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Stormwater Technical
Information Report
SWARR Station
Security Maintenance Project
Project Site Location:
2100 Benson Drive South,
Renton, WA 98055
April 14th, 2026
Stormwater Technical Information Report
SWARR Station Security Maintenance Project
Puget Sound Energy
Prepared for:
Puget Sound Energy
35131 SE Center Street,
Snoqualmie, Washington 98065
Attention: Jason Henry, PE
Prepared by:
HDR Engineering Inc.
555 110th Avenue NE, Suite 1200,
Bellevue, WA 98004-5124
(425) 503-5815
____________________________
Nathaniel Cockbain, EIT
Site Civil EIT
____________________________
Jeffrey Becker, PE
Civil Section Manager
04/19/202604/14/2026
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Contents
1 Project Overview ..................................................................................................................................... 4
1.1 Introduction and Purpose ............................................................................................................. 4
1.2 Project Overview/Description ....................................................................................................... 4
1.3 Existing Site Conditions ................................................................................................................. 5
1.3.1 Existing Site Topography ................................................................................................ 5
1.3.2 Existing Site Drainage ..................................................................................................... 6
1.3.3 Existing Site Vegetation .................................................................................................. 7
1.3.3 Existing Site Soils and Groundwater ............................................................................... 7
1.4 Proposed Site Conditions .............................................................................................................. 8
1.4.1 Site Earthwork ................................................................................................................ 9
1.4.2 Site Drainage .................................................................................................................. 9
1.4.3 Vegetation Management ............................................................................................. 10
2 Conditions and Requirements Summary .............................................................................................. 13
2.1 Drainage Review Classification for Project ................................................................................. 13
2.2 CORE Requirements and Project Applicability ............................................................................ 13
2.2.1 CR #1: Discharge at Natural Location ........................................................................... 13
2.2.2 CR #2: Offsite Analysis .................................................................................................. 13
2.2.3 CR #3: Flow Control Facilities ....................................................................................... 14
2.2.4 CR #4: Conveyance Systems ......................................................................................... 14
2.2.5 CR #5: Construction Stormwater Pollution Prevention ................................................ 14
2.2.6 CR #6: Maintenance and Operations ........................................................................... 14
2.2.7 CR #7: Financial Guarantees and Liability .................................................................... 15
2.2.8 CR #8: Water Quality Facilities ..................................................................................... 15
2.2.9 CR #9: On-site BMPs ..................................................................................................... 15
2.3 Special Requirements and Project Applicability ......................................................................... 15
2.3.1 SR #1: Other Adopted Area-Specific Requirements ..................................................... 15
2.3.2 SR #2: Flood Hazard Area Delineation .......................................................................... 15
2.3.3 SR #3: Flood Protection Facilities ................................................................................. 15
2.3.4 SR #4: Source Control ................................................................................................... 15
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2.3.5 SR #5: Oil Control .......................................................................................................... 15
2.3.6 SR #6: Aquifer Protection Areas ................................................................................... 16
3 Offsite Analysis ...................................................................................................................................... 16
4 Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design ........... 16
5 Conveyance System Analysis and Design ............................................................................................. 16
6 Special Reports and Studies ................................................................................................................. 17
7 Other Permits ....................................................................................................................................... 17
8 CSWPP Analysis and Design ................................................................................................................. 17
9 Bond Quantities, Facility Summaries, and Declaration of Covenant .................................................... 18
10 Operations and Maintenance Manual .................................................................................................. 18
11 References ............................................................................................................................................ 19
Figures
Figure 1. Site Location ................................................................................................................. 11
Figure 2. Overall Site Plan ............................................................................................................ 12
Appendices
Appendix A. TIR Worksheet ..................................................................................................................
Appendix B. Project Drainage Review Classification ............................................................................
Appendix C. Geotechnical Design Memorandum .................................................................................
Appendix D. Geologically Hazardous Areas Report ..............................................................................
Appendix E. Construction Stormwater Pollution Prevention Plan .......................................................
Appendix F. Site Improvement Drawings (submitted separately) .......................................................
Appendix G. Arborist Report .................................................................................................................
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Abbreviations
ac acre(s)
bgs below ground surface
BMP best management practice
CED Community and Economic Development Department
Cf cubic foot/feet
City City of Renton
COR City of Renton
CR Core Requirement
CSWPPP Construction Stormwater Pollution Prevention Plan
ESC erosion and sediment control
ft2 square foot/feet
KC King County
LID low-impact development
NPGIS non-pollution-generating impervious surface
NRCS National Resources Conservation Service
PGIS pollution-generating impervious surface
PGPS pollution-generating pervious surface
PSE Puget Sound Energy
RMC Renton Municipal Code
RSWDM Renton Surface Water Design Manual
SP Standard Plan
SR Special Requirement
SWPPS stormwater pollution prevention and spill control
TDR Targeted Drainage Review
TIR Technical Information Report
USDA United States Department of Agriculture
WNG Washington Natural Gas
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1 Project Overview
1.1 Introduction and Purpose
The purpose of this Stormwater Technical Information Report (TIR) is to describe the scope of
work for proposed improvements at the Puget Sound Energy (PSE), SWARR Station Security
Maintenance Project (Project) and to summarize the stormwater review level thresholds as found
in the 2022 City of Renton (COR) Surface Water Design Manual (RSWDM, 2022). This report
accompanies the civil engineering plans and documents for the PSE SWARR Security Maintenance
Project (Project).
Based on the Project criteria and Figure 1.1.2.A of the 2022 RSWDM, the Project is subject to a
Targeted Drainage Review (TDR), and specifically TDR Review Category #2 as defined by section
1.1.2.2 of the 2022 RSWDM. See Appendix A: TIR Worksheet, for a detailed summary of the
Project and its proposed stormwater controls. As required by Section 2.3 of the 2022 RSWDM,
this Stormwater TIR has been prepared in accordance with the COR Stormwater TIR format. As
such, the purpose of this Stormwater TIR is to demonstrate that the Project complies with the
selected core and special requirements corresponding to the TDR Review Category #2 of the 2022
RSWDM.
1.2 Project Overview/Description
PSE is proposing to improve reliability, security and safety at the SWARR Station by upgrading
perimeter security fencing and security system equipment. The Project will be completed on PSE
owned Parcel No. 2023059071, located at 2100 Benson Drive South in Renton, King County,
Washington. The property is situated within Section 20 of Township 23 North and Range 05 East
of the Willamette Meridian (WM). See Figure 1: Site Location for Project location. The Project is
bounded by Benson Drive South (SR-515) to the west, South Puget Drive to the east, single family
residences to the South and vacant land to the north. Site access is via a paved driveway from
Benson Drive South (SR-515) to the southwest. The Project will be completed within the southern
developed 8 acres of the approximate 16.71-acre parcel. The current zoning classification of the
Project site is residential development zone R-8. Land use in the area includes residential
development zone R-8 to the west (across Benson Drive South), a combination of zoning R-14,
RM-F and CA to the east (across South Puget Drive), a combination of zoning R-14 and R-8 to the
north (across intersection of South Puget Drive and Benson Drive South) and a combination of
zoning R-8 and RM-F to the south. The Project will not affect current land uses on nearby or
adjacent properties.
The developed area is currently surrounded by an existing chain link perimeter fence with barbed
wire. The existing perimeter security fence is antiquated and damaged in places, and several
security breaches have occurred in recent years. To protect the property and associated critical
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infrastructure against unauthorized access, theft, vandalism and other threats, PSE plans to
replace the perimeter security fencing and security system equipment.
1.3 Existing Site Conditions
The property was originally developed by Washington Natural Gas (WNG) in 1965 as a “peak
shaving” facility for periods of high natural gas demand during cold weather. The facility is now
owned and operated by PSE; successor to WNG. The Project is within the COR Flow Control
Duration Standard (matching forested conditions) and within the Black River drainage basin. The
project does not contain or is not adjacent to an aquifer protection area.
The Project site is situated in the southern portion of a 16.71-acre triangular parcel bordered by
Benson Drive South (SR-515) and South Puget Drive. In general, the existing facilities located near
the center of the Project site include a one-story metal sided building, natural gas piping and
aboveground storage tanks situated on a gravel surface. Existing underground storage tanks are
located on the north side of the project site where the ground surface is vegetated with grass. The
south side of the project site contains the main driveway into the site facilities and parking area,
east to west trending underground natural gas pipelines (owned by Williams and PSE), forested
habitat with little understory vegetation and maintained grass areas. The northern portion of the
parcel (outside of the fenced improved area) is undeveloped and forested with shrub understory.
See Figure 2: Overall Site Plan for the existing and proposed developed conditions. Existing site
conditions as reported in a topographic survey completed for the Project, titled Topographic
Survey SWARR Station WO#142003204 Puget Sound Energy Renton, WA, prepared by David Evans
and Associates Inc., dated December 22, 2025 (seal date January 7th, 2026).
1.3.1 Existing Site Topography
The Project site is situated in the southern portion of the parcel which is located in a northwest-
southeast trending drainage of Rolling Hills Creek. The site is situated on a relatively flat to very
gently sloping (slope gradients of 0 to 15 percent) ground surface. The developed portion of the
site is bounded by a gently sloping (slope gradients between 5 and 15 percent) forested area to
the north, by steep slopes (slope gradients ranging between 40 to 65 percent) up to South Puget
Drive and businesses to the east, by gentle slopes (slope gradients between 5 and 20 percent)
uphill to single-family residential developments to the south, and to the west by steep slopes
(slope gradients raging between 40 to 70 percent) up to Benson Drive South (SR-515). Slopes
around the site are vegetated with evergreen and deciduous trees and shrubs, blackberries, ivy,
grass and other understory vegetation.
When the station was built in the 1960’s, the site was graded to provide a relatively flat to gently
sloping ground surface between approximately elevation 160 above mean sea level (MSL) to
approximately 150 feet MSL from south to north. The project area is approximately 10 to 30 feet
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lower in elevation than Benson Drive South on the west side of the site and between
approximately 50 to 90 feet lower in elevation than South Puget Drive on the east.
1.3.2 Existing Site Drainage
Per the COR Utility Geographic Information System (GIS) data (COR, 2025), there are multiple
stormwater discharge points that direct water towards the Project Site. Surface water along
Benson Drive South (SR-515) collects within curbside gutters and enters three catch basins located
on the east side of Benson Drive South (SR-515) adjacent to the west side of the Project parcel.
Stormwater along this portion of Benson Drive South (SR-515) as well as stormwater from the
north side of Benson Drive South (SR-515), South 21st Street and South 19th Street enters the
stormwater drain system and discharges onto PSE’s property at a point outside of the northwest
corner of the Project site. Evidence of water sheet flow (fine sediments, organic matter
accumulation) from the discharge point that flows northeast through the northwest corner of the
existing fence line towards Rolling Hills Creek has been reported. This sheet flow either infiltrates
or eventually flows into Rolling Hills Creek.
Surface water along South Puget Drive adjacent to the Project site is collected within curbside
gutters and enters two catch basins located on the east and west sides of South Puget Drive which
discharge stormwater onto the slopes on the east side of the Project site. Evidence (GeoEngineers,
2026b.) of plastic piping installed on the site slopes to capture the discharged water and transport
it to the base of the slopes has been reported. The water then flows into the half-rounds that have
been installed on the east side of the site access road to convey the water along the toe of the
slope to the northeast corner of the site where the water flows into an existing catch basin and
then discharges via a 12-inch diameter pipe to Rolling Hills Creek on the north side of the Project
site.
According to COR, Rolling Hills Creek is mapped as an open channel on the north and south sides
of the Project site. Rolling Hills Creek flows north through the Project site and is located within a
culvert under the developed portion of the property. The creek flows into the culvert inlet at the
south end of the Project site and discharges to an open stream channel on the north end of the
Project site. The creek is located outside of the proposed work areas and will not be disturbed by
construction. All land disturbance will occur within or immediately adjacent to the Project
facilities, which are located in upland areas.
Portions of the Project site are mapped by COR as containing GeoHazard areas, including Erosion
Hazard, Landslide Hazard and Coal Mine Hazard Areas. These features have previously been
evaluated by PSE and additional analysis has been conducted and reported by GeoEngineers Inc.,
titled Geologically Hazardous Areas Report, SWARR Station – Security Maintenance Project, dated
February 6th, 2026 (GeoEngineers, 2026b) and is included for reference in Appendix D.
Geologically Hazardous Areas Report of this report.
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1.3.3 Existing Site Vegetation
Project site conditions are composed of a primarily forested landscape surrounding the existing
perimeter security fence. Himalayan blackberry and English ivy, both considered noxious weeds
within King County, were pervasive throughout the understory of the Project site. Existing
underground storage tank facilities are located on the north side of the project site where the
ground surface is vegetated with grass. The south side of the project site contains the main
driveway into the site facilities and parking area, east to west trending underground natural gas
pipelines, forested habitat with little understory vegetation and maintained grass areas. The
northern portion of the parcel (outside of the fenced facility) is undeveloped and forested with
shrub understory.
An Arborist Report titled “Arborist Report SWARR Station (Fence Replacement Project)” dated
October 2025 prepared by Davey Resource Group (DRG, 2025) inventories all the significant trees
potentially impacted by construction on the Project site. The Arborist Report is included for
reference in Appendix G. Arborist Report of this report. This inventory included significant trees
either A) 15-feet from the existing fence or B) in areas where trees would be impacted by new
fence alignment as it deviates from the existing. Each tree was visually assessed, and the required
tree data was collected using a GIS database. Refer to the separately bound arborist report for
additional information regarding existing trees on the Project site.
1.3.4 Existing Site Soils and Groundwater
A Geotechnical Memorandum (GeoEngineers, 2025), see Appendix C. Geotechnical Design
Memorandum, and a Geologically Hazardous Areas Report (GeoEngineers, 2026b.), see Appendix
D. Geologically Hazardous Areas Report, for this Project have been completed by GeoEngineers,
Inc. GeoEngineers completed nine hand auger borings at the Project site to depths ranging from
0.5 feet to 2.5 feet below the ground surface (bgs) on September 27, 2024, to evaluate soils and
groundwater conditions along the proposed Project replacement fence line alignment.
Groundwater was not observed in the hand auger borings. Subsurface conditions consist of fill to
the depth explored. The fill consists of poorly graded sand with silt and gravel, silty sand and
organic matter and extends to a depth of 2 feet bgs.
GeoEngineers (GeoEngineers, 2011) installed 10 monitoring wells at the site between 2003 and
2007 as part of a previous environmental study at the site. Groundwater levels were measured in
the wells during monitoring events in September 2010 and March 2011. Depths to groundwater
measured in the vicinity of the storage and pumping facilities ranged from approximately 2.7 to
11.4 feet bgs in September 2010 and March 2011. Depths to groundwater measured on the south
side of the site entrance driveway ranged from approximately 7.8 to 17.8 feet bgs. Depths to
groundwater measured in the northeast corner of the developed site ranged from approximately
14.3 to 22.4 feet bgs.
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Based on soil information available from the United States Department of Agriculture (USDA)
National Resources Conservation Service (NRCS), the Project site is underlain by two distinct
surficial soil units. The majority of the Project site is underlain by a soil unit referred to as the
Alderwood gravelly sandy loam, 15 to 30 percent slopes. The soil is described as having a parent
material of glacial drift and/or glacial outwash and being a gravelly sandy loam from 0 to 7 inches
and very gravelly sandy loam between 7 to 59 inches. This soil unit is classified by the NRCS as
having a severe erosion hazard, being moderately well-drained, and having a very low to
moderately low infiltration rate of between 0.00 and 0.06 inches per hour. The depth to the water
table is reported to be 18 to 37 inches.
The minor soil unit located along the western boundary of the Project site is referred to as the
Beausite gravelly sandy loam characterized by 6 to 15 percent slopes. The soil is described as
having a parent material of till over weathered soils from sandstone, being a gravelly, ashy sandy
loam from 0 to 38 inches, and as bedrock between 38 to 42 inches. This soil unit is classified by
the NRCS as having a moderate erosion hazard, being well-drained and having a moderately high
infiltration rate of between 0.57 and 1.98 inches per hour. The depth to the water table is reported
to be more than 80 inches.
1.4 Proposed Site Conditions
The Project proposes to replace the existing 6 to 7-foot-tall chain link perimeter security fence
around the SWARR Station with new 8-to 12-foot-tall metal mesh fence including security cameras
and intrusion detection security upgrades. The Project also plans to replace the aging vehicle and
pedestrian gates at the main entrance to Benson Drive South (SR-515) in the southwest corner of
the site and at the entrance to South Puget Drive in the northeast corner of the site. The Project
is proposing the addition of four (4) 4-to 5-foot-wide pedestrian gates, two (2) 20-foot-wide
removable fence panels and one (1) 20-foot-wide double swing gate around the replaced fence
perimeter to improve operation and maintenance access. Security maintenance including
cameras and intrusion detection systems will be installed in-line with the replacement fence
alignment, on specialized fence posts. The replacement fence alignment will generally follow the
existing fence alignment, with most segments installed interior to the existing fence alignment.
The replacement fence will not expand the developed station footprint. See Figure 2: Overall Site
Plan for the existing and proposed developed conditions.
During fence construction, the existing 6 to 7-foot-tall chain link perimeter security fence around
the SWARR Station shall remain in place to provide site security during construction of the new
fence, where feasible. Following installation of the new security fence, portions of the existing 6
to 7-foot-tall chain link perimeter security fence that are within 10-feet of the new fence will be
removed, by cutting existing fence posts at ground surface and abandoning existing footings in
place to minimize ground disturbance. Portions of the existing fence that are located greater than
10-feet away from the new fence shall remain in-place.
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1.4.1 Site Earthwork
Site work for the SWARR Station security maintenance will consist of excavation by means of
auguring, hydrovactoring and/or air spading for fence post and camera post installation. The
proposed security maintenance requires the installation of a power and communications system
with conduits hung on the proposed fence to reduce ground disturbance. Conduit trenching will
be required from the existing maintenance building to the replacement fence alignment and
between all gate and removable fence sections. Six (6) existing gas sensors will be relocated
interior to the replacement perimeter security fence, which will require minor conduit trenching.
Two (2) existing gate controllers and associated concrete pads will be removed and replaced in
the southwest corner of the site at the entrance to Benson Drive South (SR-515). All earthwork
activities will occur within the existing station security fence.
Land disturbing activity will include approximately 1,250 square feet of grading to flatten existing
ground in proximity to a proposed 20-foot-wide double swing gate, approximately 1,000 square
feet of vegetation clearing, approximately 940 square feet for conduit trenching and gate
controller concrete pads and approximately 760 square feet for fence post excavation. Total land
disturbing activity is estimated at approximately 3,950 square feet. Site restoration will be
completed as soon as practical after construction activities are completed. Site restoration will
include backfilling excavations, regrading workspaces to pre-construction conditions and placing
crushed rock, gravel, asphalt or grass seed and mulch in disturbed areas to match pre-construction
site conditions. Areas where existing trees and vegetation have been cut will be restored with
mulch.
The proposed land disturbing activity will generate approximately 210 cubic yards of cut, 70 cubic
yards of fill. The remaining net 140 cubic yards will be hauled off-site and disposed of at a PSE
approved landfill and/or disposal facility. Excavations will range from approximately 24-inches to
76-inches deep for fence post installation and conduit trenching. No buildings or new impervious
surface is proposed for the project.
1.4.2 Site Drainage
The replacement fence alignment is proposed to cross over an existing, private roadside ditch
consisting of a half-round 24-inch diameter corrugated plastic pipe. The replacement fence
alignment will cross over the existing ditch to avoid potential separation issues between the new
fence and existing public water and sewer utilities. The ditch crossing will create an open space
where unauthorized personnel could crawl underneath the fence. To mitigate the potential
security risk, the gap beneath the replacement fence is proposed to be filled-in with a 12-inch
diameter stick of storm drainpipe, installed within the existing roadside ditch. The stick of pipe
will be anchored in-place, and gravel backfill will be provided on top and around the pipe to match
existing adjacent grade. Both ends of the 12-inch diameter pipe will be beveled, and a debris
barrier will be secured to the beveled end. 12-inch diameter pipe is selected to prohibit
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unauthorized personnel from passing through, and it is the same size pipe as used further
downstream in the existing stormwater drainage system that has not been observed to have
capacity issues. No other drainage improvements are proposed for this Project.
See Section 2 for additional information and a description of Project conformance with core and
special requirements.
1.4.3 Vegetation Management
Vegetation management will be required, including cutting and removing fifty-nine (59) trees. This
includes cutting and removing forty-two (42) dead or dying poor-condition trees recommended
for removal for safety concerns as identified in the Arborist Report (DRG, 2025), cutting and
removing seventeen (17) trees in conflict with the replacement fence alignment, and clearing
approximately 1,000 square feet of existing blackberries/weeds in conflict with the replacement
fence alignment. The tree species identified for removal include Douglas fir (Pseudotsuga
menziesii), bigleaf maple (Acer macrophyllum), shore pine (Pinus contorta), wild cherry (Prunus
avium), black cottonwood (Populus trichocarpa), western red cedar (Thuja plicata), willow (Salix
spp.), red alder (Alnus rubra), Scots pine (Pinus sylvestris), bitter cherry (Prunus emarginata),
western hemlock (Tsuga heterophylla), Oregon ash (Fraxinus latifolia), apple (Malys spp.), and
grand fir (Abies grandis).
Vegetation management will occur along the north, east and west sides of the new perimeter
security fence to allow for installation of the new fence. Vegetation management along the south
side of the site will be minimal as new fence installation will be limited to within the existing
driveways gravel shoulder. Tree removals will minimize ground disturbance by sawcutting the
existing tree at the ground surface and abandoning the existing stumps and roots in place. To
ensure proper security clearance from the replacement fence, pruning activities shall include
pruning all tree limbs that are withing 10-feet horizontal of the replacement fence, for 5-feet
minimum above the replacement fence. No more than 10% of the overall canopies will be
removed as a result of pruning. English ivy (Hedera helix) will be removed from numerous trees
by girdling the ivy stems at the base to improve tree health. A minor extent of native understory
plants near retained trees may need to be trimmed and/or temporarily covered with construction
mats during construction activities.
Comprehensive tree protection measures will be implemented including use of air spade and/or
hydrovactoring systems for excavation within Critical Root Zones, application of 3-inch layer of
coarse arborist wood chips and construction mats to reduce soil compaction, and active
supervision by an ISA Certified Arborist as needed during construction activities near retained
trees.
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Figure 1. Site Location
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SWARR STATION
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SOUTH (SHEETS C002, C005, C009)NORTH (SHEETS C003, C006, C010)
SWARR STATION
BENSON DR S (SR-515)
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OVERALL SITE PLAN IN COMPLIANCE WITH CITY OF RENTON STANDARDS
Call before you dig.
PUGET SOUND ENERGY
SWARR STATION SECURITY MAINTENANCE PROJECT
2100 BENSON DRIVE S, RENTON, WA 98055 SW
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WO NUMBER: 142003204 (LEADING), 10860860 (RETIREMENT)
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OVERALL SITE PLAN
Figure 2. Overall Site Plan
04/19/202604/14/2026
PSE SWARR STATION SECURITY MAINTENANCE PROJECT | Stormwater Technical Information Report
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2 Conditions and Requirements Summary
2.1 Drainage Review Classification for Project
The Project is subject to the City of Renton’s Municipal Code 4-6-030, Drainage and Water Quality
(Surface Water) Standards. The City of Renton 2022 Surface Water Design Manual (RSWDM, 2022)
is applicable to Renton projects with permit application after the effective date of the updated
manual.
This Project is required to provide a Targeted Drainage Review (TDR), specifically TDR Review
Category #2 because it meets the following criteria in Section 1.1.1, Figure 1.1.2.A (see Appendix
B. Project Drainage Review Classification) and Section 1.1.2.2 of the 2022 RSWDM.
• Projects containing or adjacent to a flood, erosion, or steep slope hazard area.
• Projects that construct or modify a drainage pipe/ditch that is 12” or larger or receive
runoff from a 12” or larger drainage pipe/ditch.
Projects that trigger a TDR Category #2 are required to demonstrate that the project complies
with Core Requirements (CR) #1, #2, #4, #5, #6, #7 and Special Requirements (SR) #4 and #6.
Sections 2.2 and 2.3 below provide a summary of how the project will comply with these core and
special requirements respectively. Where a particular requirement is not specifically applicable to
the Project, the basis for that determination is provided.
2.2 CORE Requirements and Project Applicability
The following 2022 RSWDM Core Requirements (CR) were evaluated for applicability under the
Project’s Targeted Drainage Review (TDR) Category #2.
2.2.1 CR #1: Discharge at Natural Location
The Project will maintain existing drainage patterns on site with stormwater generally flowing
north. Stormwater generally infiltrates onsite and any runoff sheet flows to the private roadside
ditch consisting of a half-round 24-inch diameter corrugated plastic pipe, where the water flows
into an existing catch basin and then discharges via a 12-inch diameter pipe to Rolling Hills Creek
on the north side of the Project site. The Project will not alter existing drainage patterns, and
runoff from the site will continue to drain as it currently does today, with either sheet flow or
infiltration into the surrounding soils, until it is conveyed to the existing 12-inch diameter pipe to
Rolling Hills Creek on the north side of the Project site.
2.2.2 CR #2: Offsite Analysis
Exempt per the Project Pre-Application meeting held with City of Renton (COR) Community and
Economic Development Department (CED) held on November 21st, 2024, titled PRE 24-000335
and follow-up discussions with CED held thereafter (COR, 2024).
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2.2.3 CR #3: Flow Control Facilities
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.2.4 CR #4: Conveyance Systems
The Project will not alter existing pervious/impervious surface areas, storm water runoff flow
rates, volumes or patterns and will not alter the existing storm drain system. The Project requires
the new fence crossing an existing private roadside ditch, consisting of a half-round 24-inch
diameter corrugated plastic pipe that will create a gap below the fence introducing a security
concern. To resolve the security concern, a stick of 12” diameter pipe will be placed directly under
the fence to fill-in the gap. 12” diameter pipe is used to match the diameter of other downstream
culverts and storm drain pipe for which there are no known performance issues. Because there
are no known performance issues, no calculations are required. The Project will protect and
maintain all existing conveyance piping or systems currently installed on-site during construction.
2.2.5 CR #5: Construction Stormwater Pollution Prevention
Since the Project will conduct construction activities that will clear, grade, or otherwise disturb
the site, erosion and sediment control to prevent, to the maximum extent practical, the transport
of sediment from the Project site to downstream drainage facilities, water resources, and adjacent
properties must be provided. The Project will conduct construction activities onsite and must
provide stormwater pollution prevention and spill controls to prevent, reduce, or eliminate the
discharge of pollutants to onsite or adjacent stormwater systems or watercourses. To prevent
sediment transport and pollutant discharges as well as other impacts related to land-disturbing
and construction activities, Erosion and Sediment Control (ESC) measures and Stormwater
Pollution Prevention and Spill Control (SWPPS) measures that are appropriate to the Project site
must be applied through a comprehensive Construction Stormwater Pollution Prevention
(CSWPP) plan as described in Sections 1.2.5.1 and 1.2.5.3 and shall perform as described in Section
1.2.5.2 of the 2022 RSWDM.
Targeted ESC and SWPPS Best Management Practices (BMPs) applicable to the Project are
included in the Project Construction Stormwater Pollution Prevention Plan (CSWPP) prepared by
GeoEngineers (GeoEngineers, 2026a). The CSWPP is included as Appendix E. Construction
Stormwater Pollution Prevention Plan.
2.2.6 CR #6: Maintenance and Operations
Exempt per the Project Pre-Application meeting held with City of Renton (COR) Community and
Economic Development Department (CED) held on November 21st, 2024, titled PRE 24-000335
and follow-up discussions with CED held thereafter (COR, 2024).
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2.2.7 CR #7: Financial Guarantees and Liability
The financial guarantee requirement of the City under Renton Municipal Code (RMC) Section 4-6-
030 for all newly constructed or modified drainage systems proposed by a project are not
expected to directly apply since the project owner is a utility company and minimal drainage
system modification is proposed. PSE and the City will need to review how this requirement will
be handled for this Project, either as a Standard Adjustment from Core Requirement (CR) #7, or
as implemented through a Memorandum of Understanding (MOU) or similar agreement between
PSE and City.
2.2.8 CR #8: Water Quality Facilities
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.2.9 CR #9: On-Site BMPs
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.3 Special Requirements and Project Applicability
The following 2022 RSWDM Special Requirements (SR) were evaluated for applicability under the
Project’s Targeted Drainage Review (TDR) Category #2.
2.3.1 SR #1: Other Adopted Area-Specific Requirements
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.3.2 SR #2: Flood Hazard Area Delineation
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.3.3 SR #3: Flood Protection Facilities
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
2.3.4 SR #4: Source Control
Not applicable. The purpose of the Project is security maintenance improvements that do not
change the site use and operations, pervious and impervious surface areas and does not require
a commercial building or a commercial site development permit. No improvements are proposed
that will require source controls.
2.3.5 SR #5: Oil Control
Not applicable per 2022 RSWDM TDR Review Category #2 in Figure 1.1.2.A and Table 1.1.2.A.
PSE SWARR STATION SECURITY MAINTENANCE PROJECT | Stormwater Technical Information Report
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2.3.6 SR #6: Aquifer Protection Areas
Not applicable. The Project site is not located within a Wellhead Protection Area mapped by the
City of Renton (COR) Utility Geographic Information System (GIS) data (COR, 2025). As a result,
Special Requirement (SR) #6: Aquifer Protection Areas, does not apply.
3 Offsite Analysis
Exempt per the Project Pre-Application meeting held with City of Renton (COR) Community and
Economic Development Department (CED) held on November 21st, 2024, titled PRE 24-000335
and follow-up discussions with CED held thereafter (COR, 2024).
4 Flow Control, Low Impact Development (LID)
and Water Quality Facility Analysis and Design
Not applicable per section 2.3.2 and specifically Table 2.3.2.A, Minimum Engineering Plan
Elements for Projects in Targeted Drainage Review, of the 2022 RSWDM, the Project is not
required to address Section 4: Flow Control, Low Impact Development (LID) and Water Quality
Facility Analysis and Design under the TDR Category #2 requirements.
5 Conveyance System and Design
The replacement fence alignment is proposed to cross over an existing, private roadside ditch
consisting of a half-round 24-inch diameter corrugated plastic pipe. The ditch crossing will create
a security concern with an open space where unauthorized personnel could crawl underneath the
fence, within the existing roadside ditch, and gain access to the secure site. To mitigate the
potential security risk, the gap beneath the replacement fence is proposed to be filled-in with a
12-inch diameter stick of storm drainpipe, installed within the existing roadside ditch.
The Project will result in the installation of a 20-foot long, 12-inch diameter stick of ADS N-12 pipe,
installed within an existing, private roadside ditch consisting of a half-round 24-inch diameter
corrugated plastic pipe. The stick of pipe will be anchored in-place, and gravel backfill will be
provided on top and around the pipe to match existing adjacent grade. Both ends of the 12-inch
diameter pipe will be beveled, and a debris barrier will be secured to each beveled end. 12-inch
diameter pipe is selected to prohibit unauthorized personnel from passing through and is the
same size pipe as used further downstream in the existing stormwater drainage system.
Approximately 90 linear feet downstream, the existing private roadside ditch transitions to an
existing below grade 12-inch diameter storm drainpipe. The Project is not proposing to modify
the contributing flow to the existing private roadside ditch, and existing flow characteristics will
PSE SWARR STATION SECURITY MAINTENANCE PROJECT | Stormwater Technical Information Report
April 14th, 2026
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be maintained. The existing stormwater drainage system has not been observed to have capacity
issues and no other drainage improvements are proposed for this Project.
Per section 1.2.4.2, Conveyance Requirements for Existing Systems, of the 2022 RSWDM, existing
conveyance systems may be utilized if they can provide a minimum level of protection as-is or
with minor modifications. The existing onsite conveyance system will not experience a change in
flow characteristics (e.g., peak flows or volume of flows) as a result of the Project and thus is not
required to be analyzed for conveyance capacity, per Section 1.2.4.2 of the 2022 RSWDM.
6 Special Reports and Studies
The following special reports and studies associated with the Project have been completed and
are included in this Technical Information Report (TIR) as appendices:
• Appendix C: Geotechnical Design Memorandum SWARR Station – Security Perimeter
Maintenance Project, dated October 7th, 2025, prepared by GeoEngineers Inc.
• Appendix D: Geologically Hazardous Areas Report SWARR Station – Security Maintenance
Project, dated February 6th, 2026, prepared by GeoEngineers Inc.
• Appendix G: Arborist Report SWARR Station (Fence Raplcement Project), dated October
2025, prepared by Davey Resource Group, Inc.
7 Other Permits
A list of permits, approvals, and notifications expected to be required for Project Implementation
includes:
City of Renton
• Fence Variance
• Building Permit
• SEPA Environmental Checklist
Washington State Department of Ecology
• Construction Stormwater General Permit
8 CSWPP Analysis and Design
Since the Project will conduct construction activities that will clear, grade, or otherwise disturb
the site, erosion and sediment control to prevent, to the maximum extent practical, the transport
of sediment from the Project site to downstream drainage facilities, water resources, and adjacent
properties must be provided. The Project will conduct construction activities onsite or offsite and
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must provide stormwater pollution prevention and spill controls to prevent, reduce, or eliminate
the discharge of pollutants to onsite or adjacent stormwater systems or watercourses. To prevent
sediment transport and pollutant discharges as well as other impacts related to land-disturbing
and construction activities, Erosion and Sediment Control (ESC) measures and Stormwater
Pollution Prevention and Spill Control (SWPPS) measures that are appropriate to the Project site
must be applied through a comprehensive Construction Stormwater Pollution Prevention
(CSWPP) plan as described in Sections 1.2.5.1 and 1.2.5.3 and shall perform as described in Section
1.2.5.2 of the 2022 RSWDM.
Targeted ESC and SWPPS Best Management Practices (BMPs) applicable to the Project are
included in the Project Construction Stormwater Pollution Prevention Plan (CSWPP) prepared by
GeoEngineers (GeoEngineers, 2026a). The CSWPP is included as Appendix E. Construction
Stormwater Pollution Prevention Plan. A copy of the CSWPPP document must be maintained on-
site and available for City staff access and review during construction. The contractor will be
required to implement all required BMPs, provide TESC construction oversight, conduct required
monitoring and reporting, provide construction stormwater permit compliance, and provide
ongoing updates to the CSWPPP consistent with their means/methods of construction.
9 Bond Quantities, Facility Summaries, and
Declaration of Covenant
Not applicable per section 2.3.2 and specifically Table 2.3.2.A, Minimum Engineering Plan
Elements for Projects in Targeted Drainage Review, of the 2022 RSWDM, the Project is not
required to address Section 9: Bond Quantities, Facility Summaries, and Declaration of Covenant
under the TDR Category #2 requirements.
10 Operations and Maintenance Manual
Not applicable per section 2.3.2 and specifically Table 2.3.2.A, Minimum Engineering Plan
Elements for Projects in Targeted Drainage Review, of the 2022 RSWDM, the Project is not
required to address Section 10: Operations and Maintenance Manual under the TDR Category #2
requirements.
PSE SWARR STATION SECURITY MAINTENANCE PROJECT | Stormwater Technical Information Report
April 14th, 2026
hdrinc.com
555 110th Avenue NE, Suite 1200, Bellevue, WA 98004-5124
(425) 503-5815
P a g e | 1 9
11 References
City of Renton (COR) 2024. Pre-application Meeting for PSE SWARR Station – Security Perimeter
Maintenance, 2100 Benson Dr S (APN 2023059071, PRE-24-000335. November 21, 2024.
City of Renton (COR) 2025. COR Map Viewer Interactive mapping tool. Accessed December 5, 2025
from COR Maps | City of Renton
City of Renton Municipal Code (RMC) 4-6-030. Accessed December 5, 2025 from Renton Municipal
Code
City of Renton Surface Water Design Manual (RSWDM). 2022. Accessed December 5, 2025 from
2022 Surface Water Design Manual 2022 RSWDM
Davey Resource Group, Inc. (DRG) 2025. Arborist Report SWARR Station (Fence Replacement
Project), prepared for Puget Sound Energy dated October 2025.
GeoEngineers, Inc. (GeoEngineers) 2011. September 2010 and March 2011 Groundwater
Monitoring Report, SWARR Station, Renton Washington prepared for Puget Sound
Energy dated July 18, 2011. GEI File No. 0186-596-01.
GeoEngineers, Inc. (GeoEngineers) 2025. Geotechnical Design Memorandum – Pole and Fence
Foundations, SWARR Station – Security Perimeter Maintenance Project. 2100 Benson
Drive South, Renton, Washington, prepared for Puget Sound Energy and dated October
7, 2025. GEI File No. 9186-184-00 Task 2032.
GeoEngineers, Inc. (GeoEngineers) 2026a. Construction Stormwater Pollution Prevention and Spill
Control Plan, SWARR Station – Security Perimeter Maintenance Project Renton, King
County, Washington, prepared for Puget Sound Energy and dated April 2026. GEI File No.
9186-184-00 Task 2032.
GeoEngineers, Inc. (GeoEngineers) 2026b. Geologically Hazardous Areas Report, SWARR Station
– Security Maintenance Project WO 142003204, 2100 Benson Drive South Renton,
Washington, prepared for Puget Sound Energy and dated February 6, 2026. GEI File No.
9186-184-00 Task 2032.
King County (KC) 2025. King County iMap; Interactive mapping tool. Accessed December 5, 2025
from iMap
APPENDIX A
TIR WORKSHEET
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2022 City of Renton Surface Water Design Manual 6/22/2022
8-A-1
REFERENCE 8-A
TECHNICAL INFORMATION REPORT (TIR)
WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER
Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner _____________________________
Phone ___________________________________
Address __________________________________
Project Engineer ___________________________
Company _________________________________
Phone ___________________________________
Project Name __________________________
CED Permit # ________________________
Location Township ________________
Range __________________
Section _________________
Site Address __________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Land Use (e.g., Subdivision / Short Subd.)
Building (e.g., M/F / Commercial / SFR)
Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline
Management
Structural
Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
Puget Sound Energy (PSE)
(206) 496-4813
35131 SE Center Street,
Snoqualmie, Washington 98065
HDR
Jeff Becker, PE
(425) 503-5815
SWARR Security Maintenance
23 N
5 E
20
2100 Benson Drive South,
Renton, Washington 98055
Fence Variance
April 20th, 2026
April 14th, 2026
April 14th, 2026
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual
8-A-2
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Blanket
Description: (include conditions in TIR Section 2)
Approved Adjustment No. ______________________ Date of Approval: _______________________
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
Re: SWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: _____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
CR #2 - Offsite Analysis - Exempt
CR #6 - Maintenance and Operations - Exempt
No stormwater operational monitoring required
2022 City of Renton Surface Water Design Manual (2022 RSWDM)
Rolling Hills Creek On parcel to north and west
On parcel, central and eastern
High
On parcel to the east
Benson
Black River
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-3
Part 10 SOILS
Soil Type Slopes Erosion Potential
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
LIMITATION / SITE CONSTRAINT
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Threshold Discharge Area:
name or description)
Core Requirements (all 9 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Standard: _______________________________
or Exemption Number: ____________
Conveyance System Spill containment located at: _____________________________
Erosion and Sediment Control /
Construction Stormwater Pollution
Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Alderwood gravelly sandy
loam
15-30%Severe
Beausite gravelly sandy
loam
6-15%Moderate
Rolling Hills Creek - N/A
(1) Rolling Hills Creek
Exempt
Not Required - N/A
Not Required - N/A
Carla Woodworth
(425) 466-6772
(425) 466-6772
Exempt
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual
8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
On-site BMPs Describe:
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
Not Required - N/A
Not Required - N/A
Not Required - N/A
Residential Development Zone R-8
Not Required - N/A
The Project will result in the installation of a 20-foot long, 12-inch diameter stick of ADS N-12 pipe,
installed within an existing, private roadside ditch consisting of a half-round 24-inch diameter corrugated
plastic pipe. The stick of pipe will be anchored in-place, and gravel backfill will be provided on top and
around the pipe to match existing adjacent grade. Both ends of the 12-inch diameter pipe will be beveled,
and a debris barrier will be secured to each beveled end. 12-inch diameter pipe is selected to prohibit
unauthorized personnel from passing through and is the same size pipe as used further downstream in
the existing stormwater drainage system.
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed
BMPs/Facilities
Maintain Protective BMPs / Manage
Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure
operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Description Water Quality Description On-site BMPs Description
Detention
Infiltration
Regional
Facility
Shared
Facility
Other
Vegetated
Flowpath
Wetpool
Filtration
Oil Control
Spill Control
Other
Full Dispersion
Full Infiltration
Limited Infiltration
Rain Gardens
Bioretention
Permeable
Pavement
Basic Dispersion
Soil Amendment
Perforated Pipe
Connection
Other
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual
8-A-6
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4 High
Structural on Steep Slope
Other _______________________________
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were
incorporated into this worksheet and the attached Technical Information Report. To the best of my
knowledge the information provided here is accurate.
Signed/Date
Various public utility easements
4/14/2026
APPENDIX B
PROJECT DRAINAGE REVIEW CLASSIFICATION
SECTION 1.1 DRAINAGE REVIEW
6/22/2022 2022 City of Renton Surface Water Design Manual
1-14
FIGURE 1.1.2.A FLOW CHART FOR DETERMINING TYPE OF DRAINAGE REVIEW REQUIRED
1.1.2 DRAINAGE REVIEW TYPES AND REQUIREMENTS
2022 City of Renton Surface Water Design Manual 6/22/2022
1-15
TABLE 1.1.2.A REQUIREMENTS APPLIED UNDER EACH DRAINAGE REVIEW TYPE
Simplified
Single family residential projects that result in 2,000 sf of new plus replaced impervious
surface or 7,000 sf of land disturbing activity but do not exceed the new plus replaced PGIS,
new PGPS, and new pervious surface thresholds specified in Sec. 1.1.2.1. Note: The project may
also be subject to Targeted Drainage Review.
Directed
Single family residential projects that result in 2,000 sf of new plus replaced impervious
surface or 7,000 sf of land disturbing activity that are not subject to Simplified Drainage Review
or Large Project Drainage Review. The project may also be subject to Targeted Drainage Review.
Targeted
New and redevelopment projects that are not subject to Directed, Full or Large Project Drainage
Review, AND have characteristics of one or more of the following categories of projects:
1. Projects containing or adjacent to a flood, erosion, or steep slope hazard area; or projects
within a Landslide Hazard Drainage Area or Aquifer Protection Area .
2. Projects that construct or modify a drainage pipe/ditch that is 12 or larger or receive runoff
from a 12 or larger drainage pipe/ditch.
3. Redevelopment projects with $100,000 in improvements to a high-use site.(1)
Full
All projects that result in 2,000 sf of new plus replaced impervious surface or 7,000 sf of land
disturbing activity but are not subject to Simplified Drainage Review, Directed Drainage Review,
OR Large Project Drainage Review.
Large Project Projects that result in 50 acres of new impervious surface within a subbasin or multiple
subbasins that are hydraulically connected.
DRAINAGE REVIEW TYPE
Simplified Directed
Targeted
Full
Large
ProjectCateg1Categ2Categ3
SIMPLIFIED DRAINAGE
REQUIREMENTS SEE NOTE 4
CORE REQUIREMENT #1
Discharge at Natural Location (
4) (2,3) *(2)
CORE REQUIREMENT #2
Offsite Analysis (
4) (2,3) *(2) (3) (3) (3)
CORE REQUIREMENT #3
Flow Control Facilities (
4) (2,3) *(2) (3) (3)
CORE REQUIREMENT #4
Conveyance System (
4) (2,3) *(2)
CORE REQUIREMENT #5
Construction Stormwater
Pollution Prevention
4) (2,3)
CORE REQUIREMENT #6
Maintenance & Operations (
4) (2,3) *(2)
CORE REQUIREMENT #7
Financial Guarantees & Liability (
4) (2,3) *(2) (3) (3) (3) (3)
CORE REQUIREMENT #8
Water Quality Facilities (
4) (2,3) *(2) (3) (3)
CORE REQUIREMENT #9
On-site BMPs (
4)
Exempt per COR CED Pre-App
Meeting, 11/21/2024, PRE 24-000335
Exempt per COR CED Pre-App
Meeting, 11/21/2024, PRE 24-000335
SECTION 1.1 DRAINAGE REVIEW
6/22/2022 2022 City of Renton Surface Water Design Manual
1-16
TABLE 1.1.2.A REQUIREMENTS APPLIED UNDER EACH DRAINAGE REVIEW TYPE
DRAINAGE REVIEW TYPE
Simplified Directed
Targeted
Full
Large
ProjectCateg1Categ2Categ3
SPECIAL REQUIREMENT #1
Other Adopted Area-Specific
Requirements
4) (2,3) (3) (3) (3)
SPECIAL REQUIREMENT #2
Flood Hazard Area Delineation (
4) (2,3) (3) (3) (3)
SPECIAL REQUIREMENT #3
Flood Protection Facilities (
4) (2,3) (3) (3) (3)
SPECIAL REQUIREMENT #4
Source Control (
4) (2,3) (3) (3) (3) (3) (3)
SPECIAL REQUIREMENT #5
Oil Control (
4) (2,3) 3) (3) (3)
SPECIAL REQUIREMENT #6
Aquifer Protection Areas (
2,3) (3) (3) (3) (3) (3)
1) Category 3 projects installing oil controls that construct or modify a 12-inch pipe/ditch are also Category 2 projects.
2) May be applied by CED based on project or site-specific conditions. Documentation of compliance required.
3) These requirements have exemptions or thresholds that may preclude or limit their application to a specific project.
4) A proposed project subject to Simplified Drainage Review that complies with the Simplified drainage requirements detailed in Appendix
C is presumed to comply with all the core and special requirements in Sections 1.2 and 1.3 except those requirements that would apply
to the project if it is subject to Targeted Drainage Review as specified in Section 1.1.2.2.
1.1.2.1 SIMPLIFIED DRAINAGE REVIEW
Simplified Drainage Review is for small residential building projects or clearing projects that meet the
threshold requirements below. The core and special requirements applied under Full Drainage Review are
replaced with simplified drainage requirements that can be applied by a non-engineer. These requirements
include simple stormwater dispersion, infiltration, and site design techniques called flow control Best
Management Practices (BMPs), which provide the necessary mitigation of flow and water quality impacts
for small projects. Also included are simple measures for erosion and sediment control (ESC). This
simplified form of drainage review acknowledges that drainage impacts for many small project proposals
can be effectively mitigated without construction of costly flow control and water quality facilities.
The Simplified Drainage Review process minimizes the time and effort required to design, submit, review,
and approve drainage facilities for these proposals. In most cases, the requirements can be met with
submittals prepared by contractors, architects, or homeowners without the involvement of a civil engineer.
Note: some projects subject to Simplified Drainage Review may also require Targeted Drainage Review if
they meet any of the threshold criteria in Section 1.1.2.2.
Threshold
Simplified Drainage Review is required for any single family residential project that will result in
2,000 square feet8 or more of new impervious surface, replaced impervious surface, or new plus replaced
8 The thresholds of 2,000 and 7,000 square feet shall be applied by project site. All other thresholds specified in terms of
square feet of impervious or pervious surface shall be applied by threshold discharge area and in accordance with the
definitions of these surfaces in Section 1.1. Note: the calculation of total impervious surface may exclude any such added
impervious surface that is confirmed by CED staff to be already mitigated by a City approved and inspected flow control facility
or on-site BMP.
APPENDIX C
GEOTECHNICAL DESIGN MEMORANDUM
Memorandum
2101 4th Avenue, Suite 950, Seattle, Washington 98121, Telephone: 206.728.2674 www.geoengineers.com
To: Puget Sound Energy
From: Timothy D. Bailey, PE
Date: October 7, 2025
File: 9186-184-00, Task 2032
Subject: Geotechnical Design Memorandum –
Pole and Fence Foundations
SWARR Station – Security Perimeter
Maintenance Project
2100 Benson Drive South, Renton, Washington
Introduction
This design memorandum presents the results of GeoEngineers, Inc.’s (GeoEngineers) geotechnical
engineering services associated with the pole and fence foundations associated with the proposed security
perimeter maintenance project at the existing PSE Renton SWARR station located in Renton, Washington
(King County Parcel No. 2023059071). The project site is shown in relation to existing features in the
Vicinity Map, Figure 1 and the Site Plan, Figure 2.
We understand that Puget Sound Energy (PSE) is planning to replace the existing 6-foot-high chain-link
fence with a new 8-foot-high Tier 2 metal mesh fence that includes intrusion detection and is also planning
to install additional security cameras. However, it is anticipated that the new fence may be 2 to 4 feet taller
in some areas to accommodate the existing terrain and top of fence design elevation. The replacement
fence alignment will generally follow the existing fence alignment with some alignment shifts within the
existing fence perimeter to avoid tree removal.
This design memorandum incorporates PSE review comments and supersedes the previous version dated
November 5, 2024.
Scope of Services
Our services were completed in accordance with our proposal dated August 30, 2024 and included:
■Completing geotechnical explorations using hand tools and hand operated instruments at the site.
■Completing geotechnical laboratory testing on selected soil samples from the explorations.
■Providing geotechnical conclusions and recommendations for the proposed fence replacement
foundations and camera pole foundations, and
■Preparing this memorandum.
10/7/2025
Memorandum to Puget Sound Energy
October 7, 2025
Page 2
Geotechnical Field Exploration and Laboratory Testing
FIELD EXPLORATIONS
Subsurface conditions at the site were evaluated on September 27, 2024, by completing nine hand auger
explorations (HA-1 through HA-9) to depths ranging from approximately 0.5 to 2.5 feet below the ground
surface (bgs). The explorations included manual samples and direct cone penetrometer (DCP) testing to
evaluate soil density. A description of the field exploration program and summary exploration logs are
presented in Attachment A. The exploration locations are shown in Figure 2.
GEOTECHNICAL LABORATORY TESTING
Soil samples were obtained during the hand auger explorations and taken to GeoEngineers’ Redmond
laboratory for further evaluation. Selected samples were tested for the determination of grain-size
distribution (sieve analysis). A description of the laboratory testing and the test results are presented in
Attachment A or on the exploration logs.
Site Conditions
GEOLOGY
We reviewed the geologic map of the Renton quadrangle (Mullineaux et al., 1965). Surficial soils in the
project vicinity are mapped on the geologic map as ground moraine deposits consisting of mostly ablation
till over lodgment till (Qgt). Till generally consists of a medium dense to very dense unsorted mixture of clay,
silt, sand, gravel, cobbles and boulders. We observed a large glacial erratic boulder on site adjacent to the
access road, which is consistent with geologic mapping.
SURFACE CONDITIONS
The project site is approximately 16.7 acres in size and is developed with below-ground propane storage
tanks, process equipment that produces a mixture of propane and air, and a one-story building that houses
process equipment and control operations. The site is accessed from a paved road coming off South
Benson Drive to the west and is surrounded by a chain-link fence. The fenced site is bordered by South
Benson Drive to the west and by undeveloped forested areas to the north, south and east. The site is
located in a small valley, with the topography rising to the east and west. Rolling Hills Creek flows south-to-
north below the site in a culvert, with the culvert inlet structure located at the south end of the site, just
south of the access road.
SUBSURFACE CONDITIONS
The driveway ramp supporting the main paved entry is anticipated to consist of fill. Additionally, there are
unknown quantities and depths of fill supporting the main building pad and aboveground utility
infrastructure, as well as fill placed on top of the underground storage tanks (USTs).
Based on our explorations, subsurface conditions consist of fill and glacial till extending to the depths
explored. The fill is likely regraded glacial till and both the fill and glacial till consist of sand with variable
silt and gravel content.
Memorandum to Puget Sound Energy
October 7, 2025
Page 3
Groundwater was not observed in our explorations. During our September 27, 2024 site visit, we measured
groundwater levels in three existing monitoring wells at the site (well locations are noted in Figure 2).
The monitoring wells did not have Washington State Department of Ecology well tags, so we were unable
to locate the original boring logs. We identified the wells and associated depth to groundwater as follows:
■ MW-1 (south end of site, adjacent to access road) – groundwater at a depth of 19 feet.
■ MW-2 (north end of site, between tanks and access road) – groundwater at a depth of 16 feet.
■ MW-3 (southwest of the building) – groundwater at a depth of 10 feet.
GEOLOGICALLY HAZARDOUS AREAS
Geologically hazardous areas are discussed separately in another report being prepared by GeoEngineers.
Conclusions and Recommendations
FENCE POST AND CAMERA FOUNDATIONS
The new fence post foundations are anticipated to be 24 inches in diameter and 3 feet deep. The camera
pole foundations are anticipated to be 3 feet in diameter and 7 feet deep for 15-foot-high camera poles or
8.5 feet deep for 25-foot-high camera poles. The soil conditions for these foundations are anticipated to
consist of fill overlying glacial till.
If lateral bearing pressures are needed for design of post or pole foundations, an allowable lateral bearing
pressure of 1500 pounds per square foot (psf) can be used as a conservative value, which is consistent
with loose (blowcount, N = 10) soil in Table 17-2 in the Washington State Department of Transportation
Geotechnical Design Manual.
If LPile design parameters are needed for design of these foundations, the parameters presented in Table 1
below can be used. The soil parameters were developed based on our field explorations and extrapolation
of anticipated conditions below the depths explored, based on geologic mapping that shows glacial till and
the documented refusal conditions encountered in the hand auger explorations.
TABLE 1. 2021 LPILE PARAMETERS
SOIL PARAMETER FILL AND GLACIAL TILL
Depth below existing ground surface (feet) 0-10
Soil Type (p-y curve model) Sand (Reese)
Effective Unit Weight (pcf) 125
Friction Angle (degrees) 32
p-y Modulus, k (pci) 50
Notes:
pcf = pounds per cubic foot; pci = pounds per cubic inch
Memorandum to Puget Sound Energy
October 7, 2025
Page 4
Limitations
We have prepared this report for the exclusive use of PSE and their authorized agents for the proposed
SWARR Station – Security Perimeter Maintenance project in Renton, Washington.
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
generally accepted practices in the field of geotechnical engineering in this area at the time this report was
prepared. No warranty or other conditions, express or implied, should be understood.
Please refer to Attachment B, Report Limitations and Guidelines for Use, for additional information
pertaining to the use of this report.
References
Mullineaux, D.R., 1965, “Geologic map of the Renton quadrangle, King County, Washington,” U.S.
Geological Survey, Geologic Quadrangle Map GQ-405, 1:24,000.
Washington State Department of Transportation, February 2022, Geotechnical Design Manual M 46-03.16.
U.S. Geological Survey, MapView, accessed October 1, 2024 from web site:
https://ngmdb.usgs.gov/mapview/?center=-97,39.6&zoom=4.
GDT:TDB:mce
Attachments:
Figure 1. Vicinity Map
Figure 2. Site Plan
Attachment A. Field Explorations and Laboratory Testing
Figure A-1. Key to Exploration Logs
Figures A-2 through A-10. Logs of Explorations
Figure A-11. Sieve Analysis Results
Attachment B. Report Limitations and Guidelines for Use
Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table and/or figure), if provided, and any attachments are only a copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
SW
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Figure 1
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Source(s):• ESRI
Coordinate System: NAD 1983 UTM Zone 10N
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty orrepresentation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
SWARR
Security Perimeter Maintenance ProjectRenton, Washington
HA-4
MW-2
HA-5HA-6
HA-7
HA-8
MW-3
HA-9
HA-3
MW-1 HA-1 HA-2
Site Plan
SWARRSecurity Perimeter Maintenance ProjectRenton, Washington
Figure 2
0 120
Feet
Legend
Hand Auger Exploration Completed by GeoEngineers
Unknown Monitoring Well
Rebuild Fence - Approximate Location (2,133.3 feet)
Existing Fence (2,976.8 feet)
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400_F02_SitePlan_Tsk2032 Date Exported: 10/08/25 by maugust
Source(s):• Drawing updated with proposed fence alignment 10/3/24.• Roads, 2023 aerial, contours and parcel boundaries from King County GIS. http://www.kingcounty.gov/services/gis.aspx
Coordinate System: NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Attachment A
Field Explorations and Laboratory Testing
Memorandum to Puget Sound Energy
October 7, 2025
Page A-1
Attachment A
Field Explorations and Laboratory Testing
FIELD EXPLORATIONS
Subsurface conditions at the site were evaluated on September 27, 2024, by completing nine hand auger
explorations (HA-1 through HA-9). The approximate exploration locations are shown in the Site Plan,
Figure 2. Exploration locations were measured from existing site features.
Hand Auger Explorations
Hand auger explorations were completed by excavating using a post-hole digger and hand auger, with
samples collected manually. The density of the soils encountered in the explorations were evaluated using
a direct cone penetrometer (DCP), which uses a 15-pound hammer free-falling 20 inches to penetrate a
1.5-inch-diameter, 45-degree cone to a depth of 1¾ inch into the bottom of the hole. DCP blowcounts can
be correlated to standard penetration test (SPT) blowcounts. Both DCP and estimated SPT blow counts are
shown on the exploration logs at the evaluation depths.
Soils encountered in the explorations were visually classified in accordance with the classification system
described in Figure A-1. A key to the exploration log symbols is also presented in Figure A-1. The logs of the
explorations are presented in Figures A-2 through A-10. The logs reflect our interpretation of the field
conditions and the results of laboratory testing and evaluation of samples. They also indicate the depths at
which the soil types or their characteristics change, although the change might actually be gradual.
The ground surface elevations shown on the logs were estimated from GIS data.
LABORATORY TESTING
Soil samples obtained from the field explorations were transported to our laboratory and examined to
confirm or modify field classifications, as well as to evaluate index properties of the soil samples.
Representative samples were selected for laboratory testing consisting of the determination of sieve
analysis (gradation).
Sieve Analyses
Sieve analyses were performed on selected samples in accordance with ASTM International (ASTM) D 6913
to determine the sample grain-size distribution. The wet sieve analysis method was used to determine the
percentage of soil greater than the U.S. No. 200 mesh sieve. The results of the sieve analyses were plotted,
and samples were classified in accordance with the Unified Soil Classification System (USCS). Results are
presented in Figure A-11.
Measured groundwater level in exploration,well, or piezometer
Measured free product in well or piezometer
Distinct contact between soil strata
Approximate contact between soil strata
Contact between geologic units
SYMBOLS TYPICAL
DESCRIPTIONS
GW
GP
SW
SP
SM
FINEGRAINED
SOILS
SILTS ANDCLAYS
NOTE: Multiple symbols are used to indicate borderline or dual soil classifications
MORE THAN 50%RETAINED ONNO. 200 SIEVE
MORE THAN 50%PASSINGNO. 200 SIEVE
GRAVEL
ANDGRAVELLYSOILS
SC
LIQUID LIMITLESS THAN 50
(APPRECIABLE AMOUNTOF FINES)
(APPRECIABLE AMOUNTOF FINES)
COARSEGRAINEDSOILS
MAJOR DIVISIONS GRAPH LETTER
GM
GC
ML
CL
OL
SILTS AND
CLAYS
SANDS WITHFINES
SANDANDSANDY
SOILS
MH
CH
OH
PT
(LITTLE OR NO FINES)
CLEAN SANDS
GRAVELS WITHFINES
CLEAN GRAVELS
(LITTLE OR NO FINES)
WELL-GRADED GRAVELS, GRAVEL -SAND MIXTURES
CLAYEY GRAVELS, GRAVEL - SAND -CLAY MIXTURES
WELL-GRADED SANDS, GRAVELLYSANDS
POORLY-GRADED SANDS, GRAVELLYSAND
SILTY SANDS, SAND - SILT MIXTURES
CLAYEY SANDS, SAND - CLAYMIXTURES
INORGANIC SILTS, ROCK FLOUR,CLAYEY SILTS WITH SLIGHTPLASTICITY
INORGANIC CLAYS OF LOW TOMEDIUM PLASTICITY, GRAVELLYCLAYS, SANDY CLAYS, SILTY CLAYS,LEAN CLAYS
ORGANIC SILTS AND ORGANIC SILTYCLAYS OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS ORDIATOMACEOUS SILTY SOILS
INORGANIC CLAYS OF HIGHPLASTICITY
ORGANIC CLAYS AND SILTS OFMEDIUM TO HIGH PLASTICITY
PEAT, HUMUS, SWAMP SOILS WITHHIGH ORGANIC CONTENTSHIGHLY ORGANIC SOILS
SOIL CLASSIFICATION CHART
MORE THAN 50%OF COARSEFRACTION RETAINEDON NO. 4 SIEVE
MORE THAN 50%OF COARSEFRACTION PASSINGON NO. 4 SIEVE
SILTY GRAVELS, GRAVEL - SAND -SILT MIXTURES
POORLY-GRADED GRAVELS,GRAVEL - SAND MIXTURES
LIQUID LIMIT GREATERTHAN 50
Contact between soil of the same geologicunit
Material Description Contact
Graphic Log Contact
NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions.Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to berepresentative of subsurface conditions at other locations or times.
Groundwater Contact
Blowcount is recorded for driven samplers as the number ofblows required to advance sampler 12 inches (or distance noted).See exploration log for hammer weight and drop.
"P" indicates sampler pushed using the weight of the drill rig.
"WOH" indicates sampler pushed using the weight of thehammer.
Key to Exploration Logs
Figure A-1
ADDITIONAL MATERIAL SYMBOLS
SYMBOLS
Asphalt Concrete
Cement Concrete
Crushed Rock/Quarry Spalls
Topsoil
GRAPH LETTER
AC
CC
SOD Sod/Forest Duff
CR
DESCRIPTIONS
TYPICAL
TS
No Visible SheenSlight SheenModerate SheenHeavy Sheen
Laboratory / Field Tests
%F%GALCACPCSDDDSHAMCMDMohsOCPMPIPLPPSATXUCUUVS
Sheen Classification
NSSSMSHS
Percent finesPercent gravelAtterberg limitsChemical analysisLaboratory compaction testConsolidation testDry densityDirect shearHydrometer analysisMoisture contentMoisture content and dry densityMohs hardness scaleOrganic contentPermeability or hydraulic conductivityPlasticity indexPoint load testPocket penetrometerSieve analysisTriaxial compressionUnconfined compressionUnconsolidated undrained triaxial compressionVane shear
Continuous Coring
Bulk or grab
Direct-Push
Piston
Shelby tube
Standard Penetration Test (SPT)
Sampler Symbol Descriptions
Modified California Sampler (6-inch sleeve) or Dames & Moore
Rev. 03/2024
Brown silty sand (medium dense, moist)
Boring terminated at approximately 1.2 feet below ground surface(bgs) due to hand auger refusal
SM
1
Dynamic Cone Penetrometer (DCP) (15-poundhammer/20-inch drop) blowcount converted to anequivalent standard penetration test (SPT) blowcountbased on ASTM STP 399
DCP = 24 (SPT >20)
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
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Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-1
Figure A-2
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
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REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 1.25
181NAVD88 47.461129-122.205816 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Brown silty sand (medium dense, moist)
Boring terminated at approximately 2.5 feet bgs due to hand augerrefusal
SM
1SA 5
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 21 (SPT >15)34
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
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E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-2
Figure A-3
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
174
173
De
p
t
h
(
f
e
e
t
)
1
2
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 2.5
175NAVD88 47.461188-122.205435 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Brown silty sand with gravel (medium dense, moist)
Boring terminated at approximately 2 feet bgs due to hand augerrefusal
SM
1
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 19 (SPT >15)
Soil probe rod penetrated approximately ½-inch
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-3
Figure A-4
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
162
161
De
p
t
h
(
f
e
e
t
)
1
2
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 2
163NAVD88 47.462043-122.205436 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Forest duff
Dark brown poorly-graded fine to medium sand with silt and occasionalgravel and cobbles (medium dense, moist)
Brown well-graded gravel with silt and sand (medium dense, moist)
Boring terminated at approximately 2 feet bgs due to hand augerrefusal
DUFF
SP-SM
GW-GM
1SA 6
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 36 (SPT >20)Soil probe rod penetrated approximately ½-inch
Probe depth of ½-inch
9
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-4
Figure A-5
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
185
184
De
p
t
h
(
f
e
e
t
)
1
2
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 2
186NAVD88 47.463166-122.20554 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Forest duff
Brown silty sand (dense, moist)
Boring terminated at approximately 0.5 foot bgs due to hand augerrefusal
DUFF
SM
1
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 50 (SPT >30)Soil probe rod penetrated approximately ½-inch
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-5
Figure A-6
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
De
p
t
h
(
f
e
e
t
)
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 0.5
156NAVD88 47.463095-122.206579 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Forest duff
Gray-brown silty sand (dense, moist)
Boring terminated at approximately 1.5 feet bgs due to hand augerrefusal
DUFF
SM
1SA
18
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 50 (SPT >30)43
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-6
Figure A-7
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
158
De
p
t
h
(
f
e
e
t
)
1
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 1.5
159NAVD88 47.463089-122.206914 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Brown silty sand with organic matter (dense, moist)
Boring terminated at approximately 1.25 feet bgs due to hand augerrefusal
SM
1
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 50 (SPT >30)Soil probe rod penetrated approximately ½-inch
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-7
Figure A-8
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
160
De
p
t
h
(
f
e
e
t
)
1
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 1.25
161NAVD88 47.462747-122.206858 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Brown silty sand with organic matter (dense, moist)
Boring terminated at approximately 0.75 feet bgs due to hand augerrefusal
SM
1SA
7
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 50 (SPT >30)Soil probe rod penetrated approximately ¼-inch47
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
P
_
G
E
O
T
E
C
_
%
F
Sheet 1 of 1Project Number:
Project Location:
Project:
9186-184-00 Task 2032
Log of Hand Auger HA-8
Figure A-9
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Ele
v
a
t
i
o
n
(
f
e
e
t
)
De
p
t
h
(
f
e
e
t
)
Te
s
t
i
n
g
S
a
m
p
l
e
Gr
a
p
h
i
c
L
o
g
SAMPLE
MATERIAL
DESCRIPTION
Gr
o
u
p
Cla
s
s
i
f
i
c
a
t
i
o
n
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
REMARKS
Fin
e
s
Co
n
t
e
n
t
(
%
)
DateExcavated
Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 0.75
165NAVD88 47.462187-122.206559 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
Brown silty sand with gravel (dense, moist)
Boring terminated at approximately 1 foot bgs due to hand augerrefusal
SM
1
DCP (15-pound hammer/20-inch drop) blowcountconverted to an equivalent SPT blowcount based onASTM STP 399
DCP = 50 (SPT >30)Soil probe rod penetrated approximately ¼-inch to½-inch
Notes: See Figure A-1 for explanation of symbols.The depths on the hand-augered boring logs are based on an average of measurements across the hand-auger and should be considered accurate to ½ foot.Coordinates Data Source: Horizontal approximated based on . Vertical approximated based on .
Da
t
e
:
1
0
/
3
1
/
2
4
P
a
t
h
:
P
:
\
9
\
9
1
8
6
1
8
4
\
G
I
N
T
\
9
1
8
6
1
8
4
0
0
_
2
0
3
2
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
T
E
S
T
P
I
T
_
1
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9186-184-00 Task 2032
Log of Hand Auger HA-9
Figure A-10
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
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Surface Elevation (ft)Vertical Datum Coordinate SystemHorizontal DatumLatitudeLongitude
TotalDepth (ft)9/27/2024 1
167NAVD88 47.461836-122.206475 Decimal DegreesWGS84
JSP/JX
Checked By TB
Groundwater not observed
Caving not observedEquipment Hand Auger/DCP
Logged By Excavator GeoEngineers, Inc.
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09186-184-00 Date Exported: 10/16/2024
Note: This report may not be reproduced, except in full, without written approval of GeoEngineers, Inc. Test results are applicable only to the specific sample on which they were
performed, and should not be interpreted as representative of any other samples obtained at other times, depths or locations, or generated by separate operations or processes.
The grain size analysis results were obtained in general accordance with ASTM D6913. GeoEngineers 17425 NE Union Hill Road Ste 250, Redmond, WA 98052
#2001”#140
Attachment B
Report Limitations and Guidelines for Use
Memorandum to Puget Sound Energy
October 7, 2025
Page B-1
Attachment B
Report Limitations and Guidelines for Use1
This attachment provides information to help you manage your risks with respect to the use of this report.
READ THESE PROVISIONS CLOSELY
It is important to recognize that the geoscience practices (geotechnical engineering, geology and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
To help clients better understand how this difference pertains to our services, GeoEngineers includes the
following explanatory “limitations” provisions in its reports. Please confer with GeoEngineers if you need to
know more how these “Report Limitations and Guidelines for Use” apply to your project or site.
GEOTECHNICAL SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES, PERSONS AND
PROJECTS
This report has been prepared for Puget Sound Energy and their authorized agents and for the Project(s)
specifically identified in the report. The information contained herein is not applicable to other sites or
projects.
GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party
to whom this report is addressed may rely on the product of our services unless we agree to such reliance
in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its
schedule and budget, our services have been executed in accordance with our Agreement with Puget Sound
Energy dated August 30, 2024 and generally accepted geotechnical practices in this area at the time this
report was prepared. We do not authorize, and will not be responsible for, the use of this report for any
purposes or projects other than those identified in the report.
SUBSURFACE CONDITIONS CAN CHANGE
This geotechnical or geologic report is based on conditions that existed at the time the study was performed.
The findings and conclusions of this report may be affected by the passage of time, by man-made events
such as construction on or adjacent to the site, new information or technology that becomes available
subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or
groundwater fluctuations. If more than a few months have passed since issuance of our report or work
product, or if any of the described events may have occurred, please contact GeoEngineers before applying
this report for its intended purpose so that we may evaluate whether changed conditions affect the
continued reliability or applicability of our conclusions and recommendations.
INFORMATION PROVIDED BY OTHERS
GeoEngineers has relied upon certain data or information provided or compiled by others in the
performance of our services. Although we use sources that we reasonably believe to be trustworthy,
GeoEngineers cannot warrant or guarantee the accuracy or completeness of information provided or
compiled by others.
1 Developed based on material provided by GBA, GeoProfessional Business Associa�on; www.geoprofessional.org.
APPENDIX D
GEOLOGICALLY HAZARDOUS AREAS REPORT
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.861.6000
March 5, 2026
Puget Sound Energy
PO Box 97034 M/S EST-04W
Bellevue, Washington 98009-9734
Attention: Kathryn Hodges and Elaine Babby
Subject: Revised Geologically Hazardous Areas Report
SWARR Station Security Maintenance Project, WO 142003204
2100 Benson Drive South
Renton, Washington
File No. 9186-184-00 Task 2032
1.0 Introduction and Project Understanding
GeoEngineers, Inc. (GeoEngineers) was contracted by Puget Sound Energy (PSE) to perform a geologic
hazard and drainage evaluation in support of the SWARR Station Security Maintenance Project (project).
The project site was developed by Washington Natural Gas (now Puget Sound Energy) in 1965 as a “peak
shaving” facility for periods of high natural gas demand during cold weather.
We understand that PSE is proposing to replace the existing 6 to 7-foot-tall chain link fence around the
SWARR Station with a new 8- to 12-foot-tall metal mesh fence including intrusion detection and security
cameras to meet new Homeland Security requirements and PSE standards. PSE also plans to replace the
aging vehicle and pedestrian gates at the main entrance to Benson Drive South in the southwest corner of
the site and at the back entrance to South Puget Drive in the northeast corner of the site. The replacement
fence alignment will generally follow the existing fence alignment, with some segments shifting further into
developed areas. The fence will not move outward away from the developed station footprint. The security
system will be updated to current technology, with new security cameras and associated conduit and
electrical system adjustments. Conduits will be attached to the fence, to minimize trenching, except at gate
crossings and between power source at control building and fence where conduits will be routed below
ground. Minor excavation, including augering or hydrovactoring, for fence and camera post installation will
also occur as part of the project. Refer to the Project Narrative and project site plan (prepared by PSE) for
more detailed information on the proposed work.
The property is situated within Section 20 of Township 23 North and Range 05 East of the Willamette
Meridian (WM). The reference address for the property is 2100 Benson Drive South in Renton, Washington.
The SWARR Station is located on approximately 16.7-acre Parcel No. 2023059071; with the developed
portion of the site occupying the southern 8 acres of the property. The proposed fence, gate and security
Puget Sound Energy | March 5, 2026 Page 2
File No. 9186-184- 00 Task 2032
maintenance will take place within the developed portion of the site only and will not extend to the
undeveloped areas of the parcel. The project location is shown in Figure 1, Vicinity Map. The project and
the preliminary fence installation location as provided by PSE is shown in Figure 2, Fence Replacement Site
Plan.
This report is intended to provide baseline geologic hazard critical areas (landslide, erosion, steep slope
and coal mine hazards) and drainage review data to PSE in response to the November 21, 2024,
memorandum from the City of Renton (COR) Department of Community and Economic Development
summarizing COR’s comments during the November 21, 2024, PRE 24-000335 preapplication meeting
with PSE (COR 2024b). This report also generally satisfies the geotechnical soils report as required per the
2022 Renton Surface Water Design Manual (RSWDM), Section C.1.3 (COR 2022). The primary purpose of
the required soil report, as per RSWDM Section C.1.3, is to determine the feasibility of infiltrative Best
Management Practices (BMPs). No new infiltrative BMPs (e.g. bioswales, new infiltration basins, new
previous surfaces) are proposed for the project. Therefore, in our opinion site-specific infiltration testing is
not required and was not conducted for the project. Recommendations for on-site BMPs during construction
in accordance with RSWDM Appendix C are provided in this report. A summary of our stream assessment
services for the project is provided in our Stream Assessment Memorandum dated December 9, 2025
(GeoEngineers 2025b). A summary of our geotechnical engineering testing services associated with the
proposed fence replacement is provided in our Geotechnical Design Memorandum dated October 7, 2025
(GeoEngineers 2025a).
2.0 Scope of Services
The purpose of our services was to review the Renton Municipal Code (RMC) 4-3-050 and the 2022 RSWDM
requirements and exceptions and to perform a desktop-level study and site reconnaissance to characterize
geologic hazards, surface soil and bedrock, groundwater seepage and surface water conditions and
drainage patterns for the project. The information collected provides a basis for developing
recommendations regarding permitting requirements, potential geologic hazards, site drainage, erosion
control BMPs and site restoration recommendations to reduce the risk of adversely affecting geologic
hazards that may be present at or near the project.
Our specific scope of services included the following:
1. Reviewed readily available published geologic, soil and groundwater well data and our in-house files
for existing information on soil, geologic hazards and groundwater conditions in the site vicinity.
2. Reviewed RMC 4-3-050 and 2022 RSWDM requirements and exemptions.
3. Reviewed RMC 4-3-050 for Geologic Critical Areas (COR 2024a), 2022 RSWDM, Section C.1.3, King
County (KC) (KC 2024), Office of Surface Mining Reclamation and Enforcement (OSMRE; 2024) and
the Washington State Department of Natural Resources (DNR 2024a) websites to identify delineated
geological hazard areas in the project area and to evaluate requirements for work completed within
geologic hazard critical areas.
4. Reviewed COR review comments provided in a memorandum from the COR dated November 21, 2024
(COR 2024b).
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File No. 9186-184- 00 Task 2032
5. Reviewed and interpreted hillshade imagery and topographic maps derived from bare earth Light
Detection and Ranging (lidar) data available from DNR (DNR 2024b) for the site and adjacent
properties.
6. Completed a site visit to the SWARR Station location to assess the adjacent slopes for surface
indications of slope instability, erosion, drainage and groundwater seepage.
7. Evaluated the potential impacts to slope stability, erosion, drainage and coal mine hazards at the
project location.
8. Prepared this preliminary letter report summarizing our desktop review, site reconnaissance
observations, and preliminary erosion control and site restoration recommendations.
3.0 Desktop Reviews
3.1. GEOLOGIC CONDITIONS
As shown in Figure 3, Geology, geologic mapping obtained from the DNR (DNR 2024a) indicates that the
project area is underlain by Pleistocene-aged continental glacial till (Qgt). However, the DNR mapping and
smaller scale mapping we reviewed (Schuster et al. 2015; Mullineaux, D.R. 1965), indicates that the glacial
till is in turn predominately underlain by continental sedimentary rocks of the Puget Sound Group (Tr)
consisting of sandstone, siltstone, shale, carbonaceous shale, claystone and coal.
We reviewed available well reports from the Washington State Department of Ecology (Ecology; 2024) for
geotechnical soil borings completed at the project site and Renton School District at Talbot Hill Elementary
School located at 578 23rd Street (approximately 1,500 feet southwest of the project site), where the
subsurface geology is mapped as having similar geologic conditions as the project site. Our review of these
well logs indicated that the project area is likely underlain by approximately 16 to 25 feet of silt, sandy silt
and gravel (glacial till), which are in turn underlain by the Puget Sound Group rocks.
3.2. SOIL CONDITIONS
Based on soil information available from the United States Department of Agriculture (USDA) National
Resources Conservation Service (NRCS) (USDA-NRCS 2024), the project location is underlain by two distinct
surficial soil units. Soil units are shown graphically in Figure 4, Soils and Erosion Hazards.
The majority of the site is underlain by a soil unit referred to as the Alderwood gravelly sandy loam, 15 to
30 percent slopes. The soil is described as having a parent material of glacial drift and/or glacial outwash
and being a gravelly sandy loam from 0 to 7 inches and very gravelly sandy loam between 7 to 59 inches.
This soil unit is classified by the NRCS as having a severe erosion hazard, being moderately well-drained
and having a very low to moderately low infiltration rate of between 0.00 and 0.06 inches per hour. The
depth to the water table is reported to be 18 to 37 inches.
The minor soil unit located along the western boundary of the project is referred to as the Beausite gravelly
sandy loam characterized by 6 to 15 percent slopes. The soil is described as having a parent material of
till, over weathered soils from sandstone, being a gravelly, ashy sandy loam from 0 to 38 inches, and as
bedrock between 38 to 42 inches. This soil unit is classified by the NRCS as having a moderate erosion
Puget Sound Energy | March 5, 2026 Page 4
File No. 9186-184- 00 Task 2032
hazard, being well-drained and having a moderately high infiltration rate of between 0.57 and 1.98 inches
per hour. The depth to the water table is reported to be more than 80 inches.
We did not complete infiltration tests for the project because no new infiltration structures are planned for
the project and the project will not alter existing site run-off or infiltration.
3.3. CITY OF RENTON GEOLOGIC CRITICAL AREA MAPPING
The COR Geologic Critical Areas, as defined in COR 4-3-050B, include regulated slopes, landslide, erosion,
seismic and/or coal mine hazards. Geologic hazards, including regulated slopes, erosion, coal mine and
landslide hazards, are shown in Figures 3 through 8.
3.3.1. Potential Erosion Hazard Areas
The COR maps potential erosion hazard areas as shown in Figure 4. The COR defines significant erosion
hazards as those soils that may experience high erosion (COR 2024a). The central and eastern portions of
the project area are mapped within a potential high erosion hazard area. This area generally corresponds
to the NRCS mapping of the Alderwood gravelly sandy loam soil units classified as having a severe erosion
hazard.
3.3.2. Regulated Slope Hazard Areas
We reviewed the Regulated Slope maps available from COR (COR 2024a) to characterize mapped slope
steepness at the site. As shown in the Regulated Slopes map, Figure 5, most of the project area and site
are mapped with slopes less than 25 percent. However, cut and fill slopes associated with construction
activities for the development of the project site, the main entrance to the site off Benson Drive South,
Benson Drive South and South Puget Drive are mapped as steep slopes with gradients greater than
15 percent and less than or equal to 25 percent, Sensitive Slopes (slopes which are greater than 25 percent
and less than or equal to 40 percent) and/or Protected slopes (slopes which are greater than 45 percent
and less than or equal to 90 percent).
3.3.3. Potential Coal Mine Hazard Areas
As shown in Figure 6, Coal Mine Hazards, moderate and high coal mine hazards are mapped on the eastern
side of the project. Based on our review of information available from DNR, the area was mapped in 1915
to include mine workings and railroad tracks of the Old Talbot Mine workings of the Renton Coal Mine,
owned by the Renton Coal Company. The mapped moderate and high coal mine hazards from the COR is
overlain on a georeferenced detailed map available from DNR in Figure 6, which indicates that the
northeast portion of the project site is located directly over mapped mine shafts related to the coal seams
within the 1st and 2nd Levels West of the Old Talbot Mine. Based on our review of the coal mine maps and
stratigraphic sections, these mine levels are typically more than 77 and 248 feet below the ground surface,
respectively. We reviewed information from the OSMRE regarding reported repairs, subsidence and
enforcement actions and no reports of repairs, subsidence or enforcement actions are reported for the site.
Based on our communications with Lori Ford of the OSMRE on October 24, 2024, she confirmed that there
has not been an investigation or reclamation project associated with the project site recorded or completed
by OSMRE in the OSMRE database.
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File No. 9186-184- 00 Task 2032
3.3.4. Potential Landslide Hazard Areas
Based on our review of information available from the COR, King County and DNR, the COR Landslide
Severity is mapped as High within all but the southwest corner of the project location. COR Landslide
Severity mapping is shown in Figure 7, Landslide Severity. Individual landslides or deposits are not mapped
within or adjacent to the project location.
We also reviewed the most recent lidar hillshade model available from the DNR lidar portal, as shown in
Figure 8, Lidar Interpretation (DNR 2024b). Based on our interpretation of the lidar hillshade model, the
site is not located on a historic landslide, nor are there historic landslides in the near vicinity of the project
location.
3.3.5. Potential Seismic or Volcanic Hazard Areas
Based on our review of information available from the COR, King County and DNR, there are no mapped
seismically active faults or volcanic hazard areas mapped near the project area.
3.4. GROUNDWATER
GeoEngineers (GeoEngineers 2025a) completed nine hand auger borings (HA-1 through HA-9) for our
geotechnical work at the site to depths ranging from 0.5 feet to 2.5 feet below the ground surface (bgs) on
September 27, 2024, to evaluate soils and groundwater conditions along the proposed project fence line
alignment. Groundwater was not observed in the hand auger borings. Based on our explorations,
subsurface conditions consist of fill to the depth explored. The fill consists of poorly-graded sand with silt
and gravel, silty sand and organic matter and extends to a depth of 2 feet below ground surface (bgs).
GeoEngineers (GeoEngineers 2011) installed 10 monitoring wells at the site between 2003 and 2007 as
part of a previous environmental study at the site. The approximate locations of the monitoring wells are
shown in Figure 2 and Appendix A, Site Plan and Groundwater Elevations – March 2011, Figure A-1, Site
Plan. Groundwater levels were measured in the wells during monitoring events in September 2010 and
March 2011. Depths to groundwater measured in the vicinity of the storage and pumping facilities (MW-1
through MW-4, and MW-7 through MW-10) ranged from approximately 2.7 to 11.4 feet bgs in
September 2010 and March 2011. Depths to groundwater measured in upgradient well MW-5 located on
the south side of the site entrance driveway ranged from approximately 7.8 to 17.8 feet bgs. Depths to
groundwater measured in downgradient well MW-6 in the northeast corner of the developed site ranged
from approximately 14.3 to 22.4 feet bgs. Seasonal fluctuation of groundwater levels (higher levels in the
spring) is common throughout western Washington. Based on the depths to groundwater and groundwater
elevations in the wells, the shallow groundwater flow direction at the site was to the northeast during the
September 2010 and March 2011 monitoring events. This flow direction is consistent with previous
monitoring events evaluated since 2005 and reflects the topographic slope at the site. Groundwater
elevations and the inferred flow direction based on the March 2011 groundwater measurements are shown
in Figure A-2, Groundwater Elevations – March 2011.
Based on our review of information from the COR, the project site is not located within a Wellhead Protection
Area mapped by the COR (COR 2024a).
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File No. 9186-184- 00 Task 2032
3.5. DRAINAGE CONDITIONS
Based on our review of information available from COR (COR 2024a), the site is within the COR Flow Control
Duration Standard (matching forested conditions) and within the Black River drainage basin. The project
does not contain or is not adjacent to an aquifer protection area. Land use in the area includes residential
development zone R-8.
According to the COR Utility Geographic Information System (GIS) data (COR 2024a), there are multiple
stormwater discharge points that direct water towards the SWARR Station parcel from offsite roadways and
parking lots. Surface water along Benson Drive South collects within curbside gutters and enters three
catch basins located on the east side of Benson Drive South Road adjacent to the west side of the project
parcel (Figure 2). Stormwater along this portion of Benson Drive South as well as stormwater from the north
side of Benson Drive South, South 21st Street and South 19th Street enters the stormwater drain system
and discharges at a point outside of the northwest corner of the project area (Figure 2). As discussed below
in Section 4.0 Site Reconnaissance, we observed evidence of water sheet flow (fine sediments, organic
matter accumulation) from the discharge point that flows northeast through the northwest corner of the
existing fence line towards Rolling Hills Creek. This sheet flow either infiltrates or eventually flows into
Rolling Hills Creek.
Surface water along South Puget Drive adjacent to the site is collected within curbside gutters and enters
two catch basins located on the east and west sides of South Puget Drive. Water in the east catch basins
flows directly to the catch basins on the west side of South Puget Drive which discharges stormwater onto
the slopes on the east side of the project area. As discussed below in Section 4.0, we observed that plastic
piping has been installed on the site slopes to capture the discharged water and transport it to the base of
the slopes. Based on our surface reconnaissance, the water then flows into the half-rounds that have been
installed on the east side of the site access road to convey the water along the toe of the slopes to the
northeast corner of the site where the water flows into an existing catch basin and then discharges to
Rolling Hills Creek on the north side of the developed site.
Surface water near the intersection of South Puget Drive and Benson Road South enters a series of catch
basins located near the intersection. This water then flows through the stormwater drain system and
discharges to the slopes southeast of the project area into a tributary that directs flow westward towards
Rolling Hills Creek. However, as discussed below in Section 4.0, due to natural topography, water does not
directly enter the stream and evidence of standing water was observed just east of the south portion of the
site where Rolling Hills Creek enters the culvert (Figure 2).
According to COR, Rolling Hills Creek is mapped as an open channel on the north and south sides of the
project area. The creek flows through a culvert beneath the ground surface of the project area. As discussed
below in Section 4.0, Rolling Hills Creek was observed flowing into the culvert inlet at the south end of the
project site and discharging to an open stream channel at the north end of the project site.
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File No. 9186-184- 00 Task 2032
4.0 Site Reconnaissance
4.1. GENERAL
A GeoEngineers’ Washington licensed geologist conducted a site reconnaissance on September 12, 2024,
to observe site conditions. The project site is situated in the southern portion of the parcel which is located
in a northwest-southeast trending drainage of Rolling Hills Creek. The site is situated on a relatively flat to
very gently sloping (slope gradients of 0 to 15 percent) ground surface. The developed portion of the site is
bounded by a gently sloping (slope gradients between 5 to 15 percent) forested area to the north, by steep
slopes (slope gradients ranging between 40 to 65 percent) up to South Puget Drive and businesses to the
east, by gentle slopes (slope gradients between 5 to 20 percent) uphill to single-family residential
developments to the south and to the west by steep slopes (slope gradients ranging between 40 to
70 percent) up to Benson Drive South, the PSE Seattle South Gate Station, tennis courts, single-family
residential developments and forested areas. Slopes around the site are vegetated with evergreen and
deciduous trees and shrubs, blackberries, ivy, grass and other understory vegetation. Photographs
presented in Figures B-1 and B-14 in Appendix B, Site Photographs.
In general, the existing facilities located near the center of the project site include a one-story metal sided
building, natural gas piping and aboveground storage tanks situated on a gravel surface. Existing
underground storage tank facilities are located on the north side of the project site where the ground
surface is vegetated with grass. The south side of the project site contains the main driveway into the site
facilities and parking area, east to west trending underground gas pipelines, forested habitat with little
understory vegetation and maintained grass areas. The northern portion of the parcel (outside of the fenced
facility) is undeveloped and forested with shrub understory. Grading to construct the SWARR Station
facilities resulted in the relatively flat to gently sloping ground surface between approximately elevation 160
above mean sea level (MSL) to approximately 150 feet MSL from south to north. The project area is
approximately 10 to 30 feet lower in elevation than Benson Drive South on the west side of the site and
between approximately 50 and 90 feet lower in elevation than South Puget Drive on the east. Figure 2
provides an overview of the project site.
4.2. REGULATED SLOPES, POTENTIAL EROSION HAZARDS AND POTENTIAL
LANDSLIDE HAZARDS
During our site visit, we observed that the mapped regulated slopes and landslide hazards on the south
side of the project area near the site entrance are associated with the engineered construction fill
embankments for the paved driveway into the SWARR Station from Benson Drive South. The slopes are
inclined at about 100 percent (1H:1V [Horizontal:Vertical]) and are up to 9 feet high. The slopes are
vegetated with grass and blackberries. We did not observe indications of instability or landsliding, surface
water, groundwater seepage or erosion on the portions of the slopes that we observed. Slopes and site
features are shown in the photographs provided in Figures B-1, B-2 and B-3 in Appendix B.
We observed that the mapped regulated slopes and mapped landslide severity hazard on the east side of
the project area are associated with native slopes and the engineered construction cut and fill
embankments for South Puget Drive and the SWARR Station. The native slopes are inclined up to
65 percent and graded slopes are inclined at about 100 percent (1H:1V) and combined are up to 90 feet
high. The slopes are vegetated with grass, evergreen and deciduous trees and shrubs, blackberries, ivy,
Puget Sound Energy | March 5, 2026 Page 8
File No. 9186-184- 00 Task 2032
horsetail ferns and other understory herbaceous vegetation. We did not observe indications of instability or
landsliding on the portions of this slope that we observed, nor did we observe surface water, groundwater
seepage or erosion on these slopes. However, horsetail ferns, plants that prefer extended periods of wet
soil conditions, were observed near the toe of the slope near the half-round culvert. Slope and site features
are shown in Figure B-4, B-5 and B-6.
The regulated slopes and mapped landslide severity hazard on the north side of the project site include
graded fill slopes associated with the construction fill pads for the developed northern area of the site. The
fill slopes range between 2 and 10 feet high and are inclined at about 100 percent (1H:1V). We did not
observe indications of instability (ground cracks, recent or past landsliding, erosion, fallen trees) landslide,
surface water or groundwater seepage on the portions of the slopes that we observed. However, we
observed a 10- to 15-foot-wide area of erosion on the slope on the north side of the existing fence line
where the culvert conveying Rolling Hills Creek beneath the site outlets to an open channel. The water
outfall has eroded the slope to be inclined to near vertical at the culvert outlet. The slope along the north
side of the site is vegetated with blackberry, ivy, deciduous trees and shrubs as shown in the photographs
provided in Figure B-7.
We observed that the regulated slopes and mapped landslide severity hazard on the west side of the project
area are associated with native slopes and the engineered construction cut and fill embankments for
Benson Drive South, the SWARR Station and several 2- to 3-foot-high rock walls and concrete ditch line
constructed at the toe of the slopes at the edge of the gravel pad for the building and other SWARR Station
facilities. The native slopes are inclined up to 50 percent. The graded slopes are inclined at about
100 percent (1H:1V) and are up to 30 feet high. We did not observe indications of instability or landsliding
on the portion of this slope or the rock walls that we observed. Nor did we observe surface water,
groundwater seepage or erosion on these slopes, except for indications of surface water flow from the
storm drain outlet from Benson Road South in the northwest corner of the site as described in
Section 3.5 Drainage Conditions above. We observed sediment and organic material captured on the
outside surface of the fence in the northwest corner of the site. Slopes and site features are shown in the
photographs provided in Figures B-8, B-9, B-10, B-11 and B-12.
The remaining portions of the project site mapped within a severe landslide hazard are related to the
relatively flat, graded developed area of the site. No evidence of landsliding or landslide deposits were
observed in these areas.
4.3. DRAINAGE CONDITIONS
The majority of the precipitation and surface water at the project site generally infiltrates into the vegetated
ground surfaces around the perimeter of the site.
Surface water near the site building and gravel areas near the building either:
■ Infiltrates into the gravel areas,
■ Flows to the west and south into the concrete swales and catch basins at the base of the rockery walls
and then to the vegetated swale located in the northwest corner of the project site (Figures B-8, B-9
and B-10), or
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■ To the north into the concrete swales, grass-covered underground tank area or to the grass-lined swale
located within the underground tank area (Figure B-13).
Surface water flowing along the paved and gravel driveways flows off these surfaces into either:
■ Vegetated areas adjacent to these surfaces to infiltrate (Figure B-7),
■ The open half-round culvert on the east side of the driveway to the north side of the developed site and
then to Rolling Hills Creek once outside of the fenced project area (B-2), or
■ The concrete swale and culverts located on the west side of the driveway that conveys water to Rolling
Hills Creek culvert near the underground tank area.
Surface water along Benson Drive South is collected within curbside gutters and enters catch basins
located on the east and west sides of Benson Drive South roadway rights-of-way (ROWs). The stormwater
then discharges at a point outside of the northwest corner of the project area and flows towards Rolling
Hills Creek (Figure 2). We observed evidence of water sheet flow that originated from the storm drain
discharge point and flowed northeast through the perimeter site fence in the northwest corner of the site
then towards Rolling Hills Creek (Figure B-12).
Surface water along South Puget Drive adjacent to the site is collected within curbside gutters and enters
two catch basins located on the east and west sides of South Puget Drive which discharge stormwater
directly onto the slopes on the east side of the project area (Figure 2). We observed that plastic piping or
half-rounds have been installed on the site slopes to capture the discharged water and transport it to the
base of the slopes, where the water is discharged into the half-rounds at the toe of the slopes and on the
east side of the driveway. We did not observe evidence of erosion along the slopes that we observed
(Figures B-3, B-4, B-5 and B-6).
Surface water near the intersection of South Puget Drive and Benson Road South enters a series of catch
basins located near the intersection and eventually discharges into a tributary that directs flow westward
towards Rolling Hills Creek (Figure 2). We observed that due to the flatter topography at the toe of the slope,
the stormwater does not directly flow into the stream and evidence of standing water was observed just
east of where Rolling Hills Creek enters the culvert in the south (Figure B-3).
Rolling Hills Creek was observed flowing from the south onto the project site in an open channel and then
into an underground culvert inlet in the southeast corner of the project site. The culvert conveys the water
beneath the site and then discharges the water back to an open channel at the north end of the project
site. PSE indicated that when creek flow is too high, water collects at the culvert inlet and some of the water
flows into the half-round culvert located east of the creek and the driveway (Figures B-7 and B-14). This
water is conveyed within the half-round and segment of underground culvert to the north side of the project
site, where the water discharges back to Rolling Hills Creek. We did not observe evidence of erosion along
Rolling Hills Creek or half-round, except for minor erosion at the culvert outlet on the north side of the
project area as described above in Section 4.1 General. A more detailed description of Rolling Hills Creek
is provided in our Stream Assessment Memorandum (GeoEngineers 2025b).
Puget Sound Energy | March 5, 2026 Page 10
File No. 9186-184- 00 Task 2032
4.4. POTENTIAL COAL MINE HAZARD AREAS
We did not observe indications of settlement or subsidence at the project site where the COR moderate
and high coal mine hazards are mapped. PSE representatives attending the September 12, 2024, site
reconnaissance indicated that they and PSE have no record of reported settlement or subsidence occurring
at the project site.
5.0 City Of Renton Preapplication Review Discussion
GeoEngineers reviewed the COR’s review comments provided in a memorandum from the COR dated
November 21, 2024 (COR 2024b). Based on the review comments, permitting for the project must comply
with the requirements of COR 2022 RSWDM, Section C.1.3 and RMC 4-3-050 for Geologic Critical Areas as
applicable for the completed project since the project area contains COR mapped geologic hazards,
including erosion, regulated slope, landslide and coal mine hazards.
The COR provided the following comments regarding geologic hazards. GeoEngineers’ Reponses to the
geologic hazard review comments are included in each section below. Responses to the COR’s storm
drainage comments will be provided by others involved in the project.
Comment 1: “The site contains critical areas. There is a coalmine hazard with a severity of high, an Erosion
Hazard and a Landslide hazard all mapped on-site.”
Response 1: Based on our review, we concur that critical areas, including a severe coal mine hazard, an
erosion hazard and a landslide hazard, are mapped at the site. Based on our desktop study and site
reconnaissance, our findings regarding the mapped hazards are summarized below:
■ Severe Coal Mine Hazard: no recorded investigations or reclamation projects associated with the
project site recorded or completed by OSMRE and we did not observe indications of settlement or
subsidence at the project site where the COR moderate and high coal mine hazards are mapped.
■ Erosion Hazard: the central and eastern portions of the project area are mapped within a potential high
erosion hazard area. This area generally corresponds to the NRCS mapping of the Alderwood gravelly
sandy loam soil units classified as having a severe erosion hazard. We did not observe evidence of
erosion within the project area, except for minor erosion at the Rolling Hills Creek culvert outlet on the
north side of the project area and the evidence of water sheet flow from the discharge point that flows
northeast through the northwest corner of the existing fence line towards Rolling Hills Creek.
■ Landslide Hazards: the project site is mapped within a COR mapped high landslide hazard area within
all but the southwest corner of the project, which is mapped within a COR moderate landslide area
location. The mapped landslide hazards along the perimeter of the site are associated with the
unretained graded slopes on the north, east, south and west sides of the project site. The remaining
portions of the project site mapped within a severe landslide hazard are related to the relatively flat,
graded developed area of the site. We did not observe evidence of recent landsliding or landslide
deposits within the project site during our site reconnaissance.
In our opinion, there is a low risk that the project would adversely affect the stability of the mapped coal
mine, erosion and landslide hazard areas and site slopes because: (1) the fence posts and electrical
Puget Sound Energy | March 5, 2026 Page 11
File No. 9186-184- 00 Task 2032
conduit excavations will be shallow and unlikely to affect the stability of any underground mine shafts or
workings; (2) the fence post installation would occur at the base of the slope but do not require significant
excavation that would cut the toe of the slope; (3) the project does not include grading that could affect the
stability of the slope; and (4) the project will not result in increased drainage, erosion or water flow that
could erode and destabilize the slope.
The project will disturb the site and therefore, must provide erosion and sediment controls during
construction to prevent, to the maximum extent practicable, the transport of sediment from the project site
to downstream drainage facilities, water resources and adjacent properties. We understand that PSE will
develop a project-specific Erosion and Sediment Control Plan (ESCP) to be implemented during construction
to satisfy this requirement. The current COR Surface Water Standard Plans and standard details will be
utilized in the development of erosion and sediment control and stormwater pollution prevention control
plans for the proposed project.
Comment 5: “A geotechnical soils report for the site is required per the 2022 Renton Surface Water Design
Manual Section C.1.3. Information on the water table and soil permeability (measured infiltration rates),
with recommendations of appropriate on-site BMPs per Core Requirement #9 and Appendix C shall be
included in the report. The report should also include information concerning the soils, geology, drainage
patterns and vegetation present shall be presented in order to evaluate the drainage, erosion control and
slope stability for site development. The applicant must demonstrate the development will not result in soil
erosion and sedimentation, landslide, slippage, or excess surface water runoff.”
Response 5: This report generally satisfies this requirement. The primary purpose of the required soil
report, as per RSWDM Section C.1.3, is to determine the feasibility of infiltrative BMPs. No new infiltrative
BMPs (e.g. bioswales, new infiltration basins, new previous surfaces) are proposed for the project.
Therefore, in our opinion site-specific infiltration testing is not required and was not conducted for the
project. Recommendations for on-site BMPs during construction in accordance with RSWDM Appendix C,
are provided later in this report. Additional geotechnical information and a summary of our geotechnical
engineering testing services associated with the proposed fence replacement is provided in our
Geotechnical Design Memorandum dated October 7, 2025 (GeoEngineers 2025a).
Comment 6: “Erosion control measures to meet the City requirements shall be provided.”
Response 6: Understood, no comment.
6.0 Conclusions
6.1. CRITICAL AREAS
Based on our evaluation as presented herein, there is a low risk of the proposed fence installation adversely
affecting the regulated slopes adjacent to the project site. Furthermore, in our opinion the project will not
result in soil erosion and sedimentation, landsliding or excess surface water runoff. In our opinion, the
project will not increase the threat of geologic hazards to adjacent or abutting properties; and the project
will not adversely impact other critical areas; and the project can be safely accommodated at the site if the
project is completed following our recommendations below.
Puget Sound Energy | March 5, 2026 Page 12
File No. 9186-184- 00 Task 2032
The majority of the project site is mapped as either a moderate or high coal mine hazard. In our opinion
there is a low risk of the project adversely affecting these mapped hazards because no infiltrative BMPs
are proposed for the project, only shallow trenching for camera electrical conduit is required for the project
and no new impervious surfaces will be created as part of the project. The excavation and site restoration
of impervious surfaces will not result in new additional development-related runoff or infiltration that could
increase the risk of subsidence. Conversely, in our opinion there is a low risk of subsidence resulting from
the mapped coal mine hazard adversely affecting the project work primarily because the mapped mine
shafts are more than 50 feet beneath the ground surface of the project area.
6.2. CITY OF RENTON STORM DRAINAGE
As discussed in Section 5.0 City of Renton Preapplication Review Discussion, in our opinion the project
would require a development of an erosion and sediment control plan and implementation of that plan
during construction to prevent, to the maximum extent practicable, the transport of sediment from the
project site to downstream drainage facilities, water resources and adjacent properties. The required
Erosion and Sediment Control (ESC) measures and Stormwater Pollution Prevention and Spill Control
(SWPPS) measures provided in an ESCP and Construction Stormwater Pollution Prevention (CSWPP) Plan
for the project will be developed and implemented during the project in compliance with the 2022 RSWDM.
7.0 Recommendations
We recommend preparing an ESCP and CSWPP plan to be included in the project permit submittals.
Development of the ESCP will require a topographic survey to accurately depict site topography and
drainage directions, existing structures and slopes on or directly adjacent to the site, existing impervious
and pervious surfaces, and existing drainage structures (e.g. catch basins) so that a complete ESCP can be
developed and appropriate erosion control BMPs can be chosen and shown on the ESCP. We anticipate
that ESC and CSWPP measures would include but may not be limited to: construction limits fencing, silt
fence, ditch check dams, catch basin inserts, temporary soil stockpile plastic covering, maintaining
construction entrances, and approved concrete washouts and handling procedures.
8.0 Limitations
GeoEngineers has prepared this report in general accordance with the limitations of our scope of work.
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
the generally accepted practices for critical areas reports including geologic hazard identification and
evaluation in this area at the time this report was prepared. No warranty or other conditions, express or
implied, should be understood.
This report has been prepared for the exclusive use of PSE, their authorized agents and regulatory agencies
following the described methods and information available at the time this report was prepared. No other
party may rely on the product of our services unless we agree in advance to such reliance in writing. The
information contained herein should not be applied for any purpose or project except the one originally
contemplated.
Puget Sound Energy | March 5, 2026 Page 13
File No. 9186-184- 00 Task 2032
Please refer to Appendix C, Report Limitations and Guidelines for Use for additional information pertaining
to use of this report.
9.0 References
City of Renton (COR) 2024a. COR Map Viewer Interactive mapping tool. Accessed October 10, 2024 from
COR Maps | City of Renton (rentonwa.gov).
City of Renton (COR) 2024b. Preapplication Meeting For PSE SWARR Station – Security Perimeter
Maintenance, 2100 Benson DR S (APN 2023059071, PRE-24-000335. November 21, 2024.
City of Renton Municipal Code (RMC) 4-3-050. Accessed October 10, 2024 from City of Renton Municipal
Code.
City of Renton Surface Water Design Manual (RSWDM). 2022. Accessed October 10, 2024 from City of
Renton Surface Water Design Standards.
GeoEngineers, Inc. (GeoEngineers) 2025a. Geotechnical Design Memorandum, SWARR Station – Security
Perimeter Maintenance Project. 2100 Benson Drive South, Renton, Washington. Prepared for
Puget Sound Energy and dated October 7, 2025. GEI File No. 9186-184-00 Task 2032.
GeoEngineers, Inc. (GeoEngineers) 2025b. Stream Assessment at the SWARR Station. Prepared for Puget
Sound Energy and dated December 9, 2025. GEI File No. 9186-184-00 Task 2032.
GeoEngineers, Inc. (GeoEngineers). 2011. September 2010 and March 2011 Groundwater Monitoring
Report, Swarr Station, Renton Washington for Puget Sound Energy dated July 18, 2011. GEI File
No. 0186-596-01.
King County (KC) 2024. King County iMap; Interactive mapping tool. Accessed October 10, 2024 from
https://kingcounty.gov/services/gis/Maps/imap.aspx.
Mullineaux, D.R. 1965. Geologic map of the Renton quadrangle, King County, Washington; 1:24,000-scale;
United States Geological Survey Map GQ-405; 1965; Accessed October 10, 2024 from NGMDB
Product Description Page (usgs.gov). June 13, 2023.
Office of Surface Mining Reclamation and Enforcement (OSMRE 2024). Accessed on October 25, 2024
from OSMRE Home Page.
Schuster, J.E., Cabibbo, A.A., Schilter, J.F., and Hubert, I.J. 2015. Geologic Map of the Tacoma 1:100,000-
scale quadrangle, Washington: Washington Division of Geology and Earth Resources Map Series
2015-03.
United States Department of Agriculture-National Resources Conservation Service (UDSA-NRCS). 2024.
Accessed October 10, 2024 from Web Soil Survey - Home (usda.gov).
Washington State Department of Ecology Well Report Viewer (Ecology). 2024. Accessed October 10, 2024
from Well Report Search Options.
Puget Sound Energy | March 5, 2026 Page 14
File No. 9186-184- 00 Task 2032
Washington State Department of Natural Resources (DNR) Geologic Information Portal. 2024a. Accessed
October 10, 2024 from Washington Geologic Information Portal.
Washington State Department of Natural Resources (DNR) Light Detection and Ranging (LiDAR) Data
Portal. 2024b. Accessed October 10, 2024 from http://lidarportal.dnr.wa.gov/.
Questions regarding the information provided in this letter report should be directed to Carla Woodworth
425.861.6012 or Brian Ranney at 503.603.6675.
Sincerely,
GeoEngineers, Inc.
Carla R. Woodworth, LG
Project Geologist
Brian C. Ranney, LG, LEG
Principal Engineering Geologist
CRW:BCR:kjb
Attachments:
Figure 1. Vicinity Map
Figure 2. Fence Replacement Site Plan
Figure 3. Geology
Figure 4. Soils and Erosion Hazards
Figure 5. Regulated Slopes
Figure 6. Coal Mine Hazards
Figure 7. Landslide Severity
Figure 8. Lidar Interpretation
Appendix A. Site Plan and Groundwater Elevations – March 2011
Figure A-1. Site Plan
Figure A-2. Groundwater Elevations – March 2011
Appendix B. Site Photographs
Appendix C. Report Limitations and Guidelines for Use
Disclaimer: Any electronic form, facsimile, or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy
of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
EXP. 02/09/2027
Brian C. Ranney Digitally signed by Brian C. Ranney
Date: 2026.03.05 08:40:18 -08'00'
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Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
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Notes:
1. No changes to parking or new buildings proposed
Source(s):• Drawing updated with proposed fence alignment 10/3/24.• Streams and critical areas obtained from City of Renton GIS, http://rentonwa.gov/government/.• Roads, 2015 aerial, contours and parcel boundaries from King County GIS. http://www.kingcounty.gov/services/gis.aspxCoordinate System: NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figure for any other project or purpose shall be at the user's sole risk and without liability toGeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of thefigure, or data contained therein. The file containing this figure is a copy of a master document, the original of which is retained by GeoEngineers and is the official document ofrecord.
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s
o
n
R
d
S
S
P
u
g
e
t
D
r
S Puget Dr
EagleRidge
DrS S
18thSt
Eagl
e
Ln
S
Eag
le
Ln
S
E
agle
Ln
S
Eagle L n S
Eag
l
e
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
rWells
Ct
S
S 22 n d Ct
B
e
n
s
o
n
R
d
S
Victoria Hills
S
2
3
r
d
S
t
A
C
D
Grant A v e S
Tho
m
a
s
Ln
Thomas
L
n
S
Puget
Dr
D
D
D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDD
D
D
DD
D
D
D
D
D
D
D
D
D
D
D
D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DDDDD
Qsr
af
Tr
Qis
Qgt
Tr
Geology
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 3
1
0 300
Feet
Legend
Site
Parcel Boundary King County)
D Rebuild Fence - Approximate Location
(2,133.3 feet)
D Existing Fence (2,976.8 feet)
Geologic Units (DNR 24k)
Qgt - Pleistocene continental glacial till
Qis - Pleistocene continental glacial drift
Qsr - Pleistocene continental glacial drift
Tr - Tertiary sedimentary rocks and
deposits
af - Holocene artificial fill and modified
land
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F03_Geology Date Exported: 12/18/24 by glohrmeyer
Source(s):• Geology from Wa Dept of Natural Resources, 24k• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Morris
Ave
S
Morris
Ave
S
Smithers
Ave
S
Whitworth
Ave
S
S
P
u
g
e
t
D
r
S 1 4 t h S t
S 15th St
Talbot
Rd
S
Benso
n
Dr
S
Morris
Ave
S
TalbotRdS
S 17th St
S 19th St
S 16th St
S 20th St
Benson
Dr
S
Talbot Hill
Reservoir Park
Talbot Hill
191 ft S 23rd St S 23rd St
TalbotR d S
Smithers
Ave
S
S 21st St
Bens
on
Dr
S
Thomas
Teasdale Park
GenCare
Lifestyle
Renton at The
Lodge at Eagle
Ridge
A Block
E a gle RidgeDr
S
S Eagle Ridge Dr
S
18th
St
S
P
u
g
e
t
D
r
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
r
S Puget Dr
E agleRidge
Dr
S S18thSt
Eagl
e
Ln
S
Eagle
Ln
S
E
agle
Ln
S
Eagle L n S
Eagle
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
rWells
Ct
S
S 22 n d Ct
B
e
n
s
o
n
R
d
S
Victoria Hills
A
C
D E
Grant Av e S
Tho
m
a
s
Ln
Grant
Ave
S
Thomas
L
n
S
Puget
Dr
D
D
D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDD
D
DDD
D
D
D
D
D
D
D
D
D
D
D
D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DDDDD
Beausite gravelly
sandy loam, 15 to
30 percent slopes
Urban land
Alderwood gravelly
sandy loam, 8 to15 percent slopes
Alderwood gravelly
sandy loam, 15 to30 percent slopes
Alderwood gravellysandy loam, 15 to
30 percent slopes
Beausite gravelly
sandy loam, 6 to15 percent slopes
Soils and Erosion Hazards
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 4
1
0 300
Feet
Legend
Site
Parcel Boundary King County)
D D Rebuild Fence - Approximate
Location (2,133.3 feet)
D D Existing Fence (2,976.8 feet)
High Erosion Hazard (City of Renton)
Soil Unit Erosion Hazard
Not rated
Moderate
Severe
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F04_SoilErosion Date Exported: 12/18/24 by glohrmeyer
Source(s):• Soils from NRCS• High Erosion Hazard from City of Renton• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Morris
Ave
S
Morris
Ave
S
Smithers
Ave
S
Whitworth
Ave
S
S
P
u
g
e
t
D
r
S 1 4 t h S t
S 15th St
Talbot
Rd
S
Benso
n
Dr
S
Morris
Ave
S
TalbotRdS
S 17th St
S 19th St
S 16th St
S 20th St
Benson
Dr
S
Talbot Hill
Reservoir Park
Talbot Hill
191 ft S 23rd St S 23rd St
TalbotR d S
Smithers
Ave
S
S 21st St
Bens
on
Dr
S
Thomas
Teasdale Park
GenCare
Lifestyle
Renton at The
Lodge at Eagle
Ridge
A Block
E a gle RidgeDr
S
S Eagle Ridge Dr
S
18th
St
S
P
u
g
e
t
D
r
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
r
S Puget Dr
E agleRidge
Dr
S S18thSt
Eagl
e
Ln
S
Eagle
Ln
S
E
agle
Ln
S
Eagle L n S
Eagle
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
rWells
Ct
S
S 22 n d Ct
B
e
n
s
o
n
R
d
S
Victoria Hills
A
C
D E
Grant Av e S
Tho
m
a
s
Ln
Grant
Ave
S
Thomas
L
n
S
Puget
Dr
D
D
D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDD
D
DDD
D
D
D
D
D
D
D
D
D
D
D
D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DDDDD
Regulated Slopes
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 5
1
0 300
Feet
Legend
Site
Parcel Boundary (King County)
D Rebuild Fence - Approximate Location
(2,133.3 feet)
D Existing Fence (2,976.8 feet)
Slope (City of Renton, Percent)
>15% & <=25%
>25% & <=40% (Sensitive)
>40% & <=90% (Protected)
>90% (Protected)
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F05_RegulatedSlopes Date Exported: 12/18/24 by glohrmeyer
Source(s):• Slope data from City of Renton• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Morris
Ave
S
Morris
Ave
S
Smithers
Ave
S
Whitworth
Ave
S
S
P
u
g
e
t
D
r
S 1 4 t h S t
S 15th St
Talbot
Rd
S
Benso
n
Dr
S
Morris
Ave
S
TalbotRdS
S 17th St
S 19th St
S 16th St
S 20th St
Benson
Dr
S
Talbot Hill
Reservoir Park
Talbot Hill
191 ft S 23rd St S 23rd St
TalbotR d S
Smithers
Ave
S
S 21st St
Bens
on
Dr
S
Thomas
Teasdale Park
GenCare
Lifestyle
Renton at The
Lodge at Eagle
Ridge
A Block
E a gle RidgeDr
S
S Eagle Ridge Dr
S
18th
St
S
P
u
g
e
t
D
r
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
r
S Puget Dr
E agleRidge
Dr
S S18thSt
Eagl
e
Ln
S
Eagle
Ln
S
E
agle
Ln
S
Eagle L n S
Eagle
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
rWells
Ct
S
S 22 n d Ct
B
e
n
s
o
n
R
d
S
Victoria Hills
A
C
D E
Grant Av e S
Tho
m
a
s
Ln
Grant
Ave
S
Thomas
L
n
S
Puget
Dr
D
D
D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDD
D
DDD
D
D
D
D
D
D
D
D
D
D
D
D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DDDDD
Coal Mine Hazards
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 6
1
0 300
Feet
Legend
Site
Parcel Boundary (King County)
D Rebuild Fence - Approximate Location
(2,133.3 feet)
D Existing Fence (2,976.8 feet)
Coalmine Hazards (City of Renton)
Severity
High
Moderate
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F06_CoalMineHazards Date Exported: 12/18/24 by glohrmeyer
Source(s):• Coalmine data from City of Renton• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Morris
Ave
S
Morris
Ave
S
Smithers
Ave
S
Whitworth
Ave
S
S
P
u
g
e
t
D
r
S 1 4 t h S t
S 15th St
Talbot
Rd
S
Benso
n
Dr
S
Morris
Ave
S
TalbotRdS
S 17th St
S 19th St
S 16th St
S 20th St
Benson
Dr
S
Talbot Hill
Reservoir Park
Talbot Hill
191 ft S 23rd St S 23rd St
TalbotR d S
Smithers
Ave
S
S 21st St
Bens
on
Dr
S
Thomas
Teasdale Park
GenCare
Lifestyle
Renton at The
Lodge at Eagle
Ridge
A Block
E a gle RidgeDr
S
S Eagle Ridge Dr
S
18th
St
S
P
u
g
e
t
D
r
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
r
S Puget Dr
E agleRidge
Dr
S S18thSt
Eagl
e
Ln
S
Eagle
Ln
S
E
agle
Ln
S
Eagle L n S
Eagle
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
rWells
Ct
S
S 22 n d Ct
B
e
n
s
o
n
R
d
S
Victoria Hills
A
C
D E
Grant Av e S
Tho
m
a
s
Ln
Grant
Ave
S
Thomas
L
n
S
Puget
Dr
D
D
D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDD
D
DDD
D
D
D
D
D
D
D
D
D
D
D
D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DDDDD
Landslide Severity
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 7
1
0 300
Feet
Legend
Site
Parcel Boundary (King County)
D D Rebuild Fence - Approximate Location
(2,133.3 feet)
D D Existing Fence (2,976.8 feet)
Landslide Severity (City of Renton)
High
Moderate
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F07_LandslideSeverity Date Exported: 12/18/24 by glohrmeyer
Source(s):• Landslide data from City of Renton• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Ta
l
b
ot
Rd
S
S
P
u
g
e
t
D
r
Be
n
s
on
D
r
S
204 ft
Ta
l
b
o
t
Rd
S
S 16th St
Be
ns
o
n
D
r
S
Talbot Hill
Reservoir Park
S 21st St
Willia
m
s
A
ve
S
Be
ns
o
n
D
r
S
Altitude
Apartments
Eag
l
e
Ridg
eDr
S
S
1
8
t
h
S
t
S
P
u
g
e
t
D
r
S
P
u
g
e
t
D
r
S Puget
D
r
Eag
le
Rid
g
e
D
r
S
S
1
8th
S
t
Ea
g
l
e
L
n
S
Eag
l
e
Ln
S
E
ag
l
e
L
n
S
E
a
gle
Ln
S
Eagle
Ln
S
Ea
g
l
e
L
n
S
B
e
n
s
o
n
R
d
S
S
P
u
g
e
t
D
r
Wel
l
s
C
t
S
S
2
2
n d Ct
B
e
n
s
o
n
R
d
S
D
D
D D D D D D
D
D
D
D
D
D
D
D
D
D
D
DD
D
D
D
D
D
D
D
D
D
D
DDDDDDDDDDDDDDD
D
D D
DDD
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D D D D D D D D D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
DDDDDDD
32
0
31
0
300290
28
0
27
0
26
0
2
0
24
0
22
0
21
0
20
0
18
0
17
0
16
0
1
0
1
4
0
13
0
34
033
0
32
0
310
22
0
210
200
110
100
210
200
33
0
23
0
190
12
0
3
0
2
6
0
90
3
3
0
290
280
23
0
1
8
0
13
0
13
0
8
0
Lidar Interpretation
Puget Sound Energy
SWARR Station - Security Perimeter Maintenance Project
Renton, Washington
Figure 8
1
0 200
Feet
Legend
Site
Parcel Boundary (King County)
D D Rebuild Fence - Approximate Location
(2,133.3 feet)
D D Existing Fence (2,976.8 feet)
2-foot Contour
10-foot Contour
P:\9\9186184\GIS\9186184_2024_Q4\9186184_2024_Q4.aprx\918618400tsk2032_F08_LidarInterpretation Date Exported: 12/18/24 by glohrmeyer
Source(s):• Topography from King County Lidar, 2021• Parcels from King County• Basemap from ESRI
Coordinate System: NAD 1983 StatePlane Washington North FIPS 4601 Feet
Disclaimer: This figure was created for a specific purpose and project. Any use of this figurefor any other project or purpose shall be at the user's sole risk and without liability to GeoEngineers.
The locations of features shown may be approximate. GeoEngineers makes no warranty or
representation as to the accuracy, completeness, or suitability of the figure, or data containedtherein. The file containing this figure is a copy of a master document, the original of which isretained by GeoEngineers and is the official document of record.
Appendices
Appendix A
Site Plan and Groundwater Elevations – March 2011
MW-3
MW-4
MW-2
PUGET SOUND
ENERGY PROPERTY
MW-10
MW-8
MW-9
MW-7
MW-1
MW-5
Below Ground
Above & Below Ground
Culvert
Above Ground
Monitoring WellMW-1
Reference: Drawing entitled "Swarr Station, Drainage Plan" dated 04/01/03, by Standby Systems Inc.
discussed in a related document.
2. This drawing is for information purposes. It is intended to assist in the identification of features
1. The locations of all features shown are approximate.
Notes:
Figure A-1
Site Plan
PSE
Swarr Station
W
E
N
Legend
Feet
Facility Boundary
Aboveground Storage Tank
HIGHWAY 515 - BENSON DRIVE SOUTH
Below Ground
Above & Below Ground
Culvert
Above Ground
Reference: Drawing entitled "Swarr Station, Drainage Plan" dated 04/01/03, by Standby Systems Inc.
document.
2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached
1. The locations of all features shown are approximate.
Notes:
Figure A-2
Groundwater Elevations - March 2011
PSE
Swarr Station
Feet
Legend
Monitoring Well
Groundwater Contour (03/23/11)
Groundwater Elevation (03/23/11)
Groundwater Flow Direction
Appendix B
Site Photographs
Figure B-1
Site Photographs
September 12, 2024
Photograph 1. At site entrance gate, looking east along entrance driveway and area to south of driveway.
Photograph 2. At site entrance gate, looking south along entrance driveway and area to south of driveway.
Puget Sound Energy
SWARR Station
Renton, Washington
91
8
6
-18
4
-00
T
a
s
k
2
0
3
2
D
a
t
e
E
x
p
o
r
t
e
d
:
1
0
/
1
4
/
2
0
2
4
C
R
W
Disclaimer: This figure was created for a specific purpose and project. Any
use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Residential Properties
Site Entrance Driveway
Figure B-2
Site Photographs
September 12, 2024
Photograph 3. At site entrance gate, looking north towards proposed fence location and area to north of driveway.
Photograph 4. At site entrance gate, looking east along entrance driveway and area to north of driveway.
91
8
6
-18
4
-00
T
a
s
k
2
0
3
2
D
a
t
e
E
x
p
o
r
t
e
d
:
1
0
/
1
4
/
2
0
2
4
C
R
W
Disclaimer: This figure was created for a specific purpose and project. Any
use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Existing Fence Line
Benson Drive South
Proposed Fence Line
Site Entrance Driveway
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-3
Site Photographs
September 12, 2024
Photograph 5. East of site entrance gate, looking east towards east slopes, existing and proposed fence location and Rolling Hills Creek.
Photograph 6. Rolling Hills Creek, looking south towards Rolling Hills Creek, culvert under site and outfall from South Puget Drive .
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risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Site Entrance Driveway and Shoulder
Existing Fence Line
Rolling Hills Creek
Outfall Flow Channel and standing
water from South Puget Drive
Rolling Hills Creek
Culvert Conveying
Rolling Hills Creek
under Project Site
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-4
Site Photographs
September 12, 2024
Photograph 7. On east side of site, looking north along driveway.
Photograph 8. Northeast side of site, looking north along driveway.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Site entrance driveway
and shoulder
Slope drain outlet
Proposed fence line
Culvert that conveys
stormwater to north side of site
Proposed fence line
Existing fence line
Half-round culvert and
flow direction
Half-round culvert and
flow direction
Slope up to South Puget Drive
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-5
Site Photographs
September 12, 2024
Photograph 9. Along east side of driveway, looking east towards South Puget Drive.
Photograph 10. Slope drain and half-round culvert along east side of driveway, looking southeast towards slope.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
South Puget Drive
Existing Fence Line
Slope drain from South
Puget Drive
Half-round culvert and
flow direction
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-6
Site Photographs
September 12, 2024
Photograph 11. Near north end of site looking south.
Photograph 12. Near north end of site looking southeast up slope towards South Puget Drive.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Half-round culvert
Site Entrance Driveway and Parking Area
Slope drain from
South Puget Drive
South Puget Drive
Existing fence line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-7
Site Photographs
September 12, 2024
Photograph 13. Looking west along fence line on north side of site towards Benson Drive South.
Photograph 14. Fence line along north of site at area of erosion near Rolling Hills Creek and surface water erosion looking north.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Benson Drive South
Existing Fence Line
Erosion at Rolling Hills
Creek and swale outlet
Existing Fence Line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-8
Site Photographs
September 12, 2024
Photograph 15. At northeast corner of the building, looking south.
Photograph 16. North of site entrance gate, looking west towards Benson Drive South and area to north of driveway.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Building
Benson Drive South
Swale and flow direction
Proposed Fence LineDitch line
Swale
Existing Fence Line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-9
Site Photographs
September 12, 2024
Photograph 17. At west side of site, looking southwest along fence line towards slope and Benson Drive South.
Photograph 18. On west side of building, looking south along proposed fence line location.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Benson Drive South
Existing Fence Line
Benson Drive South
Proposed Fence Line
2- to 3-foot-high rock wall and concrete
ditch line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-10
Site Photographs
September 12, 2024
Photograph 19. On west side of site structures, looking south along proposed fence line and rock wall.
Photograph 20. Southeast corner of site facility, looking west towards Benson Drive South.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
2- to 3-foot-high rock
wall and concrete ditch
line and catch basin
Proposed Fence Line
2- to 3-foot-high rock wall
and concrete ditch line
Proposed Fence Line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-11
Site Photographs
September 12, 2024
Photograph 21. At site entrance gate, looking northwest towards Benson Drive South, existing and proposed fence location and area to north of driveway.
Photograph 22. North of site entrance gate, looking west towards Benson Drive South and area to north of driveway.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Benson Drive South
Site Entrance Driveway Shoulder
Existing Fence Line
Benson Drive South
Existing Fence Line
Proposed Fence Line
Site Entrance Driveway
Proposed Fence Line
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-12
Site Photographs
September 12, 2024
Photograph 23. At northwest corner of site, looking west towards slope up to Benson Drive South
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Existing Fence Line
Sediment and organic material captured behind fence
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-13
Site Photographs
September 12, 2024
Photograph 24. At gravel walkway to building, looking south along parking area and concrete swale.
Photograph 25. At gravel walkway to building, looking northwest towards underground tank area north of building and along concrete swale.
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use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Site driveway and
parking area
Existing Fence Line
Concrete drainage swale
and flow direction
Benson Drive South
Concrete drainage swale
Puget Sound Energy
SWARR Station
Renton, Washington
Figure B-14
Site Photographs
September 12, 2024
Photograph 26. At southeast corner of Project area, looking west towards Benson Drive South along site entrance driveway and Rolling Hills Creek.
Photograph 27. At southeast corner of Project area and Rolling Hills Creek, looking east towards overflow half round.
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Disclaimer: This figure was created for a specific purpose and project. Any
use of this figure for any other project or purpose shall be at the user's sole
risk and without liability to GeoEngineers. The locations of features shown may be approximate. GeoEngineers makes no warranty or representation as to the accuracy, completeness, or suitability of the figure, or data contained therein. The file containing this figure is a copy of a master
document, the original of which is retained by GeoEngineers and is the
official document of record.
Benson Drive South
Site Entrance Driveway
Rolling Hills Creek
and culvert inlet
Proposed Fence Line
Existing fence line
Overflow half-round
Rolling Hills Creek
and culvert inlet
Puget Sound Energy
SWARR Station
Renton, Washington
Appendix C
Report Limitations and Guidelines for Use
Puget Sound Energy | March 5, 2026 Page C-1
File No. 9186-184-00 Task 2032
Appendix C
Report Limitations and Guidelines for Use1
This appendix provides information to help you manage your risks with respect to the use of this report.
REPORT USE AND RELIANCE
This report has been prepared for Puget Sound Energy. GeoEngineers structures its services to meet the
specific needs of its clients. No party other than Puget Sound Energy may rely on the product of our services
unless we agree to such reliance in advance and in writing. Within the limitations of the agreed scope of
services for the project, and its schedule and budget, our services have been executed in general
accordance with the Statement of Work #CW2263712, our Master Services Agreement with the Client
# CW2233188 dated November 18, 2014, and generally accepted geotechnical practices in this area at
the time this report was prepared. We do not authorize, and will not be responsible for, the use of this report
for any purposes or projects other than those identified in this report.
If changes to the project or property occur after the date of this report, GeoEngineers cannot be responsible
for any consequences of such changes in relation to this report unless we have been given the opportunity
to review our interpretations and recommendations in the context of such changes. Based on that review,
we can provide written modifications or confirmation, as appropriate.
INFORMATION PROVIDED BY OTHERS
GeoEngineers has relied upon certain data or information provided or compiled by others in the
performance of our services. Although we use sources that we reasonably believe to be trustworthy,
GeoEngineers cannot warrant or guarantee the accuracy or completeness of information provided or
compiled by others.
CONDITIONS CAN CHANGE
This report is based on conditions that existed at the time the study was performed. The findings and
conclusions of this report may be affected by the passage of time, by events such as construction on or
adjacent to the site, new information or technology that becomes available subsequent to the report date,
or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. If more than
a few months have passed since issuance of our report or work product, or if any of the described events
may have occurred, please contact GeoEngineers before applying this report for its intended purpose so
that we may evaluate whether changed conditions affect the continued reliability or applicability of our
conclusions and recommendations.
PROFESSIONAL JUDGMENT
It is important to recognize that the geoscience practices (geotechnical engineering, geology, and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org.
Puget Sound Energy | March 5, 2026 Page C-2
File No. 9186-184-00 Task 2032
To help clients better understand how this difference pertains to its services, GeoEngineers includes these
explanatory “limitations” provisions in its reports. Please confer with GeoEngineers if you need to know how
these “Report Limitations and Guidelines for Use” apply to your Project or site.
APPENDIX E
CONSTRUCTION STORMWATER POLLUTION
PREVENTION PLAN
Construction Stormwater Pollution
Prevention Plan
SWARR Security Maintenance Project
Renton, King County, Washington
for
Puget Sound Energy
April 22, 2026
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.861.6000
Construction Stormwater Pollution Prevention and
Spill Control Plan (CSWPPS)
For
SWARR Security Maintenance Project
Renton, King County, Washington
Prepared for:
Puget Sound Energy
Permittee/Owner Developer Operator/Contractor
Kathryn Hodges and Elaine Babby
Puget Sound Energy
Puget Sound Energy
TBD
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
Carla Woodworth GeoEngineers, Inc.
425.466.6772
Other CESCLs to be identified as needed
CSWPPS Original Preparation Date
April 22, 2026
Approximate Project Construction Dates
(Target Dates for Planning Purposes, Subject to Revision)
Construction Phase/Activity Target Dates
Install TESC/BMPs June 2026
Tree and Shrub Cutting June 2026
Begin Maintenance and Repairs June 2026
Complete Maintenance and Repairs September 2026
Site Restoration and Remove TESC/BMPs September 2026
Construction Stormwater Pollution Prevention and Spill Control Plan
SWARR Security Maintenance Project
Renton, King County, Washington
File No. 9186-184-00 Task 2032
April 22, 2026
Prepared for:
Puget Sound Energy
PO Box 97034 M/S EST-04W
Bellevue, Washington 98009-9734
Attention: Kathryn Hodges and Elaine Babby
Prepared by:
GeoEngineers, Inc.
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.861.6000
Carla Woodworth, LG, CESCL No. 81954 Brian C. Ranney, LEG, CESCL No. 82900
Project Geologist Principal Engineering Geologist
CRW:BCR:kjb:tlm
Disclaimer: Any electronic form, facsimile, or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
Puget Sound Energy | April 22, 2026 i
File No. 9186-184-00 Task 2032
Table of Contents
1.0 Project Information ................................................................................................................... 1
2.0 Existing Conditions .................................................................................................................... 2
2.1 Site Topography and Drainage ................................................................................................................... 2
2.2 Drainage conditions .................................................................................................................................... 2
2.3 Existing Vegetation ..................................................................................................................................... 3
2.4 Soil Conditions and Erodibility .................................................................................................................... 3
2.5 Critical Areas ............................................................................................................................................... 3
2.6 Known Impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the Receiving
Waterbodies ......................................................................................................................................................... 4
3.0 Planned Construction Activities ................................................................................................. 4
4.0 Construction Stormwater BMPs ................................................................................................. 5
4.1 BMP Elements ............................................................................................................................................. 5
4.1.1 Element No. 1: Clearing Limits ....................................................................................................... 5
4.1.2 Element 2: Cover Measures ........................................................................................................... 6
4.1.3 Element No. 3: Perimeter Protection ............................................................................................. 6
4.1.4 Element No. 4: Traffic Area Stabilization ....................................................................................... 7
4.1.5 Element No. 5: Sediment Retention ............................................................................................... 7
4.1.6 Element No. 6: Surface Water Collection ....................................................................................... 8
4.1.7 Element No. 7: Dewatering Control ................................................................................................ 8
4.1.8 Element No. 8: Dust Control ........................................................................................................... 9
4.1.9 Element No. 9. Flow Control ........................................................................................................... 9
4.1.10 Element 10: Control Pollutants ................................................................................................... 10
4.1.11 Element No. 11: Protect Existing and Proposed Flow Control BMPs ........................................ 11
4.1.12 Element No. 12: Maintain BMPs ................................................................................................. 12
4.1.13 Element No. 13: Manage the Project .......................................................................................... 12
5.0 Construction Schedule and BMP Implementation .................................................................... 13
6.0 Pollution Prevention Team ....................................................................................................... 13
6.1 Roles and Responsibilities ...................................................................................................................... 13
6.2 Team Members ........................................................................................................................................ 14
6.3 Spill and Release Response .................................................................................................................... 14
7.0 Site Observation ...................................................................................................................... 14
7.1 Stormwater Turbidity Observation .......................................................................................................... 15
7.2 pH .............................................................................................................................................................. 15
8.0 Recordkeeping ........................................................................................................................ 15
8.1 Access to Plans and Records .................................................................................................................. 15
8.2 Updating the Construction Stormwater Pollution Prevention Plan ....................................................... 16
9.0 References .............................................................................................................................. 16
Puget Sound Energy | April 22, 2026 ii
File No. 9186-184-00 Task 2032
Appendices
Appendix A. Temporary Erosion and Sediment Control Plan (Completed by others)
Appendix B. Construction Stormwater BMPs
Puget Sound Energy | April 22, 2026 Page 1
File No. 9186-184-00 Task 2032
1.0 Project Information
Puget Sound Energy (PSE) plans to improve reliability and safety at the SWARR Station by maintaining and
replacing existing fencing. The maintenance and repairs will be completed on PSE-owned Parcel
No. 2023059071 located at 2100 Benson Drive South in Renton, King County, Washington. The property
is situated within Section 20 of Township 23 North and Range 05 East of the Willamette Meridian (WM).
The project will be completed within the southern developed 5 acres on an approximately 16.71-acre
parcel. The station and project vicinity are shown in the Cover Sheet Drawing G001 of the Temporary
Erosion and Sediment Control (TESC) plans in Appendix A, Temporary Erosion and Sediment Control Plan.
PSE is proposing to replace the existing 6-foot-tall chain link fence around the SWARR Station with a new
8- to 12-foot-tall metal mesh fence including intrusion detection and security cameras to meet new
Homeland Security requirements and PSE standards. PSE also plans to replace the vehicle and pedestrian
gates at the main entrance to Benson Drive South in the southwest corner of the site and at the back
entrance to South Puget Drive in the northeast corner of the site. The replacement fence alignment will
generally follow existing fence alignment, with some segments shifting further into developed areas. The
fence will not move outward away from the developed station footprint. New security cameras to be
installed will require the installation of an electrical system and conduit. Conduits will be attached to the
fence, to minimize trenching, except at gate crossings and between power source at control building and
fence where conduits will be routed below ground. Minor grading or excavation, including augering or
hydrovactoring, for fence and camera post installation, is proposed as part of the project.
Vegetation management will be required to accomplish the project, including cutting and removing 42 dead
or dying trees and 17 healthy trees and trimming approximately 430 square feet of evergreen and
deciduous shrubs along the north, east and west sides of the station fence alignment to allow for
installation of the new fence.
Land disturbing activities will be required to complete site security maintenance activities. Land
disturbance will include 3,200 square feet of temporary impact including brush and tree cutting for the
fence alignment, excavation for the fence posts and excavations for the installation of the new underground
conduit for some of the electrical system adjustments. Site restoration will be completed as soon as
practical after construction activities are completed. Site restoration will include backfilling excavations,
regrading workspaces to preconstruction conditions, if needed, and placing crushed rock, gravel, or asphalt
or grass seed and mulch in disturbed areas to match preconstruction site conditions. Areas where trees
and shrubs have been cut will be restored with mulch. The root systems of the cut trees and shrubs will be
left intact. Planned construction activities are discussed in more detail in Section 3.0 Planned Construction
Activities.
The proposed area of excavation for the fence posts and new conduit is approximately 1,520 square feet
(less than 0.035 acres). The proposed quantity of temporary excavation cut, and fill is approximately
127 cubic yards (excavations will be approximately 18 to 45 inches deep); however, there will be no net
change in surface elevation as the materials removed from the excavations will be hauled off site for
disposal. No buildings and no new impervious surface are proposed for the project.
Puget Sound Energy | April 22, 2026 Page 2
File No. 9186-184-00 Task 2032
This Construction Stormwater Pollution Prevention Plan (CSWPPP) was prepared to meet the City of Renton
(COR) Targeted Drainage Review (Category 2) Core Requirement No. 5, Construction Stormwater Prevention
so that the project complies with the City of Renton Surface Water Design Manual (RSWDM).
2.0 Existing Conditions
2.1 SITE TOPOGRAPHY AND DRAINAGE
The project site is situated in the southern portion of the parcel which is located in a northwest-southeast
trending drainage of Rolling Hills Creek. The site is situated on a relatively flat to very gently sloping (slope
gradients of 0 to 15 percent) ground surface. The developed portion of the site is bounded by a gently
sloping (slope gradients between 5 and 15 percent) forested area to the north, by steep slopes (slope
gradients ranging between 40 to 65 percent) up to South Puget Drive and businesses to the east, by gentle
slopes (slope gradients between 5 and 20 percent) down to single-family residential developments to the
south, and to the west by steep slopes (slope gradients ranging between 40 to 70 percent) up to Benson
Drive South.
When the station was built in the 1960s, the site was graded to provide a relatively flat to gently sloping
ground surface between approximately Elevation 160 above mean sea level (MSL) to approximately
150 feet MSL from south to north. The project area is approximately 10 to 30 feet lower in elevation than
Benson Drive South on the west side of the site and between approximately 50 and 90 feet lower in
elevation than South Puget Drive on the east.
2.2 DRAINAGE CONDITIONS
Based on our review of information available from COR Maps (COR 2024), the site is within the COR Flow
Control Duration Standard (matching forested conditions) and within the Black River drainage basin. The
project does not contain or is not adjacent to an aquifer protection area. Land use in the area includes
residential development zone R-8.
According to the COR Utility Geographic Information System (GIS) data (COR 2024a), there are multiple
stormwater discharge points that direct water towards the SWARR Station parcel. Surface water along
Benson Drive South collects within curbside gutters and enters three catch basins located on the east side
of Benson Drive South adjacent to the west side of the project parcel. Stormwater along this portion of
Benson Drive South as well as stormwater from the north side of Benson Drive South, South 21st Street
and South 19th Street enters the stormwater drain system and discharges onto PSE’s property at a point
outside of the northwest corner of the proposed work area. Evidence of water sheet flow (fine sediments,
organic matter accumulation) has been observed from the discharge point that flows northeast through the
northwest corner of the existing fence line towards Rolling Hills Creek. This sheet flow either infiltrates or
eventually flows into Rolling Hills Creek.
On the east side of the project site, surface water along South Puget Drive adjacent to the site is collected
within curbside gutters and enters two catch basins located on the east and west sides of South Puget
Drive. Water in the east catch basins flows directly to the catch basins on the west side of South Puget
Drive which discharges stormwater onto the slopes on the east side of the project area. Plastic piping has
been installed on the site slopes to capture the discharged water and transport it to the base of the slopes.
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Based on our surface reconnaissance, the water then flows into the half-rounds that have been installed
on the east side of the site access road to convey the water along the toe of the slopes to the northeast
corner of the site where the water flows into an existing catch basin and then discharges to Rolling Hills
Creek on the north side of the developed site.
Surface water near the intersection of South Puget Drive and Benson Road South enters a series of catch
basins located near the intersection. This water then flows through the stormwater drain system and
discharges to the slopes southeast of the project area into a tributary that directs flow westward towards
Rolling Hills Creek. However, due to natural topography, water does not directly enter the stream and
evidence of standing water was observed just east of the south portion of the site where Rolling Hills Creek
enters the culvert.
According to COR, Rolling Hills Creek is mapped as an open channel on the north and south sides of the
project area. The creek flows into the culvert inlet at the south end of the project site and discharges to an
open stream channel at the north end of the project site. The creek is located outside of the proposed work
areas and will not be disturbed by construction. All land disturbance will occur within or immediately
adjacent to the facilities, which are located in upland areas.
2.3 EXISTING VEGETATION
The site vicinity is a mixed-use area including a combination of residential areas with single-family homes
and apartment complexes, tennis courts and the PSE South Seattle Gate Station with associated
landscaping; as well as pockets of forested areas vegetated with conifer trees, evergreen shrub, and
deciduous trees and shrubs.
The existing facilities located near the center of the project site include a one-story metal sided building,
natural gas piping and aboveground storage tanks situated on a gravel surface. Existing underground
storage tank facilities are located on the north side of the project site where the ground surface is vegetated
with grass. The south side of the project site contains the main driveway into the site facilities and parking
area, east to west trending underground gas pipelines, forested habitat with little understory vegetation
and maintained grass areas. The northern portion of the parcel (outside of the fenced facility) is
undeveloped and forested with shrub understory. Slopes around the site are vegetated with evergreen and
deciduous trees and shrubs, blackberries, ivy, grass and other understory vegetation.
2.4 SOIL CONDITIONS AND ERODIBILITY
Based on soil information available from the National Resources Conservation Service (NRCS), the project
site is underlain by two general surficial soil units. The majority of the site is underlain by a soil unit referred
to as the Alderwood gravelly sandy loam, 15 to 30 percent slopes and is classified as having a severe
erosion hazard. The minor soil unit located along the western boundary of the project is referred to as the
Beausite gravelly sandy loam characterized by 6 to 15 percent slopes and is classified as having a moderate
erosion hazard. Potential erosion problems at the site during construction include turbid runoff from bare
soils at the work sites during precipitation events.
2.5 CRITICAL AREAS
The project is located adjacent to mapped potential erosion, regulated slope, landslide and coal mine
hazards, Rolling Hills Creek and within the critical area buffers of these features. TESC and best
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management practices (BMPs) will be implemented during the project to minimize impacts to critical areas.
Impacts to critical areas and buffers will be temporary. Excavations at the site will be shallow to minimize
the likelihood of impacts to areas with mapped coal mine hazards. Site conditions will be restored to
preconstruction contours, and pre-existing surface treatment, including gravel or paved surface conditions,
mulched where trees and ground cover are disturbed or mulched and reseeded where grass is removed.
2.6 KNOWN IMPAIRMENTS FOR 303(D) LISTED OR TOTAL MAXIMUM DAILY LOAD
(TMDL) FOR THE RECEIVING WATERBODIES
The receiving waterbodies for the project are Rolling Hills Creek, which eventually flows into Springbrook
Creek. Rolling Hills Creek (Listing ID 70148) was listed on Washington State Department of Ecology’s
(Ecology) 303(d) Water Quality Assessment for Washington as a Category 5 for the parameter of Benthic
Macroinvertebrates Bioassessments. The Green River Temperature TMDL is the approved TMDL within the
project area (Ecology 2025, Water Quality Atlas - Map ). The creek is culverted through the proposed work
areas and will not be disturbed by construction. All land disturbance will occur within or immediately
adjacent to the facilities in upland areas.
3.0 Planned Construction Activities
Construction will include tree and shrub cutting and trimming along portions of the proposed fence
alignment. Construction also will include installation of a new perimeter fence and security cameras and
associated electrical conduit and wiring. Restoration of all disturbed areas will occur once all construction
activities are completed. Minor concrete work is planned to back fill the fence and camera post hole
excavations and replacement of gate controller concrete pads which are about 2 feet by 2 feet in size. The
station will be accessed using existing public roads and the main station driveway.
The construction activities generally include the following:
■ Install TESC BMP measures prior to tree and brush cutting and land disturbing activities.
■ Mark trees and brush to be cut.
■ Cut and remove trees and brush from the proposed fence alignment.
■ Install mats or mulch to protect work areas within Critical Root Zone.
■ Complete camera conduit installation. Conduits will be attached to the fence, to minimize trenching,
except at gate crossings and between power source at control building and fence where a small
excavator will be used for trenching to install conduits below ground in locations where not attached to
the fence.
■ Complete fence post excavations using augering, vactoring or air spade methodologies.
■ Install fence and camera posts.
■ Backfill post holes using concrete to be flush with the existing ground surface.
■ Install camera wiring and fence.
■ Install culvert pipe where fence crosses ditch.
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■ Stabilize all excavation work areas and other disturbed ground surfaces with crushed rock, gravel or
asphalt, or with mulch and appropriate seed mixtures as appropriate.
■ Remove TESC BMPs when disturbed areas are stabilized.
We do not anticipate that perched groundwater will be encountered within shallow conduit and post
excavations for the project.
4.0 Construction Stormwater BMPs
The primary sources of turbid surface water runoff and potential sedimentation problems are likely to be
caused by equipment and vehicles tracking sediment from the work areas onto driveways and roadways.
In addition, erosion may occur from exposure of soils during conduit and post hole excavation and from
backfilling and grading along the work areas.
Straw wattles or compost socks, or equivalent, gravel surfacing and temporary ground protection mats will
be installed around the work areas to help keep turbid water within the work areas. Although dewatering is
not anticipated, if stormwater fills excavations, pumping may be required to periodically dewater the
excavations. This water will be pumped using temporary pumps. Turbid water will be discharged through
sediment bags onto vegetated ground surfaces more than 100 feet away from any surface water body or
regulated slope, landslide or erosion hazard area. Small check dams or straw or compost wattles also may
be placed on the vegetated surface downslope of the sediment bags, as needed, to slow discharge water.
Below is a list of elements of the CSWPPS that will be employed during construction that are intended to
reduce the likelihood of turbid stormwater discharging from the work areas. The proposed location of BMP
elements are shown in the TESC plans in Appendix A.
4.1 BMP ELEMENTS
According to the 2022 City of Renton Surface Water Design Manual – Appendix D (RSWDM), the project
will comply with the Erosion and Sediment Control (ESC) Elements No. 1 through No. 13 below. BMPs will
be implemented at the beginning of, inspected during and maintained throughout the duration of the
projects. Unless specified otherwise, the BMPs specified with numbers below are from the 2022 RSWDM.
BMPs are shown in the drawings in Appendix A. All temporary construction stormwater BMPs will be
removed after construction is complete and construction areas have been stabilized. Any accumulated
sediment will be removed after construction is complete or periodically during the construction activities if
sediment accumulation exceeds established depths or thicknesses.
BMPs relevant to the project are included in Appendix B, Construction Stormwater BMPs.
4.1.1 Element No. 1: Clearing Limits
To protect the adjacent properties and to reduce the area of soil exposed to construction, work will occur
within the limits of the existing security fence, which will provide security during construction of new fence
with exception of when entrance gate is replaced, then 24-7 security will be needed. Portions of the existing
fence will be removed after construction of new fence. Land disturbing activity will generally occur within
about 10 feet on each side of the new fence. Critical tree root zones will be protected with a 3-inch layer of
coarse arborist wood chips and/or construction mats. Additional details regarding tree and root protection
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is provided in the Swarr Station (Security Perimeter Maintenance) Arborist Report by Davey Resource
Group, Inc. dated 07/2024 (Updated 10/2025). Existing vegetation and native topsoil in the work areas
will be retained in an undisturbed state to the maximum extent possible. All construction limits and trees
to be protected are shown in the TESC sheets in Appendix A. The BMPs relevant to marking the clearing
limits and protecting trees that will be applied for this project include:
■ Clearing Limits (D.2.1.1)
■ Plastic or Metal Fence (BMP D.2.1.1.1)
■ Coarse Arborist Wood Chips
■ Construction mats
4.1.2 Element 2: Cover Measures
Exposed and unworked soils will be stabilized with the application of effective BMPs to prevent erosion
throughout the life of the project. This includes gravel, crushed rock and asphalt placement if the paved
portion of the driveway is disturbed; plastic covering; mulching; and temporary and permanent seeding.
The BMPs for cover measures that will be used on this project include:
■ Cover Measures (BMP D.2.1.2)
■ Mulching (BMP D.2.1.2.2)
■ Plastic Covering (BMP D.2.1.2.4)
■ Temporary and Permanent Seeding (BMP D.2.1.2.6)
■ Gravel, crushed rock and asphalt pavement restoration
The project site is located west of the Cascade Mountain Crest. As such, no soils will remain exposed and
unworked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet
season (October 1 to April 30). Regardless of the time of year, all soils will be stabilized at the end of the
shift, before a holiday or weekend, if needed, based on weather forecasts.
Excavated soil will be temporarily stockpiled onsite or loaded directly into trucks and transported to a
permitted off-site disposal facility.
Temporary and permanent gravel, rock and pavement restoration (if necessary), and mulch and seed
placement will be used once work has been completed. Dust control measures will be implemented in
accordance with the erosion and sediment control BMP presented in Section D.2.1.8 and Appendix B under
dry conditions during construction. Cover measures will be implemented at the beginning of, inspected
during and maintained throughout the duration of the project.
4.1.3 Element No. 3: Perimeter Protection
Straw wattles or compost socks will be the primary BMPs to filter sediment from sheet flow and reduce
erosion downstream of all disturbed areas during construction, if needed. A straw wattle will be placed
along the perimeter of Rolling Hills Creek to reduce the risk of runoff entering the creek during construction.
Check dams may also be used to reduce risk of runoff from the driveways if straw wattles cannot be staked
or weighted effectively. Straw/compost wattles may also be installed around excavations or on the downhill
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side of excavations to reduce stormwater flow rates if required because of precipitation and runoff. The
vegetation around the work areas will be maintained to the extent possible to provide additional filtering
beyond work areas.
The specific BMPs to control flow rates that will be used on this project include:
■ Perimeter Protection (BMP D.2.1.3)
■ Straw Wattles, staked or weighted (BMP D.2.1.2.5)
■ Silt Fence (BMP D.2.1.3.1) (if needed)
■ Vegetative Strip (BMP D.2.1.3.3)
■ Compost Socks (BMP D.2.1.3.6)
4.1.4 Element No. 4: Traffic Area Stabilization
Construction access will be from the paved surfaces of adjacent roadways and the existing main driveway
to the station from Benson Drive South. The driveway into the site is paved, while the parking areas adjacent
to the driveway are gravel surfaced. Temporary ground protection mats and wood chips mulch will be used
to protect existing ground and vegetation from construction equipment in non-paved areas. Construction
equipment will enter and leave the site from existing asphalt driveway to minimize track out of soil onto
Benson Drive South. The construction crews will keep paved surfaces swept to prevent soil materials from
migrating off-site. If necessary, a street sweeper will be used to keep the driveways and roadways clean.
The BMPs relevant to establishing construction access that will be applied for this project include:
■ Traffic Area Stabilization (BMP D.2.1.4)
■ Stabilized Construction Entrance (D.2.1.4.1)
■ Construction Road/Parking Area Stabilization (D.2.1.4.2)
■ Protective matts, wood chips or mulch on areas of grass, removed trees or underground piping.
4.1.5 Element No. 5: Sediment Retention
All stormwater runoff from disturbed areas will pass through an appropriate sediment removal BMP before
leaving the construction site. Silt fence or straw wattles, compost socks, vegetated strips and catch basin
inserts will be used to control sediment-laden runoff and stormwater run-on from excavations as needed.
If needed, gravel or sandbag berms can be used to filter turbid water before leaving the site. There is one
catch basin in the station near the northeast corner of the site.
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As a protective measure, the BMPs relevant to controlling sediment that will be applied for this project
include:
■ Sediment Retention (BMP D.2.1.5)
■ Storm Drain Inlet Protection, including Gravel and Sandbag Berms (BMP D.2.1.5.3)
■ Straw Wattles, staked (BMP D.2.1.2.5)
■ Silt Fence (BMP D.2.1.3.1)
■ Vegetated Strip (BMP D.2.1.3.3)
■ Compost Socks (BMP D.2.1.3.6)
4.1.6 Element No. 6: Surface Water Collection
The project is not anticipated to cause measurable changes in stormwater runoff flow rates during
construction. Construction activity may cause the temporary channelization of stormwater runoff which will
be mitigated by filtering and dispersing runoff through straw wattles and compost socks. Straw wattles,
compost socks, or gravel or sand bag berms will be used to divert stormwater away from work areas and
excavations to the extent possible. If stormwater does flow into excavations, this water will be pumped from
the excavations using temporary submersible pumps. The water will be discharged through sediment bags
to a dry, vegetated area for infiltration. Water also may be removed using vacuum trucks and discharged
off-site at an approved disposal facility. All discharge areas will be observed for erosion and to check for
infiltration. Turbid water will not discharge to surface water bodies, including Rolling Hills Creek. No
trenches or channels will be constructed as part of the project to intercept surface water from upstream or
downstream of the work areas.
The following BMPs will be used to intercept all surface water from disturbed areas or to control erosion at
any discharge hose outlet and within the vegetated areas, if necessary:
■ Surface Water Collection (BMP D.2.1.6)
■ Straw Wattles (staked, BMP D.2.1.2.5)
■ Compost Socks (BMP D.2.1.3.6)
■ Pumps and Flexible Hoses, with discharge through sediment bag to dry, stable, vegetated areas for
infiltration.
■ Sediment Bag
■ Gravel or Sandbag Berms
4.1.7 Element No. 7: Dewatering Control
Dewatering is not anticipated as part of the project at this time. However, dewatering may be required if
unseasonably heavy precipitation occurs during construction, or if groundwater is encountered within the
excavations. If needed, water will be removed from excavations using submersible pumps. Dewatering
water will be discharged through sediment bags to a dry, stable, vegetated area for infiltration. Straw
wattles, compost socks, or gravel or sand bag berms will be used to slow discharged water flow for
infiltration. Water may also be removed using vacuum trucks and discharged off-site at an approved
disposal facility. Appropriate pumping methods are to be determined by the contractor depending on site
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conditions and needs. Extra pumps will be on-site to control stormwater runoff in the event of primary pump
failure.
If needed, the following BMPs will be used to control erosion at any channels or outlets during dewatering:
■ Dewatering Control (BMP D.2.1.7)
■ Straw Wattles (staked, BMP D.2.1.2.5)
■ Compost Socks (BMP D.2.1.3.6)
■ Pumps and Flexible Hoses, with discharge through sediment bag to dry, stable, vegetated areas for
infiltration.
■ Sediment Bag
■ Gravel or Sandbag Berms
4.1.8 Element No. 8: Dust Control
Prevention measures to minimize the wind transport of soil from work areas shall be taken to prevent
sediment and dust from being blown from the site onto roadways, drainage ways and surface waters.
Control measures shall be implemented when exposed soils are dry enough to be blown by the wind. The
following BMP will be used to control dust during construction:
■ Dust Control (BMP D.2.1.8)
4.1.9 Element No. 9. Flow Control
Surface water from disturbed areas are not expected to increase surface water flow of the existing site
conditions above the existing 2-year and 10-year runoff peaks discharging from the site during construction.
The proposed work is scheduled to be completed during the drier months of the year. However, if
unseasonably heavy precipitation occurs during construction, water will be directed away from drainage
areas and Rolling Hills Creek using straw wattles, compost socks, or gravel or sandbag berms. If needed,
water will be contained and removed using vacuum trucks and discharged off-site at an approved disposal
facility. Appropriate pumping methods are to be determined by the contractor depending on site conditions
and needs. Extra pumps will be on-site to control stormwater runoff in the event of primary pump failure.
If needed, the following BMPs will be used to control flow during construction:
■ Flow Control (BMP D.2.1.9)
■ Straw Wattles (staked, BMP D.2.1.2.5)
■ Compost Socks (BMP D.2.1.3.6)
■ Pumps and Flexible Hoses, with discharge through sediment bag to dry, stable, vegetated areas for
infiltration.
■ Sediment Bag
■ Gravel or Sandbag Berms
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4.1.10 Element 10: Control Pollutants
All pollutants, including waste materials that occur during construction, will be handled and disposed of in
a manner that is consistent with practices that do not cause contamination of stormwater, surface water
or groundwater. Good housekeeping and preventive measures will be taken to ensure that the site will be
kept clean, well-organized and free of debris.
Spill response kits will be located on the site for rapid and easy access. Any equipment leaks from a fuel
tank, equipment seal or hydraulic line will be contained within a spill pad placed beneath potential leak
sources. Each spill response kit will include plastic sheeting, tarps, overpack drums, absorbent pads and
kitty litter. Shovels and excavating equipment will be onsite and the contractor will be prepared to excavate
and remove impacted soil if a spill occurs.
Cover, containment and protection from vandalism will be provided for all chemicals, liquid products,
petroleum products and non-inert wastes present on the site (see Washington Administrative Code
[WAC] 173-304 for a definition of inert waste). Maintenance and repair of heavy equipment and vehicles
should be performed to the extent practical at off-site locations, or if warranted, at service facilities away
from the site. Maintenance and repair at on-site locations must be conducted using spill prevention
measures such as drip pans, temporary impermeable liners, absorbent pads and other appropriate
methods. Contaminated surfaces will be cleaned immediately following any discharge or spill incident.
Emergency repairs may be performed on-site using temporary plastic placed beneath, and if raining, over
the equipment.
The following specific BMPs that will be used to control pollutants include:
■ Material Delivery, Storage and Containment (BMP D.2.2.4)
■ Maintain Protective BMPS (BMP D.2.2.10)
Other BMP practices to be implemented to control specific sources of pollutants are discussed below.
4.1.10.1 VEHICLES, CONSTRUCTION EQUIPMENT AND/OR PETROLEUM PRODUCT STORAGE/DISPENSING
■ All vehicles, equipment and petroleum product storage/dispensing areas will be inspected at least daily
to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills.
■ Contaminated surfaces will be cleaned immediately following any discharge or spill incident.
4.1.10.2 CHEMICAL STORAGE
Chemicals will not be stored on-site as part of the project. However, if any chemicals are used or temporarily
stored in the construction areas, storage and handling procedures will conform to the details of the
following BMPs:
■ Material Delivery, Storage and Containment (BMP D.2.2.4)
■ Maintain Protective BMPS (BMP D.2.2.10)
4.1.10.3 EXCAVATION AND DEWATERING WASTE
Dewatering BMPs and BMPs specific to the excavation are discussed under Element No. 7.
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4.1.10.4 DEMOLITION
Demolition activities include removing portions of existing chain link fence (posts will be cut at ground
surface with foundations abandoned in place), hazardous trees will be cut at ground surface with stump
and roots abandoned in-place, existing concrete gate controller pads (about 2 feet by 2 feet) will be
replaced and a narrow portion of asphalt driveway will be saw cut and restored in-kind to support conduit
installation for security power and communications services.
4.1.10.5 CONCRETE AND GROUT
Minor concrete work is anticipated as part of the project. Concrete work will be associated with fence post
installation. Wash water from areas should not be allowed to drain directly (without detention or treatment)
to natural or constructed stormwater conveyances or Rolling Hills Creek. Wash water and leftover product
should be contained in a lined container when no designated concrete washout areas (or formed areas)
are available. Contained concrete and concrete wash water (process water) should be disposed of properly
off-site. Under no circumstances shall concrete wash water be allowed to discharge to any site ground
surfaces or the site storm drain system.
The following specific BMPs that will be used to control pollutants associated with concrete handling
include:
■ SWPPS Measures (BMP D.2.2)
■ Concrete Handling (BMP D.2.2.1)
■ Concrete Washout Area (BMP D.2.2.2)
■ Sawcutting and Surfacing Pollution Prevention (BMP D.2.2.3)
4.1.10.6 SANITARY WASTEWATER
Portable sanitation facilities will be firmly secured, regularly maintained and emptied when necessary.
4.1.10.7 SOLID WASTE
Solid waste will be stored in secure, clearly marked containers.
4.1.10.8 OTHER
Other BMPs will be administered as necessary to address any additional pollutant sources onsite.
4.1.11 Element No. 11: Protect Existing and Proposed Flow Control BMPs
Sedimentation and soil compaction reduce the infiltration capacity of native and engineered soils.
Protection measures shall be used to prevent adverse impacts to existing flow control BMPs at the site.
Engineered soils have not been used at the site for infiltration purposes. No new flow control structures are
planned as part of this project and existing flow control structures will not be impacted as part of this
project. Temporary protective matts or mulch will be used to protect native and existing fill soils from
compaction during fence and conduit construction activities.
The following BMPs will be used during construction:
■ Protect Existing and Proposed Stormwater Facilities and On-Site BMPs (BMP D.2.1.10)
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4.1.12 Element No. 12: Maintain BMPs
All temporary and permanent erosion and sediment control BMPs will be maintained and repaired as
needed to ensure continued performance of their intended function. Maintenance and repair will be
conducted in accordance with each particular BMP’s specification.
The following specific BMPs that will be used to maintain BMPs include:
■ Maintain Protective BMPs (BMP D.2.1.11)
Whenever site observation reveals that the BMPs identified in this CSWPPS are inadequate because the
actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or
design changes will be implemented as soon as possible.
All temporary erosion and sediment control BMPs will be removed within 30 days after the final site
stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment will be
removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation will be
permanently stabilized.
4.1.13 Element No. 13: Manage the Project
Temporary erosion and sediment control BMPs for this project have been designed based on the following
principles:
■ Emphasize erosion control rather than sediment control.
■ Minimize the extent and duration of the area exposed.
■ Retain sediment onsite.
■ Thoroughly observe site and maintain all erosion and sediment control measures.
■ Schedule major earthwork during the dry season
All BMPs will be inspected, maintained and repaired, as needed, to ensure continued performance of their
intended functions during the project. Site observations will be conducted by a qualified person who will be
on-site daily and/or on-call in case a stormwater issue arises. This person has the necessary skills to:
■ Assess the site conditions and construction activities that could impact the quality of stormwater.
■ Assess the effectiveness of erosion and sediment control measures used to control the quality of
stormwater discharges.
The following specific BMPs that will be used for project management include:
■ Manage the Project (BMP D.2.1.12)
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5.0 Construction Schedule and BMP Implementation
The BMP implementation schedule is driven by the construction schedule. The following provides a
sequential list of the proposed construction schedule milestones and the corresponding BMP
implementation schedule. However, target dates are for planning purposes only and are subject to revision.
The project site is located west of the Cascade Mountain Crest. As such, the dry season is considered to be
from May 1st to September 30th, and the wet season is considered to be from October 1st to April 30th.
CONSTRUCTION SCHEDULE
CONSTRUCTION SCHEDULE MILESTONES IMPLEMENTATION SCHEDULE
Mobilize equipment to site June 2026
Install ESC measures June 2026
Estimated tree and shrub cutting activities June 2026
Estimated ground disturbing activities June 2026
Estimated restoration/stabilization September 2026
Demobilize equipment from site September 2026
6.0 Pollution Prevention Team
6.1 ROLES AND RESPONSIBILITIES
The pollution prevention team consists of personnel responsible for implementation of the CSWPPS,
including the following:
■ Project Manager – Owner representative that is the project’s supervising engineer responsible for
observations and issuing instructions and drawings to the contractor’s site supervisor or
representative.
■ Contractor – the person, firm or corporation with whom the owner has the contract to perform all
project area work, including installing and maintaining requirements of the CSWPPS for the duration of
the project.
■ TESC/BMP responsible person – primary contractor contact, responsible for site observations (BMPs,
visual observation, sampling, recording, etc.); to be called upon in case of failure of any erosion and
sediment control measures.
■ TESC/BMP Supervisor – primary contact for site inspector responsible for issuing additional
instructions in case of failure of any erosion and sediment control measures and for contacting
Project Manager and then Ecology.
■ Emergency Owner Contact – individual that is the site owner or representative of the site owner to be
contacted in the case of an emergency.
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■ Washington Emergency Management Division (ERTS) and National Response Center – Reporting
centers to be contacted by the Project Manager if contaminated liquids or product enters the roadside
ditches or nearby stream networks areas.
6.2 TEAM MEMBERS
Names and contact information for those identified as members of the pollution prevention team are
provided in the following table. Chain of command should be followed at all times and is established as
follows: TESC/BMP personnel should report directly to TESC/BMP supervisor and coordinate daily activities
with the Project Manager.
CSWPPS TEAM MEMBERS
TITLE NAME(S) PHONE NUMBER
PSE Project Manager James Mauldin 206.940.9557
PSE Construction Manager Sam Hicks 206-817-3704
PSE Land Planning Contacts Kathryn Hodges
Elaine Babby
206.549.7606
425.462.3805
PSE Emergency Contact James Mauldin 206.940.9557
Contractor Contact TBD TBD
TESC/BMP Responsible Person Carla Woodworth 425.466.6772
TESC/BMP Supervisor Carla Woodworth 425.466.6772
REPORTING TO ECOLOGY WILL BE DIRECTED CONDUCTED BY PSE PERSONNEL; CONTACT INFORMATION IS LISTED FOR
REFERENCE.
Emergency Ecology Contact Report a Spill 425.649.6300
Emergency Ecology Contact
(non-office hours) Northwest Regional Office 206.594.0000
Ecology Contact (office hours) Northwest Regional Office 206.594.0000
Washington Emergency Management
Division (ERTS) 1.800.258.5990,
1.800.OILS.911
National Response Center 1.800.424.8802
6.3 SPILL AND RELEASE RESPONSE
In the event of a discharge or release of oil, fuel or chemicals into state waters or onto land with a potential
for entry into state waters, containment and clean-up efforts will begin immediately and be completed as
soon as possible, taking precedence over normal work. Clean-up will include proper disposal of any spilled
material and used clean-up materials. The event also needs to be reported to Ecology, ERTS and the
National Response Center at the number listed in the above table.
7.0 Site Observation
Site observation includes visual observation of all BMPs and visual observation for turbidity.
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File No. 9186-184-00 Task 2032
All BMPs will be inspected daily. All BMPs will be maintained and repaired as needed to ensure continued
performance of their intended function. Site observations will be conducted by a person who is
knowledgeable in the principles and practices of erosion and sediment control. The on-site inspector will
have the skills to assess the potential for water quality impacts as a result of the type of construction
activities occurring on-site, and the knowledge of the appropriate and effective erosion and sedimentation
control measures needed to control the quality of stormwater discharges.
Site observations will occur in all areas disturbed by construction activities and at all stormwater discharge
points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration and
oily sheen. The site inspector will evaluate the effectiveness of the installed BMPs and determine if it is
necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All new
BMPs or design changes will be documented on the TESC plans as soon as possible.
7.1 STORMWATER TURBIDITY OBSERVATION
Visual water quality observation locations for turbid runoff discharged from the site, except for infiltration,
will be field determined based on runoff observed during work activities. Contingency locations may be
added in the vicinity of the area of work, as needed and as work progresses. If suspended sediment,
turbidity, discoloration and oily sheen is observed on surface water in the project areas, the following steps
will be conducted:
■ Monitoring of Discharges (BMP D.2.3.2)
■ Ensure all BMPs specified in this CSWPPS are installed and functioning as intended.
■ Assess whether additional BMPs should be implemented, and document additional BMPs that were
installed in the CSWPPS and on the TESC plans if revised.
7.2 PH
Minor concrete work is planned for the project. Visual water quality observation locations for discharge or
release of concrete or concrete slurry will be field determined based on runoff observed during concrete
work activities. If concrete impacted surface water is observed, containment and clean-up efforts will begin
immediately and be completed as soon as possible, taking precedence over normal work. Clean-up will
include proper disposal of any spilled material and used clean-up materials. The following steps also will
be conducted:
■ Ensure all BMPs specified in this CSWPPS are installed and functioning as intended.
■ Assess whether additional BMPs should be implemented, and document additional BMPs that were
installed in the CSWPPS and on the TESC plans if revised.
8.0 Recordkeeping
8.1 ACCESS TO PLANS AND RECORDS
This CSWPPS will be retained onsite or within reasonable access to the site.
Puget Sound Energy | April 22, 2026 Page 16
File No. 9186-184-00 Task 2032
8.2 UPDATING THE CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN
This CSWPPS will be modified if the CSWPPS is ineffective in eliminating or significantly minimizing
pollutants in stormwater discharges from the work areas or there has been a change in design,
construction, operation or maintenance at the site that has a significant effect on the discharge, or potential
for discharge, of pollutants to the waters of the State. The CSWPPS will be modified within 7 days of
determination based on observation(s) that additional or modified BMPs are necessary to correct problems
identified, and an updated timeline for BMP implementation will be prepared.
9.0 References
City of Renton Maps (COR). 2024a. Available at COR Maps | City of Renton
Swarr Station (Security Perimeter Maintenance) Arborist Report by Davey Resource Group, Inc. dated
07/2024 (Updated 10/2025).
Washington State Administrative Code [WAC] 173-304, Minimal Functional Standards for Solid Waste
Handling. Available at Chapter 173-304 WAC:
Washington State Department of Ecology (Ecology). 2025. Water Quality Atlas - Map. Available at:
https://apps.ecology.wa.gov/waterqualityatlas/wqa/map?CustomMap=y&BBox=-13612568,
6008369,-13591048,6030789&RT=0&Layers=27&Filters=y,n,n,n,n,n&F1.4=n,n,n,n,n,y
Appendices
Appendix A
Temporary Erosion and Sediment Control Plan
(Completed by others)
ECB
ECB
M
S
S
M
M
M M
M
M
M
M
M
T
U
D
M
P
P
P
PP
P
UR
G
G
G
G
G
G
G
G
G
G
G
G
G
S
1
7
0
1
7
0
1
8
0
1
9
0
2
1
0
200
2
3
0
2
4
0
22
0
21
0
20
0
1
9
0
18
0
2
0
0
19
0
1
8
0
17
0
1
6
0
17
0
1
8
0
1
9
0
2
0
0
19
0
1
8
0
1
7
0
160
15
0
150
2
1
0
20
0
19
0
18
0
17
0
16
0
2
5
0
1
5
0
16
0
17
0
1
5
0
15
0
1
4
0
1
3
0
1
3
0
140
150
xx
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Δ
=
3
5
°
1
8
'
2
5
"
R
=
3
8
4
.
2
6
'
L
=
2
3
6.7
9
'
S
2
1
°
2
2
'
1
0
"
E
4
2
9
.
8
7
'
S0
5
°
1
0
'
1
6
"
E
1
6
5
.
5
1
'
S0
0
°
4
5
'
4
9
"
W
6
3
1
.
1
5
'
S
1
6
°
2
2
'
1
0
"
E
1
,
1
1
5
.
9
2
'
BE
N
S
O
N
D
R
S
(
S
R
-
5
1
5
)
SWARR STATION
1
8
6
184
SWARR STATION
S
P
U
G
E
T
D
R
VICINITY MAP
SITE167
181
515
169
OA
K
E
S
D
A
L
E
A
V
E
S
W
900
S 2
1
S
T
S
T
I-405
SEE SURVEY SHT
6 OF 6 FOR
PARCEL SITE PLAN
SITE PLAN
SWARR STATION SECURITY MAINTENANCE
QUARTER-SECTION-TOWNSHIP-RANGE: SW 1/4 SEC. 20, TWP 23 N., RNG. 05E., W.M.
CITY OF RENTON, KING COUNTY, WASHINGTON
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
Call before you dig.
PUGET SOUND ENERGY
SWARR STATION SECURITY MAINTENANCE PROJECT
2100 BENSON DRIVE S, RENTON, WA 98055 SW
A
R
R
S
T
A
T
I
O
N
S
E
C
U
R
I
T
Y
M
A
I
N
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E
N
A
N
C
E
P
R
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J
E
C
T
SW
A
R
R
S
T
A
T
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O
N
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I
T
Y
M
A
I
N
T
E
N
A
N
C
E
P
R
O
J
E
C
T
WO NUMBER: 142003204 (LEADING), 10860860 (RETIREMENT)
G0
0
1
COVER SHEET
04/19/202604/14/2026
x
x
x
W
W
W
W
W
W
W
P
P
P
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
P
P
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
x
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TOP
NAIL IN CONC FILLED 2" IRON PIPE
IN CONC MONUMENT IN CASE -0.6'
BELOW GRADE (VISITED JUNE
2023) 389+83.40 P.T. BK 389+92.43
AHD. 31'RT. (DOT)
ECB
ECB
CONC
CONC
G
A
T
E
G
A
T
E
PCONC
CONC
ASPH
DW
M
TO
P
TO
P
DIT
W W
W
TO
P
NAIL IN CONC FILLED 2" IRON PIPE
IN CONC MONUMENT IN CASE -0.3'
BELOW GRADE. (VISITED JUNE 2023)
391+62.25 31' RT (DOT)
391+62.28 32'RT (C)
8898700680
N/A
TOP
TO
P
VARIES R/
W
R/
W
EP
EP
EP
EP
EP
TO
P
BE
N
S
O
N
D
R
S
(
S
R
-
5
1
5
)
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SWARR STATION
M M
M
M
M
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TOP
TOP
TOE
TO
E
TO
P
ER(2)
TOE
TOE/ROCKERY
SD
CBW
36
"
C
M
P
GVL
24
"
C
O
N
C
P
I
P
E
W/
N
O
T
O
P
S
D
SD
CONC, TYP
CONC EX
P
O
S
E
D
P
I
P
E
S
GA
T
E
GVL
ER(2)CW
CONC W/
VENT, TYP
GENERATOR
EA
V
E
WR(2)
WMICV
CONC
SD
D
DI
T
/
H
A
L
F
P
I
P
E
EX LIGHT POLE
W/ CAMERAS
TOP
GVL
WV
TOP
TO
P
TOP
M
W W W W W W W
P
P
P
P
P
P
P
P
P
PPW
P
P
P P P P
P
P
P
P
P
P
P
P
P
P
P P P P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
DIT
P
ER
P
P
GV
GV
ECC
GV
URGV
ECCECC
DIT
DI
T
DIT
GVL
EG
EG
E
G
S
TO
P
S
℄
R/
W
G G G G G G G G G G G G G G G G
G
G G G G G G G G
G
G G G G G G G G G
G
G G
G
G G G G G G G G
G G
G
G
G G G G G G G G G G
G G G
10'
EP
10
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W
I
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W
A
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D
I
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.
95
1
1
1
6
0
3
9
2
TOP
15' WIDE
P
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R
M
A
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N
T
EASEME
N
T
P
E
R
RECORDI
N
G
N
O
.
7
8
1
2
2
1
0
9
4
2
10' WIDE
T
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NO. 781
2
2
1
0
9
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2
15
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.
77
0
7
0
1
1
0
0
9
15' WIDE PUBLIC
UTILITIES EASEMENT
PER RECORDING NO.
7707011009
1
5
'
W
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E
P
U
B
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7
7
0
7
0
1
1
0
0
9
10'
5'
1
5
'
15
'
ASPH DW
ASPH
TOE
TOE
BUILDING
DI
T
/
H
A
L
F
P
I
P
E
GRASS
15'
SD
10
'
10'
10' WIDE WATER
EASEMENT PER
RECORDING NO.
9511160392
18
4
164
16
6
16
8
1
7
0
18
0
1
7
2
17
4
17
6
1
7
8
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1
7
0
1
6
2
1
6
4
1
6
6
1
6
8
17
2
1
7
0
18
0
1
9
0
20
0
21
0
1
6
8
17
2
1
7
4
17
6
1
7
8
18
2
18
4
18
6
18
8
1
9
2
19
4
19
4
1
9
4
1
9
6
19
8
20
2
20
4
20
6
20
8
17
0
18
0
1
9
0
164
16
6
168
17
2
1
7
4
17
6
178
18
2
1
8
4
1
8
6
1
8
8
1
9
2
1
9
4
1
9
6
19
8
17
0
18
0
16
6
16
8
17
2
17
4
1
7
6
1
7
8
1
8
2
1
8
4
24617
0
19
0
2
0
0
21
0
2
2
0
23
0
2
4
0
18
0
17
4
17
6
17
8
18
2
18
4
18
6
18
8
16
0
1
7
0
18
0
16
2
16
4
16
6
16
8
1
7
2
1
7
4
1
7
6
1
7
8
160
17
0
18
0
1
9
0
20
0
154
156
158
162
164
16
6
1
6
8
1
7
2
17
4
17
6
17
8
18
2
1
8
4
18
6
1
8
8
1
9
2
1
9
4
19
6
1
9
8
20
2
20
4
20
6
20
8
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
8898700660
2107 WELLS CT S
2103 WELLS CT S
8898700670
889870TR-D 1016 S 22ND CT
8898700710 8898700720
1022 S 22ND CT 1102 S 22ND CT
8898700730
2100 BENSON DR S
2023059071
2104 WELLS CT S
x
xxx
x
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xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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S87°07'55"W 764.47'
N0
0
°
1
2
'
1
0
"
W
3
2
.
0
9
'
S0
5
°
1
0
'
1
6
"
E
1
6
5
.
5
1
'
S0
0
°
4
5
'
4
9
"
W
6
3
1
.
1
5
'
TESC PLAN (SOUTH)
KEY MAP
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
Call before you dig.
PUGET SOUND ENERGY
SWARR STATION SECURITY MAINTENANCE PROJECT
2100 BENSON DRIVE S, RENTON, WA 98055 SW
A
R
R
S
T
A
T
I
O
N
S
E
C
U
R
I
T
Y
M
A
I
N
T
E
N
A
N
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P
R
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J
E
C
T
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A
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T
A
T
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O
N
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R
I
T
Y
M
A
I
N
T
E
N
A
N
C
E
P
R
O
J
E
C
T
WO NUMBER: 142003204 (LEADING), 10860860 (RETIREMENT)
C0
0
2
TESC PLAN (SOUTH)
04/19/202604/14/2026
P
P
P P
P
P
P
P P P
P P
P P
P P
P
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
^
^
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^
^
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^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
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^
^
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^
^
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^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
7' CLF W/ BW
7' CLF W/ BW
TO
P
SD
SD
SD
SD
TO
E
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
ASPH
DW
GATE
TOP
ER(2)
T
O
E
T
O
E
TO
P
EM
SD
SD
GATE
CBW
SD
SD
SD
SD
SD
SD
SD
SD
N/
A
EP
EP
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P
7'
C
L
F
W
/
B
W
BE
N
S
O
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R
S
(
S
R
-
5
1
5
)
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
S
S
SWARR STATION
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
M
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^
^^^^^^^^^^^^^^
^^^^
^
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^
^
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M
^^^^
^
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^
^
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SP-1
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GEI
TO
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TOP
TO
P
TO
P
T
O
P
BUILDING
GA
T
E
CONC
STEEL
STEPS
EXPOSED PIPES
ER
GVL
ER
P
P
^
^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
M
M
^^^^
^
^^^^^^^^^^^^^^^^^^^^^
^
^
^^^^^^^^^^^^^^^^
T
GVL
GRASS
TOE
T
O
E
TOE
TOP
TO
P
GVL
GVL
GVL
GVL
DW TO
E
T
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P
TO
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R
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K
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GA
T
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W/ CAMERAS
TOE
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EG
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EXPOSED
PIPES ON
CONC
GVL
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EX
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D
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S
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SD
36
"
C
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SHED
GVL
CONC, TYP
GVL
GVL
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EX
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CONC W/
GENERATOR
CONC W/
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W/ AC UNIT
ER
W/ SENSOR
TO
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TO
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P
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TOPCONC
CONC
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UNDERGROUND
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UNDERGROUND
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UNDERGROUND
CENTER OF TANK 5
UNDERGROUND
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UNDERGROUND
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UNDERGROUND
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UNDERGROUND CENTER GAS TANK 17
UNDERGROUND CENTER GAS TANK 16
UNDERGROUND CENTER GAS TANK 15
UNDERGROUND CENTER GAS TANK 14
UNDERGROUND CENTER GAS TANK 13
UNDERGROUND CENTER GAS TANK 12
UNDERGROUND CENTER GAS TANK 11
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TESC PLAN (NORTH)
KEY MAP
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
Call before you dig.
PUGET SOUND ENERGY
SWARR STATION SECURITY MAINTENANCE PROJECT
2100 BENSON DRIVE S, RENTON, WA 98055 SW
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WO NUMBER: 142003204 (LEADING), 10860860 (RETIREMENT)
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TESC PLAN (NORTH)
04/19/202604/14/2026
12
1CATCH BASIN INSERT
-
2STRAW WATTLES
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
Call before you dig.
PUGET SOUND ENERGY
SWARR STATION SECURITY MAINTENANCE PROJECT
2100 BENSON DRIVE S, RENTON, WA 98055 SW
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TESC DETAILS
04/19/202604/14/2026
Appendix B
Construction Stormwater BMPs
Puget Sound Energy | April 22, 2025 Page B-1
File No. 9186-184-00 Task 2032
Appendix B
City of Renton Construction Stormwater BMPs
The following is a list of construction stormwater BMPs that are to be implemented during the project.
Where applicable, BMPs are labeled according to the City of Renton Surface Water Design Manual
(RSWDM 20221) BMP detail number and BMP details subsequently follow this page.
■ Clearing Limits (BMP D.2.1.1)
■ High Visibility Fencing (BMP D.2.1.1.1)
■ Cover Measure (BMP D.2.1.2)
■ Mulching (BMP D.2.1.2.2)
■ Plastic Covering (BMP D.2.1.2.4)
■ Straw Wattles, staked or weighted (BMP D.2.1.2.5)
■ Temporary and Permanent Seeding (BMP D.2.1.2.6)
■ Perimeter Protection (BMP D.2.1.3)
■ Silt Fence (BMP D.2.1.3.1)
■ Vegetative Strip (BMP D.2.1.3.3)
■ Compost Socks, staked or weighted (BMP D.2.1.3.6)
■ Traffic Area Stabilization (BMP D.2.1.4)
■ Stabilized Construction Entrance (BMP D.2.1.4.1)
■ Construction Road/Parking Area Stabilization (BMP D.2.1.4.2)
■ Sediment Retention (BMP D.2.1.5)
■ Storm Drain Inlet Protection (BMP D.2.1.5.3)
■ Surface Water Collection (BMP D.2.1.6)
■ Dewatering Control (BMP D.2.1.7)
■ Dust Control (BMP D.2.1.8)
■ Flow Control (BMP D.2.1.9)
■ Protect Existing and Proposed Stormwater Facilities and On-Site BMPs (BMP D.2.1.10)
■ Maintain Protective BMPS (BMP D.2.1.11)
■ Manage the Project (BMP D.2.1.12)
1 City of Renton Surface Water Design Design Manual (RSWDM). 2022. Available at: https://edocs.rentonwa.gov/Documents/
DocView.aspx?id=11464516&dbid=0&repo=CityofRenton
Puget Sound Energy | April 22, 2025 Page B-2
File No. 9186-184-00 Task 2032
■ SWPPS Measures (BMP D.2.2)
■ Concrete Handling (BMP D.2.2.1)
■ Concrete Washout Area (BMP D.2.2.2)
■ Sawcutting and Surfacing Pollution Prevention (BMP D.2.2.3)
■ Material Delivery, Storage and Containment (BMP D.2.2.4)
■ Maintain Protective BMPS (BMP D.2.2.10)
■ Manage the Project (BMP D.2.2.11)
■ Monitoring of Discharges (BMP D.2.3.2)
■ Coarse Arborist Wood Chips
■ Construction Mats
■ Pumps, Flexible Hose or Piping with Diffuser System at End (to be designed, as needed, by contractor)
■ Sediment Bag(s), Gravel or Sandbag or Equivalent Berms/Cofferdams
■ Gravel, Crushed Rock and Asphalt Pavement Restoration
D.2.1 ESC MEASURES
2022 City of Renton Surface Water Design Manual 6/22/2022
D-11
facility, runoff treatment facility, and on-site BMP areas [existing or proposed] shall not be used for
this purpose).
10. Control Pollutants: Stormwater pollution prevention (SWPPS) measures are required to prevent,
reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or
watercourses from construction-related activities such as materials delivery and storage, onsite
equipment fueling and maintenance, demolition of existing buildings and disposition of demolition
materials and other waste, and concrete handling, washout and disposal. Section D.2.2 describes
BMPs specific to this purpose; additionally, several of the ESC BMPs described herein are applicable.
11. Protect Existing and Proposed Stormwater Facilities and On-site BMPs: Sedimentation and soil
compaction reduce the infiltration capacity of native and engineered soils. Protection measures shall
be applied/installed and maintained so as to prevent adverse impacts to existing stormwater facilities
and on-site BMPs and areas of proposed stormwater facilities and on-site BMPs for the project.
Adverse impacts can prompt the requirement to restore or replace affected stormwater facilities and
on-site BMPs.
12. Maintain Protective BMPs: Protection measures shall be maintained to ensure continued
performance of their intended function, to prevent adverse impacts to existing BMPs/facilities and
areas of proposed BMPs/facilities, and protect other disturbed areas of the project.
13. Manage the Project: Coordination and timing of site development activities relative to ESC
concerns, and timely inspection, maintenance and update of protective measures are necessary to
effectively manage the project and ensure the success of protective ESC and SWPPS design and
implementation.
D.2.1.1 CLEARING LIMITS
Prior to any site clearing or grading, those areas that are to remain undisturbed during project construction
shall be delineated. At a minimum, clearing limits shall be installed at the edges of all critical area buffers
and any other areas required to be left uncleared such as portions of the site subject to clearing limits under
RMC 4-4-060, areas around significant trees identified to be retained, on-site BMP areas to be protected,
and other areas identified to be left undisturbed to protect sensitive features.
Purpose: The purpose of clearing limits is to prevent disturbance of those areas of the project site that are
not designated for clearing or grading. This is important because limiting site disturbance is the single
most effective method for reducing erosion. Clearing limits may also be used to control construction
traffic, thus reducing the disturbance of soil and limiting the amount of sediment tracked off site.
When to Install: Clearing limits shall be installed prior to the clearing and/or grading of the site.
Measures to Use: Marking clearing limits by delineating the site with a continuous length of brightly
colored survey tape is sometimes sufficient. The tape may be supported by vegetation or stakes, and it
shall be 3 to 6 feet high and highly visible. Critical areas and their buffers require more substantial
protection and shall be delineated with plastic or metal safety fences or stake and wire fences. Fencing
may be required at the City’s discretion to control construction traffic or at any location where greater
protection is warranted. Permanent fencing may also be used if desired by the applicant. Silt fence, in
combination with survey flagging, is also an acceptable method of marking critical areas and their buffers.
D.2.1.1.1 PLASTIC OR METAL FENCE
Code: FE Symbol:
Purpose
Fencing is intended to (1) restrict clearing to approved limits; (2) prevent disturbance of critical areas, their
buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated
construction entrances or roads; and (4) protect areas where marking with survey tape may not provide
adequate protection.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
6/22/2022 2022 City of Renton Surface Water Design Manual
D-12
Conditions of Use
To establish clearing limits, plastic or metal fence may be used:
1. At the boundary of critical areas, their buffers, and other areas required to be left uncleared.
2. As necessary to control vehicle access to and on the site (see Sections D.2.1.4.1 and D.2.1.4.2).
Design and Installation Specifications
1. The fence shall be designed and installed according to the manufacturer’s specifications.
2. The fence shall be at least 3 feet high and must be highly visible.
3. The fence shall not be wired or stapled to trees.
Maintenance Requirements
1. If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and
visibility restored.
2. Disturbance of a critical area, critical area buffer, native growth retention area, or any other area
required to be left undisturbed shall be reported to the City for resolution.
D.2.1.2 COVER MEASURES
Temporary and permanent cover measures shall be provided to protect all disturbed areas, including the
faces of cut and fill slopes. Temporary cover shall be installed if an area is to remain unworked for more
than seven days during the dry season (May 1 to September 30) or for more than two consecutive working
days during the wet season (October 1 to April 30). These time limits may be relaxed if an area poses a
low risk of erosion due to soil type, slope gradient, anticipated weather conditions, or other factors.
Conversely, the City may reduce these time limits if site conditions warrant greater protection (e.g.,
adjacent to significant aquatic resources or highly erosive soils) or if significant precipitation (see
Section D.2.4.2) is expected. Any area to remain unworked for more than 30 days shall be seeded or
sodded, unless the City determines that winter weather makes vegetation establishment infeasible. During
the wet season, slopes and stockpiles at 3H:1V or steeper and with more than ten feet of vertical relief
shall be covered if they are to remain unworked for more than 12 hours. Also during the wet season, the
material necessary to cover all disturbed areas must be stockpiled on site. The intent of these cover
requirements is to have as much area as possible covered during any period of precipitation.
Purpose: The purpose of covering exposed soils is to prevent erosion, thus reducing reliance on less
effective methods that remove sediment after it is entrained in runoff. Cover is the only practical method
of reducing turbidity in runoff. Structural measures, such as silt fences and sediment ponds, are only
capable of removing coarse particles and in most circumstances have little to no effect on turbidity.
When to Install: Any exposed soils that will remain unworked for more than the time limit set above shall
be covered by the end of the working day. If the exposed area is to remain unworked for more than
30 days, the area shall be seeded with the temporary seed mix or an equivalent mix that will provide rapid
protection (see Section D.2.1.2.6). If the disturbed area is to remain unworked for a year or more or if the
area has reached final grade, permanent seed mix or an equivalent mix shall be applied.
Measures to Use: Cover methods include the use of surface roughening, mulch, erosion control nets and
blankets, plastic covering, seeding, and sodding. Mulch and plastic sheeting are primarily intended to
protect disturbed areas for a short period of time, typically days to a few months. Seeding and sodding are
measures for areas that are to remain unworked for months. Erosion nets and blankets are to be used in
conjunction with seeding steep slopes. The choice of measures is left to the designer; however, there are
restrictions on the use of these methods, which are listed in the “Conditions of Use” and the “Design and
Installation Specifications” sections for each measure.
The methods listed are by no means exhaustive. Variations on the standards presented here are encouraged
if other cost-effective products or methods provide substantially equivalent or superior performance. Also,
D.2.1 ESC MEASURES
2022 City of Renton Surface Water Design Manual 6/22/2022
D-13
the details of installation can, and should, vary with the site conditions. A useful reference on the
application of cover measures in the Puget Sound area is Improving the Cost Effectiveness of Highway
Construction Site Erosion and Pollution Control, Horner, Guedry, and Kortenhof (1990).
D.2.1.2.1 SURFACE ROUGHENING
Purpose
The purpose of surface roughening is to aid in the establishment of vegetative cover and to reduce runoff
velocity, increase infiltration, and provide for sediment trapping through the provision of a rough soil
surface. The rough soil surface may be created by operating a tiller or other equipment on the contour to
form horizontal depressions or by leaving slopes in a roughened condition by not fine grading.
Conditions of Use
1. All slopes steeper than 3H:1V and greater than 5 vertical feet require surface roughening to a depth of
2 to 4 inches prior to seeding.
2. Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding
takes place.
3. Slopes with a stable rock face do not require roughening.
4. Slopes where mowing is planned should not be excessively roughened.
Design and Installation Specifications
There are different methods for achieving a roughened soil surface on a slope, and the selection of an
appropriate method depends upon the type of slope. Roughening methods include stair-step grading,
grooving, contour furrows, and tracking. See Figure D.2.1.2.A for information on tracking and contour
furrows. Factors to be considered in choosing a method are slope steepness, mowing requirements, and
whether the slope is formed by cutting or filling. Sole reliance on roughening for temporary erosion
control is of limited effectiveness in intense rainfall events. Stair-step grading may not be practical for
sandy, steep, or shallow soils.
1. Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough after
filling
2. Stair Step grading is particularly appropriate in soils containing large amounts of soft rock. Each
step” catches material that sloughs from above, and provides a level site where vegetation can
become established. Stairs should be wide enough to work with standard earth moving equipment.
Stair steps must be on contour or gullies will form on the slope.
3. Areas that will be mowed (slopes less steep than 3H:1V) may have small furrows left by disking,
harrowing, raking, or seed-planting machinery operated on the contour.
4. Graded areas with slopes greater than 3H:1V but less than 2H:1V should be roughened before
seeding. This can be accomplished in a variety of ways, including “track walking” or driving a crawler
tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours.
5. Tracking is done by operating equipment up and down the slope to leave horizontal depressions in the
soil.
Maintenance Standards
Periodically check roughened, seeded, planted, and mulched slopes for rills and gullies, particularly after a
significant storm event. Fill these areas slightly above the original grade, then re-seed and mulch as soon
as possible.
D.2.1 ESC MEASURES
2022 City of Renton Surface Water Design Manual 6/22/2022
D-15
D.2.1.2.2 MULCHING
Code: MU Symbol:
Purpose
The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also
enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and
moderating soil temperatures. There is an enormous variety of mulches that may be used. Only the most
common types are discussed in this section.
Conditions of Use
As a temporary cover measure, mulch should be used:
1. On disturbed areas that require cover measures for less than 30 days
2. As a cover for seed during the wet season and during the hot summer months
3. During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief.
Design and Installation Specifications
For mulch materials, application rates, and specifications, see Table D.2.1.2.A. Note: Thicknesses may be
increased for disturbed areas in or near critical areas or other areas highly susceptible to erosion.
Maintenance Standards
1. The thickness of the cover must be maintained.
2. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the
erosion problem is drainage related, then the drainage problem shall be assessed and alternate drainage
such as interceptor swales may be needed to fix the problem and the eroded area remulched.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
6/22/2022 2022 City of Renton Surface Water Design Manual
D-16
TABLE D.2.1.2.A MULCH STANDARDS AND GUIDELINES
Mulch
Material
Quality Standards Application
Rates
Remarks
Straw Air-dried; free from
undesirable seed and
coarse material
2–3 thick;
5 bales per
1,000 sf or 2–
3 tons per acre
Cost-effective protection when applied with
adequate thickness. Hand-application generally
requires greater thickness than blown straw. Straw
should be crimped to avoid wind blow. The
thickness of straw may be reduced by half when
used in conjunction with seeding.
Wood Fiber
Cellulose
No growth inhibiting
factors
Approx. 25–30 lbs
per 1,000 sf or
1,500–2,000 lbs
per acre
Shall be applied with hydromulcher. Shall not be
used without seed and tackifier unless the
application rate is at least doubled. Some wood
fiber with very long fibers can be effective at lower
application rates and without seed or tackifier.
Compost No visible water or
dust during handling.
Must be purchased
from supplier with
Solid Waste Handling
Permit.
2 thick min.;
approx. 100 tons
per acre (approx.
1.5 cubic feet per
square yard)
More effective control can be obtained by
increasing thickness to 3 (2.25 cubic feet per
square yard). Excellent mulch for protecting final
grades until landscaping because it can be directly
seeded or tilled into soil as an amendment.
Compost may not be used in Sensitive Lake7
basins unless analysis of the compost shows no
phosphorous release.
Hydraulic
Matrices
Bonded
Fiber Matrix
BFM])
This mulch category
includes hydraulic
slurries composed of
wood fiber, paper
fiber or a
combination of the
two held together by
a binding system.
The BFM shall be a
mixture of long wood
fibers and various
bonding agents.
Apply at rates
from 3,000 lbs per
acre to 4,000 lbs
per acre and
based on
manufacturers
recommendations
The BFM shall not be applied immediately before,
during or immediately after rainfall so that the
matrix will have an opportunity to dry for 24 hours
after installation. Application rates beyond 2,500
pounds may interfere with germination and are not
usually recommended for turf establishment. BFM
is generally a matrix where all fiber and binders
are in one bag, rather than having to mix
components from various manufacturers to create
a matrix. BFMs can be installed via helicopter in
remote areas. They are approximately $1,000 per
acre cheaper to install.
Chipped Site
Vegetation
Average size shall be
several inches.
2 minimum
thickness
This is a cost-effective way to dispose of debris
from clearing and grubbing, and it eliminates the
problems associated with burning. Generally, it
should not be used on slopes above approx. 10%
because of its tendency to be transported by
runoff. It is not recommended within 200 feet of
surface waters. If seeding is expected shortly after
mulch, the decomposition of the chipped
vegetation may tie up nutrients important to grass
establishment.
7 Sensitive lake means a lake that has proved to be particularly prone to eutrophication; the City did not have any lakes that had
this designation at the time of SWDM adoption.
D.2.1 ESC MEASURES
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D-19
D.2.1.2.4 PLASTIC COVERING
Code: PC Symbol:
Purpose
Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.
Conditions of Use
1. Plastic covering may be used on disturbed areas that require cover measures for less than 30 days.
2. Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid
breakdown of most polyethylene sheeting makes it unsuitable for long-term applications.
3. Clear plastic sheeting may be used over newly-seeded areas to create a greenhouse effect and
encourage grass growth. Clear plastic should not be used for this purpose during the summer months
because the resulting high temperatures can kill the grass.
4. Due to rapid runoff caused by plastic sheeting, this method shall not be used upslope of areas that
might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes.
Note: There have been many problems with plastic, usually attributable to poor installation and
maintenance. However, the material itself can cause problems, even when correctly installed and
maintained, because it generates high-velocity runoff and breaks down quickly due to ultraviolet
radiation. In addition, if the plastic is not completely removed, it can clog drainage system inlets and
outlets. It is highly recommended that alternatives to plastic sheeting be used whenever possible and that
its use be limited.
Design and Installation Specifications
1. See Figure D.2.1.2.D for details.
2. Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
3. If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be
installed at the toe of the slope in order to reduce the velocity of runoff.
FIGURE D.2.1.2.D PLASTIC COVERING
TIRES, SANDBAGS, OR
EQUIVALENT MAY BE USED
TO WEIGHT PLASTIC
SEAMS BETWEEN SHEETS
MUST OVERLAP A MINIMUM
OF 12" AND BE WEIGHTED
OR TAPED
TOE IN SHEETING
IN MINIMUM 4"X4"
TRENCH
PROVIDE ENERGY DISSIPATION
AT TOE WHEN NEEDED
10' MAX.
10' MAX.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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Maintenance Standards for Plastic Covering
1. Torn sheets must be replaced and open seams repaired.
2. If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and
replaced.
3. When the plastic is no longer needed, it shall be completely removed.
D.2.1.2.5 STRAW WATTLES
Code: SW Symbol:
Purpose
Wattles are erosion and sediment control barriers consisting of straw wrapped in biodegradable tubular
plastic or similar encasing material. Wattles may reduce the velocity and can spread the flow of rill and
sheet runoff, and can capture and retain sediment. Straw wattles are typically 8 to 10 inches in diameter
and 25 to 30 feet in length. The wattles are placed in shallow trenches and staked along the contour of
disturbed or newly constructed slopes.
Conditions of Use
1. Install on disturbed areas that require immediate erosion protection.
2. Use on slopes requiring stabilization until permanent vegetation can be established.
3. Can be used along the perimeter of a project, as a check dam in unlined ditches and around temporary
stockpiles
4. Wattles can be staked to the ground using willow cuttings for added revegetation.
5. Rilling can occur beneath and between wattles if not properly entrenched, allowing water to pass
below and between wattles
Design and Installation Specifications
1. It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope
contour.
2. Narrow trenches should be dug across the slope, on contour, to a depth of 3 to 5 inches on clay soils
and soils with gradual slopes. On loose soils, steep slopes, and during high rainfall events, the trenches
should be dug to a depth of 5 to 7 inches, or ½ to 2/3 of the thickness of the wattle.
3. Start construction of trenches and installing wattles from the base of the slope and work uphill.
Excavated material should be spread evenly along the uphill slope and compacted using hand tamping
or other method. Construct trenches at contour intervals of 3 to 30 feet apart depending on the
steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches
should be constructed. Vertical distance between wattles is not to exceed 10 feet.
4. Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends.
5. Install stakes at each end of the wattle, and at 4 foot centers along the entire length of the wattle.
6. If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and
into the soil.
7. At a minimum, wooden stakes should be approximately ¾ x ¾ x 24 inches. Willow cuttings or
3/8 inch rebar can also be used for stakes.
8. Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding
above the wattle.
D.2.1 ESC MEASURES
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D-21
Maintenance Standards
1. Inspect wattles prior to forecasted rain, daily during extended rain events, after rain events, weekly
during the wet season, and at two week intervals at all other times of the year.
2. Repair or replace split, torn, raveling, or slumping wattles
3. Remove sediment accumulations when exceeding ½ the height between the top of the wattle and the
ground surface.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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FIGURE D.2.1.2.E STRAW WATTLES
1. STRAW ROLL INSTALLATION REQUIRES THE PLACEMENT AND SECURE STAKING
OF THE ROLL IN A TRENCH, 3" x 5" (75-125mm) DEEP, DUG ON CONTOUR.
2. RUNOFF MUST NOT BE ALLOWED TO RUN UNDER OR AROUND ROLL.
ROLL SPACING DEPENDS ON SOIL
TYPE AND SLOPE STEEPNESS
STRAW ROLLS MUST BE PLACED
ALONG SLOPE CONTOURS
3'-4'
1.2m)
10'-25'
3-8m)
3"-5"
75-125mm)
ADJACENT ROLLS
SHALL TIGHTLY ABUT
SEDIMENT, ORGANIC MATTER,
AND NATIVE SEEDS ARE
CAPTURED BEHIND THE ROLLS
LIVE STAKE
1" x 1" STAKE
8"-10" DIA.
200-250mm)
NOTES:
STRAW WATTLES
NTS
D.2.1 ESC MEASURES
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D-23
D.2.1.2.6 TEMPORARY AND PERMANENT SEEDING
Code: SE Symbol:
Purpose
Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is
one of the most effective methods of reducing erosion.
Conditions of Use
1. Seeding shall be used throughout the project on disturbed areas that have reached final grade or that
will remain unworked for more than 30 days.
2. Vegetation-lined channels shall be seeded. Channels that will be vegetated should be installed before
major earthwork and hydroseeded or covered with a Bonded Fiber Matrix (BFM).
3. Retention/detention ponds shall be seeded as required.
4. At the City’s discretion, seeding without mulch during the dry season is allowed even though it will
take more than seven days to develop an effective cover. Mulch is, however, recommended at all
times because it protects seeds from heat, moisture loss, and transport due to runoff.
5. Prior to the beginning of the wet season, all disturbed areas shall be reviewed to identify which ones
can be seeded in preparation for the winter rains (see Section D.2.4.2). Disturbed areas shall be seeded
within one week of the beginning of the wet season. A sketch map of those areas to be seeded and
those areas to remain uncovered shall be submitted to the CED inspector. The CED inspector may
require seeding of additional areas in order to protect surface waters, adjacent properties, or drainage
facilities.
6. At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be seeded and
mulched (see Section D.2.4.5).
Design and Installation Specifications
1. The best time to seed is fall (late September to October) or in spring (mid-March to June). Irrigation
is required during the first summer following installation if seeding occurs in spring or summer or
during prolonged dry times of year. Areas may also be seeded during the winter months, but it may
take additional spring seeding applications to develop a dense groundcover due to cold temperatures.
The application and maintenance of mulch is critical for winter seeding.
2. To prevent seed from being washed away, confirm that all required surface water control measures
have been installed.
3. The seedbed should not be compacted because soils that are well compacted will not vegetate as
quickly or thoroughly. Slopes steeper than 3H:1V shall be surface roughened. Roughening can be
accomplished in a variety of ways, but the typical method is track walking, or driving a crawling
tractor up and down the slope, leaving cleat imprints parallel to the slope contours.
4. In general, 10-20-20 N-P-K (nitrogen-phosphorus-potassium) fertilizer may be used at a rate of
90 pounds per acre. Slow-release fertilizers are preferred because they are more efficient and have
fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct
soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over-
application of fertilizer. Disturbed areas within 200 feet of water bodies and wetlands must use slow-
release low-phosphorus fertilizer (typical proportions 3-1-2 N-P-K).
5. The following requirements apply to mulching:
a) Mulch is always required for seeding slopes greater than 3H:1V (see Section D.2.1.2.2).
b) If seeding during the wet season, mulch is required.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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c) The use of mulch may be required during the dry season at the City’s discretion if grass growth is
expected to be slow, the soils are highly erodible due to soil type or gradient, there is a water body
close to the disturbed area, or significant precipitation (see Section D.2.4.2) is anticipated before
the grass will provide effective cover.
d) Mulch may be applied on top of the seed or simultaneously by hydroseeding.
6. Hydroseeding is allowed as long as tackifier is included. Hydroseeding with wood fiber mulch is
adequate during the dry season. Application of hydroseeded wood fiber mulch should be appropriate
for slope angle. Follow manufacturer specifications for application rates.
7. Areas to be permanently landscaped shall use soil amendments. Good quality topsoil shall be tilled
into the top six inches to reduce the need for fertilizer and improve the overall soil quality. Most
native soils will require the addition of four inches of well-rotted compost to be tilled into the soil to
provide a good quality topsoil. Compost used should meet specifications provided in Reference
Section 11-C of the SWDM.
8. The seed mixes listed below include recommended mixes for both temporary and permanent seeding.
These mixes, with the exception of the wetland mix, shall be applied at a rate of 80 to 100 seeds per
square foot. Wet sites should apply 120 to 150 seeds per square foot. Local suppliers should be
consulted for information on current Pure Live Seed (PLS) rates and species specific seeds per pound
in order to determine seed mix PLS pounds of seed per acre. The appropriate mix depends on a variety
of factors, including exposure, soil type, slope, and expected foot traffic. Alternative seed mixes
approved by the City may be used.
Table D.2.1.2.B presents the standard mix for those areas where temporary or permanent vegetative cover
is required. The following mix assumes a desired 150 seeds per square foot and should be applied at
approximately 37 pounds of pure live seed per acre.
TABLE D.2.1.2.B EROSION CONTROL SEED MIX
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
Spike bentgrass/Agrostis exarata 6 9 0.1
California brome/Bromus carinatus 15 23 9.8
Tufted hairgrass/Deschampsia cespitosa 15 23 0.4
Blue wildrye/Elymus glaucus 18 27 10.7
California oatgrass/Danthonia californica 18 27 5.6
Native red fescue/Festuca rubra var. rubra 18 27 2.4
Meadow barley/Hordeum brachyantherum 10 15 7.7
Table D.2.1.2.C provides just one recommended possibility for landscaping seed. It assumes a desired
100 seeds per square foot and should be applied at 18 pounds of pure live seed per acre.
TABLE D.2.1.2.C LANDSCAPING SEED MIX
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
Sideoats grama/Bouteloua curtipendula 20 30 6.8
California oatgrass/Danthonia californica 20 30 6.2
Native red fescue/Festuca rubra var. rubra 30 45 3.9
Prairie junegrass/Koeleria macrantha 30 45 0.8
D.2.1 ESC MEASURES
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D-25
This turf seed mix in Table D.2.1.2.D is for dry situations where there is no need for much water. The
advantage is that this mix requires very little maintenance.
TABLE D.2.1.2.D LOW-GROWING TURF SEED MIX
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
Hard fescue/Festuca brevipila 25 20 1.5
Sheep fescue/Festuca ovina 30 24 1.5
Native red fescue/Festuca rubra var. rubra 25 20 1.7
Prairie junegrass/Koeleria macrantha 20 16 0.3
Table D.2.1.2.E presents a mix recommended for bioswales and other intermittently wet areas. The mix
assumes a desired 150 seeds per square foot and approximately 29 pounds of pure live seed per acre. Sod
shall generally not be used for bioswales because the seed mix is inappropriate for this application. Sod
may be used for lining ditches to prevent erosion, but it will provide little water quality benefit during the
wet season.
TABLE D.2.1.2.E BIOSWALE SEED MIX
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
American sloughgrass/Beckmannia
syzigachne 15 23 0.9
Tufted hairgrass/Deschampsia cespitosa 20 30 0.5
Blue wildrye/Elymus glaucus 18 27 10.7
Native red fescue/Festuca rubra var. rubra 20 30 2.6
Meadow barley/Hordeum brachyantherum 12 18 9.2
Northwestern mannagrass/Glyceria
occidentalis 15 23 4.9
The seed mix shown in Table D.2.1.2.F is a recommended low-growing, non-invasive seed mix
appropriate for very wet areas that are not regulated wetlands (if planting in wetland areas, see
Section 6.3.1 of the SWDM). Other mixes may be appropriate, depending on the soil type and hydrology of
the area. This mixture assumes a target goal of 150 seeds per square foot and should be applied at a rate of
36 pounds per acre.
TABLE D.2.1.2.F WET AREA SEED MIX*
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
California brome/Bromus carinatus 15 23 9.8
Columbia brome/Bromus vulgaris 18 27 8.1
Tufted hairgrass/Deschampsia cespitosa 15 23 0.4
California oatgrass/Danthonia californica 15 23 4.7
Native red fescue/Festuca rubra var. rubra 17 26 2.2
Western manna grass/Glyceria
occidentalis
10 15 3.3
Meadow barley/Hordeum brachyantherum 10 15 7.7
Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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The meadow seed mix in Table D.2.1.2.G is recommended for areas that will be maintained infrequently
or not at all and where colonization by native plants is desirable. Likely applications include rural road and
utility right-of-way. Seeding should take place in September or very early October in order to obtain
adequate establishment prior to the winter months. This seed mix assumes a target goal of 120 seeds per
square foot and an application rate of 23 pounds of pure live seed per acre.
TABLE D.2.1.2.G MEADOW SEED MIX
Common Name/Latin Name
Species
Composition
Desired Seeds
per
Square Foot
PLS
Pounds/Acre
Common yarrow/Achillea millefolium 4 5 0.1
Pearly everlasting/Anaphalis margartacae 1 1 0.0
California brome/Bromus carinatus 15 18 7.8
California oatgrass/Danthonia californica 15 18 3.7
Blue wildrye/Elymus glaucus 16 19 7.6
Festuca idahoensis 15 18 1.7
Native red fescue/Festuca rubra var. rubra 18 22 1.9
Sickle keeled lupine/Lupinus albicaulis 1 1 2.2
Fowl bluegrass/Poa palustris 15 18 0.4
Maintenance Standards for Temporary and Permanent Seeding
1. Any seeded areas that fail to establish at least 80 percent cover within one month shall be reseeded. If
reseeding is ineffective, an alternate method, such as sodding or nets/blankets, shall be used. If winter
weather prevents adequate seed establishment and growth, this time limit may be relaxed at the
discretion of the City when critical areas would otherwise be protected.
2. After adequate cover is achieved, any areas that experience erosion shall be re-seeded and protected
by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area re-
seeded and protected by mulch.
3. Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes
runoff.
D.2.1.2.7 SODDING
Code: SO Symbol:
Purpose
The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize
drainage ways where concentrated overland flow will occur.
Conditions of Use
Sodding may be used in the following areas:
1. Disturbed areas that require short-term or long-term cover
2. Disturbed areas that require immediate vegetative cover
3. All waterways that require vegetative lining (except biofiltration swales—the seed mix used in most
sod is not appropriate for biofiltration swales). Waterways may also be seeded rather than sodded, and
protected with a net or blanket (see Section D.2.1.2.3).
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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Provide immediate temporary protection from erosion by protecting soil from rainfall and slowing
flow velocity over the soil surface.
Enhance temporary or permanent plant establishment by conserving moisture, holding seed and
topsoil in place, providing nutrients and soil microorganisms, and moderating soil temperatures.
Compost blankets, applied at the proper thickness and tilled into the soil, are also an option for
amending soils for permanent landscaping.
Compost generally releases and adds phosphorous to stormwater. Therefore, compost blankets are not
recommended for use in watersheds where phosphorous sensitive water resources are located. Unless
prior approval is given by the City, they should not be used in Sensitive Lake Watersheds.
Conditions of Use
1. Compost blankets may be used unseeded on disturbed areas that require temporary cover measures up
to 1 year. Compost applied as temporary cover may be reclaimed and re-used for permanent cover.
2. Compost provides cover for protecting final grades until landscaping can be completed as it can be
directly seeded or tilled into soil as an amendment.
3. Compost blankets meet mulch requirements for seed.
4. Seed may be applied to a compost blanket at any time for permanent or temporary stabilization of
disturbed areas. Seed may be applied prior to blanket application, on top of blankets, or injected and
mixed into the compost as it is applied.
5. Compost blankets may be applied on slopes up to 2H:1V.
Design and Installation Specifications
1. Compost shall be applied at a minimum of 2 inches thick, unless otherwise directed by an ESC
supervisor or the City. At an application of 2 inches, this will equal approximately 100 tons per acre
compost generally weighs approximately 800 lbs per cubic yard). Thickness shall be increased at the
direction of the design engineer for disturbed areas in or near critical areas or other areas highly
susceptible to erosion.
2. Compost shall meet criteria in Reference Section 11-C of the SWDM.
3. Compost shall be obtained from a supplier meeting the requirements in Reference Section 11-C.
4. Compost blankets shall be applied over the top of the slope to which it is applied, to prevent water
from running under the blanket
5. Compost blankets shall not be used in areas exposed to concentrated flow (e.g., channels, ditches,
dikes)
Maintenance Standards
1. The specified thickness of the blanket/cover must be maintained.
2. Any areas that show signs of erosion must be re-mulched. If the erosion problem is drainage related,
then the drainage problem must first be remedied and then the eroded area re-mulched.
D.2.1.3 PERIMETER PROTECTION
Perimeter protection to filter sediment from sheetwash shall be located downslope of all disturbed areas
and shall be installed prior to upslope grading. Perimeter protection includes the use of vegetated strips as
well as, constructed measures, such as silt fences, fiber rolls, sand/gravel barriers, brush or rock filters,
triangular silt dikes and other methods. During the wet season, 50 linear feet of silt fence (and the
necessary stakes) per acre of disturbed area must be stockpiled on site.
Purpose: The purpose of perimeter protection is to reduce the amount of sediment transported beyond the
disturbed areas of the construction site. Perimeter protection is primarily a backup means of sediment
control. Most, if not all, sediment-laden water is to be treated in a sediment trap or pond. The only
D.2.1 ESC MEASURES
2022 City of Renton Surface Water Design Manual 6/22/2022
D-31
circumstances in which perimeter control is to be used as a primary means of sediment removal is when
the catchment is very small (see below).
When to Install: Perimeter protection is to be installed prior to any upslope clearing and grading.
Measures to Use: The above measures may be used interchangeably and are not the only perimeter
protection measures available. If surface water is collected by an interceptor dike or swale and routed to a
sediment pond or trap, there may be no need for the perimeter protection measures specified in this
section.
Criteria for Use as Primary Treatment: At the boundary of a site, perimeter protection may be used as
the sole form of treatment when the flowpath meets the criteria listed below. If these criteria are not met,
perimeter protection shall only be used as a backup to a sediment trap or pond.
Average Slope Slope Percent Flowpath Length
1.5H:1V or less 67% or less 100 feet
2H:1V or less 50% or less 115 feet
4H:1V or less 25% or less 150 feet
6H:1V or less 16.7% or less 200 feet
10H:1V or less 10% or less 250 feet
D.2.1.3.1 SILT FENCE
Code: SF Symbol:
Purpose
Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a
temporary physical barrier to sediment and reducing the runoff velocities of overland flow.
Conditions of Use
1. Silt fence may be used downslope of all disturbed areas.
2. Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of
overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment
trap or pond. The only circumstance in which overland flow may be treated solely by a silt fence,
rather than by a sediment trap or pond, is when the area draining to the fence is small (see “Criteria for
Use as Primary Treatment” in Section D.2.1.3 above).
Design and Installation Specifications
1. See Figure D.2.1.3.A and Figure D.2.1.3.B for details.
2. The geotextile used must meet the standards listed below. A copy of the manufacturer’s fabric
specifications must be available on site.
AOS (ASTM D4751) 30–100 sieve size (0.60–0.15 mm) for slit film
50–100 sieve size (0.30–0.15 mm) for other fabrics
Water Permittivity (ASTM D4491) 0.02 sec-1 minimum
Grab Tensile Strength (ASTM D4632)
see Specification Note 3)
180 lbs. min. for extra strength fabric
100 lbs. min. for standard strength fabric
Grab Tensile Elongation (ASTM D4632) 30% max. (woven)
Ultraviolet Resistance (ASTM D4355) 70% min.
3. Standard strength fabric requires wire backing to increase the strength of the fence. Wire backing or
closer post spacing may be required for extra strength fabric if field performance warrants a stronger
fence.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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4. Where the fence is installed, the slope shall be no steeper than 2H:1V.
5. If a typical silt fence (per Figure D.2.1.3.A) is used, the standard 4 x 4 trench may be reduced as long
as the bottom 8 inches of the silt fence fabric is well buried and secured in a trench that stabilizes the
fence and does not allow water to bypass or undermine the silt fence.
Maintenance Standards
1. Any damage shall be repaired immediately.
2. If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a
sediment trap or pond.
3. It is important to check the uphill side of the fence for signs of the fence clogging and acting as a
barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the
fence or remove the trapped sediment.
4. Sediment must be removed when the sediment is 6 inches high.
5. If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced.
D.2.1 ESC MEASURES
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D-33
FIGURE D.2.1.3.A SILT FENCE
2"X2" BY 14 Ga. WIRE OR
EQUIVALENT, IF STANDARD
STRENGTH FABRIC USED
NOTE: FILTER FABRIC FENCES
SHALL BE INSTALLED ALONG
CONTOURS WHENEVER POSSIBLE
JOINTS IN FILTER FABRIC SHALL BE SPLICED
AT POSTS. USE STAPLES, WIRE RINGS OR
EQUIVALENT TO ATTACH FABRIC TO POSTS.
FILTER FABRIC
BACKFILL TRENCH WITH NATIVE SOIL
OR 3/4" TO 1-1/2" WASHED GRAVEL
MINIMUM 4"x4" TRENCH
2"x4" WOOD POSTS, STEEL FENCE
POSTS, REBAR, OR EQUIVALENT
POST SPACING MAY BE
INCREASED TO 8' IF
WIRE BACKING IS USED
6' MAX.
2'
MIN
12
M
IN
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D-34
FIGURE D.2.1.3.B SILT FENCE INSTALLATION BY SLICING
1. GATHER FABRIC AT POSTS, IF NEEDED.
2. UTILIZE THREE TIES PER POST, ALL
WITHIN TOP 8" OF FABRIC.
3. POSITION EACH TIE DIAGONALLY,
PUNCTURING HOLES VERTICALLY A
MINIMUM OF 1" APART.
4. HANG EACH TIE ON A POST NIPPLE AND
TIGHTEN SECURELY. USE CABLE TIES
50 LBS) OF SOFT WIRE.
TOP OF FABRIC
BELT
DIAGONAL ATTACHMENT
DOUBLES STRENGTH
FLOW
ST
E
E
L
S
U
PPO
R
T
P
O
S
T
1. POST SPACING: 7' MAX. ON OPEN RUNS
4' MAX. ON POOLING AREAS.
2. POST DEPTH: AS MUCH BELOW GROUND
AS FABRIC ABOVE GROUND.
3. PONDING HEIGHT MAX. 24" ATTACH
FABRIC TO UPSTREAM SIDE OF POST.
4. DRIVE OVER EACH SIDE OF SILT FENCE
2 TO 4 TIMES WITH DEVICE EXERTING
60 P.S.I. OR GREATER.
5. NO MORE THAN 24" OF A 36" FABRIC
IS ALLOWED ABOVE GROUND.
6. VIBRATORY PLOW IS NOT ACCEPTABLE
BECAUSE OF HORIZONTAL COMPACTION.
100% COMPACTION
EACH SIDE
OPERATION
ROLL OF SILT FENCE
PLOW
FABRIC ABOVE
GROUND
HORIZONTAL CHISEL POINT
76 mm WIDTH)200-300mm
SILT FENCE
TOP 8"
NOTES:
ATTACHMENT DETAILS:
SILT FENCE INSTALLATION BY SLICING METHOD
NTS
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D.2.1.3.3 VEGETATED STRIP
Code: VS Symbol:
Purpose
Vegetated strips reduce the transport of coarse sediment from a construction site by providing a temporary
physical barrier to sediment and reducing the runoff velocities of overland flow.
Conditions of Use
1. Vegetated strips may be used downslope of all disturbed areas.
2. Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial
amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a
sediment trap or pond. The only circumstance in which overland flow may be treated solely by a strip,
rather than by a sediment trap or pond, is when the area draining to the strip is small (see “Criteria for
Use as Primary Treatment” in Section D.2.1.3).
Design and Installation Specifications
1. The vegetated strip shall consist of a 25-foot minimum width continuous strip of dense vegetation
with a permeable topsoil. Grass-covered, landscaped areas are generally not adequate because the
volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native
growth with a well-developed soil that allows for infiltration of runoff.
2. The slope within the strip shall not exceed 4H:1V.
3. The uphill boundary of the vegetated strip shall be delineated with clearing limits as specified in
Section D.2.1.1.
Maintenance Standards
1. Any areas damaged by erosion or construction activity shall be seeded immediately and protected by
mulch.
2. If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded,
sod must be installed using the standards for installation found in Section D.2.1.2.7.
If there are indications that concentrated flows are traveling across the buffer, surface water controls must
be installed to reduce the flows entering the buffer, or additional perimeter protection must be installed.
D.2.1.3.4 TRIANGULAR SILT DIKE (GEOTEXTILE ENCASED CHECK DAM)
Code: TSD Symbol:
Purpose
Triangular silt dikes (TSDs) may be used as check dams, for perimeter protection, for temporary soil
stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Silt dikes, if attached to
impervious surfaces with tack or other adhesive agent may also be used as temporary wheel wash areas, or
concrete washout collection areas.
Conditions of Use
1. May be used for temporary check dams in ditches.
2. May be used on soil or pavement with adhesive or staples.
3. TSDs have been used to build temporary sediment ponds, diversion ditches, concrete washout
facilities, curbing, water bars, level spreaders, and berms.
D.2.1 ESC MEASURES
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3. Any damage to berms must be repaired immediately. Damage includes flattening, compacting, rills,
eroded areas due to overtopping.
4. If concentrated flows are evident uphill of the berm, the flows must be intercepted and conveyed to a
sediment trap or pond.
5. The uphill side of the berm shall be inspected for signs of the berm clogging and acting as a barrier to
flows and causing channelization of flows parallel to the berm. If this occurs, replace the berm or
remove the trapped sediment.
6. Sediment that collects behind the berm must be removed when the sediment is more than 6 inches
deep.
D.2.1.3.6 COMPOST SOCKS
Code: COSO Symbol:
Purpose
Compost socks reduce the transport of sediment from a construction site by providing a temporary
physical barrier to sediment-laden water and reducing the runoff velocities of overland flow. Compost
socks trap sediment by filtering water that passes through the sock and allows water to pond behind the
sock, creating a settling area for solids. Organic materials in the compost also may reduce metal and
petroleum hydrocarbon concentrations in construction runoff. Compost socks function similarly to
compost berms; however, because the compost is contained in a mesh tube, they are appropriate for both
concentrated flow and sheet flow. Compost socks may be used to channel concentrated flow on hard
surfaces.
Conditions of Use
1. Compost socks may be used in areas requiring sediment or erosion control where runoff is in the form
of sheet flow or in areas that silt fence is normally considered acceptable. Compost socks may also be
used in sensitive environmental areas where migration of aquatic life, including turtles, salamanders
and other aquatic life may be impeded by the used of silt fence.
2. Compost socks are not intended to treat substantial amounts of overland flow. However, compost
socks may be subjected to some ponding and concentrated flows. If intended primarily as a filtration
device, the socks should be sized and placed so that flows do not overtop the socks.
3. For purposes of long term sediment control objectives, compost socks may be seeded at the time of
installation to create an additional vegetated filtering component.
Design and Installation Specifications
1. Compost socks shall be produced using a pneumatic blower hose or equivalent to fill a mesh tube with
compost to create a uniform cross-section and berm density.
2. Socks shall be filled so they are firmly – packed yet flexible. Upon initial filling, the socks shall be
filled to have a round cross-section. Once placed on the ground, it is recommended to apply weight to
the sock to improve contact with the underlying surface. This may cause the sock to assume an oval
shape.
3. Compost socks shall be a minimum of 8 inches in diameter. Larger diameter socks are recommended
for areas where ponding is expected behind the sock.
4. Compost socks shall not be used on slopes greater than 2H:1V.
5. Compost shall meet criteria in Reference Section 11-C of the SWDM, except for the particle size
distribution (see Bullet 7).
6. Compost shall be obtained from a supplier meeting the requirements in Reference Section 11-C.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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7. Compost particle size distribution shall be as follows: 99% passing a 1-inch sieve, 90% passing a
3/4-inch sieve and a minimum of 70% greater than the 3/8-inch sieve. A total of 98% shall not exceed
3 inches in length.
8. In order to prevent water from flowing around the ends of compost socks, the ends must be pointed
upslope so the ends of the socks are at a higher elevation than the remainder of the sock.
Maintenance Standards
1. Compost socks shall be regularly inspected to make sure the mesh tube remains undamaged, the socks
retain their shape, and allow adequate flow through of surface water. If the mesh tube is torn, it shall
be repaired using twine, zip-ties, or wire. Large sections of damaged socks must be replaced. Any
damage must be repaired immediately upon discovery of damage.
2. When the sock is no longer needed, the socks shall be cut open and the compost dispersed to be
incorporated into the soil or left on top of the soil for final seeding to occur. The mesh material must
be disposed of properly as solid waste. If spills of oil, antifreeze, hydraulic fluid, or other equipment
fluids have occurred that have saturated the sock, the compost must be disposed of properly as a
waste.
3. Sediment must be removed when sediment accumulations are within 3 inches of the top of the sock.
D.2.1.4 TRAFFIC AREA STABILIZATION
Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize
erosion and tracking of sediment off site. Stabilized construction entrances shall be installed as the first
step in clearing and grading. At the City’s discretion, road and parking area stabilization is not required
during the dry season (unless dust is a concern) or if the site is underlain by coarse-grained soils. Roads
and parking areas shall be stabilized immediately after initial grading.
Purpose: The purpose of traffic area stabilization is to reduce the amount of sediment transported off site
by construction vehicles and to reduce the erosion of areas disturbed by vehicle traffic. Sediment
transported off site onto paved streets is a significant problem because it is difficult to effectively remove,
and any sediment not removed ends up in the drainage system. Additionally, sediment on public right-of-
way can pose a serious traffic hazard. Construction road and parking area stabilization is important
because the combination of wet soil and heavy equipment traffic typically forms a slurry of easily erodible
mud. Finally, stabilization also is an excellent form of dust control in the summer months.
When to Install: The construction entrance is to be installed as the first step in clearing and grading.
Construction road stabilization shall occur immediately after initial grading of the construction roads and
parking areas.
Measures to Use: There are two types of traffic area stabilization: (1) a stabilized construction entrance
and (2) construction road/parking area stabilization. Both measures must be used as specified under
Conditions of Use” for each measure.
D.2.1.4.1 STABILIZED CONSTRUCTION ENTRANCE
Code: CE Symbol:
Purpose
Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by
motor vehicles or runoff by constructing a stabilized pad of quarry spalls at entrances to construction sites.
D.2.1 ESC MEASURES
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Conditions of Use
Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling
on paved roads or other paved areas within 1,000 feet of the site. Access and exits shall be limited to one
route if possible, or two for linear projects such as roadway where more than one access/exit is necessary
for maneuvering large equipment.
For residential construction provide stabilized construction entrances for each residence in addition to the
main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle
access/parking, based on lot size/configuration.
Design and Installation Specifications
1. See Figure D.2.1.4.A for details.
2. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into
the rock pad. The geotextile shall meet the following standards:
Grab Tensile Strength (ASTM D4632) 200 lbs min.
Grab Tensile Elongation (ASTM D4632) 30% max.(woven)
Puncture Strength (ASTM D6241) 495 lbs min.
AOS (ASTM D4751) 20–45 (U.S. standard sieve size)
3. Do not use crushed concrete, cement, or calcium chloride for construction entrance stabilization
because these products raise pH levels in stormwater and concrete discharge to surface waters of the
State is prohibited.
4. Hog fuel (wood based mulch) may be substituted for or combined with quarry spalls in areas that will
not be used for permanent roads. The effectiveness of hog fuel is highly variable, but it has been used
successfully on many sites. It generally requires more maintenance than quarry spalls. Hog fuel is not
recommended for entrance stabilization in urban areas. The inspector may at any time require the use
of quarry spalls if the hog fuel is not preventing sediment from being tracked onto pavement or if the
hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent roadbeds because
organics in the subgrade soils cause difficulties with compaction.
5. Fencing (see Section D.2.1.1) shall be installed as necessary to restrict traffic to the construction
entrance.
6. Whenever possible, the entrance shall be constructed on a firm, compacted subgrade. This can
substantially increase the effectiveness of the pad and reduce the need for maintenance.
Maintenance Standards
1. Quarry spalls (or hog fuel) shall be added if the pad is no longer in accordance with the specifications.
2. If the entrance is not preventing sediment from being tracked onto pavement, then alternative
measures to keep the streets free of sediment shall be used. This may include street sweeping, an
increase in the dimensions of the entrance, or the installation of a wheel wash. If washing is used, it
shall be done on an area covered with crushed rock, and wash water shall drain to a sediment trap or
pond.
3. Any sediment that is tracked onto pavement shall be removed immediately by sweeping. The sediment
collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by
washing down the street, except when sweeping is ineffective and there is a threat to public safety. If
it is necessary to wash the streets, a small sump must be constructed. The sediment would then be
washed into the sump where it can be controlled. Wash water must be pumped back onto the site and
cannot discharge to systems tributary to surface waters.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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4. Any quarry spalls that are loosened from the pad and end up on the roadway shall be removed
immediately.
5. If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see
Section D.2.1.1) shall be installed to control traffic.
FIGURE D.2.1.4.A SCHEMATIC REPRESENTATION OF A STABILIZED CONSTRUCTION ENTRANCE
D.2.1.4.2 CONSTRUCTION ROAD/PARKING AREA STABILIZATION
Code: CRS Symbol:
Purpose
Stabilizing subdivision roads, parking areas and other onsite vehicle transportation routes immediately
after grading reduces erosion caused by construction traffic or runoff.
Conditions of Use
1. Roads or parking areas shall be stabilized wherever they are constructed, whether permanent or
temporary, for use by construction traffic.
2. Fencing (see Section D.2.1.1) shall be installed, if necessary, to limit the access of vehicles to only
those roads and parking areas that are stabilized.
Design and Installation Specifications
1. A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be
applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATB)
may also be used, or the road/parking area may be paved. It may also be possible to use cement or
PER KING COUNTY ROAD DESIGN AND CONSTRUCTION STANDARDS (KCRDCS), DRIVEWAYS SHALL
BE PAVED TO EDGE OF R-O-W PRIOR TO INSTALLATION OF THE CONSTRUCTION ENTRANCE TO
AVOID DAMAGING OF THE ROADWAY.
IT IS RECOMMENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE PAD.
12" MIN.
THICKNESS
PROVIDE FULL WIDTH OF
INGRESS/EGRESS AREA
IF A ROADSIDE DITCH IS
PRESENT, INSTALL
DRIVEWAY CULVERT
PER KCRDCS
GEOTEXTILE
4"- 8" QUARRY
SPALLS
R=25' MIN.100'
MIN.
E X I S T IN G R O A D
1 5 ' M I N .
NOTES:
D.2.1 ESC MEASURES
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calcium chloride for soil stabilization. If the area will not be used for permanent roads, parking areas,
or structures, a 6-inch depth of hog fuel may also be used, but this is likely to require more
maintenance. Whenever possible, construction roads and parking areas shall be placed on a firm,
compacted subgrade. Note: If the area will be used for permanent road or parking installation later in
the project, the subgrade will be subject to inspection.
2. Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain
transversely. Drainage ditches shall be provided on each side of the roadway in the case of a crowned
section, or on one side in the case of a super-elevated section. Drainage ditches shall be designed in
accordance with the standards given in Section D.2.1.6.4 and directed to a sediment pond or trap.
3. Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet-flows
into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this
area has at least 50 feet of vegetation, then it is generally preferable to use the vegetation to treat
runoff, rather than a sediment pond or trap. The 50 feet shall not include vegetated wetlands. If runoff
is allowed to sheet flow through adjacent vegetated areas, it is vital to design the roadways and
parking areas so that no concentrated runoff is created.
4. In order to control construction traffic, the City may require that signs be erected on site informing
construction personnel that vehicles, other than those performing clearing and grading, are restricted
to stabilized areas.
5. If construction roads do not adequately reduce trackout to adjacent property or roadways, a wheel
wash system will be required.
Maintenance Standards
Crushed rock, gravel base, hog fuel, etc., shall be added as required to maintain a stable driving surface
and to stabilize any areas that have eroded.
D.2.1.4.3 WHEEL WASH
Code: WW Symbol:
Purpose
Wheel wash systems reduce the amount of sediment transported onto paved roadways and into surface
water systems by construction vehicles.
Conditions of Use
When a stabilized construction entrance is not preventing sediment from being tracked onto pavement:
Wheel washing is generally an effective erosion and sediment control method and BMP when
installed with careful attention to topography. For example, a wheel wash can be detrimental if
installed at the top of a slope abutting a right-of-way where the water from the dripping truck wheels
and undercarriage can run unimpeded into the street.
Pressure washing combined with an adequately sized and properly surfaced wash pad with direct
drainage discharge to a large 10-foot x 10-foot sump can be very effective.
Design and Installation Specifications
A suggested detail is shown in Figure D.2.1.4.B.
1. A minimum of 6 inches of asphalt treated base (ATB) over crushed base material or 8 inches over a
good subgrade is recommended to pave the wheel wash area.
2. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will
work well to test clearance.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D-46
D.2.1.5 SEDIMENT RETENTION
Surface water collected from disturbed areas of the site shall be routed through a sediment pond or trap
prior to release from the site. An exception is for areas at the perimeter of the site with drainage areas
small enough to be treated solely with perimeter protection (see Section D.2.1.3). Also, if the soils and
topography are such that no offsite discharge of surface water is anticipated up to and including the
developed 2-year runoff event, sediment ponds and traps are not required. A 10-year peak flow using the
approved model with 15-minute time steps shall be used for sediment pond/trap sizing if the project size,
expected timing and duration of construction, or downstream conditions warrant a higher level of
protection (see below). At the City’s discretion, sites may be worked during the dry season without
sediment ponds and traps if there is some other form of protection of surface waters, such as a 100-foot
forested buffer between the disturbed areas and adjacent surface waters. For small sites, use the criteria
defined in Section D.2.1.3, Perimeter Protection to determine minimum flow path length. If the site work
has to be extended into the wet season, a back-up plan must be identified in the CSWPP plan and
implemented. Protection of catch basins is required for inlets that are likely to be impacted by sediment
generated by the project and that do not drain to an onsite sediment pond or trap. Sediment retention
facilities shall be installed prior to grading of any contributing area and shall be located so as to avoid
interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages.
Purpose: The purpose of sediment retention facilities is to remove sediment from runoff generated from
disturbed areas.
When to Install: The facilities shall be constructed as the first step in the clearing and grading of the site.
The surface water conveyances may then be connected to the facilities as site development proceeds.
Measures to Use: There are three sediment retention measures in this section. The first two, sediment
traps and ponds, serve the same function but for different size catchments. All runoff from disturbed areas
must be routed through a trap or pond except for very small areas at the perimeter of the site small enough
to be treated solely with perimeter protection (see Section D.2.1.3). The third measure is for catch basin
protection. It is only to be used in limited circumstances and is not a primary sediment treatment facility. It
is only intended as a backup in the event of failure of other onsite systems.
Use of Permanent Drainage Facilities: All projects that are constructing permanent facilities for runoff
quantity control are strongly encouraged to use the rough-graded or final-graded permanent facilities for
ponds and traps. This includes combined facilities and infiltration facilities. When permanent facilities are
used as temporary sedimentation facilities, the surface area requirements of sediment traps (for drainages
less than 3 acres) or sediment ponds (more than 3 acres) must be met. If the surface area requirements are
larger than the surface area of the permanent facility, then the pond shall be enlarged to comply with the
surface area requirement. The permanent pond shall also be divided into two cells as required for sediment
ponds. Either a permanent control structure or the temporary control structure described in Section
D.2.1.5.2 may be used. If a permanent control structure is used, it may be advisable to partially restrict the
lower orifice with gravel to increase residence time while still allowing dewatering of the pond.
If infiltration facilities are to be used, the sides and bottom of the facility must only be rough excavated to
a minimum of three feet above final grade. Excavation should be done with a backhoe working at “arm’s
length” to minimize disturbance and compaction of the infiltration surface. Additionally, any required
pretreatment facilities shall be fully constructed prior to any release of sediment-laden water to the facility.
Pretreatment and shallow excavation are intended to prevent the clogging of soil with fines. Final grading
of the infiltration facility shall occur only when all contributing drainage areas are fully stabilized (see
Section D.2.4.5).
Selection of the Design Storm: In most circumstances, the developed condition 2-year peak flow using
the approved model with 15-minute time steps is sufficient for calculating surface area for ponds and traps
and for determining exemptions from the sediment retention and surface water collection requirements
Sections D.2.1.5 and D.2.1.6, respectively). In some circumstances, however, the approved model 10-year
15-minute peak flow should be used. Examples of such circumstances include the following:
D.2.1 ESC MEASURES
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D-47
Sites that are within ¼ mile of salmonid streams, wetlands, and designated sensitive lakes such as
Lake Sammamish
Sites where significant clearing and grading is likely to occur during the wet season
Sites with downstream erosion or sedimentation problems.
Natural Vegetation: Whenever possible, sediment-laden water shall be discharged into onsite, relatively
level, vegetated areas. This is the only way to effectively remove fine particles from runoff. This can be
particularly useful after initial treatment in a sediment retention facility. The areas of release must be
evaluated on a site-by-site basis in order to determine appropriate locations for and methods of releasing
runoff. Vegetated wetlands shall not be used for this purpose. Frequently, it may be possible to pump
water from the collection point at the downhill end of the site to an upslope vegetated area. Pumping shall
only augment the treatment system, not replace it because of the possibility of pump failure or runoff
volume in excess of pump capacity.
D.2.1.5.1 SEDIMENT TRAP
Code: ST Symbol:
Purpose
Sediment traps remove sediment from runoff originating from disturbed areas of the site. Sediment traps
are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence,
they usually only result in a small reduction in turbidity.
Conditions of Use
A sediment trap shall be used where the contributing drainage area is 3 acres or less.
Design and Installation Specifications
1. See Figure D.2.1.5.A for details.
2. If permanent runoff control facilities are part of the project, they should be used for sediment retention
see “Use of Permanent Drainage Facilities” in Section D.2.1.5).
3. To determine the trap geometry, first calculate the design surface area (SA) of the trap, measured at the
invert of the weir. Use the following equation:
SA = FS(Q2/Vs)
where Q2 = Design inflow (cfs) from the contributing drainage area based on the developed
condition 2-year or 10-year peak discharge using the approved model with 15-minute
time steps as computed in the hydrologic analysis. The approved model 10-year
15-minute peak flow shall be used if the project size, expected timing and duration of
construction, or downstream conditions warrant a higher level of protection, or if the
pond discharge path leaves the site (note provisions must made to prevent increases
in the existing site conditions 2-year and 10-year runoff peaks discharging from the
project site during construction, see Section D.3.9, Flow Control). If no hydrologic
analysis is required, the Rational Method may be used (Section 3.2.1 of the SWDM).
Vs = The settling velocity (ft/sec) of the soil particle of interest. The 0.02 mm (medium
silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle
of interest and has a settling velocity (Vs) of 0.00096 ft/sec.
FS = A safety factor of 2 to account for non-ideal settling.
Therefore, the equation for computing surface area becomes:
SA = 2 x Q2/0.00096 or 2080 square feet per cfs of inflow
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D-52
FIGURE D.2.1.5.D SEDIMENT POND RISER DETAIL
D.2.1.5.3 STORM DRAIN INLET PROTECTION
Code: FFP or CBI or CBP Symbol: or or
Purpose
Storm drain inlets are protected to prevent coarse sediment from entering storm drainage systems.
Temporary devices around storm drains assist in improving the quality of water discharged to inlets or
catch basins by ponding sediment-laden water. These devices are effective only for relatively small
drainage areas.
Conditions of Use
1. Protection shall be provided for all storm drain inlets downslope and within 500 feet of a disturbed or
construction area, unless the runoff that enters the catch basin will be conveyed to a sediment pond or
trap.
2. Inlet protection may be used anywhere at the applicant’s discretion to protect the drainage system.
This will, however, require more maintenance, and it is highly likely that the drainage system will still
require some cleaning.
3. The contributing drainage area must not be larger than one acre.
Design and Installation Specifications
1. There are many options for protecting storm drain inlets. Two commonly used options are filter
fabric protection and catch basin inserts. Filter fabric protection (see Figure D.2.1.5.E) is filter fabric
geotextile) placed over the grate. This method is generally very ineffective and requires intense
maintenance efforts. Therefore, filter fabric protection is not allowed in the City of Renton. Catch
basin inserts (see Figure D.2.1.5.F) are manufactured devices that nest inside a catch basin. This
method also requires a high frequency of maintenance to be effective.
3.5' MIN.
18" MIN.
2X RISER DIA. MIN.
CORRUGATED
METAL RISER
CONCRETE BASE
ALTERNATIVELY, METAL
STAKES AND WIRE MAY
BE USED TO PREVENT
FLOTATION
DEWATERING ORIFICE,
SCHEDULE 40 STEEL
STUB MIN. DIAMETER
AS PER CALCULATIONS
6" MIN.
PROVIDE
ADEQUATE
STRAPPING
POLYETHYLENE CAP
PERFORATED
DEWATERING DEVICE,
SEE NOTE WATERTIGHT
COUPLING
TACK
WELD
NOTE:
PERFORATED CORRUGATED
POLYETHYLENE (CPE)
DRAINAGE TUBING, DIAMETER
MIN. 2" LARGER THAN
DEWATERING ORIFICE. TUBING
SHALL COMPLY WITH ASTM
F667 AND AASHTO M294.
D.2.1 ESC MEASURES
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D-53
Trapping sediment in the catch basins is unlikely to improve the water quality of runoff if it is treated
in a pond or trap because the coarse particles that are trapped at the catch basin settle out very quickly
in the pond or trap. Catch basin protection normally only improves water quality where there is
no treatment facility downstream. In these circumstances, catch basin protection is an important last
line of defense. It is not, however, a substitute for preventing erosion.
2. It is sometimes possible to construct a small sump around the catch basin before final surfacing of the
road. This is allowed because it can be a very effective method of sediment control.
3. Block and gravel filters, gravel and wire mesh filter barriers, and bag barriers filled with various
filtering media placed around catch basins can be effective when the drainage area is 1 acre or less and
flows do not exceed 0.5 cfs. It is necessary to allow for overtopping to prevent flooding. Many
manufacturers have various inlet protection filters that are very effective in keeping sediment-laden
water from entering the storm drainage system. The following are examples of a few common
methods.
a) Block and gravel filters (Figure D.2.1.5.G) are a barrier formed around an inlet with standard
concrete block and gravel, installed as follows:
Height is 1 to 2 feet above the inlet.
Recess the first row of blocks 2 inches into the ground for stability.
Support subsequent rows by placing a 2x4 through the concrete block opening.
Do not use mortar.
Lay some blocks in the bottom row on their side for dewatering the pooled water.
Place cloth or mesh with ½ inch openings over all block openings.
Place gravel below the top of blocks on slopes of 2:1 or flatter.
An alternate design is a gravel donut.
b) Gravel and wire mesh filters consist of a gravel barrier placed over the top of an inlet. This
structure generally does not provide overflow. Install as follows:
Cloth or comparable wire mesh with ½ inch openings is placed over inlet.
Coarse aggregate covers the cloth or mesh.
Height/depth of gravel should be 1 foot or more, 18 inches wider than inlet on all sides.
c) Curb inlet protection with a wooden weir is a barrier formed around an inlet with a wooden
frame and gravel, installed as follows:
Construct a frame and attach wire mesh (½ inch openings) and filter fabric to the frame.
Pile coarse washed aggregate against the wire/fabric.
Place weight on frame anchors.
d) Curb and gutter sediment barriers (Figure D.2.1.5.H) consist of sandbags or rock berms (riprap
and aggregate) 3 feet high and 3 feet wide in a horseshoe shape, installed as follows:
Bags of either burlap or woven geotextile fabric, filled with a variety of media such as gravel,
wood chips, compost or sand stacked tightly allows water to pond and allows sediment to
separate from runoff.
Leave a “one bag gap” in the top row of the barrier to provide a spillway for overflow.
Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 x 3 and at
least 2 feet from the inlet.
Construct a horseshoe shaped sedimentation trap on the outside of the berm to sediment trap
standards for protecting a culvert inlet.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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4. Excavated drop inlet sediment traps are appropriate where relatively heavy flows are expected and
overflow capability is needed. If emergency overflow is provided, additional end-of-pipe treatment
may be required. Excavated drop inlets consist of an excavated impoundment area around a storm
drain. Sediment settles out of the stormwater prior to enter the drain. Install according to the following
specifications:
a) The impoundment area should have a depth of 1 to 2 feet measured from the crest of the inlet
structure.
b) Side slopes of the excavated area must be no steeper than 2:1.
c) Minimum volume of the excavated area should be 35 cubic yards.
d) Install provisions for draining the area to prevent standing water problems.
e) Keep the area clear of debris.
f) Weep holes may be drilled into the side of the inlet.
g) Protect weep holes with wire mesh and washed aggregate.
h) Weep holes must be sealed when removing and stabilizing excavated area.
i) A temporary dike may be necessary on the down slope side of the structure to prevent bypass
flow.
Maintenance Standards
1. Any accumulated sediment on or around inlet protection shall be removed immediately. Sediment
shall not be removed with water, and all sediment must be disposed of as fill on site or hauled off site.
2. Any sediment in the catch basin insert shall be removed when the sediment has filled one-third of the
available storage. The filter media for the insert shall be cleaned or replaced at least monthly.
3. Regular maintenance is critical for all forms of catch basin/inlet protection. Unlike many forms of
protection that fail gradually, catch basin protection will fail suddenly and completely if not
maintained properly.
D.2.1 ESC MEASURES
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FIGURE D.2.1.5.E FILTER FABRIC PROTECTION (NOT ALLOWED)
FIGURE D.2.1.5.F CATCH BASIN INSERT
CATCH BASIN
NOTE: ONLY TO BE USED WHERE
PONDING OF WATER ABOVE THE
CATCH BASIN WILL NOT CAUSE
TRAFFIC PROBLEMS AND WHERE
OVERFLOW WILL NOT RESULT IN
EROSION OF SLOPES.
GRATE
STANDARD STRENGTH
FILTER FABRIC
NOTE: THIS DETAIL IS ONLY
SCHEMATIC. ANY INSERT IS
ALLOWED THAT HAS:
A MIN. 0.5 C.F. OF STORAGE,
THE MEANS TO DEWATER THE
STORED SEDIMENT,
AN OVERFLOW, AND
CAN BE EASILY MAINTAINED.
OVERFLOW
GRATECATCHBASIN
POROUS
BOTTOM
SOLID
WALLS
FILTER
MEDIA FOR
DEWATERING
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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FIGURE D.2.1.5.G BLOCK AND GRAVEL CURB INLET PROTECTION
1. USE BLOCK AND GRAVEL TYPE SEDIMENT BARRIER WHEN CURB INLET IS LOCATED
IN GENTLY SLOPING SEGMENT, WHERE WATER CAN POND AND ALLOW SEDIMENT TO
SEPARATE FROM RUNOFF.
2. BARRIER SHALL ALLOW FOR OVERFLOW FROM SEVERE STORM EVENT.
3. INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENT
AND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY.
2x4 WOOD STUD
OVERFLOW
WATER
A
A
PLAN VIEW
NTS
SECTION A-A
NTS
BLOCK AND GRAVEL CURB INLET PROTECTION
NTS
CATCH BASIN COVER
CURB INLET
CONCRETE BLOCKS
CATCH BASIN COVER
CURB INLET
CATCH BASIN
BACK OF SIDEWALK
CURB FACE
3/4" DRAIN
GRAVEL (20 mm)
WIRE SCREEN OR
FILTER FABRIC
POND HEIGHT
WIRE SCREEN
OR FILTER FABRIC
2x4 WOOD STUD
100x50 TIMBER STUD)
3/4" DRAIN
GRAVEL (20 mm)
NOTES:
D.2.1 ESC MEASURES
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FIGURE D.2.1.5.H CURB AND GUTTER BARRIER PROTECTION
RUNOFF
RUNOFF
SPILLWAY
1. PLACE CURB-TYPE SEDIMENT BARRIERS ON GENTLY SLOPING STREET SEGMENTS,
WHERE WATER CAN POND AND ALLOW SEDIMENT TO SEPARATE FROM RUNOFF.
2. SANDBAGS OF EITHER BURLAP OR WOVEN GEOTEXTILE FABRIC ARE FILLED WITH
GRAVEL, LAYERED AND PACKED TIGHTLY.
3. LEAVE A ONE-SANDBAG GAP IN THE TOP ROW TO PROVIDE A SPILLWAY FOR OVERFLOW.
4. INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENT
AND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY.
GRAVEL FILLED SANDBAGS
STACKED TIGHTLY
DRAIN GRATE
GUTTER
CURB FACE
CURB INLET
SANDBAGS TO OVERLAP
ONTO CURB
BACK OF SIDEWALK
PLAN VIEW
NTS
CURB AND GUTTER BARRIER
NTS
NOTES:
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D.2.1.6 SURFACE WATER COLLECTION
All surface water from disturbed areas shall be intercepted, conveyed to a sediment pond or trap, and
discharged downslope of any disturbed areas. An exception is for areas at the perimeter of the site with
drainage areas small enough to be treated solely with perimeter protection (see Section D.2.1.3). Also, if
the soils and topography are such that no offsite discharge of surface water is anticipated up to and
including the developed 2-year runoff event, surface water controls are not required. A 10-year approved
model 15-minute peak flow shall be used for sizing surface water controls if the project size, expected
timing and duration of construction, or downstream conditions warrant a higher level of protection (see the
introduction to Section D.2.1.5). At the City’s discretion, sites may be worked during the dry season
without surface water controls, if there is some other form of protection of surface waters, such as a
100-foot forested buffer between the disturbed areas and adjacent surface waters. Significant sources of
upslope surface water that drain onto disturbed areas shall be intercepted and conveyed to a stabilized
discharge point downslope of the disturbed areas. Surface water controls shall be installed concurrently
with rough grading.
Purpose: The purpose of surface water control is to collect and convey surface water so that erosion is
minimized, and runoff from disturbed areas is treated by a sediment pond or trap. Surface water control
essentially consists of three elements:
1. Interception of runoff on and above slopes
2. Conveyance of the runoff to a sediment pond or trap (if the runoff was collected from a disturbed
area)
3. Release of the runoff downslope of any disturbed areas.
When to Install: Surface water controls shall be constructed during the initial grading of an area and must
be in place before there is any opportunity for storm runoff to cause erosion.
Measures to Install: Interceptor dikes/swales intercept runoff, ditches and pipe slope drains convey the
runoff, and riprap or level spreaders help release the runoff in a non-erosive manner. Each measure is to be
used under different circumstances so there is very little overlap. However, the two options for releasing
water in a non-erosive manner, outlet protection and level spreaders, can be somewhat interchangeable.
See Figure D.2.1.6.A for a schematic drawing demonstrating the use of these measures.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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FIGURE D.2.1.6.F LEVEL SPREADER
D.2.1.7 DEWATERING CONTROL
Any runoff generated by dewatering shall be treated through construction of a sediment trap
Section D.2.1.5.1) when there is sufficient space or by releasing the water to a well vegetated, gently
sloping area. Since pumps are used for dewatering, it may be possible to pump the sediment-laden water
well away from the surface water so that vegetation can be more effectively utilized for treatment.
Discharge of sediment-laden water from dewatering activities to surface and storm waters is prohibited. If
dewatering occurs from areas where the water has come in contact with new concrete, such as tanks,
vaults, or foundations, the pH of the water must be monitored and must be neutralized prior to discharge.
Clean non-turbid dewatering water, such as well point ground water can be discharged to systems tributary
to, or directly to surface waters provided the flows are controlled so no erosion or flooding occurs. Clean
water must not be routed through a stormwater sediment pond. Highly turbid or contaminated dewatering
water must be handled separately from stormwater.
Purpose: To prevent the untreated discharge of sediment-laden water from dewatering of utilities,
excavated areas, foundations, etc.
When to Install: Dewatering control measures shall be used whenever there is a potential for runoff from
dewatering of utilities, excavations, foundations, etc.
Measures to install:
1. Foundation, vault, excavation, and trench dewatering water that has similar characteristics to
stormwater runoff at the site shall be discharged into a controlled conveyance system prior to
discharge to a sediment trap or sediment pond. Foundation and trench dewatering water that has
similar characteristics to stormwater runoff at the site must be disposed of through one of the
following options depending on site constraints:
a) Infiltration,
b) Transport offsite in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that
does not pollute surface waters,
SPREADER MUST BE LEVEL
18" MIN. REBAR SUPPORTS
8' MIN. SPACING
CROSS SECTION
DETAIL OF SPREADER
DENSELY VEGETATED FOR
A MIN. OF 100' AND SLOPE
LESS THAN 5:1
PRESSURE-TREATED
2"X10"
3' MIN.
TREATED 2"x10" MAY BE ABUTTED END TO
END FOR MAX. SPREADER LENGTH OF 50'
6" MIN.
6" MIN.
1" MIN.
2H:1VMAX.
1' MIN.
D.2.1 ESC MEASURES
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c) Discharge to the sanitary sewer discharge with approval from King County and the City of Renton
if there is no other option, or
d) Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized
dewatering.
2. Clean, non-turbid dewatering water, such as well-point ground water, may be discharged via stable
conveyance to systems tributary to surface waters, provided the dewatering flow does not cause
erosion or flooding of receiving waters.
3. Highly turbid or contaminated dewatering water (high pH or other) shall be handled separately
from stormwater. See Section D.2.2 , SWPPS Measures.
D.2.1.8 DUST CONTROL
Preventative measures to minimize the wind transport of soil shall be taken when a traffic hazard may be
created or when sediment transported by wind is likely to be deposited in water resources or adjacent
properties.
Purpose: To prevent wind transport of dust from exposed soil surfaces onto roadways, drainage ways, and
surface waters.
When to Install: Dust control shall be implemented when exposed soils are dry to the point that wind
transport is possible and roadways, drainage ways, or surface waters are likely to be impacted. Dust
control measures may consist of chemical, structural, or mechanical methods.
Measures to Install: Water is the most common dust control (or palliative) used in the area. When using
water for dust control, the exposed soils shall be sprayed until wet, but runoff shall not be generated by
spraying. Calcium chloride, Magnesium chloride, Lignin derivatives, Tree Resin Emulsions, and Synthetic
Polymer Emulsions may also be used for dust control. Exposed areas shall be re-sprayed as needed. Oil
shall not be used for dust control. The following table lists many common dust control measures. Some of
the measures are not recommended for use in the City and must have prior approval prior to use from the
CED inspector assigned to specific projects.
TABLE D.2.1.8.A DUST CONTROL MEASURES
Method Considerations Site Preparation
Recommended
Application Rate
Water -Most commonly used practice
Evaporates quickly
Lasts less than 1 day
For all liquid agents:
Blade a small surface
Crown or slope surface to avoid
ponding
Compact soils if needed
Uniformly pre-wet at
0.03 – 0.3 gal/sq yd
Apply solution under pressure.
Overlap solution 6 – 12 inches
Allow treated area to cure
0 – 4 hours
Compact area after curing
Apply second treatment before first
treatment becomes ineffective
0.125 gal/sq yd every
20 to 30 minutes
Salts
Calcium
Chloride
CaCl)
Restricts evaporation
Lasts 6–12 months
Can be corrosive
Less effective in low humidity
Can build up in soils and leach by rain
Apply 38% solution at
1.21L/m2 (0.27 gal/yd2)
or as loose dry granules
per manufacturer
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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TABLE D.2.1.8.A DUST CONTROL MEASURES
Method Considerations Site Preparation
Recommended
Application Rate
Magnesium
Chloride
MgCl)
Restricts evaporation
Works at higher temperatures and lower
humidity than CaCl
May be more costly than CaCl
Apply 26 – 32%
solution at 2.3 L/m2
0.5 gal/yd2)
Sodium
Chloride
NaCl)
Effective over smaller range of
conditions
Less expensive
Can be corrosive
Less effective in low humidity
Per Manufacturer
Silicates -Generally expensive
Available in small quantities
Require Second application
Surfactants -High evaporation rates
Effective for short time periods
Must apply frequently
Copolymers -Forms semi-permeable transparent
crust
Resists ultraviolet radiation and
moisture induced breakdown
Last 1 to 2 years
750 – 940 L/ha (80 –
100 gal/ac)
Petroleum
Products
Used oil is prohibited as a dust control
method
Bind soil particles
May hinder foliage growth
Environmental and aesthetic concerns
Higher cost
Use 57 – 63% resins as
base. Apply at 750 –
940 L/ha
80–100 gal/ac)
Lignin
Sulfonate
Paper industry waste product
Acts as dispersing agent
Best in dry climates
Can be slippery
Will decrease Dissolved Oxygen in
waterways therefore cannot be used
adjacent to surface water systems
Loosen surface
25–50 mm (1–2 inches)
Need 4–8% fines
Vegetable
Oils
Coat grains of soils, so limited binding
ability
May become brittle
Limited availability
Per Manufacturer
Spray on
Adhesives
Available as organic or synthetic
Effective on dry, hard soils
Forms a crust
Can last 3 to 4 years
Per Manufacturer
D.2.1.9 FLOW CONTROL
Surface water from disturbed areas must be routed through the project’s onsite flow control facility or
other provisions must made to prevent increases in the existing site conditions 2-year and 10-year runoff
peaks discharging from the project site during construction.
Purpose: The purpose of surface water flow control is to mitigate increases in runoff peaks that occur
during construction as a result of clearing vegetation, compacting the soil, and adding impervious surface.
Such increases can cause or aggravate downstream flooding and erosion.
D.2.1 ESC MEASURES
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When to Install: Surface water flow control shall be installed or otherwise provided prior to any clearing
and/or grading of the site, except that required to construct the surface water flow control facilities.
Measures to Use: The project’s onsite flow control facility or other equivalent storage facility that meets
the peak-matching performance criteria stated above.
D.2.1.10 PROTECT EXISTING AND PROPOSED STORMWATER FACILITIES AND
ON-SITE BMPS
Protection measures shall be applied/installed and maintained so as to prevent adverse impacts to existing
stormwater facilities and on-site BMPs and areas of proposed stormwater facilities and on-site BMPs for
the project. Adverse impacts can prompt the requirement to restore or replace affected stormwater
facilities and on-site BMPs.
Purpose: The purpose of protecting existing and proposed stormwater facility and on-site BMP areas is to
avoid sedimentation and soil compaction that would adversely affect infiltration, and also avoid
contamination by other pollutants.
When to Install: Stormwater facility and on-site BMP area protection shall be installed or otherwise
provided prior to any clearing and/or grading of the site, except that required to construct stormwater
facilities and on-site BMPs.
Measures to Use:
1. Protect all stormwater facilities and on-site BMPs and proposed stormwater facility and on-site BMP
footprints from sedimentation through installation and maintenance of erosion and sediment control
BMPs on portions of the site that drain into the BMPs/facilities.
2. Stormwater facilities and on-site BMPs shall be restored to their fully functioning condition if they
accumulate sediment during construction. Restoring the stormwater facilities and on-site BMPs shall
include, at a minimum, removal of sediment and any sediment-laden bioretention soils, and replacing
the removed soils with soils meeting the design specification. Replacement with a new fully-
functioning stormwater facility and/or on-site BMP may be required if restoration to the fully-
functioning condition can’t be accomplished.
3. Prevent compacting Bioretention BMPs/facilities by excluding construction equipment and foot
traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment.
4. Control erosion and avoid introducing sediment from surrounding land uses onto permeable pavement
BMPs. Do not allow muddy construction equipment on the base material or pavement. Do not allow
sediment-laden runoff onto permeable pavements.
5. Permeable pavement BMPs fouled with sediments or no longer passing an initial infiltration text must
be cleaned using procedures from Appendix A or the manufacturer’s procedures.
6. Keep all heavy equipment off existing soils under stormwater facilities and on-site BMPs that have
been excavated to final grade to retain the infiltration rate of the soils.
D.2.1.11 MAINTAIN PROTECTIVE BMPS
Protection measures shall be maintained to ensure continued performance of their intended function, to
prevent adverse impacts to existing stormwater facilities and on-site BMPs and areas of proposed
BMPs/facilities, and protect other disturbed areas of the project.
Purpose: The purpose of maintaining protective BMPs is to provide continuous erosion and sediment
control protection throughout the life of the project, and avoid sedimentation, soil compaction and
contamination by other pollutants that would adversely affect infiltration and surface runoff.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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When to Maintain: Protection measures shall be monitored per Section D.2.4.4 at a minimum, and
promptly maintained to fully functioning condition as necessary to ensure continued performance of their
intended function.
Measures to Use:
1. Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to
ensure continued performance of their intended function in accordance with BMP specifications.
2. Remove all temporary erosion and sediment control BMPs prior to final construction approval, or
within 30 days after achieving final site stabilization or after the temporary BMPs are no longer
needed.
3. Provide protection to all stormwater facilities and on-site BMPs installed for the permanent control of
stormwater from sediment and compaction. All stormwater facilities and on-site BMPs that are to
remain in place following completion of construction shall be examined and placed in full operating
conditions. If sediment enters the stormwater facilities and/or on-site BMPs during construction, it
shall be removed and the stormwater facility and on-site BMP shall be returned to the conditions
specified in the construction documents or as required for full stormwater facility and on-site BMP
replacement.
4. Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting from
removal of erosion and sediment control BMPs or vegetation.
D.2.1.12 MANAGE THE PROJECT
Coordination and timing of site development activities relative to ESC concerns (Section D.2.4), and
timely inspection, maintenance and update of protective measures (Section D.2.3) are necessary to
effectively manage the project and ensure the success of protective ESC and SWPPS design and
implementation.
Projects shall assign a qualified CSWPP Supervisor (Section D.2.3.1) to be the primary contact for ESC
and SWPPP issues and reporting, coordination with subcontractors and implementation of the CSWPP
plan as a whole.
Measures to Use:
1. Phase development projects to the maximum degree practicable and take into account seasonal work
limits.
2. Inspection and monitoring – Inspect, maintain, and repair all BMPs as needed to ensure continued
performance of their intended function. Conduct site inspections and monitoring in accordance with
the Construction Stormwater General Permit and City requirements.
3. Maintaining an updated construction SWPPP – Maintain, update, and implement the SWPPP in
accordance with the Construction Stormwater General Permit and City requirements.
4. Projects that disturb one or more acres must have, site inspections conducted by a Certified Erosion
and Sediment Control Lead (CESCL) (see Section D.2.3.1). Project sites less than one acre (not part
of a larger common plan of development or sale) may have a person without CESCL certification
conduct inspections. By the initiation of construction, the SWPPP must identify the CESCL or
inspector, who shall be present onsite or on-call at all times.
The CESCL or inspector (project sites less than one acre) must have the skills to assess the:
Site conditions and construction activities that could impact the quality of stormwater.
Effectiveness of erosion and sediment control measures used to control the quality of stormwater
discharges.
The CESCL or inspector must examine stormwater visually for the presence of suspended
sediment, turbidity, discoloration, and oil sheen. They must evaluate the effectiveness of BMPs
and determine if it is necessary to install, maintain, or repair BMPs to improve the quality of
stormwater discharges.
D.2.2 SWPPS MEASURES
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Based on the results of the inspection, construction site operators must correct the problems identified
by:
Reviewing the SWPPP for compliance with all construction SWPPP elements and making
appropriate revisions within 7 days of the inspection.
Immediately beginning the process of fully implementing and maintaining appropriate source
control and/or treatment BMPs as soon as possible, addressing the problems not later than within
10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10
days, the construction site operator may request an extension within the initial 10-day response
period.
Documenting BMP implementation and maintenance in the site log book (applies only to sites
that have coverage under the Construction Stormwater General Permit).
The CESCL or inspector must inspect all areas disturbed by construction activities, all BMPs, and
all stormwater discharge points at least once every calendar week and within 24 hours of any
discharge from the site. (For purposes of this condition, individual discharge events that last more
than one day do not require daily inspections. For example, if a stormwater pond discharges
continuously over the course of a week, only one inspection is required that week.) The CESCL
or inspector may reduce the inspection frequency for temporary stabilized, inactive sites to once
every calendar month.
D.2.2 SWPPS MEASURES
This section details the SWPPS measures that are required to prevent, reduce, or eliminate the discharge of
pollutants to onsite or adjacent stormwater systems or watercourses from construction-related activities
such as materials delivery and storage, onsite equipment fueling and maintenance, demolition of existing
buildings and disposition of demolition materials and other waste, and concrete handling, washout and
disposal. These SWPPS measures represent Best Management Practices (BMPs)8 for the control of
pollutant drips and spills as well as other impacts related to construction such as increased pH in concrete
construction and handling activities. Compliance with each of the SWPPS measures, and with any project-
specific control measures, to the extent applicable and necessary to meet the performance criteria in
Section D.2.2, and compliance with the CSWPP implementation requirements in Section D.2.4, constitutes
overall compliance with the City’s CSWPP Standards.
Note: Additional measures shall be required by the City if the existing standards are insufficient to protect
adjacent properties, drainage facilities, or water resources.
The standards for each individual SWPPS measure are divided into four sections:
1. Purpose
2. Conditions of Use
3. Design and Installation Specifications
4. Maintenance Requirements.
Note that the “Conditions of Use” always refers to site conditions. As site conditions change, SWPPS
measures must be changed to remain in compliance with the requirements of this appendix.
Whenever compliance with City SWPPS Standards is required, all of the following SWPPS measures must
be considered for application to the project site as detailed in the following sections. The construction
pollutant generating concerns addressed by the BMPs that follow include:
Concrete handling, washout and disposal(specifically portland cement concrete)
Sawcutting and surfacing activities
Materials delivery, storage and containment
8 Best Management Practices (BMPs) means the best available and reasonable physical, structural, managerial, or behavioral
activities, that when singly or in combination, eliminate or reduce the contamination of surface and/or ground waters.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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Filtration and chemical treatment of construction water to facilitate disposal or discharge to approved
locations
Reporting requirements and documentation availability for specific BMP processes
Additionally, several of the ESC BMPs described in Section D.2.1 can be applicable to the SWPPS plan,
e.g., use of cover, fencing and access protection to protect temporary materials storage locations. The
applicant’s material supplier may be a resource (subject to City approval) for BMPs to address specific
project applications or proposals. Conditions of approval on adjustments may also specify additional
requirements for the SWPPS plan.
D.2.2.1 CONCRETE HANDLING
Purpose
Concrete work can generate process water and slurry that contain fine particles and high pH, both of which
can violate water quality standards in the receiving water. Concrete spillage or concrete discharge to
surface waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, concrete
process water, and concrete slurry from entering waters of the state.
Conditions of Use
Any time concrete is used, utilize these management practices. Concrete construction projects include, but
are not limited to, curbs, sidewalks, roads, bridges, foundations, floors, stormwater vaults, retaining walls,
driveways and runways.
Design and Installation Specifications
1. Ensure that washout of concrete trucks, chutes, pumps, and internals is performed at an approved off-
site location or in designated concrete washout areas. Do not wash out concrete trucks, chutes, pumps,
or internals onto the ground, or into storm drains, open ditches, streets, or streams. Refer to BMP
D.2.2.2 for information on concrete washout areas.
2. Return unused concrete remaining in the truck and pump to the originating batch plant for recycling.
Do not dump excess concrete on site, except in designated concrete washout areas.
3. Wash off hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels into
formed areas awaiting future concrete pours only.
4. Do not wash out to formed areas awaiting infiltration BMPs.
5. Wash equipment difficult to move, such as concrete pavers in areas that do not directly drain to
natural or constructed stormwater conveyances.
6. Do not allow washdown from areas, such as concrete aggregate driveways, to drain directly to natural
or constructed stormwater conveyances.
7. Contain washwater and leftover product in a lined container when no formed areas are available.
Dispose of contained concrete in a manner that does not violate ground water or surface water quality
standards.
8. Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface
waters.
9. Refer to BMPs D.2.2.7 and D.2.2.8 for pH adjustment requirements.
10. Refer to the Construction Stormwater General Permit for pH monitoring requirements if the project
involves one of the following activities:
Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete
used over the life of a project).
The use of engineered soils amended with (but not limited to) Portland cement-treated base,
cement kiln dust or fly ash.
Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH.
D.2.2 SWPPS MEASURES
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D-73
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repair the same day.
D.2.2.2 CONCRETE WASHOUT AREA
Purpose
Prevent or reduce the discharge of pollutants to stormwater from concrete waste by conducting washout
off-site, or performing onsite washout in a designated area to prevent pollutants from entering surface
waters or ground water.
Conditions of Use
Concrete washout area best management practices are implemented on construction projects where:
Concrete is used as a construction material
It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.).
Concrete trucks, pumpers, or other concrete coated equipment are washed onsite.
Note: If less than 10 concrete trucks or pumpers need to be washed out onsite, the washwater may be
disposed of in a formed area awaiting concrete or an upland disposal site where it will not contaminate
surface or ground water. The upland disposal site shall be at least 50 feet from sensitive areas such as
storm drains, open ditches, or water bodies, including wetlands.
Design and Installation Specifications
Implementation
The following steps will help reduce stormwater pollution from concrete wastes:
1. Perform washout of concrete trucks at an approved off-site location or in designated concrete washout
areas only.
2. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or
streams.
3. Do not allow excess concrete to be dumped onsite, except in designated concrete washout areas.
4. Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures
above-grade or below-grade).
5. Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies
may offer delivery service and provide regular maintenance and disposal of solid and liquid waste.
6. If self-installed concrete washout areas are used, below-grade structures are preferred over above-
grade structures because they are less prone to spills and leaks.
7. Self-installed above-grade structures should only be used if excavation is not practical.
Education
1. Discuss the concrete management techniques described in this BMP with the ready-mix concrete
supplier before any deliveries are made.
2. Educate employees and subcontractors on the concrete waste management techniques described in this
BMP.
3. Arrange for contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to
oversee and enforce concrete waste management procedures.
4. A sign should be installed adjacent to each temporary concrete washout facility to inform concrete
equipment operators to utilize the proper facilities.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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Contracts
Incorporate requirements for concrete waste management into concrete supplier and subcontractor
agreements.
Location and Placement
1. Locate washout area at least 50 feet from sensitive areas such as storm drains, open ditches, or water
bodies, including wetlands.
2. Allow convenient access for concrete trucks, preferably near the area where the concrete is being
poured.
3. If trucks need to leave a paved area to access washout, prevent track-out with a pad of rock or quarry
spalls (see BMP D.2.1.4.2). These areas should be far enough away from other construction traffic to
reduce the likelihood of accidental damage and spills.
4. The number of facilities you install should depend on the expected demand for storage capacity.
5. On large sites with extensive concrete work, washouts should be placed in multiple locations for ease
of use by concrete truck drivers.
On-Site Temporary Concrete Washout Facility, Transit Truck Washout Procedures:
1. Temporary concrete washout facilities shall be located a minimum of 50 feet from sensitive areas
including storm drain inlets, open drainage facilities, and watercourses. (See Figures D.2.2.2.A,
D.2.2.2.B, and D.2.2.2.C).
2. Concrete washout facilities shall be constructed and maintained in sufficient quantity and size to
contain all liquid and concrete waste generated by washout operations.
3. Washout of concrete trucks shall be performed in designated areas only.
4. Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and
discharged into designated washout area or properly disposed of off-site.
5. Once concrete wastes are washed into the designated area and allowed to harden, the concrete should
be broken up, removed, and disposed of per applicable solid waste regulations. Dispose of hardened
concrete on a regular basis.
6. Temporary Above-Grade Concrete Washout Facility
a) Temporary concrete washout facility (type above grade) should be constructed as shown on the
details below, with a recommended minimum length and minimum width of 10 ft, but with
sufficient quantity and volume to contain all liquid and concrete waste generated by washout
operations.
b) Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of
holes, tears, or other defects that compromise the impermeability of the material.
7. Temporary Below-Grade Concrete Washout Facility
a) Temporary concrete washout facilities (type below grade) should be constructed as shown on the
details below, with a recommended minimum length and minimum width of 10 ft. The quantity
and volume should be sufficient to contain all liquid and concrete waste generated by washout
operations.
b) Lath and flagging should be commercial type.
c) Plastic lining material shall be a minimum of 10 mil polyethylene sheeting and should be free of
holes, tears, or other defects that compromise the impermeability of the material.
d) Liner seams shall be installed in accordance with manufacturers’ recommendations.
D.2.2 SWPPS MEASURES
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e) Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic
lining material.
Maintenance Standards
Inspection and Maintenance
1. Inspect and verify that concrete washout BMPs are in place prior to the commencement of concrete
work.
2. During periods of concrete work, inspect daily to verify continued performance.
a) Check overall condition and performance.
b) Check remaining capacity (% full).
c) If using self-installed washout facilities, verify plastic liners are intact and sidewalls are not
damaged.
d) If using prefabricated containers, check for leaks.
3. Washout facilities shall be maintained to provide adequate holding capacity with a minimum
freeboard of 12 inches.
4. Washout facilities must be cleaned, or new facilities must be constructed and ready for use once the
washout is 75% full.
5. If the washout is nearing capacity, vacuum and dispose of the waste material in an approved manner.
a) Do not discharge liquid or slurry to waterways, storm drains or directly onto ground.
b) Do not use sanitary sewer without local approval.
c) Place a secure, non-collapsing, non-water collecting cover over the concrete washout facility prior
to predicted wet weather to prevent accumulation and overflow of precipitation.
d) Remove and dispose of hardened concrete and return the structure to a functional condition.
Concrete may be reused onsite or hauled away for disposal or recycling.
6. When you remove materials from the self-installed concrete washout, build a new structure; or, if the
previous structure is still intact, inspect for signs of weakening or damage, and make any necessary
repairs. Re-line the structure with new plastic after each cleaning.
Removal of Temporary Concrete Washout Facilities
1. When temporary concrete washout facilities are no longer required for the work, the hardened
concrete, slurries and liquids shall be removed and properly disposed of.
2. Materials used to construct temporary concrete washout facilities shall be removed from the site of the
work and disposed of or recycled.
3. Holes, depressions or other ground disturbance caused by the removal of the temporary concrete
washout facilities shall be backfilled, repaired, and stabilized to prevent erosion.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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FIGURE D.2.2.2.A CONCRETE WASHOUT AREA (ABOVE GRADE)
SECTION B-B
NTS
SECTION A-A
NTS
STAPLE DETAIL
NTS
PLAN
NTS
ABOVE GRADE TEMPORARY CONCRETE WASHOUT FACILITY
NTS
CONCRETE WASHOUT SIGN DETAIL
NTS 10 mil PLASTIC
LINING
PLAN
NTS
TYPE "ABOVE GRADE" WITH
WOOD PLANKS
TYPE "ABOVE GRADE" WITH STRAW BALES
10 mil PLASTIC
LINING
16 GAUGE
STEEL WIRE
2"
8"
LAG SCREWS ( 12" )
BLACK LETTERS
6" HEIGHT
PLYWOOD 4' X 2'
PAINTED WHITE
WOOD POST
312" x 312" x 8'
3'
3'
STRAW
BALES
TYP.)
STAKE
TYP.)
WEDGE LOOSE
STRAW
BETWEEN BALES
SAND OR GRAVEL-FILLED
BAGS IN CORNERS
10' MIN. RECOMMENDED
VARIES
WOOD OR
METAL STAKES
2 PER BALE)
STRAW BALES (2
BALES HIGH, MAX.)
ORIGINAL GROUND
10 mil PLASTIC
LINING
STAPLES (2 PER BALE)
SAND OR GRAVEL-FILLED
BAGS IN CORNERS
NATIVE MATERIAL
OPTIONAL)
10 mil
PLASTIC
LINING
WOOD FRAME SECURELY
FASTENED AROUND
ENTIRE PERIMETER WITH
TWO STAKES
TWO-STACKED
2x12 ROUGH
WOOD FRAME
STAKE
TYP.)
10' MIN. RECOMMENDED
VARIES
NOTES:
1. ACTUAL LAYOUT DETERMINED IN
THE FIELD
2. THE CONCRETE WASHOUT SIGN
SHALL BE INSTALLED WITHIN 30'
OF THE FACILITY
1' MIN.
Adapted from CalTrans Fig4-14 SAC 8-14-02
D.2.2 SWPPS MEASURES
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D-77
FIGURE D.2.2.2.B CONCRETE WASHOUT AREA (BELOW GRADE)
FIGURE D.2.2.2.C PREFABRICATED CONCRETE WASHOUT CONTAINER W/RAMP
EARTHEN BERM
TYPICAL SECTION
NTS
BELOW GRADE TEMPORARY CONCRETE WASHOUT FACILITY
NTS
CONCRETE WASHOUT SIGN DETAIL
NTS
SANDBAG
PLAN
NTS
Adapted from CalTrans Fig4-14 SAC 8-14-02
10 mil
PLASTIC
LINING
LAG SCREWS ( 12" )
BLACK
LETTERS
6" HEIGHT
PLYWOOD 4' X 2'
PAINTED WHITE
WOOD POST
312" x 312" x 8'
3'
3'
EARTHEN
BERM
10 mil
PLASTIC
LINING
SANDBAG
10' MIN. RECOMMENDED
VARIES
BERM
3'
LATH AND
FLAGGING
ON 3 SIDES
NOTES:
1. ACTUAL LAYOUT DETERMINED IN
THE FIELD
2. THE CONCRETE WASHOUT SIGN
SHALL BE INSTALLED WITHIN 30' OF
THE FACILITY
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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D.2.2.3 SAWCUTTING AND SURFACING POLLUTION PREVENTION
Purpose
Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high
pH (concrete cutting), both of which can violate the water quality standards in the receiving water.
Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to
minimize and eliminate process water and slurry created through sawcutting or surfacing from entering
waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and
surfacing operations include, but are not limited to, sawing, coring, grinding, roughening, hydro-
demolition, bridge and road surfacing
Design and Installation Specifications
1. Vacuum slurry and cuttings during cutting and surfacing operations.
2. Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.
3. Slurry and cuttings shall not drain to any natural or constructed drainage conveyance including
stormwater systems. This may require temporarily blocking catch basins.
4. Dispose of collected slurry and cuttings in a manner that does not violate ground water or surface
water quality standards.
5. Do not allow process water generated during hydro-demolition, surface roughening or similar
operations to drain to any natural or constructed drainage conveyance including stormwater systems.
Dispose process water in a manner that does not violate ground water or surface water quality
standards.
6. Handle and dispose cleaning waste material and demolition debris in a manner that does not cause
contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate
disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters
of the state. If inspections show that a violation of water quality standards could occur, stop operations and
immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum
trucks.
D.2.2.4 MATERIAL DELIVERY, STORAGE, AND CONTAINMENT
Purpose
Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from
material delivery and storage. Minimize the storage of hazardous materials onsite, store materials in a
designated area, and install secondary containment.
Conditions of Use
These procedures are suitable for use at all construction sites with delivery and storage of the following
materials:
Petroleum products such as fuel, oil and grease
Soil stabilizers and binders (e.g., Polyacrylamide)
Fertilizers, pesticides and herbicides
Detergents
Asphalt and concrete compounds
D.2.2 SWPPS MEASURES
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Hazardous chemicals such as acids, lime, adhesives, paints, solvents and curing compounds
Any other material that may be detrimental if released to the environment
Design and Installation Specifications
The following steps should be taken to minimize risk:
1. Temporary storage area should be located away from vehicular traffic, near the construction
entrance(s), and away from waterways or storm drains.
2. Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be
kept in their original labeled containers.
3. Hazardous material storage onsite should be minimized.
4. Hazardous materials should be handled as infrequently as possible.
5. During the wet weather season (October 1 – April 30), consider storing materials in a covered area.
6. Materials should be stored in secondary containments, such as earthen dike, horse trough, or even a
children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small
amounts of material may be secondarily contained in “bus boy” trays or concrete mixing trays.
7. Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a
pallet and, when possible, and within secondary containment.
8. If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the
lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums,
preventing water from collecting.
Material Storage Areas and Secondary Containment Practices:
1. Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in
approved containers and drums and shall not be overfilled. Containers and drums shall be stored in
temporary secondary containment facilities.
2. Temporary secondary containment facilities shall provide for a spill containment volume able to
contain 10% of the total enclosed container volume of all containers, or 110% of the capacity of the
largest container within its boundary, whichever is greater.
3. Secondary containment facilities shall be impervious to the materials stored therein for a minimum
contact time of 72 hours.
4. Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the
event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums.
These liquids shall be handled as hazardous waste unless testing determines them to be non-
hazardous.
5. Sufficient separation should be provided between stored containers to allow for spill cleanup and
emergency response access.
6. During the wet weather season (October 1 – April 30), each secondary containment facility shall be
covered during non-working days, prior to and during rain events.
7. Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill
clean-up material (spill kit).
8. The spill kit should include, at a minimum:
1-Water Resistant Nylon Bag
3-Oil Absorbent Socks 3 x 4
2-Oil Absorbent Socks 3 x 10
12-Oil Absorbent Pads 17 x 19
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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1-Pair Splash Resistant Goggles
3-Pair Nitrile Gloves
10-Disposable Bags with Ties
Instructions
D.2.2.5 CONSTRUCTION STORMWATER CHEMICAL TREATMENT
Purpose
This BMP applies when using stormwater chemicals in batch treatment or flow-through treatment.
Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a construction
site. Sedimentation ponds are effective at removing larger particulate matter by gravity settling, but are
ineffective at removing smaller particulates such as clay and fine silt. Traditional erosion and sediment
control BMPs may not be adequate to ensure compliance with the water quality standards for turbidity in
receiving water.
Chemical treatment can reliably provide exceptional reductions of turbidity and associated pollutants.
Chemical treatment may be required to meet turbidity stormwater discharge requirements, especially when
construction is to proceed through the wet season.
Conditions of Use
Formal written approval from Ecology is required for the use of chemical treatment regardless of
site size. The City also requires review and approval. When approved, the chemical treatment systems
must be included in the SWPPS portion of the project’s CSWPP.
Design and Installation Specifications
Coagulation and flocculation have been used for over a century to treat water. It is used less frequently for
the treatment of wastewater. The use of coagulation and flocculation for treating stormwater is a very
recent application. Experience with the treatment of water and wastewater has resulted in a basic
understanding of the process, in particular factors that affect performance. This experience can provide
insights as to how to most effectively design and operate similar systems in the treatment of stormwater.
Fine particles suspended in water give it a milky appearance, measured as turbidity. Their small size, often
much less than 1 m in diameter, give them a very large surface area relative to their volume. These fine
particles typically carry a negative surface charge. Largely because of these two factors, small size and
negative charge, these particles tend to stay in suspension for extended periods of time. Thus, removal is
not practical by gravity settling. These are called stable suspensions. Polymers, as well as inorganic
chemicals such as alum, speed the process of clarification. The added chemical destabilizes the suspension
and causes the smaller particles to agglomerate. The process consists of three steps: coagulation,
flocculation, and settling or clarification. Each step is explained below as well as the factors that affect the
efficiency of the process.
Coagulation: Coagulation is the first step. It is the process by which negative charges on the fine particles
that prevent their agglomeration are disrupted. Chemical addition is one method of destabilizing the
suspension, and polymers are one class of chemicals that are generally effective. Chemicals that are used
for this purpose are called coagulants. Coagulation is complete when the suspension is destabilized by the
neutralization of the negative charges. Coagulants perform best when they are thoroughly and evenly
dispersed under relatively intense mixing. This rapid mixing involves adding the coagulant in a manner
that promotes rapid dispersion, followed by a short time period for destabilization of the particle
suspension. The particles are still very small and are not readily separated by clarification until
flocculation occurs.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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proper disposal must be submitted to the City. All authorizations for disposal shall be obtained prior to
CKD/CTB application.
Infiltration: Depending on the site conditions, pH-adjusted stormwater may be infiltrated. Prior to
infiltration, pH must be between 6.5 and 8.5.
Surface Water: Contact water from the application area shall not be discharged to surface waters,
even if treatment has adjusted the pH.
8. Emergency backup plan: An emergency backup plan must be prepared and ready to implement to
handle large quantities of stormwater.
9. Monitoring shall be conducted to determine that contact stormwater is not leaving the site. Offsite
monitoring shall also be conducted to identify impacts to adjacent water bodies. Bonding may be
required to cover mitigation of impacts and restoration.
10. A soils specialist will establish the mixing percentage for onsite soils. Soil amendments will never
occur in excess of the ability of the onsite equipment and resources to meet all BMP requirements.
11. For sites one acre or larger, a Construction Stormwater General permit must be obtained from
Ecology. Construction Stormwater General permits and ‘Stormwater Pollution Prevention Plans
SWPPPs) must be amended and the use of CKD/CTB must be approved by Ecology prior to
application.
The contractor/developer shall comply will all federal, state, and local regulations. A health and safety
plan may be required for the protection of CED inspectors.
Additional BMPs may be applicable depending on mix design, proximity of wetlands or streams (e.g.,
within 300 feet of class/type I and 100 feet or less for other types) and site conditions.
D.2.2.10 MAINTAIN PROTECTIVE BMPS
Pollutant protection measures shall be maintained to ensure continued performance of their intended
function. Reporting and documentation shall be kept current and made available to CED as indicated.
Purpose: The purpose of maintaining protective BMPs is to provide effective pollutant protection when
and where required by the plan and the project, and to provide timely and relevant project information.
When to Maintain: Protection measures shall be monitored per Section D.2.4.4 at a minimum,
continuously during operation, and promptly maintained to fully functioning condition as necessary to
ensure continued performance of their intended function. Documentation shall be kept current per specific
BMP requirements.
Measures to Use:
1. Maintain and repair all pollutant control BMPs as needed to ensure continued performance of their
intended function in accordance with BMP specifications.
2. Maintain and repair storage locations for equipment and materials associated with BMP processes.
Conduct materials disposal in compliance with City requirements.
3. As required, provide current reporting and performance documentation at an accessible location for
the site inspector and other CED staff.
4. Remove all temporary pollutant control BMPs prior to final construction approval, or within 30 days
after achieving final site stabilization or after the temporary BMPs are no longer needed.
D.2.2.11 MANAGE THE PROJECT
SWPPP requirements shall be implemented and managed as part of the overall CSWPP plan. Concrete
construction and its impacts are primary among pollutant concerns on site development projects. Fueling
operations and materials containment of treatment chemicals and other project materials are also typical
D.2.2 SWPPS MEASURES
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D-101
pollutant concerns. Operations that produce these and other pollutants are often conducted by
subcontractors and their laborers, yet may require specific protective measures, documentation and
reporting. Protective measures and BMPs need to be made available prior to construction and suitable
oversight provided to ensure inspection, monitoring and documentation requirements are met.
Projects shall assign a qualified CSWPP Supervisor (Section D.2.3.1) to be the primary contact for
SWPPP and ESC issues and reporting, coordination with subcontractors and implementation of the
CSWPP plan as a whole.
Measures to Use:
1. Phase development projects to the maximum degree practicable and take into account seasonal work
limits.
2. Inspection and monitoring – Inspect, maintain, and repair all BMPs as needed to ensure continued
performance of their intended function. Conduct site inspections and monitoring in accordance with
the Construction Stormwater General Permit and City requirements. Coordinate with subcontractors
and laborers to ensure the SWPPP measures are followed.
3. Documentation and reporting – Inspect, maintain, and repair all BMPs as needed to ensure continued
performance of their intended function. Document site inspections and monitoring in accordance with
the Construction Stormwater General Permit, specific BMP conditions and City requirements. Log
sheets provided in Reference Section 8 may be used if appropriate. Follow reporting requirements and
provide documentation as requested to CED staff.
4. Maintaining an updated construction SWPPP – Maintain, update, and implement the SWPPP in
accordance with the Construction Stormwater General Permit and City requirements. Obtain approval
for specific SWPPP measures (e.g., chemical treatments of stormwater) well in advance of need.
Coordinate SWPPP plan updates with the site inspector (see Section D.2.4.1).
D.2.3 CSWPP PERFORMANCE AND COMPLIANCE PROVISIONS
The changing conditions typical of construction sites call for frequent field adjustments of existing ESC
and SWPPS measures or additional ESC and SWPPS measures in order to meet required performance. In
some cases, strict adherence to specified measures may not be necessary or practicable based on site
conditions or project type. In other cases, immediate action may be needed to avoid severe impacts.
Therefore, careful attention must be paid to ESC and SWPPS performance and compliance in accordance
with the provisions contained in this section.
D.2.3.1 CSWPP SUPERVISOR
For projects in Targeted, Full, or Large Project Drainage Review, or projects in Directed Drainage Review
as determined by CED review staff, the applicant must designate a CSWPP supervisor who shall be
responsible for the performance, maintenance, and review of ESC and SWPPS measures and for
compliance with all permit conditions relating to CSWPP as described in the CSWPP Standards. The
applicant’s selection of a CSWPP supervisor must be approved by the City. (City approval may be
rescinded for non-compliance, requiring the applicant to select another CSWPP supervisor and obtain City
approval prior to continuing work on the project site.)
For projects that disturb one acre or more of land, the CSWPP supervisor must be a Certified
Professional in Erosion and Sediment Control (see <www.cpesc.net> for more information) or a
Certified Erosion and Sediment Control Lead whose certification is recognized by the City.11 The City
may also require a certified ESC professional for sites smaller than one acre of disturbance if CED
determines that onsite ESC measures are inadequately installed, located, or maintained.
11 The City’s recognition of certification means that the individual has taken an approved third party training program and has
passed the approved test for that training program.
SECTION D.2 GENERAL CSWPP REQUIREMENTS
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For larger, more sensitive sites, the City may require a certified ESC professional with several years of
experience in construction supervision/inspection and a background in geology, soil science, or agronomy.
Typically, if a geotechnical consultant is already working on the project, the consultant may also be a
certified ESC professional designated as the CSWPP supervisor. The design engineer may also be
qualified for this position. This requirement shall only be used for sensitive sites that pose an unusually
high risk of impact to surface waters as determined by CED. At a minimum, the project site must meet all
of the following conditions in order to require the applicant to designate as the CSWPP supervisor a
certified ESC professional with such expertise:
Alderwood soils or other soils of Hydrologic Group C or D
Five acres of disturbance
Large areas (i.e., two or more acres) with slopes in excess of 10 percent.
Proximity to streams or wetlands or phosphorus-sensitive lakes, such as Lake Sammamish, shall also be a
factor in determining if such expertise in the CSWPP supervisor is warranted. However, proximity alone
shall not be a determining factor because even projects that are a considerable distance from surface
waters can result in significant impacts if there is a natural or constructed drainage system with direct
connections to surface waters.
The name, address, and phone number of the CSWPP supervisor shall be supplied to the City prior to the
start of construction. A sign shall be posted at all primary entrances to the site identifying the CSWPP
supervisor and his/her phone number. The requirement for a CSWPP supervisor does not relieve the
applicant of ultimate responsibility for the project and compliance with Renton Municipal Code.
D.2.3.2 MONITORING OF DISCHARGES
The CSWPP supervisor shall have a turbidity meter onsite and shall use it to monitor surface and storm
water discharges from the project site and into onsite wetlands, streams, or lakes whenever runoff occurs
from onsite activities and during storm events. The CSWPP supervisor shall keep a log of all turbidity
measurements taken onsite and make it available to CED upon request. If the project site is subject to a
NPDES general permit for construction issued by the Washington State Department of Ecology (Ecology),
then the project must comply with the monitoring requirements of that permit.
The CSWPP supervisor shall also use the specific SWPPS BMP procedures for monitoring surface and
stormwater discharge for pollutants and acceptable discharge levels. The CSWPP supervisor shall keep
logs as required by the procedures of all measurements taken onsite and make them available to CED on
request.
D.2.3.3 ESC PERFORMANCE
ESC measures shall be applied/installed and maintained so as to prevent, to the maximum extent
practicable, the transport of sediment from the project site to downstream drainage systems or surface
waters or into onsite wetlands, streams, or lakes or onto adjacent properties. This performance is intended
to be achieved through proper selection, installation, and operation of the above ESC measures as detailed
in the CSWPP Standards (Appendix D) and approved by the City. However, the CSWPP supervisor
designated per Section D.2.3.1 or the City may determine at any time during construction that such
approved measures are not sufficient and additional action is required based on one of the following
criteria:
1. IF a turbidity test of surface and storm water discharges leaving the project site is greater than the
benchmark value of 25 nephelometric turbidity units (NTU) set by the Washington State Department
of Ecology, but less than 250 NTU, the CSWPP Supervisor shall do all of the following:
a) Review the ESC plan for compliance and make appropriate revisions within 7 days of the
discharge that exceeded the benchmark of 25 NTU, AND
APPENDIX F
SITE IMPROVEMENT DRAWINGS
(SUBMITTED SEPARETLY)
APPENDIX G
ARBORIST REPORT
Arborist Report
Swarr Station (Security Perimeter Maintenance) - 07/2024 (Updated 10/2025)
Prepared
For:
Puget Sound Energy
355 110th Ave NE
Bellevue, WA 98004
Contact: Kathryn Hodges
206.549.7606
Kathryn.Hodges@pse.com
Prepared
By:
Davey Resource Group Inc.
18809 10th Ave NE
Shoreline, WA, 98155
Contact: Joe Sisneros
joe.sisneros@davey.com
Local Office: 206.331.0869
Corporate Office: 800.828.8312
Notice of Disclaimer
Assessment data provided by Davey Resource Group is based on visual recording at the time of inspection. Visual records do not
include testing or analysis and do not include aerial or subterranean inspection unless indicated. Davey Resource Group is not
responsible for discovery or identification of hidden or otherwise non-observable risks. Records may not remain accurate after
inspection due to variable deterioration of surveyed material. Risk ratings are based on observable defects and mitigation
recommendations do not reduce potential liability to the owner. Davey Resource Group provides no warranty with respect to the
fitness of the trees for any use or purpose whatsoever.
Table of Contents
Introduction 3
Limits of the Assignment 3
Methods 4
Observations 5
Overview 5
Tree Species 6
Proposed Tree Removals 7
Analysis & Recommendations 7
Priority Recommendations Related to Proposed Construction 7
Pre-Construction Tree Care 8
Tree Protection Zone & Timing 9
Tree Care During Construction 10
Post-Construction 11
Tree Credits 11
Concluding Remarks 13
Appendix A: Maps 15
Appendix B: Inventory Table 26
Appendix C: Tree Credits Table (Retained Trees) 62
Arborist Report - DRG Inc. Page 2 of 73 July 2024 (Updated October 2025)
Introduction
Davey Resource Group, Inc. (DRG) was contracted by Puget Sound Energy to inspect and provide an
arborist report and tree retention plan for Parcel Identification Number (PIN) 2023059071 at 2100 Benson
Dr. S in Renton, WA (Swarr Station - Security Perimeter Maintenance). The arborist’s assignment was to
inventory the significant trees (any tree at >6’’ at 4.5’ above grade) as defined by Renton Municipal Code 1
adjacent to the proposed fence replacement and provide PSE with a tree retention plan.
Using a pen tablet computer, a DRG International Society of Arboriculture (ISA) Certified Arborist
(PN-9382A) inventoried all the significant trees potentially impacted by construction on the property. This
included significant trees either a) 15 feet from the existing fence or b ) in areas where trees would be
impacted by new fence alignment as it deviates from the existing. Each tree was visually assessed, and
the required tree data was collected using a GIS database. Following data collection, specific tree
retention plan elements were calculated that identified each tree’s Tree Protection Zone (TPZ) to ensure
survivability during the planned development. The following details align with the information required by
RMC 4-4-130.
● A numbering system of the inspected regulated trees on the subject property.
● Tree type or species, and DSH (Diameter at 4.5’ above grade).
● A complete description of each tree’s health, condition, and viability.
● A description of the Tree Protection Zone (TPZ) and Critical Root Zone (CRZ) and how they were
calculated.
● Any special instructions for tree care when work may be required within the TPZ.
● Any trees requiring pruning or maintenance to increase tree tolerance to construction, clearance,
or safety on the site before construction.
● Maps detailing all tree locations, species, size (DSH), and the locations of all Tree Protection
Zones (TPZ) and Critical Root Zones (CRZ).
● Maps will clearly note all trees proposed for removal.
A Note on Revisions to this Arborist Report
(07/25) - Design changes shifted a portion of the fence construction along the west perimeter of the site to
be closer to the existing building. Revisions to the arborist report were developed to include additional
trees located near the new proposed limits of disturbance.
(10/25) - Revisions to the arborist report were developed to ensure consistency with the Tree Removal
Plan and the Excavation Zone Plan.
Limits of the Assignment
Many factors can limit specific and accurate data when performing evaluations of trees, their conditions,
and values. The determinations and recommendations presented here are based on current data and
conditions that existed at the time of the evaluation and cannot be a predictor of the ultimate outcomes for
the trees. A visual inspection was used to develop this report's findings, conclusions, and
recommendations. Values were assigned to grade the attributes of the trees, including structure and
canopy health, and to obtain an overall condition rating. No physical inspection of the upper canopy,
sounding, root crown excavation, resistograph, or other technologies were used to evaluate the trees.
1 Except red alder (Alnus rubra) and black cottonwood (Populus trichocarpa) trees, which qualify as significant trees
at 8’’ DSH or greater.
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Methods
Data was collected by an ISA Certified Arborist (PN-9382A) in June 2024. Note: The DRG arborist
revisited the site in June 2025 to add additional trees to the inventory (Tree ID#s 425-476). A visual
inspection was used to develop this report's findings, conclusions, and recommendations. The following
attributes were collected for each site:
Tree Number: A tree ID number was assigned, and a numbered aluminum tag was affixed to the tree.
Location and Unique ID: An X and Y coordinate was generated for each tree site.
Species: Trees were identified by genus and species, cultivar if evident, and by common name.
Diameter at Standard Height (DSH): Trunk diameter was recorded to the nearest inch at 4.5 ft above
grade. When limbs or deformities occurred at standard height, measurement was taken below 4.5 ft. The
DSH of multi-trunk trees was determined by taking the square root of the sum of the DSH for each
individual stem squared.
Landmark Trees: Per RMC 4-11-200, identification of any landmark tree with a DSH of twenty four
inches (24") or greater, except for big leaf maples, black cottonwoods, and red alder trees, which qualify
as landmark trees with a DSH of thirty inches (30") or greater.
Condition: Condition ratings were based on but not limited to (1) the condition and environment of the
tree’s root crown; (2) the condition of the trunk, including decay, injury, callusing, or presence of fungus
sporophore; (3) the condition of the limbs, including the strength of crotches, amount of deadwood, hollow
areas, and whether they bore excessive weight; (4) the condition and growth rate history of the twigs,
including pest damage and diseases; (5) the leaf appearance, including abnormal size and density as well
as pest and disease damage.
Using an average of the above factors together with the arborist’s best judgment, the general condition of
each tree was recorded in one of the following categories adapted from the rating system established by
the International Society of Arboriculture and 10th Edition of the Council of Tree & Landscape Appraisers
(CTLA) Guide for Plant Appraisal : 2
● Excellent: High vigor and near-perfect health with little or no twig dieback, discoloration, or
defoliation. It is nearly ideal and free of structural defects. It is a nearly ideal form for the species
and is generally symmetrical.
● Good: Vigor is normal for the species and has no significant damage due to disease or pests.
Twig dieback, discoloration, or defoliation is minor. Well-developed structure with minor defects
that can be corrected easily. Minor asymmetries/deviations from species norm. Function and
aesthetics are not compromised.
● Fair: Reduced vigor. Damage due to insects or diseases may be significant and associated with
defoliation but is not likely to be fatal. Twig dieback, defoliation, discoloration, and/or dead
branches may comprise up to 50% of the canopy. A single significant structural defect or multiple
moderate defects. Structural defects are not practical to correct or would require multiple
treatments over several years. Major asymmetries/deviations from species norm. Function and
aesthetics are compromised.
● Poor: Unhealthy and declining in appearance. Poor vigor, low foliage density, and poor foliage
color are present. Potentially fatal pest infestation. Extensive twig or branch dieback. A single
serious structural defect or multiple significant defects. Observed structural problems cannot be
2 Council of Tree and Landscape Appraisers. (2019). Guide for Plant Appraisal, 10th Edition, Second Printing. Atlanta, GA:
International Society of Arboriculture.
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corrected. Failure may occur at any time. Largely asymmetrical or abnormal form. Form detracts
from aesthetics or intended use to a significant degree.
● Very Poor: It has poor vigor and appears to be dying. There is little live foliage. There are single
or multiple severe structural defects. It is visually unappealing and provides little or no function in
the landscape.
● Dead
Tree Preservation Priority: To establish a priority for tree preservation as it relates to planning for
development projects, DRG utilized a rating scale of one to four, with one being the highest priority for
protection and four being of least value for protection. The condition rating of an individual tree is an
important component of the priority rating, but several other variables are factored in: species desirability,
species longevity, species sensitivity to root loss and construction impacts, uniqueness, and aesthetics
both of the tree itself and its relation to the site. It is important to note that these are qualitative ratings
based solely on the site, individual tree, and existing conditions at the time of the inventory. Proposed
development and construction plans are not considered when assigning ratings. The following criteria
constituted the basis of tree placement in a particular category of priority:
● Priority 1: Highest priority for protection (i.e. particularly good condition, unique tree, and/or
should be protected at all reasonable cost).
● Priority 2: Good or fair condition tree well worth protecting though not uniquely valuable.
● Priority 3: Poor condition average tree that will not be missed if it were gone, not worth any
special protection measures.
● Priority 4: Trees that should be removed under most or any circumstances (i.e., invasive or
undesirable species, poor condition or critical trees, particularly high-risk situations, etc.).
Observations
Overview
Site conditions were composed of a primarily forested landscape surrounding the existing and proposed
perimeter fencing locations at the PSE Swarr Station. Himalayan blackberry (Rubus armeniacus) and
English ivy (Hedera helix), both considered noxious weeds within King County, were pervasive throughout
the understory of the inspected area. A non-fish bearing, perennial stream runs northwards through the
parcel and sustains a buffer zone width of 75’ per RMC 4-3-050. A small length of this stream on the
southern end of the parcel is classified as non-fish bearing, seasonal stream, indicating that it sustains a
buffer zone width of 50’.
A total of three hundred and fifty-four (354) trees were inspected at and around the site. Two (2) trees
were in excellent condition. One hundred and one (101) trees were in good condition. One hundred and
sixty-six (166) trees were in fair condition. Fifty-six (56) trees were in poor condition. Sixteen (16) trees
were in very poor condition. Thirteen (13) trees were dead.
Out of the three hundred and fifty-four (354) inspected trees, two-hundred and eighty-four (284) trees
were considered significant trees, forty-seven (47) were considered landmark trees, and twenty-three (23)
were considered non-significant trees.
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Out of the three hundred and fifty-four (354) inspected trees, three hundred and forty-five (345) trees were
located within the parcel and nine (9) trees were overhanging the parcel. These nine (9) trees were
located along the southern perimeter of the parcel, with their trunks situated in the backyards of
neighboring residences.
Tree Species
Out of the three hundred and fifty-four (354) inspected trees, the most abundant species were Douglas fir
(Pseudotsuga menziesii, 92 trees) followed by bigleaf maple (Acer macrophyllum, 82 trees) and black
cottonwood (Populus trichocarpa, 72 trees). These three species comprised over 68% of the total
population. There were seventeen (17) unique tree species found at the site.
Chart 1: The twelve most abundant species at the project site.
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Proposed Tree Removals
To ensure safety of the worksite, forty-two (42) trees should be removed prior to the start of construction.
These trees are either dead or in poor/very poor condition and exhibited serious decline.
● These forty-two (42) trees are highlighted in yellow within Appendix B.
Per site plans, seventeen (17) trees are proposed for removal to accommodate the construction of the
new fence. These trees include:
● Tree ID#s 430, 431, 437, 444, 458, 459, 472, 473, 474, 5553, 5554, 5555, 5656, 5663, 5664,
5557, 5582. These seventeen (17) trees are highlighted in red within Appendix B.
Analysis & Recommendations
As with most tree preservation planning, a critical element is minimizing root disturbance. When
evaluating tree root disturbance during construction, there are two considerations: the removal of
absorption roots and the removal of anchoring roots. Removal (or compaction in the area) of the
absorption roots can cause immediate water stress and a significant decline in tree health. The ability of a
tree to survive the loss of absorption roots depends on its tolerance of drought, tree health, and the ability
to form new roots quickly. Removal of the larger anchoring roots can lead to structural instability. Trees
that suffer substantial root loss or damage are seldom good candidates for preservation.
The Critical Root Zone (CRZ) is considered the ideal preservation area of a tree's root zone and was
determined according to one (1) foot radius from the center point of the tree for each one (1) inch of tree
trunk diameter measured at the diameter at standard height (DSH). The inner critical root zone (ICRZ)
was determined to be the area of the inner half of the critical root zone diameter. No disturbance of
retained trees is allowed within the ICRZ. CRZ measurements are estimated and may not accurately
represent the actual dimensions of the root zone of the trees in the field. Many factors can limit root
growth and expansion, such as the degree of slope, the presence of hardscape or heavily compacted
areas, and/or tree health. Final selections for tree preservation are largely determined by the percentage
of the Outer Critical Root Zone impacted.
Priority Recommendations Related to Proposed
Construction
For all trees on the property proposed for retention, standard tree protection measures provided in
subsequent sections of this report will be appropriate. Exceptions will be required to accommodate
construction around trees that will have the proposed development project impact the CRZ.
● Per site plans, fence post hole excavation along the east, north and west perimeters of the site
will be occurring within the CRZs of many trees. The Excavation Zone Plan (Sheet C002)
highlights the specific CRZs that will be impacted. All soil excavation in these areas should be
conducted with an air spade and/or hydrovac system to minimize damage to any roots >2’’
diameter. It is recommended that the site arborist actively monitor all excavation work to advise
on root preservation and pruning.
○ All necessary root cuts (>2’’ diameter) should be completed by hand, resulting in a clean
cut. Any exposed roots should be covered with burlap and regularly wetted to retain
moisture if it is necessary to leave an excavation pit open.
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○ Per work specifications, fencing contractors will have the ability to adjust fence post
placement by a few feet if large roots are encountered that the site arborist recommends
for preservation. Each fence post excavation pit is anticipated to be limited to a 2.5’ width
by a 3.5’ depth.
○ To minimize soil compaction, wood chip mulch (as detailed later in this report) should be
applied to the CRZs of all the retained trees located near/adjacent to the fence post hole
excavation. Additionally, temporary ground protection matting can be applied to further
minimize soil compaction.
● Per site plans, minor crown raise pruning is necessary to ensure proper clearance from the new
fence. All clearance pruning is anticipated to remove no more than 10% of the overall canopies of
the retained trees.
○ All limb pruning cuts should be completed by hand, resulting in a clean cut just outside
the branch collar. All limb pruning should be supervised by an ISA Certified Arborist.
● There are numerous tree removals proposed along the west perimeter of the site, which is
currently a dense, tall stand of (primarily) Douglas fir (Pseudotsuga menziesii). Recognizing the
client’s objective to maintain screening in this area, the DRG arborist anticipates that the tree
density following the removals will remain sufficient to provide screening along Benson Dr S.
● Per site plans, soil excavation along/near the south perimeter of the site (near the existing
driveway) will remain outside the CRZs of the retained trees and/or will be occurring within an
existing gravel shoulder, indicating that no impact to these trees is anticipated.
● Numerous trees had English ivy (Hedera helix) growing up the trunk and/or into the canopy. To
improve the health and viability of these trees, it is recommended to remove the ivy by girdling the
ivy stems at the base of the trees. The specific trees with ivy coverage are identified within
Appendix B.
● Note: All trees situated on neighboring properties are remote from the proposed disturbance and
are not anticipated to be impacted.
Pre-Construction Tree Care
Successful tree preservation efforts begin in the planning and design phase. To select the appropriate
trees for preservation and then incorporate those trees into future development plans, site managers and
designers need detailed information on the health and status of the existing trees. This report satisfies the
conditions of the critical first step in the preservation process: a tree inventory, assessment, and analysis
conducted by a qualified professional. The resulting findings guide the beginning stages of the
preservation process.
Condition rating and preservation priority rating help nominate potential candidates for preservation.
Development plans should ensure that no impact or root damage occurs within the inner root zone, and
plans should consider the significant reduction in the likelihood of tree survival when the root zone is
impacted. After individual trees are selected for preservation, the following action steps are recommended
and/or required before development activities:
● Prune trees, as necessary, to remove existing deadwood and stubs. This strategy controls
potential future vectors of decay. Clean cuts made at branch collars allow the tree to undergo its
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natural process of compartmentalizing wounds, preventing the spread of decay. During the
pruning process, remove as minimal live foliage as possible and no more than 25% of it in any
one season while allowing for the safe and unimpeded operation of construction activities.
● If the soil within the TPZ is compacted, then aerate the soil using an air spade to alleviate
compaction and promote the flow of oxygen and water to the roots.
● Add a 3-inch layer of coarse arborist wood chips and/or construction mats to the root zone
protected by the TPZ. Be sure not to cover/bury the tree root collar. Mulch aids the soil in water
retention and also helps insulate the soil from hot and cold weather extremes. Wood chips and/or
construction mats will also reduce the impact of soil compaction from heavy equipment during the
upcoming construction activities
Tree Protection Zone & Timing
To ensure the long-term viability of trees and stands identified for protection, construction activities shall
comply with the minimum required tree protection through an established Tree Protection Zone (TPZ) for
those trees determined to remain on the site. All TPZ recommendations are in alignment with RMC
4-4-130.
● Fencing contractors will be excavating soil within the CRZs of numerous trees along the
east, north, and west perimeters of the site in order to install fence posts. Tree protection
standards will be met by utilizing active supervision by the site arborist as described in
the Priority Recommendations section of the report.
○ To avoid any hindrance to construction access, temporary chain-link fencing is not
necessary for these retained trees, and active supervision by the site arborist will
ensure minimal, code-compliant impact to the root systems.
○ The Excavation Zone Plan (Sheet C002) indicates the locations where best
management practices (excavation with hydrovac and/or air spade, wood chip
layer, construction mats) will be utilized to ensure impact to the CRZs of the
retained trees is minimized.
● All other inventoried trees on site are remote from the proposed disturbance indicating
that no temporary chain-link fencing is required.
● Although temporary chain-link fencing is not necessary for this project, the City of Renton
standards for tree protection fencing are detailed as follows for general reference: the applicant
should erect and maintain a six-foot (6') high, post-driven, chain-link temporary construction fence
around the drip lines of all retained trees, or if a tree protection tract or easement is provided,
along the perimeter of the tree protection tract or easement, prior to development activities. The
temporary tree protection fencing shall be installed with steel posts driven at a depth that will
adequately ensure the fence remains in an upright position for the duration of the development.
● The temporary tree protection fencing shall not be disturbed, removed, or relocated until the
conclusion of construction activities. Protected trees may be fenced individually or in groups of
trees. Individual trees shall be fenced on four (4) sides. If some tree or vegetation removal is
necessary in order to gain access to retained trees for the purposes of installing temporary tree
protection fencing, the applicant shall submit a phased tree removal plan for review and approval
by the Administrator, prior to all development activities.
● Signage shall be placed on the tree protection fencing at intervals of no more than twenty feet
(20') along the entirety of the protective tree fence. The sign(s) shall be designed, constructed,
and installed in accordance with official specifications provided by the Administrator and shall
convey the information deemed necessary by the Administrator.
● Any entry or work within the TPZ of retained trees is prohibited. This includes but is not limited to
the storage of materials, parking, or contaminating soil by washing out equipment.
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● If the grade level adjoining a tree to be retained is to be raised, the applicant shall construct a dry
rock wall or rock well around the tree. The diameter of this wall or well must be equal to the tree
drip line. Note: no grade changes are proposed within the CRZs of retained trees for this project.
● The grade level around any tree to be retained may not be lowered within the greater of the
following areas: (i) the area defined by the drip line of the tree, or (ii) an area around the tree
equal to one and one-half feet (1-1/2') in diameter for each one inch (1") of tree caliper. A larger
tree protection zone based on tree size, species, soil, or other conditions may be required.
● A minor extent of native understory plants near the retained trees may need to be trimmed
and/or temporarily covered with construction mats. With the exception of invasive species
removal which has received prior written approval from the City, removal of the existing
vegetation within the drip line of protected trees is prohibited during development activities. Native
understory trees, shrubs, and other vegetation shall be protected within the designated tree
protection area for the duration of the development activities.
● TPZ fencing should follow the edge of building/road/paved paths where necessary and is not
required to extend to the dripline where impervious surfaces are determined to be the limiting
factor for root development (fence following existing curb does not trigger ‘impact’ status). Tree
protection fencing may be installed at the edge of the impermeable or paved surfaces for those
trees whose driplines extend over the edge.
● Retain a site arborist for the duration of the project who may conduct periodic site visits to
investigate tree protection compliance and any changes to tree condition. The arborist shall
supervise the installation of any required tree protection fencing, permanent or temporary.
Tree Care During Construction
Once construction begins, several measures are necessary to help ensure optimal outcomes for all trees
selected for preservation:
● Retain a Certified Arborist on site to monitor activities and assess impacts on trees. The
arborist can make as-needed recommendations to improve tree preservation activities throughout
the development process. This is particularly important to respond promptly when a preserved
tree is accidentally damaged or otherwise impacted during development.
● Signage instructing site workers not to enter Tree Protection Zones throughout the job site is
recommended. Signage should be posted in English, Spanish, and any other language deemed
necessary by site managers.
● Discuss tree protection regularly at required staff meetings. Reiterate the importance of
respecting the Tree Protection Zone as critical to the safety of on-site staff and the success of
tree preservation efforts.
● Strictly enforce the Tree Protection Zones as “No-Go” zones. No activity, human or machinery,
should breach the established TPZ, unless under direct supervision of the site arborist and the
concurrent use of protective wood chip mulch and/or construction mats.
● Root prune where any grading or trenching occurs within the critical root zone.
● Ensure the area within the TPZ receives weekly watering equivalent to the average natural
rainfall for the specific development site. Manual watering methods should be employed when the
natural rainfall is less than the historical average. The on-site Certified Arborist can determine
when additional manual watering is necessary.
● Do not raise or lower the soil grade near the TPZ. A tree relies upon small, non-woody feeder
roots to absorb water and nutrients. These roots predominantly reside in the upper several inches
of soil, just below grade. Lowering the soil grade, even just a few inches, will sever these feeder
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roots and compromise tree health. Raising the soil above the existing grade, such as by adding
fill soil, buries feeder roots too deep and restricts feeder root access to water and oxygen.
Post-Construction
A successful tree preservation effort continues well past the conclusion of development activities:
● The preserved trees should be re-inspected for signs of impact that may have gone undetected
during construction, and mitigation measures should be assigned accordingly.
● The preserved trees should be placed on a two-year seasonal care plan that includes
continued monitoring.
Tree Credits
Per RMC 4-4-130-H, properties subject to an active land development permit shall retain a minimum of
thirty percent (30%) of all significant trees on site. Additionally, tree credit requirements shall apply at a
minimum rate of thirty (30) credits per net acre. To calculate the required tree credits, the square footage
of the subject lot was divided by 43,560 (the square footage of one acre). The resulting number is
multiplied by 30, the minimum tree credit requirement for one acre. Any fraction of credits was rounded up
to the next whole number from a 0.5 or greater value in calculating required tree credits. The parcel
measured approximately 727,887 square feet, indicating (727,887/43,560 = 16.7 x 30 = 501) a minimum
of 501 tree credits are required.
Per RMC 4-4-130-H, either tree retention or a combination of tree retention and supplemental tree
planting (with new small, medium, or large tree species) shall be provided to meet or exceed the minimum
tree credits required for the site. Supplemental tree planting shall consist of new small, medium, or large
species trees, as defined in RMC 4-11-200, Definitions T. The supplemental trees shall be planted with a
minimum size of two-inch (2") caliper, or evergreen trees with a minimum size of six feet (6') tall. Tree
credit values for existing and newly planted trees are shown in the table below.
Table 1: Tree Credit Values For New and Existing Trees
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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 16-18 caliper inches 7
Preserved tree 19-21 caliper inches 8
Preserved tree 22-24 caliper inches 9
Available Onsite Tree Credits
Per RMC 4-4-130-H, a total of 2061 tree credits were derived from all the inspected onsite trees
(Appendix C), exceeding the minimum requirement of 501 tree credits. This sum excludes the forty-two
(42) trees that are recommended for removal prior to construction due to safety concerns and the
seventeen (17) trees that are recommended for removal to accommodate the proposed construction. A
City of Renton Tree Retention and Credit Worksheet may need to be completed following final
confirmation of design plans. Note: a large population of non-inventoried significant trees exists
elsewhere within the parcel, particularly north of the proposed construction. This indicates that
the total number of tree credits onsite is significantly higher than the 2061 tree credits derived
from the inspected trees.
Image 1. Overview of subject parcel (highlighted in yellow), showcasing the large population of
non-inventoried significant trees situated elsewhere within the parcel. The inventoried trees are
generally located within the blue highlight.
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Preserved tree 25-28 caliper inches 10
Preserved tree 29-32 caliper inches 11
Preserved tree 33-36 caliper inches 12
Preserved tree 37 caliper inches and greater 13
Concluding Remarks
This report, along with the tree inventory, is the first step in preserving the health, function, and value of
the trees on the site during and after development. Trees and green spaces provide benefits and add
value to residential properties. Tree preservation starts with a basic understanding of the health and
structure of the trees on the site. With proper care and protection, these trees can continue to thrive. Tree
protection guidelines and strategies should be shared with contractors and employers before any
disturbance at the site.
The suitability of a tree for preservation is a qualitative process based on the interaction of various
influencing factors. A tree inventory and arborist report provide a snapshot of each individual tree
assessed across many of the most important observable factors relative to preservation. Healthy,
vigorous trees better tolerate impacts from construction and more readily adapt to the new site conditions
that exist after completion of development. Additionally, tolerance to impact from construction activities
varies across species and sites. The percentage impact on the tree protection zone also greatly
influences the suitability of a particular tree for preservation.
Numerous trees exhibited English ivy (Hedera helix) climbing up the trunk and/or into the canopy. This
invasive vine is a fast-growing species that can significantly damage and even kill the tree that it is
climbing. Recommended mitigation measures include severing the ivy stalks at the base of each afflicted
tree. This can result in most, if not all, of the ivy growing above the severed point to die and fall away. The
specific trees with significant ivy coverage are identified in Appendix B.
Successful tree preservation requires a team effort to find the right balance and select the appropriate
trees. Using this report's findings as a guiding foundation, planners can design, prepare, and implement a
tree preservation plan tailored to achieving the optimal outcome.
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Appendix A: Maps
Map A1. Overview of Site
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Map A2. Overview of Site
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Map A3. West Perimeter of Site
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Map A4. West Perimeter of Site
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Map A5. Northwest Perimeter of Site
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Map A6. Northeast Perimeter of Site
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Map A7. East Perimeter of Site
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Map A8. East Perimeter of Site
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Map A9. Southeast Perimeter of Site
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Map A10. Southeast Corner of Site
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Map A11. South Perimeter of Site
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Appendix B: Inventory Table
Table B1. Tree Inventory Table
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5530
Black cottonwood
(Populus
trichocarpa) 7 Fair 10 3 7 10
Non-Significa
nt Retain
Growing Into Fence,
Blackberry Climbing. 4
5531
Red alder (Alnus
rubra) 7 Good 8 2 7 8
Non-Significa
nt Retain 4
5532
Western red cedar
(Thuja plicata) 15 Fair 15 2 15 15 Significant Retain Minor Sapsucker Damage. 6
5533
Western red cedar
(Thuja plicata) 16 Fair 12 2 16 12 Significant Retain
Multistem Trunk. Minor
Sapsucker Damage. 7
5534
Western red cedar
(Thuja plicata) 12 Fair 12 2 12 12 Significant Retain
Multistem Trunk. Corrected
Lean, Uneven Crown. 5
5535
Western red cedar
(Thuja plicata) 21 Good 15 2 21 15 Significant Retain Minor Sapsucker Damage. 8
5536
Western red cedar
(Thuja plicata) 15 Good 15 2 15 15 Significant Retain Minor Sapsucker Damage. 6
5537
Red alder (Alnus
rubra) 9 Good 10 2 9 10 Significant Retain Corrected Lean. 4
5538
Western hemlock
(Tsuga
heterophylla) 20 Fair 15 3 20 15 Significant Retain
DSH Estimated, Not
Accessible. Growing Out of
Stump. 8
5539
Western red cedar
(Thuja plicata) 17 Good 15 2 17 15 Significant Retain Multistem Trunk. 7
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Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5540
Western red cedar
(Thuja plicata) 19 Good 15 2 19 15 Significant Retain 8
5541
Western red cedar
(Thuja plicata) 20 Good 15 2 20 15 Significant Retain Multistem Trunk. 8
5542
Western red cedar
(Thuja plicata) 19 Fair 15 2 19 15 Significant Retain
Multistem Trunk, Uneven
Crown. 8
5543
Western hemlock
(Tsuga
heterophylla) 12 Fair 12 2 12 12 Significant Retain Uneven Crown. 5
5544
Western red cedar
(Thuja plicata) 16 Fair 12 2 16 12 Significant Retain
Multistem Trunk, Uneven
Crown. 7
5545
Western red cedar
(Thuja plicata) 15 Good 12 2 15 12 Significant Retain 6
5546
Western red cedar
(Thuja plicata) 11 Fair 10 2 11 10 Significant Retain Uneven Crown. 5
5547
Western red cedar
(Thuja plicata) 6 Good 8 3 6 8 Significant Retain Poor Taper. 4
5548
Western red cedar
(Thuja plicata) 11 Good 10 2 11 10 Significant Retain 5
5549
Western red cedar
(Thuja plicata) 15 Good 15 2 15 15 Significant Retain Minor Sapsucker Damage. 6
5550
Western red cedar
(Thuja plicata) 13 Excellent 15 2 13 15 Significant Retain 6
5551
Western red cedar
(Thuja plicata) 14 Good 15 2 14 15 Significant Retain Minor Sapsucker Damage. 6
5552
Western red cedar
(Thuja plicata) 27 Fair 20 2 27 20 Landmark Retain
Multistem Trunk, Uneven
Crown. Broken Top. 10
Arborist Report - DRG Inc. Page 26 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5553
Wild cherry (Prunus
avium) 22 Poor 25 3 22 25 Significant Remove
Multistem Trunk, Uneven
Crown. Significant Ivy
Coverage. 9
5554
Shore pine (Pinus
contorta) 20 Poor 12 3 20 12 Significant Remove
Sprase, Uneven Crown.
Significant Ivy Coverage. 8
5555
Shore pine (Pinus
contorta) 16 Poor 15 3 16 15 Significant Remove
Sparse, Uneven Crown.
Significant Ivy Coverage. 7
5556
Douglas fir
(Pseudotsuga
menziesii) 27 Good 25 1 27 25 Landmark Retain Uneven Crown. 10
5557
Douglas fir
(Pseudotsuga
menziesii) 20 Fair 15 2 20 15 Significant Remove Uneven Crown. 8
5558
Shore pine (Pinus
contorta) 19 Fair 15 3 19 15 Significant Retain
Sparse Crown, Forked
Top. 8
5559
Douglas fir
(Pseudotsuga
menziesii) 17 Fair 15 2 17 15 Significant Retain Uneven Crown. 7
5560
Douglas fir
(Pseudotsuga
menziesii) 16 Fair 15 2 16 15 Significant Retain Uneven Crown. 7
5561
Douglas fir
(Pseudotsuga
menziesii) 13 Fair 12 3 13 12 Significant Retain
Uneven Crown, Corrected
Lean. 6
5562
Douglas fir
(Pseudotsuga
menziesii) 13 Fair 12 2 13 12 Significant Retain Uneven Crown. 6
Arborist Report - DRG Inc. Page 27 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5563
Douglas fir
(Pseudotsuga
menziesii) 16 Fair 12 2 16 12 Significant Retain Uneven Crown. 7
5564
Douglas fir
(Pseudotsuga
menziesii) 10 Poor 10 3 10 10 Significant Retain Sparse Crown, Poor Taper. 5
5565
Douglas fir
(Pseudotsuga
menziesii) 21 Fair 15 2 21 15 Significant Retain Uneven Crown. 8
5566
Douglas fir
(Pseudotsuga
menziesii) 21 Fair 15 2 21 15 Significant Retain Uneven Crown. 8
5567
Shore pine (Pinus
contorta) 11 Poor 12 4 11 12 Significant Remove
Multistem Trunk. Uneven
Crown, Poor Structure. Not
Safe To Leave As Snag. 5
5568
Shore pine (Pinus
contorta) 12 Poor 10 3 12 10 Significant Retain
Uneven, Sparse Crown.
Poor Structure. 5
5569
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 15 2 15 15 Significant Retain Uneven Crown. 6
5570
Scots pine (Pinus
sylvestris) 12 Poor 10 3 12 10 Significant Retain
Uneven, Sparse Crown.
Poor Structure. Minor
Sapsucker Damage. 5
5571
Douglas fir
(Pseudotsuga
menziesii) 13 Fair 12 2 13 12 Significant Retain Uneven Crown. 6
5572
Shore pine (Pinus
contorta) 19 Fair 20 2 19 20 Significant Retain Uneven Crown. 8
Arborist Report - DRG Inc. Page 28 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5573
Douglas fir
(Pseudotsuga
menziesii) 21 Good 15 2 21 15 Significant Retain 8
5574
Douglas fir
(Pseudotsuga
menziesii) 10 Fair 12 2 10 12 Significant Retain Uneven Crown. 5
5575
Bigleaf maple (Acer
macrophyllum) 8 Fair 20 2 8 20 Significant Retain
Multistem Trunk. Uneven
Crown, Suppressed. 4
5576
Oregon ash
(Fraxinus latifolia) 8 Good 10 2 8 10 Significant Retain Multistem Trunk. 4
5577
Douglas fir
(Pseudotsuga
menziesii) 13 Good 10 2 13 10 Significant Retain 6
5578
Douglas fir
(Pseudotsuga
menziesii) 21 Good 12 2 21 12 Significant Retain Corrected Lean. 8
5579
Douglas fir
(Pseudotsuga
menziesii) 14 Good 10 2 14 10 Significant Retain 6
5580
Douglas fir
(Pseudotsuga
menziesii) 10 Fair 8 3 10 8 Significant Retain
Uneven Crown, Poor
Taper. 5
5581
Douglas fir
(Pseudotsuga
menziesii) 21 Fair 15 2 21 15 Significant Retain Uneven Crown. 8
5582
Shore pine (Pinus
contorta) 14 Poor 10 3 14 10 Significant Remove
Sparse Crown, Poor
Structure. 6
Arborist Report - DRG Inc. Page 29 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5583
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 12 2 15 12 Significant Retain Uneven, Sparse Crown. 6
5584
Douglas fir
(Pseudotsuga
menziesii) 16 Good 12 2 16 12 Significant Retain 7
5585
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 12 2 15 12 Significant Retain Uneven Crown. 6
5586
Shore pine (Pinus
contorta) 14 Poor 10 3 14 10 Significant Retain
Poor Structure, Sparse
Crown. 6
5587
Shore pine (Pinus
contorta) 7 Poor 10 3 7 10 Significant Retain
Poor Structure, Sparse
Crown. Uneven Crown. 4
5588
Douglas fir
(Pseudotsuga
menziesii) 16 Good 12 2 16 12 Significant Retain Full Crown. 7
5589
Scots pine (Pinus
sylvestris) 13 Poor 10 4 13 10 Significant Remove
Broken Top, Uneven
Crown. Poor Structure. Not
Safe To Leave As Snag. 6
5590
Douglas fir
(Pseudotsuga
menziesii) 17 Good 15 2 17 15 Significant Retain 7
5591
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 12 3 15 12 Significant Retain
Uneven Crown, Minor
Uncorrected Lean To
West. 6
5592
Douglas fir
(Pseudotsuga
menziesii) 9 Poor 8 4 9 8 Significant Remove
Uncorrected Lean To
West, Uneven Crown. Not
Safe To Leave As Snag. 4
Arborist Report - DRG Inc. Page 30 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5593
Red alder (Alnus
rubra) 5 Poor 10 3 5 10
Non-Significa
nt Retain
Suppressed, Poor Taper.
Sparse Crown. 0
5594
Red alder (Alnus
rubra) 9 Dead 0 4 9 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 4
5595
Red alder (Alnus
rubra) 7 Dead 0 4 7 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 4
5596
Red alder (Alnus
rubra) 11 Fair 10 3 11 10 Significant Retain Poor Taper, Sparse Crown. 5
5597
Red alder (Alnus
rubra) 10 Poor 12 3 10 12 Significant Retain
Poor Taper, Corrected
Lean. 5
5598
Red alder (Alnus
rubra) 10 Fair 15 2 10 15 Significant Retain Corrected Lean. 5
5599
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 12 3 12 12 Significant Retain Poor Taper, Sparse Crown. 5
5600
Red alder (Alnus
rubra) 10 Fair 10 3 10 10 Significant Retain
Multistem Trunk, Poor
Taper. Uncorrected Lean,
Uneven Crown. 5
5601
Bigleaf maple (Acer
macrophyllum) 30 Fair 30 1 30 30 Landmark Retain
Multistem Trunk. Large, 4'
Wide Cavity At Base Of
Trunk. Good Response
Growth. 11
5602
Bigleaf maple (Acer
macrophyllum) 7 Poor 15 3 7 15 Significant Retain
Multistem Trunk. Corrected
Lean, Uneven Crown, Poor
Taper. 4
Arborist Report - DRG Inc. Page 31 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5603
Douglas fir
(Pseudotsuga
menziesii) 21 Good 20 1 21 20 Significant Retain
Structural Roots Likely
Stabilizing Slope. 8
5604
Douglas fir
(Pseudotsuga
menziesii) 6 Poor 6 3 6 6 Significant Retain Poor Taper, Sparse Crown. 4
5605
Douglas fir
(Pseudotsuga
menziesii) 21 Fair 20 1 21 20 Significant Retain
Minor Insect Damage.
Structural Roots Likely
Stabilizing Slope. 8
5606
Douglas fir
(Pseudotsuga
menziesii) 9 Dead 0 4 9 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 4
5607
Douglas fir
(Pseudotsuga
menziesii) 8 Poor 10 4 8 10 Significant Remove
Broken Top, Poor
Structure, Uneven Crown.
Not Safe To Leave As
Snag. 4
5608
Douglas fir
(Pseudotsuga
menziesii) 14 Fair 12 2 14 12 Significant Retain
Uneven Crown, Corrected
Lean. 6
5609
Douglas fir
(Pseudotsuga
menziesii) 25 Fair 20 2 25 20 Landmark Retain Forked Top. 10
5610
Douglas fir
(Pseudotsuga
menziesii) 10 Fair 10 2 10 10 Significant Retain Sparse, Uneven Crown. 5
5611
Douglas fir
(Pseudotsuga
menziesii) 14 Good 15 2 14 15 Significant Retain 6
Arborist Report - DRG Inc. Page 32 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5612
Douglas fir
(Pseudotsuga
menziesii) 19 Good 12 2 19 12 Significant Retain Uneven Crown. 8
5613
Douglas fir
(Pseudotsuga
menziesii) 11 Fair 10 3 11 10 Significant Retain
Poor Structure, Corrected
Lean. 5
5614
Douglas fir
(Pseudotsuga
menziesii) 25 Good 20 2 25 20 Landmark Retain Uneven Crown. 10
5615
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 15 3 12 15 Significant Retain Uneven Crown. 5
5616
Douglas fir
(Pseudotsuga
menziesii) 19 Good 15 2 19 15 Significant Retain Uneven Crown. 8
5617
Grand fir (Abies
grandis) 22 Good 18 1 22 18 Significant Retain Uneven Crown. 9
5618
Douglas fir
(Pseudotsuga
menziesii) 26 Good 20 1 26 20 Landmark Retain Uneven Crown. 10
5619
Douglas fir
(Pseudotsuga
menziesii) 14 Fair 15 2 14 15 Significant Retain Uneven Crown. 6
5620
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 12 2 12 12 Significant Retain
Suppressed, Sparse
Crown. 5
Arborist Report - DRG Inc. Page 33 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5621
Douglas fir
(Pseudotsuga
menziesii) 19 Good 15 2 19 15 Significant Retain 8
5622
Douglas fir
(Pseudotsuga
menziesii) 19 Good 15 2 19 15 Significant Retain Uneven Crown. 8
5623
Douglas fir
(Pseudotsuga
menziesii) 11 Poor 15 3 11 15 Significant Retain
Uneven Crown. Fruiting
Bodies On Trunk, Poor
Structure. 5
5624
Douglas fir
(Pseudotsuga
menziesii) 11 Very Poor 8 4 11 8 Significant Remove
Poor Taper, Very Sparse
Crown. Can Leave As
Snag. 5
5625
Douglas fir
(Pseudotsuga
menziesii) 15 Good 15 2 15 15 Significant Retain Uneven Crown. 6
5626
Douglas fir
(Pseudotsuga
menziesii) 18 Good 15 1 18 15 Significant Retain Minor Sap Flow. 7
5627
Douglas fir
(Pseudotsuga
menziesii) 23 Good 20 1 23 20 Significant Retain
Minor Insect Frass On
Trunk. 9
5628
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 10 2 12 10 Significant Retain Uneven Crown. 5
5629
Black cottonwood
(Populus
trichocarpa) 17 Good 25 2 17 25 Significant Retain Full Crown. 7
Arborist Report - DRG Inc. Page 34 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5630
Western red cedar
(Thuja plicata) 29 Fair 25 2 29 25 Landmark Retain
Multistem Trunk. Minor
Sapsucker Damage. 11
5631
Black cottonwood
(Populus
trichocarpa) 48 Good 30 1 48 30 Landmark Retain
DSH Estimated, Not
Accessible. Growing Up
Against Fence. 13
5632
Bigleaf maple (Acer
macrophyllum) 28 Good 35 2 28 35 Significant Retain
Multistem Trunk. Full
Crown. 10
5633
Oregon ash
(Fraxinus latifolia) 19 Good 30 2 19 30 Significant Retain 8
5634
Bitter cherry
(Prunus
emarginata) 8 Dead 0 4 8 0
Non-Significa
nt Remove Can Leave As Snag. 4
5635 Willow (Salix spp.) 11 Very Poor 8 4 11 8 Significant Remove
Trunk Rot, Broken Top,
Large Dead Limbs. Can
Leave As Small Snag. 5
5636 Apple (Malus spp.) 10 Poor 10 3 10 10 Significant Retain
Significant Sapsucker
Damage, Poor Structure,
Sparse Crown. 5
5637
Bitter cherry
(Prunus
emarginata) 13 Fair 15 3 13 15 Significant Retain
Sparse Crown, Poor
Structure. 6
5638
Bitter cherry
(Prunus
emarginata) 16 Dead 0 4 16 0
Non-Significa
nt Remove Can Leave As Snag. 7
5639
Bigleaf maple (Acer
macrophyllum) 12 Fair 15 3 12 15 Significant Retain
Multistem Trunk. Weak
Unions, Rot On Smaller
Stem. 5
Arborist Report - DRG Inc. Page 35 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5640
Bitter cherry
(Prunus
emarginata) 11 Fair 10 3 11 10 Significant Retain
Multistem Trunk. Corrected
Lean, Uneven Crown. 5
5641
Bigleaf maple (Acer
macrophyllum) 15 Good 20 2 15 20 Significant Retain Uneven Crown. 6
5642
Bigleaf maple (Acer
macrophyllum) 10 Good 20 2 10 20 Significant Retain
Uneven Crown. Poor
Taper. 5
5643
Bigleaf maple (Acer
macrophyllum) 10 Fair 20 2 10 20 Significant Retain
Uneven Crown. Poor
Taper. 5
5644
Bigleaf maple (Acer
macrophyllum) 36 Fair 25 3 36 25 Landmark Retain
Multistem Trunk. Previous
Stem Failures. Poor
Structure. 12
5645
Bigleaf maple (Acer
macrophyllum) 19 Fair 30 2 19 30 Significant Retain
Multistem Trunk. Poor
Taper, Uneven Crown. 8
5646
Bigleaf maple (Acer
macrophyllum) 17 Good 25 2 17 25 Significant Retain Multistem Trunk. 7
5647
Bigleaf maple (Acer
macrophyllum) 12 Fair 20 3 12 20 Significant Retain
Uneven Crown, Poor
Taper. 5
5648
Bigleaf maple (Acer
macrophyllum) 14 Good 25 2 14 25 Significant Retain Poor Taper. 6
5649
Bigleaf maple (Acer
macrophyllum) 24 Fair 30 2 24 30 Significant Retain
Multistem Trunk. Poor
Structure. 9
5650
Bigleaf maple (Acer
macrophyllum) 22 Fair 30 2 22 30 Significant Retain
Multistem Trunk. Poor
Structure, Rot On One
Stem. 9
5651
Bigleaf maple (Acer
macrophyllum) 14 Good 20 2 14 20 Significant Retain Full Crown. 6
Arborist Report - DRG Inc. Page 36 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5652
Bigleaf maple (Acer
macrophyllum) 14 Good 25 2 14 25 Significant Retain
Full Crown, Corrected
Lean. 6
5653
Shore pine (Pinus
contorta) 10 Dead 0 4 10 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 5
5654
Shore pine (Pinus
contorta) 11 Poor 8 3 11 8 Significant Retain
Poor Structure, Sparse
Crown. Significant Ivy
Coverage. 5
5655
Western red cedar
(Thuja plicata) 11 Excellent 15 1 11 15 Significant Retain 5
5656
Western red cedar
(Thuja plicata) 17 Good 15 1 17 15 Significant Remove Multistem Trunk. 7
5657
Red alder (Alnus
rubra) 5 Dead 0 4 5 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag, Leaning Towards
Fencing. 0
5658
Black cottonwood
(Populus
trichocarpa) 23 Good 20 2 23 20 Significant Retain Significant Ivy Coverage. 9
5659
Bitter cherry
(Prunus
emarginata) 8 Very Poor 0 4 8 0 Significant Remove
Peeling Bark, No Live
Crown. Not Safe To Leave
As Snag. 4
5660
Black cottonwood
(Populus
trichocarpa) 29 Fair 20 2 29 20 Significant Retain Significant Ivy Coverage. 11
5661
Oregon ash
(Fraxinus latifolia) 6 Poor 12 3 6 12 Significant Retain
Uneven Crown. Significant
Ivy Coverage. 4
5662
Western red cedar
(Thuja plicata) 9 Good 15 2 9 15 Significant Retain Significant Ivy Coverage. 4
Arborist Report - DRG Inc. Page 37 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5663
Western red cedar
(Thuja plicata) 11 Good 15 2 11 15 Significant Remove Significant Ivy Coverage. 5
5664
Western red cedar
(Thuja plicata) 10 Fair 10 3 10 10 Significant Remove Multistem Trunk. 5
5665
Black cottonwood
(Populus
trichocarpa) 39 Good 30 1 39 30 Landmark Retain
Full Crown, Tree Is
Eroding Into Stream Bank. 13
5666 Willow (Salix spp.) 6 Poor 8 4 6 8 Significant Remove
Poor Structure, Trunk Rot.
Not Safe To Leave As
Snag. 4
5667
Black cottonwood
(Populus
trichocarpa) 34 Good 20 1 34 20 Landmark Retain 12
5668
Oregon ash
(Fraxinus latifolia) 7 Fair 10 2 7 10 Significant Retain
Uneven Crown, Poor
Taper. 4
5669
Black cottonwood
(Populus
trichocarpa) 34 Good 30 1 34 30 Landmark Retain Full Crown. 12
5670
Oregon ash
(Fraxinus latifolia) 11 Fair 25 3 11 25 Significant Retain
Uneven Crown, Corrected
Lean. 5
5671
Bigleaf maple (Acer
macrophyllum) 7 Fair 15 2 7 15 Significant Retain
Uneven Crown, Poor
Taper. 4
5672
Bigleaf maple (Acer
macrophyllum) 5 Good 12 2 5 12
Non-Significa
nt Retain Poor Taper. 0
5673
Common hawthorn
(Crataegus
monogyna) 6 Good 10 3 6 10 Significant Retain 4
Arborist Report - DRG Inc. Page 38 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5674 Willow (Salix spp.) 13 Very Poor 15 4 13 15 Significant Remove
Poor Structure, Resting
Against Fence. Active
Trunk Rot. Not Safe To
Leave As Snag. 6
5675
Bigleaf maple (Acer
macrophyllum) 6 Poor 10 4 6 10 Significant Remove
Poor Taper. Uneven,
Sparse Crown. Not Safe
To Leave As Snag. 4
5676
Bigleaf maple (Acer
macrophyllum) 5 Very Poor 10 4 5 10
Non-Significa
nt Remove
Uncorrected Lean, Large
Dead Tree Resting On it.
Not Safe To Leave As
Snag. 0
5677
Red alder (Alnus
rubra) 7 Dead 0 4 7 0
Non-Significa
nt Remove
Uncorrected Lean. Not
Safe To Leave As Snag. 4
5678
Black cottonwood
(Populus
trichocarpa) 39 Good 35 1 39 35 Landmark Retain
Full Crown, Large
Structural Root Growing
Through Fence. 13
5679
Bigleaf maple (Acer
macrophyllum) 10 Poor 15 3 10 15 Significant Retain
Multistem Trunk. Poor
Structure, Large Dead
Limbs. Uneven Crown. 5
5680
Bigleaf maple (Acer
macrophyllum) 5 Fair 12 3 5 12
Non-Significa
nt Retain
Uneven Crown, Poor
Taper. Growing Out Of
Tree ID# 5680. 0
5681
Bigleaf maple (Acer
macrophyllum) 6 Fair 15 3 6 15 Significant Retain
Poor Taper, Uneven
Crown. 4
5682
Black cottonwood
(Populus
trichocarpa) 55 Good 40 1 55 40 Landmark Retain
DSH Estimated, Not
Accessible. Forked Top,
Full Crown. 13
Arborist Report - DRG Inc. Page 39 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5683
Black cottonwood
(Populus
trichocarpa) 38 Fair 25 2 38 25 Landmark Retain Uneven Crown. 13
5684
Bigleaf maple (Acer
macrophyllum) 8 Poor 10 4 8 10 Significant Remove
Large Dead Limb, Poor
Structure, Trunk Rot. Can
Leave As Snag. 4
5685
Bigleaf maple (Acer
macrophyllum) 10 Fair 12 2 10 12 Significant Retain
Poor Taper, Uneven
Crown. 5
5686
Bigleaf maple (Acer
macrophyllum) 7 Poor 10 3 7 10 Significant Retain
Poor Structure,
Suppressed. Uneven
Crown. 4
5687
Bigleaf maple (Acer
macrophyllum) 9 Fair 15 2 9 15 Significant Retain
Poor Structure,
Suppressed. Uneven
Crown. 4
5688
Black cottonwood
(Populus
trichocarpa) 46 Good 35 1 46 35 Landmark Retain Full Crown. 13
5689
Shore pine (Pinus
contorta) 9 Poor 8 4 9 8 Significant Remove
Sparse Crown, Serious
Decline. Not Safe To
Leave As Snag. 4
5690
Black cottonwood
(Populus
trichocarpa) 30 Good 20 2 30 20 Landmark Retain Uneven Crown. 11
5691
Black cottonwood
(Populus
trichocarpa) 20 Good 15 2 20 15 Significant Retain Uneven Crown. 8
Arborist Report - DRG Inc. Page 40 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5692
Black cottonwood
(Populus
trichocarpa) 21 Fair 15 2 21 15 Significant Retain
Uneven Crown, Corrected
Lean. 8
5693
Black cottonwood
(Populus
trichocarpa) 23 Fair 15 2 23 15 Significant Retain
Poor Structure, Broken
Top. 9
5694
Black cottonwood
(Populus
trichocarpa) 29 Fair 15 3 29 15 Significant Retain
Uneven Crown, Corrected
Lean. 11
5695
Bigleaf maple (Acer
macrophyllum) 7 Fair 15 3 7 15 Significant Retain
Poor Structure, Poor
Taper. 4
5696
Bigleaf maple (Acer
macrophyllum) 17 Fair 35 3 17 35 Significant Retain
Uncorrected Lean, Uneven
Crown. 7
5697
Black cottonwood
(Populus
trichocarpa) 20 Fair 15 2 20 15 Significant Retain Corrected Lean. 8
5698
Bigleaf maple (Acer
macrophyllum) 12 Fair 20 2 12 20 Significant Retain
Uneven Crown, Poor
Structure. 5
5699
Black cottonwood
(Populus
trichocarpa) 27 Fair 15 2 27 15 Significant Retain
Corrected Lean, Uneven
Crown. 10
5700
Black cottonwood
(Populus
trichocarpa) 34 Fair 20 2 34 20 Landmark Retain Uneven Crown. 12
5701
Black cottonwood
(Populus
trichocarpa) 21 Good 20 2 21 20 Significant Retain Full Crown. 8
Arborist Report - DRG Inc. Page 41 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5702
Black cottonwood
(Populus
trichocarpa) 17 Good 15 2 17 15 Significant Retain 7
5703
Bigleaf maple (Acer
macrophyllum) 16 Fair 20 2 16 20 Significant Retain
Multistem Trunk. Poor
Structure, Uneven Crown. 7
5704
Black cottonwood
(Populus
trichocarpa) 31 Fair 20 3 31 20 Landmark Retain Uneven, Sparse Crown. 11
5705
Black cottonwood
(Populus
trichocarpa) 17 Poor 8 4 17 8 Significant Remove
Sparse Crown, Serious
Decline. Not Safe To
Leave As Snag. 7
5706
Bigleaf maple (Acer
macrophyllum) 11 Fair 20 2 11 20 Significant Retain
Uneven Crown, Corrected
Lean. 5
5707
Black cottonwood
(Populus
trichocarpa) 35 Fair 20 2 35 20 Landmark Retain Uneven Crown. 12
5708
Bigleaf maple (Acer
macrophyllum) 6 Fair 10 3 6 10 Significant Retain
Poor Taper, Uneven
Crown. 4
5709
Bigleaf maple (Acer
macrophyllum) 7 Fair 15 3 7 15 Significant Retain
Poor Taper, Uneven
Crown. 4
5710
Bigleaf maple (Acer
macrophyllum) 7 Fair 10 3 7 10 Significant Retain Poor Taper, Sparse Crown. 4
5711
Bigleaf maple (Acer
macrophyllum) 6 Poor 12 3 6 12 Significant Retain
Poor Structure, Uneven
Crown. Corrected Lean. 4
5712
Bigleaf maple (Acer
macrophyllum) 9 Good 15 2 9 15 Significant Retain Uneven Crown. 4
Arborist Report - DRG Inc. Page 42 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5713
Black cottonwood
(Populus
trichocarpa) 22 Fair 15 2 22 15 Significant Retain Uneven Crown. 9
5714
Bigleaf maple (Acer
macrophyllum) 6 Fair 12 3 6 12 Significant Retain
Poor Taper, Sparse,
Uneven Crown. 4
5715
Black cottonwood
(Populus
trichocarpa) 25 Fair 20 2 25 20 Significant Retain
Uneven Crown, Poor
Taper. 10
5716
Bigleaf maple (Acer
macrophyllum) 6 Fair 15 3 6 15 Significant Retain
Uneven Crown, Poor
Taper. 4
5717
Black cottonwood
(Populus
trichocarpa) 24 Good 20 2 24 20 Significant Retain Full Crown. 9
5718
Black cottonwood
(Populus
trichocarpa) 33 Fair 25 2 33 25 Landmark Retain
Multistem Trunk. Full
Crown. 12
5719
Bigleaf maple (Acer
macrophyllum) 7 Fair 10 3 7 10 Significant Retain
Uneven Crown, Corrected
Lean. 4
5720
Black cottonwood
(Populus
trichocarpa) 13 Poor 10 4 13 10 Significant Remove
Dead Top, Serious
Decline. Not Safe To
Leave As Snag. 6
5721
Black cottonwood
(Populus
trichocarpa) 19 Good 15 2 19 15 Significant Retain 8
5722
Black cottonwood
(Populus
trichocarpa) 31 Good 25 2 31 25 Landmark Retain
Uneven Crown, Corrected
Lean. 11
Arborist Report - DRG Inc. Page 43 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5723
Black cottonwood
(Populus
trichocarpa) 28 Fair 20 2 28 20 Significant Retain
Multistem Trunk. Minor
Basal Rot, Corrected Lean. 10
5724
Black cottonwood
(Populus
trichocarpa) 21 Fair 25 2 21 25 Significant Retain
Uneven Crown, Corrected
Lean. 8
5725
Bigleaf maple (Acer
macrophyllum) 6 Fair 12 2 6 12 Significant Retain
Full Crown, Large Dead
Stem. 4
5726
Black cottonwood
(Populus
trichocarpa) 18 Fair 15 2 18 15 Significant Retain Poor Structure. 7
5727
Black cottonwood
(Populus
trichocarpa) 33 Fair 25 2 33 25 Landmark Retain Uneven Crown. 12
5728
Black cottonwood
(Populus
trichocarpa) 13 Dead 0 4 13 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 6
5729
Black cottonwood
(Populus
trichocarpa) 10 Fair 15 3 10 15 Significant Retain
Uneven Crown,
Uncorrected Lean. 5
5730
Black cottonwood
(Populus
trichocarpa) 14 Good 20 2 14 20 Significant Retain Uneven Crown. 6
5731
Black cottonwood
(Populus
trichocarpa) 8 Dead 0 4 8 0
Non-Significa
nt Remove
Not Safe To Leave As
Snag. 4
Arborist Report - DRG Inc. Page 44 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5732
Black cottonwood
(Populus
trichocarpa) 22 Poor 20 4 22 20 Significant Remove
Uneven Crown, Broken
Top. Corrected Lean. Not
Safe To Leave As Snag. 9
5733
Black cottonwood
(Populus
trichocarpa) 13 Fair 12 3 13 12 Significant Retain Uneven, Sparse Crown. 6
5734
Bigleaf maple (Acer
macrophyllum) 9 Fair 12 3 9 12 Significant Retain
Corrected Lean. Large
Dead Tree From Upslope
Leaning Against It. 4
5735
Black cottonwood
(Populus
trichocarpa) 19 Fair 15 2 19 15 Significant Retain
Uneven Crown, Corrected
Lean. 8
5736
Black cottonwood
(Populus
trichocarpa) 16 Dead 0 4 16 0
Non-Significa
nt Remove
Trunk Failure. Not Safe To
Leave As Snag. 7
5737
Bigleaf maple (Acer
macrophyllum) 6 Good 15 2 6 15 Significant Retain Suppressed. 4
5738
Black cottonwood
(Populus
trichocarpa) 18 Fair 10 3 18 10 Significant Retain
Poor Taper, Sparse Crown.
Corrected Lean. 7
5739
Black cottonwood
(Populus
trichocarpa) 24 Good 15 2 24 15 Significant Retain 9
5740
Black cottonwood
(Populus
trichocarpa) 13 Fair 15 2 13 15 Significant Retain
Uneven Crown, Corrected
Lean. 6
5741
Bigleaf maple (Acer
macrophyllum) 6 Fair 10 2 6 10 Significant Retain Uneven Crown. 4
Arborist Report - DRG Inc. Page 45 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5742
Black cottonwood
(Populus
trichocarpa) 9 Very Poor 3 4 9 3 Significant Remove
Little Live Crown, Dead
Top, Peeling Bark. Not
Safe To Leave As Snag. 4
5743
Black cottonwood
(Populus
trichocarpa) 18 Fair 20 3 18 20 Significant Retain
Uneven Crown, Corrected
Lean. Poor Structure. 7
5744
Black cottonwood
(Populus
trichocarpa) 32 Good 30 1 32 30 Landmark Retain Full Crown. 11
5745
Black cottonwood
(Populus
trichocarpa) 16 Good 12 2 16 12 Significant Retain Full Crown. 7
5746
Black cottonwood
(Populus
trichocarpa) 19 Good 12 2 19 12 Significant Retain Corrected Lean. 8
5747
Black cottonwood
(Populus
trichocarpa) 14 Fair 12 3 14 12 Significant Retain Corrected Lean. 6
5748
Black cottonwood
(Populus
trichocarpa) 20 Good 12 2 20 12 Significant Retain Corrected Lean. 8
5749
Black cottonwood
(Populus
trichocarpa) 33 Fair 30 2 33 30 Landmark Retain
Uneven Crown, Corrected
Lean. 12
5750
Bigleaf maple (Acer
macrophyllum) 19 Fair 30 3 19 30 Significant Retain
Multistem Trunk. Uneven
Crown, Poor Structure. 8
Arborist Report - DRG Inc. Page 46 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5751
Bigleaf maple (Acer
macrophyllum) 11 Very Poor 5 4 11 5 Significant Remove
Dead Top, Little Live
Crown. Can Leave As
Snag. 5
5752
Bigleaf maple (Acer
macrophyllum) 18 Poor 15 4 18 15 Significant Remove
Multistem Trunk. Uneven
Crown, Broken Top. Can
Leave As Snag. 7
5753
Black cottonwood
(Populus
trichocarpa) 24 Fair 17 2 24 17 Significant Retain
Uneven, Sparse Crown.
Poor Taper. 9
5754
Western red cedar
(Thuja plicata) 18 Fair 20 2 18 20 Significant Retain
DSH Estimated. Growing
Out of Stump. 7
5755
Black cottonwood
(Populus
trichocarpa) 26 Fair 12 2 26 12 Significant Retain
Sparse Crown. Significant
Ivy Coverage. 10
5756
Black cottonwood
(Populus
trichocarpa) 16 Fair 10 2 16 10 Significant Retain
Significant Ivy Coverage.
Poor Taper. 7
5757
Bigleaf maple (Acer
macrophyllum) 14 Fair 20 2 14 20 Significant Retain
Poor Structure, Uneven
Crown. 6
5758
Bigleaf maple (Acer
macrophyllum) 12 Poor 20 3 12 20 Significant Retain
Multistem Trunk. Poor
Structure, Uneven Crown. 5
5759
Black cottonwood
(Populus
trichocarpa) 27 Fair 25 2 27 25 Significant Retain
Uneven Crown, Corrected
Lean. 10
5760
Black cottonwood
(Populus
trichocarpa) 27 Fair 25 2 27 25 Significant Retain
Uneven Crown, Corrected
Lean. 10
Arborist Report - DRG Inc. Page 47 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5761
Black cottonwood
(Populus
trichocarpa) 21 Fair 12 2 21 12 Significant Retain
Uneven Crown, Corrected
Lean. 8
5762
Oregon ash
(Fraxinus latifolia) 12 Dead 0 4 12 0
Non-Significa
nt Remove Can Leave As Snag. 5
5763
Bigleaf maple (Acer
macrophyllum) 13 Poor 17 3 13 17 Significant Retain
Uneven Crown, Poor
Structure. 6
5764
Black cottonwood
(Populus
trichocarpa) 38 Good 30 1 38 30 Landmark Retain
Large Structural Roots
Growing Through Fence. 13
5765
Western red cedar
(Thuja plicata) 25 Very Poor 10 4 25 10 Landmark Remove
Uneven Crown, Trunk Rot,
Poor Structure. Can Leave
As Snag. 10
5766
Black cottonwood
(Populus
trichocarpa) 36 Good 25 2 36 25 Landmark Retain Sparse Crown. 12
5767
Black cottonwood
(Populus
trichocarpa) 39 Fair 30 2 39 30 Landmark Retain
Multistem Trunk. Uneven
Crown, Corrected Lean. 13
5768 Willow (Salix spp.) 7 Very Poor 3 4 7 3 Significant Remove
Uncorrected Lean Onto
Fence. Sparse Crown,
Trunk Rot. Leave As Snag. 4
5769
Oregon ash
(Fraxinus latifolia) 7 Fair 12 2 7 12 Significant Retain Poor Structure. 4
5770
Bigleaf maple (Acer
macrophyllum) 16 Poor 20 4 16 20 Significant Remove
Multistem Trunk. Previous
Large Stem Failure,
Fruiting Bodies. Poor 7
Arborist Report - DRG Inc. Page 48 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
Structure. Not Safe To
Leave As Snag.
5771
Bigleaf maple (Acer
macrophyllum) 19 Fair 17 3 19 17 Significant Retain
Multistem Trunk. Previous
Large Stem Failure, Poor
Structure. 8
5772
Black cottonwood
(Populus
trichocarpa) 23 Fair 17 2 23 17 Significant Retain
Poor Structure, Uneven
Crown. 9
5773
Oregon ash
(Fraxinus latifolia) 10 Poor 10 3 10 10 Significant Retain Significant Crown Dieback. 5
5774
Black cottonwood
(Populus
trichocarpa) 32 Fair 20 2 32 20 Landmark Retain
Uneven Crown, Corrected
Lean. 11
5775
Oregon ash
(Fraxinus latifolia) 9 Good 12 2 9 12 Significant Retain Full Crown. 4
5776
Black cottonwood
(Populus
trichocarpa) 24 Fair 15 2 24 15 Significant Retain Corrected Lean. 9
5777
Western red cedar
(Thuja plicata) 7 Good 10 2 7 10 Significant Retain 4
5778
Bigleaf maple (Acer
macrophyllum) 12 Poor 10 3 12 10 Significant Retain
Multistem Trunk. Poor
Taper, Dead Top. 5
5779
Bigleaf maple (Acer
macrophyllum) 6 Fair 10 3 6 10 Significant Retain
Uneven Crown, Poor
Structure. Dead Top. 4
5780
Bigleaf maple (Acer
macrophyllum) 8 Fair 15 2 8 15 Significant Retain Uneven Crown. 4
Arborist Report - DRG Inc. Page 49 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5781
Bigleaf maple (Acer
macrophyllum) 8 Very Poor 6 4 8 6 Significant Remove
Severe Trunk Rot, Poor
Structure, Sparse Crown.
Can Leave As Snag. 4
5782
Bigleaf maple (Acer
macrophyllum) 11 Very Poor 15 4 11 15 Significant Remove
Broken Top, Sparse
Crown. Can Leave As
Snag. 5
5783
Bigleaf maple (Acer
macrophyllum) 18 Fair 30 2 18 30 Significant Retain
Multistem Trunk. Trunk
Rot, Dead Limb. 7
5784
Western red cedar
(Thuja plicata) 22 Good 17 2 22 17 Significant Retain 9
5785
Bigleaf maple (Acer
macrophyllum) 14 Fair 20 2 14 20 Significant Retain Sparse Crown. 6
5786
Bitter cherry
(Prunus
emarginata) 6 Fair 10 3 6 10 Significant Retain
Multistem Trunk. Small
Cavity In Trunk. 4
5787
Bigleaf maple (Acer
macrophyllum) 9 Good 15 2 9 15 Significant Retain 4
5788
Black cottonwood
(Populus
trichocarpa) 19 Very Poor 15 4 19 15 Significant Remove
Significant Ivy Coverage.
Sparse, Uneven Crown.
Dead Top. Can Leave As
Snag. 8
5789
Western hemlock
(Tsuga
heterophylla) 9 Dead 0 4 9 0
Non-Significa
nt Remove Can Leave As Snag. 4
5790
Bigleaf maple (Acer
macrophyllum) 16 Fair 30 2 16 30 Significant Retain Uneven Crown. 7
Arborist Report - DRG Inc. Page 50 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5791
Bigleaf maple (Acer
macrophyllum) 19 Poor 20 3 19 20 Significant Retain
Multistem Trunk. Sparse
Crown, Poor Structure. 11''
DSH Dead Stem. 8
5792
Oregon ash
(Fraxinus latifolia) 23 Poor 15 3 23 15 Significant Retain
Significant Ivy Coverage,
Very Little Live Crown. 9
5793
Bigleaf maple (Acer
macrophyllum) 18 Poor 10 3 18 10 Significant Retain
Significant Ivy Coverage,
Very Little Live Crown. 7
5794
Black cottonwood
(Populus
trichocarpa) 28 Poor 25 3 28 25 Significant Retain
Significant Ivy Coverage,
Uneven Crown. 10
5795
Western red cedar
(Thuja plicata) 12 Good 20 1 12 20 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 5
5796
Bigleaf maple (Acer
macrophyllum) 10 Fair 25 1 10 25 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 5
5797
Western red cedar
(Thuja plicata) 7 Fair 15 1 7 15 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 4
5798
Red alder (Alnus
rubra) 17 Fair 20 1 17 20 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 7
5799
Bigleaf maple (Acer
macrophyllum) 20 Good 35 1 20 35 Significant Retain Full Crown. 8
5800
Bigleaf maple (Acer
macrophyllum) 12 Fair 20 2 12 20 Significant Retain
Uneven Crown, Poor
Taper. 5
9960
Oregon ash
(Fraxinus latifolia) 25 Fair 20 2 25 20 Landmark Retain
Multistem Trunk. Sparse
Crown, Poor Taper. Minor
Sapsucker Damage. 10
Arborist Report - DRG Inc. Page 51 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
9961
Bigleaf maple (Acer
macrophyllum) 15 Very Poor 15 4 15 15 Significant Remove
Broken Top, Trunk Rot,
Sparse Crown. Can Leave
As Snag. 6
9962
Bigleaf maple (Acer
macrophyllum) 29 Poor 25 3 29 25 Significant Retain
Multistem Trunk. Fruiting
Bodies On Trunk, Poor
Structure, Sparse Crown. 11
9963
Lawson cypress
(Chamaecyparis
lawsoniana) 16 Good 25 1 16 25 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 7
9964
Lawson cypress
(Chamaecyparis
lawsoniana) 11 Good 15 1 11 15 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 5
9965
Bigleaf maple (Acer
macrophyllum) 19 Good 25 1 19 25 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 8
9966
Lawson cypress
(Chamaecyparis
lawsoniana) 17 Good 20 1 17 20 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 7
9967
Bigleaf maple (Acer
macrophyllum) 15 Poor 20 3 15 20 Significant Retain
Multistem Trunk. Poor
Structure, Sparse Crown. 6
9968
Oregon ash
(Fraxinus latifolia) 19 Fair 20 2 19 20 Significant Retain
Significant Ivy Coverage,
Sparse Crown. 8
9969
Western red cedar
(Thuja plicata) 10 Good 12 2 10 12 Significant Retain Significant Ivy Coverage. 5
9970
Western red cedar
(Thuja plicata) 26 Poor 20 3 26 20 Landmark Retain
Significant Ivy Coverage,
Sparse Crown. 10
9971
Bigleaf maple (Acer
macrophyllum) 8 Poor 12 3 8 12 Significant Retain
Significant Ivy Coverage,
Very Little Live Crown. 4
Arborist Report - DRG Inc. Page 52 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
9972
Western red cedar
(Thuja plicata) 20 Good 20 1 20 20 Significant Retain
Overhanging, DSH
Estimated, Not Tagged. 8
9973
Oregon ash
(Fraxinus latifolia) 12 Fair 17 2 12 17 Significant Retain Uneven Crown. 5
9974
Oregon ash
(Fraxinus latifolia) 11 Poor 20 3 11 20 Significant Retain
Uneven Crown.
Suppressed, Cavity In
Trunk. 5
9975
Black cottonwood
(Populus
trichocarpa) 70 Good 45 1 70 45 Landmark Retain
Multistem Trunk. Forked
Top On Larger Stem. 13
9976
Black cottonwood
(Populus
trichocarpa) 46 Good 35 1 46 35 Landmark Retain Full Crown. 13
9977
Bigleaf maple (Acer
macrophyllum) 10 Poor 15 3 10 15 Significant Retain
Broken Top, Poor
Structure, Uneven Crown. 5
9978
Oregon ash
(Fraxinus latifolia) 8 Fair 12 3 8 12 Significant Retain
Multistem Trunk, Poor
Structure. 4
9979
Grand fir (Abies
grandis) 13 Very Poor 10 4 13 10 Significant Remove
Dead Top, Sparse Crown,
Severe Dieback. Can
Leave As Snag. 6
5801
Bigleaf maple (Acer
macrophyllum) 11 Poor 10 3 11 10 Significant Retain
Poor Structure, Broken
Top, Uneven Crown. 5
5802
Bigleaf maple (Acer
macrophyllum) 22 Very Poor 20 4 22 20 Significant Remove
Forked Top, Previous Stem
Failure, Severe Trunk Rot.
Can Leave As Snag. 9
Arborist Report - DRG Inc. Page 53 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5803 Willow (Salix spp.) 7 Poor 12 3 7 12 Significant Retain
Multistem Trunk. Poor
Structure, Cavities In
Trunk. 4
5804
Bigleaf maple (Acer
macrophyllum) 7 Very Poor 12 4 7 12 Significant Remove
DSH Estimated, Not
Tagged, Inaccessible.
Crown Dieback, Large
Dead Stem, Poor
Structure. Can Leave As
Snag. 4
5805
Black cottonwood
(Populus
trichocarpa) 45 Good 25 2 45 25 Landmark Retain
Full Crown. Could Be
Prone To Dropping Limbs
On New Fence. 13
5806
Bigleaf maple (Acer
macrophyllum) 22 Poor 25 3 22 25 Significant Retain
Multistem Trunk. Uneven
Crown, Cavity In Trunk,
Corrected Lean. 9
5807
Bigleaf maple (Acer
macrophyllum) 20 Fair 25 2 20 25 Significant Retain
Multistem Trunk. Poor
Structure, Uneven Crown. 8
5800
Oregon ash
(Fraxinus latifolia) 19 Fair 20 2 19 20 Significant Retain
DSH Estimated, Not
Tagged, Inaccessible.
Significant Blackberry
Coverage. 8
5809
Bitter cherry
(Prunus
emarginata) 7 Good 10 3 7 10 Significant Retain
DSH Estimated, Not
Tagged, Inaccessible.
Significant Blackberry
Coverage. 4
5810
Common hawthorn
(Crataegus
monogyna) 10 Good 15 3 10 15 Significant Retain
DSH Estimated, Not
Tagged, Inaccessible.
Significant Blackberry
Coverage. 5
Arborist Report - DRG Inc. Page 54 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
5811
Common hawthorn
(Crataegus
monogyna) 10 Good 10 3 10 10 Significant Retain
DSH Estimated, Not
Tagged, Inaccessible.
Significant Blackberry
Coverage. 5
425
Scots pine (Pinus
sylvestris) 12 Fair 8 3 12 Significant Retain
Suppressed, Crook In
Trunk. Low LCR, Ivy. 5
426
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 12 2 18 Significant Retain
Uneven Crown, Ivy, Small
Deadwood. 7
427
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 10 2 15 Significant Retain
Uneven Crown, Small
Deadwood. 6
428
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 12 2 18 Significant Retain
Uneven Crown, Small
Deadwood. 7
429
Douglas fir
(Pseudotsuga
menziesii) 19 Fair 15 2 19 Significant Retain
Uneven Crown, Small
Deadwood. Ivy, Large 8''
Diameter Surface Root
Running East. 8
430
Douglas fir
(Pseudotsuga
menziesii) 17 Fair 10 2 17 Significant Remove
Uneven Crown, Ivy, Low
LCR, Suppressed, Small
Deadwood. 7
431
Douglas fir
(Pseudotsuga
menziesii) 32 Good 20 2 32 Landmark Remove
Uneven Crown, Minor
Corrected Lean, Ivy, Small
Deadwood. Large 8''
Diameter Surface Root
Historically Damaged By
Landscaping. 11
Arborist Report - DRG Inc. Page 55 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
432
Red alder (Alnus
rubra) 6 Fair 6 3 6
Not
Significant Retain Corrected Lean, Low LCR. 4
433
Red alder (Alnus
rubra) 6 Fair 8 3 6
Not
Significant Retain
Corrected Lean, Poor
Crown Structure, Low
LCR, Minor Physical
Damage To Trunk. 4
434
Red alder (Alnus
rubra) 6 Fair 8 3 6
Not
Significant Retain
Uneven Crown, Corrected
Lean, Poor Crown
Structure. 4
435
Red alder (Alnus
rubra) 6 Fair 10 3 6
Not
Significant Retain
Uneven Crown, Corrected
Lean, Low LCR. 4
436
Bigleaf maple (Acer
marcophyllum) 7 Fair 20 3 7 Significant Retain
Uneven Crown, Poor
Crown Structure. 4
437
Bigleaf maple (Acer
marcophyllum) 6 Fair 12 3 6 Significant Remove
Uneven Crown, Poor
Crown Structure,
Corrected Lean. 4
438
Douglas fir
(Pseudotsuga
menziesii) 23 Fair 20 2 23 Significant Retain
Uneven Crown, Small
Deadwood. 9
439
Douglas fir
(Pseudotsuga
menziesii) 20 Good 15 2 20 Significant Retain
Modest LCR, Small
Deadwood. 8
440
Douglas fir
(Pseudotsuga
menziesii) 11 Poor 8 3 11 Significant Retain
Uneven Crown,
Suppressed, Low LCR, Ivy,
Small Deadwood. 5
441
Douglas fir
(Pseudotsuga
menziesii) 22 Good 20 2 22 Significant Retain
Uneven Crown, Small
Deadwood. 9
Arborist Report - DRG Inc. Page 56 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
442
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 10 3 18 Significant Retain
Low LCR, Uneven Crown,
Ivy, Small Deadwood. 7
443
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 8 3 15 Significant Retain
Uneven Crown, Low LCR,
Small Deadwood. 6
444
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 12 3 12 Significant Remove
Uneven Crown, Poor
Taper, Small Deadwood. 5
445
Douglas fir
(Pseudotsuga
menziesii) 13 Fair 10 2 13 Significant Retain
Uneven Crown, Small
Deadwood. 6
446
Douglas fir
(Pseudotsuga
menziesii) 26 Good 25 2 26 Landmark Retain
Uneven Crown, Small
Deadwood. 10
447
Douglas fir
(Pseudotsuga
menziesii) 12 Fair 10 3 12 Significant Retain
Suppressed, Uneven
Crown, Small Deadwood,
Low LCR. 5
448
Douglas fir
(Pseudotsuga
menziesii) 24 Good 15 2 24 Landmark Retain
Modest LCR, Small
Deadwood. 9
449
Douglas fir
(Pseudotsuga
menziesii) 9 Poor 6 3 9 Significant Retain
Broken Top, Low LCR,
Uneven Crown, Small
Deadwood. 4
450
Douglas fir
(Pseudotsuga
menziesii) 26 Fair 15 2 26 Landmark Retain
Uneven Crown, Minor
Corrected Lean, Small
Deadwood, Thinning
Crown. 10
Arborist Report - DRG Inc. Page 57 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
451
Douglas fir
(Pseudotsuga
menziesii) 13 Fair 10 2 13 Significant Retain
Uneven Crown, Small
Deadwood, Poor Taper. 6
452
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 12 2 18 Significant Retain
Uneven Crown, Small
Deadwood, Minor
Corrected Lean. 7
453
Douglas fir
(Pseudotsuga
menziesii) 19 Fair 15 2 19 Significant Retain
Uneven Crown, Small
Deadwood. 8
454
Douglas fir
(Pseudotsuga
menziesii) 12 Poor 8 3 12 Significant Retain
Uneven Crown, Low LCR,
Suppressed, Poor Taper,
Small Deadwood. 5
455
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 12 2 18 Significant Retain
Uneven Crown, Small
Deadwood, Modest LCR. 7
456
Douglas fir
(Pseudotsuga
menziesii) 15 Fair 10 2 15 Significant Retain
Uneven Crown, Small
Deadwood. 6
457
Douglas fir
(Pseudotsuga
menziesii) 20 Good 15 2 20 Significant Retain
Modest LCR, Small
Deadwood. 8
458
Douglas fir
(Pseudotsuga
menziesii) 23 Fair 15 2 23 Significant Remove
Uneven Crown, Minor
Corrected Lean, Small
Deadwood. 9
459
Douglas fir
(Pseudotsuga
menziesii) 25 Fair 20 2 25 Landmark Remove
Uneven Crown, Crook In
Trunk, Small Deadwood. 10
Arborist Report - DRG Inc. Page 58 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
460
Douglas fir
(Pseudotsuga
menziesii) 21 Fair 12 2 21 Significant Retain
Uneven Crown, Small
Deadwood. 8
461
Douglas fir
(Pseudotsuga
menziesii) 12 Poor 8 3 12 Significant Retain
Uneven Crown, Broken
Top, Low LCR. 5
462
Douglas fir
(Pseudotsuga
menziesii) 24 Good 20 2 24 Landmark Retain
Modest LCR, Uneven
Crown, Small Deadwood. 9
463
Douglas fir
(Pseudotsuga
menziesii) 25 Good 15 2 25 Landmark Retain
Uneven Crown, Small
Deadwood. 10
464
Douglas fir
(Pseudotsuga
menziesii) 30 Good 20 2 30 Landmark Retain
Uneven Crown, Small
Deadwood. 11
465
Douglas fir
(Pseudotsuga
menziesii) 25 Good 15 2 25 Landmark Retain
Slightly Uneven Crown,
Small Deadwood. 10
466
Douglas fir
(Pseudotsuga
menziesii) 20 Fair 10 2 20 Significant Retain
Uneven Crown, Small
Deadwood, Low LCR. 8
467
Douglas fir
(Pseudotsuga
menziesii) 19 Fair 10 2 19 Significant Retain
Uneven Crown, Low LCR,
Small Deadwood. 8
468
Douglas fir
(Pseudotsuga
menziesii) 18 Fair 12 2 18 Significant Retain
Low LCR, Small
Deadwood, Burls At Base. 7
Arborist Report - DRG Inc. Page 59 of 73 July 2024 (Updated October 2025)
Tree
ID# Species DSH (in) Condition
Avg
Canop
y
Radius
(ft)
Preservation
Priority
CRZ
Radius
(ft)
TPZ
Radiu
s (ft)
RMC Status Proposed Action Comments Tree
Credits
469
Douglas fir
(Pseudotsuga
menziesii) 22 Fair 10 2 22 Significant Retain
Uneven Crown, Small
Deadwood. 9
470
Douglas fir
(Pseudotsuga
menziesii) 23 Fair 12 2 23 Significant Retain
Uneven Crown, Small
Deadwood. 9
471
Grand fir (Abies
grandis) 32 Good 20 2 32 Landmark Retain Slightly Uneven Crown. 11
472
Bigleaf maple (Acer
macrophyllum) 14 Fair 15 2 14 Significant Remove
Uneven Crown, Poor
Taper. 6
473
Bigleaf maple (Acer
macrophyllum) 33 Fair 30 2 33 Landmark Remove
Multistem Trunk, Crown
Dieback, Weak Stem
Unions At Base, Large
Deadwood, Stem Decay
(With Woundwood),
Uneven Crown. 12
474 Willow (Salix spp.) 21 Poor 10 4 21 Significant Remove
Multistem Trunk. All Stems
Historically Failed, New
Shoots Response Growth,
Uneven Crown, Decay
Throughout Stems. 8
475
Deodar cedar
(Cedrus deodara) 32 Fair 25 2 32 Landmark Retain
Uneven Crown, Forked
Top, Thin Crown,
Corrected Lean. 11
476
Douglas fir
(Pseudotsuga
menziesii) 7 Poor 6 2 7 Significant Retain
Suppressed, Low LCR,
Uneven Crown, Small
Deadwood. 4
Arborist Report - DRG Inc. Page 60 of 73 July 2024 (Updated October 2025)
Appendix C: Tree Credits Table (Retained Trees)
Table C1. Tree Credits Table For Onsite Inspected Trees (Excludes Trees Currently Recommended For Removal)
Arborist Report - DRG Inc. Page 61 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5530 Black cottonwood (Populus trichocarpa) 7 4
5531 Red alder (Alnus rubra) 7 4
5532 Western red cedar (Thuja plicata) 15 6
5533 Western red cedar (Thuja plicata) 16 7
5534 Western red cedar (Thuja plicata) 12 5
5535 Western red cedar (Thuja plicata) 21 8
5536 Western red cedar (Thuja plicata) 15 6
5537 Red alder (Alnus rubra) 9 4
5538 Western hemlock (Tsuga heterophylla) 20 8
5539 Western red cedar (Thuja plicata) 17 7
5540 Western red cedar (Thuja plicata) 19 8
5541 Western red cedar (Thuja plicata) 20 8
5542 Western red cedar (Thuja plicata) 19 8
5543 Western hemlock (Tsuga heterophylla) 12 5
5544 Western red cedar (Thuja plicata) 16 7
5545 Western red cedar (Thuja plicata) 15 6
5546 Western red cedar (Thuja plicata) 11 5
5547 Western red cedar (Thuja plicata) 6 4
5548 Western red cedar (Thuja plicata) 11 5
5549 Western red cedar (Thuja plicata) 15 6
5550 Western red cedar (Thuja plicata) 13 6
Arborist Report - DRG Inc. Page 62 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5551 Western red cedar (Thuja plicata) 14 6
5552 Western red cedar (Thuja plicata) 27 10
5556 Douglas fir (Pseudotsuga menziesii) 27 10
5558 Shore pine (Pinus contorta) 19 8
5559 Douglas fir (Pseudotsuga menziesii) 17 7
5560 Douglas fir (Pseudotsuga menziesii) 16 7
5561 Douglas fir (Pseudotsuga menziesii) 13 6
5562 Douglas fir (Pseudotsuga menziesii) 13 6
5563 Douglas fir (Pseudotsuga menziesii) 16 7
5564 Douglas fir (Pseudotsuga menziesii) 10 5
5565 Douglas fir (Pseudotsuga menziesii) 21 8
5566 Douglas fir (Pseudotsuga menziesii) 21 8
5568 Shore pine (Pinus contorta) 12 5
5569 Douglas fir (Pseudotsuga menziesii) 15 6
5570 Scots pine (Pinus sylvestris) 12 5
5571 Douglas fir (Pseudotsuga menziesii) 13 6
5572 Shore pine (Pinus contorta) 19 8
5573 Douglas fir (Pseudotsuga menziesii) 21 8
5574 Douglas fir (Pseudotsuga menziesii) 10 5
5575 Bigleaf maple (Acer macrophyllum) 8 4
5576 Oregon ash (Fraxinus latifolia) 8 4
5577 Douglas fir (Pseudotsuga menziesii) 13 6
5578 Douglas fir (Pseudotsuga menziesii) 21 8
5579 Douglas fir (Pseudotsuga menziesii) 14 6
5580 Douglas fir (Pseudotsuga menziesii) 10 5
Arborist Report - DRG Inc. Page 63 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5581 Douglas fir (Pseudotsuga menziesii) 21 8
5583 Douglas fir (Pseudotsuga menziesii) 15 6
5584 Douglas fir (Pseudotsuga menziesii) 16 7
5585 Douglas fir (Pseudotsuga menziesii) 15 6
5586 Shore pine (Pinus contorta) 14 6
5587 Shore pine (Pinus contorta) 7 4
5588 Douglas fir (Pseudotsuga menziesii) 16 7
5590 Douglas fir (Pseudotsuga menziesii) 17 7
5591 Douglas fir (Pseudotsuga menziesii) 15 6
5593 Red alder (Alnus rubra) 5 0
5596 Red alder (Alnus rubra) 11 5
5597 Red alder (Alnus rubra) 10 5
5598 Red alder (Alnus rubra) 10 5
5599 Douglas fir (Pseudotsuga menziesii) 12 5
5600 Red alder (Alnus rubra) 10 5
5601 Bigleaf maple (Acer macrophyllum) 30 11
5602 Bigleaf maple (Acer macrophyllum) 7 4
5603 Douglas fir (Pseudotsuga menziesii) 21 8
5604 Douglas fir (Pseudotsuga menziesii) 6 4
5605 Douglas fir (Pseudotsuga menziesii) 21 8
5608 Douglas fir (Pseudotsuga menziesii) 14 6
5609 Douglas fir (Pseudotsuga menziesii) 25 10
5610 Douglas fir (Pseudotsuga menziesii) 10 5
5611 Douglas fir (Pseudotsuga menziesii) 14 6
5612 Douglas fir (Pseudotsuga menziesii) 19 8
Arborist Report - DRG Inc. Page 64 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5613 Douglas fir (Pseudotsuga menziesii) 11 5
5614 Douglas fir (Pseudotsuga menziesii) 25 10
5615 Douglas fir (Pseudotsuga menziesii) 12 5
5616 Douglas fir (Pseudotsuga menziesii) 19 8
5617 Grand fir (Abies grandis) 22 9
5618 Douglas fir (Pseudotsuga menziesii) 26 10
5619 Douglas fir (Pseudotsuga menziesii) 14 6
5620 Douglas fir (Pseudotsuga menziesii) 12 5
5621 Douglas fir (Pseudotsuga menziesii) 19 8
5622 Douglas fir (Pseudotsuga menziesii) 19 8
5623 Douglas fir (Pseudotsuga menziesii) 11 5
5625 Douglas fir (Pseudotsuga menziesii) 15 6
5626 Douglas fir (Pseudotsuga menziesii) 18 7
5627 Douglas fir (Pseudotsuga menziesii) 23 9
5628 Douglas fir (Pseudotsuga menziesii) 12 5
5629 Black cottonwood (Populus trichocarpa) 17 7
5630 Western red cedar (Thuja plicata) 29 11
5631 Black cottonwood (Populus trichocarpa) 48 13
5632 Bigleaf maple (Acer macrophyllum) 28 10
5633 Oregon ash (Fraxinus latifolia) 19 8
5636 Apple (Malus spp.) 10 5
5637 Bitter cherry (Prunus emarginata) 13 6
5639 Bigleaf maple (Acer macrophyllum) 12 5
5640 Bitter cherry (Prunus emarginata) 11 5
5641 Bigleaf maple (Acer macrophyllum) 15 6
Arborist Report - DRG Inc. Page 65 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5642 Bigleaf maple (Acer macrophyllum) 10 5
5643 Bigleaf maple (Acer macrophyllum) 10 5
5644 Bigleaf maple (Acer macrophyllum) 36 12
5645 Bigleaf maple (Acer macrophyllum) 19 8
5646 Bigleaf maple (Acer macrophyllum) 17 7
5647 Bigleaf maple (Acer macrophyllum) 12 5
5648 Bigleaf maple (Acer macrophyllum) 14 6
5649 Bigleaf maple (Acer macrophyllum) 24 9
5650 Bigleaf maple (Acer macrophyllum) 22 9
5651 Bigleaf maple (Acer macrophyllum) 14 6
5652 Bigleaf maple (Acer macrophyllum) 14 6
5654 Shore pine (Pinus contorta) 11 5
5655 Western red cedar (Thuja plicata) 11 5
5658 Black cottonwood (Populus trichocarpa) 23 9
5660 Black cottonwood (Populus trichocarpa) 29 11
5661 Oregon ash (Fraxinus latifolia) 6 4
5662 Western red cedar (Thuja plicata) 9 4
5665 Black cottonwood (Populus trichocarpa) 39 13
5667 Black cottonwood (Populus trichocarpa) 34 12
5668 Oregon ash (Fraxinus latifolia) 7 4
5669 Black cottonwood (Populus trichocarpa) 34 12
5670 Oregon ash (Fraxinus latifolia) 11 5
5671 Bigleaf maple (Acer macrophyllum) 7 4
5672 Bigleaf maple (Acer macrophyllum) 5 0
5673
Common hawthorn (Crataegus
monogyna) 6 4
Arborist Report - DRG Inc. Page 66 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5678 Black cottonwood (Populus trichocarpa) 39 13
5679 Bigleaf maple (Acer macrophyllum) 10 5
5680 Bigleaf maple (Acer macrophyllum) 5 0
5681 Bigleaf maple (Acer macrophyllum) 6 4
5682 Black cottonwood (Populus trichocarpa) 55 13
5683 Black cottonwood (Populus trichocarpa) 38 13
5685 Bigleaf maple (Acer macrophyllum) 10 5
5686 Bigleaf maple (Acer macrophyllum) 7 4
5687 Bigleaf maple (Acer macrophyllum) 9 4
5688 Black cottonwood (Populus trichocarpa) 46 13
5690 Black cottonwood (Populus trichocarpa) 30 11
5691 Black cottonwood (Populus trichocarpa) 20 8
5692 Black cottonwood (Populus trichocarpa) 21 8
5693 Black cottonwood (Populus trichocarpa) 23 9
5694 Black cottonwood (Populus trichocarpa) 29 11
5695 Bigleaf maple (Acer macrophyllum) 7 4
5696 Bigleaf maple (Acer macrophyllum) 17 7
5697 Black cottonwood (Populus trichocarpa) 20 8
5698 Bigleaf maple (Acer macrophyllum) 12 5
5699 Black cottonwood (Populus trichocarpa) 27 10
5700 Black cottonwood (Populus trichocarpa) 34 12
5701 Black cottonwood (Populus trichocarpa) 21 8
5702 Black cottonwood (Populus trichocarpa) 17 7
5703 Bigleaf maple (Acer macrophyllum) 16 7
5704 Black cottonwood (Populus trichocarpa) 31 11
Arborist Report - DRG Inc. Page 67 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5706 Bigleaf maple (Acer macrophyllum) 11 5
5707 Black cottonwood (Populus trichocarpa) 35 12
5708 Bigleaf maple (Acer macrophyllum) 6 4
5709 Bigleaf maple (Acer macrophyllum) 7 4
5710 Bigleaf maple (Acer macrophyllum) 7 4
5711 Bigleaf maple (Acer macrophyllum) 6 4
5712 Bigleaf maple (Acer macrophyllum) 9 4
5713 Black cottonwood (Populus trichocarpa) 22 9
5714 Bigleaf maple (Acer macrophyllum) 6 4
5715 Black cottonwood (Populus trichocarpa) 25 10
5716 Bigleaf maple (Acer macrophyllum) 6 4
5717 Black cottonwood (Populus trichocarpa) 24 9
5718 Black cottonwood (Populus trichocarpa) 33 12
5719 Bigleaf maple (Acer macrophyllum) 7 4
5721 Black cottonwood (Populus trichocarpa) 19 8
5722 Black cottonwood (Populus trichocarpa) 31 11
5723 Black cottonwood (Populus trichocarpa) 28 10
5724 Black cottonwood (Populus trichocarpa) 21 8
5725 Bigleaf maple (Acer macrophyllum) 6 4
5726 Black cottonwood (Populus trichocarpa) 18 7
5727 Black cottonwood (Populus trichocarpa) 33 12
5729 Black cottonwood (Populus trichocarpa) 10 5
5730 Black cottonwood (Populus trichocarpa) 14 6
5733 Black cottonwood (Populus trichocarpa) 13 6
5734 Bigleaf maple (Acer macrophyllum) 9 4
Arborist Report - DRG Inc. Page 68 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5735 Black cottonwood (Populus trichocarpa) 19 8
5737 Bigleaf maple (Acer macrophyllum) 6 4
5738 Black cottonwood (Populus trichocarpa) 18 7
5739 Black cottonwood (Populus trichocarpa) 24 9
5740 Black cottonwood (Populus trichocarpa) 13 6
5741 Bigleaf maple (Acer macrophyllum) 6 4
5743 Black cottonwood (Populus trichocarpa) 18 7
5744 Black cottonwood (Populus trichocarpa) 32 11
5745 Black cottonwood (Populus trichocarpa) 16 7
5746 Black cottonwood (Populus trichocarpa) 19 8
5747 Black cottonwood (Populus trichocarpa) 14 6
5748 Black cottonwood (Populus trichocarpa) 20 8
5749 Black cottonwood (Populus trichocarpa) 33 12
5750 Bigleaf maple (Acer macrophyllum) 19 8
5753 Black cottonwood (Populus trichocarpa) 24 9
5754 Western red cedar (Thuja plicata) 18 7
5755 Black cottonwood (Populus trichocarpa) 26 10
5756 Black cottonwood (Populus trichocarpa) 16 7
5757 Bigleaf maple (Acer macrophyllum) 14 6
5758 Bigleaf maple (Acer macrophyllum) 12 5
5759 Black cottonwood (Populus trichocarpa) 27 10
5760 Black cottonwood (Populus trichocarpa) 27 10
5761 Black cottonwood (Populus trichocarpa) 21 8
5763 Bigleaf maple (Acer macrophyllum) 13 6
5764 Black cottonwood (Populus trichocarpa) 38 13
Arborist Report - DRG Inc. Page 69 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5766 Black cottonwood (Populus trichocarpa) 36 12
5767 Black cottonwood (Populus trichocarpa) 39 13
5769 Oregon ash (Fraxinus latifolia) 7 4
5771 Bigleaf maple (Acer macrophyllum) 19 8
5772 Black cottonwood (Populus trichocarpa) 23 9
5773 Oregon ash (Fraxinus latifolia) 10 5
5774 Black cottonwood (Populus trichocarpa) 32 11
5775 Oregon ash (Fraxinus latifolia) 9 4
5776 Black cottonwood (Populus trichocarpa) 24 9
5777 Western red cedar (Thuja plicata) 7 4
5778 Bigleaf maple (Acer macrophyllum) 12 5
5779 Bigleaf maple (Acer macrophyllum) 6 4
5780 Bigleaf maple (Acer macrophyllum) 8 4
5783 Bigleaf maple (Acer macrophyllum) 18 7
5784 Western red cedar (Thuja plicata) 22 9
5785 Bigleaf maple (Acer macrophyllum) 14 6
5786 Bitter cherry (Prunus emarginata) 6 4
5787 Bigleaf maple (Acer macrophyllum) 9 4
5790 Bigleaf maple (Acer macrophyllum) 16 7
5791 Bigleaf maple (Acer macrophyllum) 19 8
5792 Oregon ash (Fraxinus latifolia) 23 9
5793 Bigleaf maple (Acer macrophyllum) 18 7
5794 Black cottonwood (Populus trichocarpa) 28 10
5795 Western red cedar (Thuja plicata) 12 5
5796 Bigleaf maple (Acer macrophyllum) 10 5
Arborist Report - DRG Inc. Page 70 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5797 Western red cedar (Thuja plicata) 7 4
5798 Red alder (Alnus rubra) 17 7
5799 Bigleaf maple (Acer macrophyllum) 20 8
5800 Bigleaf maple (Acer macrophyllum) 12 5
9960 Oregon ash (Fraxinus latifolia) 25 10
9962 Bigleaf maple (Acer macrophyllum) 29 11
9963
Lawson cypress (Chamaecyparis
lawsoniana) 16 7
9964
Lawson cypress (Chamaecyparis
lawsoniana) 11 5
9965 Bigleaf maple (Acer macrophyllum) 19 8
9966
Lawson cypress (Chamaecyparis
lawsoniana) 17 7
9967 Bigleaf maple (Acer macrophyllum) 15 6
9968 Oregon ash (Fraxinus latifolia) 19 8
9969 Western red cedar (Thuja plicata) 10 5
9970 Western red cedar (Thuja plicata) 26 10
9971 Bigleaf maple (Acer macrophyllum) 8 4
9972 Western red cedar (Thuja plicata) 20 8
9973 Oregon ash (Fraxinus latifolia) 12 5
9974 Oregon ash (Fraxinus latifolia) 11 5
9975 Black cottonwood (Populus trichocarpa) 70 13
9976 Black cottonwood (Populus trichocarpa) 46 13
9977 Bigleaf maple (Acer macrophyllum) 10 5
9978 Oregon ash (Fraxinus latifolia) 8 4
5801 Bigleaf maple (Acer macrophyllum) 11 5
Arborist Report - DRG Inc. Page 71 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
5803 Willow (Salix spp.) 7 4
5805 Black cottonwood (Populus trichocarpa) 45 13
5806 Bigleaf maple (Acer macrophyllum) 22 9
5807 Bigleaf maple (Acer macrophyllum) 20 8
5800 Oregon ash (Fraxinus latifolia) 19 8
5809 Bitter cherry (Prunus emarginata) 7 4
5810
Common hawthorn (Crataegus
monogyna) 10 5
5811
Common hawthorn (Crataegus
monogyna) 10 5
425 Scots pine (Pinus sylvestris) 12 5
426 Douglas fir (Pseudotsuga menziesii) 18 7
427 Douglas fir (Pseudotsuga menziesii) 15 6
428 Douglas fir (Pseudotsuga menziesii) 18 7
429 Douglas fir (Pseudotsuga menziesii) 19 8
432 Red alder (Alnus rubra) 6 4
433 Red alder (Alnus rubra) 6 4
434 Red alder (Alnus rubra) 6 4
435 Red alder (Alnus rubra) 6 4
436 Bigleaf maple (Acer macrophyllum) 7 4
438 Douglas fir (Pseudotsuga menziesii) 23 9
439 Douglas fir (Pseudotsuga menziesii) 20 8
440 Douglas fir (Pseudotsuga menziesii) 11 5
441 Douglas fir (Pseudotsuga menziesii) 22 9
442 Douglas fir (Pseudotsuga menziesii) 18 7
443 Douglas fir (Pseudotsuga menziesii) 15 6
Arborist Report - DRG Inc. Page 72 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
445 Douglas fir (Pseudotsuga menziesii) 13 6
446 Douglas fir (Pseudotsuga menziesii) 26 10
447 Douglas fir (Pseudotsuga menziesii) 12 5
448 Douglas fir (Pseudotsuga menziesii) 24 9
449 Douglas fir (Pseudotsuga menziesii) 9 4
450 Douglas fir (Pseudotsuga menziesii) 26 10
451 Douglas fir (Pseudotsuga menziesii) 13 6
452 Douglas fir (Pseudotsuga menziesii) 18 7
453 Douglas fir (Pseudotsuga menziesii) 19 8
454 Douglas fir (Pseudotsuga menziesii) 12 5
455 Douglas fir (Pseudotsuga menziesii) 18 7
456 Douglas fir (Pseudotsuga menziesii) 15 6
457 Douglas fir (Pseudotsuga menziesii) 20 8
460 Douglas fir (Pseudotsuga menziesii) 21 8
461 Douglas fir (Pseudotsuga menziesii) 12 5
462 Douglas fir (Pseudotsuga menziesii) 24 9
463 Douglas fir (Pseudotsuga menziesii) 25 10
464 Douglas fir (Pseudotsuga menziesii) 30 11
465 Douglas fir (Pseudotsuga menziesii) 25 10
466 Douglas fir (Pseudotsuga menziesii) 20 8
467 Douglas fir (Pseudotsuga menziesii) 19 8
468 Douglas fir (Pseudotsuga menziesii) 18 7
469 Douglas fir (Pseudotsuga menziesii) 22 9
470 Douglas fir (Pseudotsuga menziesii) 23 9
471 Grand fir (Abies grandis) 32 11
Arborist Report - DRG Inc. Page 73 of 73 July 2024 (Updated October 2025)
Tree ID# Species DSH (in) Tree Credits
475 Deodar cedar (Cedrus deodara) 32 11
476 Douglas fir (Pseudotsuga menziesii) 7 4
Total 2061