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Home My WebLink AboutAttachment A - Final-UHRBFRS_County-combined-3C1 - 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 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 C1 ‐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 11 ea g v d a f av d f v Fi g u r e C1 ‐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 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 OP T I O N S R a n k Co n t i n u e d M a i n t e n a n c e R a n k Re l o c a t e R o a d R a n k Co m p l e x R o u g h e n e d L a r g e Ro c k T o e R a n k Co m p l e x L o g C r i b W a l l R a n k Ri p r a p w i t h L W D a n d Pl a n t i n g s R a n k Ri p r a p w i t h S t r e a m b a r b s Rank ELJ Groins Rank Large Stream barbs Rank Ro a d o n t h e e d g e o f t h e c h a n n e l m i g r a t i o n zo n e h a s l e s s o f a n i m p a c t t o t h e t o t a l ch a n n e l z o n e . Pl a c e o r r e p l a c e r i p r a p a s ne e d e d f o r p r e v e n t i n g r o a d cl o s u r e . Of f s e t R o a d 2 0 0 F e e t w i t h 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 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 $ 8 , 9 0 2 , 4 0 0 $ 1 , 2 7 6 , 1 6 5 $ 1 , 5 9 5 , 6 3 2 $ 2 , 3 1 1 , 7 9 0 $ 2 , 3 0 9 , 4 7 2 $ 9 , 2 8 9 , 0 9 8 $ 5 , 3 9 9 , 8 6 2 $ 5 , 2 8 5 , 8 0 0 Ri p r a p a n d W o 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 $ 3 4 9 , 8 0 0 $ 6 9 2 , 5 3 3 $ 5 0 5 , 2 6 7 $ 3 7 7 , 7 3 3 $ 4 , 4 8 8 , 0 0 0 $ 4 8 8 , 4 0 0 $ 3 , 0 0 0 , 0 0 0 To t a l C a p i t a l C o s t ( 5 0 y e a r s ) N A $ 1 3 , 6 9 8 , 2 4 0 $ 2 , 0 7 2 , 6 2 3 $ 2 , 8 4 6 , 6 3 6 $ 3 , 6 2 6 , 1 8 4 $ 3 , 4 9 5 , 5 2 1 $ 1 7 , 0 2 8 , 2 8 2 $ 7 , 7 7 8 , 2 1 4 $ 1 0 , 1 3 5 , 8 3 0 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 ; Mo s t 1 ) $2 1 , 0 0 0 $1 , 0 0 8 , 2 8 8 $1 5 2 , 5 6 0 $2 0 9 , 5 3 3 $2 6 6 , 9 1 3 $257,295 $1,253,402 $572,532 $746,069 SC O R E 44 43 52 48 52 50 48 52 44 Ta b l e C 1 - 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 1 - M P 3 . 7 - 4 . 0 B a n k S t a b i l i z a t i o n Ba n k S t a b i l i z a t i o n 51 3 3 3 3 1 11Minor Active River Channel Shift M a j o r A c t i v e R i v e r C h a n n e l S h i f t 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 n St u d y 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 (Page left blank.) 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 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 C2 ‐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 33 ea g v d a f av d f v Fi g u r e C2 ‐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 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 T I O N S R a n k Co n t i n u e d M a i n t e n a n c e R a n k Re l o c a t e R o a d R a n k Co m p l e x R o u g h e n e d L a r g e Ro c k T o e R a n k Co m p l e x L o g C r i b W a l l R a n k Ri p r a p w i t h L W D a n d Pl a n t i n g s R a n k Ri p r a p w i t h S t r e a m b a r b s Rank ELJ Groins Rank Large Stream barbs Rank Ro a d o n t h e e d g e o f t h e c h a n n e l m i g r a t i o n zo n e h a s l e s s o f a n i m p a c t t o t h e t o t a l ch a n n e l z o n e . Pl a c e o r r e p l a c e r i p r a p a s ne e d e d f o r p r e v e n t i n g r o a d cl o s u r e . Of f s e t R o a d 2 0 0 F e e t - in s t a l l s t r e a m b a r b s a n d EL J ' s f o r p r e s e r v i n g r i p a r i a n zo 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 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 3 , 7 3 0 Ri p r a p a n d W o o d R e p l a c e m e n t ( 5 0 y e a r s ) N A $ 6 2 4 , 0 0 0 $ 1 1 5 , 5 0 0 $ 2 2 8 , 6 6 7 $ 1 6 6 , 8 3 3 $ 1 1 9 , 6 6 7 $ 5 9 8 , 4 0 0 $ 7 4 , 6 4 0 $ 1 , 8 0 0 , 0 0 0 To t a l C a p i t a l C o s t ( 5 0 y e a r s ) N A $ 3 , 2 4 6 , 6 5 5 $ 5 7 1 , 9 2 2 $ 9 0 2 , 6 0 6 $ 1 , 1 9 9 , 1 2 9 $ 1 , 0 2 8 , 3 3 7 $ 2 , 5 6 7 , 1 3 8 $ 1 , 3 3 8 , 8 0 9 $ 5 , 6 1 2 , 0 3 6 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 ; Mo s t 1 ) $4 5 , 0 0 0 $2 3 8 , 9 7 7 $4 2 , 0 9 8 $6 6 , 4 3 8 $8 8 , 2 6 4 $75,693 $188,960 $98,546 $413,086 SC O R E 44 43 52 48 52 50 48 52 44 Ta b l e C 2 - 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 2 - M P 4 . 4 B a n k S t a b i l i z a t i o n Ba n k S t a b i l i z a t i o n 51 3 3 3 3 1Minor Active River Channel Shift 11Major Active River Channel Shift 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 n St u d y p 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 n St u d y p 55 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)$40,300 Summary Notes: 1. Method from HEC-17, April 1981. Table C3-2. Total Expected Cost Project: Hoh River Road Bank Erosion Risk Study Site: C3 - Tower Creek Bridge Alternative: Continue Maintenance Total Annual Risk Cost Annualized Capital Cost Capital Cost Annualized Capital Cost Assume bridge is replaced for 100-year and larger flood events. Upper Hoh Road - Bank Failure Risk Reduction Study p 56 Table C3-3. Cost Estimate Site: 130 Feet Long Bridge Unit Quantity Unit Cost Total Cost Mobilization 7% of construction cost LS 1 117,880$ 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 p 57 C4 - COUNTY MILEPOST 7.8 BANK STABILIZATION Upper Hoh Road - Bank Failure Risk Reduction Study p 58 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 p 59 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 p 60 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 p 61 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 p 62 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 p 63 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 p 64 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 p 65 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. Upper Hoh Road - Bank Failure Risk Reduction Study p 66 (Page left blank.) Upper Hoh Road - Bank Failure Risk Reduction Study p 67 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 C4 ‐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 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 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 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 T I O N S R a n k Co n t i n u e d M a i n t e n a n c e R a n k Re l o c a t e R o a d R a n k Co m p l e x R o u g h e n e d L a r g e Ro c k T o e R a n k Co m p l e x L o g C r i b W a l l R a n k Ri p r a p w i t h L W D a n d Pl a n t i n g s R a n k Ri p r a p w i t h S t r e a m b a r b s Rank ELJ Groins Rank Large Stream barbs Rank Ro a d o n t h e e d g e o f t h e c h a n n e l m i g r a t i o n z o n e ha s l e s s o f a n i m p a c t t o t h e t o t a l c h a n n e l z o n e . Pl a c e o r r e p l a c e r i p r a p a s ne e d e d f o r p r e v e n t i n g r o a d cl o s u r e . Of f s e t R o a d 2 0 0 F e e t w i t h 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 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 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 ) 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 t o 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 ) 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 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 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 0 2 $ 4 , 0 3 3 , 9 0 0 Ri p r a p a n d W o 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 $ 3 8 1 , 3 3 3 $ 2 8 2 , 6 6 7 $ 2 , 9 1 7 , 2 0 0 $ 3 3 9 , 9 6 0 $ 1 , 8 0 0 , 0 0 0 To t a l C a p i t a l C o s t ( 5 0 y e a r s ) N A $ 1 1 , 1 6 9 , 4 7 8 $ 1 , 4 1 8 , 5 3 0 $ 2 , 0 7 7 , 8 0 5 $ 2 , 7 0 9 , 1 7 2 $ 2 , 5 1 0 , 3 5 3 $ 1 1 , 5 5 0 , 0 5 2 $ 5 , 5 6 0 , 0 0 7 $ 7 , 2 4 5 , 7 6 5 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 ) $ 2 1 , 0 0 0 $ 8 2 2 , 1 5 3 $ 1 0 4 , 4 1 4 $ 1 5 2 , 9 4 1 $ 1 9 9 , 4 1 4 $ 1 8 4 , 7 8 0 $ 8 5 0 , 1 6 6 $ 4 0 9 , 2 5 6 $ 5 3 3 , 3 4 0 SC O R E 4 4 4 3 5 2 4 8 5 2 5 0 4 8 5 2 4 4 Ta b l e C4 ‐1. Al t e r n a t i v e Su m m a r y an d Ra n k i n g . Up p e r Ho h Ri v e r Ro a d Si t e ‐ C4 ‐ MP 7. 8 Ba n k St a b i l i z a t i o n Ba n k S t a b i l i z a t i o n 51 3 3 3 3 1Minor Active River Channel Shift 11Major Active River Channel Shift 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 n St u d y p 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 (Page left blank.) 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 a t i o n AC M Z 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 y R O W . 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 ) 3 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 . 3 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 . 5 Mi t i g a t e s w a s h o u t r i s k . 5 Mitigates wash out risk. To t a l C o n s t r u c t i o n c o s t NA $3 9 2 , 5 7 1 $1,031,751 $3,651,839 To t a l C a p i t a l C o s t ( 5 0 y e a r s ) NA $5 3 9 , 9 7 1 $1,392,864 $4,949,982 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 ) $1 8 , 8 8 0 $3 9 , 7 4 6 $102,525 $364,354 S C O R E3 44 56 15 6 Ta b l e C5 ‐1. Al t e r n a t i v e Su m m a r y an d Ra n k i n g . Ta b l e C5 ‐1. Al t e r n a t i v e Su m m a r y an d Ra n k i n g . 55 3 1 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 n St u d y p 90 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