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CLEAN WATER ACT SECTION 404(B)(1)
EVALUATION
Upper Hoh River Road Project
Jefferson County, Washington
Prepared for:
U.S. DEPARTMENT OF TRANSPORTATION
FEDERAL HIGHWAY ADMINISTRATION
WESTERN FEDERAL LANDS HIGHWAY DIVISION
610 East Fifth Street
Vancouver, Washington 98661
WA JEFF 91420
Prepared by:
DAVID EVANS AND ASSOCIATES, INC.
14432 SE Eastgate Way, Suite 400
Bellevue, Washington 98007
October 2017
Upper Hoh River Road Project i October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Table of Contents
1 INTRODUCTION ................................................................................................................ 1
2 PROJECT DESCRIPTION .................................................................................................. 2
2.1 Project Background .......................................................................................................... 2
2.2 Purpose and Need ............................................................................................................. 4
2.3 Project Alternatives .......................................................................................................... 5
2.3.1 No Action Alternative ................................................................................................ 5
2.3.2 Build Alternative (Proposed Project) ....................................................................... 5
2.3.2.1 Road Relocation ................................................................................................ 6
2.3.2.2 Alternative Construction Methods..................................................................... 7
2.3.2.3 Alternatives for MP 4.38 Stream Crossing ........................................................ 9
2.3.2.4 Alternatives for the Tower Creek Bridge ........................................................ 10
2.3.2.5 Alternatives for the Canyon Creek Culvert ..................................................... 10
2.4 Location and Type of Impacts to Waters of the United States....................................... 10
2.5 Factual Determinations .................................................................................................. 13
2.5.1 Physical Substrate Determinations ......................................................................... 14
2.5.2 Water Circulation, Fluctuation and Salinity Determinations ................................ 14
2.5.3 Suspended Particulate/Turbidity Determinations................................................... 14
2.5.4 Contaminant Determinations .................................................................................. 14
2.5.5 Aquatic Ecosystem and Organism Determinations ................................................ 14
2.5.6 Proposed Disposal Site Determinations ................................................................. 14
2.5.7 Determination of Cumulative Effects on the Aquatic Ecosystem............................ 15
2.5.8 Determination of Secondary Effects on the Aquatic Ecosystem ............................. 15
2.6 Mitigation ....................................................................................................................... 15
2.6.1 Canyon Creek Crossing .......................................................................................... 15
2.6.2 Spruce Creek Culvert at MP 9.8 ............................................................................. 15
2.6.3 Spruce Creek/Canyon Creek ELJs at MP 9.8 ......................................................... 15
2.6.4 Lindner Creek Side Channel Engineered Log Jams at MP 6.7 to 7.3 .................... 16
3 CONCLUSION ...................................................................................................................19
4 REFERENCES ..................................................................................................................20
List of Tables
Table 1 Wetland Summary Report ....................................................................................... 11
Table 2 Stream Summary Table ........................................................................................... 12
Table 3 Wetland and Stream Impact Table ......................................................................... 13
Upper Hoh River Road Project ii October 2017
Clean Water Act Section 404 (b) (1) Evaluation
List of Figures
Figure 1 Vicinity Map ................................................................................................................. 3
Figure 2 Proposed Aquatic Mitigation Concept – Lindner Creek Side Channel Engineered Log
Jams at MP 6.7 to 7.3 .................................................................................................. 17
LIST OF ATTACHMENTS
Attachment A Upper Hoh River Bank Failure Risk Reduction Study
Attachment B Upper Hoh River Road Bank Stabilization Habitat Preservation
Mitigation, Draft Hydraulics Report
Acronyms and Abbreviations
BMP Best Management Practice
CFR Code of Federal Regulations
Corps U.S. Corps of Engineers
CWA Clean Water Act
dbh diameter at breast height
EA Environmental Assessment
ELJ engineered log jam
ELJ/dolosse engineered log jam with dolosse ballast
FHWA Federal Highway Administration
FONSI Finding of No Significant Impact
LWD large woody debris
MP mile post
NEPA National Environmental Policy Act
OHWM ordinary high water mark
ONP Olympic National Park
ROW right-of-way
UHRR Upper How River Road
US 101 U.S. Highway 101
USFWS U.S. Fish and Wildlife Service
WDFW Washington Department of Fish and Wildlife
WDNR Washington State Department of Natural Resources
WFLHD Western Federal Lands Division
Upper Hoh River Road Project 1 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
1 INTRODUCTION
The purpose of Clean Water Act (CWA) Section 404(b)(1) (40 CFR Part 230) is to restore and
maintain the chemical, physical, and biological integrity of waters of the United States through
the control of discharges of dredged or fill material. Fundamental to the guidelines is the precept
that dredged or fill material should not be discharged into the aquatic ecosystem, unless it can be
demonstrated that such a discharge will not have an unacceptable adverse impact either
individually or in combination with known or probable impacts of other activities affecting the
ecosystems of concern. This analysis will show that the discharge of dredged or fill materials
related to the Upper Hoh River Road (UHRR) Bank Stabilization Project (project) will not have
an unacceptable adverse impact individually or in combination with known or probable impacts
of other activities affecting the ecosystems of concern.
For projects involving fill in waters of the United States, such as the proposed project, CWA
Section 404(b)(1) requires an evaluation of "practicable alternatives" that would have less impact
on the aquatic ecosystem. In compliance with Section 404(b)(1), this analysis will show that
practicable alternatives that do not involve special aquatic sites are not available or if available,
would not have less adverse impact on the aquatic ecosystem when compared to the proposed
project or would not meet the project purpose and need.
Section 230.10 of Subpart B of the 404(b)(1) guidelines establishes four conditions that must be
satisfied to make a finding that a proposed discharge complies with the guidelines. These
conditions include the following:
a) Except as provided under Section 404(b)(2), no discharge of dredged material shall be
permitted if there is a practicable alternative to the proposed discharge which would have
less adverse impact on the aquatic ecosystem, so long as the alternative does not have
other significant adverse environmental consequences;
b) No discharge of dredged or fill material shall be permitted if it violates state water quality
standards, Section 307 of the Clean Water Act, or the Endangered Species Act of 1973;
c) No discharge of dredged or fill material shall be permitted which will cause or contribute
to significant degradation of the waters of the United States; and
d) Except as provided under Section 404(b)(2), no discharge shall be permitted unless
appropriate and practicable steps have been taken which will minimize adverse impacts
of the discharge on the aquatic ecosystem.
Section 404(b)(1), Subpart A, Section 230.10(a) stipulates that no discharge will be allowed into
waters of the United States if the following is true:
• There is a practicable alternative, which would have less adverse impact on the aquatic
ecosystem so long as the alternative does not have other significant adverse
environmental consequences.
When an activity is proposed to occur in a special aquatic site (i.e., wetland fill) and it is not
water dependent, the regulations presume that (1) practicable alternatives that do not involve
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Clean Water Act Section 404 (b) (1) Evaluation
special aquatic sites are available, and that (2) these alternatives will have less adverse impact on
the aquatic ecosystem.
Adverse impacts may be offset by compensatory mitigation to bring the proposed project into
compliance with the 404(b)(1) guidelines. Impacts must be avoided to the maximum extent
practicable and remaining unavoidable impacts will then be mitigated to the extent appropriate
and practicable by taking steps to minimize impacts and compensate for the loss of aquatics
resource functions and values. Section 230.11 sets forth the factual determinations, which must
be considered in determining whether a proposed discharge satisfies the four conditions of
compliance. These determinations for the proposed project are discussed in the following
sections of this evaluation.
2 PROJECT DESCRIPTION
2.1 Project Background
The Western Federal Lands Highway Division (WFLHD) of the Federal Highway
Administration (FHWA), in partnership with Jefferson County, proposes constructing bank
stabilization and bridge and culvert improvements in six locations along the UHRR. Located in
western Jefferson County between U.S. Highway 101 (US 101) and the Hoh Rain Forest Visitor
Center, the UHRR provides access to the Olympic National Park (ONP) and private properties
along the road. The road was built in the 1930s, when ONP was established, and is the primary
western access to the park (see Figure 1).
The UHRR extends in a generally east-west direction north of, and in many places adjacent to,
the Hoh River, an approximately 56-mile-long river originating from Mount Olympus, flowing
through the Olympic Mountains and foothills, and emptying into the Pacific Ocean at the Hoh
Indian Reservation. The Hoh River valley is relatively flat and broad, with a complex channel-
migration zone supporting the braided river channel, gravel bars, side channels, and backwater
areas. The Hoh River has a wide range of seasonal flow rates, with recorded annual peak flows
more than 60,000 cubic feet per second.
The UHRR is within approximately five feet of the Hoh River in many areas, resulting in
unstable banks and slides during high water or storm events. WFLHD and Jefferson County have
constructed several emergency projects in recent years along the road, to prevent road closures
due to unstable slopes on the river side of the road. Repair projects constructed in an emergency
are potentially more expensive, environmentally damaging, and less sustainable in the long run.
The locations WFLHD chose for this project have the highest estimated risk of impending failure
compared to other locations along the UHRR.
Upper Hoh River Road Project
Data Sources: Jefferson County, Washington DNR.
\\Pdxfs1\project\F\FHAX00000226\0600INFO\GS\Maps\Public EA maps\Fig_1-1 Vicinity Map.mxd
Figure 3-1Vicinity Map
HohRiver
Site C4 UpstreamBank StabilizationMP 7.9, RM 23.6
10101
H o h R i v e r
Upper H
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R
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Upper Hoh River Rd
Upper Hoh River Rd
Maple Creek Rd
Ow
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C
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R
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10101
10101
Hoh Mainline Rd
Culvert ReplacementMP 4.38, RM 19.5
Site C4 DownstreamBank StabilizationMP 7.5 to 7.6RM 23.3
Site C5Canyon Creek CulvertMP 10.2, RM 27.1
Site C1Bank StabilizationMP 3.6 to 3.8RM 18.8 to 18.9
Site C3Tower Creek BridgeMP 7.5, RM 23.3
Site C2Bank StabilizationMP 4.0 to 4.4RM 19.1 to 19.5
Project Locations
Upper Hoh River
Upper Hoh River Road
Local Road
0 0.5 1Mile
WASHINGTONEnlarged Area
T. 27N R. 11WSec. 19, 25, 27, 28 & 30T. 27N R. 12W Sec. 24 & 25
Project Location
10101
10101
Olympic National Park
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Clean Water Act Section 404 (b) (1) Evaluation
2.2 Purpose and Need
The proposed project’s purpose is to develop and implement cost-effective, long-term bank
stabilization solutions at three locations along the UHRR in western Jefferson County,
Washington. The project will also replace three stream-crossing structures (bridges or culverts).
The UHRR at the bank stabilization and stream crossing sites is at risk of washing away in a
large flood event. Key design objectives are to protect the UHRR at certain locations between
mile post (MP) 3.6 and MP 10.2 from erosion, and to provide safe and consistent access to
residents, businesses, and ONP visitors between US 101 and the Hoh Rain Forest Visitor Center.
The UHRR serves as the only access road for the residents and businesses located along this
roadway and for visitors entering ONP from US 101 from the west. In 2014, over 82,000
vehicles entered the park using the UHRR. In August of 2015 alone, 24,000 vehicles entered the
park using the UHRR. Visitor data for recent years indicate that an annual average of 3 million
people visit the park. The UHRR leads to the Hoh Rain Forest Visitor Center, which is one of
four year-round ranger stations in ONP and the only year-round ranger station with access to the
western side of the park (NPS 2016a; 2016b).
Maintaining safe and consistent access along the UHRR has been increasingly difficult due to the
dynamic character of the adjacent Hoh River, a low-gradient river with frequenting-shifting
braided channels. Additional challenges have recently exacerbated the character of the river
corridor. For example, vegetation removal in the Hoh River drainage combined with recent
changes in weather patterns (warmer temperatures and less snow) have contributed to the
magnitude and extent of the river’s channel migration. Often, this has caused flows to be directed
against the road embankment causing significant erosion and instability. Bank erosion has
occurred on sections of riverbank not protected by riprap revetments, heavy vegetation, or
boulder lag deposits. The bank erosion is caused by mid-channel sediment deposits and woody
debris shifting across the braid plain and redirecting flood flows at unstable bank areas. Damage
to the UHRR due to flooding has resulted in road or lane closures lasting several weeks in 1996,
1998, 2003, 2004, 2006, 2007, and 2014. A continuing trend of more frequent flooding will
increase the potential for interrupted access to US 101 and ONP for local residents, business
owners/patrons, park users, and other recreationists.
The cost to repeatedly maintain safe access on the UHRR has increased substantially due to the
Hoh River’s character and its proximity to the UHRR. Over the past decade, the County and
WFLHD (through the Emergency Relief Program) have spent over $5 million on 13 projects to
maintain safe access on the 12-mile portion of the UHRR between US 101 and ONP.
Built in 1983, the Tower Creek Bridge is in need of replacement, and does not meet current
seismic and design standards. The Hoh River’s migration toward the UHRR has shortened the
Tower Creek channel length, which has caused the Tower Creek channel to incise and scour the
bridge abutments. In addition to being undersized and requiring frequent maintenance to remove
debris and sediment, the MP 4.38 and Canyon Creek culverts are barriers to fish passage at
certain flows.
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Clean Water Act Section 404 (b) (1) Evaluation
Because the purpose and need of the project are intended to stabilize the bank of the Hoh River
and make changes to the in-stream conditions of several tributaries, the project by definition is
“water dependent” as defined under Section 4049(b)(1).
2.3 Project Alternatives
The following project alternatives were previously described and evaluated in the project
Environmental Assessment (DEA 2017).
2.3.1 No Action Alternative
With the No Action Alternative, the project would not be constructed, and maintenance and
emergency repairs along the UHRR would continue similar to existing conditions, on an as-
needed basis, in response to damage from flood and storm events. This would require ongoing
monitoring along various lengths of bank and riprap revetment to prevent potential future road
closures. Maintenance at the MP 4.38 and Canyon Creek culverts and the Tower Creek Bridge
would continue. Typically, emergency repairs to the riverbank, roadway, or related structures
would need to begin immediately following incidents causing damage, irrespective of the in-
water work window that would normally constrain the timing of construction to protect fish and
fish habitat.
Similar to past emergency repair work, future work would likely require temporary closures on
the UHRR for staging vehicles, backhoes, cranes, and other equipment during riprap placement.
The amount of riprap would depend on the extent and magnitude of damage resulting from bank
erosion or riprap dislodgement. Some or all of this work could occur below the ordinary high
water mark (OHWM). To the extent Best Management Practices (BMPs) could be employed on
short notice for emergency work, they would minimize water quality impacts from the release of
silt and soils during riprap placement.
2.3.2 Build Alternative (Proposed Project)
The purpose of the Build Alternative is to develop and implement, at six locations, cost-
effective, long-term bank stabilization and stream crossing solutions to lessen the probability of
road washouts and assure safe and consistent access along the UHRR. The need for the project
stems from historic and ongoing damages to the UHRR, and its embankment, from flooding and
erosion along the Hoh River. Such conditions have caused access along the UHRR to be
unreliable for local residents, businesses, ONP visitors, and others traveling this sole route that
connects US 101 with the ONP’s Hoh Rain Forest Visitor Center. The Build Alternative would
accomplish the purpose of and need for the project while providing fish habitat benefits,
including fish passage and in-stream habitat.
The locations WFLHD chose for this project have the highest estimated risk of impending failure
compared to other locations along the UHRR, as determined by the Upper Hoh Road Bank
Failure Risk Reduction Study (study) (WFLHD 2013), included as Attachment A. This
engineering study evaluated the existing bank conditions and considered treatments options and
methods for the bank stabilization locations at Sites C1, C2, and C4 and the Tower Creek and
Canyon Creek crossings. Treatments options considered included continuing maintenance,
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Clean Water Act Section 404 (b) (1) Evaluation
relocating the road, stabilizing the existing road embankment, a minor active river channel shift,
and a major active river channel shift.
Specific methods for stabilizing the existing road embankment were evaluated and included a
complex roughened large rock toe, a complex log crib wall; riprap with roughened tock toe, large
woody debris (LWD), and riparian planting; and riprap with stream barbs. Riprap with stream
barbs and engineered log jam (ELJ) groins were considered and evaluated as specific methods to
accomplish a minor active river channel shift.
The study ranked each of these options and methods according to several criteria, including
roadway protection and preservation; cost; and impacts to bank stability, special species and
habitat, wilderness areas, river process and function, safety, and private property. The study also
discussed environmental clearance considerations for each of the options. Ranking highest for
the three bank stabilization locations (Sites C1, C2, and C4) were bank stabilization with
complex roughened large rock toe or riprap with LWD plantings and a minor active river
channel shift using large stream barbs. For Tower Creek, replacing the bridge ranked highest,
and for Canyon Creek, replacing the culvert with a new open-bottom culvert ranked highest.
The study was the starting point for further evaluation of methods, development of the Build
Alternative (Proposed Project), and the evaluation of environmental impacts in the EA. Further
evaluation by WFLHD, including relocation of the UHRR and alternative bank stabilization
measures, are described in more detail below.
2.3.2.1 Road Relocation
Relocating the UHRR north of the existing alignment was initially considered. This preliminary
alternative would have required removal of mature vegetation and critical habitat for the marbled
murrelet, resulted in impacts to undisturbed wetlands, and required excavation on very steep
slopes with geologic hazards. Retaining walls could have been required. Slopes begin at the
UHRR and generally become steeper moving north toward the 3,018-foot summit of Spruce
Mountain, approximately 2.5 miles from Sites C4 and C5. With this alternative, WFLHD would
have had to acquire large amounts of private and public property for conversion to transportation
use. In addition to more extensive road demolition and construction that would have disrupted
traffic for a considerably longer duration and extensive right-of-way acquisitions, substantial
efforts and costs also would have been required to relocate several stream crossing structures
(bridges and culverts) and restore vegetation and the river embankment sections along the
original roadway.
WFLHD documented its examination of the UHRR relocation option in Section 2.3.3 of
Attachment A. Major findings for road relocation included the following:
• The required length of the relocated UHRR would have been 3,000 to 4,000 feet; this
option would have required the relocated road cross the 260-foot high terrace slope
immediately north of the UHRR;
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Clean Water Act Section 404 (b) (1) Evaluation
• Observed slumping on the terrace slope suggested geotechnical instability, meaning that a
relocated road could have caused landslides and debris flows, potentially blocking and
damaging the UHRR;
• Road relocation would therefore have required significant efforts to stabilize the road
foundation, in order to reduce the potential for landslides and debris flows; and
• Road relocation would have allowed removal of the existing riprap revetment and
reconstruction of an area of riverbank approximately 80 to 100 feet wide by 1,800 feet
long. Bank stabilization techniques and newly planted vegetation would have been
required on the reconstructed riverbank and upland area to prevent lateral bank erosion
and migration of the channel to the north. Techniques and vegetation would have been
subject to performance monitoring, similar to the proposed project.
More recent evaluation of UHRR relocation considered two main options: (1) relocating the
UHRR to the north between MP 3.0 and MP 11.0, and (2) relocating shorter segments of the
UHRR that are closest to the road, including either the segment from MP 3.0 to MP 5.5, MP 7.0
to MP 9.0, or MP 9.0 to MP 11.0.
Relocating the UHRR for 2.5 miles, between MP 3.0 to MP 5.5, would have moved the road
away from Sites C1 and C2 and required demolition and replacement of two large bridges,
relocation of two to three large-diameter fish-passable culverts, construction of major retaining
walls on the north side of the UHRR, and clearing approximately 20 acres of right-of-way
(ROW). The first bridge would have been approximately 600 feet long and 100 feet above
ground. The second bridge would have been approximately 100 feet long. As the road length
increased and the alignment differences grew, this preliminary alternative would have increasing
risks, including steep slopes and unstable soils on the north side of the UHRR. WFLHD
estimated that the total capital cost of relocating the road, not including addressing erosion and
road washouts at Site C4, would have been ranged from $13 million to $17 million, based on
these two options.
Additional funds could have been required to stabilize the UHRR and surrounding area if
landslides were to occur. Based on the greater magnitude of environmental consequences, a
more extended construction timeline, and higher costs, relocating the UHRR was dismissed from
further consideration.
2.3.2.2 Alternative Construction Methods
Selection of the three bank stabilization sites was based on observations along the river and
UHRR and represent locations most in need of stabilization. Methods considered for stabilizing
banks, other than ELJs with dolosse, include riprap, log crib walls, and stream barbs and groins.
Riprap. Riprap is the most common and highly effective form of bank protection in the Pacific
Northwest. It consists of armoring the bank with large angular rock that deflects hydraulic forces
from treated sites, and is used for long-term erosion control. Using riprap at the three bank
stabilization sites would meet the purpose and need of the project, as it would stabilize the bank
and result in long-term increased reliability and safety along the UHRR. However, riprap can
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Clean Water Act Section 404 (b) (1) Evaluation
permanently displace and adversely affect fish habitat, result in erosion at other untreated sites,
and reduce the recruitment of LWD and sediment recruitment. Riprap not installed properly
tends to (1) create downstream scour at the transition to the natural bank, and (2) undermine the
toe of the slope downstream of the installed riprap. Existing riprap revetments along the Hoh
River may be responsible for some observable downstream scour and channel changes, although
the dynamic nature of the river’s migrating channel may also be a contributing factor. The riprap
option was dismissed from further consideration due to the risks associated with improper
installation and the long-term potential for adverse impacts related to fish habitat, LWD, and
sediment transport.
Roughened Toe. The roughened toe method is a stabilization technique that prevents erosion at
the toe of a river bank, where erosion is typically the greatest along a river. It provides rock
armoring at the toe and allows for more natural techniques such as planting on the upper bank.
Large woody debris is often incorporated into this technique to provide habitat value and further
decrease water velocities adjacent to the bank. Similar to riprap, roughened rock toe will reduce
sediment recruitment from the streambank as well as large woody debris recruitment. Roughened
toe was dismissed from further consideration due to the following:
• Stabilizing the logs and root wads would require extensive excavation of the bank and
road or filling out into the river with a substantial amount of rock, fill ballast, or ground
anchors, which would represent a larger adverse impact than ELJ/dolosse units;
• Roughened toe would not create as many interstitial spaces or changes in flow velocity
for fish to hide, compared to other techniques;
• This method would require approximately 700 cubic yards of riprap for each ELJ length.
Considering the extent of the protected areas, the amount of riprap placed on the bank
would be very large;
• Log decay, shifting, sliding, rocking, and slumping would tend to disengage the logs
from the ballast material. A surplus of ballast material must be placed to ensure the logs
are not completely dislodged. The treatment area would require 400 cubic yards of riprap
ballast to counteract the buoyancy forces of the root wads. This represents approximately
40 percent of the ELJ void space volume, resulting in a treatment very similar to riprap,
as far as fish habitat and hydraulic performance is concerned. The riprap ballast greatly
reduces the ELJ void space available for habitat and channel complexity.
• When the logs rot away or become dislodged from the roughened toe, the riprap will not
collect logs drifting downstream, unlike the ELJ/dolosse units, which will continue to
collect debris and large wood drifting downstream during flood events after the logs rot
away.
Log Crib Walls. Log crib walls are large rectangular log boxes filled with rocks and soil,
oriented parallel to the direction of streamflow. Planting spaces are formed in the wall by
stacking the wall logs in alternating fashion. This solution would meet the purpose and need of
the project—to stabilize the bank and create increased reliability and safety for residents,
businesses, and ONP visitors using the UHRR. These structures are typically used where
streambanks are experiencing mass failure or significant erosion from subsurface drainage. Bank
failure along the Hoh River is caused by river scour at the toe of slope, not by erosion from
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Clean Water Act Section 404 (b) (1) Evaluation
subsurface drainage. As vertical structures, log crib walls are susceptible to hydraulic and
gravitational forces that cause undermining and settling of soils within and behind the wall;
therefore, this may not be a sustainable option, given the dynamic and forceful attributes of the
Hoh River flow regime. Installing log crib walls along the banks of the Hoh River could result in
the toe of the structure remaining vulnerable to scour and subsequent undermining, settling, and
collapse. Therefore, log crib walls as a treatment option were also dismissed from further
consideration.
Stream Barbs and Groins. Stream barbs and groins extend from the bank into the flow of a
water body, and are typically constructed of rock, LWD, or a combination of both. They are used
for bank protection, to create lateral sand bars, to divert stream flow in a mid-channel direction,
and to change depositional patterns of sediment. The height of groins usually extend above the
high-flow water surface elevation. This tends to change the cross-section of the stream more than
barbs, by deepening and narrowing the channel. Each type has the potential to provide pool
habitat for fish. Although trees or LWD can be added into barbs or groins to increase habitat
value, they increase the risk of voids in the rock fill, result in poor foundation conditions, and
may cause buoyancy that affects the stability of the structure (NRCS 2013). Groins constructed
of LWD typically allow more water to flow through them, which tends to create less scouring of
the adjoining streambed than a rock groin.
Although both groins and barbs would meet the project’s purpose and need of increasing bank
stabilization and related reliability and safety of the UHRR, they can cause more significant
changes to downstream and upstream hydraulic and erosion patterns. Stream barbs and groins
were dismissed from further consideration because any additional downstream or upstream
erosion they might cause could exacerbate current bank erosion conditions.
Based on the hydraulic analysis and cost estimates, installation of wood buffers with dolosse
ballast (ELJ/dolosse) was recommended for the bank stabilization sites. In addition to being the
least expensive for effectively controlling bank erosion, this approach can accommodate a
greater range of active flow channel migration and flow impingement angles. Minimal channel
bed excavation will occur, and the ELJ/dolosse units will be placed directly into flowing water,
which will be the least disruptive to the environment. This approach does not appear to (1)
noticeably increase flooding or bank erosion on private property adjacent to the project site, or
(2) negatively affect stream processes. The ELJ/dolosse approach also provides the greatest
reduction in flow velocity and improvement in habitat complexity, compared to other
alternatives. This approach is also most adaptable to changing field conditions. See Attachment
B, Upper Hoh River Road Bank Stabilization Habitat Preservation Mitigation - Draft Hydraulics
Report, for more detail.
2.3.2.3 Alternatives for MP 4.38 Stream Crossing
The water conveyance/stream crossing improvement at MP 4.38 was initially envisioned as a
bridge to minimize the level of disturbance to the UHRR at this site. During the design process,
the Hoh River migrated closer to the existing roadway. Consequently, the anticipated detour
route planned for construction was no longer feasible because there would be limited area for the
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Clean Water Act Section 404 (b) (1) Evaluation
contiguous footings and piers needed for construction. While the bridge option would have met
the purpose and need for the project, the design layout at this site was no longer feasible.
WFLHD, therefore, decided to only carry forward the culvert option for this site.
2.3.2.4 Alternatives for the Tower Creek Bridge
Steel girders were considered as an option at the span length required for Tower Creek.
Replacing Tower Creek Bridge (with steel girders or girders made from another material) meets
the purpose and need for the project, in that a new bridge supports the long-term reliability of the
UHRR. Concerns were expressed that steel girders could require a cast-in-place concrete deck
and that the girders would be susceptible to corrosion and create new maintenance issues.
Therefore, steel girders were dismissed from further consideration for the Tower Creek Bridge.
2.3.2.5 Alternatives for the Canyon Creek Culvert
A three-span bridge arrangement was initially evaluated for Canyon Creek. A three-span
structure would use shorter and more cost-effective bridge girders, yet the cost saving from the
superstructure could be offset by the cost of the additional foundation and piers and the required
in-water work for the intermediate piers. Although the multiple span arrangements would help
minimize the structural depth and reduce the cost of the bridge superstructure, the bridge piers
would have potential problems due to added requirements for dewatering, cofferdams, and
equipment access. The additional piers and shorter spans would combine to catch and retain
debris, and provide another mechanism for scour to form under the bridge. The three-span
arrangement was therefore dismissed from further consideration, even though it would have met
the purpose and need for the project as part of a new bridge, which would have increased the
long-term safety and reliability of the UHRR.
2.4 Location and Type of Impacts to Waters of the United States
Characteristics and classification of wetlands and streams in the project area are described in
detail in the original Wetland and Streams Delineation Report for the project as well as the
Addendum to that report (prepared in 2017). Tables 1 and 2 below summarizes waters of the
United States delineated in the study area.
A total of 22 wetlands and 19 streams were mapped within the study area. The wetlands are all
either Category II or III wetlands, and their hydrogeomorphic class is mostly slope. Most of the
wetlands are located on the north side of the Upper Hoh River Road, opposite of the proposed
bank stabilization work. Most of the wetlands are dominated by either shrub or forest vegetation.
Most of the streams are small, high gradient side wall tributaries that drain directly to the Hoh
River. The larger, fish bearing streams in the study area include the Hoh River, Willoughby
Creek, Tower Creek, Canyon Creek, and the unnamed tributary at MP 4.38.
All of the wetlands and streams are assumed to be under the jurisdiction of the U.S. Corps of
Engineers (Corps) based on direct surface water connections to the Hoh River or location in the
100-year floodplain.
Upper Hoh River Road Project 11 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Table 1 Wetland Summary Report
Wetland ID Ecology1
Category
NWI
Classifi-
cation
HGM
Wetland
Class
Total
Wetland
Functions
Score
Water
Quality
Functions
Score
Hydrology
Functions
Score
Wildlife
Habitat
Functions
Score
Jefferson
County
Wetland
Buffer2
Site C1
W4 III PFO Slope 18 6 4 8 150
W5 III PSS Slope 17 6 4 7 80
W6/WC1-A III PFO Slope 18 6 4 8 150
WC1-B III PFO Slope 17 4 5 8 150
WC1-C III PFO Slope 17 4 5 8 150
WC1-D III PFO Slope 17 4 5 8 150
WC1-E III PFO Slope 17 4 5 8 150
W3/WC1-F III PFO Slope 18 6 4 8 150
WC1-G III PFO Slope 17 4 5 8 150
Site C2
W1 III PEM Slope 17 6 4 7 80
W2/WC1-H III PFO Slope 18 6 4 8 150
W12 III PFO Slope 18 6 4 8 150
Site C3
WC3-A III PFO Depressional 16 7 4 5 80
WC3-B III PFO Depressional 16 7 4 5 80
Site C4
WC4-A III PFO Slope 17 4 5 8 150
WC4-B III PFO Slope 17 4 5 8 150
WC4-C III PFO Slope 17 4 5 8 150
Site M1
W7 II PFO Depressional 20 7 5 8 300
W8 II PFO Depressional 20 7 5 8 300
Site M2
W9 III PSS Depressional 20 7 7 6 150
W10 III PSS Slope 20 7 5 8 150
W11 III PSS Slope 20 7 5 8 150
1 Washington State Department of Ecology (2014)
2 Wetland buffer widths in the Jefferson County
Upper Hoh River Road Project 12 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Table 2 Stream Summary Table
Stream Watershed DNR Classification1
Local Jurisdiction
Classification2
Field
Estimated
Classification
Stream
Width (feet)
Buffer Width
(feet)D
Site C1
Willoughby
Creek
WRIA 20 Type F = Fish Type F = Fish F = Fish 15 -20 150
S9 WRIA 20 Not Mapped Not Mapped Ns 2 – 2.5 50
SC1-A WRIA 20 Not Mapped Not Mapped Ns 1 – 1.5 50
SC1-B WRIA 20 Not Mapped Not Mapped Ns 1 – 1.5 50
Hoh River (C1) WRIA 20 Type S Type F = Fish F = Fish 570 - 830 150
Site C2
S8/SC1-C WRIA 20 Not Mapped Not Mapped Ns 1 – 1.5 50
S12 WRIA 20 Not Mapped F = Fish F = Fish 3 - 5 150
S13 WRIA 20 Not Mapped Not Mapped Ns 1 - 2 50
S14 WRIA 20 Not Mapped Not Mapped Ns 2 - 3 75
S15 WRIA 20 Not Mapped Not Mapped Ns 1 - 2 75
S16 WRIA 20 Not Mapped Not Mapped Ns 1 – 2.5 75
S17/SC1-D WRIA 20 Not Mapped Not Mapped Ns 1 - 3 75
S18 WRIA 20 Not Mapped Not Mapped Np 1 - 2 50
Hoh River (C2) WRIA 20 Type S Type F = Fish F = Fish 560 - 590 150
Site C3
Tower Creek WRIA 20 Type F = Fish Type F = Fish F = Fish 30 - 50 150
Hoh River (C3) WRIA 20 Type S Type F = Fish F = Fish 630 150
Site C4
SC4-A WRIA 20 Not Mapped Not Mapped Ns 1 – 1.5 50
SC4-B WRIA 20 Not Mapped Not Mapped Ns 3 – 5 50
Hoh River (C4) WRIA 20 Type S Type F = Fish F = Fish 800 - 1000 150
Site C5
Canyon Creek WRIA 20 Type F = Fish Type F = Fish F = Fish 30 - 50 150
Hoh River (C5) WRIA 20 Type S Type F = Fish F = Fish 720 - 780 150
Site M1
Hoh River (M1) WRIA 20 Type S Type F = Fish F = Fish 400 - 750 150
Site M2
S10 WRIA 20 Not Mapped Not Mapped Ns 2 - 3 50
S11 WRIA 20 Not Mapped Not Mapped Ns 2 - 3 50
Hoh River (M2) WRIA 20 Type S Type F = Fish F = Fish 800 - 1000 150
Upper Hoh River Road Project 13 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Table 3 describes proposed impacts to waters of the United States. This information is also listed
in the project JARPA. Most of the proposed fill in waters of the United States will occur in the
Hoh River, and will consist of the ELJs and associated materials. The proposed project will have
permanent impacts to approximately 1.5 acres of streams, including the Hoh River, and
approximately 2.8 acres of temporary impact to streams. Most of these impacts are due to
placement of the ELJs in the Hoh River. Approximately 0.05 acre of wetlands will be
temporarily affected by the proposed project, and approximately 0.03 acre of wetlands will be
permanently affected. All of the permanently affected wetlands are previously disturbed and in
close proximity to UHHR.
Table 3 Wetland and Stream Impact Table
Waterbody Impact Type Area of Impact (square feet)
Streams
Hoh River Permanent 58,824
Hoh River Temporary 120,716
Unnamed Tributary at MP 4.38 Permanent 534
Unnamed Tributary at MP 4.38 Temporary 1118
Tower Creek Permanent 5,908
Tower Creek Temporary --
Canyon Creek Permanent 2130
Canyon Creek Temporary --
Total Permanent Impact 65,496
Total Temporary Impact 121,834
Wetlands
Wetland 1 Permanent 765
Wetland 5 Permanent 458
Wetland WC3-A Permanent 339
Wetland WC3-A Temporary 265
Wetland WC3-B Temporary 2
Wetland WC4-A Temporary 18
Ditch DC3-A Permanent 432
Ditch DC3-A Temporary 60
Ditch DC4-A Permanent 55
Ditch DC4-B Permanent 630
Ditch DC4-B Temporary 466
Total Permanent Impact 2679
Total Temporary Impact 811
2.5 Factual Determinations
Section 404(b)(1), Subpart A, Section 230.11, of the CWA requires that certain factual
determinations be made in order to demonstrate that the project will not cause or contribute to
significant degradation of water of the United States. Each of these determinations are addressed
Upper Hoh River Road Project 14 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
below. In general, information is summarized, and the reader is referred to other existing
documents for more information.
2.5.1 Physical Substrate Determinations
The proposed project will not significantly change substrate in the Hoh River. ELJs will be
limited to addition of dolosse and LWD to mimic behavior of natural logjams in the river. See
section 4.4 (Hydrology and Hydraulics) in the Draft and Final Environmental Assessment (EA)
for more information.
2.5.2 Water Circulation, Fluctuation and Salinity Determinations
The proposed bank stabilization projects are designed to produce a buffering effect along the
existing riverbank and reduce water velocities in order to reduce bank erosion and scour. See
Section 4.5, Hydrology and Hydraulics, in the Final EA, as well as Appendix D of the FONSI,
Hydraulic Report, and Attachment B to this report, Upper Hoh River Road Bank Stabilization
Habitat Preservation Mitigation, Draft Hydraulics Report.
2.5.3 Suspended Particulate/Turbidity Determinations
The proposed project will create temporary increases in suspended sediment during installation
of the ELJ/dolosse units. However, these increases will be reduced through use of BMPs and
adherence to the project Water Quality Monitoring Plan, which was an enclosure with the
JARPA application to the Corps. No temporary increase in suspended sediment is anticipated for
any of the tributary projects since all of those will be constructed with complete work area
isolation. No long term changes in suspended sediment or turbidity are anticipated.
2.5.4 Contaminant Determinations
No contaminants will be introduced to the aquatic ecosystem due to the project. All materials
will be either native materials (e.g., logs, slash, nearby bank material, etc.) or pre-fabricated
concrete dolosse.
2.5.5 Aquatic Ecosystem and Organism Determinations
The proposed project will have a variety of effects to the aquatic ecosystem, including temporary
and permanent impacts to the Hoh River, Tower Creek, Canyon Creek, and the unnamed
tributary at MP 4.38. Overall, the project will permanently affect 0.04 acre of wetlands and wet
ditches, and 1.5 acres of the Hoh River due to installation of the ELJs. These impacts to the
aquatic ecosystem and associated aquatic organisms are fully described in the project Biological
Assessment, Biological Opinion (prepared by the U.S. Fish and Wildlife Service (USFWS),
Draft and Final EA, and associated technical reports, including the Wetland Delineation Report
and Addendum.
2.5.6 Proposed Disposal Site Determinations
Location of the proposed in-water work is described in the JARPA application and other project
documents.
Upper Hoh River Road Project 15 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
2.5.7 Determination of Cumulative Effects on the Aquatic Ecosystem
Cumulative effects to the aquatic ecosystem are described in Sections 4.4 (Hydrology and
Hydraulics) and 4.6 (Fish and Wildlife) of the Draft and Final EA.
2.5.8 Determination of Secondary Effects on the Aquatic Ecosystem
Secondary (indirect) effects to the aquatic ecosystem are described in Sections 4.4 (Hydrology
and Hydraulics) and 4.6 (Fish and Wildlife) of the Draft and Final EA.
2.6 Mitigation
During the environmental permitting phase of the project, resource agencies voiced concerns that
placing the ELJ/dolosse units into the river channel would cause negative effect to fish and
aquatic habitat. As a result of these concerns and of the National Environmental Policy Act
(NEPA) process, including agency consultation and public comment, WFLHD concluded that
the proposed project would require compensatory mitigation to offset unavoidable impacts to the
aquatic ecosystem.
Four mitigation options were discussed with involved agencies, including mitigation options at
Canyon Creek crossing, Spruce Creek Bridge, Spruce Creek/Canyon Creek at MP 9.8, and
Lindner Creek Side Channel at MP 6.7. Each mitigation option considered is described below.
Detailed information, including construction sequencing the potential effects, are provided below
about the mitigation option that was ultimately chosen, at Lindner Creek Side Channel (MP 6.7).
2.6.1 Canyon Creek Crossing
WFLHD considered proposing the replacement of Canyon Creek culvert with a bridge as
mitigation for the bank stabilization project. Replacing the culvert at Canyon Creek with a bridge
was evaluated in the Draft EA, and it was noted (at the time the Draft EA was issued) that the
Canyon Creek component of the project was under consideration as mitigation for the bank
stabilization components of the project. Since the Draft EA was issued, WFLHD in coordination
with the Washington Department of Fish and Wildlife (WDFW), the Hoh Tribe, and the Corps
determined that the Canyon Creek crossing work would not qualify as mitigation.
2.6.2 Spruce Creek Culvert at MP 9.8
In 2009, the eastbound lane of the UHRR was undermined when a debris flow damaged the
Spruce Creek culvert beyond repair. Jefferson County installed temporary riprap to rebuild the
eastbound lane. In 2012, the damaged culvert was replaced with a 24-foot concrete bridge. The
project was self-mitigating because it replaced an existing partial fish passage barrier. Since
2012, much of the material comprising the bank has washed away, and fish passage no longer
exists at Spruce Creek. WFLHD considered rebuilding the bank at this location and restoring fish
passage to Spruce Creek, as mitigation for the bank stabilization work.
2.6.3 Spruce Creek/Canyon Creek ELJs at MP 9.8
Mitigation at Spruce Creek/Canyon Creek at MP 9.8 was considered and would have involved
installing four large ELJs in the Hoh River adjacent to and upstream of the confluence of Spruce
Creek to MP 9.8, in an area managed by the Nature Conservancy. The ELJs would be placed in
Upper Hoh River Road Project 16 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
front of the existing riprap that Jefferson County installed as part of emergency repair. They
would be similar in design to the ELJ/dolosse units previously described for the proposed
project, and would provide the following benefits:
• Preserve the existing riparian habitat at this location, where the river is actively scouring
upstream of the riprap installation;
• Improve channel roughness and complexity, which has decreased due to nearby riprap;
• Provide additional rearing habitat and cover for salmonids, through decreasing near-shore
flow velocity at this important location near the mouth of Spruce Creek and the mouth of
Canyon Creek (Canyon Creek flows through a large side channel and joins the mainstem
upstream of this location); and
• Provide more favorable habitat for juvenile salmonids through (1) the use of the ELJs
itself as cover, and (2) creation of additional channel complexity including scour pools.
(Post-construction monitoring studies of similar ELJ structures installed by WSDOT in
the lower Hoh River and elsewhere have demonstrated this effect.)
During the NEPA agency consultation and public comment period, the agencies decided this
would not constitute adequate mitigation because it did not sufficiently offset potential project
impacts to aquatic habitat in the mainstem Hoh River. In addition, anchoring the ELJs with piles
or dolosse would represent an impact, and would require mitigation in itself. For these two
reasons, the Spruce Creek/Canyon Creek ELJs at MP 9.8 as mitigation was not carried forward.
2.6.4 Lindner Creek Side Channel Engineered Log Jams at MP 6.7 to 7.3
The extent and permanency of high-value side channel aquatic habitat is limited in the Hoh River
system. The side channel habitat that does exist is quickly disappearing due to the river’s
frequent channel migration and avulsions. During the permitting process, WDFW identified
high-value side channel aquatic habitat immediately downstream of MP 7.8 (see Figure 2).
Lindner Creek and several other creeks flow into a major side channel of the Hoh River at this
location, which formed approximately 15 years ago when the main channel of the river migrated
to the south side of the channel migration zone. Mitigation will involve placing ELJs at the edge
of the floodplain, in order to provide floodplain roughness and improve resilience of the side
channel aquatic habitat by reducing the channel migration and avulsion risk and encouraging the
development of natural floodplain roughness. The aquatic side channel habitat is best preserved
where the floodplain vegetation is oldest and has become large and dense enough for resisting
channel migration and avulsion.
Increasing the floodplain roughness along the floodplain boundary is recommended for
protecting the side channel aquatic habitat and encouraging future tree growth. Side channel
aquatic habitat is created when the channel migrated or avulses, leaving water-filled pools that
are isolated from the main river flow. They persist when alder and conifer trees are able to
colonize in sufficient numbers and grow large enough to create a high floodplain roughness that
inhibits channel migration and avulsion. Most of the site’s floodplain area has only sparse small
willows and alder trees. The trees will not provide enough floodplain roughness for resisting
expected channel migration and avulsion.
Service Layer Credits:
Upper Hoh River Road Project
Data Sources: USDA 2015 NAIP, Jefferson County
\\Pdxfs1\project\F\FHAX00000242\0600INFO\GS\Maps\Biological Assessment Maps\Fig_1_M1 Lindner Ck Mitigation ELJs.mxd
U p p e r H o h R d
Hoh
River
H o h R i v e r
¶
U p p e r H o h R d
Existing Road
New Road
EngineeredLog Jam (ELJ)
Site C3Tower Creek BridgeMP 7.5, RM 23.3
Site C4 DownstreamBank StabilizationMP 7.5 to 7.6RM 23.3
0 250 500Feet
Figure 1Proposed Aquatic Mitigation Concept -Lindner Creek Side ChannelEngineered Log Jams, MP 6.7 to 7.3
Project Site
Upper Hoh Road
New Road
Existing Road
Engineered Log Jam (ELJ)³
Upper Hoh River Road Project 18 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
If left to grow, the trees will likely provide adequate natural resistance. LWD lining the active
channel edge will deflect high velocity flow away from overbank areas, reducing the overbank
flow velocity, increasing fine-grained sediment deposition, and allowing alder and conifer trees
to grow.
Twenty-four (24) ELJs will be installed at the head of flood scour channels near the active
channel edge, which will simulate the LWD that currently lines the bank in this area. They will
be installed between approximately MP 6.7 and MP 7.3 of the UHRR, west of Site C3 (Tower
Creek) and in an area and owned or managed by the U.S. Forest Service, the Nature
Conservancy, and the Washington Department of Natural Resources (WDNR) (see Figure 2, and
Figure 2 in Attachment B).
Tributaries to the Hoh River, such as Lindner Creek, and the high-water channels that cross the
wooded floodplain between the Hoh River upstream and the large side channel near MP 6.7
provide important rearing and high-water refuge habitat for fish species such as steelhead,
Chinook salmon, coho, and bull trout. Many of the high-water channels have emerged during
relatively minor flood events (e.g., less than 10-year flood flow) since the 1990s, due to the
increasingly erratic nature of the Hoh River’s migration across the river meander belt. Figure 3
in Attachment B shows the finger- and overflow-channels that emerge on the floodplain
‘peninsula’ during a two-year flood event.
Lindner Creek, the large main channel, and the high-water channels on the ‘peninsula’ comprise
a side channel complex. Long-term preservation of this side channel complex would result in the
following benefits to aquatic and forest resources, which are important to stakeholder resource
managers such as WDFW and the Hoh Tribe:
• Preservation and maintenance of vital rearing and high-water refuge habitat for steelhead,
Chinook salmon, coho, and bull trout;
• Preservation of nearby priority steelhead spawning areas, which could potentially
undergo modification during the next channel migration event;
• Protection of the remaining mature forest stand south of the UHRR;
• Encouragement of riparian forest development in the area surrounding the side channel
complex by preventing a future channel migration (this area provides important forage
and cover for Roosevelt elk, particularly in the spring); and
• Preservation of the configuration of small overflow channels in the ‘peninsula’ area that
currently exist as small, finger- and overflow-channels, rather than having them develop
into larger channels, or join the main channel, if a river migration occurs.
In addition to the side channel benefits listed above, this mitigation project will encourage long-
term preservation of rearing and spawning habitat on the mainstem Hoh River by increasing
channel stability.
The 24 ELJs will be installed in an arc, extending approximately 0.8 mile south and west from
MP 7.3 of the UHRR, crossing the lower section of the side channel complex (see Figure 2, and
Upper Hoh River Road Project 19 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Figure 2 in Attachment B). Each ELJ will consist of four log bundles and five root wads. The
log bundles are made of three logs, 20 to 22 feet long, 18 to 37 inches in diameter, with total log
volume 110 to 150 cubic feet, and without attached root wads. Each log bundle is wrapped with
a steel chain. Sheet F.8 of Appendix E, Design Plan Set (70%) and Attachment B have further
detail of the dolosse/log bundle design. Between the ELJs, the bank would be planted with
cottonwood, bank willow, and emergent willow. In addition, the bank would be stabilized with a
mixture of gravel and cobble.
Installation of the ELJs will require limited clearing and temporary improvements to an existing
un-graded side road off the UHRR. This unimproved road, which is currently used for drift boat
access to the river, will be improved and temporarily extended beyond its existing terminus for
construction access. The extended portion will be replanted with dense native shrubs and trees
when ELJ installation is complete. Up to one acre of clearing will be required for the temporary
20-foot-wide access road, located approximately 200 feet from the active river channel edge.
Vegetation clearing for the newly extended access road will be limited to young alders and
willows averaging less than 10 inches diameter of breast height (dbh).
Hydraulic modeling of the Lindner Creek Side Channel mitigation project was conducted
(Attachment B) and shows that for the proposed 2-year flood, flow will be maintained to the
side channel aquatic habitat. See Figures 3 and 4 in Attachment B, which show the flows and
depths, respectively, for the 2-year flood event with this mitigation approach.
For the 100-year flood, modeling showed that flow velocity and flow depth will decrease in the
sparsely vegetated floodplain area (Figures 5, 6, 7, and 8 in Attachment B), which should
encourage natural vegetation growth. Figures 11 and 12 in Attachment B show that the
presence of the ELJs with the 100-year flood scenario will result in a decrease in flow and depth
across the floodplain by dissipating the river’s energy across the floodplain, and lessening the
potential for main channels to form. Photos 1 through 12 in Attachment B show examples of
pools that form when channels avulse and the differences in vegetation growth and ground
surface over time, after avulsion.
The model also showed that the flow depths and velocities in the active channel and along the
floodplain limit for the model 100-year proposed conditions will not be significantly different
than existing conditions. The ELJs are intended to inhibit bank erosion and channel avulsion
along the wooded floodplain. Flooding or bank erosion impacts to private property adjacent to
the project site above current levels was not shown in the modeling to noticeably increase due to
the ELJ placement. Impacts on the river and stream processes are discussed in more detail in
Attachment B.
Attachment B includes Channel Habitat Preservation (Sheets 1-4) and Channel Plug
Details, which display and explain details about the placement, configuration, and construction
of the ELJs and the temporary construction access road.
Upper Hoh River Road Project 20 October 2017
Clean Water Act Section 404 (b) (1) Evaluation
3 CONCLUSION
Based on the previous analysis, combined with other relevant project documents, including the
NEPA EA, Biological Opinion, and extensive agency coordination, the WFLHD believes that
there is no practicable alternative to the proposed work, which would have less adverse impact
on the aquatic ecosystem, while still meeting the project’s purpose and need. Other evaluated
options (i.e., riprap) would cost less to implement, but would have greater environmental
consequences. The proposed project will involve extensive BMPs and avoidance measures to
minimize potential adverse impacts to waters of the United States. These measures are described
in the Water Quality Monitoring Plan, Section 9 of the FONSI (Mitigation and Environmental
Commitments), the Biological Opinion from the USFWS, and other project documents.
Compensatory mitigation is also proposed that will provide long term habitat improvement for
aquatic habitat in the mainstem Hoh River.
4 REFERENCES
David Evans and Associates, Inc. (DEA). 2017. Final Environmental Assessment, Upper Hoh
River Road Project, Jefferson County, Washington. July, 2107.
Natural Resources Conservation Service (NRCS). 2013. Kansas Engineering Technical Note No.
KS-1 (Revision 1). ENG – Design of Stream Barbs. January 23, 2013.
National Park Service (NPS). 2016a. Park Entrance Traffic Counts. https://irma.nps.gov/Stats/
SSRSReports/Park%20Specific%20Reports/Traffic%20Counts?Park=OLYM. Accessed
March 9, 2016.
———. 2016b. National Park Service Visitor Use Statistics. https://irma.nps.gov/Stats/
Reports/Park/OLYM. Accessed January 20, 2016.
Western Federal Lands Highway Division (WFLHD). 2013. Federal Highway Administration,
Western Federal Lands Highway Division, Upper Hoh River Road Bank Failure Risk
Reduction Study. September 12, 2013.
Upper Hoh River Road Project October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Attachment A
Upper Hoh River Bank Failure Risk Reduction Study
(This page left blank intentionally.)
C1 - COUNTY MILEPOST 3.7 - 4.0
BANK STABILIZATION
Upper Hoh Road - Bank Failure Risk Reduction Study
p 1
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
SITE C1 – COUNTY MILEPOST 3.7 - 4.0 BANK STABILIZATION
Site Conditions
The site parallels the outside bank of a river bend (Fig. C1-1). Approximately 3,900 lineal feet of
riprap revetment along the apex of the river bend appears to be generally effectively controlling
road embankment erosion. The 2 to 4 feet diameter riprap comprising the revetment is
generally properly graded and placed. Revetments are in three segments. Upstream, middle,
and downstream segments are approximately 1,350, 400, and 750 feet long, respectively.
Upstream segment is also the downstream revetment segment for site C2. The remaining
1,400 feet of riprap revetment is included with site C2. Upstream segment is densely planted
with willow and alder and appears stable (Photo C1c-2). Currently, the upstream segment is
behind a point bar and does not experience impinging flow. Down-valley translation of an
upstream meander channel could expose the segment to impinging stream flows. Middle
segment is densely planted with willow and appears stable (Photo C1b-6). Approximately 550
feet of the downstream segment is densely planted with willow and alder and appears stable
(Photo C1a-2). The remaining 200 feet of the downstream segment appears less stable.
Distance of stream bank between the upstream and middle revetment segments is
approximately 500 feet. Distance of stream bank between the middle and downstream
revetment segments is approximately 260 feet.
Toe erosion and undermining of the stream bank is occurring;
Downstream of the downstream revetment segment (C1a – 100 feet).
Between the downstream and middle revetment segments (C1b – 260 feet eroding bank
and 200 feet high-risk revetment).
Between the middle and upstream revetment segments (C1c – 500 feet).
-C1a
The stream bank toe is approximately 20 feet away and 12 feet below the road pavement edge.
Mid-channel sediment deposits deflect stream flow towards the stream bank, aggravating the
bank erosion (Photo C1a-1, 5 and 6). A large woody debris jam approximately 20 feet from the
stream bank deflects stream flow towards the bank, creating a particularly vulnerable spot 15
feet long (Photo C1a-2 to 5).
-C1b
The stream bank toe is approximately 10 to 15 feet away and 16 feet below the road pavement
edge (Photo C1b-2 to 5). A point bar opposite the site directs stream flow towards the stream
bank, aggravating the bank erosion. A large woody debris jam, approximately 15 to 20 feet
from the stream bank deflects stream flow towards the bank, creating a particularly vulnerable
spot 100 feet long (Photo C1b-3 to 5).
Immediately downstream of the eroding stream bank is approximately 200 feet of the
downstream revetment segment that is nearly devoid of alder and willows and has a 1.5(h):1(v)
and steeper finished surface slope appears less stable (Fig. C1-1, Site C1b, Photo C1b-1).
Riprap has been dislodged from toe and mid slope areas. The segment is at the maximum
point of stream bank curvature and likely experiences high shear stress when floods occur.
Continued riprap loss could result in dismantling of the revetment and damage to the road.
Based on current channel alignment and expected limited channel alignment shifts and
Upper Hoh Road - Bank Failure Risk Reduction Study
p 2
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
assuming revetment maintenance is completed; the risk of a catastrophic road embankment
failure is low. Without revetment maintenance, the risk becomes moderately high.
-C1c
The stream bank toe is approximately 15 to 20 feet away and 18 feet below the road pavement
edge. A point bar opposite the site directs stream flow towards the stream bank, aggravating
the bank erosion (Photo C1c-1 and 3).
At all locations cobbles and small boulders naturally armoring the toe and large trees growing in
the stream bank inhibits the bank erosion. An erosion resistant poorly consolidated alluvium
terrace deposit has limited river bend migration to the north and south. The terrace deposit
represents the historical channel migration zone (HCMZ) right and left (looking downstream)
boundaries (Geomorphic Assessment of the Hoh River in Washington State, Bureau of
Reclamation, July 2004). Width of the HCMZ is approximately 500 feet. The road embankment
coincides with the HCMZ right boundary and valley wall. Based on historical satellite imagery,
the active channel has not changed significantly in width and location since 1994 (Fig. C1-2).
Continued stream bank erosion could undermine the road. Based on current channel alignment
and expected limited channel alignment shifts, the risk of a catastrophic road embankment
failure is moderate. Water depth at typically normal annual low flow conditions is estimated to
be 4 to 6 feet.
Considered Options
Continuing maintenance, relocating the road, installing additional bank stabilization, minor active
river channel shift, and major active river channel shift were considered. Table C1-1 presents
an evaluation and ranking of the options against design selection criteria.
Riprap is expected to be lost during extreme flooding, requiring replenishment for maintaining
the riprap installation’s effectiveness. Total Capital and Annualized Total Capital Costs provided
in Table C1-1 assume 20 percent of the riprap in an installation is replaced every 50 years.
Douglas fir and hemlock are the most commonly available logs in the area. Douglas-fir logs can
remain durable in wetting-drying conditions for 25 to 60 years (Tech. Supp. 14J, Use of Large
Woody Material for Habitat and Bank Protection, Part 654, National Engineering Handbook,
USDA, Natural Resources Conservation Service). Hemlock is the least durable of the conifers.
Because the tree quality and species to be used in the structures is not known, Total Capital
and Annualized Total Capital Costs provided in Table C1-1 assume wood used in the
alternatives is replaced every 30 years.
Continue Maintenance
Continued maintenance involves monitoring approximately 860 feet of stream bank (C1a, C1b,
and C1c) and 200 feet of the downstream revetment segment (C1b) for excessive bank erosion
and riprap loss. Stream bank toe erosion upstream and downstream of the existing riprap
revetments could progress to the point that undermining of the road is imminent. Continued
maintenance is placing riprap in an emergency action or after flooding as needed for preventing
a road closure. Placing riprap as an emergency action may be hazardous or difficult. The
emergency-placed riprap may not be effective in controlling the erosion.
A Total Expected Cost analysis (HEC-17, FHWA, April 1981) was used for estimating total
expected cost repairing flood-induced road damage over a 50-year service-life. Based on
observed riprap revetment condition, proximity of channel to roadway, and amount of natural
Upper Hoh Road - Bank Failure Risk Reduction Study
p 3
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
bank armoring, the analysis assumes damage requiring repair of the existing revetments or
addition of new riprap revetment placed as an emergency action for stabilizing an eroding river
bank occurs for flood events equal to and larger than the 25-year flood event. Based on review
of historical satellite imagery, length of bank typically exposed to impinging flood flow is
estimated to be approximately 300 feet. Based on vegetation distribution and age and
estimated riprap placement sequencing, the length of past revetment installations ranged from
200 to 500 feet. Assuming 300 feet total for each flood damage event and a cost of $1,000 per
foot, the total expected annual cost is $21,000 (Table C1-2).
Relocate Road
Shifting the road at least 100 to 200 feet away from the active river channel edge provides a
riparian buffer wide enough for containing a reconstructed stream bank area, eliminating the
need for continuous revetment bank stabilization. The 260 feet high terrace slope is
immediately adjacent to the existing roadway. A shift would mean an alignment that crosses the
terrace slope. Slumping observed on the terrace slope suggests the terrace slope is not
geotechnically stable. A new road alignment located across the terrace slope would experience
landslides and debris flows that could potentially bury the road with debris. The road alignment
may require significant foundation stabilization for mitigating landslides. Length of reroute is
estimated to be 3,000 to 4,000 feet for connecting the new road to lower risk existing road
segments.
Existing riprap revetment is removed and approximately 80 to 100 feet wide by 1,800 feet long
area of the stream bank is reconstructed. The erodible newly reconstructed stream bank would
allow lateral bank erosion and migration to the north. Streambarbs constructed from the
existing revetment riprap, Engineered-log-jams (ELJ’s), and planted vegetation control the bank
erosion and lateral migration and preserve a riparian buffer between the active river channel
and the new road embankment. The alternative requires monitoring and repair of the
streambarbs and ELJ’s to remain effective in controlling the bank erosion and lateral migration.
Estimated construction cost for the new road, existing road removal, 10 streambarbs, 5 ELJ’s,
and stream bank reconstruction is summarized in Table C1-3. Stabilizing landslides may
require significantly more money. Road construction is expected to occur outside the active
flow channel. Revetment removal, streambarb, ELJs, and stream bank construction is expected
to occur within the active flow channel. Turbidity released is expected to be limited in extent
and duration. Access for construction is assumed from the existing road. Constructing the new
road alignment first and then switching the Upper Hoh Road traffic over before removing the
existing road reduces traffic impacts to one-lane closures and short-term delays.
Stabilize Existing Road Embankment
Approximately 860 feet of stream bank (C1a, C1b, and C1c) and 200 feet of the downstream
revetment segment (C1b) are proposed for stabilization.
Options considered;
Complex roughened large rock toe.
Complex log crib wall.
Riprap with roughened rock toe, large woody debris (LWD), and riparian plantings.
Riprap with streambarbs.
Based on field evidence, the sites will experience high shear stress, 10 to 14 feet deep flood
flows, and abundant floating debris. It is critical that the stabilization methods be properly
Upper Hoh Road - Bank Failure Risk Reduction Study
p 4
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
designed and anchored for maintaining effectiveness and surviving the expected flood
conditions.
Construction for all the alternatives is expected to occur entirely within the active flow channel
and requires excavating into the streambed and stream bank. Stream work would be
accomplished in flowing water. Assuming the work is completed during low flow periods,
turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a temporary access route built of riprap and logs. The access route would be
removed after construction is completed. Upper Hoh Road traffic impacts are expected to be
limited to one-lane closures and short-term delays.
-Complex roughened large rock toe (Appendix A, Sheet 4).
The approach involves placing a rock toe between the expected scour depth and ordinary high
water level, total height approximately 10 to 12 feet and 5 feet thick. Log bundles spaced 6 to
10 feet are placed at the bottom of the rock toe. Soil placed above the rock toe in overlapping
layers of erosion control blanket, approximately 6 to 12 feet. The rock toe and soil ballast the
logs and reduce the risk of the logs floating away. Estimated construction cost for the complex
roughened large rock toe is summarized in Table C1-3.
-Complex log crib wall (Appendix A, Sheet 5).
The approach involves placing a log crib wall made of rough logs between the expected scour
depth and ordinary high water level, approximately 10 to 12 feet high. Stone is placed within the
log crib wall for ballast. Logs with attached root wads extending into the stream bank provide
roughness and additional wall stability. All logs are cabled together for enhancing stability.
Designs typically include piles driven to refusal or minimum depth of 10 feet. The cobble and
boulder stream bed material will likely prevent the piles from being cost-effectively driven or
excavated. They are assumed eliminated in the proposed design. Approximately 6 to 12 feet of
soil is placed above the crib wall and planted. Estimated construction cost for the complex log
crib wall is summarized in Table C1-3.
-Riprap with Roughened Rock Toe, LWD, and Riparian Plantings (Appendix A, Sheet 9).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
A launchable riprap toe 8 feet wide and 5 feet thick reduces the risk of scour and channel
incision undermining the revetment and provides additional stability. Logs or log bundles
spaced 6 to 10 feet are placed along the revetment toe for providing roughness and channel
complexity. The logs are buried in the road embankment for reducing the risk of them floating
away. Willow and alder are planted throughout the revetment and bank area above the
revetment. Estimated construction cost is summarized in Table C1-3.
-Riprap with Streambarbs (Appendix A, Sheet 11).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
Instead of a launchable riprap toe, 10 to 12 - 40 to 50 feet long streambarbs are proposed for
reducing shear stress and deflecting the river flow away from the revetment. The streambarbs
reduce the risk of scour and channel incision undermining the revetment, promote sediment
deposition and retention along the bank toe, and creates channel complexity. The bank, riprap,
streambarbs, and channel area between the streambarbs would be augmented with streambed
material, large woody debris, and planted with riparian vegetation for establishing a riparian
buffer. Estimated construction cost is summarized in Table C1-3.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 5
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
Minor Active River Channel Shift
An environmentally desirable approach would be to nudge the active river channel over enough
from the road to reestablish a riparian buffer. Ideally, the buffer would have the same erosion
resistance of a natural, wooded and vegetated river bank. The buffer would need to be wide
enough to allow some bank erosion without threatening the roadway. It would be made by
placing alluvial material over existing riprap revetment and unstable bank areas. To promote
vegetation establishment and soil mass stability, the finished surface of the buffer area should
not be steeper than 5(h):1(v). Assuming a 10 feet high bank, the width of the new buffer area
would be at least 50 feet. Existing relative stable riparian buffers observed along the river are at
least 40 to 50 feet wide and densely vegetated with alder and fir. The new buffer area would be
prone to erosion from active channel migration. The erosive forces are expected to be too large
for passive and bio-engineering methods to be effective by themselves. Hardened, more
erosion resistant components in the buffer system are needed for mitigating the erosive forces.
-Engineered-log-jam Groins.
ELJ’s groins constructed perpendicular to the stream bank and extending through the new
buffer area would control channel location and deflect river flow away from new buffer area
(Appendix A, Sheet 10). An ELJ’s buoyancy and sliding analysis (Design Guidelines for
Reintroducing Wood in Australian Streams, Abbe/Brooks, 2006) was completed assuming 6 feet
design flow depth, 5 feet design scour depth, 8 feet per second average flow velocity, 1.5
velocity correction factor, and 18-inch average trunk diameter. The river bed contains cobbles
and small boulders. Piles would need to penetrate the river bottom at least 20 to 30 feet for
providing adequate resistance to buoyancy and sliding. Tree trunk piles would likely splinter
before reaching the desired design depth. As wood decays, it losses strength and cannot resist
the shear stresses created by a sliding ELJ mass. Driving steel piles for pinning the ELJ
structure to the river bottom would be expensive and leave a tangle of steel piles protruding
from the river bottom. Based on the analysis, an ELJ structure 15 feet wide and ballasted with
stone is needed for achieving a minimum sliding factor-of-safety of 2.0, the minimum needed for
unknown flow conditions and resisting expected additional woody debris accumulation.
Each ELJ groin would be 60 feet long and constructed of three 15 feet wide by 20 feet long
modules. Assuming 2 to 3 feet gaps between logs and 8 layers, approximately 50 logs are
needed for each module and 150 for each groin. Based on the stability analysis, 150 cubic
yards of ballast stone is needed for each ELJ groin for achieving minimum sliding and buoyancy
factor-of-safeties of 2.0, the minimum needed for unknown flow conditions and resisting
expected additional woody debris accumulation. The logs are cabled together for keeping them
in place against expected flow depth and velocity and additional woody debris accumulation.
-Riprap Streambarbs.
Streambarbs are an alternative to using ELJ groins for controlling channel location and reducing
erosive forces (Appendix A, Sheet 10). Each stream barb would be angled upstream 30 degree
relative the bank line and approximately 100 feet long for fitting within the new riparian buffer.
Assuming Class 8 riprap, crest width is 8 feet. Barb thickness is 8 feet at base and 6 feet at tip.
Barb bottom width is 32 feet at base and 23 feet at tip. Approximately 470 cubic yards of riprap
is needed for each stream barb.
Based on review of historical satellite imagery, length of bank typically exposed to impinging
flood flow is estimated to be approximately 300 feet. The radius of curvature for active channel
is 500 to 800 feet. To effectively deflect the impinging river flow away from the new bank area,
the ELJ groins or stream barbs would need to be spaced every 100 to 150 feet. Assuming
Upper Hoh Road - Bank Failure Risk Reduction Study
p 6
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
2,000 feet of unstable bank and existing riprap revetment is covered with new stream bank;
approximately 15 to 20 ELJ groins or stream barbs are needed.
The existing revetment is assumed left in place. Stream bank area is constructed between the
ELJ groins or stream barbs by placing conserved and imported stream bed and bank material.
Willow and cottonwood trees are planted throughout the area. Willow fascines are placed along
the lower 3 to 6 feet of the bank toe for controlling erosion. Large wood is incorporated
randomly throughout the bank area.
Estimated construction cost is summarized in Table C1-3. Work will be within the active river
channel and requires temporarily diverting the river flow. Flow defection is assumed
accomplished with large sandbags or water-inflated bladders. Dewatering the work area would
be extremely difficult and expensive. Excavation and placing logs, stone, and new stream bank
fill material is assumed to take place in the water ponded behind the flow diversion structure.
Turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a ramp constructed over the existing riprap revetment. The ramp could provide
permanent access for maintenance. Upper Hoh Road traffic impacts are expected to be limited
to one-lane closures and short-term delays.
The HCMZ is narrows at the site relative to upstream and downstream reaches. Consequently,
it is expected that any active channel relocation would likely induce dramatic bank erosion and
stream avulsion, resulting in unnatural changes in the HCMZ boundaries and the likely loss of
private property downstream.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Major Active River Channel Shift
Shifting the active river channel away from the road eliminates the current riprap revetment
failure risk and road loss risk from bank erosion occurring between and downstream of the
existing revetments. Shifting the active river channel to flow across the point bar opposite the
existing riprap revetment could be accomplished with 8 to 10 ELJ’s, each at least 20 feet wide
and 60 to 100 feet long. All would be constructed within the active river channel. Top of the
ELJ’s are set equal to 100-year water surface, estimated to be approximately 5 to 6 feet above
the point bar surface. Bottom of the ELJ’s are set below the active channel thalweg elevation
and expected scour depth, approximately 6 feet below the point bar surface. Each engineered-
log-jam is ballasted with stone and logs cabled together for keeping them in place against
expected flow depth and velocity and additional woody debris accumulation.
The existing revetment is assumed left in place. No stream bank area is reconstructed. Off-
channel rearing and resting habitat is created along the toe of the existing riprap revetment. A
new 100 feet wide active flow channel would be constructed across the point bar for diverting
stream flow away from the construction area. Alluvial and plant materials from the channel
excavation would be used for the habitat reconstruction.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 7
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
Estimated construction cost is summarized in Table C1-3. Construction requires temporarily
diverting the river flow. Turbidity released is expected to be limited in extent and duration.
Access for construction is assumed down a ramp constructed over the existing riprap
revetment. The ramp could provide permanent access for maintenance. Upper Hoh Road
traffic impacts are expected to be limited to one-lane closures and short-term delays.
The HCMZ is narrows at the site relative to upstream and downstream reaches. Consequently,
it is expected that any active channel relocation would likely induce dramatic bank erosion and
stream avulsion, resulting in unnatural changes in the HCMZ boundaries and the likely loss of
private property downstream.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Environmental Clearance Considerations
This section of the Upper Hoh Road extends through primarily state trust lands with designated
critical marbled murrelet critical habitat located immediately adjacent to the north side of the
road and designated bull trout critical habitat in the Hoh River. Designated northern spotted owl
critical habitat is located approximately 3 miles to the east. Individuals of both species may be
present in the forest immediately north of the road at this location. No wetlands were identified
on the National Wetland Inventory Maps. A wetland survey and, if needed, delineation, would
need to be conducted to confirm this negative finding.
Environmental considerations for the treatment options at this location are as follows.
Continue Maintenance
Continued maintenance would require periodic replacement of material below the ordinary high
water mark where there is currently riprap revetment. The Seattle District of the U.S. Army
Corps of Engineers (Corps) has indicated that such work is exempt from Section 404 of the
Clean Water Act provided that all work occurs within the existing road prism. Consequently, no
state water quality permitting would be required.
In the event that one of the areas of concern should fail during a storm event, the roadway
failure would release a large amount of sediment into the river. Assuming this sediment release
occurs concurrently with the storm event it is unlikely that this would result in a considerable
increase over the background condition.
Repair of the road after failure would likely cause considerable environmental impacts. The
need to quickly reestablish access would permit no design time typically needed for more
habitat-friendly solutions, thus relying on the use of conventional methods including riprap.
Also, work would likely need to occur outside of the in-water work window. The need for rapid
response to an emergency situation will result in environmental impacts to sensitive habitats
that would likely warrant expensive mitigation. If this option is pursued, Jefferson County may
want to consider developing, in advance, an emergency plan in coordination with the U.S. Fish
Upper Hoh Road - Bank Failure Risk Reduction Study
p 8
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
and Wildlife Service (Service) and the Washington Department Fish and Wildlife (WDFW) for
developing more habitat-friendly designs that can be implemented in the event of a failure.
Such a plan may reduce mitigation costs.
Relocate Road
Given the proximity of designated marbled murrelet habitat to the road at this location,
relocation would involve removal of critical habitat. Relocation of the road may improve aquatic
habitat for the threatened bull trout as the existing riprap revetment would be removed and a
streambank length of 1800 feet would be restored using streambarbs, ELJ’s, and vegetation. A
biological assessment would need to be prepared evaluating the effects to the marbled
murrelet, the northern spotted owl, and the bull trout.
If wetlands are determined to be present in the road relocation area, permitting from the Corps
and the Washington Department of Ecology (DOE) would be required. If the waters of the US
would be impacted only by the removal of the riprap revetment and the restoration of the
steambank, then a Nationwide permit may cover this work. If no protocol surveys are done for
the marbled murrelet or the northern spotted owl, or if protocol surveys are done and species
presence is confirmed, construction would have to adhere to seasonal and daily noise
restrictions.
Stabilize Existing Road Embankment
Due to lack of design detail, no distinction is made in terms of environmental impacts for each of
the four stabilization methods discussed in this report. However, based on conversations with
the Corps, the more natural and “softened” (logs and vegetation) the bank stabilization method,
the easier it will be to permit the activity. Riprap alone is the most difficult bank stabilization
method to be permitted.
Bank stabilization would likely have no permanent impacts to designated marbled murrelet or
northern spotted owl critical or suitable habitat. Temporary impacts would likely occur for all
three listed species, thereby requiring the preparation of a biological assessment. In addition to
complying with the in-water work window, certain construction activities may be limited to certain
times of the day or season to minimize disturbing the marbled murrelet and the northern spotted
owl. Placement of fill will trigger the need for a permit under Section 404 of the Clean Water Act
and 401 certification. Whether an individual permit or the simpler nationwide permit is sufficient
depends on the design and extent of impacts.
Scope of work and the limited in-water work window would likely require a petition for a waiver
and extension from the WDFW.
Minor and Major Active River Channel Shift
This could have a dramatic effect on the existing river system. The extent to which the option
helps or harms the aquatic habitat would need determined through modeling and formal
consultation with the Service, the Hoh Tribe, and the WDFW. This work would require an
individual permit from the Corps and 401 Certification from the DOE.
A biological assessment would need to be prepared evaluating short and long term impacts to
bull trout and short term construction impacts to the marbled murrelet and the northern spotted
owl.
In addition, geomorphic assessments would need to be conducted for assessing effect this
option may have on downstream properties.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 9
Site C1 – County Milepost 3.7 - 4.0 Bank Stabilization
Due to the scope of work and the limited in-water work window, WDFW would likely need to be
petitioned for an extension.
Each ELJ requires a number of trees to be cut down. Approximately 1,500 and 3,000 logs are
needed for the minor and major active river channel shift options, respectively. Cutting these
trees would have a direct impact on some forest’s ecosystem and watershed’s health.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 10
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 11
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 12
Photos C1a - CMP 3.7 Bank Stabilization
PHOTO C1a- 1
PHOTO C1a- 2
PHOTO C1a- 3
12/12/2012
12 feet high stream bank undercut and
eroding. Large woody debris deflects
stream flow towards stream bank,
aggravating erosion.
Heavily wooded riprap revetment
appears moderately stable.
Bank erosion within 20 feet of road
pavement edge.
Downstream end of existing riprap
revetment - looking downstream at
eroding stream bank.
Large woody debris deflects stream flow
towards stream bank, aggravating
erosion.
Downstream end of existing riprap
revetment - looking upstream at existing
riprap revetment.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 13
Photos C1a - CMP 3.7 Bank Stabilization
PHOTO C1a- 4
PHOTO C1a- 5
PHOTO C1a- 6
12/12/2012
Large woody debris deflects stream flow
towards stream bank, aggravating
erosion. Woody debris jam could
become larger and persist overtime.
Bank erosion within 20 feet of road
pavement edge.
12 feet high stream bank undercut and
eroding. Large woody debris deflects
stream flow towards stream bank,
aggravating erosion.
Mid-channel sediment deposits and large
woody debris adjacent to site.
Large woody debris deflects stream flow
towards stream bank, aggravating
erosion. Woody debris jam could
become larger and persist overtime.
Mid-channel sediment deposits and large
woody debris adjacent to site.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 14
Photos C1b - CMP 3.9 Bank Stabilization
PHOTO C1b- 1
PHOTO C1b- 2
PHOTO C1b- 3
12/12/2012
16 feet high stream bank. Erosion scarp
within 10 feet of road pavement edge.
Large woody debris deflects stream flow
towards bank, aggravating erosion.
16 feet high stream bank undercut and
eroding. Trees have and are falling into
the river. Middle revetment segment
appears stable.
Bank erosions site at MP C3.9 - looking
upstream.
Downstream riprap revetment segment -
looking upstream.
Finished slope is steep, some riprap has
been dislodged from middle slope and
toe areas.
Gap in bank erosion control between
downstream and middle revetment
segments - looking downstream.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 15
Photos C1b - CMP 3.9 Bank Stabilization
PHOTO C1b- 4
PHOTO C1b- 5
PHOTO C1b- 6
12/12/2012
Riprap appears moderately stable.
Bank erosions site at MP C3.9 - looking
downstream.
16 feet high stream bank. Erosion scarp
within 10 feet of road pavement edge.
Large woody debris deflects stream flow
towards bank, aggravating erosion.
Downstream riprap revetment segment in
top center photo.
Bank erosions site at MP C3.9 - existing
downstream riprap revetment segment
upstream end.
Large woody debris deflects stream flow
towards bank, aggravating erosion.
Some riprap has been dislodged.
Middle riprap revetment segment -
looking upstream from C1b.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 16
Photos C1c - CMP 4.0 Bank Stabilization
PHOTO C1c- 1
PHOTO C1c- 2
PHOTO C1c- 3
12/12/2012
18 feet high stream bank undercut and
eroding. Erosion scarp 15 to 20 feet of
road pavement edge. Trees have and
are falling into the river.
Upstream revetment segment heavily
treed and appears stable.
Gap in bank erosion control between
upstream and middle revetment
segments - looking upstream from C1b.
Gap in bank erosion control between
upstream and middle revetment
segments - looking upstream.
18 feet high stream bank undercut and
eroding. Erosion scarp 15 to 20 feet of
road pavement edge. Trees have and
are falling into the river.
Upstream end of bank erosion gap -
looking downstream.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 17
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mi
t
i
g
a
t
i
o
n
o
f
e
x
i
s
t
i
n
g
ro
a
d
w
a
y
s
l
o
p
e
t
o
r
i
p
a
r
i
a
n
zo
n
e
-
i
n
s
t
a
l
l
s
t
r
e
a
m
b
a
r
b
s
an
d
E
L
J
'
s
f
o
r
p
r
e
s
e
r
v
i
n
g
ri
p
a
r
i
a
n
z
o
n
e
.
Ro
c
k
t
o
e
w
i
t
h
L
W
D
.
Lo
g
c
r
i
b
w
a
l
l
w
i
t
h
r
o
u
g
h
n
e
s
s
el
e
m
e
n
t
s
.
Ri
p
r
a
p
s
i
m
i
l
a
r
t
o
w
h
a
t
i
s
co
m
m
o
n
l
y
u
s
e
d
a
l
o
n
g
U
p
p
e
r
Ho
h
R
i
v
e
r
R
o
a
d
em
b
a
n
k
m
e
n
t
.
Ba
n
k
a
r
e
a
p
l
a
n
t
e
d
w
i
t
h
wi
l
l
o
w
a
n
d
a
l
d
e
r
.
Construct new stream bank area over unstable and revetment areas.Construct new stream bank area over unstable and revetment areas.Shift active flow channel to flow across point bar away from revetment area.
Ab
i
l
i
t
y
t
o
p
r
e
s
e
r
v
e
a
n
d
o
p
e
r
a
t
e
t
h
e
r
o
a
d
w
a
y
i
n
a
s
p
e
c
i
f
i
c
l
o
c
a
t
i
o
n
(M
o
s
t
a
b
l
e
5
,
l
e
a
s
t
a
b
l
e
1
)
3
Re
d
u
c
e
s
r
i
s
k
o
f
a
c
a
t
a
s
t
r
o
p
h
i
c
ro
a
d
f
a
i
l
u
r
e
d
u
r
i
n
g
e
x
t
r
e
m
e
fl
o
o
d
e
v
e
n
t
.
3
Be
t
t
e
r
t
h
a
n
w
h
e
r
e
i
t
i
s
,
b
u
t
t
h
e
ri
v
e
r
m
a
y
e
v
e
n
t
u
a
l
l
y
m
i
g
r
a
t
e
no
r
t
h
a
n
d
i
m
p
a
c
t
r
o
a
d
a
g
a
i
n
.
5
Gr
e
a
t
l
y
r
e
d
u
c
e
s
r
i
s
k
o
f
a
ca
t
a
s
t
r
o
p
h
i
c
r
o
a
d
f
a
i
l
u
r
e
d
u
r
i
n
g
ex
t
r
e
m
e
f
l
o
o
d
e
v
e
n
t
.
5
Gr
e
a
t
l
y
r
e
d
u
c
e
s
r
i
s
k
o
f
a
ca
t
a
s
t
r
o
p
h
i
c
r
o
a
d
f
a
i
l
u
r
e
d
u
r
i
n
g
ex
t
r
e
m
e
f
l
o
o
d
e
v
e
n
t
.
5
Gr
e
a
t
l
y
r
e
d
u
c
e
s
r
i
s
k
o
f
a
ca
t
a
s
t
r
o
p
h
i
c
r
o
a
d
f
a
i
l
u
r
e
d
u
r
i
n
g
ex
t
r
e
m
e
f
l
o
o
d
e
v
e
n
t
.
5
Gr
e
a
t
l
y
r
e
d
u
c
e
s
r
i
s
k
o
f
a
ca
t
a
s
t
r
o
p
h
i
c
r
o
a
d
f
a
i
l
u
r
e
d
u
r
i
n
g
ex
t
r
e
m
e
f
l
o
o
d
e
v
e
n
t
.
5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.
Ro
a
d
w
a
y
s
u
s
t
a
i
n
a
b
i
l
i
t
y
(
l
i
f
e
o
f
s
o
l
u
t
i
o
n
)
(L
o
n
g
e
s
t
5
,
s
h
o
r
t
e
s
t
1
)
1
In
c
r
e
a
s
e
d
m
a
i
n
t
e
n
a
n
c
e
i
n
t
h
e
fu
t
u
r
e
m
i
t
i
g
a
t
i
n
g
c
l
i
m
a
t
e
ch
a
n
g
e
o
r
a
f
t
e
r
l
a
r
g
e
f
l
o
o
d
ev
e
n
t
s
.
3
In
c
r
e
a
s
e
r
o
a
d
l
i
f
e
r
e
d
u
c
e
s
fu
t
u
r
e
r
i
s
k
f
r
o
m
r
i
v
e
r
.
R
o
a
d
ne
a
r
h
i
l
l
s
i
d
e
m
a
y
e
x
p
e
r
i
e
n
c
e
la
n
d
s
l
i
d
e
s
a
n
d
d
e
b
r
i
s
f
l
o
w
s
.
3
Re
q
u
i
r
e
s
m
o
d
e
r
a
t
e
a
m
o
u
n
t
o
f
wo
o
d
r
e
p
l
a
c
e
m
e
n
t
a
n
d
ma
i
n
t
e
n
a
n
c
e
.
1
Re
q
u
i
r
e
s
s
u
b
s
t
a
n
t
i
a
l
a
m
o
u
n
t
o
f
wo
o
d
r
e
p
l
a
c
e
m
e
n
t
a
n
d
ma
i
n
t
e
n
a
n
c
e
.
3
Re
q
u
i
r
e
s
m
o
d
e
r
a
t
e
a
m
o
u
n
t
o
f
wo
o
d
r
e
p
l
a
c
e
m
e
n
t
a
n
d
ma
i
n
t
e
n
a
n
c
e
.
5
Re
q
u
i
r
e
s
m
o
d
e
r
a
t
e
l
e
v
e
l
o
f
ma
i
n
t
e
n
a
n
c
e
.
1Requires substantial amount of wood replacement and maintenance.5 Requires moderate level of maintenance.1Requires substantial amount of wood replacement and maintenance.
Im
p
a
c
t
t
o
h
i
l
l
s
i
d
e
s
t
a
b
i
l
i
t
y
a
d
j
a
c
e
n
t
t
o
s
i
t
e
(M
o
s
t
l
i
k
e
l
y
1
;
l
e
a
s
t
l
i
k
e
l
y
5
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Ro
a
d
n
e
a
r
h
i
l
l
s
i
d
e
m
a
y
ex
p
e
r
i
e
n
c
e
l
a
n
d
s
l
i
d
e
s
a
n
d
de
b
r
i
s
f
l
o
w
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Po
t
e
n
t
i
a
l
t
o
r
e
d
u
c
e
e
r
o
s
i
o
n
o
f
b
a
n
k
s
a
d
j
a
c
e
n
t
to
s
i
t
e
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3 Adjacent bank erosion will continue.3 Adjacent bank erosion will continue.1 Likely increase down stream right bank erosion.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
h
r
e
a
t
e
n
e
d
a
n
d
E
n
d
a
n
g
e
r
e
d
(T
&
E
)
t
e
r
r
e
s
t
r
i
a
l
s
p
e
c
i
e
s
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
a
n
d
po
t
e
n
t
i
a
l
l
y
T
&
E
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
&
E
f
i
s
h
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
Ri
p
r
a
p
p
l
a
c
e
d
a
l
o
n
g
b
a
n
k
re
d
u
c
e
s
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
B
a
r
b
s
re
q
u
i
r
e
s
i
g
n
i
f
i
c
a
n
t
e
x
c
a
v
a
t
i
o
n
in
t
o
c
h
a
n
n
e
l
b
e
d
.
3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.
Im
p
a
c
t
t
o
u
p
l
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
W
e
t
l
a
n
d
s
a
n
d
W
a
t
e
r
s
o
f
t
h
e
U
.
S
.
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
Ri
p
r
a
p
p
l
a
c
e
m
e
n
t
i
n
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
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1 Requires major in stream construction.1 Requires major in stream construction.1 Requires major in stream construction.
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0 No impacts.0 No impacts.0 No expected impacts.
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5Provides woody debris for habitat complexity and biological processes.3Provides some woody debris for habitat complexity and biological processes.5Provides woody debris for habitat complexity and biological processes.
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3Some impacts expected from bank erosion downstream of site. 3Some impacts expected from bank erosion downstream of site. 1 Impacts likely from bank erosion downstream of site.
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1 Boaters could become trapped in ELJ's.3 Boaters could become trapped in root wads.1 Boaters could become trapped in ELJ's.
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$257,295 $1,253,402 $572,532 $746,069
SC
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3
3
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3
1 11Minor Active River Channel Shift
M
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p
18
Date: 3/14/2013
By: S. Leon
Flood
Frequency
(yr)
Exceedance
Probability
Flood
Damage
Average
Flood
Damage
Delta
Exceedance
Probability
Annual Risk
Cost
No damage.2 0.5 $0
$0 0.3 $0
No damage.5 0.2 $0
$0 0.1 $0
No damage.10 0.1 $0
$150,000 0.06 $9,000
Place riprap.25 0.04 $300,000
$300,000 0.02 $6,000
Place riprap.50 0.02 $300,000
$300,000 0.01 $3,000
Place riprap.100 0.01 $300,000
$300,000 0.01 $3,000
0 $300,000
$21,000
$0
Disc. rate, i 0.07125 Serv. life, n 50 CFR 0.0736
$0
Total Expected Cost (Annual)$21,000
Summary
Notes:
1. Method from HEC-17, April 1981.
Table C1-2. Total Expected Cost
Project: Hoh River Road Bank Erosion Risk Study
Alternative: Continue Maintenance
Site: C1 - CMP 3.7 to 4.0 Bank Stabilization
Capital Cost
Annualized Capital Cost
Assume 300 feet ($1k/ft) of revetment repair and bank armoring for each flood damage event.
Annualized Capital
Cost
Total Annual Risk Cost
Upper Hoh Road - Bank Failure Risk Reduction Study
p 19
Table C1-3. Cost Estimates
Site:
Relocate Road
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 448,000$ 448,000$
New Road LF 4,000 500$ 2,000,000$
Hillside Stabilization LS 1 200,000$ 200,000$
Remove Existing Revetment LF 2,500 200$ 500,000$
Streambank Reconstruction LF 1,800 1,000$ 1,800,000$
Streambarbs EA 10 40,000$ 400,000$
ELJ's EA 5 300,000$ 1,500,000$
Total Construction Cost without Contingencies 6,848,000$
Contingency 30% of construction cost 2,054,400$
Total Construction Cost 8,902,400$
Compliance 5% of total construction cost 445,120$
Predesign/design (PE)15% of total construction cost 1,335,360$
Construction Engineering (CE)15% of total construction cost 1,335,360$
ROW 100,000$
Riprap replacement -20% replacement every 50 years 80,000$
Wood replacement -full log replacement every 30 years 1,500,000$
TOTAL Capital Cost Cost/Foot 3,425$ 13,698,240$
Annualized Capital Cost Discount rate, i 0.07125 1,008,288$
Service life, n 50 years
CFR 0.0736071
Complex Roughened Large Rock Toe
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 64,221$ 64,221$
Remove Existing Revetment LF 200 200$ 40,000$
Rock H 12 ft T 5 ft CY 2,356 180$ 424,000$
L 1060 ft
Logs L 1060 ft XS 8 ft EA 133 2,000$ 265,000$
Soil H 12 ft T 10 ft CY 4,711 40$ 188,444$
L 1060 ft
Total Construction Cost without Contingencies 981,666$
Contingency 30% of construction cost 294,500$
Total Construction Cost 1,276,165$
Compliance 5% of total construction cost 63,808$
Predesign/design (PE)15% of total construction cost 191,425$
Construction Engineering (CE)15% of total construction cost 191,425$
ROW -$
Riprap replacement -20% replacement every 50 years 84,800$
Wood replacement -full log replacement every 30 years 265,000$
TOTAL Capital Cost Cost/Foot 1,955$ 2,072,623$
Annualized Capital Cost Discount rate, i 0.07125 152,560$
Service life, n 50 years
CFR 0.0736071
C1 - CMP 3.7 to 4.0 - Bank Stabilization
Upper Hoh Road - Bank Failure Risk Reduction Study
p 20
Table C1-3. Cost Estimates
Complex Log Crib Wall
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 80,298$ 80,298$
Remove Existing Revetment LF 200 200$ 40,000$
Rock H 12 ft T 5 ft CY 2,356 120$ 282,667$
L 1060 ft
Logs L 1060 ft H 12 ft EA 318 2,000$ 636,000$
Dia 2 ft Row 6
log l 20 ft No. 318
Piles EA 0 -$ -$
Soil H 12 ft T 10 ft CY 4,711 40$ 188,444$
L 1060 ft
Total Construction Cost without Contingencies 1,227,409$
Contingency 30% of construction cost 368,223$
Total Construction Cost 1,595,632$
Compliance 5% of total construction cost 79,782$
Predesign/design (PE)15% of total construction cost 239,345$
Construction Engineering (CE)15% of total construction cost 239,345$
ROW -$
Riprap replacement -20% replacement every 50 years 56,533$
Wood replacement -full log replacement every 30 years 636,000$
TOTAL Capital Cost Cost/Foot 2,686$ 2,846,636$
Annualized Capital Cost Discount rate, i 0.07125 209,533$
Service life, n 50 years
CFR 0.0736071
Riprap with Roughened Rock Toe, LWD, and Riparian Plantings
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 116,337$ 116,337$
Remove Existing Revetment LF 200 200$ 40,000$
Riprap H 13 ft T 5 ft CY 6,674 180$ 1,201,333$
L 1060 ft SS 2 (h):1(v)
TW 8 ft TT 5 ft
Logs L 1060 ft XS 8 ft EA 133 2,000$ 265,000$
Willow 1200 sy XS 2 EA 600 10$ 6,000$
Alder 1200 sy XS 1 EA 1,200 20$ 24,000$
Soil H 8 ft T 10 ft CY 3,141 40$ 125,630$
L 1060 ft
Total Construction Cost without Contingencies 1,778,300$
Contingency 30% of construction cost 533,490$
Total Construction Cost 2,311,790$
Compliance 5% of total construction cost 115,590$
Predesign/design (PE)15% of total construction cost 346,769$
Construction Engineering (CE)15% of total construction cost 346,769$
ROW -$
Riprap replacement -20% replacement every 50 years 240,267$
Wood replacement -full log replacement every 30 years 265,000$
TOTAL Capital Cost Cost/Foot 3,421$ 3,626,184$
Annualized Capital Cost Discount rate, i 0.07125 266,913$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 21
Table C1-3. Cost Estimates
Riprap with Streambarbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 116,221$ 116,221$
Remove Existing Revetment LF 200 200$ 40,000$
Riprap H 13 ft T 5 ft CY 5,104 180$ 918,667$
L 1060 ft SS 2 (h):1(v)
TW 0 ft TT 0 ft
Streambarbs EA 11 40,000$ 440,000$
Logs L 1060 ft XS 20 ft EA 53 2,000$ 106,000$
Willow 1200 sy XS 2 EA 600 10$ 6,000$
Alder 1200 sy XS 1 EA 1,200 20$ 24,000$
Soil H 8 ft T 10 ft CY 3,141 40$ 125,630$
L 1060 ft
Total Construction Cost without Contingencies 1,776,517$
Contingency 30% of construction cost 532,955$
Total Construction Cost 2,309,472$
Compliance 5% of total construction cost 115,474$
Predesign/design (PE)15% of total construction cost 346,421$
Construction Engineering (CE)15% of total construction cost 346,421$
ROW -$
Riprap replacement -20% replacement every 50 years 271,733$
Wood replacement -full log replacement every 30 years 106,000$
TOTAL Capital Cost Cost/Foot 3,298$ 3,495,521$
Annualized Capital Cost Discount rate, i 0.07125 257,295$
Service life, n 50 years
CFR 0.0736071
Major River Channel Shift
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 266,000$ 266,000$
Channel Excavation - 100 feet by 5 feet LF 2,000 300$ 600,000$
Rearing and Resting Habitat Construction AC 4 50,000$ 200,000$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction LF - 1,000$ -$
Streambarbs EA - 40,000$ -$
ELJ's - 20 ft by 60 ft EA 10 300,000$ 3,000,000$
Total Construction Cost without Contingencies 4,066,000$
Contingency 30% of construction cost 1,219,800$
Total Construction Cost 5,285,800$
Compliance 5% of total construction cost 264,290$
Predesign/design (PE)15% of total construction cost 792,870$
Construction Engineering (CE)15% of total construction cost 792,870$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 3,000,000$
TOTAL Capital Cost Cost/Foot 5,068$ 10,135,830$
Annualized Capital Cost Discount rate, i 0.07125 746,069$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 22
Table C1-3. Cost Estimates
Minor River Channel Shift - ELJ Groins
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 467,460$ 467,460$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 1,700 1,200$ 2,040,000$
Large Wood EA 100 1,500$ 150,000$
ELJ groin - 15 ft by 60 ft (3 x 15 ft by 20 ft mod.)EA 20 224,400$ 4,488,000$
Primary logs 50
Pin logs 4
Ballast stone 50
Cabling 1
74,800$
No. modules/ ELJ groin 3 224,400$
Total Construction Cost without Contingencies 7,145,460$
Contingency 30% of construction cost 2,143,638$
Total Construction Cost 9,289,098$
Compliance 5% of total construction cost 464,454.90$
Predesign/design (PE)15% of total construction cost 1,393,365$
Construction Engineering (CE)15% of total construction cost 1,393,365$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 4,488,000$
TOTAL Capital Cost Cost/Foot 5,464$ 17,028,282$
Annualized Capital Cost Discount rate, i 0.07125 1,253,402$
Service life, n 50 years
CFR 0.0736071
Minor River Channel Shift - Stream Barbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 271,740$ 271,740$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 1,700 1,200$ 2,040,000$
Large Wood EA 100 1,500$ 150,000$
Streambarbs Length 100 ft EA 20 84,600$ 1,692,000$
Crest width 8 ft
Average bot. width 28 ft
Average thickness 7 ft
Volume 470 cy
Cost/cy 180 $/cy Cost/barb 84,600$
Total Construction Cost without Contingencies 4,153,740$
Contingency 30% of construction cost 1,246,122$
Total Construction Cost 5,399,862$
Compliance 5% of total construction cost 269,993$
Predesign/design (PE)15% of total construction cost 809,979$
Construction Engineering (CE)15% of total construction cost 809,979$
ROW -$
Riprap replacement -20% replacement every 50 years 338,400$
Wood replacement -full log replacement every 30 years 150,000$
TOTAL Capital Cost Cost/Foot 3,176$ 7,778,214$
Annualized Capital Cost Discount rate, i 0.07125 572,532$
Service life, n 50 years
CFR 0.0736071
180$ 9,000$
1,000$ 1,000$
60,000$ 1,200$
1,200$ 4,800$
Upper Hoh Road - Bank Failure Risk Reduction Study
p 23
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 24
C2 - COUNTY MILEPOST 4.4
BANK STABILIZATION
Upper Hoh Road - Bank Failure Risk Reduction Study
p 25
Site C2 – County Milepost 4.4 Bank Stabilization
SITE C2 – COUNTY MILEPOST 4.4 BANK STABILIZATION
Site Conditions
The site parallels the outside bank of a river bend (Fig. C2-1). Approximately 3,900 lineal feet of
riprap revetment along the apex of the river bend appears to be generally effectively controlling
road embankment erosion. Approximately 1,150 feet of the riprap revetment is included with
site C1. The 2 to 4 feet diameter riprap comprising the revetment is generally properly graded
and placed. Revetments are in two segments. Upstream and downstream segments are
approximately 1,400 and 1,350 feet long, respectively. Downstream segment is also the
upstream revetment segment for site C1. The segments are densely planted with willow and
alder and appear generally stable. Currently, a large portion of the downstream segment is
experiencing impinging flood flow. Down-valley translation of the meander channel at the site
could eventually erode away a point bar, exposing the entire revetment segment to impinging
flood flows.
Distance of stream bank between the upstream and downstream revetment segments is
approximately 350 feet. Currently, a point bar directs stream flow towards the bank. Toe
erosion and undermining of the stream bank is occurring (Photo C2-1). The stream bank toe is
approximately 10 to 20 feet away and 8 feet below the road pavement edge (Photo C2-2).
Cobbles and small boulders naturally armor the lower 3 to 4 feet of the bank. A soft, highly
fractured silt-stone was observed at several areas along the bank toe (Photo C2-3 and 4). It
and the cobbles and boulders inhibit the toe erosion. The upper 5 to 6 feet of bank is a highly
erodible, finer-grained alluvial material. Large trees are and dense vegetation is sparse (Photo
C2-2). Where present they have inhibited the bank erosion. Erosion scarps have reached
within 10 feet of the pavement edge. The scarps tend to be less than 20 feet long.
An erosion resistant poorly consolidated alluvium terrace deposit has limited river bend
migration to the north and south. The terrace deposit represents the historical channel
migration zone (HCMZ) right and left (looking downstream) boundaries (Geomorphic
Assessment of the Hoh River in Washington State, Bureau of Reclamation, July 2004). Width
of the HCMZ is approximately 500 to 1,000 feet. The road embankment coincides with the
HCMZ right boundary and valley wall. Based on historical satellite imagery, the active channel
has not changed significantly in width and location since 1994 (Fig. C2-2). The point of active
flow channel impingement on the right bank has sifted downstream approximately 1,000 feet
since 1994.
Continued stream bank erosion could undermine the road. Based on current channel alignment
and expected limited channel alignment shifts, the risk of a catastrophic road embankment
failure is high. Water depth at typically normal annual low flow conditions is estimated to be 4 to
6 feet.
Considered Options
Continuing maintenance, relocating the road, installing additional bank stabilization, minor active
river channel shift, and major active river channel shift were considered. Table C2-1 presents
an evaluation and ranking of the options against design selection criteria.
Riprap is expected to be lost during extreme flooding, requiring replenishment for maintaining
the riprap installation’s effectiveness. Total Capital and Annualized Total Capital Costs provided
in Table C2-1 assume 20 percent of the riprap in an installation is replaced every 50 years.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 26
Site C2 – County Milepost 4.4 Bank Stabilization
Douglas fir and hemlock are the most commonly available logs in the area. Douglas-fir logs can
remain durable in wetting-drying conditions for 25 to 60 years (Tech. Supp. 14J, Use of Large
Woody Material for Habitat and Bank Protection, Part 654, National Engineering Handbook,
USDA, Natural Resources Conservation Service). Hemlock is the least durable of the conifers.
Because the tree quality and species to be used in the structures is not known, Total Capital
and Annualized Total Capital Costs provided in Table C2-1 assume wood used in the
alternatives is replaced every 30 years.
Continue Maintenance
Continued maintenance involves monitoring the stream bank areas for excessive bank erosion.
Stream bank toe erosion could progress to the point that undermining of the road is imminent.
Continued maintenance is placing riprap in an emergency action or after flooding as needed for
preventing a road closure. Placing riprap as an emergency action may be hazardous or difficult.
The emergency-placed riprap may not be effective in controlling the erosion.
A Total Expected Cost analysis (HEC-17, FHWA, April 1981) was completed for estimating total
expected cost repairing flood-induced road damage over a 50-year service-life. Based on
observed proximity of channel to roadway and resistance of the natural bank armoring, the
analysis assumes damage requiring addition of new riprap revetment placed as an emergency
action for stabilizing an eroding river bank occurs for floods equal to and larger than the 10-year
flood event. Based on review of historical satellite imagery, length of bank typically exposed to
impinging flood flow is estimated to be approximately 300 feet. Based on vegetation distribution
and age and estimated riprap placement sequencing, the length of past revetment installations
ranged from 200 to 500 feet. Assuming 300 feet total for each flood damage event and a cost
of $1,000 per foot, the total expected annual cost is $45,000 (Table C2-2, Total Expected Cost).
Relocate Road
Shifting the road at least 100 to 200 feet away from the active river channel edge provides a
riparian buffer wide enough for containing a reconstructed stream bank area, eliminating the
need for continuous revetment bank stabilization. The 260 feet high terrace slope is
immediately adjacent to the roadway. A shift would mean an alignment that crosses the terrace
slope. Slumping observed on the terrace slope suggests the terrace slope is not geotechnically
stable. A new road alignment located across the terrace slope would experience landslides and
debris flows that could potentially bury the road with debris. The road alignment may require
significant foundation stabilization for mitigating landslides. Length of reroute is estimated to be
1,200 feet for connecting to existing road segments that are behind stable appearing riprap
revetments.
The unprotected stream bank will continue to erode and migrate to the north. Streambarbs,
engineered-log-jams (ELJ’s), and planted vegetation would inhibit the bank erosion and lateral
migration and preserve a riparian buffer between the active river channel and road
embankment. The alternative requires monitoring and repair of the streambarbs and ELJ’s to
remain effective in controlling the bank erosion and lateral migration. Approximately 350 feet of
the stream bank is reconstructed.
Estimated construction cost for the new road, existing road removal, three streambarbs, and two
ELJ’s is summarized in Table C2-3. Stabilizing landslides may require significantly more
money. Road construction is expected to occur outside the active flow channel. Streambarb,
ELJ, and stream bank construction is expected to occur within the active flow channel. Turbidity
released is expected to be limited in extent and duration. Access for construction is assumed
from the existing road. Constructing the new road alignment first and then switching the Upper
Upper Hoh Road - Bank Failure Risk Reduction Study
p 27
Site C2 – County Milepost 4.4 Bank Stabilization
Hoh Road traffic over before removing the existing road reduces traffic impacts to one-lane
closures and short-term delays.
Stabilize Existing Road Embankment
Approximately 350 feet of stream bank is proposed for stabilization.
Alternatives evaluated;
Complex roughened large rock toe.
Complex log crib wall.
Riprap with roughened rock toe, LWD, and riparian plantings.
Riprap with streambarbs.
Based on field evidence, the site will experience high shear stress, 10 to 12 feet deep flood
flows, and abundant floating debris. It is critical that the stabilization methods be properly
designed and anchored for maintaining effectiveness and surviving the expected flood
conditions.
Construction for all the alternatives is expected to occur entirely within the active flow channel
and requires excavating into the streambed and stream bank. Stream work would be
accomplished in flowing water. Assuming the work is completed during low flow periods,
turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a temporary access route built of riprap and logs. The access route would be
removed after construction is completed. Upper Hoh Road traffic impacts are expected to be
limited to one-lane closures and short-term delays.
-Complex roughened large rock toe (Appendix A, Sheet 4).
The approach involves placing a rock toe between the expected scour depth and ordinary high
water level, approximately 10 to 12 feet high and 5 feet thick. Log bundles spaced 6 to 10 feet
are placed at the bottom of the rock toe. Soil placed above the rock toe in overlapping layers of
erosion control blanket, approximately 2 to 4 feet. The rock toe and soil ballast the logs and
reduce the risk of the logs floating away. Estimated construction cost for the complex
roughened large rock toe is summarized in Table C2-3.
-Complex log crib wall (Appendix A, Sheet 5).
The approach involves placing a log crib wall made of rough logs between the expected scour
depth and ordinary high water level, approximately 10 to 12 feet high. Stone is placed within the
log crib wall for ballast. Logs with attached root wads extending into the stream bank provide
roughness and additional wall stability. All logs are cabled together for enhancing stability.
Designs typically include piles driven to refusal or minimum depth of 10 feet. The cobble and
boulder stream bed material will likely prevent the piles from being cost-effectively driven or
excavated. They are assumed eliminated in the proposed design. Approximately 2 to 4 feet of
soil is placed above the crib wall and planted. Estimated construction cost for the complex log
crib wall is summarized in Table C2-3.
-Riprap with Roughened Rock Toe, LWD, and Riparian Plantings (Appendix A, Sheet 9).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
A launchable riprap toe 8 feet wide and 5 feet thick reduces the risk of scour and channel
incision undermining the revetment and provides additional stability. Logs or log bundles
Upper Hoh Road - Bank Failure Risk Reduction Study
p 28
Site C2 – County Milepost 4.4 Bank Stabilization
spaced 6 to 10 feet are placed along the revetment toe for providing roughness and channel
complexity. The logs are buried in the road embankment for reducing the risk of them floating
away. Willow and alder are planted throughout the revetment and bank area above the
revetment. Estimated construction cost is summarized in Table C2-3.
-Riprap with Streambarbs (Appendix A, Sheet 11).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
Instead of a launchable riprap toe, 10 to 12 - 40 to 50 feet long streambarbs are proposed for
reducing shear stress and deflecting the river flow away from the revetment. The streambarbs
reduce the risk of scour and channel incision undermining the revetment, promote sediment
deposition and retention along the bank toe, and creates channel complexity. The bank, riprap,
streambarbs, and channel area between the streambarbs would be augmented with streambed
material, large woody debris, and planted with riparian vegetation for establishing a riparian
buffer. Estimated construction cost is summarized in Table C2-3.
Minor Active River Channel Shift
An environmentally desirable approach would be to nudge the active river channel over enough
from the road to reestablish a riparian buffer. Ideally, the buffer would have the same erosion
resistance of a natural, wooded and vegetated river bank. The buffer would need to be wide
enough to allow some bank erosion without threatening the roadway. It would be made by
placing alluvial material over existing riprap revetment and unstable bank areas. To promote
vegetation establishment and soil mass stability, the finished surface of the buffer area should
not be steeper than 5(h):1(v). Assuming an 8 feet high bank, the width of the new buffer area
would be at least 40 feet. Existing relative stable riparian buffers observed along the river are at
least 40 to 50 feet wide and densely vegetated with alder and fir. The new buffer area would be
prone to erosion from active channel migration. The erosive forces are expected to be too large
for passive and bio-engineering methods to be effective by themselves. Hardened, more
erosion resistant components in the buffer system are needed for mitigating the erosive forces.
-Engineered-log-jam Groins.
ELJ’s groins constructed perpendicular to the stream bank and extending through the new
buffer area would control channel location and deflect river flow away from new buffer area
(Appendix A, Sheet 10). An ELJ’s buoyancy and sliding analysis (Design Guidelines for
Reintroducing Wood in Australian Streams, Abbe/Brooks, 2006) was completed assuming 6 feet
design flow depth, 5 feet design scour depth, 8 feet per second average flow velocity, 1.5
velocity correction factor, and 18-inch average trunk diameter. The river bed contains cobbles
and small boulders. Piles would need to penetrate the river bottom at least 20 to 30 feet for
providing adequate resistance to buoyancy and sliding. Tree trunk piles would likely splinter
before reaching the desired design depth. As wood decays, it losses strength and cannot resist
the shear stresses created by a sliding ELJ mass. Driving steel piles for pinning the ELJ
structure to the river bottom would be expensive and leave a tangle of steel piles protruding
from the river bottom. Based on the analysis, an ELJ structure 15 feet wide and ballasted with
stone is needed for achieving a minimum sliding factor-of-safety of 2.0, the minimum needed for
unknown flow conditions and resisting expected additional woody debris accumulation.
Each ELJ groin would be 40 feet long and constructed of two 15 feet wide by 20 feet long
modules. Assuming 2 to 3 feet gaps between logs and 8 layers, approximately 50 logs are
needed for each module and 100 for each groin. Based on the stability analysis, 100 cubic
yards of ballast stone is needed for each ELJ groin for achieving minimum sliding and buoyancy
Upper Hoh Road - Bank Failure Risk Reduction Study
p 29
Site C2 – County Milepost 4.4 Bank Stabilization
factor-of-safeties of 2.0, the minimum needed for unknown flow conditions and resisting
expected additional woody debris accumulation. The logs are cabled together for keeping them
in place against expected flow depth and velocity and additional woody debris accumulation.
-Riprap Streambarbs.
Streambarbs are an alternative to using ELJ groins for controlling channel location and reducing
erosive forces (Appendix A, Sheet 10). Each stream barb would be angled upstream 30 degree
relative the bank line and approximately 90 feet long for fitting within the new riparian buffer.
Assuming Class 8 riprap, crest width is 8 feet. Barb thickness is 6 feet at base and 6 feet at tip.
Barb bottom width is 23 feet at base and 23 feet at tip. Approximately 310 cubic yards of riprap
is needed for each stream barb.
Based on review of historical satellite imagery, length of bank typically exposed to impinging
flood flow is estimated to be approximately 150 to 200 feet. The radius of curvature for active
channel is 200 to 500 feet. To effectively deflect the impinging river flow away from the new
bank area, the ELJ groins or stream barbs would need to be spaced every 100 to 150 feet.
Assuming the new bank area is placed over the eroding bank, approximately 350 feet of new
bank area is created and four ELJ groins or stream barbs are needed.
The existing stream bank is assumed left in place. New stream bank area is constructed
between the ELJ groins or stream barbs by placing conserved and imported stream bed and
bank material. Willow and cottonwood trees are planted throughout the area. Willow fascines
are placed along the lower 3 to 6 feet of the bank toe for controlling erosion. Large wood is
incorporated randomly throughout the bank area.
Estimated construction cost is summarized in Table C2-3. Work will be within the active river
channel and requires temporarily diverting the river flow. Flow defection is assumed
accomplished with large sandbags or water-inflated bladders. Dewatering the work area would
be extremely difficult and expensive. Excavation and placing logs, stone, and new stream bank
fill material is assumed to take place in the water ponded behind the flow diversion structure.
Turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a ramp constructed over the existing riprap revetment. The ramp could provide
permanent access for maintenance. Upper Hoh Road traffic impacts are expected to be limited
to one-lane closures and short-term delays.
The HCMZ is narrows at the site relative to upstream and downstream reaches. Consequently,
it is expected that any active channel relocation would likely induce dramatic bank erosion and
stream avulsion, resulting in unnatural changes in the HCMZ boundaries and the likely loss of
private property downstream.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 30
Site C2 – County Milepost 4.4 Bank Stabilization
Major Active River Channel Shift
Shifting the active river channel away from the road eliminates the current road loss risk from
bank erosion occurring between the existing revetments. Shifting the active river channel to
flow across the point bar opposite the existing riprap revetment could be accomplished with four
to six ELJ’s, each at least 20 feet wide and 60 to 100 feet long. All would be constructed within
the active river channel. Top of the ELJ’s are set equal to 100-year water surface, estimated to
be approximately 5 to 6 feet above the point bar surface. Bottom of the ELJ’s are set below the
active channel thalweg elevation and expected scour depth, approximately 6 feet below the
point bar surface. Each engineered-log-jam is ballasted with stone and logs cabled together for
keeping them in place against expected flow depth and velocity and additional woody debris
accumulation.
The existing revetments are assumed left in place. No stream bank area is reconstructed. Off-
channel rearing and resting habitat is created along the toe of the existing road embankment. A
new 100 feet wide active flow channel would be constructed across the point bar for diverting
stream flow away from the construction area. Alluvial and plant materials from the channel
excavation would be used for the habitat reconstruction.
Estimated construction cost is summarized in Table C2-3. Construction requires temporarily
diverting the river flow. Turbidity released is expected to be limited in extent and duration.
Access for construction is assumed down a ramp constructed over the existing road
embankment. The ramp could provide permanent access for maintenance. Upper Hoh Road
traffic impacts are expected to be limited to one-lane closures and short-term delays.
The HCMZ is narrows at the site relative to upstream and downstream reaches. Consequently,
it is expected that any active channel relocation would likely induce dramatic bank erosion and
stream avulsion, resulting in unnatural changes in the HCMZ boundaries and the likely loss of
private property downstream.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Environmental Clearance Considerations
This section of the Upper Hoh Road extends through primarily state trust lands. Designated
critical marbled murrelet critical habitat is located immediately to the north and designated bull
trout critical habitat is in the Hoh River. Designated northern spotted owl critical habitat is
located approximately 3 miles to the east. Individuals of both species may be present in the
forest immediately north of the road at this location. No wetlands were identified on the National
Wetland Inventory Maps. A wetland survey and, if needed, delineation, would need to be
conducted to confirm this negative finding.
Except for as described below, environmental clearance considerations for Site C2 are the
same as described for Site C1.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 31
Site C2 – County Milepost 4.4 Bank Stabilization
Continue Maintenance
Environmental considerations are the same as those described in Site C1.
Relocate Road
The environmental clearance considerations are the same at this site as for Site C1 except for
the fact that the existing riprap revetment would not be removed at this site and, therefore, the
benefit to aquatic species is not as great.
Stabilize Existing Road Embankment
Environmental considerations are the same as those described in Site C1.
Minor and Major Active River Channel Shift
This could have a dramatic effect on the existing river system. The extent to which the option
helps or harms the aquatic habitat would need determined through modeling and formal
consultation with the Service, the Hoh Tribe, and the WDFW. This work would require an
individual permit from the Corps and 401 Certification from the DOE.
A biological assessment would need to be prepared evaluating short and long term impacts to
bull trout and short term construction impacts to the marbled murrelet and the northern spotted
owl.
In addition, geomorphic assessments would need to be conducted for assessing effect this
option may have on downstream properties.
Due to the scope of work and the limited in-water work window, WDFW would likely need to be
petitioned for an extension.
Each ELJ requires a number of trees to be cut down. Approximately 400 and 900 logs are
needed for the minor and major active river channel shift options, respectively. Cutting these
trees would have a direct impact on some forest’s ecosystem and watershed’s health.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 32
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 33
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 34
Photos C2 - CMP 4.4 Bank Stabilization
PHOTO C2-1
PHOTO C2-2
PHOTO C2-3
12/12/2012
Road 15 to 20 feet from erosion scarp.
Soft, fractured silt-stone observed along
bank toe. Finer-grained alluvial material
in upper bank is highly erodible.
Road 8 to 20 feet from erosion scarp.
Vegetation sparse. Point bar deflects
flow towards bank. Bank erosion
nearest road at red flagging.
Typical erosion scarp.
Upstream end of eroding bank - looking
downstream.
Vegetation leaning and bank vertical.
Point bar deflects flow towards bank.
Downstream end of eroding bank -
looking upstream.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 35
Photos C2 - CMP 4.4 Bank Stabilization
PHOTO C2-4
12/12/2012
Typical erosion scarp.
Road 15 to 20 feet from erosion scarp.
Bottom 2 to 3 feet armored with cobble
and small boulder material. Soft,
fractured silt-stone observed along bank
toe. Finer-grained alluvial material in
upper bank is highly erodible.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 36
OP
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Rank ELJ Groins Rank Large Stream barbs Rank
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Construct new stream bank area over unstable and revetment areas.Construct new stream bank area over unstable and revetment areas.Shift active flow channel to flow across point bar away from revetment area.
Ab
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3
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3
Be
t
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h
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i
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,
b
u
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5
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5
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5
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5
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5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.
Ro
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3
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1
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3
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5
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1Requires substantial amount of wood replacement and maintenance.5 Requires moderate level of maintenance.1Requires substantial amount of wood replacement and maintenance.
Im
p
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5
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d
a
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a
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1
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5
No
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x
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a
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d
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5
No
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5
No
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x
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d
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5
No
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x
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d
a
d
d
i
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a
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p
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.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Po
t
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i
a
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o
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d
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1
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j
a
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s
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co
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t
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u
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3
Ad
j
a
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b
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k
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s
i
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w
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co
n
t
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u
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.
3
Ad
j
a
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n
t
b
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k
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w
i
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co
n
t
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u
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.
3
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j
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t
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3
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j
a
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n
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b
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k
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s
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w
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co
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t
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n
u
e
.
3
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j
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co
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t
i
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u
e
.
3 Adjacent bank erosion will continue.3 Adjacent bank erosion will continue.1 Likely increase down stream right bank erosion.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
h
r
e
a
t
e
n
e
d
a
n
d
E
n
d
a
n
g
e
r
e
d
(T
&
E
)
t
e
r
r
e
s
t
r
i
a
l
s
p
e
c
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e
s
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
a
n
d
po
t
e
n
t
i
a
l
l
y
T
&
E
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
&
E
f
i
s
h
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
Ri
p
r
a
p
p
l
a
c
e
d
a
l
o
n
g
b
a
n
k
re
d
u
c
e
s
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
B
a
r
b
s
re
q
u
i
r
e
s
i
g
n
i
f
i
c
a
n
t
e
x
c
a
v
a
t
i
o
n
in
t
o
c
h
a
n
n
e
l
b
e
d
.
3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.
Im
p
a
c
t
t
o
u
p
l
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
W
e
t
l
a
n
d
s
a
n
d
W
a
t
e
r
s
o
f
t
h
e
U
.
S
.
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
Ri
p
r
a
p
p
l
a
c
e
m
e
n
t
i
n
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
B
a
r
b
s
re
q
u
i
r
e
s
i
g
n
i
f
i
c
a
n
t
e
x
c
a
v
a
t
i
o
n
in
t
o
c
h
a
n
n
e
l
b
e
d
.
1 Requires major in stream construction.1 Requires major in stream construction.1 Requires major in stream construction.
Im
p
a
c
t
t
o
D
e
s
i
g
n
a
t
e
d
W
i
l
d
e
r
n
e
s
s
a
r
e
a
(L
e
a
s
t
5
;
m
o
s
t
1
)
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
Ex
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0 No impacts.0 No impacts.0 No expected impacts.
Po
t
e
n
t
i
a
l
f
o
r
H
o
h
R
i
v
e
r
E
n
h
a
n
c
e
m
e
n
t
(G
r
e
a
t
e
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
r
i
v
e
r
en
h
a
n
c
e
m
e
n
t
s
.
5
Pr
o
v
i
d
e
s
o
f
f
-
c
h
a
n
n
e
l
/
s
i
d
e
-
ch
a
n
n
e
l
h
a
b
i
t
a
t
,
a
l
l
o
w
s
r
i
v
e
r
t
o
fu
l
l
y
a
c
c
e
s
s
H
C
M
Z
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Mo
v
e
s
t
h
a
l
w
e
g
a
w
a
y
f
r
o
m
ro
a
d
,
i
m
p
r
o
v
e
s
s
e
d
i
m
e
n
t
tr
a
n
s
p
o
r
t
a
n
d
h
a
b
i
t
a
t
co
m
p le
x
i
t
y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .
Po
t
e
n
t
i
a
l
t
o
m
a
i
n
t
a
i
n
o
r
i
m
p
r
o
v
e
r
i
v
e
r
p
r
o
c
e
s
s
an
d
f
u
n
c
t
i
o
n
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
i
m
p
r
o
v
e
r
i
v
e
r
p
r
o
c
e
s
s
an
d
f
u
n
c
t
i
o
n
.
5
Pr
o
v
i
d
e
s
o
f
f
-
c
h
a
n
n
e
l
/
s
i
d
e
-
ch
a
n
n
e
l
h
a
b
i
t
a
t
,
a
l
l
o
w
s
r
i
v
e
r
t
o
fu
l
l
y
a
c
c
e
s
s
H
C
M
Z
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Mo
v
e
s
t
h
a
l
w
e
g
a
w
a
y
f
r
o
m
ro
a
d
,
i
m
p
r
o
v
e
s
s
e
d
i
m
e
n
t
tr
a
n
s
p
o
r
t
a
n
d
h
a
b
i
t
a
t
co
m
p le
x
i
t
y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .
Po
t
e
n
t
i
a
l
f
o
r
o
t
h
e
r
h
a
b
i
t
a
t
e
n
h
a
n
c
e
m
e
n
t
s
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
o
t
h
e
r
h
a
b
i
t
a
t
en
h
a
n
c
e
m
e
n
t
s
.
5
Op
p
o
r
t
u
n
i
t
y
f
o
r
i
m
p
r
o
v
i
n
g
f
i
s
h
ac
c
e
s
s
t
o
o
f
f
-
c
h
a
n
n
e
l
h
a
b
i
t
a
t
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
o
t
h
e
r
h
a
b
i
t
a
t
en
h
a
n
c
e
m
e
n
t
s
.
5Provides woody debris for habitat complexity and biological processes.3Provides some woody debris for habitat complexity and biological processes.5Provides woody debris for habitat complexity and biological processes.
Po
t
e
n
t
i
a
l
p
r
i
v
a
t
e
p
r
o
p
e
r
t
y
i
m
p
a
c
t
s
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
3Some impacts expected from bank erosion downstream of site. 3Some impacts expected from bank erosion downstream of site. 1 Impacts likely from bank erosion downstream of site.
Sa
f
e
t
y
r
i
s
k
o
f
d
e
s
i
g
n
t
o
p
u
b
l
i
c
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
i
n
c
r
e
a
s
e
i
n
s
a
f
e
t
y
ri
s
k
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
1
Pu
b
l
i
c
c
o
u
l
d
f
a
l
l
d
o
w
n
w
a
l
l
.
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
5
No
e
x
p
e
c
t
e
d
i
n
c
r
e
a
s
e
i
n
s
a
f
e
t
y
ri
s
k
.
1 Boaters could become trapped in ELJ's.3 Boaters could become trapped in root wads.1 Boaters could become trapped in ELJ's.
To
t
a
l
C
o
n
s
t
r
u
c
t
i
o
n
c
o
s
t
N
A
$
1
,
9
0
5
,
6
7
0
$
3
3
8
,
0
9
0
$
4
9
9
,
2
1
4
$
7
6
4
,
6
6
4
$
6
7
3
,
0
8
9
$
1
,
4
5
8
,
3
2
4
$
9
3
6
,
4
2
1
$
2
,
8
2
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37
Date: 3/14/2013
By: S. Leon
Flood
Frequency
(yr)
Exceedance
Probability
Flood
Damage
Average
Flood
Damage
Delta
Exceedance
Probability
Annual Risk
Cost
No damage.2 0.5 $0
$0 0.3 $0
No damage.5 0.2 $0
$150,000 0.1 $15,000
No damage.10 0.1 $300,000
$300,000 0.06 $18,000
Place riprap.25 0.04 $300,000
$300,000 0.02 $6,000
Place riprap.50 0.02 $300,000
$300,000 0.01 $3,000
Place riprap.100 0.01 $300,000
$300,000 0.01 $3,000
0 $300,000
$45,000
$0
Disc. rate, i 0.07125 Serv. life, n 50 CFR 0.0736
$0
Total Expected Cost (Annual)$45,000
Summary
Notes:
1. Method from HEC-17, April 1981.
Table C2-2. Total Expected Cost
Project: Hoh River Road Bank Erosion Risk Study
Site: C2 - CMP 4.4 Bank Stabilization
Alternative: Continue Maintenance
Total Annual Risk Cost
Annualized Capital
Cost
Capital Cost
Annualized Capital Cost
Assume 300 feet ($1k/ft) of revetment repair and bank armoring for each flood damage event.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 38
Table C2-3. Cost Estimates
Site:
Relocate Road
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 95,900$ 95,900$
New Road LF 1,200 500$ 600,000$
Hillside Stabilization LS 1 50,000$ 50,000$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction LF - 1,000$ -$
Streambarbs EA 3 40,000$ 120,000$
ELJ's EA 2 300,000$ 600,000$
Total Construction Cost without Contingencies 1,465,900$
Contingency 30% of construction cost 439,770$
Total Construction Cost 1,905,670$
Compliance 5% of total construction cost 95,284$
Predesign/design (PE)15% of total construction cost 285,851$
Construction Engineering (CE)15% of total construction cost 285,851$
ROW 50,000$
Riprap replacement -20% replacement every 50 years 24,000$
Wood replacement -full log replacement every 30 years 600,000$
TOTAL Capital Cost Cost/Foot 2,706$ 3,246,655$
Annualized Capital Cost Discount rate, i 0.07125 238,977$
Service life, n 50 years
CFR 0.0736071
Complex Roughened Large Rock Toe
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 17,014$ 17,014$
Remove Existing Revetment LF - 200$ -$
Rock H 12 ft T 5 ft CY 778 180$ 140,000$
L 350 ft
Logs L 350 ft XS 8 ft EA 44 2,000$ 87,500$
Soil H 3 ft T 10 ft CY 389 40$ 15,556$
L 350 ft
Total Construction Cost without Contingencies 260,069$
Contingency 30% of construction cost 78,021$
Total Construction Cost 338,090$
Compliance 5% of total construction cost 16,905$
Predesign/design (PE)15% of total construction cost 50,714$
Construction Engineering (CE)15% of total construction cost 50,714$
ROW -$
Riprap replacement -20% replacement every 50 years 28,000$
Wood replacement -full log replacement every 30 years 87,500$
TOTAL Capital Cost Cost/Foot 1,634$ 571,922$
Annualized Capital Cost Discount rate, i 0.07125 42,098$
Service life, n 50 years
CFR 0.0736071
C2 - CMP 4.4 - Bank Stabilization
Upper Hoh Road - Bank Failure Risk Reduction Study
p 39
Table C2-3. Cost Estimates
Complex Log Crib Wall
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 25,122$ 25,122$
Remove Existing Revetment LF 200 200$ 40,000$
Rock H 12 ft T 5 ft CY 778 120$ 93,333$
L 350 ft
Logs L 350 ft H 12 ft EA 105 2,000$ 210,000$
Dia 2 ft Row 6
log l 20 ft No. 105
Piles EA 0 -$ -$
Soil H 3 ft T 10 ft CY 389 40$ 15,556$
L 350 ft
Total Construction Cost without Contingencies 384,011$
Contingency 30% of construction cost 115,203$
Total Construction Cost 499,214$
Compliance 5% of total construction cost 24,961$
Predesign/design (PE)15% of total construction cost 74,882$
Construction Engineering (CE)15% of total construction cost 74,882$
ROW -$
Riprap replacement -20% replacement every 50 years 18,667$
Wood replacement -full log replacement every 30 years 210,000$
TOTAL Capital Cost Cost/Foot 2,579$ 902,606$
Annualized Capital Cost Discount rate, i 0.07125 66,438$
Service life, n 50 years
CFR 0.0736071
Riprap with Roughened Rock Toe, LWD, and Riparian Plantings
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 38,481$ 38,481$
Remove Existing Revetment LF 200 200$ 40,000$
Riprap H 13 ft T 5 ft CY 2,204 180$ 396,667$
L 350 ft SS 2 (h):1(v)
TW 8 ft TT 5 ft
Logs L 350 ft XS 8 ft EA 44 2,000$ 87,500$
Willow 400 sy XS 2 EA 200 10$ 2,000$
Alder 400 sy XS 1 EA 400 20$ 8,000$
Soil H 3 ft T 10 ft CY 389 40$ 15,556$
L 350 ft
Total Construction Cost without Contingencies 588,203$
Contingency 30% of construction cost 176,461$
Total Construction Cost 764,664$
Compliance 5% of total construction cost 38,233$
Predesign/design (PE)15% of total construction cost 114,700$
Construction Engineering (CE)15% of total construction cost 114,700$
ROW -$
Riprap replacement -20% replacement every 50 years 79,333$
Wood replacement -full log replacement every 30 years 87,500$
TOTAL Capital Cost Cost/Foot 3,426$ 1,199,129$
Annualized Capital Cost Discount rate, i 0.07125 88,264$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 40
Table C2-3. Cost Estimates
Riprap with Streambarbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 33,872$ 33,872$
Remove Existing Revetment LF - 200$ -$
Riprap H 13 ft T 5 ft CY 1,685 180$ 303,333$
L 350 ft SS 2 (h):1(v)
TW 0 ft TT 0 ft
Streambarbs EA 3 40,000$ 120,000$
Logs L 350 ft XS 20 ft EA 18 2,000$ 35,000$
Willow 400 sy XS 2 EA 200 10$ 2,000$
Alder 400 sy XS 1 EA 400 20$ 8,000$
Soil H 3 ft T 10 ft CY 389 40$ 15,556$
L 350 ft
Total Construction Cost without Contingencies 517,761$
Contingency 30% of construction cost 155,328$
Total Construction Cost 673,089$
Compliance 5% of total construction cost 33,654$
Predesign/design (PE)15% of total construction cost 100,963$
Construction Engineering (CE)15% of total construction cost 100,963$
ROW -$
Riprap replacement -20% replacement every 50 years 84,667$
Wood replacement -full log replacement every 30 years 35,000$
TOTAL Capital Cost Cost/Foot 2,938$ 1,028,337$
Annualized Capital Cost Discount rate, i 0.07125 75,693$
Service life, n 50 years
CFR 0.0736071
Major River Channel Shift
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 142,100$ 142,100$
Channel Excavation - 100 feet by 5 feet LF 600 300$ 180,000$
Rearing and Resting Habitat Construction AC 1 50,000$ 50,000$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction LF - 1,000$ -$
Streambarbs EA - 40,000$ -$
ELJ's - 20 ft by 60 ft EA 6 300,000$ 1,800,000$
Total Construction Cost without Contingencies 2,172,100$
Contingency 30% of construction cost 651,630$
Total Construction Cost 2,823,730$
Compliance 5% of total construction cost 141,187$
Predesign/design (PE)15% of total construction cost 423,560$
Construction Engineering (CE)15% of total construction cost 423,560$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 1,800,000$
TOTAL Capital Cost Cost/Foot 9,353$ 5,612,036$
Annualized Capital Cost Discount rate, i 0.07125 413,086$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 41
Table C2-3. Cost Estimates
Minor River Channel Shift - ELJ Groins
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 73,388$ 73,388$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 350 1,200$ 420,000$
Large Wood EA 20 1,500$ 30,000$
ELJ groin - 15 ft by 40 ft (2 x 15 ft by 20 ft mod.)EA 4 149,600$ 598,400$
Primary logs 50
Pin logs 4
Ballast stone 50
Cabling 1
74,800$
No. modules/ ELJ groin 2 149,600$
Total Construction Cost without Contingencies 1,121,788$
Contingency 30% of construction cost 336,536$
Total Construction Cost 1,458,324$
Compliance 5% of total construction cost 72,916$
Predesign/design (PE)15% of total construction cost 218,749$
Construction Engineering (CE)15% of total construction cost 218,749$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 598,400$
TOTAL Capital Cost Cost/Foot 4,167$ 2,567,138$
Annualized Capital Cost Discount rate, i 0.07125 188,960$
Service life, n 50 years
CFR 0.0736071
Minor River Channel Shift - Stream Barbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 47,124$ 47,124$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 350 1,200$ 420,000$
Large Wood EA 20 1,500$ 30,000$
Streambarbs Length 90 ft EA 4 55,800$ 223,200$
Crest width 8 ft
Average bot. width 23 ft
Average thickness 6 ft
Volume 310 cy
Cost/cy 180 $/cy Cost/barb 55,800$
Total Construction Cost without Contingencies 720,324$
Contingency 30% of construction cost 216,097$
Total Construction Cost 936,421$
Compliance 5% of total construction cost 46,821$
Predesign/design (PE)15% of total construction cost 140,463$
Construction Engineering (CE)15% of total construction cost 140,463$
ROW -$
Riprap replacement -20% replacement every 50 years 44,640$
Wood replacement -full log replacement every 30 years 30,000$
TOTAL Capital Cost Cost/Foot 2,675$ 1,338,809$
Annualized Capital Cost Discount rate, i 0.07125 98,546$
Service life, n 50 years
CFR 0.0736071
1,000$ 1,000$
1,200$ 4,800$
180$ 9,000$
1,200$ 60,000$
Upper Hoh Road - Bank Failure Risk Reduction Study
p 42
(Page left blank.)
Upper Hoh Road - Bank Failure Risk Reduction Study
p 43
C3 - COUNTY MILEPOST 7.6
TOWER CREEK BRIDGE
Upper Hoh Road - Bank Failure Risk Reduction Study
p 44
Site C3 – Tower Creek Bridge
SITE C3 - TOWER CREEK BRIDGE
Existing Bridge
The existing bridge is a single span decked bulb-tee girder (5 girders) with thrie-beam guardrail
supported on spill-through abutments and founded on pipe piles (4 piles per abutment). The
basic geometry of the existing bridge is approximately 70 feet in length, 30 feet in width and 18
feet vertical clearance from stream bed to bottom of girders (Photo C3-1). In general, the bridge
is in good condition. There are minor spalls on the decked bulb-tee girders.
Main deficiencies include scour at the abutments with exposed piles and erosion at wingwalls
(Photo C3-2). There is significant embankment scour/erosion on the upstream side of west
abutment (Photo C3-6). It was observed that the abutment fills have been scoured or eroded
and replaced with riprap. The existing riprap was installed at a very steep slope (greater than
1:1 slope). Sheet piling was installed behind the west abutment for retaining the approach road
fill. At the wingwalls, it appears that these “elephant-ear” wingwalls were not extended low &
long enough to retain the soil.
The active channel width is approximately 20 feet. Ordinary high water flow depth is
approximately 3 feet. Stream gradient upstream of the bridge is approximately 7 percent.
Stream gradient downstream is approximately 4 percent. Step-pool and cascade are the
dominant bed forms. Cobble and small boulders are the dominant bed material. Estimated 2-
year and 50-year peak discharges are 231 cfs and 484 cfs, respectively (StreamStats). There is
abundant woody debris available for recruitment to the stream from windfall and stream bank
erosion. The stream is capable of transporting the woody debris at the more extreme (> 25-
year) flood events. Based on satellite imagery and field evidence, the stream is subject to
relative frequent debris flows and sediment impulses.
Tower Creek is a tributary of the Hoh River, a braided river with dramatically shifting active
channels. Currently, a main active river channel is 300 feet from the bridge (Fig. C3-1 and
Photo C3-3). Between 1994 and 2009 the active river channel was within 100 feet of the bridge
(Fig. C3-2). Woody debris accumulating on a river point bar beginning in 2006 developed a jam
that eventually deflected the river flow away from the north river bank, cutting in 2011 a new
active channel across the river point bar. The woody debris jam has largely dissipated, leaving
only a small woody debris jam at the head of a small mid-channel gravel bar.
The river channel bottom is lower than the Tower Creek channel bottom. The bottom elevation
of the Tower Creek channel will tend to lower until the channel bottoms are nearly the same
elevation. Typically, incising or degradation occurs as a nick point migrating upstream from the
active river channel edge. A 5-foot high nick point is approximately 80 feet downstream of the
bridge (Photos C3-1 and 3). It was likely initiated in 1994 when the active river channel was
closer to the bridge. The nick point is expected to migrate upstream to the bridge.
The degradation rate is controlled by the elevation differences between stream bottom and river
edge (approximately 8 feet), bed armoring, and an erosion resistant, consolidated alluvial
material observed on the stream banks and bottom (Photos C3-4 to 6). Based on projecting the
downstream channel gradient and adjusting for the relative coarse bed material, stream
degradation at the bridge is not expected to exceed 5 to 6 feet below existing channel bottom
elevation. Total scour (degradation and local scour) is estimated to be 10 feet.
Depth of the piles below stream bottom is not known. The bridge rests on the piles. Piles that
do not extend far enough into the ground could buckle, causing the bridge foundation to fail.
The hardness of the consolidated alluvial material likely prevented the piles being driven to an
Upper Hoh Road - Bank Failure Risk Reduction Study
p 45
Site C3 – Tower Creek Bridge
adequate depth below estimated total scour. The piles depend on the embankment material
around them for support. Scouring of the embankment materials could increase the potential for
the piles to buckle and the bridge foundation to fail. The existing riprap beneath the bridge is
intended to control the scour. The riprap appears properly sized for expected stream flow
velocities, but is overly steep and lacks stabilizing key trenches founded below the estimated
total scour depth (Photos C3-2, 4, 5, 7, 8, and 9). Flood events equal to and larger than the 10-
year would have enough flow depth and velocity to undermine and displace the existing riprap.
To remain effective, the dislodged riprap would need to be repaired or replaced after each major
flood event. Flood events equal to and larger than the 100-year would have enough flow depth
and velocity to significantly displace the riprap and scour the embankment material from around
the piles. Scour from a 100-year flood could also completely undermine the piles. Undermined
or buckled piles would require a complete bridge replacement.
Considered Options
Three options were evaluated for mitigating the expected stream degradation and scour;
continue maintenance, new concrete walls placed under existing bridge, and new bridge. Table
C3-1 presents an evaluation and ranking of the options against design selection criteria.
Continue Maintenance
Riprap will need to be replaced when dislodged from extreme flood flows. Riprap is not easily
countersunk and keyed into the consolidated alluvial material. Width of the existing waterway
does not allow the riprap to be laid back at a stable slope and layer thickness. A moderate to
large debris flow would likely almost completely erode the existing riprap. Replacing riprap as
needed after a flood may not prevent an extreme flood from inducing scour that completely
undermines piles. Placing riprap as an emergency action may be hazardous or difficult. The
emergency-placed riprap may not be effective in controlling the erosion.
A Total Expected Cost analysis (HEC-17, FHWA, April 1981) was completed for estimating total
expected cost repairing damage caused by flooding. The analysis assumes a 50-year service-
life. Based on observed riprap revetment condition, expected flood flow depths, assumed
bridge pile depths, debris flow risk, and scour resistance of the consolidated alluvial material,
the extent of damage varies with flooding magnitude.
Assumed flooding magnitude and damage extent:
10-year – 60 lineal feet new riprap - $60,000.
25-year – 80 lineal feet new riprap - $80,000.
50-year – 160 lineal feet new riprap - $160,000.
100-year – bridge undermined by scour/debris flow - $2,300,000.
500-year – bridge undermined by scour/debris flow - $2,300,000.
Riprap replacement assumes $1,000 per foot. Bridge replacement assumes road is shifted
upstream slightly and includes new road construction costs. Total expected annual cost is
$40,300 (Table C3-2, Total Expected Cost).
New Concrete Walls under Existing Bridge
New concrete walls are proposed for protecting existing bridge from scour. The new concrete
walls are expected to provide at least a 50-year service life, with minimal maintenance. The
remaining service life of the existing bridge is expected to be less than 30 years. Foundation,
structure, deck, and railing elements could be replaced as needed for providing the remaining
Upper Hoh Road - Bank Failure Risk Reduction Study
p 46
Site C3 – Tower Creek Bridge
20 years of service life. The approach is believed not cost-effective. A more cost-effective
approach is to replace the existing bridge with one designed for a full 50-year service-life when
the existing bridge must be replaced. A full replacement costing equivalent to a new 130 feet
bridge is assumed.
Set the bottom of the wall below the expected stream degradation, approximately 6 feet below
the channel thalweg elevation, measured at the downstream bridge face. Set the top of wall 10
feet above channel thalweg elevation, measured at the upstream bridge face. Terminate the
walls into the existing road embankments or stream banks at least 5 feet. Place Class 6 riprap
over the concrete wall footings for controlling local scour. Minimum distance between wall faces
is 45 feet. Total length of wall is estimated to be 160 feet. Estimated construction costs for
excavation, concrete wall, and riprap are summarized in Table C3-3.
New 130 Feet Long Bridge
The new bridge must have an initial waterway that accommodates the expected stream
degradation. Assuming 6 feet of degradation, 1.75(h):1(v) side slopes, and 20 feet active
channel, the initial waterway width is 44 feet. Assuming 16 feet clearance between initial
channel bottom and bridge low chord, 5 feet thick riprap layer, and 1.75(h):1(v) side slopes, the
recommended minimum bridge length is 130 feet.
SPAN ARRANGEMENT: The existing structure is single span, and the proposed structure span
length suits well with a single span deck bulb tee bridge. Thus, only single span arrangement is
considered at this site.
SUPERSTRUCTURE TYPE: Precast prestressed concrete decked bulb tee girders are
appropriate girder types for this stream crossing. The decked bulb tee can be lifted into place by
cranes located on the banks of the channels and eliminating the needs for deck forming, rebar
installation, and concrete casting and curing. Steel girders may also be an effective alternative
at this span length; yet it may require cast-in-place concrete deck, be susceptible to corrosion
and create maintenance problems over the life of the structure. Thus, only precast prestressed
concrete decked bulb tee superstructure is considered at this site.
SUBSTRUCTURE TYPE: Semi-integral abutments supported on deep foundation with
cantilevered wing walls are recommended. This type of construction will eliminate the need for
any expansion joints on the bridge superstructure eliminating water leakage and long term
maintenance associated with expansion joints. Additionally, this type of abutment configuration
will help to eliminate design complexity and the uncertainty of the structure and soil movements.
Based on the existing as-built plans and proposed bridge size, it is most likely that the
foundation type would be pipe pile.
STRUCTURE ALTERNATIVES AND PRELIMINARY COST ESTIMATES: The study evaluated
two structure types for the single span arrangements using precast prestressed concrete deck
bulb girders.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 47
Site C3 – Tower Creek Bridge
Table C3-4. Summary of Bridge Structure Type Alternative
Alt. No. No. of
Spans
Span
Length
Girder
Type
Girder
Spacing
Deck
Thickness
Total
Cost
Cost
per
sft
1 1 130 WASHINGTON
53” - DBT
7’-0” 6” $1,040,000 $220
The single span using Washington 53”-DBT (Deck Bulb-Tee) girders, is the recommended
alternative. This recommended bridge provides the best compromise between structure costs,
constructability and environmental concerns.
Because the abutments are integral with the superstructure, approach slabs are recommended
to ensure ride-ability across the abutments should the approach fill settle. Deck drains are not
anticipated due to the longitudinal slope, crowned deck section, and shoulders. Catch basins
can be installed in the shoulder approach of the bridge to capture pavement runoff flowing
toward the bridge.
Construction Phasing: At this site, a combination of minor shift of alignment, and staged
removal and construction of the existing bridge and proposed bridge respectively may provide
an adequate one-lane temporary traffic during construction. For the purpose of this study, let us
assume that the alignment will be shifted lightly to the south.
The proposed construction phasing for this bridge is described in the following subsections.
Phase 1: Install concrete barrier on the south edge of the third deck bulb tee of the existing
bridge. Set up a one-lane traffic on the existing bridge on the north portion of the existing
bridge. Construct the south portion of the new bridge with three deck bulb tees. Construct the
permanent bridge rail on the south bridge edge, and set a temporary concrete barrier along the
north edge of the bridge. This first south portion of the new bridge may have to have a minimum
width of 20 feet edge to edge to provide a one-lane 10-foot lane with 2-foot shoulders.
Phase 2: Shift traffic onto the completed south portion of the new structure. Remove the
remaining existing bridge. Construct the remaining north portion of the new bridge with two
deck bulb tees.
The estimated construction cost for the new bridge, shifting the road alignment, removing the
existing bridge, and installing riprap abutment scour countermeasures are summarized in Table
C3-3.
Environmental Clearance Considerations
This portion of the road extends through a small parcel of U.S. Forest Service (FS)-managed
lands and privately-held trust lands. The existing Tower Creek Bridge is located on the northern
edge of designated critical habitat for the northern spotted owl. Marbled murrelet critical habitat
is located approximately one mile north of the project in lands managed by the FS. During the
December 2012 field review at least one suitable tree believed to be suitable for marbled
murrelet nesting was identified just west of the bridge on the north side of the road. WDFW
identified Tower Creek as a Priority Habitat area for resident and migratory fish species. The
National Wetland Inventory Maps identified no wetlands adjacent to Tower Creek at this
Upper Hoh Road - Bank Failure Risk Reduction Study
p 48
Site C3 – Tower Creek Bridge
location, though Tower Creek itself is a Water of the US and State. A wetland survey and, if
needed, delineation, would need to be conducted to confirm this negative finding.
Project development should be coordinated with the FS in addition to the other project partners.
Continued Maintenance
This work is likely covered under a Nationwide Permit 3 under the Clean Water Act. There may
be in-water work windows and timing restrictions to avoid adversely impacting the marbled
murrelet, northern spotted owl, and the bull trout.
New Concrete Walls Under Existing Bridge
As described, this alternative will likely require streambed alteration with the placement of riprap
below the ordinary high water mark triggering the need for a Section 404 Permit. Depending on
the extent of work and volume of fill, the work may qualify for a Nationwide Permit 14.
Otherwise, an individual permit will be required.
Further coordination is needed to determine if Tower Creek, being a WDFW Priority habitat, will
warrant the implementation of bioengineering methods to soften the bank stabilization materials.
A biological assessment will need to be prepared to evaluate impacts to marbled murrelet,
northern spotted owl, including designated critical habitat, and bull trout. If no protocol surveys
are done for the marbled murrelet or the northern spotted owl, or if protocol surveys are done
and species presence is confirmed, construction would have to adhere to noise restrictions,
typically no work being permitted 2 hours after sunrise and 2 hours before sunset.
New Bridge
The new bridge as described will require minor realignment to allow for maintenance of single-
lane traffic during construction. This minor realignment shift will result in vegetation clearing.
The present anticipated shift to the south would result in vegetation clearing of designated
critical habitat for the northern spotted owl. It could also impact suitable nesting, roosting,
foraging, and dispersal habitat for the marbled murrelet. Also, the proposed construction may
generate noise that could adversely affect these bird species as they nest, roost, and forage.
As a result, a biological assessment will need to be prepared to analyze these effects and
determine if there will be a take of any individuals of these species.
The installation of the new bridge and associated rip-rap will require in-water work, thereby
potentially impacting the bull trout. As a result, a biological assessment will need to be prepared
to analyze these effects. Also, this work will trigger the need to acquire a Section 404 permit
and 401 Certification.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 49
ea
g
v
d
a
f
av
d
f
v
AC
M
Z
‐
Ac
t
i
v
e
Ch
a
n
n
e
l
Mi
g
r
a
t
i
o
n
Zo
n
e
,
Ge
o
m
o
r
p
h
i
c
As
s
e
s
s
m
e
n
t
of
Ho
h
Ri
v
e
r
in
Wa
s
h
i
n
g
t
o
n
St
a
t
e
,
US
B
R
,
Ju
l
y
20
0
4
.
Im
a
g
e
r
y
da
t
e
11
/
3
/
2
0
1
1
Fi
g
u
r
e
C3
‐1.
Si
t
e
Lo
c
a
t
i
o
n
19
9
4
Ac
t
i
v
e
Ch
a
n
n
e
l
Li
m
i
t
AC
M
Z
Upper Hoh Road - Bank Failure Risk Reduction Study
p 50
ea
g
v
d
a
f
av
d
f
v
Fi
g
u
r
e
C3
‐2.
Hi
s
t
o
r
i
c
a
l
Sa
t
e
l
l
i
t
e
Im
a
g
e
r
y
19
9
4
20
1
1
20
0
9
20
0
6
Upper Hoh Road - Bank Failure Risk Reduction Study
p 51
Photos C3 - Tower Creek Bridge
PHOTO C3- 1
PHOTO C3- 2
PHOTO C3- 3
12/12/2012
Nick point approximately 4 to 5 feet high
and consisting of woody debris and
cobbles/boulders. Stream bed is cobble-
boulder dominated. Active river channel
is approx. 300 feet away from bridge.
Riprap setting on consolidated alluvial
material. Stream bed is cobble-boulder
dominated. Upstream channel has
abundant large woody debris.
Looking downstream over nick point
towards confluence with river.
Looking upstream at nick point and
bridge.
Nick point approximately 4 to 5 feet high
and consisting of woody debris and
cobbles/boulders. Stream bed is cobble-
boulder dominated.
Looking upstream at bridge.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 52
Photos C3 - Tower Creek Bridge
PHOTO C3- 4
PHOTO C3- 5
PHOTO C3- 6
12/12/2012
Bank is vertical and prone to erosion.
Woody debris deflects stream flow
towards bank. Consolidated alluvial
material is exposed on stream bed and
dark green vertical bank area in center of
photo.
East abutment riprap scour
countermeasure.
Riprap setting on consolidated alluvial
material, which is exposed across stream
bed. Channel incised into material
approx. 3 to 4 feet.
East abutment riprap scour
countermeasure and consolidated
alluvial material.
Riprap setting on consolidated alluvial
material, which is exposed across stream
bed. Channel incised into material
approx. 3 to 4 feet. Consolidated alluvial
material is firm, difficult to pick or scratch
with rock hammer, and is likely retards
erosion.
Upstream west abutment.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 53
Photos C3 - Tower Creek Bridge
PHOTO C3- 7
PHOTO C3- 8
PHOTO C3- 9
12/12/2012
Bank reasonably well protected from
erosion by riprap.
Downstream west abutment.
Bank reasonably well protected from
erosion by riprap.
Upstream east abutment.
Downstream east abutment.
Bank reasonably well protected from
erosion by riprap. Woody debris deflects
stream flow towards bank.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 54
OP
T
I
O
N
S
Ra
n
k
Co
n
t
i
n
u
e
d
M
a
i
n
t
e
n
a
n
c
e
Ra
n
k
Co
n
c
re
t
e
W
a
l
l
u
n
d
e
r
B
r
i
d
g
e
Rank Replace Bridge
Re
p
l
a
c
e
r
i
p
r
a
p
w
h
e
n
d
i
s
l
o
d
g
e
d
f
r
o
m
e
x
t
r
e
m
e
fl
o
o
d
f
l
o
w
s
.
In
s
t
a
l
l
n
e
w
w
a
l
l
i
n
f
r
o
n
t
o
f
e
x
i
s
t
i
n
g
a
b
u
t
m
e
n
t
s
-
ex
i
s
t
i
n
g
b
r
i
d
g
e
r
e
m
a
i
n
s
i
n
p
l
a
c
e
.
Replace bridge with new 130 feet long bridge - requires new road alignment immediately upstream of existing bridge.
Ab
i
l
i
t
y
t
o
p
r
e
s
e
r
v
e
a
n
d
o
p
e
r
a
t
e
t
h
e
r
o
a
d
w
a
y
i
n
a
sp
e
c
i
f
i
c
l
o
c
a
t
i
o
n
(M
o
s
t
a
b
l
e
5
,
l
e
a
s
t
a
b
l
e
1
)
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
u
n
d
e
r
m
i
n
e
f
o
o
t
i
n
g
s
.
3
Mo
d
e
r
a
t
e
r
e
d
u
c
t
i
o
n
i
n
s
c
o
u
r
r
i
s
k
.
A
t
l
e
a
s
t
5
0
-
y
e
a
r
se
r
v
i
c
e
-
l
i
f
e
.
5 Mitigates scour risk. At least 50-year service-life.
Ro
a
d
w
a
y
s
u
s
t
a
i
n
a
b
i
l
i
t
y
(
l
i
f
e
o
f
s
o
l
u
t
i
o
n
)
(L
o
n
g
e
s
t
5
,
s
h
o
r
t
e
s
t
1
)
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
u
n
d
e
r
m
i
n
e
f
o
o
t
i
n
g
s
.
3
Mo
d
e
r
a
t
e
r
e
d
u
c
t
i
o
n
i
n
s
c
o
u
r
r
i
s
k
.
A
t
l
e
a
s
t
5
0
-
y
e
a
r
se
r
v
i
c
e
-
l
i
f
e
.
5 Mitigates scour risk. At least 50-year service-life.
Im
p
a
c
t
t
o
h
i
l
l
s
i
d
e
s
t
a
b
i
l
i
t
y
a
d
j
a
c
e
n
t
t
o
s
i
t
e
(M
o
s
t
l
i
k
e
l
y
1
;
l
e
a
s
t
l
i
k
e
l
y
5
)
1
No
i
m
p
a
c
t
t
o
g
e
o
l
o
g
i
c
a
l
s
t
a
b
i
l
i
t
y
.
1
No
i
m
p
a
c
t
t
o
g
e
o
l
o
g
i
c
a
l
s
t
a
b
i
l
i
t
y
.
3 Shift in road alignment to construct new bridge may induce hillside instability.
Po
t
e
n
t
i
a
l
t
o
r
e
d
u
c
e
e
r
o
s
i
o
n
o
f
b
a
n
k
s
a
d
j
a
c
e
n
t
t
o
s
i
t
e
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
i
n
c
r
e
a
s
e
b
a
n
k
e
r
o
s
i
o
n
.
3
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
i
n
c
r
e
a
s
e
b
a
n
k
e
r
o
s
i
o
n
.
5 Channel not constrained.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
h
r
e
a
t
e
n
e
d
a
n
d
E
n
d
a
n
g
e
r
e
d
(
T
&
E
)
te
r
r
e
s
t
r
i
a
l
s
p
e
c
i
e
s
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
.
3
No
p
e
r
m
a
n
e
n
t
i
m
p
a
c
t
s
,
t
e
m
p
o
r
a
r
y
c
o
n
s
t
r
u
c
t
i
o
n
im
p
a
c
t
s
.
1Likely adverse modification of suitable marbled murrelet habitat and temporary construction impacts.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
&
E
f
i
s
h
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
,
a
s
s
u
m
i
n
g
n
o
r
o
a
d
o
r
b
r
i
d
g
e
f
a
i
l
u
r
e
.
3
No
n
e
e
x
p
e
c
t
e
d
.
3 None expected.
Im
p
a
c
t
t
o
u
p
l
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
.
1 Realignment results in upland habitat loss.
Im
p
a
c
t
s
t
o
W
e
t
l
a
n
d
s
a
n
d
W
a
t
e
r
s
o
f
t
h
e
U
.
S
.
(L
e
a
s
t
5
;
m
o
s
t
1
)
1
Ri
p
r
a
p
f
i
l
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ri
p
r
a
p
f
i
l
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
-
c
h
a
n
n
e
l
l
e
s
s
co
n
s
t
r
a
i
n
e
d
.
5 Riprap fill placed in channel - channel not constrained.
Im
p
a
c
t
t
o
D
e
s
i
g
n
a
t
e
d
W
i
l
d
e
r
n
e
s
s
a
r
e
a
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
.
5 None expected.
Po
t
e
n
t
i
a
l
f
o
r
H
o
h
R
i
v
e
r
E
n
h
a
n
c
e
m
e
n
t
(G
r
e
a
t
e
s
t
5
;
L
e
a
s
t
1
)
5
Fi
s
h
a
c
c
e
s
s
t
o
o
f
f
-
c
h
a
n
n
e
l
h
a
b
i
t
a
t
n
o
t
r
e
d
u
c
e
d
o
f
in
c
r
e
a
s
e
d
.
5
Fi
s
h
a
c
c
e
s
s
t
o
o
f
f
-
c
h
a
n
n
e
l
h
a
b
i
t
a
t
n
o
t
r
e
d
u
c
e
d
o
f
in
c
r
e
a
s
e
d
.
5 Fish access to off-channel habitat not reduced of increased.
Po
t
e
n
t
i
a
l
t
o
m
a
i
n
t
a
i
n
o
r
i
m
p
r
o
v
e
r
i
v
e
r
p
r
o
c
e
s
s
a
n
d
f un
c
ti
o
n
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
3
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
5 Channel not constrained.
Po
t
e
n
t
i
a
l
f
o
r
o
t
h
e
r
h
a
b
i
t
a
t
e
n
h
a
n
c
e
m
e
n
t
s
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
3
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
5 Channel not constrained - debris transported through site.
Po
t
e
n
t
i
a
l
p
r
i
v
a
t
e
p
r
o
p
e
r
t
y
i
m
p
a
c
t
s
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
.
1 Shift in road alignment to construct new bridge may require ROW.
Sa
f
e
t
y
r
i
s
k
o
f
d
e
s
i
g
n
t
o
p
u
b
l
i
c
(L
e
a
s
t
5
;
M
o
s
t
1
)
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
u
n
d
e
r
m
i
n
e
f
o
o
t
i
n
g
s
.
3
Mo
d
e
r
a
t
e
r
e
d
u
c
t
i
o
n
i
n
s
c
o
u
r
r
i
s
k
.
5 Mitigates scour risk.
To
t
a
l
C
o
n
s
t
r
u
c
t
i
o
n
c
o
s
t
NA
$7
8
2
,
8
7
5
$2,342,444
To
t
a
l
C
a
p
i
t
a
l
C
o
s
t
(
5
0
y
e
a
r
s
)
NA
$4
,
2
3
9
,
1
8
1
$3,182,299
An
n
u
a
l
i
z
e
d
T
o
t
a
l
C
a
p
i
t
a
l
C
o
s
t
(
L
e
a
s
t
5
;
M
o
s
t
1
)
$4
0
,
3
0
0
$3
1
2
,
0
3
4
$234,240
S C O R E4 35
06 0
51
1
Ta
b
l
e
C
3
-
1
.
A
l
t
e
r
n
a
t
i
v
e
S
u
m
m
a
r
y
a
n
d
R
a
n
k
i
n
g
.
Up
p
e
r
H
o
h
R
i
v
e
r
R
o
a
d
S
i
t
e
-
C
3
-
T
o
w
e
r
C
r
e
e
k
B
r
i
d
g
e
Up
p
e
r
Ho
h
Ro
a
d
-
Ba
n
k
Fa
i
l
u
r
e
Ri
s
k
Re
d
u
c
t
i
o
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Date: 3/14/2013
By: S. Leon
Flood
Frequency
(yr)
Exceedance
Probability
Flood
Damage
Average
Flood
Damage
Delta
Exceedance
Probability
Annual Risk
Cost
No damage.2 0.5 $0
$0 0.3 $0
No damage.5 0.2 $0
$30,000 0.1 $3,000
Revetment damaged.10 0.1 $60,000
$70,000 0.06 $4,200
Revetment damaged.25 0.04 $80,000
$120,000 0.02 $2,400
Revetment damaged.50 0.02 $160,000
$1,230,000 0.01 $12,300
Replace bridge.100 0.01 $2,300,000
$2,300,000 0.008 $18,400
Replace bridge.500 0.002 $2,300,000
$40,300
$0
Disc. rate, i 0.07125 Serv. life, n 50 CFR 0.0736
$0
Total Expected Cost (Annual)$40,300
Summary
Notes:
1. Method from HEC-17, April 1981.
Table C3-2. Total Expected Cost
Project: Hoh River Road Bank Erosion Risk Study
Site: C3 - Tower Creek Bridge
Alternative: Continue Maintenance
Total Annual Risk Cost
Annualized Capital
Cost
Capital Cost
Annualized Capital Cost
Assume bridge is replaced for 100-year and larger flood events.
Upper Hoh Road - Bank Failure Risk Reduction Study
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Table C3-3. Cost Estimate
Site:
130 Feet Long Bridge
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 117,880$ 117,880$
New Road LF 400 500$ 200,000$
Hillside Stabilization LS 1 30,000$ 30,000$
Flow Diversion LS 1 20,000$ 20,000$
Remove Existing Bridge LS 1 250,000$ 250,000$
130 feet Bridge LS 1 1,040,000$ 1,040,000$
Riprap H 12 ft T 5 ft CY 800 180$ 144,000$
L 160 ft SS 1.75 (h):1(v)
TW 6 ft TT 5 ft
Total Construction Cost without Contingencies 1,801,880$
Contingency 30% of construction cost 540,564$
Total Construction Cost 2,342,444$
Compliance 5% of total construction cost 117,122$
Predesign/design (PE)15% of total construction cost 351,367$
Construction Engineering (CE)15% of total construction cost 351,367$
ROW 20,000$
TOTAL Capital Cost Cost/Foot 7,956$ 3,182,299$
Annualized Capital Cost Discount rate, i 0.07125 234,240$
Service life, n 50 years
CFR 0.0736071
Concrete Wall Under Existing Bridge
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 39,397$ 39,397$
Flow Diversion LS 1 20,000$ 20,000$
Exc. H 6 ft T 14 ft CY 498 200$ 99,556$
L 160 ft
Wall H 16 ft T 2 ft CY 190 2,000$ 379,259$
L 160 ft
Riprap H 6 ft T 10 ft CY 356 180$ 64,000$
L 160 ft
Total Construction Cost without Contingencies 602,212$
Contingency 30% of construction cost 180,664$
Total Construction Cost 782,875$
Compliance 5% of total construction cost 39,144$
Predesign/design (PE)15% of total construction cost 117,431$
Construction Engineering (CE)15% of total construction cost 117,431$
ROW -$
New 130 feet bridge to replace existing bridge after remaining 30-year service life is over.3,182,299$
TOTAL Capital Cost Cost/Foot 26,495$ 4,239,181$
Annualized Capital Cost Discount rate, i 0.07125 312,034$
Service life, n 50 years
CFR 0.0736071
C3 - Tower Creek Bridge
Upper Hoh Road - Bank Failure Risk Reduction Study
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C4 - COUNTY MILEPOST 7.8
BANK STABILIZATION
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
SITE C4 – COUNTY MILEPOST 7.8 BANK STABILIZATION
Site Conditions
The site parallels the outside bank of a river bend (Fig. C4-1). Approximately 1,300 lineal feet of
riprap revetment along the apex of the river bend appears to be effectively controlling road
embankment erosion (Photo C4-1). The 2 to 4 feet diameter riprap comprising the revetment is
generally properly graded and placed. The upstream 800 feet long segment, installed in 2007,
has a 1.75(h):1(v) finished surface slope and appears stable. The downstream 500 feet long
segment, installed in 2004, has a 1.5(h):1(v) steeper finished surface slope and appears less
stable (Fig. C4-1, C4b). Some riprap has been dislodged from toe and mid slope areas. The
segment is at the maximum point of stream bank curvature and likely experiences high shear
stress when floods occur. Continued riprap loss could result in dismantling of the revetment and
damage to the road. Based on current channel alignment and expected limited channel
alignment shifts, the risk of a catastrophic road embankment failure is low. Water depth at
typically normal annual low flow conditions is estimated to be 4 to 6 feet.
Toe erosion and undermining of the stream bank continues immediately upstream and
downstream of the riprap revetment (Photos C4-2 and 6). At the upstream location, C4c, the
stream bank toe is approximately 50 feet away and 20 feet below the road surface. Cobbles
and small boulders naturally armoring the toe and large trees growing in the stream bank have
inhibited the bank erosion. A mid-channel gravel bar approximately 50 feet away from and
paralleling the stream bank deflects stream flow towards the bank, aggravating the bank
erosion. Continued stream bank erosion could undermine the road. Based on current channel
alignment and expected limited channel alignment shifts, the risk of a catastrophic road
embankment failure is moderate. Water depth at typically normal annual low flow conditions is
estimated to be 4 to 5 feet.
At the downstream location, C4a, the stream bank toe is approximately 50 feet away and 20
feet below the road surface. Cobbles and small boulders naturally armoring the toe and large
trees growing in the stream bank have inhibited the bank erosion (Photos C4-5 and 6).
Currently, the downstream stream bank toe is separated from the active river channel by a
gravel bar (Photos C4-3 to 5). The gravel bar is expected to be completely exposed at typically
normal annual low flow conditions. Woody debris will likely continue to accumulate on the
existing small woody debris jam at the head of the small mid-channel gravel bar (Photos C4-3 to
5). A woody debris jam not completely plugging the 150 feet wide side channel between the
small mid-channel gravel bar and stream bank could deflect river flow directly at the stream
bank, accelerating the bank erosion and undermining the road. Based on the amount and size
of wood available in the river for transport and the width of the side channel, the risk of a woody
debris jam building that only partially blocks the side channel is high. With a partial blocking of
the side channel, the risk of a catastrophic road embankment failure is high.
The Hoh River is a braided river with dramatically shifting active channels. Between 1994 and
2009 the active river channel flowed along the north bank (Fig. C4-2). Woody debris
accumulating on a river point bar beginning in 2006 developed a jam that eventually deflected
the river flow away from the north river bank, cutting in 2011 a new active channel across a river
point bar. The woody debris jam has largely dissipated, leaving only a small woody debris jam
at the head of a small mid-channel gravel bar.
An erosion resistant poorly consolidated alluvium terrace deposit has limited river bend
migration to the north. The terrace deposit represents the historical channel migration zone
(HCMZ) right (looking downstream) boundary. Width of the HCMZ is approximately 2,500 feet.
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
The road embankment coincides with the HCMZ right boundary. Wetlands between the terrace
toe and existing road have been established due to drainage off the hillside. Terrace deposits
have also limited active channel migration to the south. Terrace deposits and Tower Creek
debris flow and alluvial material have restricted down-valley migration of the meander bend.
Considered Options
Continuing maintenance, relocating the road, installing additional bank stabilization, minor active
river channel shift, and major active river channel shift were considered. Table C4-1 presents
an evaluation and ranking of the options against design selection criteria.
Riprap is expected to be lost during extreme flooding, requiring replenishment for maintaining
the riprap installation’s effectiveness. Total Capital and Annualized Total Capital Costs provided
in Table C4-1 assume 20 percent of the riprap in an installation is replaced every 50 years.
Douglas fir and hemlock are the most commonly available logs in the area. Douglas-fir logs can
remain durable in wetting-drying conditions for 25 to 60 years (Tech. Supp. 14J, Use of Large
Woody Material for Habitat and Bank Protection, Part 654, National Engineering Handbook,
USDA, Natural Resources Conservation Service). Hemlock is the least durable of the conifers.
Because the tree quality and species to be used in the structures is not known, Total Capital
and Annualized Total Capital Costs provided in Table C4-1 assume wood used in the
alternatives is replaced every 30 years.
Continue Maintenance
Continued maintenance involves monitoring the riprap revetment and upstream/downstream
stream bank areas for excessive riprap loss and bank erosion, respectively. Riprap will need to
be replaced when dislodged from extreme flood flows. Stream bank toe erosion upstream and
downstream of the existing riprap revetments could progress to the point that undermining of the
road is imminent. Continued maintenance is placing riprap in an emergency action or after
flooding as needed for preventing a road closure. Placing riprap as an emergency action may
be hazardous or difficult. The emergency-placed riprap may not be effective in controlling the
erosion.
A Total Expected Cost analysis (HEC-17, FHWA, April 1981) was used for estimating total
expected cost repairing flood-induced road damage over a 50-year service-life. Based on
observed riprap revetment condition, proximity of channel to roadway, and amount of natural
bank armoring, the analysis assumes damage requiring repair of the existing revetments or
addition of new riprap revetment placed as an emergency action for stabilizing an eroding river
bank occurs for flood events equal to and larger than the 25-year flood event. Based on review
of historical satellite imagery, length of bank typically exposed to impinging flood flow is
estimated to be approximately 300 feet. Based on vegetation distribution and age and
estimated riprap placement sequencing, the length of past revetment installations ranged from
500 to 800 feet. Assuming 300 feet total for each flood damage event and a cost of $1,000 per
foot, the total expected annual cost is $21,000 (Table C4-2, Total Expected Cost).
Relocate Road
Shifting the road away from the river eliminates the current riprap revetment failure risk and road
loss risk from bank erosion occurring upstream and downstream of the existing revetment. The
alternative involves shifting the road 100 to 150 feet north to parallel the valley edge along the
toe of a 260 feet high terrace. Length of reroute is 2,000 feet and extends from the existing
Tower Creek Bridge to a point on the existing road that is outside of the HCMZ.
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
Connecting the new alignment to the existing bridge would make the road turn sharply. It would
require the posted speed for this location to be reduced. To correct this problem, the Tower
Creek Bridge would need to be rebuilt about 100 feet north of the existing one. The option
assumes that the new road alignment connects to the existing bridge.
Existing riprap revetment is removed and approximately 80 to 100 feet wide by 1,800 feet long
area of the stream bank is reconstructed. An erodible newly reconstructed stream bank would
allow lateral bank erosion and migration to the north. Streambarbs constructed from the
existing revetment riprap, engineered-log-jams (ELJ’s), and planted vegetation control the bank
erosion and lateral migration and preserve a riparian buffer between the active river channel
and road embankment.
Rerouting the road requires construction in the wetlands established between the terrace toe
and existing road. Constructing new wetlands and off-channel rearing and resting habitat within
the existing road prism would not fully mitigate the area of wetlands lost realigning the road.
Slumping observed on the terrace slope suggests the terrace slope is not geotechnically stable.
A new road alignment located at the terrace toe would likely experience landslides and debris
flows that could potentially bury the road with debris. Keeping the road away from terrace toe
and elevating it as much as possible would reduce the severity and frequency of landslide-
induced damage. The alternative requires monitoring and repair of the streambarbs and ELJ’s
to remain effective in controlling the bank erosion and lateral migration.
Estimated construction cost for the 2,000 feet of new road, existing road removal, 10
streambarbs, 5 ELJ’s, and stream bank reconstruction is summarized in Table C4-3.
Construction is expected to occur outside the active flow channel. Turbidity released is
expected to be limited in extent and duration. Access for construction is assumed from the
existing road. Constructing the new road alignment first and then switching the Upper Hoh
Road traffic over before removing the existing road reduces traffic impacts to one-lane closures
and short-term delays.
Stabilize Existing Road Embankment
Approximately 100 feet of upstream stream bank (C4c), 200 feet of downstream stream bank
(C4a), and 500 feet of the revetment (C4b) are proposed for stabilization.
Alternatives evaluated;
Complex roughened large rock toe.
Complex log crib wall.
Riprap with roughened rock toe, LWD, and riparian plantings.
Riprap with streambarbs.
Based on field evidence, the sites are expected to experience high shear stress, 10 to 14 feet
deep flood flows, and abundant floating debris. It is critical that the stabilization methods be
properly designed and anchored for maintaining effectiveness and surviving the expected flood
conditions.
Construction for all the alternatives is expected to occur entirely within the active flow channel
and requires excavating into the streambed and stream bank. Stream work would be
accomplished in flowing water. Assuming the work is completed during low flow periods,
turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a temporary access route built of riprap and logs. The access route would be
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
removed after construction is completed. Upper Hoh Road traffic impacts are expected to be
limited to one-lane closures and short-term delays.
-Complex roughened large rock toe (Appendix A, Sheet 4).
The approach involves placing a rock toe between the expected scour depth and ordinary high
water level, approximately 10 to 12 feet high and 5 feet thick. Log bundles spaced 6 to 10 feet
are placed at the bottom of the rock toe. Soil placed above the rock toe in overlapping layers of
erosion control blanket, approximately 6 to 12 feet. The rock toe and soil ballast the logs and
reduce the risk of the logs floating away. Estimated construction cost for the complex
roughened large rock toe is summarized in Table C4-3.
-Complex log crib wall (Appendix A, Sheet 5).
The approach involves placing a log crib wall made of rough logs between the expected scour
depth and ordinary high water level, approximately 10 to 12 feet high. Stone is placed within the
log crib wall for ballast. Logs with attached root wads extending into the stream bank provide
roughness and additional wall stability. All logs are cabled together for enhancing stability.
Designs typically include piles driven to refusal or minimum depth of 10 feet. The cobble and
boulder stream bed material will likely prevent the piles from being cost-effectively driven or
excavated. They are assumed eliminated in the proposed design. Approximately 6 to 12 feet of
soil is placed above the crib wall and planted. Estimated construction cost for the complex log
crib wall is summarized in Table C4-3.
-Riprap with Roughened Rock Toe, LWD, and Riparian Plantings (Appendix A, Sheet 9).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
A launchable riprap toe 8 feet wide and 5 feet thick reduces the risk of scour and channel
incision undermining the revetment and provides additional stability. Logs or log bundles
spaced 6 to 10 feet are placed along the revetment toe for providing roughness and channel
complexity. The logs are buried in the road embankment for reducing the risk of them floating
away. Willow and alder are planted throughout the revetment and bank area above the
revetment. Estimated construction cost is summarized in Table C4-3.
-Riprap with Streambarbs (Appendix A, Sheet 11).
The approach involves placing a riprap revetment between the expected scour depth and 50-
year flood event water level, approximately 12 to 15 feet high, 5 feet thick, and 2(h):1(v) slope.
Instead of a launchable riprap toe, 6 to 8 - 40 to 50 feet long streambarbs are proposed for
reducing shear stress and deflecting the river flow away from the revetment. The streambarbs
reduce the risk of scour and channel incision undermining the revetment, promote sediment
deposition and retention along the bank toe, and creates channel complexity. The bank, riprap,
streambarbs, and channel area between the streambarbs would be augmented with streambed
material, large woody debris, and planted with riparian vegetation for establishing a riparian
buffer. Estimated construction cost is summarized in Table C4-3.
Minor Active River Channel Shift
An environmentally desirable approach would be to nudge the active river channel over enough
from the road to reestablish a riparian buffer. Ideally, the buffer would have the same erosion
resistance of a natural, wooded and vegetated river bank. The buffer would need to be wide
enough to allow some bank erosion without threatening the roadway. It would be made by
placing alluvial material over existing riprap revetment and unstable bank areas. To promote
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
vegetation establishment and soil mass stability, the finished surface of the buffer area should
not be steeper than 5(h):1(v). Assuming a 10 feet high bank, the width of the new buffer area
would be at least 50 feet. Existing relative stable riparian buffers observed along the river are at
least 40 to 50 feet wide and densely vegetated with alder and fir. The new buffer area would be
prone to erosion from active channel migration. The erosive forces are expected to be too large
for passive and bio-engineering methods to be effective by themselves. Hardened, more
erosion resistant components in the buffer system are needed for mitigating the erosive forces.
-Engineered-log-jam Groins.
ELJ’s groins constructed perpendicular to the stream bank and extending through the new
buffer area would control channel location and deflect river flow away from new buffer area
(Appendix A, Sheet 10). An ELJ’s buoyancy and sliding analysis (Design Guidelines for
Reintroducing Wood in Australian Streams, Abbe/Brooks, 2006) was completed assuming 6 feet
design flow depth, 5 feet design scour depth, 8 feet per second average flow velocity, 1.5
velocity correction factor, and 18-inch average trunk diameter. The river bed contains cobbles
and small boulders. Piles would need to penetrate the river bottom at least 20 to 30 feet for
providing adequate resistance to buoyancy and sliding. Tree trunk piles would likely splinter
before reaching the desired design depth. As wood decays, it losses strength and cannot resist
the shear stresses created by a sliding ELJ mass. Driving steel piles for pinning the ELJ
structure to the river bottom would be expensive and leave a tangle of steel piles protruding
from the river bottom. Based on the analysis, an ELJ structure 15 feet wide and ballasted with
stone is needed for achieving a minimum sliding factor-of-safety of 2.0, the minimum needed for
unknown flow conditions and resisting expected additional woody debris accumulation.
Each ELJ groin would be 60 feet long and constructed of three 15 feet wide by 20 feet long
modules. Assuming 2 to 3 feet gaps between logs and 8 layers, approximately 50 logs are
needed for each module and 150 for each groin. Based on the stability analysis, 150 cubic
yards of ballast stone is needed for each ELJ groin for achieving minimum sliding and buoyancy
factor-of-safeties of 2.0, the minimum needed for unknown flow conditions and resisting
expected additional woody debris accumulation. The logs are cabled together for keeping them
in place against expected flow depth and velocity and additional woody debris accumulation.
-Riprap Streambarbs.
Streambarbs are an alternative to using ELJ groins for controlling channel location and reducing
erosive forces (Appendix A, Sheet 10). Each stream barb would be angled upstream 30 degree
relative the bank line and approximately 100 feet long for fitting within the new riparian buffer.
Assuming Class 8 riprap, crest width is 8 feet. Barb thickness is 8 feet at base and 6 feet at tip.
Barb bottom width is 32 feet at base and 23 feet at tip. Approximately 470 cubic yards of riprap
is needed for each stream barb.
Based on review of historical satellite imagery, length of bank typically exposed to impinging
flood flow is estimated to be approximately 300 feet. The radius of curvature for active channel
is 500 to 800 feet. To effectively deflect the impinging river flow away from the new bank area,
the ELJ groins or stream barbs would need to be spaced every 100 to 150 feet. Assuming 100
feet of upstream stream bank (C4c), 200 feet of downstream stream bank (C4a), and 1,300 feet
of the revetment is proposed for covering and stabilization, approximately 13 ELJ groins or
stream barbs are needed.
The existing revetment is assumed left in place. Stream bank area is constructed between the
ELJ groins or stream barbs by placing conserved and imported stream bed and bank material.
Willow and cottonwood trees are planted throughout the area. Willow fascines are placed along
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
the lower 3 to 6 feet of the bank toe for controlling erosion. Large wood is incorporated
randomly throughout the bank area.
Estimated construction cost is summarized in Table C4-3. Work will be within the active river
channel and requires temporarily diverting the river flow. Flow defection is assumed
accomplished with large sandbags or water-inflated bladders. Dewatering the work area would
be extremely difficult and expensive. Excavation and placing logs, stone, and new stream bank
fill material is assumed to take place in the water ponded behind the flow diversion structure.
Turbidity released is expected to be limited in extent and duration. Access for construction is
assumed down a ramp constructed over the existing riprap revetment. The ramp could provide
permanent access for maintenance. Upper Hoh Road traffic impacts are expected to be limited
to one-lane closures and short-term delays.
Shifting the active river channel 50 feet south is expected to induce moderate erosion of the
point bar erosion opposite the site. It also increases the risk of an avulsion across the point
bars opposite and immediately downstream of the site. The approach would likely induce minor
downstream bank erosion.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Major Active River Channel Shift
Shifting the river 200 to 400 feet away from the road eliminates the current riprap revetment
failure risk and road loss risk from bank erosion occurring upstream and downstream of the
existing revetment. Shifting the active river channel to flow across the point bar opposite the
existing riprap revetment could be accomplished with four to six ELJ’s, each at least 20 feet
wide and 60 to 100 feet long. Three of the ELJ’s would be constructed within the active river
channel and two would be constructed within the point bar. Top of the ELJ’s are set equal to
100-year water surface, estimated to be approximately 5 to 6 feet above the point bar surface.
Bottom of the ELJ’s are set below the active channel thalweg elevation and expected scour
depth, approximately 6 feet below the point bar surface. Each engineered-log-jam is ballasted
with stone and logs cabled together for keeping them in place against expected flow depth and
velocity and additional woody debris accumulation.
The existing revetment is assumed left in place. Off-channel rearing and resting habitat is
created along the toe of the existing riprap revetment. A new 100 feet wide active flow channel
would be constructed across the point bar for diverting stream flow away from the construction
area. Alluvial and plant materials from the channel excavation are to be used for the habitat
reconstruction.
Estimated construction cost is summarized in Table C4-3. Construction requires temporarily
diverting the river flow. Turbidity released is expected to be limited in extent and duration.
Access for construction is assumed down a temporary access routes through the Olympic
National Forest land, across river point bar, and across the Tower Creek alluvial fan. A ramp
constructed over the existing riprap revetment could provide temporary access for construction
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
and permanent access for maintenance. Upper Hoh Road traffic impacts are expected to be
limited to one-lane closures and short-term delays.
Moving the active river channel 400 feet south provides opportunity for creating off-channel
rearing and resting habitat along the toe of the existing riprap revetment. Moving the active river
channel more than 400 feet south would likely induce dramatic downstream bank erosion and
stream avulsion, resulting in unnatural changes in the HCMZ boundaries and loss of private
property and Olympic National Forest land.
Executive Order 11988, Floodplain Management, established federal policies for protecting
floodplains and floodways. The intention of the associated regulations is to avoid, to the extent
practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health,
and welfare; and avoid supporting land use development that is incompatible with the natural
and beneficial floodplain values. When avoidance is not possible, the policies require
appropriate consideration of methods to assess and minimize adverse impacts. If the option is
considered, additional analysis is needed for identifying extent and location of private property
impacts. If found violating Executive Order 11988, relocating the active river channel would not
be eligible for Federal funds.
Environmental Clearance Considerations
This section of the Upper Hoh Road appears to extend through private lands with FS lands to
the immediate south. The 1400 linear foot of rip-rap installed after flood events in 2004 and
2007 have created multiple fish barriers, preventing migratory and resident fish from accessing
high quality rearing habitat in a forested wetland on the north side of the road. This section of
road is adjacent to critical habitat for the bull trout. Northern spotted owl critical habitat is
located just south of the project and marbled murrelet critical habitat is located about ¾ of a mile
north of the project area in lands managed by the FS. A wetland delineation would need to be
conducted to confirm to determine its boundaries.
Except for as described below, environmental clearance considerations for Site C4 are the
same as described for Site C1.
Continue Maintenance
Environmental considerations are the same as those described in Site C1.
Relocate Road
The proposed relocation would involve placing fill in an estimated 2 acres of forested wetland.
This area appears to be suitable juvenile rearing and resting habitat for various fish species.
Removing the riprap revetment and the restoring the natural streambank in conjunction with the
installation of more natural streambarbs and engineer-long jams and the reestablishment of
wetlands and accessible off-channel rearing and resting habitat, could likely benefit bull trout
and resident fish.
This proposed work would require an Individual Permit under Section 404 of the Clean Water
Act as well as a 401 certification from the DOE. Due to the impacts to special aquatic sites
(wetlands) a full 404(b)(1) analysis is likely required demonstrating that this road relocation is
the least environmentally damaging (to wetlands) practicable alternative. Practicable is defined
in terms of cost, existing technology, and logistics. This project will also likely require off-site
wetland mitigation, using a wetland mitigation bank. Wetland mitigation banks in this area are
expensive, costing up to $200K per credit.
Upper Hoh Road - Bank Failure Risk Reduction Study
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Site C4 – County Milepost 7.8 Bank Stabilization
A biological assessment will need to be prepared evaluating impacts to bull trout, bull trout
designated critical habitat, marbled murrelet, and the northern spotted owl.
Hoh River Trust, owners of the land that would be impacted by the relocation have indicated
that there are easement restrictions preventing the Trust from selling the land for development
purposes. As a result, condemnation may be required.
Stabilize Existing Road Embankment
Environmental considerations are the same as those described in Site C1.
Minor and Major Active River Channel Shift
This could have a dramatic effect on the existing river system. The extent to which the option
helps or harms the aquatic habitat would need determined through modeling and formal
consultation with the Service, the Hoh Tribe, and the WDFW. This work would require an
individual permit from the Corps and 401 Certification from the DOE.
A biological assessment would need to be prepared evaluating short and long term impacts to
bull trout and short term construction impacts to the marbled murrelet and the northern spotted
owl.
In addition, geomorphic assessments would need to be conducted for assessing effect this
option may have on downstream properties.
Due to the scope of work and the limited in-water work window, WDFW would likely need to be
petitioned for an extension.
Each ELJ requires a number of trees to be cut down. Approximately 2,000 and 900 logs are
needed for the minor and major active river channel shift options, respectively. Cutting these
trees would have a direct impact on some forest’s ecosystem and watershed’s health.
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Upper Hoh Road - Bank Failure Risk Reduction Study
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Ac
t
i
v
e
Ch
a
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n
e
l
Li
m
i
t
AC
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Z
Upper Hoh Road - Bank Failure Risk Reduction Study
p 68
ea
g
v
d
a
f
av
d
f
v
Fi
g
u
r
e
C4
‐2.
Hi
s
t
o
r
i
c
a
l
Sa
t
e
l
l
i
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e
Im
a
g
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y
19
9
4
20
1
1
20
0
9
20
0
6
Upper Hoh Road - Bank Failure Risk Reduction Study
p 69
Photos C4 - MP 7.8 Bank Stabilization
PHOTO C4-1
PHOTO C4-2
PHOTO C4-3
12/12/2012
Bank 20 feet high. Lower 3 feet of toe
naturally armored with cobble/boulder
material. Gravel bar between bank and
natural woody debris jam at head of small
island. Woody debris deflects stream
flow towards bank. Distance between
bank and woody debris 150 feet.
Bank 20 feet high. Lower 3 feet of toe
naturally armored with cobble/boulder
material.
Steep, undercut, and eroding stream
bank immediately downstream of
revetment, looking downstream.
Looking downstream along riprap
revetment, upstream segment in
foreground.
Finished slope is steep, some riprap has
been dislodged from middle slope and
toe areas.
C4c - Steep, undercut, and eroding
stream bank immediately upstream of
revetment.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 70
Photos C4 - MP 7.8 Bank Stabilization
PHOTO C4-4
PHOTO C4-5
PHOTO C4-6
12/12/2012
Bank 20 feet high. Lower 3 feet of toe
naturally armored with cobble/boulder
material. Debris flow/alluvial material
from Tower Creek inhibits down-valley
meander bend migration.
Steep, undercut, and eroding stream
bank immediately downstream of
revetment, looking upstream.
Bank 20 feet high. Lower 3 feet of toe
naturally armored with cobble/boulder
material. Gravel bar between bank and
natural woody debris jam at head of small
island. Woody debris deflects stream
flow towards bank. Distance between
bank and woody debris 150 feet.
Looking upstream at riprap revetment,
eroding bank, gravel bar, and small
woody debris jam/island.
Bank 20 feet high. Lower 3 feet of toe
naturally armored with cobble/boulder
material. Gravel bar between bank and
natural woody debris jam at head of small
island. Woody debris deflects stream
flow towards bank. Distance between
bank and woody debris 150 feet.
C4a - Tower Creek confluence with Hoh
River - upstream along eroding bank.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 71
OP
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Rank ELJ Groins Rank Large Stream barbs Rank
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willow and alder.Construct new stream bank area over unstable and revetment areas.Construct new stream bank area over unstable and revetment areas.Shift active flow channel to flow across point bar away from revetment area.
Ab
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y
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(M
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5
,
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1
)
3
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t
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.
3
Be
t
t
e
r
t
h
a
n
w
h
e
r
e
i
t
i
s
,
b
u
t
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ri
v
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m
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a
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m
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no
r
t
h
a
n
d
i
m
p
a
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o
a
d
a
g
a
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.
5
Gr
e
a
t
l
y
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e
d
u
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s
r
i
s
k
o
f
a
ca
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a
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d
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g
ex
t
r
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d
e
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.
5
Gr
e
a
t
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d
u
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s
r
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k
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f
a
ca
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p
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ex
t
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5
Gr
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a
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d
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s
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k
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ex
t
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5
Gr
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a
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.
5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.5Greatly reduces risk of a catastrophic road failure during extreme flood event.
Ro
a
d
w
a
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s
u
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t
a
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a
b
i
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(
l
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)
(L
o
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s
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5
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t
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s
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1
)
1
In
c
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a
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m
a
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3
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c
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a
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p
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3
Re
q
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a
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a
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a
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ma
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a
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1
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3
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5
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.
1Requires substantial amount of wood replacement and maintenance.5 Requires moderate level of maintenance.1Requires substantial amount of wood replacement and maintenance.
Im
p
a
c
t
t
o
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y
1
;
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a
s
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l
i
k
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l
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5
)
5
No
e
x
p
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c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
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s
.
1
Ro
a
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a
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a
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p
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a
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s
a
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de
b
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f
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s
.
5
No
e
x
p
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c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
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c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Po
t
e
n
t
i
a
l
t
o
r
e
d
u
c
e
e
r
o
s
i
o
n
o
f
b
a
n
k
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a
d
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a
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t
t
o
s
i
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e
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Ad
j
a
c
e
n
t
b
a
n
k
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s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
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o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
c
e
n
t
b
a
n
k
e
r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3
Ad
j
a
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n
t
b
a
n
k
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r
o
s
i
o
n
w
i
l
l
co
n
t
i
n
u
e
.
3 Adjacent bank erosion will continue.3 Adjacent bank erosion will continue.1 Likely increase down stream right bank erosion.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
h
r
e
a
t
e
n
e
d
a
n
d
E
n
d
a
n
g
e
r
e
d
(
T
&
E
)
te
r
r
e
s
t
r
i
a
l
s
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e
c
i
e
s
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
a
n
d
po
t
e
n
t
i
a
l
l
y
T
&
E
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
&
E
f
i
s
h
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
Ri
p
r
a
p
p
l
a
c
e
d
a
l
o
n
g
b
a
n
k
re
d
u
c
e
s
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
3
Ma
t
e
r
i
a
l
p
l
a
c
e
d
i
n
c
h
a
n
n
e
l
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
B
a
r
b
s
re
q
u
i
r
e
s
i
g
n
i
f
i
c
a
n
t
e
x
c
a
v
a
t
i
o
n
in
t
o
c
h
a
n
n
e
l
b
e
d
.
3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.3Considerable temporary impacts from in-stream channel work.
Im
p
a
c
t
t
o
u
p
l
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
1
Im
p
a
c
t
s
u
p
l
a
n
d
a
r
e
a
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5 No expected additional impacts.5 No expected additional impacts.5 No expected additional impacts.
Im
p
a
c
t
s
t
o
W
e
t
l
a
n
d
s
a
n
d
W
a
t
e
r
s
o
f
t
h
e
U
.
S
.
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
Ri
p
r
a
p
p
l
a
c
e
m
e
n
t
i
n
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
.
3
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
to
w
e
t
l
a
n
d
s
;
r
i
p
r
a
p
p
l
a
c
e
m
e
n
t
in
r
i
v
e
r
.
1
Ri
p
r
a
p
a
l
o
n
g
b
a
n
k
r
e
d
u
c
e
s
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
.
B
a
r
b
s
re
q
u
i
r
e
s
i
g
n
i
f
i
c
a
n
t
e
x
c
a
v
a
t
i
o
n
in
t
o
c
h
a
n
n
e
l
b
e
d
.
1 Requires major in stream construction.1 Requires major in stream construction.1 Requires major in stream construction.
Im
p
a
c
t
t
o
D
e
s
i
g
n
a
t
e
d
W
i
l
d
e
r
n
e
s
s
a
r
e
a
(L
e
a
s
t
5
;
m
o
s
t
1
)
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
Ex
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0
No
e
x
p
e
c
t
e
d
i
m
p
a
c
t
s
.
0 No impacts.0 No impacts.0 No expected impacts.
Po
t
e
n
t
i
a
l
f
o
r
H
o
h
R
i
v
e
r
E
n
h
a
n
c
e
m
e
n
t
(G
r
e
a
t
e
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
r
i
v
e
r
en
h
a
n
c
e
m
e
n
t
s
.
5
Pr
o
v
i
d
e
s
o
f
f
-
c
h
a
n
n
e
l
/
s
i
d
e
-
ch
a
n
n
e
l
h
a
b
i
t
a
t
,
a
l
l
o
w
s
r
i
v
e
r
t
o
fu
l
l
y
a
c
c
e
s
s
H
C
M
Z
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Mo
v
e
s
t
h
a
l
w
e
g
a
w
a
y
f
r
o
m
ro
a
d
,
i
m
p
r
o
v
e
s
s
e
d
i
m
e
n
t
tr
a
n
s
p
o
r
t
a
n
d
h
a
b
i
t
a
t
co
m
p le
x
i
t
y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .
Po
t
e
n
t
i
a
l
t
o
m
a
i
n
t
a
i
n
o
r
i
m
p
r
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v
e
r
i
v
e
r
p
r
o
c
e
s
s
a
n
d
fu
n
c
t
i
o
n
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
i
m
p
r
o
v
e
r
i
v
e
r
p
r
o
c
e
s
s
an
d
f
u
n
c
t
i
o
n
.
5
Pr
o
v
i
d
e
s
o
f
f
-
c
h
a
n
n
e
l
/
s
i
d
e
-
ch
a
n
n
e
l
h
a
b
i
t
a
t
,
a
l
l
o
w
s
r
i
v
e
r
t
o
fu
l
l
y
a
c
c
e
s
s
H
C
M
Z
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
w
o
o
d
y
d
e
b
r
i
s
f
o
r
ha
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Mo
v
e
s
t
h
a
l
w
e
g
a
w
a
y
f
r
o
m
ro
a
d
,
i
m
p
r
o
v
e
s
s
e
d
i
m
e
n
t
tr
a
n
s
p
o
r
t
a
n
d
h
a
b
i
t
a
t
co
m
p le
x
i
t
y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .5Moves thalweg away from road, adds bank area, improves sediment transport and habitat com p lexit y .
Po
t
e
n
t
i
a
l
f
o
r
o
t
h
e
r
h
a
b
i
t
a
t
e
n
h
a
n
c
e
m
e
n
t
s
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
o
t
h
e
r
h
a
b
i
t
a
t
en
h
a
n
c
e
m
e
n
t
s
.
5
Op
p
o
r
t
u
n
i
t
y
f
o
r
i
m
p
r
o
v
i
n
g
f
i
s
h
ac
c
e
s
s
t
o
o
f
f
-
c
h
a
n
n
e
l
h
a
b
i
t
a
t
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
3
Pr
o
v
i
d
e
s
s
o
m
e
w
o
o
d
y
d
e
b
r
i
s
fo
r
h
a
b
i
t
a
t
c
o
m
p
l
e
x
i
t
y
a
n
d
bi
o
l
o
g
i
c
a
l
p
r
o
c
e
s
s
e
s
.
1
Do
e
s
n
o
t
p
r
o
v
i
d
e
o
t
h
e
r
h
a
b
i
t
a
t
en
h
a
n
c
e
m
e
n
t
s
.
5Provides woody debris for habitat complexity and biological processes.3Provides some woody debris for habitat complexity and biological processes.5Provides woody debris for habitat complexity and biological processes.
Po
t
e
n
t
i
a
l
p
r
i
v
a
t
e
p
r
o
p
e
r
t
y
i
m
p
a
c
t
s
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
im
p
a
c
t
s
.
3Some impacts expected from bank erosion downstream of site. 3Some impacts expected from bank erosion downstream of site. 1 Impacts likely from bank erosion downstream of site.
Sa
f
e
t
y
r
i
s
k
o
f
d
e
s
i
g
n
t
o
p
u
b
l
i
c
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
i
n
c
r
e
a
s
e
i
n
s
a
f
e
t
y
ri
s
k
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
1
Pu
b
l
i
c
c
o
u
l
d
f
a
l
l
d
o
w
n
w
a
l
l
.
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
3
Bo
a
t
e
r
s
c
o
u
l
d
b
e
c
o
m
e
t
r
a
p
p
e
d
in
r
o
o
t
w
a
d
s
.
5
No
e
x
p
e
c
t
e
d
i
n
c
r
e
a
s
e
i
n
s
a
f
e
t
y
ri
s
k
.
1 Boaters could become trapped in ELJ's.3 Boaters could become trapped in root wads.1 Boaters could become trapped in ELJ's.
To
t
a
l
C
o
n
s
t
r
u
c
t
i
o
n
c
o
s
t
N
A
$
7
,
0
6
6
,
2
8
0
$
8
5
5
,
2
0
7
$
1
,
1
5
1
,
9
5
4
$
1
,
7
2
4
,
3
2
5
$
1
,
6
5
0
,
1
3
8
$
6
,
3
9
4
,
7
0
5
$
3
,
8
6
6
,
7
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2
$
4
,
0
3
3
,
9
0
0
Ri
p
r
a
p
a
n
d
W
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o
d
R
e
p
l
a
c
e
m
e
n
t
(
5
0
y
e
a
r
s
)
N
A
$
1
,
5
8
0
,
0
0
0
$
2
6
4
,
0
0
0
$
5
2
2
,
6
6
7
$
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8
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,
3
3
3
$
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8
2
,
6
6
7
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9
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2
0
0
$
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3
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,
8
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,
0
0
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To
t
a
l
C
a
p
i
t
a
l
C
o
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72
Date: 3/14/2013
By: S. Leon
Flood
Frequency
(yr)
Exceedance
Probability
Flood
Damage
Average
Flood
Damage
Delta
Exceedance
Probability
Annual Risk
Cost
No damage.2 0.5 $0
$0 0.3 $0
No damage.5 0.2 $0
$0 0.1 $0
No damage.10 0.1 $0
$150,000 0.06 $9,000
Place riprap.25 0.04 $300,000
$300,000 0.02 $6,000
Place riprap.50 0.02 $300,000
$300,000 0.01 $3,000
Place riprap.100 0.01 $300,000
$300,000 0.01 $3,000
0 $300,000
$21,000
$0
Disc. rate, i 0.07125 Serv. life, n 50 CFR 0.0736
$0
Total Expected Cost (Annual)$21,000
Summary
Notes:
1. Method from HEC-17, April 1981.
Table C4-2. Total Expected Cost
Project: Hoh River Road Bank Erosion Risk Study
Site: C4 - CMP 7.8 Bank Stabilization
Alternative: Continue Maintenance
Total Annual Risk Cost
Annualized Capital
Cost
Capital Cost
Annualized Capital Cost
Assume 300 feet ($1k/ft) of revetment repair and bank armoring for each flood damage event.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 73
Table C4-3. Cost Estimates
Site:
Relocate Road
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 355,600$ 355,600$
New Road LF 2,000 500$ 1,000,000$
Hillside Stabilization LS 1 100,000$ 100,000$
Remove Existing Revetment LF 1,400 200$ 280,000$
Streambank Reconstruction LF 1,800 1,000$ 1,800,000$
Streambarbs EA 10 40,000$ 400,000$
ELJ's EA 5 300,000$ 1,500,000$
Total Construction Cost without Contingencies 5,435,600$
Contingency 30% of construction cost 1,630,680$
Total Construction Cost 7,066,280$
Compliance 5% of total construction cost 353,314$
Predesign/design (PE)15% of total construction cost 1,059,942$
Construction Engineering (CE)15% of total construction cost 1,059,942$
ROW 50,000$
Riprap replacement -20% replacement every 50 years 80,000$
Wood replacement -full log replacement every 30 years 1,500,000$
TOTAL Capital Cost Cost/Foot 5,585$ 11,169,478$
Annualized Capital Cost Discount rate, i 0.07125 822,153$
Service life, n 50 years
CFR 0.0736071
Complex Roughened Large Rock Toe
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 43,037$ 43,037$
Remove Existing Revetment LF - 200$ -$
Rock H 12 ft T 5 ft CY 1,778 180$ 320,000$
L 800 ft
Logs L 800 ft XS 8 ft EA 100 2,000$ 200,000$
Soil H 8 ft T 10 ft CY 2,370 40$ 94,815$
L 800 ft
Total Construction Cost without Contingencies 657,852$
Contingency 30% of construction cost 197,356$
Total Construction Cost 855,207$
Compliance 5% of total construction cost 42,760$
Predesign/design (PE)15% of total construction cost 128,281$
Construction Engineering (CE)15% of total construction cost 128,281$
ROW -$
Riprap replacement -20% replacement every 50 years 64,000$
Wood replacement -full log replacement every 30 years 200,000$
TOTAL Capital Cost Cost/Foot 1,773$ 1,418,530$
Annualized Capital Cost Discount rate, i 0.07125 104,414$
Service life, n 50 years
CFR 0.0736071
C4 - CMP 7.8 Bank Stabilization
Upper Hoh Road - Bank Failure Risk Reduction Study
p 74
Table C4-3. Cost Estimates
Complex Log Crib Wall
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 57,970$ 57,970$
Remove Existing Revetment LF 200 200$ 40,000$
Rock H 12 ft T 5 ft CY 1,778 120$ 213,333$
L 800 ft
Logs L 800 ft H 12 ft EA 240 2,000$ 480,000$
Dia 2 ft Row 6
log l 20 ft No. 240
Piles EA 0 -$ -$
Soil H 8 ft T 10 ft CY 2,370 40$ 94,815$
L 800 ft
Total Construction Cost without Contingencies 886,119$
Contingency 30% of construction cost 265,836$
Total Construction Cost 1,151,954$
Compliance 5% of total construction cost 57,598$
Predesign/design (PE)15% of total construction cost 172,793$
Construction Engineering (CE)15% of total construction cost 172,793$
ROW -$
Riprap replacement -20% replacement every 50 years 42,667$
Wood replacement -full log replacement every 30 years 480,000$
TOTAL Capital Cost Cost/Foot 2,597$ 2,077,805$
Annualized Capital Cost Discount rate, i 0.07125 152,941$
Service life, n 50 years
CFR 0.0736071
Riprap with Roughened Rock Toe, LWD, and Riparian Plantings
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 86,774$ 86,774$
Remove Existing Revetment LF 200 200$ 40,000$
Riprap H 13 ft T 5 ft CY 5,037 180$ 906,667$
L 800 ft SS 2 (h):1(v)
TW 8 ft TT 5 ft
Logs L 800 ft XS 8 ft EA 100 2,000$ 200,000$
Willow 400 sy XS 2 EA 200 10$ 2,000$
Alder 400 sy XS 1 EA 400 20$ 8,000$
Soil H 7 ft T 10 ft CY 2,074 40$ 82,963$
L 800 ft
Total Construction Cost without Contingencies 1,326,404$
Contingency 30% of construction cost 397,921$
Total Construction Cost 1,724,325$
Compliance 5% of total construction cost 86,216$
Predesign/design (PE)15% of total construction cost 258,649$
Construction Engineering (CE)15% of total construction cost 258,649$
ROW -$
Riprap replacement -20% replacement every 50 years 181,333$
Wood replacement -full log replacement every 30 years 200,000$
TOTAL Capital Cost Cost/Foot 3,386$ 2,709,172$
Annualized Capital Cost Discount rate, i 0.07125 199,414$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 75
Table C4-3. Cost Estimates
Riprap with Streambarbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 83,041$ 83,041$
Remove Existing Revetment LF - 200$ -$
Riprap H 13 ft T 5 ft CY 3,852 180$ 693,333$
L 800 ft SS 2 (h):1(v)
TW 0 ft TT 0 ft
Streambarbs EA 8 40,000$ 320,000$
Logs L 800 ft XS 20 ft EA 40 2,000$ 80,000$
Willow 400 sy XS 2 EA 200 10$ 2,000$
Alder 400 sy XS 1 EA 400 20$ 8,000$
Soil H 7 ft T 10 ft CY 2,074 40$ 82,963$
L 800 ft
Total Construction Cost without Contingencies 1,269,337$
Contingency 30% of construction cost 380,801$
Total Construction Cost 1,650,138$
Compliance 5% of total construction cost 82,507$
Predesign/design (PE)15% of total construction cost 247,521$
Construction Engineering (CE)15% of total construction cost 247,521$
ROW -$
Riprap replacement -20% replacement every 50 years 202,667$
Wood replacement -full log replacement every 30 years 80,000$
TOTAL Capital Cost Cost/Foot 3,138$ 2,510,353$
Annualized Capital Cost Discount rate, i 0.07125 184,780$
Service life, n 50 years
CFR 0.0736071
Major River Channel Shift
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 203,000$ 203,000$
Channel Excavation - 100 feet by 5 feet LF 2,000 300$ 600,000$
Rearing and Resting Habitat Construction AC 10 50,000$ 500,000$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction LF - 1,000$ -$
Streambarbs EA - 40,000$ -$
ELJ's - 20 ft by 60 ft EA 6 300,000$ 1,800,000$
Total Construction Cost without Contingencies 3,103,000$
Contingency 30% of construction cost 930,900$
Total Construction Cost 4,033,900$
Compliance 5% of total construction cost 201,695$
Predesign/design (PE)15% of total construction cost 605,085$
Construction Engineering (CE)15% of total construction cost 605,085$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 1,800,000$
TOTAL Capital Cost Cost/Foot 3,623$ 7,245,765$
Annualized Capital Cost Discount rate, i 0.07125 533,340$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 76
Table C4-3. Cost Estimates
Minor River Channel Shift - ELJ Groins
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 321,804$ 321,804$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 1,300 1,200$ 1,560,000$
Large Wood EA 80 1,500$ 120,000$
ELJ groin - 15 ft by 60 ft (3 x 15 ft by 20 ft mod.)EA 13 224,400$ 2,917,200$
Primary logs 50
Pin logs 4
Ballast stone 50
Cabling 1
74,800$
No. modules/ ELJ groin 3 224,400$
Total Construction Cost without Contingencies 4,919,004$
Contingency 30% of construction cost 1,475,701$
Total Construction Cost 6,394,705$
Compliance 5% of total construction cost 319,735$
Predesign/design (PE)15% of total construction cost 959,206$
Construction Engineering (CE)15% of total construction cost 959,206$
ROW -$
Riprap replacement -20% replacement every 50 years -$
Wood replacement -full log replacement every 30 years 2,917,200$
TOTAL Capital Cost Cost/Foot 4,919$ 11,550,052$
Annualized Capital Cost Discount rate, i 0.07125 850,166$
Service life, n 50 years
CFR 0.0736071
Minor River Channel Shift - Stream Barbs
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 194,586$ 194,586$
Rearing and Resting Habitat Construction AC - 50,000$ -$
Remove Existing Revetment LF - 200$ -$
Streambank Reconstruction - fill/plants/fascines LF 1,300 1,200$ 1,560,000$
Large Wood EA 80 1,500$ 120,000$
Streambarbs Length 100 ft EA 13 84,600$ 1,099,800$
Crest width 8 ft
Average bot. width 28 ft
Average thickness 7 ft
Volume 470 cy
Cost/cy 180 $/cy Cost/barb 84,600$
Total Construction Cost without Contingencies 2,974,386$
Contingency 30% of construction cost 892,316$
Total Construction Cost 3,866,702$
Compliance 5% of total construction cost 193,335$
Predesign/design (PE)15% of total construction cost 580,005$
Construction Engineering (CE)15% of total construction cost 580,005$
ROW -$
Riprap replacement -20% replacement every 50 years 219,960$
Wood replacement -full log replacement every 30 years 120,000$
TOTAL Capital Cost Cost/Foot 2,974$ 5,560,007$
Annualized Capital Cost Discount rate, i 0.07125 409,256$
Service life, n 50 years
CFR 0.0736071
180$ 9,000$
1,000$ 1,000$
1,200$ 60,000$
1,200$ 4,800$
Upper Hoh Road - Bank Failure Risk Reduction Study
p 77
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 78
C5 - COUNTY MILEPOST 10.2
CANYON CREEK CULVERT
Upper Hoh Road - Bank Failure Risk Reduction Study
p 79
Site C5 – Canyon Creek Culvert
SITE C5 - CANYON CREEK CULVERT
Existing Culvert
The existing drainage is an 8.5 feet diameter corrugated metal pipe, located at a low point of a
sag vertical curve and buried under approximately 25 to 30 feet fill. The existing culvert is in fair
condition (Photo C5-6). There is damage at the crown and invert of the pipe with some
separations at the joints. Offsets at the crown of 6 to 10 inches were observed at three joint
locations. The pipe crown damage may have been due to original construction. It has been
filled in with grout and appears to be stable. At the inlet the pipe is armored with riprap (Photo
C5-3). There is evidence of debris accumulation at the upstream opening. At the outlet, the
culvert is protruding approximately 5 feet beyond the road embankment fill and 3 feet above the
water surface of a large (30 feet by 30 feet by 4 feet) scour hole (Photos C5-4 and 5). The road
embankment material is erodible. Undercutting of the culvert outlet is expected to continue.
Water streaming out from under the pipe suggests there is water piping through the culvert
bedding material. Possible sources of the water include groundwater, stream water flowing
under pipe, and stream water flowing out from the inside of the culvert. The offset crown joint
may entangle large woody debris. Removal of the woody debris from inside the culvert would
be difficult and hazardous. Based on observed pipe damage and assuming woody debris is not
trapped inside the culvert, the culvert could provide another 20 years of service life. Water
seeping under the culvert may indicate a potential risk for the bedding material failing. Woody
debris trapped inside the culvert could cause water to pond at the inlet, increasing loading and
saturation to the point that a catastrophic road embankment failure occurs.
The active channel width is approximately 16 feet. Ordinary high water flow depth is
approximately 2.5 feet. Stream gradient upstream of the culvert is approximately 10 percent.
Stream gradient downstream of the culvert is approximately 5 percent (Photo C5-2). Step-pool
and cascade are the dominant bed forms. Cobble and small boulders are the dominant bed
material. Estimated 2-year, 50-year, and 100-year peak discharges are 215 cfs, 450 cfs, and
504 cfs, respectively (StreamStats). Based on a HY-8 hydraulic analysis, the calculated
headwater depths for the 2-year, 50-year, and 100-year peak discharges are 5.5 feet, 8.6 feet,
and 9.4 feet, respectively. There is abundant woody debris available for recruitment to the
stream from windfall and stream bank erosion. The stream is capable of transporting the woody
debris at the more extreme (> 25-year) flood events.
Considered Options
In addition to continued maintenance, three options were evaluated. Constructing rock weirs at
the existing culvert outlet provides fish passage. Open-bottom arch culvert and a new bridge
replace the existing culvert with structures capable of passing fish and expected woody debris.
Table C5-1 presents an evaluation and ranking of the options against design selection criteria.
Continue Maintenance
The displaced and offset culvert joints may increase the risk of woody debris hanging up inside
the culvert. Debris accumulation at the inlet, joint gaping inside the culvert, debris accumulation
inside the culvert, and undercutting at the outlet will need to be monitored. To avoid a
catastrophic failure, the inspections should be done annually and after each major flood event.
The height of the road embankment makes monitoring difficult. The culvert interior can only be
safely accessed during low flow conditions.
A Total Expected Cost analysis (HEC-17, FHWA, April 1981) was completed for estimating total
expected cost repairing damage caused by flooding. The analysis assumes a 50-year service-
Upper Hoh Road - Bank Failure Risk Reduction Study
p 80
Site C5 – Canyon Creek Culvert
life. Based on the capacity of the stream and culvert for transporting water and woody debris,
debris removal from the inlet area and inside the culvert is expected to be needed for 25-year
and larger flood events. Estimated cost for removing debris from the inlet area and inside the
culvert is $20,000 per removal event. The analysis assumes the road embankment will be
completely washed out for the 500-year flood event. Cost for a new bridge is estimated to be
$4,400,000 (Table C5-3). Bridge replacement assumes road is shifted upstream slightly for
providing temporary traffic access. Total expected annual cost is $18,880 (Table C5-2, Total
Expected Cost).
Rock Weirs at Existing Culvert Outlet
Fish passage could be provided by constructing rock weirs immediately downstream of the
existing scour pool that elevate the water surface high enough to eliminate the outlet leap and
allow fish to swim directly into the culvert. Four to five rock weirs are needed for effectively
reducing the stream gradient enough for fish to easily migrate through the structures. To
prevent the stream from cutting around the rock weirs, each rock weir must extend into the
valley walls, approximately 40 to 50 feet total length. The rock weirs do not reduce the risk of
debris becoming trapped inside the culvert. If ponding backwatering the outlet reduces flow
velocities and increases flow depth inside the culvert, the weirs may increase the debris
accumulation risk. The rock weirs require rebuilding and are prone to being undermined from
downstream degradation.
Access for construction would be difficult. The likely scenario is lowering equipment and stone
down the existing road embankment. A temporary wood/rock pad would provide access to the
rock weir sites. The temporary pad would be removed and the area reclaimed once
construction is completed. Traffic would likely be reduced to one-lane with short-duration
interruptions. Estimated construction costs are summarized in Table C5-3.
New Open-bottom Arch Culvert
Based on the field observations, an open-bottom arch with 22 feet span and 11 feet rise is
recommended as a culvert alternative. An open-bottom arch constructed over the existing
culvert facilitates temporary stream flow diversion. The arch culvert would be placed on a
concrete footing founded below expected stream profile degradation and scour, estimated to be
8 feet. Riprap and/or engineered-streambed are placed along the footings for mitigating scour.
Assuming 50 feet road embankment top width and 2(h):1(v) embankment side slopes, the
culvert length is 160 feet. Cast-in-place concrete collars provide stiffness for the multi-plate
culvert structure. Installing the arch culvert requires a 25 to 30 feet deep excavation.
Excavation for the concrete footing would extend down below the arch bottom an additional 10
feet. Width of the excavation at the road surface would be at least 100 feet. Excavating for and
installing the culvert would require closing the road to traffic for at least six weeks. Estimated
construction costs are summarized in Table C5-3.
New 180 Feet Bridge
Based on the field observation and conceptual hydraulic recommendation, a conceptual bridge
length is approximately 160 feet to 180 feet. The conceptual bridge length was based on the
following assumptions: 20 feet channel width, 30 feet vertical clearance, 2:1 fill slope, 5 feet of
riprap thickness, and approximate abutment and end diaphragm thicknesses.
SPAN ARRANGEMENT: Single span, Two-span & Three-span arrangements were evaluated.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 81
Site C5 – Canyon Creek Culvert
A single clear span structure does not require interior support piers, which eliminates most
construction in the channel. This option also eliminates dewatering, temporary cofferdams, and
stream temporary work for construction equipment access to the pier locations. Long-term
problems with pier scour are also avoided. This option, however, requires approximately 160 to
180-foot long bridge girders, which will have shipping and weight limit issues. The prestressed
concrete girders can also be shipped in two pieces and spliced together on the site using post-
tensioning. Steel plate girders can be shipped in two or three pieces and field spliced with high
strength bolts. The single span structure will have the deepest and heaviest superstructure,
which will require larger cranes to set the girders. The analysis included two structural types for
the single-span arrangement using prestressed concrete girders, and steel plate girders.
A two-span or three-span structure uses shorter and more cost-effective bridge girders; yet the
cost saving from the superstructure may offset by the cost of the additional foundation and pier,
and in-water temporary work for the intermediate pier(s). Rolled steel beams or prestressed
concrete girders work well for this structure arrangement. These prestressed concrete girders
can be shipped in single pieces, do not require field splicing, and can be erected bent to bent.
Steel rolled beams will be continuous over the interior pier and shipped in two pieces with a
simple bolted splice near one third span points. This multiple span arrangements will help
minimize the structural depth and reduce the cost of the bridge superstructure. However, the
bridge pier(s) will have to be constructed with this option with all the associated problems of
dewatering, cofferdams, and equipment access. The additional pier(s) and shorter spans will
combine to catch and retain debris, and provide another mechanism for scour to form under the
bridge.
The multiple-span arrangements require intermediate pier(s) and present construction
difficulties/concerns such as in-water work, dewatering, cofferdams and equipment access, and
potential debris & scour issues. Based on the above discussion and available vertical clearance
of the channel, the single span arrangement lends itself well at this site.
SUPERSTRUCTURE TYPE: Precast prestressed concrete girders are appropriate girder types
for stream crossings. The precast girders can be lifted into place by cranes located on the banks
of the channels, eliminating the need for falsework and minimizing channels disturbances.
Steel girders are also a very practical superstructure type. Steel prices have been volatile in the
recent past, but now appear to be stable. As mentioned above the steel girders can be shipped
in two or three pieces and field spliced with high strength bolts, and erected by cranes located
on the banks of the channels similar to precast prestressed concrete girders.
SUBSTRUCTURE TYPE: Semi-integral abutments supported on deep foundation with
cantilevered wing walls are recommended. This type of construction will eliminate the need for
any expansion joints on the bridge superstructure eliminating water leakage and long term
maintenance associated with expansion joints. Additionally, this type of abutment configuration
will help to eliminate design complexity and the uncertainty of the structure and soil movements.
The foundation type cannot be fully determined until the geotechnical investigation is advanced
at the later time.
STRUCTURE ALTERNATIVES AND PRELIMINARY COST ESTIMATES: The study evaluated
two structure types for the single span arrangements using precast prestressed concrete girders
and steel plate girders. Due to the lack of information at this phase, the longer bridge length of
180 feet is selected for this analysis, with centerline bearing to centerline bearing from each
abutment to be approximately 172 feet.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 82
Site C5 – Canyon Creek Culvert
Table C5-4. Summary of Bridge Structure Type Alternative
Alt. No. No. of
Spans
Span
Length
Girder
Type
Girder
Spacing
Deck
Thickness
Total
Cost
Cost
per sft
1 1 180 WASHINGTON
WF83G
8’-0” 8.5” $1,550,000 $240
2 1 180 Steel Plant
Girder
(84” Web)
8’-0” 8.5” $1,840,000 $285
Alternative 1, the single span using Washington WF83G prestressed bulb-tee girders, is the
recommended alternative. This option provides the best compromise between structure costs,
constructability and environmental concerns.
Because the abutments are integral with the superstructure, approach slabs are recommended
to ensure ride-ability across the abutments should the approach fill settle. Deck drains are not
anticipated due to the longitudinal slope, crowned deck section, and shoulders. Catch basins
can be installed in the shoulder approach of the bridge to capture pavement runoff flowing
toward the bridge.
Construction Phasing: Due to the 30 feet fill on top the existing culvert, it may be very difficult,
impractical or costly to stage the new bridge construction on the existing alignment while
maintaining traffic during construction. An alignment shift is assumed for this bridge alternative.
If a one-lane temporary traffic is an acceptable detour during construction, the alignment shift
may be minimized by employing staged construction on the new bridge.
The proposed construction phasing for this bridge is described in the following subsections.
Phase 1: While maintaining traffic in the existing alignment, construction the south portion of
the new bridge offset from the existing alignment. Construct the permanent bridge rail on the
south bridge edge, and set a temporary concrete barrier along the north edge of the bridge. This
first south portion of the new bridge may have to have a minimum width of 20 feet edge to edge
to provide a one-lane 10-foot lane with 2-foot shoulders.
Phase 2: Shift traffic onto the completed south portion of the new structure. Remove the
existing fill and culvert completely or partially to yield enough space to construct the north
portion of the new bridge. Construct the remaining north portion of the new bridge.
The estimated construction cost for the new bridge, shifting the road alignment, removing the
existing bridge, and installing riprap abutment scour countermeasures are summarized in Table
C5-3.
Environmental Clearance Considerations
This portion of the road appears to extend through Hoh River Trust Lands. The culvert is
presently perched and prevents fish passage to upstream habitat for migratory and resident fish.
The WDFW have identified this stretch of Canyon Creek as a Priority Habitat for both native and
migratory fish. The leap at the culvert outlet is a physical barrier to upstream fish migration.
Washington State law requires that, where streams either historically or presently inhabited by
native fish, new culverts must provide effective upstream fish migration for all life stages of fish.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 83
Site C5 – Canyon Creek Culvert
National Wetland Inventory maps did not identify any wetlands at this project location. A
wetland survey and, if needed, delineation, will need to be conducted to confirm this negative
finding. There is no designated critical habitat for marbled murrelet or northern spotted owl,
though there may be suitable habitat or individuals of species in the project area. Designated
bull trout critical habitat is located downstream in the Hoh River. Because the culvert has a
remaining service life of at least 20 years, the primary purpose of this project is to reestablish
fish passage
Continue Maintenance
Canyon Creek is a water of the US and State. Monitoring and debris removal activities are
typically exempt from permitting and environmental clearance activities. Should the culvert fail,
a pulse of sediment will be sent into the Hoh River. If this occurs during the storm event, the
increase in turbidity will likely be negligible when compared to the background levels.
Rock Weirs at Existing Culvert Outlet
The proposed work would likely require a Nationwide Permit (#18) provided that the discharged
material does not exceed 25 cubic yards below the ordinary high water mark and it does not fill
more than 1/10th of an acre of waters of the US. A biological assessment may be needed to
evaluate effects construction activities would have on bull trout and its designated critical
habitat.
New Open-bottom Arch Culvert
This work would involve work below the ordinary high water mark and would trigger a 404
permit and 401 Certification. Because the primary intent of the work is to reestablish fish
passage, the project may qualify for Nationwide Permit 27 – Aquatic Habitat Restoration,
Establishment, and Enhancement Activities.
A stream analysis should be done to determine the extent to which the streambed would incise
upstream of the new culvert given that incision typically adversely affects fish habitat. This
analysis should be coordinated with the WDFW, the Hoh Tribe, and the U.S. Fish and Wildlife
Service (Service). It is likely the incision would need to be reduced by installing bed-stabilizing
features.
A biological assessment evaluating impacts to bull trout and critical habitat would need to be
prepared. Effects to marbled murrelet and northern spotted owl individuals and suitable habitat
may also need to be evaluated.
New 180 Feet Bridge
For all bridge proposals removal of the culvert and fill may require a section 404 permit and 401
Certification. For the single-span bridge, the placement of riprap may occur below the ordinary
high water mark, thereby triggering the need for a 404 permit/401 Certification.
For multi-span bridges piers should be placed outside of the ordinary high water mark. If this is
not feasible, then a 404 permit and 401 Certification would be required.
Regardless of bridge type, a stream analysis should be done to determine the extent to which
the streambed would incise upstream of the new culvert given that incision typically adversely
affects fish habitat. The analysis should be coordinated with the WDFW, the Hoh Tribe, and the
Service.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 84
Site C5 – Canyon Creek Culvert
A biological assessment evaluating short-term impacts culvert removal would have on bull trout
and designated critical habitat would need to be prepared. Also, because the bridge alignment
would need to be shifted in order to permit one way traffic during construction, clearing and
vegetation removal would likely occur. As a result, a biological assessment addressing effects
to marbled murrelet and northern spotted owl individuals and suitable habitat would need to be
prepared.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 85
(Page left blank.)
Upper Hoh Road - Bank Failure Risk Reduction Study
p 86
ea
g
v
d
a
f
av
d
f
v
AC
M
Z
‐
Ac
t
i
v
e
Ch
a
n
n
e
l
Mi
g
r
a
t
i
o
n
Zo
n
e
,
Ge
o
m
o
r
p
h
i
c
As
s
e
s
s
m
e
n
t
of
Ho
h
Ri
v
e
r
in
Wa
s
h
i
n
g
t
o
n
St
a
t
e
,
US
B
R
,
Ju
l
y
20
0
4
.
Im
a
g
e
r
y
da
t
e
9/
2
5
/
2
0
1
1
.
Fi
g
u
r
e
C5
‐1.
Si
t
e
Lo
c
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i
o
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AC
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Upper Hoh Road - Bank Failure Risk Reduction Study
p 87
Photos C5 - Canyon Creek Culvert
PHOTO C5-1
PHOTO C5-2
PHOTO C5-3
12/12/2012
25 feet high road embankment. Riprap
headwall appears stable. Gravel,
cobbles and boulders inside culvert.
Pipe slope approx. 5 percent. Three
joints inside culvert offset 6 to 10 inches
at crown.
Large (30 feet x30 feet x 4 feet) scour
hole at outlet. Stream channel gradient 5
percent.
8.5 feet dia. culvert inlet.
Looking upstream from road
embankment.
Bankfull width approx. 16 feet, road
embankment height 25 feet, stream
channel gradient approx. 10 percent.
Looking downstream from road
embankment.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 88
Photos C5 - Canyon Creek Culvert
PHOTO C5-4
PHOTO C5-5
PHOTO C5-6
12/12/2012
Gravel, cobbles, and boulders inside
culvert. Pipe slope approx. 5 percent.
Three joints inside culvert offset 6 to 10
inches at crown.
Culvert outlet.
3 feet water drop. Culvert undercut
approx. 5 feet. Seepage observed under
pipe. Large (30 feet x30 feet x 4 feet)
scour hole at outlet. Stream channel
gradient 5 percent.
Scour hole downstream of culvert outlet.
Existing riffle at downstream edge of
scour hole. Valley bottom width 40 to 50
feet.
8.5 feet dia. culvert inlet.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 89
OP
T
I
O
N
S
Ra
n
k
Co
n
t
i
n
u
e
d
M
a
i
n
t
e
n
a
n
c
e
Ra
n
k
Ro
c
k
W
e
i
r
s
Ra
n
k
Ne
w
O
p
e
n
-
b
o
t
t
o
m
Culvert Rank New Bridge
Re
m
o
v
e
d
e
b
r
i
s
f
r
o
m
c
u
l
v
e
r
t
i
n
s
i
d
e
a
n
d
i
n
l
e
t
.
In
s
t
a
l
l
t
w
o
r
o
c
k
w
e
i
r
s
f
o
r
b
a
c
k
w
a
t
e
r
i
n
g
e
x
i
s
t
i
n
g
cu
l
v
e
r
t
a
n
d
p
r
o
v
i
d
i
n
g
f
i
s
h
p
a
s
s
a
g
e
-
d
o
e
s
no
t
h
i
n
g
f
o
r
r
e
d
u
c
i
n
g
d
e
b
r
i
s
j
a
m
r
i
s
k
.
In
s
t
a
l
l
n
e
w
2
2
-
f
e
e
t
w
i
d
e
o
p
e
n
-
b
o
t
t
o
m
c
u
l
v
e
r
t
.
Install new 180 feet long bridge - requires new road alignment immediately upstream of existing bridge.
Ab
i
l
i
t
y
t
o
p
r
e
s
e
r
v
e
a
n
d
o
p
e
r
a
t
e
t
h
e
r
o
a
d
w
a
y
i
n
a
sp
e
c
i
f
i
c
l
o
c
a
t
i
o
n
(M
o
s
t
a
b
l
e
5
,
l
e
a
s
t
a
b
l
e
1
)
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
w
a
s
h
o
u
t
r
o
a
d
em
b
a
n
k
m
e
n
t
.
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
w
a
s
h
o
u
t
r
o
a
d
em
b
a
n
k
m
e
n
t
.
3
Re
d
u
c
e
s
d
e
b
r
i
s
j
a
m
r
i
s
k
a
n
d
o
p
e
n
s
c
h
a
n
n
e
l
.
5 Mitigates debris jam risk and opens channel.
Ro
a
d
w
a
y
s
u
s
t
a
i
n
a
b
i
l
i
t
y
(
l
i
f
e
o
f
s
o
l
u
t
i
o
n
)
(L
o
n
g
e
s
t
5
,
s
h
o
r
t
e
s
t
1
)
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
w
a
s
h
o
u
t
r
o
a
d
em
b
a
n
k
m
e
n
t
.
1
La
r
g
e
f
l
o
o
d
e
v
e
n
t
c
o
u
l
d
w
a
s
h
o
u
t
r
o
a
d
em
b
a
n
k
m
e
n
t
.
3
Re
d
u
c
e
s
d
e
b
r
i
s
j
a
m
r
i
s
k
a
n
d
o
p
e
n
s
c
h
a
n
n
e
l
.
5 Mitigates debris jam risk and opens channel.
Im
p
a
c
t
t
o
h
i
l
l
s
i
d
e
s
t
a
b
i
l
i
t
y
a
d
j
a
c
e
n
t
t
o
s
i
t
e
(M
o
s
t
l
i
k
e
l
y
1
;
l
e
a
s
t
l
i
k
e
l
y
5
)
1
No
i
m
p
a
c
t
t
o
g
e
o
l
o
g
i
c
a
l
s
t
a
b
i
l
i
t
y
.
1
No
i
m
p
a
c
t
t
o
g
e
o
l
o
g
i
c
a
l
s
t
a
b
i
l
i
t
y
.
1
No
i
m
p
a
c
t
t
o
g
e
o
l
o
g
i
c
a
l
s
t
a
b
i
l
i
t
y
.
3 Shift in road alignment to construct new bridge may induce hillside instability.
Po
t
e
n
t
i
a
l
t
o
r
e
d
u
c
e
e
r
o
s
i
o
n
o
f
b
a
n
k
s
a
d
j
a
c
e
n
t
t
o
s
i
t
e
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Un
d
e
r
s
i
z
e
d
c
u
l
v
e
r
t
c
a
u
s
e
s
b
a
n
k
e
r
o
s
i
o
n
a
t
o
u
t
l
e
t
.
3
Ba
n
k
e
r
o
s
i
o
n
a
t
o
u
t
l
e
t
m
i
t
i
g
a
t
e
d
.
5
Ch
a
n
n
e
l
l
e
s
s
c
o
n
s
t
r
a
i
n
e
d
.
5 Channel not constrained.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
h
r
e
a
t
e
n
e
d
a
n
d
E
n
d
a
n
g
e
r
e
d
(
T
&
E
)
te
r
r
e
s
t
r
i
a
l
s
p
e
c
i
e
s
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
,
a
s
s
u
m
i
n
g
n
o
t
e
m
p
o
r
a
r
y
t
r
a
f
f
i
c
by
p
a
s
s
.
1 Alignment shift results in permanent impact to suitable habitat.
Im
p
a
c
t
s
t
o
l
i
s
t
e
d
T
&
E
f
i
s
h
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
1
Fi
s
h
a
c
c
e
s
s
n
o
t
p
r
o
v
i
d
e
d
.
3
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
,
b
u
t
r
e
q
u
i
r
e
s
m
a
i
n
t
e
n
a
n
c
e
f
o
r
en
s
u
r
i
n
g
l
o
n
g
-
t
e
r
m
e
f
f
e
c
t
i
v
e
n
e
s
s
.
5
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
.
5 Fish access restored.
Im
p
a
c
t
t
o
u
p
l
a
n
d
h
a
b
i
t
a
t
(L
e
a
s
t
5
;
m
o
s
t
1
)
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
.
5
No
n
e
e
x
p
e
c
t
e
d
.
5 None expected.
Im
p
a
c
t
s
t
o
W
e
t
l
a
n
d
s
a
n
d
W
a
t
e
r
s
o
f
t
h
e
U
.
S
.
(L
e
a
s
t
5
;
m
o
s
t
1
)
3
La
r
g
e
w
a
s
h
o
u
t
c
o
u
l
d
i
n
c
r
e
a
s
e
t
u
r
b
i
d
i
t
y
a
n
d
se
d
i
m
e
n
t
a
t
i
o
n
.
3
La
r
g
e
w
a
s
h
o
u
t
c
o
u
l
d
i
n
c
r
e
a
s
e
t
u
r
b
i
d
i
t
y
a
n
d
se
d
i
m
e
n
t
a
t
i
o
n
.
3
Re
q
u
i
r
e
s
f
i
l
l
b
e
l
o
w
O
H
W
.
5 None expected.
I m pa
c
t
t
o
D
e
s
i
g
n
a
t
e
d
W
i
l
d
e
r
n
e
s
s
a
r
e
a
(L
e
a
s
t
5
;
m
o
s
t
1
)
0
No
n
e
e
x
p
e
c
t
e
d
.
0
No
n
e
e
x
p
e
c
t
e
d
.
0
No
n
e
e
x
p
e
c
t
e
d
.
0 None expected.
Po
t
e
n
t
i
a
l
f
o
r
H
o
h
R
i
v
e
r
E
n
h
a
n
c
e
m
e
n
t
(G
r
e
a
t
e
s
t
5
;
L
e
a
s
t
1
)
1
Fi
s
h
a
c
c
e
s
s
n
o
t
p
r
o
v
i
d
e
d
.
3
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
,
b
u
t
r
e
q
u
i
r
e
s
m
a
i
n
t
e
n
a
n
c
e
f
o
r
en
s
u
r
i
n
g
l
o
n
g
-
t
e
r
m
e
f
f
e
c
t
i
v
e
n
e
s
s
.
5
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
.
5 Fish access restored.
Po
t
e
n
t
i
a
l
t
o
m
a
i
n
t
a
i
n
o
r
i
m
p
r
o
v
e
r
i
v
e
r
p
r
o
c
e
s
s
a
n
d
fu
n
c
t
i
o
n
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
3
Co
n
s
t
r
a
i
n
e
d
c
h
a
n
n
e
l
r
e
d
u
c
e
s
d
e
b
r
i
s
p
a
s
s
a
g
e
.
5
Ch
a
n
n
e
l
l
e
s
s
c
o
n
s
t
r
a
i
n
e
d
.
5 Channel not constrained.
Po
t
e
n
t
i
a
l
f
o
r
o
t
h
e
r
h
a
b
i
t
a
t
e
n
h
a
n
c
e
m
e
n
t
s
(M
o
s
t
5
;
L
e
a
s
t
1
)
1
Fi
s
h
a
c
c
e
s
s
n
o
t
p
r
o
v
i
d
e
d
.
3
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
,
b
u
t
r
e
q
u
i
r
e
s
m
a
i
n
t
e
n
a
n
c
e
.
5
Fi
s
h
a
c
c
e
s
s
r
e
s
t
o
r
e
d
.
5 Fish access restored.
Po
t
e
n
t
i
a
l
p
r
i
v
a
t
e
p
r
o
p
e
r
t
y
i
m
p
a
c
t
s
(L
e
a
s
t
5
;
M
o
s
t
1
)
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
.
5
No
e
x
p
e
c
t
e
d
a
d
d
i
t
i
o
n
a
l
i
m
p
a
c
t
s
.
3
Sh
i
f
t
i
n
r
o
a
d
a
l
i
g
n
m
e
n
t
t
o
c
o
n
s
t
r
u
c
t
n
e
w
c
u
l
v
e
r
t
ma
y
r
e
q
u
i
r
e
t
e
m
p
o
r
a
r
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Date: 3/14/2013
By: S. Leon
Flood
Frequency
(yr)
Exceedance
Probability
Flood
Damage
Average
Flood
Damage
Delta
Exceedance
Probability
Annual Risk
Cost
No debris removal.2 0.5 $0
$0 0.3 $0
No debris removal.5 0.2 $0
$0 0.1 $0
No debris removal.10 0.1 $0
$10,000 0.06 $600
Debris removal.25 0.04 $20,000
$20,000 0.02 $400
Debris removal.50 0.02 $20,000
$20,000 0.01 $200
Debris removal.100 0.01 $20,000
$2,210,000 0.008 $17,680
Replace bridge.500 0.002 $4,400,000
$18,880
$0
Disc. rate, i 0.07125 Serv. life, n 50 CFR 0.0736
$0
Total Expected Cost (Annual)$18,880
Summary
Notes:
1. Method from HEC-17, April 1981.
Table C5-2. Total Expected Cost
Project: Hoh River Road Bank Erosion Risk Study
Site: C5 - Canyon Creek Culvert
Alternative: Continue Maintenance
Total Annual Risk Cost
Annualized Capital
Cost
Capital Cost
Annualized Capital Cost
Assumes debris removed for flood events larger than 25-year and road embankment is
washed out and new bridge installed for 500-year.
Upper Hoh Road - Bank Failure Risk Reduction Study
p 91
Table C5-3. Cost Estimates
Site:
180 Feet Long Bridge
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 183,773$ 183,773$
New Road LF 1,000 500$ 500,000$
Hillside Stabilization LS 1 50,000$ 50,000$
Flow Diversion LS 1 20,000$ 20,000$
Excavation CY 3,000 30$ 90,000$
180 feet Bridge LS 1 1,840,000$ 1,840,000$
Riprap H 10 ft T 5 ft CY 696 180$ 125,333$
L 160 ft SS 1.75 (h):1(v)
TW 6 ft TT 5 ft
Total Construction Cost without Contingencies 2,809,107$
Contingency 30% of construction cost 842,732$
Total Construction Cost 3,651,839$
Compliance 5% of total construction cost 182,592$
Predesign/design (PE)15% of total construction cost 547,776$
Construction Engineering (CE)15% of total construction cost 547,776$
ROW 20,000$
TOTAL Capital Cost Cost/Foot 27,500$ 4,949,982$
Annualized Capital Cost Discount rate, i 0.07125 364,354$
Service life, n 50 years
CFR 0.0736071
Rock Weirs at Culvert Outlet
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 19,756$ 19,756$
Flow Diversion LS 1 20,000$ 20,000$
Access pad - place/remove/reclaim LS 1 40,000$ 40,000$
Weirs W 8 ft T 6 ft CY 444 500$ 222,222$
L 250 ft
Total Construction Cost without Contingencies 301,978$
Contingency 30% of construction cost 90,593$
Total Construction Cost 392,571$
Compliance 5% of total construction cost 19,629$
Predesign/design (PE)15% of total construction cost 58,886$
Construction Engineering (CE)15% of total construction cost 58,886$
ROW 10,000$
TOTAL Capital Cost 539,971$
Annualized Capital Cost Discount rate, i 0.07125 39,746$
Service life, n 50 years
CFR 0.0736071
C5 - Canyon Creek Culvert
Upper Hoh Road - Bank Failure Risk Reduction Study
p 92
Table C5-3. Cost Estimates
New Open-bottom Culvert
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 51,921$ 51,921$
Flow Diversion LS 1 20,000$ 20,000$
Excavation/backfill CY 5,400 50$ 270,000$
Culvert - 22 feet by 11 feet open-bottom arch LF 160 1,800$ 288,000$
Conc. H 12 ft T 1 ft CY 142 600$ 85,333$
Foot L 320 ft
Concrete headwall/collar EA 2 20,000$ 40,000$
Riprap H 6 ft T 6 ft CY 213 180$ 38,400$
L 160 ft
Total Construction Cost without Contingencies 793,655$
Contingency 30% of construction cost 238,096$
Total Construction Cost 1,031,751$
Compliance 5% of total construction cost 51,588$
Predesign/design (PE)15% of total construction cost 154,763$
Construction Engineering (CE)15% of total construction cost 154,763$
ROW -$
TOTAL Capital Cost Cost/Foot 8,705$ 1,392,864$
Annualized Capital Cost Discount rate, i 0.07125 102,525$
Service life, n 50 years
CFR 0.0736071
Upper Hoh Road - Bank Failure Risk Reduction Study
p 93
(Page left blank.)
Upper Hoh Road - Bank Failure Risk Reduction Study
p 94
Upper Hoh River Road Project October 2017
Clean Water Act Section 404 (b) (1) Evaluation
Attachment B
Upper Hoh River Road Bank Stabilization
Habitat Preservation Mitigation
Draft Hydraulics Report
September 7, 2017
Memorandum
Western Federal Lands Highway Division
610 E. Fifth Street
Vancouver, WA 98661-3801
UPPER HOH RIVER ROAD BANK STABILIZATION
HABITAT PRESERVATION MITIGATION
DRAFT - HYDRAULICS REPORT
To: Kirk Loftsgaarden, WFLHD Project Manager
From: Sven Leon, P.E., WFLHD Hydraulics Engineer
Date: September 7, 2017
Project: Upper Hoh River Road Bank Stabilization – WA JEFF 91420(1)
Background
One of the major roads leading into Olympic National Park (Park), Washington, is the Upper Hoh Road
located off of US Highway 101 on the far western side of Olympic National Park. The road is the only
entryway into the Hoh Rain Forest and the Park Rain Forest Visitor Center. The Upper Hoh Road is
approximately 18 miles in length. Jefferson County (County) owns and maintains the portion of the road
from the junction with US 101 to the OLYM boundary, approximately 12 miles. The Park owns and
maintains the remaining 6 miles.
Management of the road to provide constant safe access to residents, business, and Park visitors, has
become increasingly difficult over the past 20 years. Portions of the Upper Hoh Road are located within
and adjacent to the Hoh River’s channel migration zone. The location combined with the increasing
frequency and severity of winter storm events (most recently in 2004, 2006, 2007, and 2009) has resulted
in an increasing number of roadway washouts which either completely prevents access or creates unsafe
roadway conditions for visitors, Park personnel, and local residents. In some cases the damage resulted in
road closures, allowing no access to the Hoh Rain Forest and the Park’s Hoh Rain Forest Visitor Center
for weeks at a time (and many months in 1996). Response to these storm events and maintenance of the
road in its current location has resulted in a continuing outlay of limited maintenance funds to maintain
safe access and to mitigate for adverse impacts those actions have on threatened and endangered fish
species.
In 1998 the Hoh Tribe requested the U.S. Bureau of Reclamation (BOR) prepare a geomorphic study to
better understand the existing and historical channel processes on the Hoh River, and how human
activities may have impacted those processes. The study, entitled Geomorphic Assessment of Hoh River
in Washington State, published in 2004, identifies areas of risk for further lateral erosion in the historic
channel migration zone and provided some general management considerations to deal with these areas of
concern. The report recommended more detailed data collection and analysis for developing a
management approach at any specific particular location.
In 2009, the Park published a report entitled Olympic National Park, Road Hazards and Solutions Report.
This report examined two methods to address roadway locations, vulnerable to damage from severe storm
events, within the Park. The two different methods evaluated included a site-specific approach versus a
natural systems engineering approach. The report concluded that a natural systems engineering approach
would likely provide a more long-term fix while improving the ecological conditions. Six sites along the
Upper Hoh River Road within the Park were included in this evaluation.
2
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
September 2013 Western Federal Lands Highway Division (WFLHD) completed for the County an
Upper Hoh Road Bank Failure Risk Reduction Study. The Study developed a comprehensive road
management strategy for mitigating high risk sites along the Upper Hoh Road. WFLHD used the
information from the two earlier reports and from site visits for developing the road management strategy.
The WFLHD study included the prioritization of sites (regardless of management jurisdictions),
development of a range of treatment options for each site, and initial cost estimates for each option
including construction, Preliminary Engineering (PE), Construction Engineering (CE), and ROW.
Treatment options developed represented a full range of types, costs, and environmental impacts. All
treatment options where expected to provide a similar level of road failure risk reduction.
Selection and refinement of treatment options were completed March 2016 for two sites, road mile post
(MP) 3.7 to 4.1 (MP 4.0 Site) and MP 7.7 to 7.9 (MP 7.8 Site) (Fig. 1). The County selected these sites
for the project as having the highest priority for needing bank stabilization.
Two bank stabilization design options were evaluated;
Stream barbs with mitigation logs.
Wood buffer with dolosse ballast.
MP 4.0 Site has 2,570 feet of proposed bank stabilization. MP 7.8 Site has 500 feet of proposed bank
stabilization. Each design options was evaluated on controlling bank erosion, cost, disrupting existing
habitat, reducing flow velocity, preserving stream processes, and minimizing private property impacts.
Based on the hydraulic analysis and cost estimates, installation of wood buffer with dolosse ballast was
recommended for both sites. The design approach is the least expensive for effectively controlling bank
erosion. The wood buffer can accommodate a greater range of active flow channel migration and flow
impingement angles. The minimal channel bed excavation and ability to place the wood and dollose
directly into flowing water is least disruptive to environment. The approach does not appear to noticeably
increase flooding or bank erosion on private property adjacent to the project sites. It does not appear to
negatively affect stream processes. The wood buffer provides the greatest flow velocity reduction and
habitat complexity. The approach is most adaptable to changing field conditions.
WFLHD is currently developing final designs and construction contract documents for the wood buffer
with dolosse ballast bank stabilization. In the environmental permit application phase, the resource
agencies identified placing the wood buffer in the river channel as causing negative impacts to fish and
aquatic habitat.
Washington Department of Fish and Wildlife (WDFW) has identified high-value backchannel aquatic
habitat immediately downstream of MP 7.8 site (Fig. 2). Frequent channel migration and avulsions limits
the extent and permanency of high-value backchannel aquatic habitat. Recommendations for improving
the backchannel aquatic habitat survivability by reducing the channel migration and avulsion risk and
encouraging natural floodplain roughness to develop are presented. The work is proposed as mitigation
for the project’s environmental impacts.
Recommendations
Increasing the floodplain roughness along the floodplain boundary is recommended for protecting the
backchannel aquatic habitat and encouraging future tree growth. Backchannel aquatic habitat is created
when the channel migrates or avulses, leaving water-filled pools that are isolated from the main river flow
(Photos 1, 2, 3, 4, and 5). They persist when alder and conifer trees can colonize in sufficient numbers
3
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
and grow large enough to create a high floodplain roughness that inhibits channel migration and avulsion
(Photos 6 and 7). Most of the site floodplain area has only sparse small willows and alder trees (Photos 8
and 9). The trees will not provide enough floodplain roughness for resisting expected channel migration
and avulsion. If left to grow, the trees will likely provide adequate natural resistance. Large woody
debris lining the active channel edge deflects high velocity flow away from overbank areas, reducing the
overbank flow velocity, increasing fine grained sediment deposition, and allowing alder and conifer trees
to grow (Photos 10 and 11). To simulate the large woody debris that lines the bank, install twenty-four
wood plugs at the head of flood scour channels near the active channel edge (Sheets H.1, H.2, H.3, and
H.4).
Each wood plug consists of four log bundles and five rootwads (Sheet H.5). The log bundles are made of
three logs, 20 to 22 feet long, 18 to 37 inches in diameter, total log volume 110 to 150 ft3, and without
attached rootwads. Each log bundle is wrapped with a steel chain. Each rootwad is 20 to 22 feet long, 18
to 37 inches in diameter, and has an attached rootwad. The rootwads will be placed on top of the log
bundles with rootwad in the upstream direction. Each channel plug will have 12 log piles and 8
Cottonwood boles evenly spaced along the downstream side of the log bundles for increasing slippage
resistance. Log piles are 20 feet long, 12 to 18 inches in dimeter, and 15 feet embedment. Set the log pile
top 5 feet above the floodplain ground surface (100-year flood flow depth). Cottonwood boles are 10 feet
long, 12 to 18 inches in dimeter, and 5 feet embedment. Embed the log piles and cottonwood boles with a
track hoe-mounted vibratory hammer. Each channel plug is covered with coarse woody debris; even
mixture of branches, limbs, trunks, and vegetation.
Initial placement of the log bundles and logs with root wads should be as shown on Sheet H.5.
Orientation is critical for deflecting flow away from the overbank area and achieving channel plug
stability. Care must be taken to pack bundles as densely as possible and to place the bottoms in close
contact with the floodplain ground surface for effectively controlling erosion under the bundles.
Do not remove or modify the existing vegetation and large woody debris lining the active channel edge
(Photo 12). A 20 feet wide temporary construction access road is proposed constructed approximately
200 feet from the active river channel edge for minimizing disturbance of the vegetated floodplain.
Install the channel plugs on the side of the road nearest the river. Plant the temporary access road with
Douglas fir trees and cottonwood/willow poles. Do not disturb the existing vegetation between the
temporary construction access road and active channel edge.
Stream Processes Impacts
The wood channel plugs are not intended to prevent water from flowing from the river to the backchannel
aquatic habitat. They are also not intended to manipulate the river flow in a way that unnaturally deflects
the river flow towards a bank. The wood channel plugs increase roughness at strategic locations along the
edge of the wooded floodplain. HECRAS 5.0 modeling results for the proposed 2-year flood flow
velocities and flow depths were used to help define the strategic locations at the head of flood scour
channels (Fig. 3 and 4). The results indicate the flow will be maintained to the aquatic backchannel
aquatic habitat.
Modeling results for the 100-year flood flow velocities and flow depths are presented in Figures 5, 6, 7,
and 8. A velocity profile plot 15 feet behind the wood channel plug alignment shows a decrease in flow
velocity behind each channel plug and an increase between the channel plugs (Fig. 9). Higher flow
velocities along the wood channel plugs sides will scour the floodplain surface materials, creating new
flood scour channels. Scoured material will be deposited on the floodplain gravel bars, building their
elevation. A depth profile plot shows only a 0.2 to 1 foot decrease in flow depth behind the channel plugs
(Fig. 10). Close-up plots are shown in Figures 11 and 12. They show how the overbank flow is deflected
4
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
around the wood channel plugs and where the flow velocity increases occur. The results indicate flow
velocity and flow depth is reduced in the sparsely vegetated floodplain area. This should help encourage
natural vegetation growth.
A 100-year flood flow velocity profile plot along the right (looking downstream) bank line immediately
in front of the wood channel plugs shows an increase in less than 0.5 feet/sec for the proposed conditions
(Fig. 13). A 100-year flood flow depth profile plot shows an increase in less than 0.2 feet for the
proposed conditions (Fig. 14). The results indicate flow depths and velocities in the active channel and
along the floodplain limit for the modeled proposed conditions will not be significantly different from
existing conditions.
Bank erosion occurs when the active flow channel migrates to the valley sides and directs flow at sharp
angles against erodible banks. Woody debris and gravel bars affect channel migration and flow
impingement angles. The wood channel plugs are not expected to restrict sediment and woody debris
transport and recruitment relative to existing conditions. Mid-channel and floodplain sediment deposition
is not expected to be noticeably different than current trends. Current natural active channel migration
and bank erosion levels beyond the proposed habitat preservation is expected to continue.
The wood channel plugs are intended to inhibit bank erosion and channel avulsion along the wooded
floodplain, not prevent them. Aggressive bank migration or full channel avulsion is still possible when
enough sediment or large woody debris is deposited in the active channel to deflect the river flow towards
the habitat preservation area. Entangling enough woody debris on the channel plugs to encroach into the
active channel is possible. The channel plug could become large enough to deflect flow towards the left
bank, significantly increasing the bank erosion.
Installing the wood channel plugs requires minor excavation into the floodplain gravel bar surface. No
flow diversion or work area dewatering is needed.ve. Turbidity release is expected to be limited in extent
and duration. Access for construction is assumed down forest road and temporary construction access
road.
Private Property Impacts
A 100-year flood flow velocity profile plot along the left bank line shows an increase in less than 0.2
feet/sec for the proposed conditions (Fig. 15). A 100-year flood flow depth profile plot shows an increase
in less than 0.2 feet for the proposed conditions (Fig. 14). Based on the HECRAS modeling, the wood
channel plugs are not expected to noticeably increase flooding or bank erosion on private property
adjacent to the project site above current levels. Woody debris entangling on the channel plugs and
encroaching into the active channel could deflect flow towards the left bank, significantly increasing the
bank erosion.
Site Conditions
The river is braided with dramatically shifting active flow channels. Bank erosion is observed at all bank
areas not protected by riprap revetments, heavy vegetation, or boulder lag deposits. The bank erosion is
caused by mid-channel sediment deposits and woody debris shifting across the braid plain and redirecting
flood flows at unstable bank areas. Erosion is severest where flow is directed at sharp angles against an
erodible bank. Large woody debris appears to play a significant role in deflecting and redirecting flood
flows. Cobbles and small boulders naturally armoring the toe and large trees growing in the stream bank
inhibits the bank erosion.
5
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
The habitat preservation site is 2,000 feet downstream from the MP 7.8 Bank Stabilization Site and
occupies a wooded floodplain area on the inside bank of a river bend (Fig. 2). Based on historical
satellite imagery (Google Earth, 1994, 2006, 2009, 2011, 2013, and 2016), the area has experienced
aggressive channel avulsions. The latest avulsion occurred between 2006 and 2009 when a relatively
consistent down-valley channel translation abruptly avulsed into a new channel, leaving the old channel
as new aquatic backchannel habitat (Photos 1, 2, 3, 4, and 5). The active channel near the habitat
preservation site has remained relatively unchanged since the avulsion.
The aquatic backchannel habitat is best preserved where the floodplain vegetation is oldest and has
become large and densely-spaced enough for resisting channel migration and avulsion (Photos 6 and 7).
Large woody debris lining the bank also help deflect overbank flow from floodplain area, slowing flow
velocities and allowing sediment deposition and abundant large diameter tree growth (Photos 10 and 11).
Areas with smaller, sparsely spaced vegetation is at greater risk of experiencing aggressive bank erosion
and a channel avulsion (Photos 8 and 9).
An erosion resistant poorly consolidated alluvium terrace deposit limits river bend migration to the north.
The terrace deposit represents the HCMZ right boundary. Width of the HCMZ is approximately 2,500
feet. The Upper Hoh River Road embankment coincides with the HCMZ right boundary. Upstream the
active channel width is 300 to 600 feet. Downstream width is 500 to 700 feet. At the site the width is
300 to 500 feet. Sand, gravel, and small boulders comprise the stream bed material. Gradation analysis
indicates the bed material ranges from sands to 12 inches with a D50 of 7 inches.
Analysis
Analysis completed by WFLHD includes hydrologic and two-dimensional hydraulic modeling.
Hydrology
The Hoh River drains the western slope of the Olympic Mountains. The river originates on the slopes
surrounding Mount Olympus and adjacent mountain peaks at an elevation of 7,800 feet (NAVD88) and
flows approximately 41 miles through relatively-wide, moderately high-relief, glacial valleys before
discharging to the Pacific Ocean. Elevations at the MP 7.8 project site and the habitat preservation site is
approximately 300 feet. MP 7.8 site is at river mile 24.6 to 24.9. The habitat preservation site is at river
mile 24.2 to 24.4.
MP 7.8 site and the habitat preservation site drainage area, including Tower Creek, was determined using
USGS StreamStats version 3.0 to be approximately 210.0 mi2. Approximately 70 percent of the
watershed is heavily timbered and 20 percent is exposed bedrock. Four small glaciers, White, Blue, Hoh,
and Hubert, are found in the higher elevations and occupy approximately 7 mi2 (3 percent) of the drainage
area. Only small lakes are present. Mean annual precipitation reported by USGS StreamStats is 168
inches. The watershed lies mostly within the Olympic National Park and Olympic National Forest.
Development is sparse, primarily light rural residential. No diversions for irrigation occur upstream.
The USGS maintains a stream gage station (12041200) on Hoh River, near the State Highway 101
Bridge, river mile 15.4. The gage has 54 years of record, beginning 1961 and ending 2014. Hydrology
for the gage station is presented in Magnitude and Frequency of Floods in Washington: U.S. Geological
Survey Water-Resources Investigations Report 97-4277 (Sumioka, S.S., Kresch, D.L., and Kasnick, K.D.,
1998). Annual peak stream flow for the gage station is presented in Figure XX. The gage station has not
experienced floods greater than the 50-year event. Largest floods of record occurred in 2004 (62,100 cfs)
and 2007 (60,700 cfs). Both were approximately equal to the 25-year flood event.
6
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
Peak flood discharges were estimated with the weighting equation in USGS WRIR 97-4277 for ungagged
sites on gaged streams. Peak discharges for the ungaged sites were estimated using USGS StreamStats
regression equations. The regression equation estimates were then improved by weighting with the
weighted estimates for the USGS 12041200 gage station (Table 2, USGS WRIR 97-4277). Peak
discharge estimates are presented in Table 1.
Maritime weather dominates. Storms and moderate to heavy precipitation occurs year round. Storms are
more frequent and precipitation is heavier September through January. September through November
have the heaviest recorded rainfall. Snow occurs frequently during winter months, but melts after a few
days. Lowest flows occur in February, March, April, July, and August. Winter season snowfall ranges
from 10 to 30 inches in the lower elevations and between 250 to 500 inches in the higher mountains. In
the lower elevations, snow melts rather quickly and depths seldom exceed 6 to 15 inches. In midwinter,
the snowline is between 1,500 and 3,000 feet above sea level. The higher ridges are covered with snow
from November until June.
Hydraulic Modeling
Water surface elevations and flow velocities were estimated using the Hydrologic Engineering Center
River Analysis System HEC-RAS 5.0, a computer program that performs two-dimensional unsteady
steady flow calculations. Two–dimensional flow models provide a more thorough understanding of how
the design options effect water surface elevations and flow velocities.
WFLHD developed HEC-RAS 5.0 flow models for the existing conditions and proposed design options.
LIDAR terrain data was obtained from Puget Sound LIDAR Consortium. The LIDAR mapping was
surveyed April 14 and 21, 2012. The LIDAR data does not have topography of the channel bed beneath
the water surface and cannot be used directly to accurately model flow conditions. WFLHD surveyed
topography and cross sections of the river channel at the MP 7.8 bank stabilization site. Terrain data was
developed for the existing condition models by merging the LIDAR terrain data with the surveyed river
cross sections and ground topography data. Each channel plug was placed in the model at design
locations. The blocking effect of the channel plugs were simulated by assigning a Manning’s Roughness
Coefficient to the channel plug areas of 10.
Meshes with 10 feet by 10 feet grid spacing encompassing the flow areas were generated for each model.
Floodplains and areas with higher flow roughness were delineated on the meshes from aerial imagery.
Floods occurring 2004 and 2006 approximately equaled the 25-year event. Existing condition model was
calibrated by adjusting the Manning’s Roughness Coefficients until the 25-year flood flow water surfaces
approximately equaled observed high water marks and debris limits. Manning’s Roughness Coefficient
of 0.040 was selected for the main channel 2D flow areas. Manning’s Roughness Coefficient of 0.15 was
selected for the floodplain areas. Figure 17 shows the two-dimensional model setup. Normal flow depth
with 0.01 feet/feet friction slope was set for the downstream boundary condition. A 10-hour duration, 1-
minute interval hydrograph, stepping through the 2, 10, 25, 50, and 100-year flood flows was used for the
upstream boundary condition. Each model uses the full momentum equation set, 15 second computation
interval, and 2-hour initial condition time.
Predicted 2-year flood flow velocities are presented in Figure 3. Predicted 2-year flood flow depths are
presented in Figure 4. Predicted 100-year flood flow velocities are presented in Figures 5, 6, and 11.
Predicted 100-year flood flow depths are presented in Figures 7, 8, and 12. The 100-year flood flow
velocities and flood flow depths were used for designing the channel plug features and evaluating
potential effect on stream processes. Differences between the existing condition and proposed habitat
preservation models for the 100-year flood flow velocities and flood flow depths are presented in Figures
9, 10, 13, 14, 15, and 16. The 100-year flood flow velocity and flood flow depths differences help
7
Memo to: Kirk Loftsgaarden, WFLHD Project Manager
September 7, 2017
identify potential private property flooding, private property bank erosion, and natural stream processes
impacts.
Floodplain and Flood-rise Limitations
Executive Order 11988, Floodplain Management, established federal policies for protecting floodplains
and floodways. The intention of the associated regulations is to avoid, to the extent practical, adverse
impacts to floodplains; minimize the impact of floods to human safety, health, and welfare; and avoid
supporting land use development that is incompatible with the natural and beneficial floodplain values.
When avoidance is not possible, the policies require appropriate consideration of methods to minimize
adverse impacts.
The sites are located within Zone A identified on the Federal Emergency Management Agency (FEMA)
Flood Insurance Rate Map (FIRM) 5300690600B and 5300690625B. Zone A is an area of 100-year
flood not determined. Jefferson County is the local floodplain administrator. Both federal and local
regulations require increases in the 100-year water surface elevation for Zone A to be less than one foot.
Cost Estimates
Construction cost estimates are provided in Table 2. Assumed stabilization length is 1,900 feet.
Temporary construction access road is 3,500 feet long. The estimates assume logs with root wads cost
$1,100 and logs without root wads cost $600 each. Flow diversion is assumed not needed. The costs
presented include 7 percent mobilization and 10 percent contingency.
attachments: Tables 1 and 2
Figures 1 to 17
Site Photographs 1 to 12
Sheets H.1 to H.5
Estimate Drainage Annual
Method Area (mi2) Precip 2 10 25 50 100
MP 7.8 ‐ Streamstats 210 170 28,400 44,700 52,500 59,300 66,700
USGS 12041200 PEAKFQ 32,660 52,390 61,460 67,890 74,060
USGS 12041200 Tab. 2 32,200 51,100 59,700 65,700 71,400
weighted Tab.2 32,000 51,000 59,600 65,700 71,200
MP 7.8 ‐ Design 210 26,960 42,968 50,213 55,352 59,986
Notes:
1. USGS - USGS Regression Equations, “Magnitude and Frequency of Floods in Washington”,
WRIR 97-4277, 1998.
Table 1. Peak Discharges (ft3/sec)
Recurrence Intervals (years)
Table 2. Cost Estimates
Site:
Wood Fence with Slash Stabilization Length 1900 feet
Unit Quantity Unit Cost Total Cost
Mobilization 7% of construction cost LS 1 42,224$ 42,224$
Remove Existing Revetment LF - -$ -$
Flow Diversion LS 1 5,000$ 2,000$
Wood Buffer
Exc./Place Conserved SBM CY 480 8$ 3,840$
18" dia. X 20' Logs w/out rootwads EA 288 600$ 172,800$
18" dia. X 20' Logs w/ rootwads EA 120 1,100$ 132,000$
Chain, 5/8" HDG Grade 43 FT 1,920 10$ 19,200$
18" dia. X 20' Log Piles EA 288 700$ 201,600$
18" dia. X 10' Cottonwood Boles EA 192 200$ 38,400$
Pole-plantings, cottonwood EA 240 4$ 960$
Pole-plantings, willow EA 3,600 2$ 7,200$
Coarse Woody Debris CY 1,680 15$ 25,200$
Per ELJ Unit
ELJ Width 80 feet
ELJ Unit No. 24
Exc./Place Conserved SBM 20 CY
18" dia. X 20' Logs w/out rootwads 12 No. 3 per
18" dia. X 20' Logs w/ rootwads 5 No.
18" dia. X 20' Log Piles 12 No. 3 per
18" dia. X 10' Cottonwood Boles 8 No. 2 per
Chain, 5/8" HDG Grade 43 80 feet 20 per
Log Bundles 4 No.
Pole-plantings, cottonwood 10 No.
Pole-plantings, willow 150 No.
Coarse Woody Debris 70 CY
Cost per ELJ Unit
Total Construction Cost without Contingencies 645,424$
Contingency 10% of construction cost 64,542$
Total Construction Cost 709,966$
CE and PE 30% of construction cost 212,990$
ROW -$
TOTAL Capital Cost Cost/Foot 486$ 922,956$
Annualized Capital Cost Discount rate, i 0.07125 67,936$
Service life, n 50 years
CFR 0.0736071
Habitat Mitigation - Channel Preservation
25,050$
Project Site Locations
Project Area Location
Map printed from National Geographic TOPO
MP 4.0
N
Habitat
Preservation
Site
0 1 mile
FIGURE 1
HABITAT PRESERVATION
SITE LOCATION
MP 7.8
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0
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FIGURE 2 HABITAT PRESERVATION SITE MAP
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N FIGURE
3
PROPOSED CHANNEL PLUGS 2-YR FLOW VELOCITYLeft Bank Floodplain
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N FIGURE
4
PROPOSED CHANNEL PLUGS 2-YR FLOW DEPTHLeft Bank Floodplain
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0 500 feet
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N FIGURE
5
EXISTING CONDITIONS 100-YR FLOW VELOCITYLeft Bank Floodplain
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0 500 feet
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N FIGURE
6
PROPOSED CHANNEL PLUGS 100-YR FLOW VELOCITYLeft Bank Floodplain
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0 500 feet
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N FIGURE
7
EXISTING CONDITIONS 100-YR FLOW DEPTHLeft Bank Floodplain
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0 500 feet
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N FIGURE
8
PROPOSED CHANNEL PLUGS 100-YR FLOW DEPTHLeft Bank Floodplain
Ri
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B
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Ri
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Wo
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a
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P
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s
0 500 feet
Ba
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A
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N FIGURE
9
FLOODPLAIN 100-YEAR FLOW VELOCITY DIFFERENCE
Te
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S
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Mo
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Ri
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Right Bank Floodplain
Do
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Upstream Boundary
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W
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FIGURE
1
0
FLOODPLAIN 100-YEAR FLOW DEPTH DIFFERENCE
We
s
t
E
n
d
East End
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2
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1
2
.
N FIGURE
1
1
PROPOSED CHANNEL PLUGS 100-YR FLOW VEL. CLOSEUPLeft Bank Floodplain
Ri
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F
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Wo
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a
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P
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s
0 300 feet
Ba
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a
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a
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a
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A
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2
1
,
2
0
1
2
.
N FIGURE
1
2
PROPOSED CHANNEL PLUGS 100-YR FLOW DEPTH CLOSEUPLeft Bank Floodplain
Ri
g
h
t
B
a
n
k
F
l
o
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d
p
l
a
i
n
Wo
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d
C
h
a
n
n
e
l
P
l
u
g
s
0 300 feet
Ba
c
k
c
h
a
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l
H
a
b
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t
a
t
A
r
e
a
Ba
c
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c
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a
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H
a
b
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a
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A
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a
N FIGURE
1
3
RIGHT BANK 100-YEAR FLOW VELOCITY DIFFERENCE
Te
r
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a
i
n
S
u
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f
a
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Mo
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G
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L
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s
Le
f
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B
a
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F
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p
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Ri
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B
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k
F
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p
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n
Ri
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B
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Fl
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a
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Ri
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a
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k
F
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d
p
l
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n
Right Bank Floodplain
Do
w
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B
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Upstream Boundary
Ch
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Upstream
Pr
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W
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d
C
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l
P
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N FIGURE
1
4
RIGHT BANK 100-YEAR FLOW DEPTH DIFFERENCE
Te
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S
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Mo
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Right Bank Floodplain
Do
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B
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Upstream Boundary
Ch
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Upstream
Pr
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N FIGURE
1
5
LEFT BANK 100-YEAR FLOW VELOCITY DIFFERENCE
Te
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B
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F
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d
p
l
a
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n
Right Bank Floodplain
Do
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B
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d
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y
Upstream Boundary
Ch
a
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P
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Do
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Upstream
Pr
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N FIGURE
1
6
LEFT BANK 100-YEAR FLOW DEPTH DIFFERENCE
Te
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S
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Right Bank Floodplain
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Upstream Boundary
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.
N FIGURE
1
7
HABITAT PRESERVATION HECRAS 2-D MODEL
Te
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Do
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Upstream Boundary
Wo
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1
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Habitat Preservation Area
PHOTO 1
PHOTO 2
PHOTO 3
2/15/2017
Backchannel aquatic habitat.
Pool formed when river channel avulsed.
Newer habitat, created with 2006
avulsion.
Backchannel aquatic habitat.
Upper Hoh River Road Bank Stabilization
Pool formed when river channel avulsed.
Newer habitat, created with 2006
avulsion.
Pool formed when river channel avulsed.
Newer habitat, created with 2006
avulsion.
Backchannel aquatic habitat.
Habitat Preservation Area
PHOTO 4
PHOTO 5
PHOTO 6
2/15/2017
Backchannel aquatic habitat.
Pool formed when river channel avulsed.
Older habitat, created in earlier
avulsions.
Main bank stabilization site - looking
upstream.
Pool formed when river channel avulsed.
Older habitat, created in earlier
avulsions.
Older floodplain with more established
vegetation.
Trees larger and type varies, ground
surface rougher.
Upper Hoh River Road Bank Stabilization
Habitat Preservation Area
PHOTO 7
PHOTO 8
PHOTO 9
2/15/2017
Older floodplain with more established
vegetation.
Newer floodplain with less established
vegetation.
Trees larger and type varies, ground
surface rougher.
Vegetation smaller with fewer types,
ground surface smoother.
Newer floodplain with less established
vegetation.
Vegetation smaller with fewer types,
ground surface smoother.
Upper Hoh River Road Bank Stabilization
Habitat Preservation Area
PHOTO 10
PHOTO 11
PHOTO 12
2/15/2017
Vegetation lining active channel edge.
Vegetation limits bank erosion and must
be preserved.
Large woody debris lining active channel
edge.
Older, naturally anchored woody debris
deflects flow away from overbank area.
Woody debris protects vegetation on
floodplain. Woody debris and vegetation
limits bank erosion and must be
preserved. Trees smaller and younger.
Large woody debris lining active channel
edge.
Upper Hoh River Road Bank Stabilization
Older, naturally anchored woody debris
deflects flow away from overbank area.
Woody debris protects vegetation on
floodplain. Woody debris and vegetation
limits bank erosion and must be
preserved. Trees larger and older.
OHW
Deflector log bundle
Deflector log bundle
Defector rootwad, 5
Deflector log bundle, 4
DETAILS
CHANNEL PLUG
7.
6.
5.
4.
3.
2.
1.
5
STATE PROJECT
NUMBER
SHEET
]
U
S
_
S
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_
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t
2
D
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:
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s
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p
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n
\
d
0
3
3
2
3
5
4
\
H
.
X
X
_
v
5
_
H
a
b
i
t
a
t
p
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e
s
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_
T
y
p
i
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a
l _
f
l o
o
d
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_
B
S
_
S
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_
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t
2
D
.
d
g
n
WA JEFF 91420(1)
1
2
:
3
6
P
M
1
6
A
u
g
u
s
t
2
0
1
7
-
-
/
-
-
-
-
-
-
/
-
-
-
-
C
h
e
c
k
e
d
b
y
:
D
e
s
i
g
n
e
d
b
y
:
Log pile
space between fill logs and deflector logs.
vegetation, 1-inch to 8-inch diameter, tightly pack into void
Coarse woody debris; even mixture of branches, limbs, trunks,
Deflector log bundle; 110 to 150 ft3 total log volume.
Space log pile and cottonwood boles 4' o.c.
Cottonwood bole; 10-foot min. trunk, 12 to 18-inch diameter.
attached rootwad.
Log pile; 20-foot min. trunk, 12 to 18-inch diameter without
attached rootwad.
Deflector rootwad; 20-foot min. trunk, 18 to 37-inch diameter with
attached rootwad.
Deflector log; 20 to 22-foot trunk, 18 to 37-inch diameter without
NO SCALE
Flow
Wrap each log bundle
trunk with chain
Wrap each log bundle
trunk with chain,
center in log bundle
20'-0"
4
'
m
i
n
.
Do not disturb existing vegetation
Do not disturb
existing vegetation
NOTE:
100-year W.S.
TYPICAL SECTION
Existing channel bottom
over deflector logs
Placed coarse woody debris, min. 1'
A
A
Temporary access road
random spacing
3 per channel plug,
Doug fir planting,
3' random spacing
method,
single group
Pole planting,
Deflector rootwad
DETAIL
TYPICAL DEFLECTOR LOG BUNDLE
80'-0"
PLAN
5
'
m
i
n
.
excavate as needed for setting flush on subgrade
Set deflector log bundle on channel bottom,
1
5
'
m
i
n
.
2'-0"
4'-0"
Log piles, 12 Cottonwood boles, 8