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Kennydale Lakeline Sewer System Replacement Project VEGETATION MANAGEMENT PLAN
Prepared for:
Carollo Engineers, Inc. May 2025
Exhibit 9
RECEIVED
07/30/2025
amorganroth
PLANNING DIVISION
Docusign Envelope ID: A6950DB9-F338-45C7-991A-0D2425171124
Kennydale Lakeline Sewer System Replacement Project VEGETATION MANAGEMENT PLAN
Prepared for:
Carollo Engineers, Inc. 1200 Fifth Ave, Suite 900 Seattle, WA 98101
Prepared by:
Confluence Environmental Company Audrey Michniak Marlene Meaders Margaret Wolf Tree Solutions Inc. Consulting Arborists Tyler Bunton
May 2025
This report should be cited as:
Confluence (Confluence Environmental Company) and Tree Solutions Inc. Consulting Arborists (Tree Solutions). 2025. Kennydale Lakeline Sewer System Replacement Project: Vegetation management plan. Prepared for Carollo Engineers, Seattle, Washington, by Confluence, Seattle, Washington.
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Kennydale Lakeline Sewer System Replacement Project: Vegetation Management Plan
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TABLE OF CONTENTS
1.0 INTRODUCTION ................................................................................................................................................... 1
1.1 Project Description .................................................................................................................................. 3
1.2 Phase 1: Upland Construction................................................................................................................. 4
1.3 Phase 2: In-Water Construction .............................................................................................................. 5
1.4 Existing Conditions .................................................................................................................................. 5
1.4.1 Vegetation ................................................................................................................................. 5
1.4.2 Trees ......................................................................................................................................... 6
1.4.3 Critical Areas............................................................................................................................. 6
1.4.4 Soils and Hydrology .................................................................................................................. 7
1.5 Construction Schedule and Duration ....................................................................................................... 7
2.0 VEGETATION CONSERVATION BUFFER .......................................................................................................... 8
2.1 Definition and Delineation (RMC 4-3-090) .............................................................................................. 8
2.2 Replacement Requirements (RMC 4-4-130) ......................................................................................... 10
2.3 Potential Impacts ................................................................................................................................... 11
3.0 VEGETATION MANAGEMENT PLAN ............................................................................................................... 13
3.1 Preservation .......................................................................................................................................... 13
3.2 Enhancement and Restoration .............................................................................................................. 13
3.3 Establishment of New Vegetation ......................................................................................................... 13
3.4 Tree Retention and Planting.................................................................................................................. 14
3.5 Restoration Performance ...................................................................................................................... 15
3.5.1 Environmental Goals and Objectives ...................................................................................... 15
3.5.2 Performance Standards .......................................................................................................... 15
4.0 MAINTENANCE, MONITORING, AND REPORTING ......................................................................................... 16
4.1 Maintenance Activities .......................................................................................................................... 16
4.2 Monitoring Plan ..................................................................................................................................... 17
4.2.1 Transects and Photo Points .................................................................................................... 17
4.2.2 Percent Survival ...................................................................................................................... 17
4.2.3 Percent Cover ......................................................................................................................... 18
4.3 Reporting ............................................................................................................................................... 18
5.0 CONTINGENCY PLAN ....................................................................................................................................... 19
5.1 Plant Mortality ....................................................................................................................................... 19
5.2 Native Species Percent Cover .............................................................................................................. 19
5.3 Invasive Species Percent Cover ........................................................................................................... 19
5.4 Plan Revisions ...................................................................................................................................... 20
6.0 REFERENCES .................................................................................................................................................... 20
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TABLES Table 1. General information by phase for the Kennydale lakeline project .................................................................... 3
Table 2. Tree sizes and associated credits per RMC 4-4-130 ..................................................................................... 10
Table 3. Proposed project impacts to vegetation and trees by phase .......................................................................... 11
Table 4. Vegetation impact and restoration quantities (open-cut methods) ................................................................. 14
Table 5. Tree removal and planting locations (trenchless construction) ...................................................................... 14
Table 6. Performance standards for the Kennydale lakeline project ............................................................................ 15
FIGURES
Figure 1. Kennydale project parcels and existing lakeline sewer system location ......................................................... 2
Figure 2. Shoreline designations and vegetation conservation buffer. ........................................................................... 9
Figure 3. Vegetation impacts on public lands. ............................................................................................................. 12
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Kennydale Lakeline Sewer System Replacement Project: Vegetation Management Plan
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1.0 INTRODUCTION
The Kennydale Lakeline Sewer System (Kennydale lakeline system or lakeline system) is owned
and operated by the City of Renton (City) and provides sanitary sewer service to Kennydale
Beach Park and 56 properties along Lake Washington from the north end of Gene Coulon
Memorial Beach Park to just south of May Creek (Figure 1). The 4,680-foot-long lakeline system
consists of a flush station, an 8-inch cast iron sewer pipe buried offshore in Lake Washington, 3
manholes, and a system of 37 gravity side sewer laterals connecting customers to sewer
treatment. The Lake Washington No. 2 lift station pumps the flow from the lakeline system (in
addition to flow from the basin to the north) to the King County Eastside Interceptor, the
regional conveyance system to South Plant, where it is treated. The Kennydale lakeline system
is a low-pressure system that operates by collecting fresh lake water via an intake pipe at the
flush station located at the north end of Gene Coulon Park and pumping water through the line
to convey wastewater collected by the lateral connections to the Lake Washington No. 2 lift
station at the north end of the lakeline near North 40th Street. The initial 300 feet of the lakeline
system is onshore and the rest is predominantly buried below the lakebed, within
approximately 50 feet of the shoreline.
From 2016 to 2019, the City conducted an assessment of the Kennydale lakeline system, which
included an attempt to clean and video inspect the entire system in 2018. Due to its location,
varying water depth and pipe grade, lack of access points, and the original construction
methods used, the City was only successful in cleaning and inspecting approximately 80% of
the lakeline system. As part of the hydraulic assessment, it was concluded that the hydraulic
capacity of the Kennydale lakeline system is reduced, indicative of partial blockages in two
general areas. These partial blockages are likely the result of solids settlement caused by
velocities below those needed for self-cleaning, delamination of the interior lining of the pipe,
and settlement of the lakeline infrastructure over time resulting in undulating slopes with high
and low points that prevent full evacuation of wastewater. Current access from the shoreline for
cleaning is limited, and settled solids cannot effectively be removed using.
The Kennydale Lakeline Sewer System Replacement Project (the project) is being designed and
permitted per applicable regulatory requirements. Once the replacement system is complete,
the existing lakeline system will be decommissioned.
Construction of the project will result in the removal of vegetation and trees at the project site.
This document, the Vegetation Management Plan, serves to fulfill those requirements of Renton
Municipal Code (RMC) specified under the Shoreline Master Program Regulations (RMC 4-3-
090), RMC 4-3-050 (Critical Areas Regulations), and the Tree Retention and Land Clearing
Regulations (RMC 4-4-130). This document provides information on vegetation and tree
management required under the RMC that is not met in full by the Landscape Plan (Permit
Drawing Sheets LS01 to LS12) or Arborist Report (Tree Solutions 2025) alone.
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Figure 1. Kennydale project parcels and existing lakeline sewer system location
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1.1 Project Description
The purpose of the project is to provide reliable and easily maintainable sewer service to Renton
shoreline residences that integrates with the existing sewer conveyance and pumping system
and that has the least aquatic environmental impact possible. This project is needed because the
existing Kennydale lakeline system that was installed in Lake Washington in 1972 is reaching
the end of its useful life and is unable to be maintained in its current location. The following is a
brief summary of the proposed project for context in the Vegetation Management Plan. Details
of the proposed action and construction methods are provided in Confluence (2025a).
There are two phases of the work: (1) upland, and (2) in-water. The general information for each
phase is identified in Table 1.
Table 1. General information by phase for the Kennydale lakeline project
Category Phase 1 Phase 2
Project Information
Name Upland Work In-Water Work
Length 4,950 LF 4,680 LF
Location City ROW, City property, private
residences, and public parks Lake Washington (Lakeline) and just upland from Lake Washington (Flush Station, Lift Station)
Section/ Township/ Range
S32, T24N, R5E S31, T24N, R5E S6, T23N, R5E
S32, T24N, R5E
S31, T24N, R5E
S6, T23N, R5E
Zoning Residential-8, Residential-6
Aquatic (Lakeline),
Residential-8 (Flush Station)
Residential-6 (Lift Station)
Shoreline Designation Single Family Residential, Urban Conservancy Aquatic (Lakeline),
Single Family Residential (Flush Station)
Project Cost $10.1 million $615,000
Materials Excavation 9,562 CY 33 CY
Fill 9,562 CY 39 CY
Distance from OHWM 5 to 200 feet from the shoreline (upland grinder pump stations)
~50 feet from the shoreline (in-water lakeline)
33 feet from the shoreline (upland flush station)
19 feet from the shoreline (upland lift station)
Water Depths N/A 6 to 20 feet (Lakeline)
CY = cubic yards; LF = linear feet; OHWM = ordinary high water mark; ROW = right-of-way
The proposed action is summarized below in Section 1.2 for the upland phase and Section 1.3
for the in-water phase. Additional details on construction methods, site access, operations and
maintenance of the replacement sewer system, and conservation measures used during
construction for both phases of the work can be found in the Project Narrative and Code
Consistency Analysis (Confluence 2025a).
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1.2 Phase 1: Upland Construction
Phase 1 of the project includes installing a new land-based sewer system that includes a low-
pressure sanitary sewer force main (or main line), discharge laterals, and grinder pumps. A
total of 54 private residences and the Kennydale Beach Park will connect to the new main line
via discharge laterals from the front, back, or side yards of each property and the park. There
are 2 residences that are currently served by the Kennydale lakeline system that will connect to
a gravity system instead of a grinder pump. The new main line and discharge laterals will be at
a minimum of 3 feet deep. Each house will have its existing gravity sewer line rerouted to its
own grinder pump station with the 2 exceptions stated above. The discharge pipe
(approximately 1 ¼ inches in diameter) from the grinder pump stations will be routed to the
new main line that will be installed within Mountain View Ave N or the unnamed access road
that is part of the King County Parks right-of-way (ROW) to the east and upland of the existing
private residences.
Phase 1 covers a total parcel area of approximately 1,681,600 square feet (SF), or 39 acres, which
includes 62 parcels, a linear force main in adjacent roadways that is approximately 3,000 linear
feet (LF), and discharge laterals that add up to approximately 5,000 LF. A total of 55 grinder
pumps will be added to service the private residences and Kennydale Beach Park. The total
ground surface disturbance includes approximately 113,670 SF, which is a small portion of the
total parcel area. Note that the value for disturbance area adds approximately 15% to the
anticipated impact values to account for potential changes during final design. Discharge
laterals may be installed using trenchless methods, which would reduce the amount of surface
disturbance.
A grading plan was prepared in accordance with RMC 4-8-120D.7, and showing contour
intervals of 2 feet where slopes are less than 10% and 5 feet where slopes are 10% or greater. The
grading plan is provided within Sheets C01 to C10 of the Project Drawings.
Temporarily affected areas will be restored in-kind to existing conditions. Vegetation will be
replaced at a 1:1 ratio using native species or replacing landscaped species. There are a total of
4 significant trees proposed to be removed and 13 significant trees impacted outside of critical
areas or buffers if trenchless methods are used to install the discharge laterals. There are a total
of 21 significant trees proposed to be removed and 13 significant trees impacted outside of
critical areas or buffers if open-trench methods are used to install the discharge laterals.
Replacement of significant trees are calculated per parcel and discussed below assuming
trenchless construction methods. The information below provides details on the location and
type of restoration for each area that is disturbed.
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1.3 Phase 2: In-Water Construction
Phase 2 of the project primarily involves in-water construction activities focused on the
decommissioning of the existing lakeline sewer system. These activities include the removal of
3 manholes and capping of flush station components. This work will not affect upland
vegetation.
There is a limited amount of work in upland areas associated with decommissioning the flush
station (APN 0523059010) and upgrades to Lake Washington Lift Station 2 (APN 3342700011).
The primary work at the flush station will include removing the interior components and
adjacent appurtenances of the flush station (the shelter, antenna, light, etc.). The above-grade
electrical/controls shelter, electrical vault, antenna, and site lighting will be removed.
The Lake Washington Lift Station No. 2 is located on-land on the northern end of the lakeline
system (APN 3342700011). In addition to lakeline system flow, the lift station collects flow north
of the station from an upland gravity system and will remain with minor upgrades to its
Supervisory Control and Data Acquisition (SCADA) and electrical systems to allow for
connection to the new permanent generator. A small retaining wall will be added to protect the
new generator. The area of the transformer and generator may require a retaining wall or other
slope stabilization method and appropriate screening as required by code. These minor
upgrades will result in approximately 500 SF of new impervious surface area.
Site access for the upland work will occur from City ROW directly adjacent to the site.
Additional details for the Phase 2 work are provided in the Project Drawings (Sheets D01 to
D02).
1.4 Existing Conditions
The following sections provide a summary of existing conditions for vegetation, trees, critical
areas, soils, and hydrology within the project area, based on available information and the
Arborist Report (Tree Solutions 2025).
1.4.1 Vegetation
The project site includes a mix of native and non-native vegetation, with coverage varying by
location. Riparian vegetation along the waterside of the shoreline associated with the lakeline
system is primarily lawn and ornamental shrubs with some native and non-native grasses. The
overall health of the vegetation varies. Areas with established native vegetation exhibit
moderate to high health, whereas disturbed zones, particularly near developed areas, show
reduced vigor and encroachment by invasive species. Invasives species present include,
Himalayan blackberry (Rubus armeniacus), English ivy (Hedera helix), and reed canarygrass
(Phalaris arundinacea).
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Landscaping coverage within the project site is identified in the Project Drawings. The plant
schedule to replace landscaped species include tall Oregon grape (Mahonia aquifolium), nutka
rose (Rosa nutkana), snowberry (Symphoricarpos albus), kinnikinnick (Arctostaphylos uva-ursi),
beach strawberry (Fragaria chiloensis), and lawn seed. The design team will work with the land
owners to understand preferred replacement for vegetation that is removed.
1.4.2 Trees
The project site supports a variety of tree species, with coverage concentrated in riparian and
shoreline buffer zones. Dominant tree species include:
Native species: Bigleaf maple (Acer macrophyllum), Douglas-fir (Pseudotsuga menziesii),
Coast redwood (Sequoia sempervirens), and Western red cedar (Thuja plicata).
Non-native species: Black locust (Robinia pseudoacacia), Austrian pine (Pinus nigra), and
Weeping willow (Salix babylonica ‘Pendula’), English holly (Ilex aquifolium), and other
ornamental species (e.g., southern magnolia; Magnolia grandiflora).
Tree health is generally good in undisturbed areas, although some trees in impacted zones
exhibit signs of stress, such as canopy thinning and dieback.
The tree table from the Arborist Report provides detailed information on the species, health,
and retention recommendations for the project site (Tree Solutions 2025). Per the requirements
identified in RMC 4-8-120, tree retention planning follows the guidelines outlined in the
Arborist Report. The full dimensional tree inventory plan, prepared by an International Society
of Arboriculture-certified arborist, aligns with the project site plan specifications.
1.4.3 Critical Areas
Critical areas within the project site include:
Shoreline Jurisdiction: The shoreline of Lake Washington is designated as a Shoreline
of the State as defined by RMC 4-3-090B.1a.
Steep Slopes and Erosion Hazard Areas: Slopes along the shoreline range from flat (less
than 15% slope) to gently or moderately sloping (less than 40% slopes), with a majority
of the shoreline having 15 to 25% slopes. Renton (2025) identifies the shorelines
associated with the project as high erosion hazard areas, medium and high landslide
hazard areas, and sensitive slope areas.
Floodplain: May Creek to the north qualifies as a Federal Emergency Management
Agency (FEMA floodway), but the project area itself does not fall within floodplain or
floodway boundaries of May Creek. Lake Washington is a controlled system and not
considered part of the FEMA floodway.
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Riparian Buffer Areas: Vegetation along the shoreline is limited, primarily consisting of
ornamental plantings and scattered trees. However, small sections retain native riparian
cover, which contributes to ecological functions such as shading and providing
invertebrate prey for salmonids.
Overlap of the project with vegetation and tree assessments include riparian tree stands and
shoreline-associated species. Additional details on existing critical areas, proposed project
impacts, and no net loss of ecological functions for these areas are discussed in the Lake Study
(Confluence 2025b).
1.4.4 Soils and Hydrology
The project site consists of a mix of Holocene and glacial deposits, with loose to medium-dense
beach and fill materials overlying dense glacial till and recessional outwash (Shannon and
Wilson 2024). Subsurface explorations advanced five borings to depths ranging from 15.5 to 25.9
feet below ground surface (bgs). Groundwater was encountered between 3 and 15.9 feet bgs,
with seasonal fluctuations expected. The area is seismically active, with potential liquefaction in
recessional outwash deposits and slope stability concerns in certain locations. Proper
engineering measures will be necessary to ensure stability of slopes.
Hydrological features within the project site include the Lake Washington shoreline, a
deepwater habitat with an unconsolidated bottom that plays a key role in local hydrology,
groundwater influences, and stormwater drainage patterns. Hydrological features are shaped
by existing shoreline modifications such as bulkheads and riprap, which impact water flow and
retention.
Further details on soil conditions, boring locations, and drainage characteristics can be found in
the Draft Geotechnical Report (Shannon and Wilson 2024).
1.5 Construction Schedule and Duration
Construction of the individual ILS with grinder pumps (i.e., Phase 1) is projected to begin in
early 2026. The anticipated duration of construction is approximately 12 to 18 months, working
in phases to minimize the duration in any one portion of the project area. The time at each
property will vary but is estimated at approximately 10 to 15 working days, which will likely be
completed in several smaller intervals.
The detailed construction phasing will be determined by the contractor and their selected
means and methods. It is generally anticipated that construction will be completed in 3 zones,
associated with the 3 force main discharges. The electrical system and main line in the public
roadway will need to be tested and operational prior to completing lateral and side sewer
connections to the grinder pump stations.
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Once the replacement system is complete (i.e., Phase 1), the existing Kennydale lakeline system
will be decommissioned (i.e., Phase 2). Lakeline decommissioning is scheduled to occur in 2027
or 2028 once the upland replacement system is installed. Decommissioning work will occur
during approved in water work window for Lake Washington (July 16-December 31) and is
expected to take approximately 6 weeks to complete. The anticipated timing is between July 16
and September 30, but could shift depending on construction needs. Upland improvements for
the flush station and Washington Lift Station No. 2 are not dependent on in-water work
windows and can occur at any time during Phase 2 activities.
2.0 VEGETATION CONSERVATION BUFFER
According to RMC Table 4-3-090D.7.a, the project is within Reaches E and F of Lake
Washington with a shoreline designations of Urban Conservancy and Single Family Residential.
Both designations require 100 feet of vegetation conservation buffer.
2.1 Definition and Delineation (RMC 4-3-090)
The Vegetation Conservation Buffer is a designated area extending landward from the OHWM
of the shoreline. For Urban Conservancy and Shoreline Residential designations in Reaches E
and F, this buffer is 100 feet wide (Figure 2). The buffer aims to protect ecological functions by
limiting development and preserving vegetation within this zone.
The Vegetation Conservation Buffer serves several critical ecological functions, including:
Habitat Provision: It offers habitat for various terrestrial and aquatic species, supporting
biodiversity.
Water Quality Improvement: The buffer filters pollutants and sediments from surface
runoff before they enter the water body, enhancing water quality.
Erosion Control: Vegetation within the buffer stabilizes soil, reducing shoreline erosion
and maintaining bank integrity.
Functions of Soils and Hydrology: Soils within the buffer play a role in water
infiltration and groundwater recharge, while the hydrology is influenced by the buffer's
capacity to moderate surface runoff, reduce peak flows, and maintain base flows in
adjacent water bodies.
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Figure 2. Shoreline designations and vegetation conservation buffer.
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2.2 Replacement Requirements (RMC 4-4-130)
While specific ratios for vegetation replacement are not detailed in RMC 4-3-090, the code
emphasizes the preservation and enhancement of native vegetation within the buffer. Any
disturbed areas should be replanted with native species to maintain ecological functions,
especially for trees.
A minimum of 30% of all significant trees (trees >6 inches in diameter at breast height or
>8 inches for alders and cottonwoods) must be retained.
Tree replacement must achieve at least 30 tree credits per net acre, with credit values
assigned based on tree size. Tree sizes and their associated credits are shown in Figure 2.
Table 2. Tree sizes and associated credits per RMC 4-4-130
Tree Size Tree Credits
New small species tree 0.25
New medium species tree 1
New large species tree 2
Preserved tree 6-9 caliper inches 4
Preserved tree 10-12 caliper inches 5
Preserved tree 12-15 caliper inches 6
Preserved tree 16-118 caliper inches 7
Preserved tree 19-21 caliper inches 8
Preserved tree 22-24 caliper inches 9
Preserved tree 25-28 caliper inches 10
Significant trees, defined as those with a diameter of at least 6 inches at breast height (or 8
inches for alders and cottonwoods), must be preserved according to a priority system outlined
in RMC 4-4-130. The priority order ensures that the most ecologically valuable trees are retained
whenever possible. If lower-priority trees are retained instead of Priority One trees, applicants
must provide written justification demonstrating why higher-priority tree retention is not
feasible. Significant tress shall be retained in the following priority order:
Priority One Trees: Highest priority trees include landmark trees, trees forming a
continuous canopy, trees on slopes greater than 20%, trees adjacent to critical areas and
their buffers, trees over 60 feet tall or 18 inches in diameter, and trees that provide wind
protection for neighboring trees.
Priority Two Trees: Includes healthy tree groupings with preserved undergrowth,
significant native evergreen or deciduous trees, and other significant non-native trees.
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Priority Three Trees: Alders and cottonwoods are retained only when no higher-
priority trees can be preserved unless they are part of an approved enhancement project
in a critical area.
The project aims to retain at least 30% of significant trees as required by RMC 4-4-130, ensuring
ecological functions such as habitat provision, soil stabilization, and hydrological regulation are
maintained.
2.3 Potential Impacts
The Project Narrative and Code Consistency Analysis provides information on avoidance and
minimization measures that will be used by the proposed project (Confluence 2025). Avoidance
of impacts are provided through design and proposed construction methods. The primary
avoidance measure is converting the existing Kennydale lakeline system to an upland system to
avoid potential discharge of wastewater into Lake Washington. Best management practices
(BMPs), as detailed in the Project Narrative and Code Consistency Analysis, will be used during
construction to avoid or minimize potential environmental impacts. Tree-specific BMPs during
construction are provided in the Arborist Report (Tree Solutions 2025). Finally, site restoration
and cleanup at the end of construction will ensure that the project will result in primarily
temporary impacts.
The majority of project impacts are on private land. Although all vegetation will be replaced at a
ratio of 1:1, the portion that is within public lands will be tracked over time using a restoration
plan (Table 3; Figure 3). Project impacts are all within the shoreline zone and are temporary
during construction activities except for the installation of a new permanent generator at Lift
Station No.2. Overlap with other critical areas (e.g., steep slopes) and a no net loss analysis is
described in the Lake Study (Confluence 2025b).
Table 3. Proposed project impacts to vegetation and trees by phase
Project Phase and Type Potential Impact (Trenchless) Potential Impact (Open-Trench)
Phase 1: Upland Work
Vegetation (Kennydale Beach Park) 200 SF 600 SF
Trees Removed 4 trees 21 trees
Trees Impacted 13 trees 13 trees
Phase 2: In-Water Work
Vegetation (Lift Station No.2) 500 SF 500 SF
Trees N/A N/A
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Figure 3. Vegetation impacts on public lands.
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3.0 VEGETATION MANAGEMENT PLAN
The following section is a discussion of the proposed restoration plan components. This
document has been prepared to meet the applicable requirements of RMC 4-3-090 (SMP), RMC
4-3-050 (Critical Areas Regulations), and RMC 4-4-130 (Tree Retention and Land Clearing).
3.1 Preservation
A tree survey was conducted in February 2025 to identify significant trees within the project
area (Tree Solutions 2025). To ensure the protection of these trees during construction, a Tree
Protection Plan will be implemented, including the installation of physical barriers such as
fencing around root zones to prevent soil compaction and mechanical damage. Additionally,
monitoring protocols will be established to ensure compliance with preservation measures
throughout all construction activities, minimizing potential impacts to retained vegetation.
3.2 Enhancement and Restoration
Selective pruning will be implemented to remove dead or diseased branches, promoting overall
plant health and reducing the risk of disease spread on existing vegetation. If construction
activities impact vegetation, these plants will be replanted so that the project will result in only
temporary impacts to vegetation.
The project will focus on identifying invasive species, including Himalayan blackberry and
English ivy, within the area. A removal plan will be developed, utilizing methods such as
manual removal or targeted herbicide application, while adhering to BMPs to minimize
environmental impacts. Following removal, the cleared areas will be replanted with native
species suited to the site conditions, aiming to enhance habitat value and ecological function.
3.3 Establishment of New Vegetation
Establishment of new vegetation will include removing invasive plant species and replacing
removed plants at a 1:1 ratio within the project site (Table 4). The Project Drawings identify
zones for new plantings and a species palette available for planting in public lands (refer to
Sheets LS01 to LS12). Native species well-suited to local soil, hydrology, and climate conditions
will be prioritized to the extent practical in public areas to ensure long-term sustainability. The
exact location of replacement plantings will be determined in the field based on existing
conditions, actual impacts, and landowner preferences. A detailed as-built report, including a
drawing of restored areas will be prepared to document that the restoration requirements were
met. Note that the table below provides the values associated with open-trench construction
methods and an additional 15% to provide a conservative estimate of impacts.
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Table 4. Vegetation impact and restoration quantities (open-cut methods)
Location Impact Area (square feet) Restoration Area (square feet) Site Restoration Actions
Phase 1: Upland Work
Private Property 1,490 1,490 Restore existing lawn and landscape material.
Kennydale Beach Park 600 600 Restore native shrub and herbaceous understory, remove invasive species.
Phase 2: In-Water Work
Private Property N/A N/A N/A
Lift Station No. 2 500 0 Permanent impact to install a new generator and retaining wall to protect the generator.
3.4 Tree Retention and Planting
The project will comply with tree retention requirements by preserving at least 30% of existing
significant trees, as specified in RMC 4-4-130, and achieving a minimum of 30 tree credits per
net acre. Tree credits are based on the size and species of retained trees, with larger and native
species earning more credits. The Arborist Report provides detailed information on tree
inventory, health assessments, retention strategies, and credit calculations (Tree Solutions 2025).
Trees that are impacted will be replanted within the project site (Table 5). The Landscape Plan
provides conceptual information on planting areas but additional discussion of tree locations
will be needed during the design process to ensure compliance with tree density requirements
and enhancing the landscape. Note that the table below provides the values associated with
trenchless construction methods to reduce the overall number of trees removed.
Table 5. Tree removal and planting locations (trenchless construction)
Tree Number Tree Removed/Impacted Tree Replacement Credits Location by Parcel Common Name Tree Size (DSH; in)
272 3342700126 Southern magnolia 14.0 6
273 3342700126 Southern magnolia 10.4
275 3342700100 Black locust 21.5 N/A
308 3342700176 Hawthorn 13.5 N/A
The black locust located on parcel 3342700100 will not require tree replacement but the two
southern magnolia will result in a total of 6 replacement tree credits needed. The Tree Retention
and Credit Worksheets for the project are provided under a separate cover by parcel.
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3.5 Restoration Performance
The following sections outline the plan for assessing the performance of the proposed
restoration through specific standards. Separate performance standards are provided for
vegetation restoration and tree replacement.
3.5.1 Environmental Goals and Objectives
Per RMC 4-3-090D.2, the following goal and objectives of the on-site restoration are proposed to
compensate for the temporary loss of functions associated with the project. Note that only
public property will be monitored. Maintenance of private property vegetation will be at the
landowner’s discretion.
The goal of project is to restore the project site to existing conditions. This goal will be achieved
through the following objectives:
Objective 1: Create a vegetation community dominated by native species on public
property.
Objective 2: Replace all removed trees at the appropriate ratios per the tree worksheets.
Objective 3: Remove invasive species when they overlap with project activities and
maintain a low percent cover of invasive species in replanted areas.
3.5.2 Performance Standards
Per RMC 4-3-090F.1.i, the following measurable, specific performance standards and success
criteria are put forward to evaluate the success of the restoration plan implementation. Success
criteria track the progress of the performance standards (Table 6). The success criteria within the
restoration area will be monitored for a minimum of 3 years. Note that these performance
standards depend on a Year 0 report (separate from the as-built report) that provides an
accurate accounting of the actual plantings on-site compared to the proposed planting
schedules to be identified at a later design phase.
Table 6. Performance standards for the Kennydale lakeline project
Objective Performance Standard Success Criteria
Year 0 Year 1 Year 2 Year 3
1 PS1 – Percent Survival Vegetation NC 100% 80% 80%
2 PS2 – Percent Survival Trees NC 100% 100% 100%
1 PS3 – Native Species Percent Cover NC <30% <40% <50%
3 PS4 - Invasive Species Percent Cover NC <10% <10% <10%
PS = Performance Standard; NC = No Criteria
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3.5.2.1 Performance Standard 1 (PS1) – Percent Survival Vegetation
Planted vegetation will be monitored for survival every year during the 3-year monitoring
period. It is anticipated that natural recruitment will occur throughout the enhancement sites,
and these recruits will be included in the percent survival assessments when present.
Monitoring will occur during the growing season after deciduous plants have flowered or
leafed-out for easier identification.
3.5.2.2 Performance Standard 2 (PS2) – Percent Survival Trees
Planted trees will be monitored for survival every year during the 3-year monitoring period.
Trees are expected to have 100% survival and will be monitored accordingly. Monitoring will
occur during the growing season after deciduous trees have flowered or leafed-out for easier
identification.
3.5.2.3 Performance Standard 3 (PS3) – Native Species Percent Cover
Restoration areas will be monitored for percent cover by native species every year over the 3-
year monitoring period. Both planted and native volunteer species will be counted in the cover
measurements. As noted above under PS1, native species percent cover is expected to increase
as natural recruitment of plants increases in the restoration area. Monitoring will occur during
the growing season after deciduous plants have flowered or leafed-out for easier identification.
3.5.2.4 Performance Standard 4 (PS4) – Invasive Species Percent Cover
Restoration areas will be monitored for percent cover by invasive species every year over the 3-
year monitoring period. Monitoring will occur during the growing season after deciduous
plants have flowered or leafed-out for easier identification. Invasive species are defined as Class
A, B, and C weeds listed in the King County Noxious Weed List (King County 2025). Invasive
species of concern within the proposed enhancement sites include Himalayan blackberry and
English ivy, which are non-regulated Class C noxious weeds, and control is recommended but
not required.
4.0 MAINTENANCE, MONITORING, AND REPORTING
This section provides a plan for maintenance, monitoring, and reporting of the restoration areas
per RMC 4-3-050L. The effort for the 3-year maintenance and monitoring period will be
consistent throughout.
4.1 Maintenance Activities
Watering will be conducted as needed based on rainfall, ensuring plants receive at least
1.5 inches of water twice per month during the first year, with potential continued watering in
subsequent years using irrigation or water trucks. Weeding will occur regularly, with increased
frequency during the growing seasons, to prevent competition from invasive species such as
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Himalayan blackberry and English ivy. Mulching will be used to retain moisture and control
invasive species, with application limited to a maximum of 4 inches around plantings. Dead
plants will be removed only after scheduled monitoring to accurately assess planting success,
with replacement species selected to maintain buffer diversity.
4.2 Monitoring Plan
Data collected in Year 0 will provide the baseline for the success criteria in subsequent
monitoring years. Should the ecologist determine that any portion of the restored area needs to
be replanted during subsequent monitoring years, a survey will be conducted after the
replanting has been completed to establish a new baseline for subsequent monitoring surveys.
For example, if the Percent Survival Vegetation criterion is not met in Year 1, and the ecologist
determines that additional plants need to be planted, a survey will be conducted after the
addition of new plants. This survey will then provide the baseline for remaining monitoring
events.
The following sections describe the proposed methods for the monitoring plan. These methods
are subject to change if final site-design and as-built conditions warrant modification.
4.2.1 Transects and Photo Points
Using rebar sheathed in white polyvinyl chloride (PVC) pipe, transects will be established
within the restoration areas, named T1, T2, etc. The actual locations of the transects will be
determined in the field after plant installation. Coordinates for the end points of each transect
will be recorded using a global positioning system (GPS) and reported in the Year 0 Report.
Permanent photo points will be established at each end of each transect (i.e., T1A, T1B, etc.) to
document the site over time. At each of the photo points, a fixed-lens digital camera will be
used to take photographs, either a panoramic photo or 1 at every 90 degrees of the compass.
4.2.2 Percent Survival
Because of the relatively small quantity of plants to be installed in the on-site restored area, all
installed plants will be counted to calculate percent survival. The number of living plants for
that survey year will be divided by the number of living plants identified during the Year 0
monitoring event to determine the percent survival. Grasses (i.e., lawn) will not be assessed for
percent survival due to the difficulty in identifying individual plants over time. For areas
dominated by grass, percent cover will be the only sampling metric.
It is the expectation that all plants be monitored for survival for 3 years. Plants installed after
Year 0 will be monitored for survival for an additional 3 years. For example, if additional plants
are installed during Year 2 as a contingency measure, those plants would be monitored for
survival during Year 3 and Year 4 monitoring events unless percent survival success criteria are
met.
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4.2.3 Percent Cover
The line intercept method will be used to determine the percent cover for native and invasive
woody vegetation (i.e., trees and shrubs), and percent cover plots will be used to calculate the
percent cover for native and invasive emergent vegetation.
4.2.3.1 Line Intercept Method
The line intercept method will be used to record the percent cover of trees and shrubs along
each of the permanently marked transects (USDA and USDI 1999). After laying a tape measure
along a transect, the lengths of tape directly under the branches and foliage of a tree or shrub
will be recorded along with the species. The percent cover of each species will then be
calculated by dividing the sum of lengths intercepted for that species by the total length of the
transect.
4.2.3.2 Percent Cover Method
At one point along each transect, a permanent circular plot 15 feet in diameter will be marked
(T1P, T2P, etc.). The location of each circular plot along the transect will be determined during
the Year 0 monitoring by using a random number generator, and this plot location on each
transect will be consistent throughout the entire monitoring period. In each circular plot, the
percent cover of herbaceous and woody species, including bare ground, will be estimated, and
recorded.
4.3 Reporting
For each monitoring event, the ecologist will prepare a report. One copy of each report will be
provided to the City, who will distribute it to the appropriate recipients within Renton
Development Services Department. The following will be included in each report:
Data tables
Species lists
Date of survey
A narrative description of methods and contingency measures taken
Identification of planted and naturally recruited trees and shrubs
Interpretation of results
Color photos from each of the permanent photo points
The Year 0 report and as-built drawing will be completed within 30 days after planting is
completed. In addition to the general reporting requirements stated above, the following will be
included in the post-construction impact assessment:
Actual planting density (container size)
Coordinates of actual location of transects and photo points
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Location of transects and photo points depicted on a figure
Description of changes from original design
Planting schedule
The first annual report will be due within 1 year after the City and Renton Development
Services Department acceptance of the Year 0 report. All annual reports will be submitted by
November 30 of the monitoring year. Monitoring reports will be submitted for Years 1, 2, and 3
documenting success or failure of meeting the performance criteria listed in Table 4 reference
for criteria.
5.0 CONTINGENCY PLAN
This section provides a contingency plan that identifies corrective measures to be taken if
monitoring indicates that the performance standards are not met per RMC 4-3-090F.1.i. These
include measures for plant mortality, percent cover, and invasive species.
5.1 Plant Mortality
High mortality could result from improper installation, diseased or infested plants, inadequate
watering, or extreme weather. If more than 25% of new plantings die in a single year, the cause
of the high losses will be investigated and corrected before dead plants are replaced. Dead plant
material may only be removed after that year’s scheduled monitoring. If Renton would prefer to
use this material to aid the ecosystem, that should be noted within the monitoring report.
The following is an example of a contingency measure that would be taken related to plant
mortality. During the Year 2 monitoring, the Percent Survival Vegetation (PS1) criterion is not
met (i.e., less than 80% of the plants installed have survived). The corrective action will be
installation of new plants to bring the planting schedule back into original specifications. Plant
survival monitoring would continue for 3 additional years (i.e., Years 3, 4, and 5).
5.2 Native Species Percent Cover
If the percent cover success criterium is not met, the cause will be investigated and corrected.
Correction measures may include increased watering, soil amendments, or additional plantings.
The cause may also be dominance by invasive species.
5.3 Invasive Species Percent Cover
Dominance by invasive species could result from disturbance of the soil, a high mortality rate of
the native planted vegetation, or colonization by windborne seeds. If more than 10% of the area
is covered by invasive species, the cause of infestation will be investigated, and corrective
actions will be taken before weeds are removed. Contingency measures could include
increasing the frequency of weeding or herbicide use (if applicable) during the monitoring
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period until native vegetation can grow and dominate the area or increasing the density of
native vegetation with additional plantings.
5.4 Plan Revisions
The Vegetation Management Plan will be updated periodically based on monitoring results and
observed environmental changes. Revisions may be made in response to shifts in vegetation
performance standards, the presence of invasive species, or other ecological factors. The update
process includes reviewing data, assessing performance standards, additional maintenance of
the plantings, and extended periods of monitoring.
6.0 REFERENCES
Confluence (Confluence Environmental Company). 2025. Kennydale lakeline sewer system
replacement project: Lake study. Prepared for Carollo Engineers, Seattle, Washington.
Prepared by Confluence Environmental Company, Seattle, Washington.
Confluence and Tree Solutions (Tree Solutions Inc.). 2025. Kennydale lakeline sewer system
replacement project: Vegetation management plan. Prepared for Carollo Engineers, Seattle,
Washington. Prepared by Confluence Environmental Company and Tree Solutions Inc.,
Seattle, Washington.
Renton (City of Renton). 2025. COR Maps | Online Data.
https://maps.rentonwa.gov/Html5viewer/Index.html?viewer=cormaps.
Shannon & Wilson Inc. 2024. Geotechnical engineering report: Kennydale lakeline sewer
improvements, Renton, Washington. Prepared for Carollo Engineers, Seattle, Washington.
Prepared by Shannon & Wilson Inc., Seattle, Washington.
Tree Solutions. 2025. Arborist Report. Prepared for Carollo, Seattle, Washington, by Tree
Solutions, Seattle, Washington.
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