HomeMy WebLinkAboutP_CSWPPP_260611_v1
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
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Appendices
Appendix A. Temporary Erosion and Sediment Control Plan (Completed by others)
Appendix B. Construction Stormwater BMPs
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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.
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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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File No. 9186-184-00 Task 2032
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.
Puget Sound Energy | April 22, 2026 Page 11
File No. 9186-184-00 Task 2032
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)
Puget Sound Energy | April 22, 2026 Page 12
File No. 9186-184-00 Task 2032
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)
Puget Sound Energy | April 22, 2026 Page 13
File No. 9186-184-00 Task 2032
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.
Puget Sound Energy | April 22, 2026 Page 14
File No. 9186-184-00 Task 2032
■ 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.
Puget Sound Energy | April 22, 2026 Page 15
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
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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
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IN CONC MONUMENT IN CASE -0.6'
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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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04/19/202604/14/2026
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2023059071
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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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C0
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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
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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
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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
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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.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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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.
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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.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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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
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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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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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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.
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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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D-41
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.
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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.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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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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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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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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D-55
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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D-56
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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D-57
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-58
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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D-66
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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D-67
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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D-68
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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D-69
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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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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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
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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
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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.
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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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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