HomeMy WebLinkAboutSpecial 2009-12-14 Item 3E - Shoreline Master Program (SMP) - Cumulative Impacts AnalysisCITY OF TUKWILA
SHORELINE MASTER PROGRAM UPDATE
Cumulative Impacts Analysis
Prepared for:
City of Tukwila
Revised December 2009
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Introduction
With the assistance of a grant from the Department of Ecology, the City of Tukwila is updating its Shoreline
Master Program (SMP) consistent with state guidelines (WAC Chapter 173 -26). Under the shoreline guidelines,
local jurisdictions are required to evaluate and consider cumulative impacts of reasonably foreseeable future
development in the shorelines of the state (WAC 173- 26- 186(8)(d)). This report assesses the cumulative impacts
of development and activities in the shoreline over time under the proposed amendments to the City of Tukwila
SMP and was prepared as a grant deliverable (SMA Grant No. G0600234, Task 9).
At this point in time, the proposed SMP has been reviewed by Department of Ecology (a staff draft and the
Planning Commission Recommended Draft SMP), the Planning Commission, and the Tukwila City Council, and
Tukwila staff has made revisions to the draft as a result of the comments received and discussions carried out with
the review entities. Accordingly, this analysis should be considered the final version, evaluating the proposed
SMP dated December 2009. This version of the SMP is expected to be locally adopted before the end of the year
and forwarded to Ecology for formal review and approval in early 2010.
For the City of Tukwila, shorelines of the state in the city limits and Potential Annexation Areas (PAAs) include
approximately 13.6 river miles of the Green/Duwamish River, between approximately river mile (RM) 17.3 and
RM 3.7. The Green/Duwamish River in Tukwila is designated as a "shoreline of statewide significance," having
a mean annual flow greater than 1,000 cubic feet per second (cfs).
The purpose of evaluating cumulative impacts is to insure that, when implemented over time, the proposed SMP
goals, policies and regulations will achieve "no net loss" of shoreline ecological functions from current "baseline"
conditions. Baseline conditions are identified and described in the Final Shoreline Inventory and Characterization
Report (May 2007); Appendix A to the proposed SMP. The proposed SMP provides standards and procedures to
evaluate individual uses or developments for their potential to impact shoreline resources on a case -by -case basis
through the permitting process. The purpose of this memorandum is to determine if impacts to shoreline
ecological functions are likely to result from the aggregate of activities and developments in the shoreline that
take place over time.
The state guidelines establish that, "to ensure no net loss of ecological functions and protection of other shoreline
functions and/or uses, master programs shall contain policies, programs, and regulations that address adverse
cumulative impacts and fairly allocate the burden of addressing cumulative impacts among development
opportunities. Evaluation of such cumulative impacts should consider:
Current circumstances affecting the shorelines and relevant natural processes;
Reasonably foreseeable future development and use of the shoreline; and
Beneficial effects of any established regulatory programs under other local, state, and federal laws.
This cumulative impacts assessment uses these three considerations as a framework for evaluating the potential
long -term impacts on shoreline ecological functions and processes that may result from development or activities
under the proposed SMP over time.
1 WAC 173- 26- 286(8)(d)
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Current Circumstances
As part of the City's SMP update, an Inventory and Characterization Report and Map Folio was prepared in
December 2006, and was finalized in the spring of 2007 following technical review by Ecology and King County.
The final report and map folio is included as Appendix A to the proposed SMP. The inventory and
characterization report identifies existing conditions and evaluates the ecological functions and processes in the
City's shoreline jurisdiction. The inventory included a characterization of ecosystem processes functioning at a
watershed scale, as well as an inventory and assessment of conditions in all shoreline areas within the City of
Tukwila and its Potential Annexation Areas (PAAs) (shown below as the "shoreline planning area The term
"shoreline planning area" refers to the approximate area within the City's shoreline jurisdiction, or areas subject
to SMP regulations, as shown in Figure 1. The following sections summarize baseline conditions, or current
circumstances, with regard to Tukwila's shorelines.
Watershed Context and Shoreline Modifications
The City of Tukwila is situated in the Puget Sound Lowlands at the transition from the fresh water Green River to
the tidally influenced Duwamish estuary ecosystem. Tukwila includes approximately 12.5 miles of the
Green/Duwamish River. The Green River basin is part of the Green/Duwamish Water Resource Inventory Area
(WRIA 9).
Historically, the Green/Duwamish River drained a significantly larger area than it does today. River course
changes and major engineering projects in the early part of the 20 century resulted in both the White and Cedar
Rivers being diverted to neighboring basins. As a result, the overall freshwater discharge in the Green/Duwamish
River has been reduced to approximately one -third of the pre- diversion era. The Green/Duwamish has undergone
extensive modifications as part of past river management with the intent of reducing channel migration and
limiting the extent and duration of valley flooding.
Levees and/or revetments have been constructed along the majority of the Green/Duwamish River through the
City of Tukwila to increase bank strength and reduce flooding. In addition, flows within the Green/Duwamish
River have been significantly modified by the construction of the Howard A. Hanson Dam and installation of
water diversions. These modifications have significantly reduced the severity of floods that historically covered
much of the valley bottom. The condition of the current system of levees and revetments is a growing source of
concern for King County and the cities involved, as many of the levees are aging and would not meet current
standards for either flood conveyance or stability.
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Map 2
Shoreline
Planning
Area
Legend
Tukwila City Limits
River Miles
Shoreline Planning Area
Potentential Annexation
Areas
t_ Reach Areas
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Figure 1. City of Tukwila Green Duwamish Shoreline Planning Area
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Biological Resources and Shoreline Functions
The Green/Duwamish River within the City of Tukwila provides important habitat for several species of
salmonids and other listed fish, as well as a few wildlife species, such as osprey. The entire length of the
GreenlDuwamish River within the City of Tukwila has been declared "critical habitat" for the Chinook salmon
and bull trout and both species are listed as threatened under the Federal Endangered Species Act. The aquatic
environment within the channel is an important corridor, particularly in the transition zone from the freshwater
riverine environment to tidal estuarine environment of Elliot Bay. Almost every species of anadromous fish
migrates through this transition zone, making it important for providing habitat functions.
The transition area generally extends from the East Marginal Way South Bridge to the city's northern limits. The
transition zone has effectively been pushed upstream from its historic location due to: (1) a significant reduction
(70 of fresh water flowing into the Duwamish estuary (owing to the diversion of the White and Cedar/Black
Rivers), (2) channel dredging, and (3) reduction of flows as a result of the Howard A. Hanson dam. The
establishment of heavy industrial uses in the transition zone has replaced wetlands and natural riparian areas with
impervious surfaces, and the river banks have been replaced by armoring, eliminating edge habitat which slows
flows and creating unrestrained rapid downstream flows. Spatial structure, residence time, and the habitat
available for fish refugia and rearing functions in the Duwamish estuary have therefore been reduced and
constrained. High densities of fish have been observed utilizing what is left of this specific habitat. At the
watershed scale, overall increases in salmonid survival rates are dependent on the availability of sufficient
transition zone habitat to accommodate fish while they adjust from fresh to salt water (WRIA 9 Steering
Committee, 2005).
Modifications to the river system have resulted in reduced levels of ecosystem functioning in the other reaches of
the river flowing through Tukwila, including hydrology, water quality, riparian habitat, and in- stream habitat.
Changes to hydrology focus on modified flow regime due to dam construction, diversion, and urban development.
River management and levees have reduced the connection between the rivers and their floodplains, changing the
spatial extent of habitats, and increasing the potential for negative water quality impacts. Disturbances to the
channel banks have resulted in areas that are dominated by non native invasive species. Wood, in the form of
riparian trees and in- channel wood, is generally lacking throughout the system, which negatively impacts riparian
and aquatic habitats.
Land Use and Public Access
The majority of the upper Green/Duwamish watershed, beyond the city limits, is in managed forestland, parkland,
or designated wilderness areas. Agricultural land covers much of the upper watershed within the Green River
gorge. The Kent -Auburn Valley is a transitional area between the forest and agricultural activities upstream to the
highly developed residential, industrial and commercial development in the cities of Kent, Tukwila, and Seattle
downstream in the Lower Green Duwamish River Valley.
Within the valley, industrial, commercial, and residential land uses dominate the former Green River floodplain in
the vicinity of Tukwila. South of the city, commercial and warehouse /industrial land uses dominate on the right
bank in the City of Kent, with agricultural fields on the left bank within the Tukwila South potential annexation
area. Commercial development is prevalent between the southern city boundary and I -405. Residential
development dominates between 1 -405 and the I -5 Bridge. North of the I -5 Bridge to the Turning Basin,
residential uses give way to commercial uses. The Turning Basin, located at river mile 5.8, is the approximate
southern boundary of the predominantly industrial area that extends to the northern city limit.
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There are significant public access opportunities for enjoyment and use of the Green/Duwamish River in Tukwila.
A series of parks and open space areas provide recreational opportunities and the Green River Trail provides
access along the river throughout much of the city, linking many shoreline parks. In addition, there are several
unofficial recreational fishing sites and fishing shelters at various locations along the shoreline.
Restoration Opportunities
The inventory and characterization provides an assessment of shoreline functions and identifies potential
conservation and restoration opportunities. As part of the SMP update process, the City also developed a Draft
Shoreline Restoration Plan in February 2007. The plan report was revised in May following technical review by
King County and Ecology. It was modified in 2009 to update the status of restoration projects and include some
newly identified projects and is included as Appendix B to the proposed SMP.
The Restoration Plan builds on the Inventory and Characterization Report and provides a framework to:
Identify primary goals for ecological restoration of the Green/Duwamish ecosystem;
Identify how restoration of ecological function can be accomplished;
Suggest how the SMP update process may accomplish the restoration of impaired shoreline functions
associated with the Green/Duwamish ecosystem; and
Prioritize restoration projects so that the highest value restoration actions may be accomplished first.
Past work which focused on the Green\Duwamish River (in Water Resource Inventory Area (WRIA) 9) has
resulted in an important collection of data used to identify potential restoration opportunities. Significant
restoration activities along the Green\Duwamish River are already underway in the form of the multi agency
Green River Ecosystem Restoration Project. Several restoration opportunities have been identified as part of the
WRIA 9 Final Salmon Habitat Plan and the recently adopted King County Flood Hazard Management Plan.
Based on the key ecosystem functions that are currently altered, there appear to be two specific types of
restoration actions that will most benefit the Green/Duwamish ecosystem in Tukwila. While these projects are
intended to restore many ecosystem functions, the restoration activities will occur in the highly -urban valley
bottom, and as a result, cannot fully achieve pre disturbance channel conditions. In addition, some restoration
actions must occur at the watershed scale, which will restore ecosystem functions that cannot be addressed solely
within Tukwila.
Enlarging channel cross sectional area. This action will increase flood storage, allow for more stable
Levees, restore floodplain area, provide a larger intertidal zone in the important transitional area, and
provide a more natural transition from aquatic to upland habitats. This action could include the use of
setback levees and revetments, and the excavation of historic fill or floodplain materials to create back
channels.
Enhance existing habitats. This action will improve the functioning of the existing aquatic, riverine
wetland, and riparian habitats that currently exist along the Green/Duwamish River. These actions could
include the removal of non native invasive vegetation, installation of native riparian vegetation, and
installation of LWD below ordinary high water.
The Restoration Plan identifies over 20 site specific projects that are in various stages of development. The
projects generally address one or both of the types of actions described above. High priority projects will
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typically address both hydrologic and habitat ecosystem functions; have opportunity for multiple funding sources;
include freshwater tributary channels; and /or not require additional property acquisition. In the context of
designating shoreline environments and developing management policies and regulations, the City wants to
encourage and enable restoration projects throughout the city wherever possible, with a particular focus on
projects in the transition zone.
Potential Use Conflicts
Two key issues illustrate potential use conflicts and constraints to implementing restoration in Tukwila: 1) levee
maintenance and management; and 2) existing development patterns and anticipated redevelopment.
Discussion of shoreline planning for the Green/Duwamish River in Tukwila must acknowledge the fact that, in
light of the existing system of levees and revetments, the City cannot act alone. There are a variety of regulatory
jurisdictions outside of the City with different responsibilities for maintenance and management of the levee
system, including the U.S. Army Corps of Engineers (the Corps), the Federal Emergency Management Agency
(FEMA), King County River and Floodplain Management Unit (acting as part of the Green River Flood Control
Zone District), and private property owners. The City of Tukwila Public Works Department has overall
responsibility for maintenance of all levees including the federally certified levee, which extends from about the I-
405 crossing to S. 180 The actual maintenance work on the levees is contracted by the City to King County.
The restoration of native tree and shrub species along the levees would increase riparian habitat and ecological
functioning of this reach of the Green/Duwamish River, benefiting salmonids as well as other species. However,
along the federally certified levee the Corps of Engineers (responsible for certifying the federal levee) has been
requiring removal of large trees to prevent what the Corps considers destabilization of the levee caused by the root
systems, potential water piping (e.g., water infiltrating into and through levees along root pathways at higher rates
than it could through root free soil) at high flows, and levee failure if trees fall. For the Vegetation Free Zone of
the levee, current Corps guidance only allows grass as vegetative cover on the levees (USACOE, Engineering
Manual 1110 -2 -301). Current guidance also specifies a root -free zone where plantings can occur, but roots will
generally not penetrate this structural zone. Therefore, under current regulations, to meet the requirements for
federal levee certification, some existing vegetation will continually have to be removed to maintain the levee
certification. Under the SMA, removing trees and vegetation from the riparian zone of shorelines of the state is in
conflict with policies for vegetation conservation and enhancement. A possible solution is to set back and re-
slope the levees to create benches where vegetation can be planted that will not interfere with the levee prism as
the levee system is reconstructed to improve its stability. This would require additional easement area beyond the
existing maintenance easements that have been acquired along the length of the system.
The existing development pattern also represents constraints to implementing restoration projects, including levee
setbacks, off channel habitat restoration, wetland and stream restoration, and riparian zone enhancements. Most
of Tukwila is fully developed with a dense, urbanized land use pattern along the river bank. The City's current
SMP, in place since 1974, establishes a 40 -foot setback from the mean high water line. In areas where King
County's SMP still applies, a 20 to 50 foot setback is established, depending on the type of use. In many places,
there is little more than this 20 to 40 -foot zone that is not intensely developed. Some places have more open
space and less development and thus have greater flexibility to accommodate potential habitat restoration actions.
The City's vision for future land use includes maintenance of existing urban development and further
development of its urban character, particularly its identity as a regionally significant center for manufacturing,
industrial, and commercial development, as well as treating the river as more of an amenity than in the past. One
challenge for the City is in determining how best to accommodate new development and redevelopment near the
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shoreline in a manner consistent with the many competing goals of the GMA and SMA and their accompanying
local documents, the Comprehensive Plan and the Shoreline Master Program.
Reasonable Foreseeable Future Development and Use
For the purposes of the cumulative impacts analysis, this section focuses on the effects of anticipated development
and use of the shoreline as envisioned in the City's Comprehensive Plan and the proposed SMP. Since the
existing development pattern in Tukwila is well established and highly urbanized, the focus of this discussion is
on potential redevelopment throughout much of the city. That is, there are few vacant parcels along Tukwila's
shorelines and virtually no potential for large areas of undeveloped land along the shoreline to be subdivided and
newly developed. One exception is the Tukwila South Potential Annexation Area, which is currently agricultural
and/or undeveloped land. While this section addresses anticipated future development and redevelopment, the
subsequent sections address how such development would occur under the proposed SMP.
Comprehensive Plan
The Comprehensive Plan Land Use Element is divided into several elements, including three that specifically
address different geographic areas of the City: the Manufacturing/Industrial Center, Tukwila Urban Center, and
Tukwila South. Additional planning efforts for these areas include master plans, planned actions, and/or strategic
implementation plans.
From the upstream City boundary downstream to the Black River Green River confluence within the city limits
(S. 204 Street to the north boundary of Ft. Dent Park), the Comprehensive Plan designates areas along the
shoreline as Tukwila Urban Center and Commercial /Light Industrial (predominantly south of I -405). North of I-
405 in this reach, designations include a mix of Low Density Residential, Medium Density Residential, Regional
Commercial Mixed Use, Commercial/Light Industrial, and Heavy Industrial. Significant portions of Low Density
Residential areas within the reach's shoreline area are designated with a Public Recreation Overlay and are
developed as Fort Dent Park, the Foster Golf Links and the Tukwila Community Center. Within the City's
southern PAA, along the western Green River shoreline, all areas are designated as Tukwila Valley South. The
Comprehensive Plan element generally envisions an extension of the commercial and industrial development on
the valley floor for this area.
From the Black River Green River confluence downstream to the northern city limits near the 16 Avenue S.
bridge, the Comprehensive Plan designates areas along the shoreline as a mix of Manufacturing Industrial
Center/Heavy and Low Density Residential. Other designations include Manufacturing Industrial Center/Light,
Commercial/Light Industrial, and Residential Commercial Center.
Tukwila Manufacturing /lndustrial Center
The Tukwila Manufacturing/IndustriaI Center (MIC) is one of eight regionally significant industrial and
employment centers in the Central Puget Sound region. Designated as such by the Puget Sound Regional
Council, the City has developed a specific element in its Comprehensive Plan and an Implementation Plan to
guide redevelopment in the area. The Implementation Plan is structured as a Planned Action under SEPA and
was adopted in 1998. This element was developed consistent with the Comprehensive Plan and has been
integrated as a component of the City -wide SMP Update. The element includes innovative approaches to
combine shoreline redevelopment with environmental conservation, restoration, or enhancement actions. The
plan also provides guidelines for integrating habitat enhancement with alternative bank stabilization designs,
based in part on King County flood reduction policies and guidelines for bank stabilization. The MIC Plan will
be reviewed for any needed amendments after the current SMP update is completed.
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Redevelopment in the MIC is also subject to design guidelines developed in 1992 by the Boeing Corporation, in
coordination with the City, and described in Duwamish Corridor Redevelopment Proposal /Design Guidelines
(Sugio Kobayashi Ullman Inc., 1992). The document, which became part of the MIC Planned Action, establishes
goals, objectives, and guidelines for redevelopment of Boeing properties in the Duwamish corridor. Objectives
include enhancement of the shoreline environment by replacing old riprap bulkheads with new, more
environmentally friendly retention structures and native riparian vegetation. The plan also promotes increased
public access as redevelopment occurs, primarily as public and employee -only (semi public) access features and
public shoreline access trails. Finally, the plan addresses remediation actions so that as redevelopment occurs,
sites with contaminated soil and groundwater are identified and clean up plans are developed, consistent with state
and federal laws. As this document is 14 years old, the City will be working with the Boeing Company to identify
any needed amendments or revisions to the Redevelopment Proposal after approval by Ecology of the SMP
update.
Tukwila Urban Center Plan
The Comprehensive Plan includes an element addressing the Tukwila Urban Center. The City is currently
preparing a Tukwila Urban Center Plan. The Urban Center serves as a regionally significant shopping center
(including Westfield Southcenter Mall) with light industrial, office park, and transportation oriented development.
The center is generally bounded by I -405, I -5, South 180 Street, and the Green River. Policies and
implementation strategies for the Urban Center promote mixed -use commercial and residential development near
the Green River, with an integrated network of park, trail, and recreational facilities.
Tukwila South
The Comprehensive Plan includes an element addressing Tukwila South, an area bounded generally by South
180 Street, I -5, the Green River, and South 204 Street. This area is approximately 75 percent of the southern
designated potential annexation area in unincorporated King County, which will be annexed by the City effective
December 31, 2009. Currently the area is primarily a mix of agricultural and vacant lands, with a small amount of
residential and industrial uses. The Comprehensive Plan element, prior to the adoption of the Tukwila South
Master Plan, generally envisioned an extension of the commercial development on the valley floor for this area.
As elsewhere in the City, the Comprehensive Plan promotes mixed -use densities for residential development near
the river, and maintenance and enhancement of the open space network along the Green River. The Tukwila
South Master Plan, required by the Comprehensive Plan prior to any significant development and annexation of
the Tukwila South Area, was adopted by the City Council in June 2009.
In July 2005, a Final EIS was issued for the 498 -acre Tukwila South Project. The adopted Tukwila South
Development Agreement allows up to 10.3 million square feet of development. The development is envisioned to
create a major new employment hub with campus -style office and research complexes with an array of
commercial, retail, residential, hotel, and recreational uses included. The master plan, described in the Final EIS
as being in accordance with the vision and policies of the Tukwila South component of the City's Comprehensive
Plan, expects to develop over two phases: Infrastructure Development Stage (3 years) and Full Buildout Stage
(horizon of 2030). The Infrastructure Development Stage would include the extension of major roadways (such
as Southcenter Parkway) into the area, establishment of site grades throughout the area, installation of utilities and
stormwater control facilities, and construction of sensitive areas mitigation as required for the master plan.
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The Draft Sensitive Area Master Plan (SAMP) and the Fisheries and Wetland Mitigation Plans, included as an
appendix to the Final EIS and required because the site was designated a Sensitive Areas Master Plan Overlay
District, describe mitigation and restoration of sensitive areas within the Tukwila South Area. These components
of the Tukwila South project will be located partially within shoreline jurisdiction and are proposed primarily as
mitigation for wetland and stream fill impacts elsewhere on the project site. The plans propose to create 7 -acres
of off channel habitat along the Green River, which is direct mitigation for filling of 7,127 feet of streams and
ditches in the Tukwila South project area (Ecology "401" Water Quality Certification Permit, 11/7/2005). The
habitat area would be designed to provide summer rearing, winter refuge, and upstream migrant holding habitats
for fish. Eight- hundred lineal feet of the existing levee would be relocated in a curved fashion landward, between
South 196 Street and South 200 Street. Approximately 4.5 acres on the river -side of the relocated levee would
be excavated down to the bed elevation of the Green River to create open water habitat. The remaining 2.6 acres
would be upland area with slopes ranging from 3:1 to 8:1 and would be planted with a mixture of palustrine
emergent species and shrub scrub species. Woody debris snags would be anchored at the upper and lower ends of
the restoration area to protect the downstream bank from erosion and to prevent sand bar formation from creating
an isolated pool.
The plans also propose to restore a perennial fish- bearing stream currently maintained as an agricultural ditch
(Johnson Creek). The creek currently discharges to the Green River through a fish blocking floodgate. Around
1,350 feet of Johnson Creek would be relocated to a newly constructed meandering channel and associated
floodplain parallel to and north of S 204 Street. A riparian area along the stream would be planted with a mixture
of palustrine emergent species, shrub scrub species, and trees. Large woody debris would be anchored to the
banks to provide in- stream structure and water velocity modification. A fish- passable flood gate would be
installed at the confluence of the Green River to allow fish to migrate through the culvert in the levee and into the
tributary under most flow conditions.
In June 2009, the City of Tukwila and the Tukwila South Project property owner (La Pianta LLC) entered into a
development agreement (Ordinance No. 2233). The development agreement stipulates that the property owner
grant permanent easements to the City for maintenance access and improvements to the City's levee system on
the west side of the Green River between South 196 Street and South 204 Street, as well as for public bicycle
and pedestrian trail access.
One of the main purposes of these easements is to make room for future levee improvements. The federally
certified 205 levee (from South 180 Street to South 196 Street) is not expected to be altered. As part of the
Tukwila South development, La Pianta is proposing to replace the King County- constructed levee system (from
South 196 Street to South 204 Street), with a levee designed to meet criteria for federal certification. The
existing east -west trending Cross Valley Levee would also be shifted southward from its existing location to the
south end of the project area just north of and roughly parallel to South 204 Street.
In the context of "reasonably foreseeable future development," the proposed changes at Tukwila South may
improve riverine ecological functions by providing off channel habitat restoration along the Green River.
However, it is important to note that the foreseeable changes in the Tukwila South project area will not result
directly from provisions or regulations within the proposed SMP. The proposed changes will result primarily
from the following:
Mitigation required by Department of Ecology through the "401" Water Quality Certification and the US
Army Corps of Engineers through the "404" Permit (to fill wetlands),
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Identification of the Tukwila South area as a Sensitive Area Master Plan Overlay District with area -wide
implementation of the sensitive areas ordinance,
SEPA environmental review processes, and
The development agreement between the City and the property owner.
Summary of Conditions and Findings
In summary, the City's shoreline planning areas are primarily designated for industrial/manufacturing and
commercial/retail land uses. Other areas are primarily designated for low- density single- family uses. Public
access and recreational uses along the shoreline are located throughout the city. These uses are not expected to
change over time. Most of the City's shorelines are fully developed and future development activities on these
properties would largely occur as redevelopment.
The inventory and characterization and restoration planning elements of the SMP update should inform goals,
policies, regulations, and environment designations. In this context, the key findings can be summarized as
follows:
The Green/Duwamish River throughout Tukwila is a critical resource, providing migratory habitat for
numerous fish species, as well as riparian habitat for a variety of wildlife. The Green/Duwamish River
changes from fresh to salt water within Tukwila, making it a unique and important section of the overall
river system that deserves attention.
Existing shoreline habitat is largely homogenous and degraded throughout the city. The variation that
does exist is typically not significant enough to warrant different levels of protection or restoration focus
along the shoreline with the exception of the transition zone.
The flood protection system is made up of a mix of newer levees (e.g., the 205 levee), and older portions
of levee (e.g., the northern portion of the city). The older levees may not meet current engineering
standards in terms of slope angles and geotechnical stability, which may provide opportunities for
different approaches to redevelopment.
Restoration opportunities exist throughout Tukwila's shoreline environment. Activities that provide
restoration of both floodplain functions and habitat functions should be prioritized. Policies should
promote and regulations should enable the City to accomplish restoration goals and actions.
Given the relative homogeneity of the resource condition and needs throughout the city, environment
designations should reflect the distinction in current and planned land use and opportunities to expand or
enhance restoration. Primarily this is a distinction between existing residential development, where banks
may be armored with bulkheads or revetments, and commercial and industrial development elsewhere in
the city, where banks are altered by flood control structures.
It is important to acknowledge that future shoreline use patterns should not be driven solely by the
Comprehensive Plan and zoning. As a result of the SMP update process, changes may be warranted in the
Comprehensive Plan, zoning code, and floodplain management regulations to help facilitate long range planning
objectives for shoreline management (such as implementation of levee setbacks). That is, since the proposed
SMP amendments are informed by a body of technical and scientific shoreline analyses consistent with state
guidelines, future amendments to other regulations may be necessary to successfully implement the SMP's vision.
The following sections summarize the most significant proposed changes to the Tukwila's SMP and how these
changes reflect the findings of the inventory and characterization and restoration planning efforts.
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Summary of Proposed SMP Amendments
Existing Regulatory Framework
The City's current SMP designates all shorelines as "Urban." At the time the 1974 SMP was developed, all of the
land in Tukwila's shoreline jurisdiction was either zoned industrial or was developed with urban uses. The SMP
defines the Urban Environment as "areas to be managed in high intensive land uses, including residential,
commercial, and industrial development and accessory uses, while providing for restoration and preservation to
ensure long -term protection of natural and cultural resources within the shoreline" (Tukwila, 1974). The SMP
further states that the management objectives for the shoreline "are directed at minimizing adverse impacts on the
river and shoreline ecology, maximizing the aesthetic quality and recreational opportunities of the river shore, and
recognizing the rights and privileges of property owners" (Tukwila, 1974). Within the Urban Environment,
Tukwila's SMP employs a three tiered system of regulations based on the distance from the Green River mean
high water mark (MHWM). These tiered management zones are generally described below and illustrated on
Figure 2:
River Environment/Zone: a 40 -foot wide zone extending landward from MHWM and having the most
environmentally protective regulations;
Low Impact Environment/Zone: the area between the River Environment and 100 feet from the MHWM;
and
High Impact Environment/Zone: the area between 100 and 200 feet from the MHWM.
200'
LOW
IMPACT
ZONE
Proposed Environment Designations
RIVER
ZONE
11
200'
URBAN ENVIRONMENT
100'
4 a'
RIVER
ZONE
c
LOW
IMPACT
ZONE
MEAN HIGH WATER LINE
Figure 2. Tukwila SMP Shoreline Management Zones (1974 SMP; TMC 18.44)
HIGH
IMPACT
ZONE
The City also administers the King County Shoreline Master Program for the areas which have been annexed
since the adoption of the City's SMP. These areas are designated Urban and the setbacks from Ordinary High
Water Mark vary from 20 feet to 50 feet depending on whether the use is water dependent, single family or
commerciaUindustrial.
Tukwila's proposed shoreline designation system reflects the state's guidelines. The City's three proposed
environment designations are:
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Shoreline Residential Environment;
Urban Conservancy Environment; and
High Intensity Environment.
The City proposes to designate river buffers to replace the current system of parallel shoreline management zones.
Instead of the current River Environment, a minimum river buffer would be established for each shoreline
environment. Allowed uses are proposed for the buffer area along the river and outside of the buffer in the
remaining shoreline jurisdiction. This system is intended to facilitate the City's long -range objectives for land
and shoreline management, including:
1. Ensuring no net loss of ecological shoreline functions;
2. Providing for habitat protection, enhancement, and restoration to improve degraded shoreline ecological
functions over time and protection of already restored areas;
3. Allowing continued and increased urban development outside of the buffers in recognition of Tukwila's
role as a regionally significant industrial and commercial center; and
4. Providing for improved flood control in coordination with King County and the Army Corps of
Engineers.
The proposed shoreline environment designations and their associated buffers are illustrated in Figures 3 through
5 and described briefly below. Designation criteria, management policies, use regulations, and development
standards for each designation and management zone are in the proposed SMP.
Shoreline Residential Environment
This environment would be designated in the area between the ordinary high water mark and 200 feet landward
for all properties zoned for single family use (see Map 3 of the proposed SMP).
The purpose of the Shoreline Residential Environment is to accommodate urban density residential development,
appurtenant structures, public access and recreational activities. In addition to general shoreline management
objectives (above), the protective river buffer would limit development to accomplish the following objectives
(not listed in order of priority):
Ensure "no net loss" to shoreline ecological functions;
Help protect water quality and habitat function by limiting allowed uses;
Protect existing and new development from high river flows by ensuring sufficient setback of structures;
Promote restoration of the natural character of the shoreline environment; and
Allow room for reconstructing over steepened river banks to achieve a more stable slope and more
natural shoreline bank conditions and avoid the need for shoreline armoring.
The width of the buffer will be determined by identifying the location where the river bank would achieve an
angle of 2.5:1 (the natural angle of repose to promote more stable banks) and then setting back 20 feet from that
location. However, in no case shall the buffer be less than fifty (50) feet from the OHWM, measured on the
horizontal. The river bank in the Shoreline Residential Environment is typically in a somewhat modified and
degraded state but generally not stabilized with revetments or levees. This buffer width will protect shoreline
functions, and allow for restoration by re- sloping and stabilization using bioengineering methods where possible
and through planting with native vegetation. The buffer area and vegetation requirements established for the
Shoreline Residential Environment will allow removing invasive plants; planting native vegetation; include other
12
features to improve shoreline habitat; and will prevent the placement of any structures in an area that could
potentially prove instable. The proposed buffers are wider than those currently required under the existing SMP.
A cross section illustrating the proposed Residential Shoreline Environment and buffer is provided in Figure 3.
Urban Conservancy Environment
200'
Shoreline Residential
Environment
Ordinary High Water Mark
z
Figure 3. Schematic of Proposed Shoreline Residential Environment
The proposed Shoreline Residential environment would be applied to approximately 14 percent of the city's
shoreline. Counting both banks, this represents approximately 3.5 miles of shoreline. This designation would
apply to areas currently within the city limits, affecting approximately 200 residential parcels. Approximately 67
residential parcels have existing structures within 50 -feet of the OHWM. The proposed SMP provisions ensure
that the "no net loss" standard will be met because: 1) much of the residential development already exists and is
located within 50 to 100 feet of the OHWM; and 2) the banks are in a somewhat degraded and altered state
(oversteepened; armored in places; and lack native vegetation). The provisions for bank restoration and
vegetation enhancement or restoration will be triggered in the Shoreline Residential environment if development
or redevelopment includes proposals for bank stabilization or overwater structures. Whether the actual buffer
distance on individual parcels becomes the minimum 50 -feet, or something greater after bank reconfiguration, the
proposed SMP provisions will ensure that vegetation and bank stability will be improved immediately adjacent to
the river. These changes in the shoreline would occur incrementally over time and would not only meet the "no
net loss" standard, but should improve ecological functions over time.
This environment begins at the Ordinary High Water Mark and extends landward 200 feet along portions of the
river not navigable to large water craft and that are not located in low- density residential areas (see Map 3 of the
proposed SMP).
The Urban Conservancy Environment areas are currently developed with high intensity urban multifamily,
commercial, industrial and/or transportation uses or are designated for such uses in the proposed annexation areas.
The Urban Conservancy Environment will also be established along Fort Dent Park as this site is bordered by a
County constructed levee. However, uses will be restricted immediately adjacent to the river by establishment of
a minimum protective buffer intended to protect and restore ecological functions where they exist in urban and
developed settings while allowing a variety of compatible uses.
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52
In addition to general shoreline management objectives, the river buffer would be established to accomplish the
following objectives (not listed in order of priority):
Protect existing and restore degraded ecological functions of the open space, flood plain and other
sensitive lands in the developed urban settings;
Ensure no net loss of shoreline function when new development or redevelopment is proposed;
Provide opportunities for restoration and public access;
Allow for adequate flood and channel management to ensure protection of property, while
accommodating shoreline habitat enhancement and promoting restoration of the natural character of the
shoreline environment, wherever possible;
Avoid the need for new shoreline armoring; and
Protect existing and new development from high river flows.
The width of the buffer in the Urban Conservancy Environment is proposed as 125 feet, if the shoreline has an
existing levee located south of I -405; or 100 feet, if there is no levee.
The establishment of the 125 foot buffer along the shorelines with levees south of I -405 allows sufficient room for
eventually setting back the levees to a 2.5:1 slope, and including a mid -slope bench that can be planted with
native vegetation. This approach widens the channel somewhat to accommodate high flows and improves
shoreline function by providing vegetation for habitat enhancement. As the Corps of Engineers does not permit
planting on the levee prism, the only way to improve habitat along the 205 leveed portion of the river is to create a
bench that can be vegetated that will not create a hazard for the stability of the levee. This levee configuration is
the minimum levee profile under the proposed SMP and is the approach currently used by King County and the
Corps of Engineers for levee repair /replacement projects.
As an alternative to the 100 foot buffer, a buffer reduction of up to 50percent may be authorized if the property
owner chooses to lay back the bank to achieve a more stable slope of 2.5:1 plus a 20 -foot wide area at the top of
the bank and plant it with native vegetation in accordance with the buffer vegetation standards in the proposed
SMP.
A cross section illustrating the proposed Urban Conservancy Environment and buffer for leveed areas is provided
in Figure 4.
14
200'
Urban Conservancy Environment
AJIow rotiO
.:fur Levee
repair
replacement;
1_
Ordinary High Water Mark
15
125'
Buffer I
Figure 4. Schematic of Proposed Urban Conservancy Environment for Areas with Levees
The proposed Urban Conservancy environment would be applied to the majority of the city's shoreline
(approximately 73 percent). Counting both banks, this represents approximately 18.2 miles of shoreline. This
designation would apply to areas currently within city limits and in the Tukwila South PAA, affecting
approximately 277 parcels. The designation would apply to areas currently developed with commercial and light
industrial uses, as well as less intense uses such as the Foster Golf Links course, Fort Dent Park, and the Tukwila
Community Center property. The proposed SMP provisions ensure that the "no net loss" standard will be met
because the buffer area (100 to 125 -feet from OHWM) will allow for bank reconfiguration and/or setback levees
with vegetated benches. The provisions for bank restoration and vegetation enhancement or restoration will be
triggered as development or redevelopment occurs in the Urban Conservancy environment. Whether the actual
buffer distance on individual parcels becomes 100 or 125 feet, or something different after bank reconfiguration at
a slope of 2.5:1, the proposed SMP provisions will ensure that vegetation and bank stability will be improved
immediately adjacent to the river. Even with a buffer reduction in exchange for re- sloping/laying back the bank
and planting with native vegetation, resulting buffer widths would be wider than those required under the current
SMP. These changes in the shoreline would occur incrementally over time and would not only meet the "no net
loss" standard, but should improve ecological functions over the long term.
High Intensity Environment
This environment will be designated in the area between the Ordinary High Water Mark and 200 feet landward
for the area of the shoreline located from the southern end of the Turning Basin north to the City limit (including
the City's North PAA) (see Map 3 of the proposed SMP). The High Intensity Shoreline Environment area is
currently developed with industrial uses, a few of which are water dependent uses. Some areas of the shoreline in
this environment are hardened with riprap or bulkheads, while other areas are more natural banks, such as those in
the three restoration sites around the Turning Basin.
The purpose of the Urban High Intensity Environment is to provide for high intensity, commercial, transportation
and industrial uses while encouraging water dependent uses, protecting existing shoreline ecological functions
and restoring ecological functions in areas that have been previously degraded. In addition to general shoreline
management objectives (above), the river buffer would be established to accomplish the following objectives (not
listed in order of priority):
Protect existing and restore degraded ecological functions of the open space, flood plain and other
sensitive lands in the developed urban settings;
53
function when new development or redevelopment occurs;
Ensure no net loss of shoreline public access; while
ortunities for restoration and p rotection of property,
Provide opp management to ensure p
adequate flood and channel manag and promoting restoration of the natural character oft the
Allow for adeq p
accommodating shoreline habitat enhancement
shoreline environment, wherever possible;
Avoid the need for new shoreline armoring; and h river flows• his consistent with
ment from g This buffer width support salmonld
Protect existing and new develop high water mark.
Areas Ordinance for Type 2 streams that th is
e City's Sensitive Ar river bank to improve shoreline function over
The buffer will extend 100 feet landward from the ordinary the T re-vegetating t
the buffer width ows established
for setting back and re -veg
fish use, back the bank to
existing conditions. if the property owner chooses to lay
percent may be authorized planted area lay n the
to 50 p vegetation plus an additional p -feet wide
A buffer reduction of up e and plant it with native veg
no steeper than a 3:1 slop
top of the new bank.
rovided in Figure 5.
t h e p High Intensity Environment and buffer is p
A cross section illustrating t p
,I
1 1
200' I
1 High i ntensity Environment I
I k 10C' Yw.,. `I
Alto roam a 1:��i,, a�;.�. {.�,xra;-
reconfigure 'h',. .1 Bu{ l
-i ,y, R Shea
l s
bank to
river
3 :1 slope
Ordinary High Water Mark
Figure 5. Schematic of Proposed High Intensity Environment
F ►g 13 percent of eline•
lied to approxima p t of would apply el areas
High Intensity environment would be applied ercen the city's shoreline.
miles of shoreline. This design designation
The proposed Hig approximately 3.1 m arcon would
design
Counting both banks,
this represents app ern PAA, affecting approximately 34 parcels.
arcels. These properties are
within the in limits and in the g Northern ro osed SMB Basin. The provisions ensure that the
currently the Manufacturing and Industrial Center, north of the Turning for bank
would apply e a in th will allow triggered
ed primarily with industrial and commercial (1�0 feet from OHWNI) or restoration will be trigg
currently develop P vegetation enhancement o
ions for bank restoration and veg environment. nt. enhancement
the actual on buffer distance on
"no net loss" standard will be met because the buffer si slope of 3:1, the
reconfiguration. The pro h Intensity reconfiguration at a p
r 00f occurs in the different after bank improved immediately adjacent to
individual development is or redevelop k stability will be imp
rosed MP p r becomes will feet, that something ve getation visions will ensure that veg and ban
proposed SMP pro percent buffer reduction, resulting buffer widths will be wider than those currently
the river. Even with a 50 p
54
16
required under the existing SMP. These changes in the shoreline would occur incrementally over time and would
not only meet the "no net loss" standard, but should improve ecological functions over the long term.
Changes to Development Standards and Use Regulations
The preference for water dependent or water related uses established in the Shoreline Management Act requires a
body of water that is navigable and accessible both to businesses and the general public. The challenge for
Tukwila's SMP is that very little of the Green/Duwamish River is navigable for commercial vessels. Of the 13.6
river miles in the City and its PAA, only approximately 1.5 river miles are accessible to deep draft vessels, from
the Duwamish River Turning Basin north to the city limits. The vast majority of the river can only be accessed by
kayaks, or small motorized boats and definitely not larger ships or barges. In addition, the presence of recently
re- certified U.S. Army Corps of Engineers (COE) levees along a major portion of the river prevents direct access
to the river, other than via visual access and pedestrian/bicycle trails, thus further limiting the possibility for
establishment of water- dependent uses. Other portions of the shoreline are protected by King County constructed
levees or over steepened banks armored with revetments, which also limit the possibility of water dependent uses.
Nonetheless, water dependent uses are designated as priority uses north of the Turning Basin.
The proposed SMP offers several changes to the development regulations that encourage shoreline conservation,
facilitate shoreline restoration, and prohibit activities that would cause adverse impact to shoreline functions and
processes. The most significant change is related to provisions within the proposed river buffer. The restoration
plan identifies vegetation enhancement or restoration as one key priority for shoreline management in Tukwila
and the development standards proposed in the SMP establishes vegetation protection and enhancement
requirements in the High Intensity and Urban Conservancy Environments. The City will work with shoreline
property owners to encourage re- vegetation of the shoreline buffer in the Shoreline Residential Environment
(bank stabilization projects and projects for overwater structures must include revegetation of buffers as a
condition of approval). The restoration plan also prioritizes actions that expand the active channel of the river
and/or provide off channel habitat. The application of the new river buffer widths would facilitate projects such
as levee setbacks and vegetated benches, as well as removal of shoreline armoring and setting back and re- sloping
banks in non -levee areas to achieve a more natural, vegetated shoreline. These actions would occur either as
project specific implementation of the WRIA 9 Salmon Habitat Plan (restoration plan) or the King County Flood
Hazard Management Plan; or as part of redevelopment proposals in coordination with the City, King County, and
other stakeholders.
Consistent with state guideline requirements, the proposed SMP integrates environmentally sensitive areas
regulations (Sensitive Areas Ordinance (SAO), TMC 18.45). Under the proposed SMP, standards and regulations
for designated sensitive areas that are physically located in the shoreline jurisdiction would apply to all shoreline
uses and development. The SAO standards provide many provisions to protect the shoreline, tributaries to the
Green/Duwamish River, associated wetlands, and adjacent upland areas.
Another change is the requirement of environmental impact mitigation where unavoidable impacts to shoreline
ecological functions would occur as a result of allowed uses or development under the proposed SMP. Consistent
with state guidelines (WAC 173- 26- 201(2)(c)), the proposed SMP requires mitigation measures where impacts
are unavoidable to achieve the "no net loss" of ecological functions standard. This requirement is applied to any
activity that would result in impacts to ecological functions, regardless if the action required a shoreline permit or
not.
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Other changes include limiting new shoreline modifications such as bulkheads and riprap revetments along much
of the City's shoreline. New development would be required to be located and designed to avoid the need for
shoreline stabilization measures. The proposed shoreline stabilization standards will limit any new shoreline
stabilization, unless it can be shown through extensive studies to be necessary and will require the use of
bioengineering techniques wherever feasible. Further, the conservation of native shoreline vegetation and
removal of invasive vegetation has been emphasized in the new shoreline regulations for the City to further
stabilize shorelands and increase habitat functions. Other changes related to development of specific uses in the
shoreline are also designed to protect shoreline ecological functions and processes, while continuing to allow
legal uses and development and encouraging public access to the shoreline for water oriented uses such as fishing.
Under the proposed SMP, new standards have been developed for non conforming uses and structures. The
existing SMP allows the expansion of a building containing a nonconforming use by 25 percent, provided the
Planning Commission grants a special permit in cases of evident hardship. Under the proposed SMP,
nonconforming uses cannot be enlarged or intensified to occupy additional land or expanded structure. A non-
conforming use can be replaced by another non conforming use provided the new use meets certain criteria
including avoidance of adverse impacts on shoreline ecological processes and/or functions; restoration of the
entire shoreline buffer including paved areas no longer in use; and expansion of the use is limited to the minimum
necessary to achieve the intended function.
The existing SMP allows a non conforming structure that has been destroyed by not more than 75 percent to be
re- built. Under the proposed SMP, such structures, regardless of the extent of destruction, may be rebuilt to their
original dimensions. The proposed SMP also allows such structures to be altered or partially reconstructed
provided that: 1) new construction does not further intrude into the buffer; 2) reconstruction will not create
adverse impacts to shoreline ecological functions and/or processes; 3) the bank is re- sloped to a 2.5:1 or 3:1 angle
in non leveed portions of the river and the entire shoreline buffer is restored (included paved areas no longer in
use); or for properties along leveed portions of the river, the remaining buffer area is enhanced, invasive
vegetation removed, and native vegetation planted on the levee prism, as allowed by the Corps of Engineers.
Single family structures in residential zoning districts which have legally non conforming setbacks from the
OHWM may expand the ground floor provided that: 1) expansion occurs along the existing building line(s); 2) the
existing distance from the nearest point of the structure to the OHWM is not reduced; 3) the square footage of the
new intrusion into the buffer does not exceed 50 percent of the square footage of the current intrusion; and 4)
invasive plant species are replaced with native species within the entire shoreline buffer. Non conforming uses
and structures that cease or are vacated for 24 consecutive months must be brought into conformance This time
limitation may be extended by the City provided the shoreline buffer is restored or enhanced.
The proposed changes to development standards and use regulations are, in general, more protective than the
existing SMP. New development would be required to meet standards for environmentally sensitive areas within
shoreline jurisdiction as well as the policy intent and development standards of the proposed SMP.
Redevelopment would be allowed in all environments. As redevelopment occurs, the policies and regulations in
the proposed SMP require that development be located and designed in a manner that avoids impacts to ecological
functions and/or enhances functions where they have been degraded. For example, the vegetation conservation
measures require that, as part of a redevelopment proposal, non native or invasive species be replaced with native
vegetation appropriate for riverine riparian environments. Another example pertains to shoreline stabilization (for
residential bulkheads or revetments). Policies and development standards establish a preference for alternative
"soft- shore" erosion control or stabilization designs. Where shoreline stabilization is requested, project applicants
would be required to demonstrate why a bioengineered design would not provide adequate protection of existing
18
development. Existing non conforming uses and structures are allowed to continue under the proposed SMP.
However, when changes or expansions occur, shoreline ecological functions would be improved because of the
requirements to restore or enhance the shoreline buffer with native vegetation and/or to re -slope non leveed river
banks. Over time, as the proposed changes to the SMP are implemented, they will likely have a net beneficial
effect on shoreline ecological processes as properties are redeveloped.
Restoration Planning
As described previously, the SMP Restoration Plan (Appendix B to the proposed SMP) represents the shoreline
restoration element of the SMP. The plan includes goals and policies addressing restoration. The policies
establish the City's intent is to meet the "no net loss" standard, and result in an overall improvement to the
condition of the habitat and resources within the shoreline jurisdiction of the City over time. The plan identifies
opportunities for restoration activities or efforts that include programmatic opportunities (e.g. surface water
management; water quality improvement; public education), 28 site specific opportunities (some of which are
already underway), regional plans and policies for Puget Sound restoration, and potential funding and partnership
opportunities. The SMP's restoration planning is focused on areas where shoreline functions have been degraded
by past development activities. The areas with impaired functions were identified in the City's Shoreline
Inventory and Characterization. Recognizing that much impairment to shoreline processes and functions are the
result of watershed scale activities beyond the City's control, the implementation of the Restoration Plan will
improve shoreline ecological functions in the City over time.
Beneficial Effects of Any Established Regulatory Programs under Other Local,
State, and Federal Laws
A variety of other regulatory programs, plans, and policies work in concert with the City's SMP to manage
shoreline resources and regulate development near the shoreline. The City's Comprehensive Plan establishes the
general land use pattern and vision of growth and development the City has adopted for areas both inside and
outside the shoreline jurisdiction. Various sections of the Tukwila Municipal Code (TMC) are relevant to
shoreline management, such as zoning (TMC Title 18), stormwater management (TMC 14.30), and floodplain
management (TMC 16.52). The City's development standards and use regulations for environmentally sensitive
areas (TMC 18.45) are particularly relevant to the City's SMP. Designated sensitive areas located in the shoreline
may include areas of potential geologic instability, wetlands, watercourses, and fish and wildlife conservation
areas. As noted above, standards and regulations in the critical areas regulations are now integrated in the
proposed SMP.
A number of state and federal agencies may have jurisdiction over land or natural elements in the City's shoreline
jurisdiction. Local development proposals most commonly trigger requirements for state or federal permits when
they impact wetlands or streams; potentially affect fish and wildlife listed under the federal Endangered Species
Act (ESA); result in over one acre of clearing and grading; or affect the floodplain or floodway. As with local
requirements, state and federal regulations may apply throughout the city, but regulated resources are common
within the City's shoreline jurisdiction. The state and federal regulations affecting shoreline related resources
include, but are not limited to:
Endanzered Species Act: The federal ESA addresses the protection and recovery of federally listed species. The
ESA is jointly administered by the National Oceanic and Atmospheric Administration (NOAA) Fisheries
(formerly referred to as the National Marine Fisheries Service), and the United States Fish and Wildlife Service
(USFWS).
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57
58
Clean Water Act (CWA): The federal CWA requires states to set standards for the protection of water quality for
various parameters, and it regulates excavation and dredging in waters of the U.S., including wetlands. Certain
activities affecting wetlands in the City's shoreline jurisdiction or work in the adjacent rivers may require a permit
from the U.S. Army Corps of Engineers and/or Washington State Department of Ecology under Section 404 and
Section 401 of the CWA, respectively.
Hydraulic Proiect Avvroval (HPA): The Washington Department of Fish and Wildlife (WDFW) regulates
activities that use, divert, obstruct, or change the natural flow of the beds or banks of waters of the state and may
affect fish habitat. Projects in the shoreline jurisdiction requiring construction below the ordinary high water
mark of Puget Sound or streams in the city could require an HPA from WDFW. Projects creating new
impervious surface that could substantially increase stormwater runoff to waters of the state may also require
approval.
National Pollutant Discharge Elimination System (NPDES): Ecology regulates activities that result in wastewater
discharges to surface water from industrial facilities or municipal wastewater treatment plants. NPDES permits
are also required for stormwater discharges from industrial facilities, construction sites of one or more acres, and
municipal stormwater systems that serve populations of 100,000 or more. The City is in the process of revising
its stormwater regulations to meet the new municipal NPDES permit requirements. There will be more stringent
stormwater management requirements for control of stormwater volume and quality that should result in
improvements in water quality and greater emphasis on the use of low impact development techniques throughout
the City, which will also improve conditions in the Green/Duwamish River.
State -owned Aauatic Lands: The Washington State Department of Natural Resources is the steward for the State
owned bed of the Green/Duwamish River and would regulate any structures constructed in the bed of the river,
such as piers.
Current and Future Performance of Shoreline Ecological Functions
The attached tables summarize the existing performance of shoreline ecological functions along the Green River
as described in the Shoreline Inventory and Characterization Report (ESA Adolfson, 2007). Actions that would
potentially cause a loss of shoreline function, and regulations from the proposed SMP that would protect or
improve ecological functions are identified. The net impact expected from implementing the regulatory provisions
of the proposed SMP is described along with opportunities for restoration of ecological functions. The tables
below are focused on the effectiveness of the regulatory provisions in meeting the "no net loss" standard. Site
specific restoration opportunities are outlined in the Restoration Plan (ESA Adolfson, 2007, updated in 2009) and
are not directly evaluated as part of this assessment. The tables are organized by shoreline reach (as identified in
the inventory and characterization report; see Figure 1 above), moving from the south to the north:
G -1 PAA (Tukwila South Potential Annexation Area)
G -1 (from upstream city limits to the Black River /Green River confluence)
G -2 (from the Black River /Green River confluence to the downstream city limits)
G -2 PAA (Tukwila North Potential Annexation Area)
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Conclusion
In large measure, the development and use patterns along Tukwila's shorelines are well established and there is
little undeveloped land along the shoreline. Tukwila's identity as a regionally significant industrial,
manufacturing, and commercial center will be maintained. Therefore, change within the shoreline will primarily
be the result of redevelopment activities. The proposed SMP provides a new system of shoreline environment
designations and river buffers that would protect shoreline resources and enable enhancement and restoration
actions. The updated development standards and regulation of shoreline modifications provides more protection
for shoreline processes. The updated standards and regulations are more restrictive of activities that would result
in adverse impacts to the shoreline environment. The restoration planning effort outlined in the proposed SMP
provides the City with opportunities to improve or restore ecological functions that have been impaired as a result
of past development activities. In addition, the proposed SMP is meant to compliment several city, county, state
and federal efforts to protect shoreline functions and values.
Based on the assessment of these factors, the cumulative actions taken over time in accordance with the proposed
SMP are not likely to result in a net loss of shoreline ecological functions from existing baseline conditions.
Instead, it is expected that the regulatory provisions of the proposed SMP would result in an overall improvement
of functions along the Green/Duwamish River. However, since most ecological functions along the Green River
are heavily influenced by conditions and activities throughout the upper watershed, the improvements are not
expected to be significant at the watershed scale. In concert with implementation of restoration actions in the city,
the regulatory provisions of the proposed SMP would serve to improve the overall condition of shoreline
resources in the city as redevelopment occurs.
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60
t Net Loss, Reac► G1 'implementation of
t �?reven ExPec tedfromimp
aced standards loss het Impact ns of SMP
F hods in Proposed SMp to prevent r
Risks to Ecos _t ii1 minimize risk
or minim
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t1d� 1� Risk would cause 5.1 slope ew
5Mp CumulativeF A c� �ctions that uld levee recon trollmgn corn banks at i ees exile
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Sects. to be constructe intertidal habitats. Ze for flood storage De ore natural
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Designati hypox functions
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Sedum sediment generation and p
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oversteea d some levee
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poorly h stornnvater detention hug enter river front Gilliam t rearm
north end of reach, ru es e es sib f
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(south er is of reach poo Quality –nutrient refs ftltrat and
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and nitrogen
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One w not including on right jurisdiction, ratan fringe Current situation of reach and removed
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of each. Tree levee. n Po wetlands, tivee a11v certified
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m id slope be 9.5, 9.6)
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4o.
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10)
No significant risks
�e sedimen significant impairment
transpor
r ve et atio n a l ong i (Sect.
val of g Y 5
remo ened batiks for Ian SM
t.and cle otn over -steep d cleating m control for
projects,
r
vet, lauds t remove fine etoston (current
secluding 125 ft (curt
Inadequate stomttvatet treatment to rem ider buffets 100 with limits
incre ent of w areas (Sect. 7 t.
pe diment and particulate Establishm leveed d uses (sect. 8)
buffer risk buffers 40 ft.) eveed an
impervious surface in blow risk due to ble situ oval and
vegetation on allowable plants
Increased imps prohibiting native vegetation removal
possible retention by enh ancement with native
existing development) Standards (except e t w federally certified levee
requiring w here
in buffer 0)
exists) (Sect 9.
of riverltloodplain interface
th rtherre duction
oTmg on over
h additional hard 01515
from eder Dec 200
shoreline jurisdiction Black f' f—"' sequencing, and tningau
Creek and acts Analysis
Gilliam "'y impacts, mitigation sea Cumulative Impacts t.. environmental imp Impacts/Final Cwn
Ana lysis of potential en ulative Imp
S3,1 waLongRangeProjects ,ShorelineiCum
acing, unles hard
Standards prohiba em new es (in that case mitigation
studies show no and standards for levee a bench
would be required) with a planted mid -slop
re pair/repla cement
(Sect.
throng 9 5 9 and tree
steepened banks With prohibiting native vegetation
e uiringbuffer vegetation
aeration and removal and r q
f Kees and native
station in the
I Removalo eg
reduction of fl
oodplatn area.
apply to all projects in the Shoreline jurisdiction
on (Sect. 9.8 of SW)
o/t
es accepted, 12109/2009
l u lbnpact chang
1 No Ne Loss Table -Cum
f 1
Opportun
provided for in
SM.? for restoration
provisions o f function
regulatory P Mitigationp j
leveed areas set of replace lost
vementi functions.
'Potential significant re coped to preferred 0500 profile to off-
Pozen area. Potential ects, as
they are re hat wider c e re slope expected Restoration Pgestotation
improve f non levee ev id entified in
No new °tease Plan, mostly m northern
i loo bioenginee
a t zone an de a part of mostly
eg(1t n orthern create a larger aquatic to w wetland reto river)
transition from
b pr otected.
11IA
141A
Wetlands will
I No change
No change ntiv for re
due to ince a L ile_ vegetating
ent (few existing ter re gulation s a ors in sloping and
provide greater
Slight s tovem d new stormw permit it t require stability at time of
Slug ermit teat wilcl and In°°t
more Po si t e treatment and new P during land redevelop
t o City MPs
respo t ides. d 8
more on site tte? vities.
co nstructio n
improvement when currently unpaved sites
Slight
redevelop due to wider buffer requirements and re
vegetation requirements
N
totectio ion p ects, per
due to vegetation p' the Restoration Plan
uirements, wider buffers, new levee
Improvement in some areas,
ent req Voluntary laying back and
and file with planted mid -slope bench.
planting of banks in
profde with plan g ,e for buffer
reduction and buffer re-
reduct
teach an d Shoreline
Designat
River, and Stream "E,
which is piped to
stonnwater pump station).
sw
jcosy stem Fun ction
es to the retention of eat and
floodplain contnbng of sedim
i n midi c f reach, but phosphorous Ro t� trapping the
ve getation ce waters
anderstary ve y eg¢tation in parts a generally groundwater and surface Boas overhanging k and ege tation that
reach (willows). Functional 1 buffers and large trees Sc ding)
narrow (largely restricted
fbattk o bank
Removal of e
e overhangs water (elimination to shin
narrow strip on rTemperatur a and
Quality a�dwater discharg Water Q Reduction in
temperature is a have
mature trees b
Current removed s ituation but certified levee
roblYem ved fi federally been Engineers s requirements and
per Corps of u a issue)
r land is fully with of reach and upland
with impervious surfaces (temperature
buffet (i.e., no
New incervious surfaces in
ocontaminants) and m
rent amioants filtering out watershed
Quality c ontributing
W ater Q
Bible sources of Untreated stormwater runoff
it land possible adjacent
Currents n (unpaved areas where
potential co pesticide out materials
heavy e land uses sung maintenance,
&e Use!siorage of ha
heavy ¢qui o landscape m o Na nce, s
(utilise*' use f snra!( quantities of
Excessive use of pesticides
storag
m aterials
Methods in p pp$ed SMP to prevent toss
Minimize rfslc
or min
Risks Would cause a net loss)
(actions that tv Sect 9,10).
native plants
'LWDIOrganic inputs
Large tree canoh bank.'" 1
Current situation- reach and on right removed
northern of parts of rein have been rem
much of reach, Tres
from federally certified lev
ration
Riparian buffers and over -win
Rip
Patting in buffer or patting in (oils
adequate stormwater treatment
Large tree remOVal
prohibit tree removal, w i t h m itigation
Standards S 9 .10), (however tree removal required
required mitigation for removed trees to be done
WD placem r e
on levee
elsewhere in shoreline' Lent
plane Standards requiring Te'veg
buffers.
buffer requiring
mitigation (Sect. S, 9
Standards controlling structures m
.2)
Standards prohibiting increase to runoff and
(Sect 9. airing
requiring (Sect. 8 9 structures ibtting increase
mitigation (Sect S. LID techniques
Standards requiring stormw i ues (Sat 9
Stan n ttechn q
low impact develop rue d coati
without
drips)
runoff and requiring nt and use of
inter treatment 4)
agency
plans, prohibiting prohibiti g spill prevention
within 100 R of
pl hibunng
sensitive area (Sect 9.12) dons
Standards that pCOhibition of (Sect fute
waste facilities m shor
controlling use of pesticides (Sect.
requirement for managem plans for areas
Standards etnent adjacent to river
requiring large turf manag
Le o rtDent tarfire facility).
(port Deni 4arklS
s for buffers Secr. 8
Uses�datd itingaanvevegera
g,10)•
Mitigation requirements that include addition of
LWD in river r with planted
Required profile forlevee 5 P� 100 or 125 ft
mid -slope width from
'Wetted from Implements
Net Impact DxP of SNIP
regulatory provisions
Slight improv ee t in win er t shade ture due to of trees
retentionlp
Potential improvement in water water regulatio e to SMcomplY and new p ety's fDESpermm
with City's NP
1
ton 01 r provided for in
SW for restoration
of functions
ve getation
cnt due to strengthe tree protection with
and future levee retorts
removal, tree Improvement
n memo te�ulations in SM Bch
v egetation
mi d slope
rohib eats for planting n ative planted
r Standards oval 4 re quireme nts ad trees $eCY.
removal and also, requirement to leave Las l users
vegetation, also, card to bwld'mgs
place unless a hazer
(Sect 91 1 le d of riparian buffers
hacemen
eat in quality and width 1 Improvem bench expected for sites that redevelop
40 R C°
increase in
Incre leYe Sect Z 7
vegetation removal, levee (if behind a led 12109(2004
Large tree and other g es accep
2 Cumul SmpaC. c hin °g
ter v egetation maintenance 1 No NetbossT
ImpaetsiVinal Cumulative Impacts Analysis Dec 2009 /G
W :tl..ong Range FroJ eCt ShorelinelCumlative
---rte s for
Education P
shoreline proPettY
L WD installation as part
I of restoration projects
m itigation
projects that
Restoration p
include buffer
Reach and Shoreline Ecosystem Function
Designation
Current situation— large tree canopy in
northern parts ofreach and on right bank in
much of reach. Trees have been removed
_from federally certified levee. Poor
understay vegetation in much of reach ,but
some overhanging vegetation in some areas
(willows). Functional buffers generally
narrow (largely restricted to bank and top of
bank only).
In- stream habitat for fish and wildlife
(especially for salmonids and bull trout)
Current situation—generally poor in stream
habitat due to channelization, levees and
steep armored banks. Some pools and riffles
from LWD in river and some beaches/mud
flats exposed at low tide in northern part of
reach.
Risks
ortun
Methods in proposed SMP to prevent loss regulatory provided for in
t provisions of SMP Implementation of PP ties
i
SMP for restoration
(actions that would cause a net loss) or minimize risk° of functions
improvements
Buffer reductions
Increased annoring on banks
New over -water structures (bridges are most
likely)
Large tree removal (elimination of shade,
source of future large woody debris, p erching
and nesting locations for birds). Removal of
native vegetation overhanging the river (shade,
food supply, source of large woody debris)
New hard shoreline amoring on over- steepened
banks
In/overwater structures with impacts on fish
passage, shading, habitat disruption
Filling of riparian wetland, off channel habitat
reduction of up to 50%
Standards that exchange for re-sloping bank d
nkand enhancing buffer
vegetation
Standards protecting trees and native vegetation and
re- vegetation requirements, and mitigation for
unavoidable vegetation removal (Sect 9.10.) (Note:
specific policy established for overhanging
vegetation)
Standards that require bioengineering techniques for
bank stabilization (Sect. 9.6)
Standards for overwater structures (Sect. 9.12)
Standards prohibiting native vegetation and tree
removal and requiring enhancement of buffers with
native, overhanging vegetation (Sect 9 10).
Standards controlling new hard armoring (Sect. 9.6),
encouragement of reducing steep slopes of banks
with native plantings (Sect. 7.7, in exch Inge for
r2.5:1
buffer reduction) and design profile for
slope with vegetated mid -slope bench.
Standards for in -water and overwater structures,
requirement for special studies to show no net loss,
mitigation requirements (Sect. 9.12)
Prohibition of wetland tilling, protection of Fish and
Wildlife Habitat Conservation Areas (Sect. 10)
3
Ran e Projects /Shoreline /Cumulative hnpacts/Final Cumulative Impacts Analysis Dec 2009/G1 No Net Loss Table Cumul Impact changes accepted, 12/09/2009
S.W W. /Long g
No change for width reduced buffers (maximum reduction
would be 50% in non -levee areas, which is still wider than
the current 40ft. Banks would be at natural angle of repose
and buffer would be enhanced with native plantings
resulting in a significant improvement ntover existing
riparian conditions. No chang e for
leveed areas, but levee mid -slope benches would provide
improved riparian habitat.
Improvement if banks are restabilized using
bioengineering techniques
No change if mitigation carried out and standards followed
Improvement over existing in- stream habitat, few in or
overwater structures expected, except for new pedestrian
bridge in this reach
Restoration projects to
increase in- stream habitat
esp. off- channel and near
channel areas
Voluntary laying back and
vegetating riverbanks
with native plants
rn
-NTukwila SMP Cu Impact Analysis Risks to Ecosystem Functions and Proposed Standards to Prevent Net L
Reach and Shoreline
Designation
Reach: G2
(Black River /Green River
confluence to north City
limit)
Designations: High
Intensity, Urban
Conservancy,
Shoreline Residential
Existing Land Use:
High Intensity Environment:
northernmost part of reach,
includes the turning basin:
industrial (truck parking,
aircraft industry),
transportation: private
vehicle bridge. Several
salmon habitat restoration
sites in turning basin (left
bank) off channel areas,
mud flats, riparian wetland.
Urban Conservancy-
Industrial, office,
commercial/warehousing,
institutional (Federal Post
office), recreational (Boeing
employees facility), Foster
Golf Course.
Significant impervious
surface existing except for
open space.
Recreational trail along river
in much of reach.
Southgate and Riverton
Creeks are tributary to river.
Ecosystem Function Risks
(actions that would cause a net risk
loss)
New hard shoreline armoring on over
steepened banks
Hydrology Channel/Flood Plain
Interaction: Surface storage, reducing
downstream flooding, habitat forming
processes, hyporheic functions
Current situation: generally constrained
due to channelization, .steep armored
banks (some eroding).
Hydrology Groundwater Recharge
Current situation: not a significant
fraction —valley is discharge area
Sediment Delivery fluvial transport
Current situation: not a significant
function process controlled and
affected at watershed level upriver from
•om
Tukwila
Sediment Delivery and Removal
upland fine sediment generation and
particulate retention
Current situation: nrostly impervious
surface in Urban Conservancy; some
unpaved area in High Intensity, unpaved
areas in Shoreline Residential, fine
sediment sources: unpaved parking lots,
residential gardens, upland sources
outside of Shoreline jurisdiction, which
contribute sediment to tributaries;
narrow, poorly vegetated buffers;
general lack ofstormwater treatment.
Water Quality nutrient retention and
removal (phosphorous through filtration
and retention and nitrogen removal
through denitrification)
Current situation: absence of large trees
in High Intensity Env. and much of
Urban Conservancy. Good tree cover in
New overwater /in -water structures
Loss of wetlands fish and wildlife
habitat areas due to filling/bank armoring
No significant risks
No significant risks for coarse sediment
transport impairment
Land clearing, removal of vegetation
along river, landslides from over
steepened banks, increased impervious
surface in buffer
Inadequate stormwater treatment to
remove fine sediment and particulates
Further reduction of river floodplain
interface through hard armoring on over
steepened banks
Removal of trees and native vegetation
and reduction of floodplain area.
Vegetation in the floodplain contributes
to the retention of phosphorous from the
Methods in proposed SMP to prevent loss or minimize
Standards controlling new hard armoring requiring bioengineering
techniques (Sect. 9.6).
Voluntary lay back of banks in exchange for buffer reduction of up to 50%
(excluding residential uses) (Sect. 7.6,7.7,7.8)
Standards controlling extent and design of new over -water structures (Sec
9.12), mitigation required (Sect. 9.12)
Sensitive areas protection provisions in SMP (Sect 10)
N/A
N/A
r Analysis of potential environmental impacts, mitigation sequencing, and mitigation (Sect. 9.8 of SMP) apply to all projects in the Shoreline Jurisdiction
1
Adequate stormwater treatment (Sect. 9 4) and increase in buffer width
from 50 ft to 100 ft in High Intensity and Urban Conservancy
Environments and from 20 ft to 50 ft in residential areas.(Sections 7.6, 7 7,
7.8)
Standards for land clearing in SMP (Sect. 9 11), including erosion
sediment control for projects
Standards prohibiting native vegetation removal and requiring vegetation
enhancement in buffer (Sect 9.10). Restrictions on what structures can be
built in buffer (Sect 8)
Standards prohibiting new hard armoring, unless studies show no
alternatives (in that case mitigation would be required) and standards for
levee reconstruction (Sect. 9.5, 9.6)
Standards prohibiting native vegetation and tree removal and requiring
vegetation enhancement in buffer for new /re- development (except
residential under 4 lots (Sect 9.10).
SW W: /Long Range Projects/Shoreline /Cumulative Impacts/Final Cumulative Impacts Analysis Dec 2009/G2 No Net Loss Table Cumul Impact changes accepted
oss, Reach G2
Net Impact Expected from
Implementation of regulatory
provisions of SMP
Slight improvement as failing banks are
stabilized with less steep slopes and
bioengineering techniques, if property
owners take advantage of incentive to
re -slope steep banks in exchange for
buffer reduction. Improvement in
overwater structures as old structures
are replaced. Increased channel width
would increase flood storage, create a
larger intertidal zone and provide a
more natural transition from aquatic to
upland habitats.
Slight im __era in protection of
sensitive areas
No change
No change
Significant improvement in High
Intensity area as area redevelops (where
little stormwater treatment exists and
many areas along river are unpaved)
Improvement in High Intensity and
Urban Conservancy due to wider
buffers and enhanced buffers planted
with dense native vegetation
Slight improvement over time as buffer
vegetation is enhanced through site
redevelopment, voluntary planting,
mitigation for over -water structures,
bank stabilization.
Opportunities provided for
in SMP for restoration of
functions
Mitigation projects to off -set or
replace lost functions
Restoration projects including
those that lay back banks and
create shallow intertidal areas and
off channel areas
N/A
N/A
Incentive built in for re- sloping
and re- vegetating banks to provide
greater stability at time of
redevelopment
Restoration projects
Voluntary riparian vegetation
enhancement
Reach and Shoreline Ecosystem Function
Designation
h reline Residential
Single Family residential,
parks open space
(Tukwila Community
Center, Codiga Park, future
Duwamish River Bend Hill
Park (partly in shoreline
jurisdiction), North Wind
Weir (both banks),
Duwamish Park. Streets
(42 "a Ave S S 155 s
dacent to river, with gravel err[ situation: potential
Risks
(actions that would cause a net
loss)
trapping of sediment and denitrificarion
Shoreline Residential and along Foster of citrate -N within the groundwater and
Golf Course. surface waters
Removal of large trees vegetation that
overhangs water (elimination of shading)
Current situation: high temperature is Increase in impervious surfaces
larger trees n igh nl rva s n cy Good tree ty Env. And (stonnwater temperatures)
large trees Urban H C o se oundwater discharge and
much o
cover in n SShorr Conservancy.
Residential and along Reduction sm gr
Foster Golf Course. New impervious sur in buffer (i.e.,
Water Quality contaminants no filtering out of contaminants) and in
contributing watershed
Water Quality Temperature
a j
Cw+
shoulders. contmnbtation f'onr ongoing industrial
activities in High Intensity Environment
(general lack of st onmvater treatment).
Lower risk in Urban Conservancy and
Shoreline Residential.
Unheated stonnwater runoff
Overwater structures (such as marinas or
boat yards) with transport, use or storage
of hazardous materials
Some contamination of sediments due to
Use/storage of hazardous materials
previously contaminated sites
Excessive use of pesticides /fertilizers
LWD /Organic inputs
Current situation absence of large trees
in High Intensity Env. dd tree cover co er in
Urban Conservancy
Shoreline Residential and along Foster
Golf Course.
Riparian buffers and overwater
vegetation
Current situation: all buffers narrow,
poor understo+y vegetation (mostly
invasive plants), poor tree canopy except
in Shoreline Residential and along
Foster Golf Course
Parking in buffer or parking in areas
without adequate stonnwater treatment
(oil drips)
Large tree removal
Removal of trees and native vegetation
Methods in proposed SMP to
risk'
Buffers increased from 50 ft to 100 ft
Conservancy Environments and from
2
prevent loss or minimize
in High Intensity and Urban
20 ft to 50 ft in residential areas.
Standards that prohibit tree removal with mitigation required (Sect 9.10)
Standards controlling structures in buffer requiring mitigation (Sect. 8,
9.2), prohibiting increase in runoff and requiring LID techniques (Sect 9.4)
Standards controlling structures in buffer requiring mitigation (Sect. 8,
9.2), prohibiting increase in runoff and requiring LID techniques (Sect 9 4)
Standards requiring stonnwater treatment (Sect 9 4)
ill prevention and contingency plans, prohibiting
Standards requiring spill
development within 100 ft of sensitive area (Sect 9.12)
Standards that limit use of treated pilings (Sect 9 12). Prohibition of
commercial hazardous waste facilities in shoreline jurisdiction (Sect 8).
Standards controlling use of pesticides (Sect. 9,10.D), requirement for
management plans for areas requiring large turf management adjacent to
river (golf course).
Use standards for buffers (Sect. 8), stonnwater treatment required (Sect.
9 4)
Standards prohibiting native vegetation removal, tree removal and
requirements for planting native vegetation (Sect 9 10).
Mitigation requirements that include addition of LWD (Sect. 9.10)
Standards prohibiting native vegetation and tree removal and requiring
buffer vegetation enhancement when redevelopment occurs (Sect 9 10). and
Buffers
onservancy Envi orunents g
and from 20 ft to 50 ft in Intensity residential Urban
areas.(Sections 7.6, 7 7, 7.8)
Buffer reductions in High Intensity
Environment Urban Conservancy up to
50% (no buffer reductions allowed in
Shoreline Residential Environment) in
exchange for re- sloping bank and planting
SW. W; /bong Range Projects /Shoreline /Cumulative Imp
acts /Final Cumulative Impacts Analysis Dec 2009 /02 No Net Loss Table Curnul Impact changes accepted
Net Impact Expected from Opportunities provided for
Implementation of regulatory in SMP for restoration of
provisions of SMP
functions
Some improvement expected tt s sites
redevelop. Little chang e protected
retention, as trees are already P
under separate tree ordinance, however
SMP tree protection is stronger.
Significant improvement expected in
High Intensity Environment as sites
redevelop (buffer vegetation
enhancement, stonnwater requirements
in SMP, and new NPDES requirements.
Also, improvements expected due to
clean -up actions under Superfund in
High Intensity Environment. Urban
Slight improvements
Conservancy and Shoreline Residential
Cons
Long -tent improvement in areas of
reach which have no large trees
currently (through requirements for re-
vegetating buffers upon redevelopment)
(source of LWD).
Slight improvement through LWD
replacement nrolects
Improvement in quality and width of
riparian buffers expected, for sites that
redevelop
No change for width reduced buffers
(maximum reduction would be 50% in
non -levee areas, which is still wider
at natural angle of repose and buf er
would be enhanced with native
plantings resulting in a significant
Voluntary tree planting,
stewardship education for
shoreline property owners
(planned)
Stewardship education for
property owners and City
maintenance crews.
Restoration projects with riparian
plantings, stewardship assistance
voluntary buffer restoration by
property owners
rn
C.)Reach and Shoreline Ecosystem Function
Designation
In -stream habitat for fish and wildlife
(especially for salmonids and bull trout).
Current situation: freshwater /saltwater
transition zone in northern part of reach.
Several new salmon habitat restoration
sites in turning basin and at North
Winds Weir (left bank) and Codiga Park
have added in -stream habitat— riparian
wetland mudflat/beaches, off
channeUbackwater areas.
Risks
(actions that would cause a net
loss)
with native vegetation
New bank armoring
New overwater structures (docks in
residential areas)
Removal of large trees that could form in-
stream habitat
Filling/dredging of riparian wetland, off
channel habitat
Methods in proposed SMP to prevent loss or minimize
risk'
Standards controlling new hard armoring and bank stabilization (Sect. 9.6)
Standards for in -water and overwater structures, requirement for special
studies to show no net loss, mitigation requirements (Sect. 9.12)
Buffers increased from 50 ft to 100 ft in High Intensity and Urban
Conservancy Environments and from 20 ft to 50 ft in residential
areas.(Sections 7.6, 7 7, 7.8)
Buffer reduction to no less than 50% in exchange for re- sloping bank and
stabilizing with bioengineering techniques including planting of native
vegetation to overhang water (Section 7.6, 7 7, 7.8)
Standards prohibiting native vegetation and tree removal and requiring
buffer vegetation enhancement when redevelopment occurs (Sect 9.10).
Standards controlling new hard armoring and bank stabilization (Sect. 9.6)
Standards for in -water and overwater structures, requirement for special
studies to show no net loss, mitigation requirements (Sect. 9.12)
Prohibition of wetland filling, protection of Fish and Wildlife Habitat
Conservation Areas (Sect. 10)
3
SW W:/Long Range Projects/Shoreline /Cumulative Impacts/Final Cumulative Impacts Analysis Dec 2009/G2 No Net Loss Table Cumul Impact changes accepted
Net Impact Expected from
Implementation of regulatory
provisions of SMP
improvement over existing riparian
conditions. No change for reduced
buffers in leveed areas, but levee mid
slope benches would provide improved
riparian habitat.
Improvement if banks are restabilized
using bioengineering techniques
No change if mitigation carried out and
standards followed
Potential improvement
Opportunities provided for
in SMP for restoration of
functions
Restoration projects prioritized in
transition zone esp. oft channel
and back channel areas
SAP Cumulative Fact
and osystena "Function
eac and Shoreline
Designati
retention
pa)vsi5^ Vasks to Ecosystem cause a net I �inimitie risk would
A gisks factions that
loss)
Channel/F
plain
Hydrology' storage, reducing
1 Interaction: Surfa habitat forming
Reach; CT ban ream flooding, habitat f
Designation/ Ur downstream
hypotheic functions
Conservancy actual interaction
situation: little t k ith o ver
d u e to s certi ied levee
Ilse: a nd tributary watercourse
LandU duero»an-
(Curr
ent uuture, rT s huctur flo d steepened bank lr levee into river
t
1 e veethr e tha fl ¢charg
Agra coon, t Fu's
Shore m h emir Gtoun
length (not
h cross Cur v alley
certifie 90 Ate discharge area �anspnrt
valley m is in t oc ¢ss
from S. oodplain
f with small portion in
Ne w cross valley
Shoreline Jurisdiction
develop m tributary and stream relocation t Johnson
developm
Creek
110 significant risks
control levee throng H y drology n ot a significant ttndwaier
Federally rent situation. is a tisks foz coarse sediment
'tin significant ens
dlevee) w i t a function river ttimpatr
e at S 1 fluvial transpor l90 south SednnentDelivery funcnon p el meet
affected at 'watershed ley for site develop
(duet mapped fl t a significa w roces f Grading and filling
(due to non -certified levee)• Not and a lnvi a upland I M change will be i li Sediment t T an d Retention p
w cross Delivery and particulate
requeste
furthe south. e stalled fin s e invent generation
valley levee to be m fine sedimen further south. ntf of
Lamds e
leve
used Standards toy prevent loss or t lv het Impact tcte
y pe o SMP
Standards for new and rebuilt levee const
d px0 0£ regulatory provisions
hods in Proposed SMp to prev
-Functions an
coon requiring
ru
less steep slope (Sect. 9.5)
Sensitive areas provisions in SMp (Sect 10)
N1A
lidestfailures on over steepened banks of
water treatment to %move fine
N 1A
n
sediment Inadequate st
Current situation: e¢ lower 1r adeq d articulates
and behind levee sediment equ o s p
oth top of activities s does no o to river
dir o ftev¢¢1, but could flow
than top small, interface
via tributary strewn th has over-
inadequate buf Further reduction of riverffl o
nadeq through additional hard armoring
nutrient through retention an teed banks of levee
wa uality filtza steep
ca l (phosp
/ion a nit' gee Te oval through' i trees and native vegetation from
removal and nittoge rebuilt levee
Removal of h areas o[ from area.
and retention newly restored o floodpla
d tuat benc hes and d areas o con t le es to the
of
titde s o m e has
Vegetation in the floodplam the trapping to thwithin
Cu situation 9 r ith retentio of phosphorous fro ofnittat :11
vegetation present in evee main w en itriftcati on
removed t° eat and d fact f nit
been r ecently sedim
f gngineef•s levee niaint¢nane the groundwater and sits
Corps o
standard
ent (Sect. 9 4), and new
water treatment implement new and 14P1DES
ne
Standards for storm to
City stormwa' regulations
T
Standards for land clearing in construction
erosion sediment control
erosion sedim mid-slope b
r equiremen ts
(Sect. 9.11), including
nSMp( n
benches in re-
built ((Sect) 10) required nd wider ivegetated buffers on
Sect 9.1
I b ilt levees tream
U
restored ttibutary s with vegetated mid -slope
Standards for levee construction
hie removal
Standards prohibiting native vegetation and
(Sect 9 10).
bench (S e
ct 9 5)
horeline Jurisdiction es accepted, 12109/2009
1 to all projects in the S h Cumul Impact chang
9.8 of NoNefLossTable
d mitigation (Sect. 9. Dec 20091G1? AA anon sequencing, an acts Analysis D
v ronmemtal impacts, m itigation Analysis of potential en
Impacts/Final Cumulative Impacts SW lLo( gRzngeRroJecUShorelinelCumulative
Reach Opportuni
G tLosS d goer I provided for in
SW for
restoration of
function
meat: levee
ent due to planned icfuture 1 provide slightly
Tovem htl
Improvement (lay back steep slope); prop o
re construc tion
eG OnstN and less acts to include off
m chan fr development impacts 2 6 upland t 5
open te1 salmon habitat
butary stream improvements,
crease flood storage and
open water) and
Increased larger intertidal in width would
c reate a large ut errtidal zone..
-trio change
o change
Two restoration
ed future development projects identified in
ent P
with plaint this reach e t° identified Improvement expected permanent stortmwateT manage(' can out by
Imp o f new stonnwat lea wily
and p er of "f uk be
due to temporary implementation develop
staards f requirements an DES permit. South project awetland
standards for NR mitigation for a (fun)
and watercours
impacts
N
Imprnv
anent as levee is rebuilt and mid -slope benches
d vegetation matures
are planted
O ff-channel r e,storation
project as mentio
above
Water Quality Temperature
Current situation: high temperature is
problem for salmonids little to no
riparian vegetation in this reach, no large
trees
Water Quality contaminants
Current situation agricultural practices
possible source of contamination
(fertilizers, pesticides)
LWD /Organic inputs
Current situation: brier comprised of
levee with little native riparian vegetation
Riparian buffers and overwater vegetation
Current situation: high temperature is
problem for salnonids little to no
riparian vegetation in this reach. Buffer
largely taken up by levee)
In -stream habitat for fish and wildlife
(especially for salmonids and bull trout).
Current condition: virtually no adequate
in- stream habitat due to channelization
and levee. Stream discharges via non-
fish-friendly culvert and flap gate through
levee
Removal/topping of large trees vegetation that
overhangs water (elimination of shading)
Increase in impervious surfaces (stormwater
temperatures)
Reduction in groundwater discharge and base
flows
Untreated stormwater runoff
Use/storage of hazardous materials
Excessive use of pesticides for landscape
maintenance
Parking in buffer or parking in areas without
adequate stormwater treatment (oil drips)
(possible use prior to levee set -back)
Minimal risks from site redevelopment little
opportunity for LWD
Increased buffer widths from 50" to 125
Buffer reduction after levee setback and
installation of mid -slope planted bench
(expected maximum reduction of 25 ft).
Low risks due to non existence of in -stream
habitat
Standards that prohibit tree removal with mitigation
required (Sect 9.10)
Standards controlling structures in buffer requiring
mitigation (Sect. 8, 9.2), prohibiting increase in runoff and
requiring LID techniques and adequate stormwater
treatment (Sect 9 4)
Standards controlling structures in buffer requiring
mitigation (Sect. 8, 9.2)
Standards requiring stormwater treatment and use of low
impact development techniques (Sect 9 4)
Standards requiring spill prevention and contingency plans,
prohibiting development within 100 ft of sensitive area
(Sect 9.12)
Prohibition of commercial hazardous waste facilities in
shoreline jurisdiction (Sect. 8).
Standards controlling use of pesticides (Sect. 9.10.D
Use standards for buffers (Sect. 8), stormwater treatment
required (Sect. 9.4)
Mitigation requirements that include addition of LWD
(Sect. 9.10)
Section 7.7.C. Buffer designations
Widening of buffer from 50ft currently to 125 ft to
accommodate eventual levee setback (Section 7.6.C, and
standards for flood hazard reduction (Section 9.5) requiring
2.5:1 slope, vegetated mid -slope bench, which will create
shallow water areas along levee in high water.
2
S.W W: /Long Range Project/Shoreline /Cumulative Impacts /Final Cumulative Impacts Analysis Dec 2009 /GIPAA No Net Loss Table Cumul Impact changes accepted, 12/09/2009
Slight improvement when levee is rebuilt allowing for
planting overhanging vegetation and trees on mid -slope
bench.
Improvement due to SMP standards and new stormwater
regulations to comply with City's NPDES permit
Improvement when site redevelops LWD will be
incorporated into new off channel habitat area (see
below) and trees will be planted on mid -slope bench
when levee rebuilt.
No change (due to levee maintenance to prevent large
trees)
Eventual improvement in over -water vegetation/shading
when levee reconstruction completed and mid -slope
bench is planted (including over hanging vegetation) and
vegetation matures
When levee is reconstructed, some fish and wildlife
habitat will be created by planting on the mid -slope
bench.
Through mitigation for site development, owner will
carry out off channel salmon habitat area of 8 acres (6
upland, 2 open water) and tributary stream
improvements, including riparian vegetation and more
fish friendly culvert and flap gate.
Tukwila SMP Cumulative Impact Analysis Risks to Ecosystem Functions and Proposed Standards to Prevent Net Loss, G2 -PAA
Reach and Shoreline Ecosystem Function Risks Methods in proposed SMP to prevent loss or minimize risk`
Designation (actions that would cause a net loss)
Current Land Use:
water dependent (boat
building, marina, marine
industrial) and non -water
dependent industrial (Seattle
City Light substation)
Reach: G2 -PAA
Designation: High
Intensity
Possible redevelopment
potential adjacent to Hamm
Creek Restoration site on
north).
No levees, some bulkheads
and armored banks. Two
salmon habitat restoration
projects in reach: Harem
Creek and Seattle Fleets and
Facilities mitigation site.
Hydrology Channel/Flood
Plain Interaction: Surface
storage, reducing
downstream flooding,
habitat forming processes,
hyporheic functions
Current situation: channel
constrained by armoring
and bulkheads except where
Hamm Creek was restored
and flows into river and
newly restored site on south
side of Seattle City Light
property
Hydrology Groundwater
Recharge
Current situation: not a
significant function, river
valley is a groundwater
discharge area
Sediment Delivery fluvial
transport
Current situation: not a
significant function
process controlled and
affected at watershed level
upriver from Tukwila
Sediment Delivery and
Removal upland fine
sediment generation and
particulate retention
Current situation: fine
sediment could enter river
from tributaries, unpaved
parcels, and parking lots
and very little riparian
vegetation, and narrow
buffers preclude retention of
particulates
New or rebuilt/maintained bulkheads, new
shoreline armoring on over- steepened banks
New overwater /in -water structures
Filling loss of newly created wetlands fish and
wildlife habitat areas
No significant risks
No significant risks for coarse sediment transport
impairment
Land clearing, removal of vegetation, landslides
from over steepened banks, bank stabilization
projects without adequate erosion controls
Increased impervious surface in buffer w/o possible
retention by vegetation
Inadequate stormwater treatment to remove fine
sediment and particulates
Incentive for re- sloping and bioengineered bank to a 3:1 slope plus 20 ft setback (in
exchange for buffer reduction maximum buffer reduction allowed is 50ft, which
would still provide for a wider channel width). (Sect. 7.8.B.)
Standards controlling new hard armoring (Sect. 9.5, 9.6)
Analysis of potential environmental impacts, mitigation sequencing, and mitigation (Sect. 9.8 of SMP) apply to all projects in the Shoreline Jurisdiction
1
Standards controlling extent and design of new over -water structures (Sec 9.12),
mitigation required (Sect. 9 12)
Sensitive areas provisions in SMP to prevent filling, other impacts (Sect 10)
N/A
N /A-
Standards requiring adequate stormwater treatment (Sect. 9 4) and increased
minimum buffer width (Sect. 7). Also, new stormwater regulations under
development to meet new NPDES requirements.
Standards for land clearing in SMP (Sect. 9.11), including erosion sediment
control for projects.
Increased buffer width from 50 (current) to 100 R for new development (Sect
7.8.B). Restrictions on what structures can be built in buffer (Sect 8)
Possible buffer reduction in exchange for re- sloping and vegetating bank no greater
than 50
Standards prohibiting native vegetation removal and requiring planting of native
vegetation (Sect 9 10).
Standards for bank stabilization projects (Sect. 9.6)
S. W
W: /Long Range Projects /Shoreline/Cumulative Impacts/Final Cumulative Impacts Analysis Dec 2009 /G2PAA No Net Loss Table Cutnul Impact changes accepted 12/09/2009
Net Impact Expected from
Implementation of
regulatory provisions of
SMP
Slight improvement wider
channel width on sites that re-
slope bank and use bioengineering
techniques, unless new water
dependent uses go in.
No change if existing water
dependent uses stay. Increased
channel width would increase
flood storage, create a larger
intertidal zone and provide a more
natural transition from aquatic to
upland habitats.
No change to existing wetland and
fish and wildlife habitat projects
installed as restoration.
No change
No change
Significant improvement in water Section 7.8.B. Establishment of
quality mainly due to City's new River Buffer
stormwater regulations (under Vegetation enhancement at time
development now). of re- development as noted above
Slight improvement in water
quality due to new buffer width
No change in buffer width over
existing buffer requirements, but
significantly improved riparian
quality, if buffer reduction
granted.
Decrease in fine sediment from
Opportunities provided for
in SMP for restoration of
functions
Mitigation projects to off -set or
replace lost functions Transition
Zone is highest priority for
restoration projects and to direct
off -site mitigation efforts
each and Shoreline Ecosystem Function Risks
Designation (actions that would cause a net Loss)
Water Quality nutrient
retention and removal
(phosphorous through
filtration and retention and
nitrogen removal through
denitrification)
Current situation —very
little riparian vegetation
present in reach
Water Quality
Temperature
Current situation: high
temperature is problem for
salmonids little riparian
vegetation in this reach,
except for recent restoration
projects and no large trees
currently
Water Quality
contaminants
Current situation: existing
industrial uses, existing
impervious surfaces many of
which do not have
stornnvater treatment and
are not tied into the City's
system,- buildings and
parking (about 2/3 of
Shoreline Jurisdiction and
some vacant, unpaved land
about I/3 ofjurisdiction;
structures in buffer).
Further reduction of river /floodplain interface
through hard armoring on over steepened banks
Removal of trees and native vegetation and
reduction of floodplain area. Vegetation in the
floodplain contributes to the retention of
phosphorous from the trapping of sediment and
denitrification of nitrate -N within the groundwater
and surface waters
Removal of large trees vegetation that overhangs
water (elimination of shading)
Increase in impervious surfaces (stormwater
temperatures)
Reduction in groundwater discharge and base flows
New impervious surfaces in buffer (i.e., no filtering
out of contaminants) and in contributing watershed
Untreated stormwater runoff
Overwater structures (such as marinas or boat
yards) with transport, use or storage of hazardous
materials
Use/storage of hazardous materials
Parking in buffer or parking in areas without
adequate stormwater treatment (oil drips)
Methods in proposed SMP to prevent loss or minimize risk'
Standards prohibiting new hard armoring, unless studies show no alternatives (in
that case mitigation would be required) (Sect. 9.5, 9.6)
Standards prohibiting native vegetation and tree removal (Sect 9.10).
Standards that prohibit tree removal with mitigation required (Sect 9.10)
Standards controlling structures in buffer requiring mitigation (Sect. 8, 9.2),
prohibiting increase in runoff and requiring LID techniques (Sect 9.4)
Standards controlling structures in buffer requiring mitigation (Sect. 8, 9.2),
prohibiting increase in runoff and requiring LID techniques (Sect 9.4)
Standards requiring stormwater treatment and use of low impact development
techniques (Sect 9.4). Also, new stormwater regulations under development
responding to new NPDES permit requirements.
Standards requiring spill prevention and contingency plans, prohibiting
development within 100 ft of sensitive area (Sect 9.12). Also, new stormwater
regulations under development responding to new NPDES permit requirements
Standards that limit use of treated pilings (Sect 9.12). Prohibition of commercial
hazardous waste facilities in shoreline jurisdiction (Sect. 8).
Use standards for buffers (Sect. 8), stonnwater treatment required (Sect. 9.4). Also,
new stormwater regulations under development responding to new NPDES permit
requirements
2
S. W
W: /Long Range Projects/Shoreline /Cumulative Impacts/Final Cumulative Impacts Analysis Dec 2009 /G2PAA No Net Loss Table Cumul Impact changes accepted 12/09/2009
Net Impact Expected from
Implementation of
regulatory provisions of
SMP
landslides if banks are re- sloped to
3:1.
Improvement in riparian
vegetation and in sediment and
particulate retention
Significant improvement in water
quality mainly due to City's new
stormwater regulations (under
development now).
Slight improvement in water
quality due to new buffer widths
and vegetation requirements
(including replacement tree
plantings in transition zone).
Opportunities provided for
in SMP for restoration of
functions
Restoration projects
Laying back banks
Installation of native vegetation
that overhangs banks
Reach and Shoreline Ecosystem Function Risks Methods in proposed SMP to prevent Toss or minimize risk'
Designation (actions that would cause a net loss)
LWD /Organic inputs Large tree removal
(Current situation: no large
trees, little overhanging
vegetation in the reach)
Riparian buffers and over- Insufficient width for adequate buffer function Requirements to increase current buffer of 50ft to 100 ft (Sect 7.8.B)
water vegetation
(Current situation: narrow
to non existent buffers, little
riparian vegetation except
in restored sites)s
In- stream habitat for fish
and wildlife (especially for
salmonids and bull trout).
Freshwater /Saltwater
Transition Zone with off
channel habitat
Current situation: little in-
stream habitat except for
two small restoration sites
that created riparian
wetland and shallow water
habitat. This area contains
the turning basin, which is
regularly dredged by the
Corps of Engineers thus
opportunity to create in-
stream habitat is limited.
Bulkheads and impervious surface
New in/overwater structures with impacts on fish
passage, shading, habitat disruption
Filling of riparian wetland, off channel habitat
Standards prohibiting native vegetation removal, tree removal and requirements for
planting native vegetation (Sect 9.10).
Mitigation requirements that include addition of LWD to shoreline ecosystem (Sect.
9.10)
Possible buffer reduction allowed in exchange for re- sloping and vegetating bank
(no more than 50% reduction allowed, but significant improvement in riparian
condition
Standards for in -water and overwater structures, requirement for special studies to
show no net loss, mitigation requirements (Sect. 9.12)
Prohibition of wetland filling, protection of Fish and Wildlife Habitat Conservation
Areas (Sect. 10)
3
S. W
W: /Long Range Projects /Shoreline/Cumulative Impacts/Final Cumulative Impacts Analysis Dec 2009 /G2PAA No Net Loss Table Cumul Impact changes accepted 12/09/2009
Net Impact Expected from
Implementation of
regulatory provisions of
SMP
No change from current tree
removal prohibition.
Significant improved riparian
vegetation and trees over long-
term for properties that redevelop
Significant improvement in
riparian buffers if sites redevelop.
Even with buffer reduction, there
will be no change in buffer width
but significant improvement in
bank stability and riparian
vegetation.
Improved conditions for
salmonids if new overwater
structures built or old ones are
upgraded.
Fish and Wildlife habitat
restoration areas protected
Opportunities provided for
in SMP for restoration of
functions
Adding LWD to reaches as
mitigation and as part of
development projects
Restoration projects prioritized in
transition zone esp. off channel
and near channel areas
Laying back and vegetating river
banks with native plants