HomeMy WebLinkAboutRS_Lake_Study_Southport_Shoreline_Modifications_20170412_v2LAKE STUDY
Southport Shoreline Modifications
Prepared for: SECO Development Inc.
Prepared on behalf of: Greg Krape, SECO Development, Inc.
April 2017
THE
WATERSHED
COMPANY
Printed on 30% recycled paper.
L A K E S T U D Y
Southport Shoreline Modifications
Prepared for:
Greg Krape
SECO Development, Inc.
1083 Lake Washington Blvd. N, Suite 50
Renton, WA 98056
Prepared by:
Revised April 2017
The Watershed Company
Reference Number:
150809
The Watershed Company Contact Person:
Andy Noone
Cite this document as:
The Watershed Company. Revised April 2017. Lake Study. Southport Shoreline
Modifications, Renton, WA. Prepared for SECO Development, Renton, WA.
i
TABLE OF C ONTENTS
Page #
1 Introduction ......................................................... 1
1.1 Background and Purpose ............................................................................. 1
2 Existing Conditions and Ecological Functions 3
2.1 Description of Project Area ........................................................................... 3
2.2 Critical Areas and Habitat ............................................................................. 7
3 Local Regulations ............................................... 9
4 Project Description ........................................... 10
4.1 Proposed Shoreline Modifications ............................................................. 10
4.2 Project Purpose ........................................................................................... 11
5 Analysis of Alternatives ................................... 11
6 Impact Evaluation & Functional Lift Analysis 12
7 Best Available Science ..................................... 15
7.1 Habitat .......................................................................................................... 15
7.2 Overwater Cover .......................................................................................... 16
7.3 Lighting ........................................................................................................ 16
7.4 Water Quality (substrate disturbance and discharge of waste products) 16
8 Summary ............................................................ 17
References ............................................................. 18
Appendix A: Southport Shoreline Modifications Site Plan
L IST OF E XHIBITS
Figure 1. Vicinity map from King County iMAP (Electronic reference) ............................ 1
Figure 2. Aerial view of proposed project parcels (outlined in yellow) from City of Renton
COR Maps (Electronic reference). .......................................................... 2
ii
Figure 3. Looking northeast near the center of the bulkhead. Note the existing bulkhead,
piles, waler, and sheet piles to be removed/repaired. ............................... 3
Figure 4. Looking southwest from the pier in the northeast corner. Note the existing
bulkhead, piles, and waler to be removed/repaired. ................................. 4
Figure 5. Looking north near the western area of the bulkhead. This is the approximate
location of the western proposed float. ..................................................... 4
Figure 6. Looking east from the western pier adjacent to Boeing. The western float is
proposed in the right hand area of the photo, and the eastern float is
proposed adjacent and parallel to the distant bulkhead on the left of the
photo. ....................................................................................................... 5
Figure 7. Looking northeast from the eastern walkway. Restoration is proposed for this
area including pile removal, weed removal, and construction of a
shoreline cove (at the area to the right on the photo)................................ 5
Figure 8. Detail of timber waler, pile, timber spacer, sheet pile and anchor. Note the
rotted condition of the timber sheet pile closest to the concrete bulkhead.6
Figure 9. The dolphin and finger pier in the center of the photo is proposed for removal.
................................................................................................................. 6
Figure 10. The dolphin in the center of the photo is proposed for removal. ...................... 7
Figure 11: A turtle was observed on site by Kenny Booth, Senior Planner. The turtle
appears to be an invasive red-eared slider (photo taken August 10th,
2015) ........................................................................................................ 9
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L A K E S T U D Y
SOUTHPORT S HORELINE M ODIFICATIONS
1 INTRODUCTION
1.1 Background and Purpose
The purpose of this report is to document potential critical area impacts associated
with proposed shoreline modifications at the Southport site, located on the
shoreline of Lake Washington in the City of Renton, Washington (Figures 1 and 2).
The property is located at 1083 Lake Washington Blvd N, Renton, Washington
98055 (SW ¼ of Section 05, Township 23 North, Range 5 East; 47.503467 N
Latitude, -122.205303 W Longitude; Figures 1 & 2). The tax parcel numbers
associated with this project are: 0823059216, 0523059075, and 0523059076. The
project area falls within the Lake Washington/Cedar/Sammamish Water Resource
Management Area (WRIA 8).
Figure 1. Vicinity map from King County iMAP (Electronic reference)
Project Site
Location
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Figure 2. Aerial view of proposed project parcels (outlined in yellow) from City of Renton
COR Maps (Electronic reference).
The Southport development includes the Bristol I and II apartment buildings
(completed), a hotel (under construction), and a 3-building office and parking
garage complex (under construction). Previous Shoreline Substantial
Development Permits include the Southport Level 2 Site Plan in 2000 (Ecology
filing date May 3, 2000; SDP #2000-NW-40003); decking over the water discharge
tunnel in 2006 (LUA-06-033, SM); and modifications to the master plan in 2008
(LUA-99-1889, SA-A, SM) and again in 2014 (LUA 14-000645, SA-A, AM, MOD,
MOD). A Shoreline Conditional Use Permit for a mixed-use development (Bristol
I) was approved in 2001 (LUA01-057, CU-H). Previous shoreline permits did not
include the improvements proposed at this time.
Shoreline modifications are now proposed to repair the existing bulkhead,
improve in-water ecological conditions, remove a portion of the bulkhead to
facilitate construction of a shoreline cove, accommodate temporary moorage of
motorized and non-motorized vessels, and allow for expanded recreational use of
the shoreline.
Lake Washington is considered a critical area by the City of Renton. Renton
Municipal Code (RMC) 4-3-050-F-2(c) requires that a lake study be conducted as
part of any modification to a lake critical area. This report fulfills this
requirement.
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2 EXISTING CONDITIONS AND
ECOLOGICAL FUNCTIONS
2.1 Description of Project Area
The site is located in the City of Renton on Lake Washington, between Gene
Coulon Memorial Beach Park and the Boeing manufacturing facility. The site is
zoned Urban Center and designated as a High Intensity environment under the
Renton Shoreline Master Program.
The existing shoreline is entirely bulkheaded. Upland conditions within the
subject parcels adjacent to the waterfront are almost exclusively impervious
(90%+), either concrete or pavers. The central shoreline area ten feet upland of
the bulkhead includes a pedestrian easement (Recording Nos. 2005102100894,
20051021000895, and 20051021000896) and an emergency vehicle access
easement. The easternmost 53 feet of the central waterfront is vegetated with a
mix of non-native landscape plants and non-native invasive species such as
Himalayan blackberry.
Existing depths along the bulkhead in the central and western shoreline areas
range from 8 feet to 17 feet.
Figure 3. Looking northeast near the center of the bulkhead. Note the existing bulkhead,
piles, waler, and sheet piles to be removed/repaired.
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Figure 4. Looking southwest from the pier in the northeast corner. Note the existing
bulkhead, piles, and waler to be removed/repaired.
Figure 5. Looking north near the western area of the bulkhead. This is the approximate
location of the western proposed float.
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Figure 6. Looking east from the western pier adjacent to Boeing. The western float is
proposed in the right hand area of the photo, and the eastern float is proposed
adjacent and parallel to the distant bulkhead on the left of the photo.
Figure 7. Looking northeast from the eastern walkway. Restoration is proposed for this
area including pile removal, weed removal, and construction of a shoreline
cove (at the area to the right on the photo).
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Figure 8. Detail of timber waler, pile, timber spacer, sheet pile and anchor. Note the
rotted condition of the timber sheet pile closest to the concrete bulkhead.
Figure 9. The dolphin and finger pier in the center of the photo is proposed for removal.
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Figure 10. The dolphin in the center of the photo is proposed for removal.
2.2 Critical Areas and Habitat
Lake Washington
Lake Washington is a 33.8 square mile freshwater lake. It is the second largest
lake in the State of Washington. Adult and juvenile Chinook salmon and
steelhead trout (listed as Threatened under the Federal Endangered Species Act)
migrate through Lake Washington. Adults migrate upstream to reach spawning
grounds in local tributaries; juveniles migrate downstream from their natal
streams to reach the ocean. Coho salmon also migrate through Lake Washington
(Species of Concern under the Federal Endangered Species Act). Bull trout, listed
as Threatened under the Federal Endangered Species Act, may also migrate
through Lake Washington. Lake Washington is a Shoreline of Statewide
Significance and is classified as a Type-S waterbody.
Wetlands and Streams
No wetlands or streams were noted within the immediate vicinity of the project
area, nor do publicly available data indicate the presence of aquatic areas aside
from Lake Washington.
Habitat
Habitat structure on the property is virtually non-existent, with no native
vegetation present along the shoreline in the project area. The majority of the area
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immediately upland of the bulkhead is covered with impervious surfaces. Several
invasive species are present on site including Himalayan blackberry and reed
canary grass. The lack of structural diversity limits food and cover opportunities
for most wildlife species, including songbirds and small mammals. The lack of
shoreline vegetation also limits cover opportunities for fish and allocthonous
inputs into the lake.
Soils
According to the Natural Resources Conservation Service, the property contains
Urban land (Ur) soils.
Wildlife
Washington Department of Fish and Wildlife Priority Habitats and Species
database lists two bald eagle nests within one mile of the project site.
Additionally, osprey presence is documented less than a half mile from the project
site. These large birds of prey typically nest and feed over large bodies of open
water and will likely fly over the project site. Great blue herons are widespread in
western Washington. Outside of breeding, which occurs in tall trees, commonly
away from human disturbance, the birds are most often observed in and along
rivers, lakes, and wetlands. The waters of Lake Washington are likely used by
foraging and resting herons throughout the year.
A turtle was observed on site by Kenny Booth, Senior Planner on August 10th,
2015. The turtle appeared to be a red-eared slider, a non-native species. There are
only two native turtle species in Washington, the western painted turtle and the
western pond turtle. Historically, western pond turtles inhabited Lake
Washington, but they have been extirpated from the area for a number of years,
likely due to development pressures, diminished water quality, and/or
competition from introduced turtle species. The western painted turtle may still
occur in Lake Washington but is also being displaced by introduced invasive
species such as the red-eared slider. Two other introduced species have also been
observed in Lake Washington: snapping turtles and spiny soft shell turtles.
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Figure 11: A turtle was observed on site by Kenny Booth, Senior Planner. The turtle
appears to be an invasive red-eared slider (photo taken August 10th, 2015)
Since the project site is mostly hardscape surfaces, vegetative habitat is limited,
and it is unlikely that terrestrial wildlife use the site. Small birds may fly over the
site in order to reach the adjacent to 57-acre Gene Coulon Memorial Beach Park,
which, while heavily landscaped, provides significantly more habitat value than
the project site.
3 LOCAL REGULATIONS
In Renton, shoreline areas are governed by the Shoreline Master Program and
regulated specifically by RMC 4-3-090. Lake Washington is a Shoreline of
Statewide Significance.
As mentioned, RMC 4-3-050-F-2(c) requires that a lake study be conducted as
part of any modification to a lake critical area. The required lake study must
demonstrate that the proposed modifications result in no net loss, meaning the
applicant must demonstrate that the modifications, combined with any
mitigation efforts, will result in equivalent or better protection of shoreline
functions.
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Mitigation or restoration of the critical area may involve restoring the shoreline
by removing structures or impervious surfaces, removing invasive plant species,
and/or planting native vegetation along the shoreline.
4 PROJECT DESCRIPTION
4.1 Proposed Shoreline Modifications
SECO Development proposes the following improvements to the shoreline area
at the Southport site (see attached plan set for additional details):
Eastern shoreline
Approximately 53 linear feet of bulkhead is proposed for removal at the
easternmost extent of the project area. A shoreline cove is proposed to replace
the existing bulkhead in this location. Restoration in this area will also involve
cutting and covering of derelict piles and control of invasive weeds as well as
installation of woody debris and native emergent and upland plantings. A fully-
grated ramp and float is also proposed in the eastern shoreline area. The eastern
float will feature two ells for added recreational boat access. The float and ramp
will total 2,027 square feet. Proposed work along the eastern shoreline also
includes abandoning the recently removed 164-foot-long floating walkway
referred to as a “log boom”. The log boom was removed several years ago and
will not be restored as part of this project.
Central shoreline
Significant repairs are proposed for the bulkhead and timber pilings along the
central shoreline. The proposed repairs involve the following: all derelict
creosote piles and horizontal walers supporting the bulkhead will be removed
(approximately 40). The inner timber sheet pile will be cut below the low water
line. Sheetpile will be driven along the waterward edge of the timber sheet pile
and bolted to the remaining portion of the timber sheet pile. The area behind the
steel plate will be filled with concrete. Other proposed modifications within the
central shoreline include removal of the following: approximately 114 derelict
pilings (including those supporting the bulkhead), 290 feet of 12-inch by 14-inch
horizontal dimensional beams, several drifted logs resting against bulkhead, and
all anchor and link logs from the log boom western attachment piling.
Western shoreline
The western shoreline modifications include installation of a pump out facility at
the existing wharf, and installation of a second, fully-grated ramp and float
totaling 564 square feet of overwater coverage. As mitigation, the proposed
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modifications include removal of 2 dolphins (each comprised of 7 piles), 1 finger
pier (5-feet-wide by 17-feet-long), removal of a 10-foot-wide by 14-foot-long ell
end dock, and abandonment of a second recently removed finger pier that was
also 5-feet-wide by 17-feet-long.
4.2 Project Purpose
The purpose of the proposed project is to repair the deteriorating bulkhead. The
bulkhead has been assessed by an engineer and it has been determined that in
order for the bulkhead to last another 30-50 years, it must be repaired. The
bulkhead supports the existing walkway/promenade, which is adjacent to the
existing apartments and hotel under construction. In addition to needing
structural repairs, the existing bulkhead system is unsafe. As mentioned,
multiple rounded piles and sheet piles are located waterward of the concrete
portion of the bulkhead. Many of these components are located just below the
OHWM and can’t be seen at all times from shore. This project seeks to enhance
safety by removing in-water components and installing other repairs to ensure
the structural integrity of the bulkhead. The proposed floats are intended to
provide public access opportunities for primarily non-motorized watercraft. As
mentioned, the site includes four mixed-use apartment buildings, with a hotel
and multiple office buildings now under construction. Thus, demand for access
to the water will increase greatly. The floats will allow for residents of the site
and hotel guests to utilize kayaks, canoes, or other non-motorized vessels. This
will result in an increase in direct public access to the shoreline.
5 ANALYSIS OF ALTERNATIVES
Pursuant to RMC 4-9-050-L(1)(b), attempts to avoid and minimize, and rectify
impacts to the on-site shoreline critical area have been taken.
Avoidance: Shoreline improvements are necessary to avoid future bulkhead
failure and provide adequate water access. An alternative location for the project
is not feasible, as the project is intended to ensure structural stability for the
shoreline and to provide shoreline access for residents, guests, and tenants at the
SECO site.
Minimization: Minimization techniques were utilized during the design process
in order to limit impacts to the shoreline critical area. Minimization measures
included providing shoreline access via anchored floats, rather than docks on
pilings; reducing the size of the two floats to the minimum necessary; and fully
grating the floats to allow light to pass through. Instead of removing and
reinstalling the entire bulkhead, repairs to the existing bulkhead are proposed to
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reduce impacts. A prior plan included installation of a grated apron and
preservation of some in-water components. The proposed plan will result in a
39% reduction (1,636 square feet) of overwater coverage compared to the
installation of the grated apron.
Rectifying/Mitigation: Approximately 53 linear feet of bulkhead will be
removed and replaced with a shoreline cove to improve shoreline functions. As
part of this restoration, 51 derelict piles will be removed and covered with gravel
fill to expand the area of shallow water habitat. Invasive weeds will be removed
and native emergent and upland vegetation will be installed in the cove area.
Mitigation also includes the removal of approximately 114 derelict creosote piles,
two additional dolphins each comprised of seven piles, one finger pier (5-feet-
wide by 17-feet-long), and one ell dock (10-feet-wide by 14-feet-long). In
addition to removing these docks and creosote pilings, the project will also
involve abandoning a second 10-foot-wide by 17-foot-long finger pier,
abandoning the recently removed 164-foot long floating walkway, removing all
anchor and link logs associated with that floating walkway, and removing
several drift logs resting against the bulkhead. Overall removal includes 310
square feet of existing pier area, and approximately 179 creosote pilings.
6 IMPACT EVALUATION & FUNCTIONAL
LIFT ANALYSIS
The project involves construction of a shoreline cove, improvements to the
shoreline bulkhead, installation of two new floats, and removal of multiple in-
water and over-water components.
Overall the proposed impact has been minimized to the greatest extent feasible in
that anchored, fully-grated floats were chosen over piers. The grating allows light
to penetrate. Anchoring the floats, as opposed to installing new pilings virtually
eliminates temporary noise impacts during installation, and it reduces in-water
structure.
To mitigate for the proposed impacts, a number of improvements are proposed.
Approximately 53 linear feet of bulkhead will be removed and replaced with a
shoreline cove. The cove will include installation of woody debris and native
emergent and upland vegetation. The cove restoration will also include cut and
cover of 51 derelict piles and invasive weed control. In total, approximately 179
creosote pilings are proposed for removal. Creosote leaches into Lake Washington
and contributes to impaired water quality. Their removal will reduce the ongoing
impact to water quality in the area. The proposed project will reduce potential
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predator structure through the removal of approximately 179 piles. The
proposed project will remove 310 square feet of existing solid-decked overwater
structures. The proposed 2,591 square feet of new ramps and floats will be fully
grated, and flotation materials will be minimized to maximize light transmittal.
Additionally, portions of the proposed floats outside of the nearshore area will
be anchored rather than supported through new piles.
The most effective strategy for minimizing or eliminating potential construction-
related impacts would be to restrict construction to periods when the presence of
bull trout, steelhead, and Chinook salmon is improbable. The combined fish-
protection prohibitions on in-water construction by NOAA Fisheries and USFWS
result in an allowable in-water construction window of July 16 through July 31
and November 16 through December 31. This window is adequate to minimize
the probability that bull trout, Chinook salmon, or steelhead would be in the
action area during construction. The precautionary conditions that have been
proposed would minimize the potential for the release of waste products or
construction debris to the lake. Additionally, during construction, any barge or
workboat used for construction would not be allowed to ground, and all
construction debris will be stockpiled on upland areas or on the construction
barge so that it can be properly disposed of on land in such a manner that it
cannot enter into the waterway or cause water quality degradation.
Through the removal of 179 piles, the project will significantly minimize in-water
structures that may attract predators to juvenile salmonids. The effects of new
overwater structures will be minimized through the use of grated decking and
through the use of helical anchors instead of new piles. The proposed
improvements, when considered with the proposed mitigation will result in no
net loss of ecological function, as demonstrated below in Table 2.
Table 1. Impact Assessment
Structure Proposed for
Removal
Proposed
New
Pilings (including dolphins) (number of pilings) 179 4*
Fully-grated Float (western) (square feet) 0 564
Fully-grated Float (eastern) (square feet) 0 2,027
Solid deck overwater structure (square feet) 310 0
Bulkhead (linear feet) 53 0
*Two new steel piles will required for each float access pier.
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Table 2. Functional Lift Analysis / No Net Loss Demonstration
Critical Area/
Shoreline
Setback
Functions
Existing Conditions Proposed
Conditions
Functional
Improvement?
Water
Quality
The shoreline area is essentially
entirely impervious and
incapable of filtering stormwater
prior to entering the lake.
Creosote pilings are leaching
into the lake.
All derelict
creosote pilings
are removed.
Yes; water quality will be
slightly improved. While
the majority of leaching
occurs early in the life of
the piling, some leaching
of heavy metals and
contaminants will be
avoided.
Hydrology
The shoreline area is essentially
entirely impervious and therefore
lacks vegetative structure that
can slow stormwater velocities
discharging into the lake from
nearby impervious areas.
Similar to
existing
conditions.
Hydrologic function on
site will be maintained.
Habitat
The existing shoreline area is
essentially entirely impervious
and lacks the native vegetation
necessary to provide substantial
forage/cover opportunities. In-
water habitat contains
approximately 179 pilings
providing bass habitat. The
entire shoreline is bulkheaded
and invasive weeds occur in
areas.
Approximately
53 linear feet of
bulkhead will be
removed and
replaced with a
shoreline cove.
Invasive species
will be removed.
All of the derelict
pilings will be
removed.
Habitat function will be
maintained. The
shoreline cove will
provide some nearshore
habitat as well as native
emergent and upland
vegetation. Piles that
provide potential juvenile
salmon predator habitat
will be removed.
Net
Condition
The shoreline area is heavily
degraded with impervious
surfaces at the shoreline edge
and no native vegetation.
Derelict creosote pilings provide
bass habitat and encourage
juvenile salmon predation.
Invasive species
are removed.
53 linear feet of
bulkhead are
removed and
replaced with a
shoreline cove.
179 derelict
creosote pilings
are removed.
Proposed fully
grated floats
allow for light
penetration.
Derelict piles will be
removed, reducing
juvenile salmon
predation. Shallow water
rearing habitat will be
expanded through the
creation of a shoreline
cove and placement of
gravel substrate and
native vegetation.
Invasive species will be
removed. Hydrologic and
shoreline habitat function
will be maintained.
Water quality functions
will be slightly improved.
Overall, no net loss of
shoreline functions will
occur.
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7 BEST AVAILABLE SCIENCE
In order to minimize and avoid potential impacts and provide adequate
mitigation, the proposed project and mitigation plan were designed using best
available science in accordance with RMC 4-8-120-19, and RMC 4-3-050-L-1-c. A
discussion of the potential affects to salmonids associated with the project
follows below.
7.1 Habitat
Graphs of trapping data indicate that juvenile Chinook salmon migrating from
the tributaries into Lake Washington exhibit two basic strategies: 1) direct
migration to the lake as fry without extended stream rearing; and 2) migration to
the lake as parr or smolts (average length 100 mm), following extended stream
rearing. Chinook fry begin entering Lake Washington around the first of the
year, peaking in February, while parr and smolts enter the lake from April
through July, peaking in late May (Tabor et al. 2006). Most naturally produced
Chinook salmon juveniles in Lake Washington originate in the Cedar River
(Celedonia et al. 2008). Past studies of juvenile Chinook salmon in Lake
Washington indicate that juvenile Chinook salmon were concentrated in the
south end of Lake Washington from February to May and the density of Chinook
salmon fry using lake shorelines in the spring decreases logarithmically with
increasing distance from the mouth of the Cedar River (Tabor et al. 2006).
The geographic proximity of the project site to the mouth of the Cedar River
suggests that the area may be significant to Chinook and other salmonids.
However, past studies in Lake Washington have found that juvenile Chinook
salmon prefer shallow water habitats with overhanging vegetation, with an
approximately 4.5:1 ratio of fish using overhanging vegetation to fish occurring
away from overhanging vegetation (Tabor et al. 2004, 2006). Shallow water
habits and significant overhanging vegetation do not currently exist in the
project area.
During the period from mid-February to mid-April, Chinook salmon fry rear
along shorelines less than 1.6 feet in depth, and they are typically found within
30 feet from the OHWM (Tabor et al. 2006). As noted above, at high water,
depths adjacent to the bulkhead range from 8 to 17 feet; therefore, the project is
not expected to affect shallow water rearing habitats in the areas where bulkhead
repair is proposed. In the eastern shoreline, removal of a portion of the bulkhead
and installation of a shoreline cove will increase shallow water habitat and
overhanging vegetation; therefore improving conditions for juvenile Chinook
rearing in this area.
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7.2 Overwater Cover
Juvenile Chinook salmon display avoidance behavior of piers. Surface water
observations found that upon approaching a pier, juvenile Chinook salmon will
move into deeper water and either pass under or swim around the pier (Tabor et
al. 2006). Similarly, in acoustic tracking studies, Chinook smolts avoided areas
under overwater structures and changed course to move around such structures
(Celedonia et al. 2008). The change in light levels associated with piers and other
overwater structures may make it difficult for juvenile Chinook salmon to detect
predators (Tabor et al. 2006), and salmon predators like smallmouth bass are
often associated with pier piles (Celedonia et al. 2008). The proposed project will
reduce potential predator structure through the removal of approximately 179
piles. The proposed project will remove 310 square feet of existing solid-decked
overwater structures. The 2,591 square feet of new ramps and floats will be fully
grated, and flotation materials minimized to maximize light transmittal.
Additionally, the proposed floats will be anchored rather than supported
through new piles. Two small piers are proposed to support access to each float.
Two steel piles are proposed for each pier.
Through the removal of approximately 179 piles, the project will significantly
minimize in-water structures that may attract predators to juvenile salmonids.
The effects of new overwater structures will be minimized through the use of
grated decking and through the use of helical anchors instead of new piles.
7.3 Lighting
Juvenile salmonids on Lake Washington are attracted to bright artificial lighting
(Tabor et al. 2015), which can potentially make them more vulnerable to
predation. No lighting is currently proposed as part of the shoreline
improvements.
7.4 Water Quality (substrate disturbance and discharge of
waste products)
Pile, finger pier, and bulkhead removal and shoreline cove construction could
produce temporary, localized sediment plumes that would dissipate following
cessation of activity. Turbidity is generally considered an undesirable condition
for salmonids, as exposure to potentially contaminated or abrasive sediments
suspended in the water column is thought to result in lethal and sub-lethal
effects (Newcombe and MacDonald 1991). However, localized episodic turbidity
events from an individual construction activity would not represent a permanent
sediment source and would not produce conditions of chronic exposure
necessary to produce a direct detrimental effect on juvenile fishes (Newcombe
and MacDonald 1991).
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Considering that the turbidity produced by any construction activity would be
localized and temporary, the most probable impact on juvenile salmonids would
be a behavior modification (avoidance response), rather than injury or reduction
in growth potential. An avoidance response could expose juvenile salmonids to
increased predation or force them away from preferred rearing areas.
The most effective strategy for minimizing or eliminating potential construction-
related impacts would be to restrict construction to periods when the presence of
Chinook and coho salmon, steelhead, and bull trout is improbable. The
combined fish-protection prohibitions on in-water construction are adequate to
minimize the probability that Chinook salmon, steelhead, or bull trout would be
in the action area during construction.
8 SUMMARY
The proposed project involves shoreline modifications to improve public
shoreline access through creation of a shoreline cove, installation of boat
moorage floats and repair to an existing deteriorated bulkhead.
A total of 2,591 square feet of new, fully-grated overwater structure is proposed.
This number includes two new floats, one totaling 2,027 square feet and the other
totaling 564 square feet. To offset impacts associated with the proposed
shoreline modifications, multiple mitigation measures are proposed.
Approximately 53 linear feet of bulkhead will be removed and replaced with a
soft-shore cove that includes woody debris, native emergent and upland
vegetation and placement of gravel substrate. Mitigation also includes removal
of approximately 165 derelict creosote piles, removal of 290 feet of horizontal
dimensional beams, removal of two dolphins (totaling 14 piles), removal of one
finger pier (85 square feet), removal of one ell end dock (140 square feet),
abandonment of a second finger pier (85 square feet), and abandonment of the
164-foot-long log boom.
The construction of the shoreline cove and removal of the derelict piles and piers
will result in an improvement in water quality, while habitat and hydrological
functions will be maintained. Overall, no net loss of shoreline ecological
functions will result from the proposed project.
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REFERENCES
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The Watershed Company
April 2017
Appendix A
A P P E N D I X A
Southport Shoreline Modifications
Site Plan
REVISED
REVISED
REVISED
REVISED
REVISED