HomeMy WebLinkAboutHABITAT MANAGEMENT PLANPoint Whitney Water Access — Habitat Management
Plan
July 26, 2021
Washington Department of Fish and Wildlife
Prepared by Chris Gourley, Environmental Planner
As required by Jefferson County Code (JCC) Chapter 18.22 Critical Areas and 18.25 Shoreline Master
Program, Article VI. Fish and Wildlife Habitat Conservation Areas (FWHCAs) 18.22.650 requires a Habitat
Management Report to be written. In a letter dated April 21, 2021, Department of Community
Development Staff Donna Frostholm requested the following Habitat Management Plan (HMP) to fulfill
the applicant's and County's obligations for review of the outlined project, submitted by Washington
Department of Fish and Wildlife (WDFW) by Chris Gourley, Senior Permitting Planner.
18.22.905 General Requirements
(a) The proposed activity, location and dimensions;
The project is the Point Whitney boat ramp, which is located at 1000 Point Whitney Road in
Brinnon, WA, Jefferson County. From Quilcene, head southwest on US-101 toward Bee Mill
Road and turn left onto Bee Mill Road. Continue on Bee Mill Road to Point Whitney Road and
follow Point Whitney road to site. The primary purpose of this project is to renovate the Point
Whitney boat ramp to address damage to the boat ramp and increase safe user access by
providing a ramp that is accessible to the public. The boat ramp is on the western shoreline of
Dabob Bay in Puget Sound. The existing boat ramp is located on a short section of northward -
facing gravel beach along a coastline that is dominantly east -west oriented. The shoreline
exhibits a left to right drift cell direction and within about 600 ft. west of the boat ramp meets a
divergence zone combining a right to left drift cell and alluvial fan formed by a low energy
lagoon outlet and small tributaries. The boat ramp is located on a barrier spit that is continually
recharged by the gravel and sand supply that moves northerly along Point Whitney Tide Lands
Beach to the east. Incoming tidal action and substantial wave height experienced by North
Puget Sound beaches (Finlayson, 2006) keep importing an abundance of gravel that feeds the
barrier spit (Please see Appendix A, Maps 2-3).
Due to sediment accrual, the Point Whitney boat ramp is currently unsafe or difficult to use for
the public. The proposed project includes installing a new ramp on top of the existing ramp and
associated mitigation. Concrete planks will be overlaid on the existing ramp to form a new,
wider ramp in the same location. Rods will be placed to level and raise the new ramp and voids
will be filled with crushed rock. The new planks are 12 ft. x 4 ft. x 6 in. Existing planks are 10 ft. x
14 in. Four (4) ft. wide articulated concrete mats will be placed on both sides of the ramp and at
the foot to provide erosion control to reduce the risk of undermining the ramp. All concrete is
pre -cast and keyed into the substrate. The ramp will not be above the grade of the beach at
highest use times and will be approximately 6-10 inches above the grade of the current ramp.
The mitigation work includes the previously completed restoration of the western edge of the
"point" at the west side of the project. Parking area and fill was removed to match the existing
grade of vegetation on the site (See Plan Set Sheet 9). The area is expected to revegetate
naturally with grasses and low vegetation. This accounts for roughly 900 square feet of
mitigation above OHW.
In addition, cooperative efforts are underway with the Hood Canal Coordinating Council (HCCC)
to utilize the in -lieu fee program established by local partners and supported by Jefferson
County.
Impacts have been assessed by WDFW and have been proposed to all regulators for this
project. HCCC is awaiting information from the applicant and regulators on the requirements
for mitigation to offset the impacts outlined below. A Use Plan is being drafted and the council
will be provided the plan to consider the mitigation credits to be purchased through the HCCC.
Material
Location
Existing
Existing
New Total
New
Net
Net SF
Dimension
SF
Dimension
Total SF
I Dimension
Increase
Ramp
Above HTL2
25' x 10'
250
25' x 12'
300
2' wider, same
50
Planks'
_
87' x 10'
870
87' x 12'
length
Ramp Planks
Below HTL
1044
2' wider, same
174
length
ACM3
Above HTL
N/A
N/A
25' x 4'
200
25' x 4' x 2
200
x2 (one per side)
ACM
Below HTL
N/A
N/A
87' x 4'
696
87' x 4' x 2
696
x2 (one per side)
Net increase of material below HTL = Ramp 870 SF
Planks + ACM
Net increase of material above HTL = Ramp 250 SF
Planks +ACM
(b) Existing site conditions and property boundaries preferably on a scaled site plan with
structures, features and geographic location described and graphically depicted;
Uplands adjacent to the public access site include forested areas amidst single-family
residences. The beach upland ecotone is nearly continuous -forested or well -vegetated. Within
2 miles of the project area there a few small steep -gradient tributaries creating alluvial fans.
The immediate uplands contain a parking lot partially paved and partially graveled. The paved
area drains out through the boat launch access. There is minor erosion once the surface run-off
engages the beach but does not appear to affect beach habitat.
The shoreline to the south of Point Whitney is dominated by a gravel beach that terminates at
approximately the high tide line in a steep bluff extending to approximately 50 ft. to 80 ft.
above sea level. The average beach slope is 12.5%. Slope increases at the upper portions of the
beach. Substrate size increases down slope. The shoreline exhibits a left to right drift cell
direction and within about 600 ft. west of the boat ramp meets a divergence zone combining a
right to left drift cell and alluvial fan formed by a low energy lagoon outlet and small tributaries.
The material here is relatively coarse, ranging in size from gravel to boulders. The northward
facing beach interacts with an outlet of a tidal lagoon to the west. The material in the lower
portion of the bluffs is relatively resistant interbedded sands and gravels that tilt towards the
north. The shoreline directly adjacent to the boat ramp is documented to be much finer than
the rest of the shoreline.
Results from a wave analysis study conducted by Northwest Hydraulic Consultants indicate that
when offshore winds are from the NNW and N directions, waves reach the shore approximately
head on and result in cross -shore transport. When the offshore winds are from the NE and
southerly directions (SSW, S, and SSE), waves refract and diffract around Point Whitney and
travel along the shore from east to west. When waves approach the shore at an angle, a
' Pre -cast Concrete Planks
z High Tide Line = 12.7 feet above MLLW
s Articulated Concrete Mat
longshore current will be generated. On this shoreline, east to west sediment transport during
the southerly storm event is the dominant factor in the ongoing sand deposition onto the boat
ramp.
Eelgrass and other seagrasses play a key role in the nearshore ecosystem environments by
providing habitat for a wide range of organisms across multiple life stages. Eelgrass beds also
help prevent erosion and increase shoreline stability by anchoring seafloor sediment. Eelgrass is
a federally -designated Essential Fish Habitat (EFH) and a Habitat of Particular Concern (HPC)
under the Magnuson Stevens Fishery Conservation and Management Act of 1996.
GeoEngineers completed a seagrass delineation and identified a continuous eelgrass bed near
the waterward extent of the boat ramp. An additional technical memo was written to
supplement the initial survey after 3 years. Both surveys have been provided to Jefferson
County. In Puget Sound, the maximum depth to which eelgrass grows ranges from
approximately 1.3 m below the low tide line (MLLW) to greater than 9 m deep. At Point
Whitney boat ramp area, the eelgrass beds elevation extent is from -2 ft. to -14 ft. tidal datum.
Quilcene-Dabob Pollution Identification and Correction (PIC), which ran from December 1, 2015
to December 31, 2018, had a goal to restore and protect surface waters for shellfish harvest,
recreational use, and aquatic life habitat. Marine algal blooms can occur in the Dabob Bay and
in 2014 the highest levels of paralytic shellfish poison biotoxins was measured in Washington
oysters. Septic system leakage remains a problem in Hood Canal contributing to nutrient
loading. Sediment quality was measured in 2004 by the Washington State Department of
Ecology as part of the Puget Sound Assessment and Monitoring Program (PSAMP). The areas
closest to Point Whitney were found to be intermediate/high quality and intermediate/low
quality sediments.
Some riprap on site may affect animal migration between upland and the beach. On the back
side of the spit, fencing may affect transient wildlife desiring to migrate between the beach and
lagoon. To a limited extent, openings in the fence accommodate these foraging behaviors. The
foreshore gradient is about 10 —12% towards the upper beach and decreases westward
approaching the lagoon alluvial fan. Upland habitats are generally available through forested
lands that comprise most of the habitat type above MHHW.
The pea gravel/sand mix in the upper tidal elevation of the beach provide ideal spawning
habitat for surf smelt. Herring spawning habitat is documented at the project site and
southward through Point Whitney Tideland Beach. The eelgrass beds provide a key substrate
for herring spawn.
Shoreline is rock/gravel substrate transitioning into mudflats moving seaward. Shoreline
vegetation is minimal —most of the upland area is part of the boat ramp and existing parking lot
and facilities. Substrate shows a segregation by particle size —the further inland, the smaller the
particle size. Point Whitney also supports clam and oyster beds as a part of its shoreline.
(c) All critical areas and their buffers on the project site;
Critical areas shown on the Jefferson County Public Lands Records indicate the following are present on the
project site:
Critical Area
Riparian Cover
Wetland
Geohazard Areas
Critical Aquifer Recharge
Area
Seawater Intrusion
Protection Zone
FEMA Flood Zone
Details as mapped by Jefferson Cou
Non -Forest; Off -Shore
Wetlands present; NWI mapped as Estuarine intertidal aquatic
bed unconsolidated shore regularly flooded (recon done by PWS
shows otherwise)
Shoreline slope stability modified; seismic hazard present
SUSC
Coastal SIPZ <100ppm chloride and % mile from shoreline
AE
(d) Assess potential impacts to critical areas function and values per the specific
requirements described in this article for each critical area type;
Critical areas found on the Jefferson County Public Lands Records indicate that no fewer than
six critical areas are found within the Action Area of the work. The Action Area shown in the
Biological Assessment includes an area above water surfaces that may be impacted by noise
and visual impacts but are not directly impacted with work. Each critical area below has been
reviewed and applicable critical areas have been further outlined. Please refer to the Biological
Assessment and project applications and drawings for further details on the project specifics
including impacts.
Critical Area
Riparian Cover
Wetland
Geohazard Areas
Details as mapped by Jefferson
County
Non -Forest; Off -Shore
Wetlands present; NWI mapped
as Estuarine intertidal aquatic bed
unconsolidated shore regularly
flooded (recon done by PWS
shows otherwise)
Shoreline slope stability modified;
seismic hazard present
Effects on functions and values
outline in JCC 18.22
No effects to functions and values
as no riparian cover is present
within the project footprint.
No effects to functions and values
as the proposed ramp will be in a
previously impacted area with
existing boat ramp. In accordance
with 18.22.270, the project area is
functionally isolated from
wetlands present.
No effects to functions and values
due to structure being placed at
or below fluctuating grade,
without disrupting existing ramp.
Critical Aquifer SUSC No effects to functions and values
Recharge Area due to structure being placed at
or below fluctuating grade,
without disrupting existing ramp.
Seawater Intrusion I Coastal SIPZ <100ppm chloride
Protection Zone and % mile from shoreline
FEMA Flood Zone I AE
No effects to functions and values
due to structure being placed at
or below fluctuating grade,
without disrupting existing ramp.
No effects to functions and values
due to structure being placed at
or below fluctuating grade,
without disrupting existing ramp.
No net rise.
The following are further justifications for no effects determinations to functions and values of
critical areas due to project work.
Riparian
Gr 6"l Areas
R Peren cover rP,NPTC, 2004;
■ C�osed Canopy
■ Non -Forest
Offshore
■ Other Naw+el Vegetenon
■ water
d. Public land Records kenw CaunH. WuAingtm oc0 eN U: fiche vw openoete P.0A
Riparian cover at the Point Whitney
is designated as "non -forest" and
"off -shore" based on the maps
available. Protection standards
18.22.830(I) require protecting
riparian vegetation or tree cover.
18.22.840(c) states that the
functions and values relate to the
existing amount of shade provided.
No shade is provided in this area and
thus the function and value of shade
is not changing with this project. In
addition, no changes are being made
to riparian vegetation, so there will
be no change in the riparian
functions. The proposed ramp will
be placed in the same location with
an expansion of footprint of roughly
250 square feet, but will not impact
riparian cover.
Wetland
Geohazard
0 Public Land Records xn,car. q ws� q� oco En Larerfirne Pw op -oar. P-1
n
t Publicland Records — FH L..— r.V
q
According to the National Wetlands
Inventory (NWI) Online Mapper,
wetlands exist in proximity to the
project area. A wetland evaluation
was completed by a Kaitlyn Kiehart,
PWS, on July 23, 2021. No wetlands
were identified within the
immediate project area. Man-made,
managed ponds are located to the
south of the existing boat ramp and
estuarine intertidal habitat is located
to the south and west. In accordance
with JCC 18.22.270 the project area
is functionally isolated from these
wetlands due to the high level of
development associated with the
hatchery buildings, roads, and
parking lot that surround the boat
ramp. Therefore, no impact to
functions and values for wetlands or
their buffers will result from the
redevelopment of the boat ramp.
Geohazard areas for the site appear
to include seismic hazard and
shoreline slope stability of
"modified" nature. No areas are
mapped as high or moderate
geologically hazardous areas within
the project area (JCC18.22.510(1)).
The potential for seismic hazard on
this site is moot due to the height of
the proposed structure being at or
below the beach grade. No structure
requested under this permit will be
above the grade of the land.
CriticalCritical Aquifer Recharge Areas are
Aquifer shown on the map for the Point
Recharge Whitney area. While JCC18.22.930(c)
Area "`." refers to chemical spill potential, no
chemicals will be kept on site as part
of the facility operations of this
public access. Furthermore, there is
no change in the use of the public
,x
access with the proposed
renovation. As no structures will be
placed into the ground and will not
be of substantial impact to nearby
+' waters, there will be no impact to
functions or values of the shown
po sly •' aquifer recharge area.
(e) Propose mitigation for unavoidable losses and impacts to critical areas;
As shown above, critical areas are not anticipated to be impacted. However, mitigation is
proposed for potential shorelines impacts, as well as to offset impacts as required by the US
Army Corps of Engineers and the WDFW.
In -water work will only be allowed from July 16 to October 14 for the protection of salmon,
sand lance and bull trout. All work below the MHHW will occur in the allowable work window.
A portion of the area to the west of the boat ramp has been restored to a lower grade to match
the vegetation line by removing sediment and relocating placed objects (picnic table and fire
pit). Approximately 900 sq. ft. has been restored and is designated a part of this mitigation
area.
In addition, the HCCC will be providing mitigation in -lieu fee credits for future mitigation
occurring in the greater Hood Canal area. Once compensatory mitigation has been agreed upon
by regulators, the HCCC will draft a Use Plan outlining specifics of mitigation. It is the intent of
WDFW to mitigate for impacts as necessary with each regulator. WDFW has agreed to the
mitigation that has already been completed on the west point. Currently, the US Army Corps of
Engineers is expecting to require mitigation for impacts below the HTL of 870 square feet. If the
county believes that compensatory mitigation is required that does not overlap with these
jurisdictions (i.e. above MHHW or OHWM not already covered by WDFW HPA requests), this
will be taken into account in the in -lieu fee calculations for credits required for purchase.
(f) Identify amount of and limits of clearing, grading, and impervious surface on a
stormwater calculation worksheet, if applicable; and
The clearing limits are limited to the extent required to install the new planks and the articulated concrete
mats, per plans. A stormwater worksheet has been submitted with this report in conjunction with this
application.
(g) Present photographs of the project site.
While project site photos exist in multiple reports submitted, additional photos will be provided upon
request.
18.22.950 Habitat Management Reports
(a) Detailed description of all proposed project components relative to on -site FWHCAs,
other on -site development, and limits of clearing;
The project is fully described above pertaining to JCC 18.22.905. Per JCC 18.22.610(1), the following are
designated as fish and wildlife habitat conservation areas (FWHCA) within the work area of the proposed
work at Point Whitney:
• Areas where federally listed species and state listed species have a primary association
• Recreational shellfish areas
• Kelp and eelgrass beds
• Forage fish spawning areas
Each of these areas will be potentially affected by project work.
(b) State whether or not in -water work is proposed, and if so, describe timing and
methods of construction;
The approved work window for the marine areas of Puget Sound is July 16 to October 14. This
project is contained within Tidal Reference Area 12 (South Puget Sound) with considerations for
salmon, bull trout, surf smelt and sand lance. For this proposed project, WDFW would complete
all work subject to tidal influence within the specified work windows. However, work could be
conducted from July 16 to February 15 with a negative forage fish survey conducted by an
approved biologist through WDFW. Negative survey results are valid for 14 days from the date
of the survey, or if forage fish spawning is observed.
Work is anticipated to be conducted in the dry during low tides as much as possible. As the tide
is going out, grading will occur, and as the tide comes in, the planks will be placed, starting at
the bottom of the ramp and working landward. Equipment will remain in the footprint of the
existing ramp and not onto the beach. Articulated concrete mats will be installed in a similar
manner, then secured to the planks and into the substrate.
(c) Date site visits were made and date report was completed;
Site visits have been conducted on 3/20/19, 4/23/19, 5/17/19, 6/5/19, 6/21/19, 7/219-30/19, 8/7/19,
8/13/19, 3/12/20, 1/15/21, and 07/23/21. This report was completed on July 26, 2021.
(d) Detailed description of the field investigation results, including habitat types present
on the property, habitat conditions with FWHCAs, location of native vegetation on the
property, and location of nonnative or invasive vegetation on the property. The habitat
management report should indicate if the critical areas extend off site;
A Biological Assessment has been prepared for this project and it details the habitat types on the project site
and beyond for listed species. Usage by listed species extends off site.
Recreational shellfish beds exist on the site and seasons are set by the WDFW. The site photos show the
extent of the shellfish usage. Oysters and clams can be found on the site and beyond.
In addition, an eelgrass delineation letter has been provided to provide technical expertise on the eelgrass
beds in the area.
Forage fish and habitat assessments have been identified in the Biological Assessment for this site as well.
Native vegetation is present on the site in low-lying clumps on the shoreline. None of the vegetation is
expected to be removed for project work. Non-native vegetation is unknown on the site.
(e) If the project area is identified as potential habitat for threatened or endangered
species, methods used to determine presence or absence of listed species, methods
used to determine if appropriate habitat occurs on site or in the vicinity of the site, and
results of the field investigation;
All listed species have been reviewed for site use, per the BA. Please see Section 10 of the report for details
on the presence or absence of the species and the effects determinations made for species and their
designated critical habitats.
(f) In addition to complying with the clearing, grading, excavation, and stormwater
requirements in JCC 18.30.060 and 18.30.070, and the current Stormwater
Management Manual for Western Washington, describe any potential effects of the
proposed activity on stormwater quantity, quality, and runoff patterns post -
construction. The report must clearly indicate if the proposal will affect or alter water
movement to the FWHCA and buffer if the proposal is implemented and identify
measures to avoid or minimize alteration of stormwater runoff patterns post -
construction;
There will be no alterations to stormwater conveyance once the project is complete. The ramp
is in the same location and the parking area is not being graded.
Seasonal restrictions applied to work conducted within or below the OHWM or MHHW, will
follow requirements within the HPA issued by the Washington Department of Fish and Wildlife,
and Water Quality Standards for Surface Waters of the State of Washington (Chapter 173-201A
WAC). Construction work will be completed in the approved work window for the project area.
This will help minimize disturbance to species because the work windows reference when fish
presence will be reduced- particularly juveniles. Construction impacts will be confined to the
minimum area necessary to complete the project. The contractor will use BMPs, as stated in
their Spill Prevention Control and Countermeasures Plan, to ensure that no foreign material
such as oil or fuel from construction equipment will enter any wetlands, flowing or standing
water. The spill prevention BMPs and water quality BMPs will minimize/prevent pollutants from
entering the waterbody during construction. All heavy equipment used for boat ramp
improvements will be situated on the existing boat ramp. This minimizes disturbance,
compaction and degradation of beach habitat and minimizes risk of oil leaks on beach. Upland
coir logs, or other sediment control devices that trap and/or filter overland runoff placed for
stormwater overland flow diversion and management during construction period. This will
eliminate the potential for overland runoff of sediment or contaminant -laden waters into the
beach area during construction period.
(g) Identify all potential impacts of the proposed activity on FWHCAs. The habitat
management report shall include:
(i) Mitigation Sequencing. Describe measures to avoid and minimize impacts to FWHCAs. For any
unavoidable impacts, describe and justify all project components that cannot avoid impacting
the FWHCA. For unavoidable impacts, mitigation plans must be prepared in accordance with
subsection (3)(h) of this section.
Mitigation sequencing per JCC 18.22.660(2) is designed to ensure no net loss of
functions on a site. While impacts on FWHCAs are minimal for this project due to scope
and extent of project work, the following sequencing has been conducted:
a. Avoidance — The project has been designed to construct a new boat ramp in the
same footprint, avoiding additional siting. This allows for a lower impact since the
impact already exists. Other avoidances have been a limit of footprint extension and
that no other work will be conducted on the site.
b. Minimization — The impacts have been limited to the smallest impacts necessary to
provide safe access to shorelines and marine waters for users. In addition, the
proposed ramp will be placed on the existing instead of removing the ramp to
reduce the impacts of removing the concrete below grade. The placement below
grade allows for sediment transport over the ramp and will not impede the
transport of material as needed for beach processes. Minimizing effects to listed
species and habitats will be accomplished through project timing, including
maximizing low tides and adhering to a fish window for in -water work.
c. Rectifying adverse impacts — Repair, rehabilitation, or restoration is not possible
when installing a boat ramp in order for the recreational uses to continue. This piece
of sequencing was not used.
d. Reducing impact overtime —The access site is intended to be maintained and used
for at least 20 years without replacement. Maintaining the site will allow for this to
be a recreational opportunity for years to come for the public.
e. Compensating by replacing, enhancing, or providing substitute resources or
environments — Some area was restored (roughly 900 square feet) to a lower grade
where vegetation is now able to grow. This restored area is being proposed as
mitigation for some impacts due to project activity. In addition, utilizing in -lieu fee
mitigation credits in coordination with HCCC will offset impacts deemed necessary
by regulating agencies including Jefferson County.
(ii) Types of Impacts. All potential impacts to FWHCAs and their functions and values shall be
identified and described in the habitat management report. Habitat management reports shall
consider direct impacts, indirect impacts, permanent impacts, temporary (long-term and short-
term) impacts, and cumulative impacts.
Listed species: Direct and indirect impacts to listed species and their associated critical habitats can
be found in the BA supplied.
Recreational shellfish: Impacts may include increased traffic to the site due to a safer and more user-
friendly boat ramp and increased harvest during allowable harvest times. Additional impacts could
include additional foot traffic to the site, increased boat traffic leading to eelgrass and shellfish
damage from boats and vehicles, and potential of increased toxins related to site traffic increases.
With WDFW testing the site for toxins and harvest, cumulative impacts on the site if management
remains diligent, should show no changes to the site impacts due to the project.
Kelp and eelgrass beds: An eelgrass memo has been supplied for this project. Impacts from the
proposed project have been minimized by maintaining and reducing the length of the boat ramp.
Eelgrass beds are anticipated to continue to thrive in this area. Potential impacts from power loading
of boats could be a reduction in eelgrass beds, but an impact like that would assume a change in the
boating community at the site.
Forage fish spawning areas: Impacts to forage fish are anticipated to remain similar to impacts now.
While increased vehicle traffic may impact the availability of forage fish spawning area within the
ramp footprint, the increase in the ramps size may be the biggest impact. The increase from 10 feet
to 12 feet wide has the potential to remove viable spawning areas at some times of the year. The
articulated concrete mats provide 20% open space to allow sediment to fill in gaps, so these areas
may still be a potential spawning area. Additional impacts have been reviewed and can be found in
the BA for this project.
(iii) Impact Area. The area (square footage) of potential impact shall be quantified for each
FWHCA. At a minimum, impact area shall include FWHCA that occurs within the limits of
clearing, as shown on the site plan;
The area of potential impact includes the area of the proposed ramp, totaling 2,016 SF. The Action
Area calculated by the consultant for the ramp work (included in the BA) includes area that will not
be impacted, as the piles are no longer being removed. Therefor, using the same sound attenuation
assessment for work done on the ramp, the impact area may encompass up to a 281 foot buffer
from the work, as shown below.
Given that the surrounding surface is comprised of water and flat surface, a hard surface coefficient
is used. Sound attenuation for hard site conditions is 6 dB per doubling of distance for point source.
Background levels (including anthropogenic sources such as pumps and traffic) are assumed to be
around 73 dBA including wave action. Heavy equipment consisting of an excavator (87 dB at 50 feet)
and a front end loader (81 dB at 50 feet) will generate up to 88 dBA of noise on the site.
Using the first equation from section 7.1.4.2 of the Construction Noise Impact Assessment (WSDOT
Biological Assessment Preparation Manual August 2020), we find that:
D = Do * 10((Construction Noise —Ambient Sound Level in dBA)/a)
Where D = the distance from the noise source
Do = the reference measurement distance (50 feet in this case)
a = 25 for soft ground and 20 for hard ground. For point source noise, a spherical
spreading loss model is used. These alpha (a) values assume a 7.5 dBA reduction per
doubling distance over soft ground and a 6.0 dBA reduction per doubling distance over
hard ground.
D = 50 * 1088-73 = 281 feet
(h) Provide a detailed mitigation plan for any unavoidable impacts.
A mitigation plan will be developed by the HCCC once in -lieu fee has been approved. The mitigation
work also includes the previously completed restoration of the western edge of the "point" at the west
side of the project. Parking area and fill was removed to match the existing grade of vegetation on the
site (See Plan Set Sheet 9). The area is expected to revegetate naturally with grasses and low vegetation.
This accounts for roughly 900 square feet of mitigation above OHW.