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HomeMy WebLinkAboutRS_Apron E _ TIR_190626_v1.pdf
Technical Information Report
for
Boeing Commercial Airplanes
Apron E Stalls and Paint Hangar
Prepared for:
Boeing Commercial Airplanes, Seattle District
P.O. Box 3707, M/S: 1W-10
Seattle, Washington 98124
Prepared by:
8410 154th Avenue NE, Suite 120 Redmond, WA 98052
Tele: (425) 869-2670 FAX: (425) 869-2679
60% Design Submittal
June 2019
This report has been prepared by the staff of DOWL under the direction of the undersigned
professional engineer whose stamp and signature appears hereon.
13726.16
Table of Contents
1.0 PROJECT OVERVIEW .................................................................................................................... 5
Figure 1: TIR Worksheet ......................................................................................................................................... 6
Figure 2: Vicinity Map .......................................................................................................................................... 11
Figure 3: Drainage Basin Map .............................................................................................................................. 12
Figure 4: Soils Mapping ........................................................................................................................................ 13
2.0 CONDITIONS & REQUIREMENTS SUMMARY ................................................................. 16
3.0 OFF-SITE ANALYSIS .................................................................................................................... 19
3.1 Define and Map the Study Area .................................................................................................................. 19
3.2 Review All Available Information On the Study Area .................................................................................. 19
3.3 Field Inspect the Study Area ....................................................................................................................... 19
3.4 Describe the Drainage System .................................................................................................................... 19
Figure 5: Downstream Flow Path to Lake Washington ......................................................................................... 20
Figure 6: Flood Map ............................................................................................................................................. 21
Figure 7: Critical Areas Map ................................................................................................................................. 22
4.0 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN ................................ 23
4.1 Existing Site Hydrology ............................................................................................................................... 23
4.2 Developed Site Hydrology .......................................................................................................................... 24
4.3 Flow Control ............................................................................................................................................... 24
4.4 On-Site Flow Control BMPS ........................................................................................................................ 24
4.5 Water Quality ............................................................................................................................................. 25
Figure 8: Existing Conditions ................................................................................................................................ 26
Figure 9: Proposed Conditions ............................................................................................................................. 27
5.0 CONVEYANCE SYSTEM ANALYSIS & DESIGN ......................................................................... 28
6.0 SPECIAL REPORTS & STUDIES .................................................................................................. 29
7.0 OTHER PERMITS ......................................................................................................................... 30
8.0 CWSPPP ANALYSIS AND DESIGN ............................................................................................. 31
8.1 Erosion and Sediment Control (ESC) Measures ........................................................................................... 31
8.1.1 Clearing Limits .......................................................................................................................................... 31
8.1.2 Cover Measures ........................................................................................................................................ 31
8.1.3 Perimeter Protection ................................................................................................................................ 31
8.1.4 Traffic Area Stabilization ........................................................................................................................... 31
8.1.5 Sediment Retention .................................................................................................................................. 31
8.1.6 Surface Water Collection .......................................................................................................................... 31
8.1.7 Dewatering Control .................................................................................................................................. 31
8.1.8 Dust Control .............................................................................................................................................. 32
8.1.9 Flow Control ............................................................................................................................................. 32
8.1.10 Control Pollutants ................................................................................................................................ 32
8.1.11 Protect Existing and Proposed Flow Control BMPS ............................................................................. 32
8.1.12 Maintain BMPs ..................................................................................................................................... 32
8.1.13 Manage the Project ............................................................................................................................. 32
8.2 SWPPS Measures ........................................................................................................................................ 32
8.2.1 Pollutant Handling and Disposal ............................................................................................................... 32
8.2.2 Cover and Containment for Materials, Fuel and Other Pollutants ........................................................... 33
8.2.3 Manage the Project Site ........................................................................................................................... 33
8.2.4 Protect from Spills and Drips .................................................................................................................... 33
8.2.5 Avoid Overapplication or Untimely Application of Chemicals and Fertilizers .......................................... 33
8.2.6 Prevent or Treat Contamination of Stormwater Runoff ........................................................................... 33
8.3 SWPPP Plan Design ..................................................................................................................................... 33
8.3.1 Element 1 – Preserve Vegetation / Mark Clearing Limits ......................................................................... 33
8.3.2 Element 2 – Establish Construction Access .............................................................................................. 34
8.3.3 Element 3 – Control Flow Rates ............................................................................................................... 34
8.3.4 Element 4 – Install Sediment Controls ..................................................................................................... 34
8.3.5 Element 5 – Stabilize Soils ........................................................................................................................ 34
8.3.6 Element 6 – Protect Slopes ....................................................................................................................... 34
8.3.7 Element 7 – Protect Drain Inlets ............................................................................................................... 34
8.3.8 Element 8 – Stabilize Channels and Outlets ............................................................................................. 34
8.3.9 Element 9 – Control Pollutants ................................................................................................................. 34
8.3.10 Element 10 – Control Dewatering ....................................................................................................... 35
8.3.11 Element 11 – Maintain BMPs............................................................................................................... 35
8.3.12 Element 12 – Manage the Project ....................................................................................................... 35
8.3.13 Element 13 – Protect Low Impact Development (LID)......................................................................... 35
9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .......... 36
9.1 Bond Quantities .......................................................................................................................................... 36
9.2 Flow Control and Water Quality Facility Summary Sheet and Sketch.......................................................... 36
9.3 Declaration of Covenant for Privately Maintained Flow Control and Water Quality Facilities .................... 36
10.0 OPERATIONS & MAINTENANCE MANUAL ............................................................................. 37
Appendix A CSWPPP Plans
Appendix B WWHM Report
Appendix C Water Quality Treatment Standard Detail
5
1.0 PROJECT OVERVIEW
This Technical Information Report is submitted to the City of Renton in support of the Apron E Expansion
Project on the existing parking lot proposed by Boeing. The project proposes to construct three airplane
stalls, a paint hangar, and a utility maintenance building on the existing parking lot.
The Apron E Expansion Project area is located at the intersection of Logan Ave N and N 6th St, adjacent
to the Apron D project site. The existing parking lot is situated between the Apron D project area and
Logan Ave N. The northern boundary of the lot is adjacent to N 6th St.
The project will use the 2017 Renton Surface Water Design Manual (RSWDM). The project is required to
undergo a Full Drainage Review in accordance with Figure 1.1.2.A of the RSWDM since it will be
removing or replacing over 2,000 square feet of impervious surface.
The project is located on the east side of the Cedar River, which flows north towards Lake Washington.
The project area will discharge directly into Lake Washington. For this project threshold discharge area
(TDA 1), flow control is not required since the proposed system connects into an existing system that is
considered to be exempt from flow control. The project will provide enhanced water quality treatment
by implementing MWS-Linear Modular Wetland structures upstream of the discharge point.
The projects consists of urban land per the USDA soil map.
Information Provided:
Figure 1: TIR Worksheet
Figure 2: Vicinity Map
Figure 3: Drainage Basin Map
Figure 4: Soils Mapping
6
Figure 1: TIR Worksheet
11
Figure 2: Vicinity Map
APRON E - STALLS PHASE 1 PROJECT
VICINITY MAP
WWW.DOWL.COM FIGURE 2
PROJECT
SITE
12
Figure 3: Drainage Basin Map
BOEING 737-MAX10BOEING 737-MAX101694 SF
ELECTRICAL ROOM
11A1
767 SF
COMPRESSOR ROOM
11A2
1522 SF
BOILER ROOM
11A3
1294 SF
INDUSTRIAL WASTE
TANK ROOM
11A4
GV
1
APRON E - STALLS PHASE 1
DRAINAGE BASIN MAP
WWW.DOWL.COM 1
FIGURE 3
13
Figure 4: Soils Mapping
16
2.0 CONDITIONS & REQUIREMENTS SUMMARY
Existing Conditions The Apron E Expansion project area is located at the intersection of Logan Ave N
and N 6th St, adjacent to the Apron D project site. The existing parking lot is situated between the Apron
D project area and Logan Ave N. The northern boundary of the lot is adjacent to N 6th St.
The existing project area is currently being uses as a parking lot with existing utilities in place. The
existing parking lot is a mix of old concrete and asphalt pavement along with existing lighting and
drainage structures.
The storm system currently discharges to the existing storm system located in Apron D just west of the
project site. The existing onsite storm system will be removed and replaced with the proposed storm
drain system that will collect and convey runoff from the new apron facilities. The new storm lines will
tie into the existing storm system. The existing system discharges to a storm drain interceptor pipe
system which runs north, parallel with the Cedar River and eventually discharges into Lake Washington.
The project site is gently sloped and surfaced primarily with concrete and asphalt pavement, with
minimal grass landscaping.
Site soils are classified as Urban Land, Ur. Figure 3 is a soil map from the USDA Web Soil Survey.
Full Drainage Review This project includes more than 2,000 square feet of new and replaced
impervious surface. Therefore, the project is subject to a full drainage review and must satisfy all 9 Core
Requirements and 6 Special Requirements of the RSWDM.
The following summary describes how this project will meet the “Core Requirements” and “Special
Requirements” that apply according to Section 1.2 in the RSWDM.
RSWDM Core Requirements
1. Core Requirement #1: Discharge at the Natural Location The project area will continue to
discharge into the existing storm system within Apron D but will modify the on-site storm
system in order to convey runoff to the discharge point. The project area can be considered to
be one TDA since all runoff from the site converges at a single discharge point.
2. Core Requirement #2: Off-Site Analysis See Section 3.0 for a detailed discussion on off-site
analysis. The project is required to provide a Level 1 downstream analysis as described in
Section 1.2.2.1 of the RSWDM.
3. Core Requirement #3: Flow Control See Section 4.0 for a detailed discussion on flow control
facilities for the project. The project is exempt from the flow control provisions since the
17
proposed storm system connects into an existing system that discharges into a flow control
exempt waterbody.
4. Core Requirement #4: Conveyance System Under this core requirement, new pipe systems
must be analyzed for capacity to contain and convey at minimum the 25-year peak flow. The
proposed drainage system will be sized to convey and contain the 25-year peak flow. See
Section 5.0 for a detailed discussion on conveyance.
5. Core Requirement #5: Erosion & Sediment Control Temporary erosion and sediment control
will be provided for the project. A Temporary Erosion and Sediment Control Plan (TESC) has
been prepared and included in the plan set. CSWPP is covered under Section 8.0 of this report.
6. Core Requirement #6: Maintenance and Operations See Section 10.0 of this report for a
detailed discussion on maintenance and operations. Ownership of the existing stormwater
system (Boeing Renton) will not change and the current maintenance program will remain in
place. The site is staffed 24-hours a day, there is a central monitoring system in place providing
for timely notification of problems.
7. Core Requirement #7: Financial Guarantees and Liability The project will comply with financial
guarantees as required by the City of Renton.
8. Core Requirement #8: Water Quality The project area is above the 5,000 square foot threshold
for providing water quality treatment. The project location is considered an industrial site.
Therefore, Enhanced Basic Water Quality is required per the latest King County Water Quality
Applications Map. The project will implement MWS-Linear Modular Wetland structures
upstream of the discharge point.
9. Core Requirement #9: On-Site BMPS The project is required to apply on-site flow control BMPs
to new impervious surfaces. See Section 4.0 for a detailed discussion regarding on-site flow
control BMPs.
City of Renton Special Requirements
1. Special Requirement #1: Other Adopted Area-Specific Requirements The site is not located
within an area having specific requirements above and beyond the core requirements.
2. Special Requirement #2: Flood Hazard Area Delineation The project site is not within the 100-
year floodplain. This project is located Zone X Other Flood Areas, 500-year floodplain per the
City of Renton (COR) mapping. See Figure 5.
3. Special Requirement #3: Flood Protection Facilities This project does not propose to rely on an
existing flood protection facility nor does it modify or construct a new flood protection facility.
18
4. Special Requirement #4: Source Control This project does warrant source controls. Fuel spill
control and containment will be provided for those areas that might hold a fueled or previously
fueled aircraft.
5. Special Requirement #5: Oil Control For a redevelopment project, where the threshold of new
plus replaced pollution generating impervious surfaces of 5,000 square feet is exceeded, runoff
treatment is required. The project will implement two Baffle Oil-Water Separator structures
upstream of the discharge point.
6. Special Requirement #6: Aquifer Protection Area The project is not located in an Aquifer
Protection Area Zone per City of Renton Groundwater Protection Areas (printed 11/12/2014)
provided in the City of Renton Surface Water Design Manual (SWDM) Special Requirements.
19
3.0 OFF-SITE ANALYSIS
Per RSWDM Section 1.2.2, this project must provide an off-site analysis report that assesses potential off-
site drainage and water quality impacts associated with the improvements to the project site. The project
requires a Level 1 downstream analysis as described in Section 1.2.2.1 of the RSWDM.
3.1 Define and Map the Study Area
The project site has a single discharge point to the west of the project site, which connects into the existing
storm system in Apron D. The project will maintain the existing discharge point. See Figure 4 for the
downstream flow path map.
3.2 Review All Available Information On the Study Area
City of Renton mapping and data were reviewed. There are no drainage complaints listed within ¼ mile of
the project site.
The Department of Ecology 303d listings were reviewed for Lake Washington. Some of the listings include
Bacteria and Total Phosphorus.
The USDA soils map identifies the on-site soils as Urban land.
3.3 Field Inspect the Study Area
The downstream flow path from the single discharge point was inspected using the City of Renton GIS
Map. No field inspections were completed for this project. There is no evidence of existing drainage and
water quality problems at the project site or downstream of the discharge points.
The project area discharges into the existing storm system in Apron D, just west of the project site. The
existing system conveys flow to a storm drain interceptor pipe system which runs north, parallel with the
Cedar River. The interceptor begins as a 24-inch diameter pipe which gradually upsizes to a 60-inch
diameter pipe as flow travels north. The pipe system discharges directly into Lake Washington.
3.4 Describe the Drainage System
There is no evidence of existing drainage and water quality problems at the project site or downstream
of the discharge points. The project will not implement any flow control facilities for the proposed
improvements. There are no predicted or anticipated drainage problems at the project site.
20
Figure 5: Downstream Flow Path to Lake Washington
Do w nstream An alysis M ap
1000 ft
N➤➤N
© 2018 Google
© 2018 Google
© 2018 Google
21
Figure 6: Flood Map
9,028 752
City of Renton Flood Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
6/18/2019
Legend
5120256
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet
Notes
512
WGS_1984_Web_Mercator_Auxiliary_Sphere
City and County Labels
City and County Boundary
Parcels
Floodway
Special Flood Hazard Areas (100
year flood)
Other Flood Areas (Zone X - 500
year flood)
Channel Migration Zones (CMZ) as
mapped by King County
Moderate Hazard Area
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
<all other values>
Type S Shoreline
Type F Fish
22
Figure 7: Critical Areas Map
9,028
752
City of Renton Critical Areas Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
5/22/2019
Legend
5120256
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet
Notes
512
WGS_1984_Web_Mercator_Auxiliary_Sphere
City and County Boundary
Parcels
Erosion Hazard - High
Floodway
Special Flood Hazard Areas (100
year flood)
Seismic Hazard Areas
Faults
Streets
Parks
Waterbodies
Map
Extent2010
23
4.0 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN
4.1 Existing Site Hydrology
The existing project area is currently being uses as a parking lot with existing utilities in place. The
existing parking lot is a mix of old concrete and asphalt pavement along with existing lighting and
drainage structures. The project site is gently sloped, with minimal grass landscaping on-site. See Figure
7 for an existing conditions map.
The project area can be considered to be one TDA since all runoff from the site converges at a single
discharge point. The storm system currently discharges to the existing storm system located in Apron D
just west of the project site. The existing system discharges to a storm drain interceptor pipe system
which runs north, parallel with the Cedar River and eventually discharges into Lake Washington.
The total area of the TDA is 10.13 acres. See Table 1 for the summary of areas in the existing conditions.
Table 1: Existing Site Area Summary
Existing Impervious Surface 9.13 Acres
Existing Pervious Surface 1.00 Acres
Total 10.13 Acres
24
4.2 Developed Site Hydrology
The Apron E Expansion project proposes to construct three airplane stalls, a paint hangar, and a utility
maintenance building on the existing parking lot. The project proposes to convey all stormwater facilities
to the existing storm system located in Apron D. The project will continue to discharge into the existing
storm system within Apron D but will modify the on-site storm system in order to convey runoff to the
discharge point.
In the developed condition, the project area is still one TDA since all stormwater runoff from the site
converges at a single discharge point. The proposed storm system will convey flow to the existing storm
system in Apron D, which connects to a storm drain interceptor pipe system that runs north, parallel with
the Cedar River and discharges into Lake Washington. Flow control facilities will not be implemented on-
site.
The project area in the developed condition will consist of primarily replaced impervious surfaces, along
with new impervious and landscape areas. See Table 2 for the summary of areas in the developed
condition.
Table 2: Developed Site Area Summary
New Impervious Surface 0.70 Acres
Replaced Impervious Surface 8.54 Acres
New Pervious Surface 0.89 Acres
Total 10.13 Acres
4.3 Flow Control
The project area is currently tributary to the existing storm system in Apron D. The project will continue
to discharge into the existing storm system within Apron D but will modify the on-site storm system in
order to convey runoff to the discharge point. The existing storm system directly discharges into Lake
Washington, which is considered a flow control exempt waterbody. Since the project will connect into an
existing system that discharges out to Lake Washington, the proposed project area shall be exempt from
flow control. Flow control facilities will not be implemented on-site.
In addition to connecting into an existing flow control exempt system, the project threshold discharge
area (TDA) does not generate more than a 0.15 cfs increase in the developed condition when modeled
using 15 minute time steps in WWHM. The 100-year peak flow rates for the predeveloped and developed
condition are 7.31 and 7.37 cfs, respectively, which results in a difference of 0.06 cfs. According to Section
1.2.3 of the RSWDM, the project area is exempt form flow control requirements since the proposed
development only results in an increase of 0.06 cfs. See Appendix B for the report generated in WWHM.
4.4 On-Site Flow Control BMPS
Per Core Requirement #9 of the RSWDM, the project is required to apply on-site flow control BMPs. On-
site flow control BMPs will not be feasible within the project area due to the lack of pervious surfaces and
25
sufficient space on-site. The implementation of on-site flow control BMPs would not be practical since the
project area is located within an airport, where the majority of the site consists of impervious land cover.
4.5 Water Quality
Since the project area will be adding more than 5,000 square feet of new impervious surface, the project
is required to provide water quality treatment on-site. The project will implement MWS-Linear Modular
Wetland structures upstream of the discharge point for two separate storm drain lines. The project site is
divided into the North and South drainage basins. See Figure 3 for the Drainage Basin map. The North
drainage basin consists of 3.43 acres of impervious surface and generates an off-line water quality flow
rate of 0.3148 cfs. The South drainage basin consists of 4.33 acres of impervious surface and generates an
off-line water quality flow rate of 0.3975 cfs. The South drainage basin will collect half of the proposed
building’s roof runoff and route it to the water quality treatment structure. The other half o f the roof
runoff will be bypassing the water quality treatment structure and routed directly to the discharge point.
The WWHM reports for the water quality flow rates for each basin can be found in Appendix B. See
Appendix C for the MWS-Linear Modular Wetland standard detail.
26
Figure 8: Existing Conditions
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C224R C15
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C225R C16
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C226R C17
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C227R C18
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C228R C19
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
RENTON SITE
PAVEMENT REMOVAL AND TESC PLAN
C229R C20
60% DESIGN REVIEW
NOT FOR CONSTRUCTION
REMOVAL
27
Figure 9: Proposed Conditions
RENTON SITE
SITE PLAN
C3 C1
GALVANIZATION NOTE LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
GV Inlet
Outlet
CONTROL POINT TABLE
RENTON SITE
SITE PLAN
C4 C2
GALVANIZATION NOTE LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
CONTROL POINT TABLE
LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
RENTON SITE
SITE PLAN
C5 C3
GALVANIZATION NOTE
28
5.0 CONVEYANCE SYSTEM ANALYSIS & DESIGN
In accordance with the RSWDM, pipe capacities for conveyance systems will be analyzed by applying the
25-year peak flow rate. A conveyance system capacity analysis will be provided with the 90% plans.
29
6.0 SPECIAL REPORTS & STUDIES
• Stormwater Pollution Prevention Plan (SWPPP) (Appendix A)
30
7.0 OTHER PERMITS
The following permits are anticipated for this project:
• SEPA Permit
• Civil Construction Permit
• Building Permit
31
8.0 CWSPPP ANALYSIS AND DESIGN
8.1 Erosion and Sediment Control (ESC) Measures
8.1.1 Clearing Limits
Prior to beginning earth disturbing activities on the site, the Contractor shall delineate the clearing limits
which will be spray painted with white paint on the edge of the existing concrete panels to be removed.
During the construction period, no disturbance beyond the marked clearing limits shall be permitted. The
marking shall be maintained by the Contractor for the duration of construction.
8.1.2 Cover Measures
The existing asphalt and concrete will remain in place as long as possible. Any exposed disturbed soil will
need to be stabilized at the end of each shift. Plastic covering is the most practical means of accomplishing
this.
8.1.3 Perimeter Protection
The perimeter will have a temporary safety fence. In the perimeter areas on the downhill side a triangular
silt dike is to be installed. This triangular silt dike works similar to a silt fence but can easily be installed
on existing pavement. The filter fabric traps the sediment so that it can be removed after reaching a depth
of four inches.
8.1.4 Traffic Area Stabilization
Currently this access is paved, and will be used as existing pavement as long as possible. Once the asphalt
is removed, a construction entrance will be installed. If the construction entrance is not providing enough
protection then a wheel wash will be installed.
8.1.5 Sediment Retention
It is not anticipated that the site will generate significant quantities of sediment laden runoff. The project
will utilize storm drain inlet protection and localized TESC measures to prevent sediment laden water
leaving the site. Triangular silt dike will also be installed adjacent to all disturbed areas to minimize the
transport of sediment.
8.1.6 Surface Water Collection
Surface water will be collected by the proposed storm system. Catch basins and clean outs will be used to
collect and convey stormwater runoff. The construction area will discharge into the existing storm system
located in Apron D, directly west of the project site.
8.1.7 Dewatering Control
Based on groundwater elevations, dewatering is not anticipated at the site.
32
8.1.8 Dust Control
If dust becomes a problem, then the area shall be sprayed with water until wet, but no runoff shall be
generated by spraying.
8.1.9 Flow Control
Flow control will not be provided for this project on-site.
8.1.10 Control Pollutants
The following measures will be taken:
• All vehicles, equipment and petroleum product storage/dispensing areas will be inspected
regularly to detect any leaks or spills, and to identify maintenance.
• Fueling will be conducted on hard pavement.
• Spill prevention measures, such as drip pans, will be used when conducting maintenance and
repair of vehicles or equipment.
• In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if
raining, over the vehicle.
• Contaminated surfaces shall be cleaned immediately following any discharge or spill incident.
• Process water and slurry resulting from concrete work will be prevented from entering waters of
the state by implementing Concrete Handling measures (BMP C151), pH neutralization will be
utilized if necessary.
8.1.11 Protect Existing and Proposed Flow Control BMPS
Protection measures shall be installed to prevent impacts to existing and proposed flow control BMPs.
Triangular silt dike and storm drain inlet protection shall be used to protect existing and proposed flow
control BMPs.
8.1.12 Maintain BMPs
The Contractor shall be responsible for maintaining and repairing all temporary and permanent erosion
and sediment control BMPs throughout construction. All temporary erosion and sediment control BMPs
shall be removed prior to final construction approval, or within 30 days after achieving final site
stabilization.
8.1.13 Manage the Project
Construction will take place during the dry season. All BMPs shall be inspected, maintained and repaired
as needed throughout all phases of construction. Site inspections and monitoring shall be documented.
The contractor shall update the SWPPP as necessary and keep a copy on site at all times.
8.2 SWPPS Measures
8.2.1 Pollutant Handling and Disposal
The following measures will be taken:
33
• All vehicles, equipment and petroleum product storage/dispensing areas will be inspected
regularly to detect any leaks or spills, and to identify maintenance.
• Fueling will be conducted on hard pavement.
• Spill prevention measures, such as drip pans, will be used when conducting maintenance and
repair of vehicles or equipment.
• In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if
raining, over the vehicle.
• Contaminated surfaces shall be cleaned immediately following any discharge or spill incident.
• Process water and slurry resulting from concrete work will be prevented from entering waters of
the state by implementing Concrete Handling measures (BMP C151), pH neutralization will be
utilized if necessary.
8.2.2 Cover and Containment for Materials, Fuel and Other Pollutants
Temporary storage areas shall be located away from vehicular traffic, near the construction entrances,
and away from waterways or storm drains. The storage and handling of hazardous materials shall be
minimized whenever possible. Construction materials shall be covered in wet weather.
8.2.3 Manage the Project Site
See Section 8.1.13 for managing the project.
8.2.4 Protect from Spills and Drips
The BMPs listed in Section 8.2.1 and 8.2.2 shall be used to protect from spills and drips.
8.2.5 Avoid Overapplication or Untimely Application of Chemicals and Fertilizers
Chemicals and fertilizers shall be prohibited for this project.
8.2.6 Prevent or Treat Contamination of Stormwater Runoff
All BMPs listed in Section 8.1 and 8.2 shall be used to prevent contamination of stormwater runoff.
8.3 SWPPP Plan Design
The Stormwater Pollution Prevention Plan (SWPPP) is a stand-alone document that describes the
Construction Best Management Practices (BMP’s). The SWPPP has been prepared under a separate cover,
but is attached in Appendix A of this report. The 13 elements and BMPs recommended are identified
below:
8.3.1 Element 1 – Preserve Vegetation / Mark Clearing Limits
Prior to beginning earth disturbing activities on the site, the Contractor shall delineate the clearing limits
which will be spray painted with white paint on the edge of the existing concrete panels to be removed.
During the construction period, no disturbance beyond the marked clearing limits shall be permitted. The
marking shall be maintained by the Contractor for the duration of construction.
34
8.3.2 Element 2 – Establish Construction Access
The site is currently paved and the asphalt will remain in place as long as possible. Once the driveway
asphalt is removed a construction entrance per the City of Renton standard detail 215.10 could be
employed. Sequentially a construction entrance might not be necessary. Wheel washing, street sweeping
and street cleaning shall be employed as necessary to prevent sediment from tracking onto the Perimeter
Road.
8.3.3 Element 3 – Control Flow Rates
Flow control will not be provided for this project on-site.
8.3.4 Element 4 – Install Sediment Controls
It is not anticipated that the site will generate significant quantities of sediment laden runoff. The project
will utilize storm drain inlet protection and localized TESC measures to prevent sediment laden water
leaving the site. Triangular silt dike will also be installed adjacent to all disturbed areas to minimize the
transport of sediment.
8.3.5 Element 5 – Stabilize Soils
The existing asphalt and concrete will remain in place as long as possible. Exposed and unworked soils
shall be stabilized with Plastic Coverings per City of Renton standard detail 213.30 or an equivalent
protection.
8.3.6 Element 6 – Protect Slopes
The site is relatively flat, where there are no slopes.
8.3.7 Element 7 – Protect Drain Inlets
Storm drain inlet protection will be installed per City of Renton standard detail 216.30 on all catch basins
located within the construction area and immediately downstream of the project areas.
8.3.8 Element 8 – Stabilize Channels and Outlets
The stormwater runoff will be directly released into the existing storm system in Apron D, just west of the
project area.
8.3.9 Element 9 – Control Pollutants
The following measures will be taken:
• All vehicles, equipment and petroleum product storage/dispensing areas will be inspected
regularly to detect any leaks or spills, and to identify maintenance.
• Fueling will be conducted on hard pavement.
• Spill prevention measures, such as drip pans, will be used when conducting maintenance and
repair of vehicles or equipment.
• In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if
raining, over the vehicle.
35
• Contaminated surfaces shall be cleaned immediately following any discharge or spill incident.
• Process water and slurry resulting from concrete work will be prevented from entering waters of
the state by implementing Concrete Handling measures, pH neutralization will be utilized if
necessary.
8.3.10 Element 10 – Control Dewatering
Based on groundwater elevations, dewatering is not anticipated at the site.
8.3.11 Element 11 – Maintain BMPs
All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be inspected, maintained
and repaired as needed to ensure continued performance of their intended function.
8.3.12 Element 12 – Manage the Project
During construction consideration shall be given to removing and replacing the pavement in stages. Site
inspections and monitoring will be conducted in accordance with Special Conditions S4 of the CSWGP.
The contractor will update the SWPPP as necessary and keep a copy on site at all times.
8.3.13 Element 13 – Protect Low Impact Development (LID)
There are no LID BMPs proposed for this project. If it becomes necessary, the BMPs listed in Elements 1-
12 shall be used to protect LID BMPs.
36
9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT
9.1 Bond Quantities
A bond quantities worksheet will be prepared for the 90% submittal.
9.2 Flow Control and Water Quality Facility Summary Sheet and Sketch
A bond quantities worksheet will be prepared for the 90% submittal.
9.3 Declaration of Covenant for Privately Maintained Flow Control and Water Quality
Facilities
A bond quantities worksheet will be prepared for the 90% submittal.
10.0 OPERATIONS & MAINTENANCE MANUAL
The Operations and Maintenance Manual will be developed in the future submittal.
Appendix A
CSWPPP Plans
Construction Stormwater General Permit
Stormwater Pollution Prevention Plan
(SWPPP)
for
Apron E Stalls and Paint Hangar
Prepared for: Prepared for:
The Washington State Department of Ecology City of Renton, WA
Northwest Regional Office
3190 – 160th Avenue SE
Bellevue, WA 98008
Permittee / Owner Developer Operator / Contractor
Boeing Commercial Airplanes TBD TBD
Project Site Location
Renton Municipal Airport
City of Renton, WA
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Jason Shrope DOWL 425-869-2670
SWPPP Preparation Date
June / 12 / 2019
Project Construction Dates
Activity / Phase Start Date End Date
TBD TBD TBD
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Table of Contents
1 Project Information .............................................................................................................. 4
1.1 Existing Conditions ...................................................................................................... 4
1.2 Proposed Construction Activities .................................................................................. 4
2 Construction Stormwater Best Management Practices (BMPs) ........................................... 6
2.1 The 13 Elements .......................................................................................................... 6
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................ 6
2.1.2 Element 2: Establish Construction Access ............................................................ 7
2.1.3 Element 3: Control Flow Rates ............................................................................. 8
2.1.4 Element 4: Install Sediment Controls .................................................................... 9
2.1.5 Element 5: Stabilize Soils ....................................................................................10
2.1.6 Element 6: Protect Slopes....................................................................................11
2.1.7 Element 7: Protect Drain Inlets ............................................................................12
2.1.8 Element 8: Stabilize Channels and Outlets ..........................................................13
2.1.9 Element 9: Control Pollutants ...............................................................................14
2.1.10 Element 10: Control Dewatering ..........................................................................16
2.1.11 Element 11: Maintain BMPs .................................................................................17
2.1.12 Element 12: Manage the Project ..........................................................................18
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .................................21
3 Pollution Prevention Team .................................................................................................22
4 Monitoring and Sampling Requirements ............................................................................23
4.1 Site Inspection ............................................................................................................23
4.2 Stormwater Quality Sampling ......................................................................................23
4.2.1 Turbidity Sampling ...............................................................................................23
4.2.2 pH Sampling ........................................................................................................25
5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .........................26
5.1 303(d) Listed Waterbodies ..........................................................................................26
5.2 TMDL Waterbodies .....................................................................................................26
6 Reporting and Record Keeping ..........................................................................................27
6.1 Record Keeping ..........................................................................................................27
6.1.1 Site Log Book ......................................................................................................27
6.1.2 Records Retention ...............................................................................................27
6.1.3 Updating the SWPPP ...........................................................................................27
6.2 Reporting ....................................................................................................................28
6.2.1 Discharge Monitoring Reports ..............................................................................28
6.2.2 Notification of Noncompliance ..............................................................................28
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List of Tables
Table 1 – Summary of Site Pollutant Constituents ................................................................. 4
Table 2 – Pollutants ................................................................................................................ 14
Table 3 – pH-Modifying Sources ............................................................................................ 15
Table 4 – Dewatering BMPs .................................................................................................... 16
Table 5 – Management ............................................................................................................ 18
Table 6 – BMP Implementation Schedule .............................................................................. 19
Table 7 – Team Information .................................................................................................... 22
Table 8 – Turbidity Sampling Method .................................................................................... 23
Table 9 – pH Sampling Method .............................................................................................. 25
List of Appendices
A. Site Map
B. BMP Detail
C. Correspondence
D. Site Inspection Form
E. Construction Stormwater General Permit (CSWGP)
F. 303(d) List Waterbodies / TMDL Waterbodies Information
G. Contaminated Site Information
H. Engineering Calculations
P a g e | 3
List of Acronyms and Abbreviations
Acronym / Abbreviation Explanation
303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies
BFO Bellingham Field Office of the Department of Ecology
BMP(s) Best Management Practice(s)
CESCL Certified Erosion and Sediment Control Lead
CO2 Carbon Dioxide
CRO Central Regional Office of the Department of Ecology
CSWGP Construction Stormwater General Permit
CWA Clean Water Act
DMR Discharge Monitoring Report
DO Dissolved Oxygen
Ecology Washington State Department of Ecology
EPA United States Environmental Protection Agency
ERO Eastern Regional Office of the Department of Ecology
ERTS Environmental Report Tracking System
ESC Erosion and Sediment Control
GULD General Use Level Designation
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Units
NWRO Northwest Regional Office of the Department of Ecology
pH Power of Hydrogen
RCW Revised Code of Washington
SPCC Spill Prevention, Control, and Countermeasure
su Standard Units
SWMMEW Stormwater Management Manual for Eastern Washington
SWMMWW Stormwater Management Manual for Western Washington
SWPPP Stormwater Pollution Prevention Plan
TESC Temporary Erosion and Sediment Control
SWRO Southwest Regional Office of the Department of Ecology
TMDL Total Maximum Daily Load
VFO Vancouver Field Office of the Department of Ecology
WAC Washington Administrative Code
WSDOT Washington Department of Transportation
WWHM Western Washington Hydrology Model
P a g e | 4
1 Project Information
Project/Site Name: Apron E Expansion Project
Street/Location: Intersection of Logan Ave N / N 6th St
City: Renton State: WA Zip code: 98057
Subdivision: N/A
Receiving waterbody: Lake Washington
1.1 Existing Conditions
Total acreage (including support activities such as off-site equipment staging yards, material
storage areas, borrow areas).
Total acreage: 10.45 Acres
Disturbed acreage: 10.45 Acres
Existing structures: Boeing S1 Parking Lot
Landscape
topography:
Flat
Drainage patterns: Parking lot runoff is collected with an existing stormdrain system and
conveyed west into the existing storm system on Apron D.
Existing Vegetation: Landscaped area throughout and around the perimeter of the existing
parking lot.
Critical Areas (wetlands, streams, high erosion
risk, steep or difficult to stabilize slopes):
Seizmic hazard areas.
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the
receiving waterbody: Lake Washington is 303(d) listed for Bacteria and Total Phosphorus.
Table 1 includes a list of suspected and/or known contaminants associated with the construction
activity.
Table 1 – Summary of Site Pollutant Constituents
Constituent
(Pollutant) Location Depth Concentration
None
1.2 Proposed Construction Activities
Description of site development (example: subdivision):
P a g e | 5
This project proposes to construct three airplane stalls, a paint hangar, and a utility maintenance
building on the existing Boeing S1 parking lot. The project porposes to connect to the existing
storm system on Apron D, just west of the project site. Construction will impact approximately
10.45 acres.
Description of construction activities (example: site preparation, demolition, excavation):
The project will include the construction of the following elements:
• Clearing and grubbing
• Demolition and excavation
• Utilities – storm, sewer and water
• Impervious surface replacement
• Storm drain conveyance connection to existing storm system
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
All stormwater is collected on-site via the proposed storm drain system and conveyed west until
it discharges to the existing downstream conveyance system on Apron D. There is no
contributing flow from or onto adjacent properties.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
The site will be stabilized with pavement and landscaping.
Contaminated Site Information:
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
There are no proposed activities regarding contaminated soils or groundwater.
P a g e | 6
2 Construction Stormwater Best Management Practices (BMPs)
The SWPPP is a living document reflecting current conditions and changes throughout the life
of the project. These changes may be informal (i.e., hand-written notes and deletions). Update
the SWPPP when the CESCL or local agency has noted a deficiency in BMPs or deviation from
original design.
2.1 The 13 Elements
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed to construction, the limits
of construction will be clearly marked before land-disturbing activities begin. Trees that are to
be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated in the
field. In general, natural vegetation and native topsoil shall be retained in an undisturbed state
to the maximum extent possible.
A protective barrier shall be placed aound the protected trees prior to land preparation or
construction activities, and shall remain in place until all construction activity is terminated. No
equipment, chemicals, soil deposits or construction materials shall be placed within the
protective barriers. Any landscaping activities subsequent to the removal of the barriers shall be
accomplished with light machinery or hand labor. (LMC 17.15.160 B1)
Prior to beginning earth disturbing activities on the site, the Contractor shall delineate the
clearing limits which will be spray painted with white paint on the edge of the existing concrete
panels to be removed. During the construction period, no disturbance beyond the marked
clearing limits shall be permitted. The marking shall be maintained by the Contractor for the
duration of construction.
List and describe BMPs:
• Plastic or Metal Fence (BMP D.2.1.1.1) (if necessary)
Installation Schedules: Prior to beginning construction activities
Inspection and Maintenance plan: Weekly observation
Responsible Staff: Contractor
P a g e | 7
2.1.2 Element 2: Establish Construction Access
Construction access or activities occurring on unpaved areas shall be minimized, yet where
necessary, access points shall be stabilized to minimize the tracking of sediment onto public
roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent
sediment from entering state waters. All wash wastewater shall be controlled on site.
Currently this access is paved, and will be used as existing pavement as long as possible. Once
the asphalt is removed, a construction entrance will be installed. If the construction entrance is
not providing enough protection then a wheel wash will be installed.
List and describe BMPs:
• Stabilized Construction Entrance (BMP D.2.1.4.1) (if necessary)
• Construction Road/Parking Area Stabilization (BMP D.2.1.4.2)
• Wheel Wash (BMP D.2.1.4.3) (if necessary)
Installation Schedules: These will be implemented for the duration of construction
Inspection and Maintenance plan: As necessary
Responsible Staff: Contractor
P a g e | 8
2.1.3 Element 3: Control Flow Rates
In order to protect the properties and waterways downstream of the project site, stormwater
discharges from the site will be controlled. There are no specific BMPs for flow control that shall
be used on this project.
The project site is located west of the Cascade Mountain Crest. As such, the project must
comply with Core Requirement 3.
In general, discharge rates of stormwater from the site will be controlled where increases in
impervious area or soil compaction during construction could lead to downstream erosion, or
where necessary to meet local agency stormwater discharge requirements (e.g. discharge to
combined sewer systems).
Flow control will not be provided for this project on-site since the project area is designated as
being exempt from flow control requirements.
Will you construct stormwater retention and/or detention facilities?
Yes No
Will you use permanent infiltration ponds or other low impact development (example: rain
gardens, bio-retention, porous pavement) to control flow during construction?
Yes No
List and describe BMPs: N/A
Installation Schedules: N/A
Inspection and Maintenance plan: N/A
Responsible Staff: N/A
P a g e | 9
2.1.4 Element 4: Install Sediment Controls
All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal
BMP before leaving the construction site or prior to being discharged to an infiltration facility.
The specific BMPs to be used for controlling sediment on this project include:
• Triangular Silt Dike (BMP D.2.1.3.4)
• Storm Drain Inlet Protection (BMP D.2.1.5.3)
To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will
promptly initiate the implementation of one or more of the alternative BMPs after the first sign
that existing BMPs are ineffective or failing.
In addition, sediment will be removed from paved areas in and adjacent to construction work
areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on
vehicle tires away from the site and to minimize washoff of sediments from adjacent streets in
runoff.
Whenever possible, sediment laden water shall be discharged into onsite, relatively level,
vegetated areas.
Installation Schedules: Prior to beginning construction activities
Inspection and Maintenance plan: Weekly inspection and after storm events
Responsible Staff: Contractor
P a g e | 10
2.1.5 Element 5: Stabilize Soils
Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent
erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be
used on this project include:
• Plastic Covering (BMP D.2.1.2.4)
• Dust Control (BMP D.2.1.8)
The project site is located west of the Cascade Mountain Crest. As such, no soils shall 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 shall be stabilized at the end of the shift before a holiday or weekend if needed based on
weather forecasts.
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be
temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion,
protected with sediment trapping measures, and where possible, be located away from storm
drain inlets, waterways, and drainage channels.
West of the Cascade Mountains Crest
Season Dates Number of Days Soils Can
be Left Exposed
During the Dry Season May 1 – September 30 7 days
During the Wet Season October 1 – April 30 2 days
Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on
the weather forecast.
Anticipated project dates: Start date: TBD End date: TBD
Will you construct during the wet season?
Yes No
Installation Schedules: Implemented as soil is exposed
Inspection and Maintenance plan: Daily
Responsible Staff: Contractor
P a g e | 11
2.1.6 Element 6: Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes
erosion. The project site is relatively flat, where there are no slopes. It is not antipicated to
require the protection of slopes, but the following specific BMPs will be used to protect slopes
for this project as necessary:
• Temporary and Permanent Seeding (BMP D.2.1.2.6) (if necessary)
Will steep slopes be present at the site during construction?
Yes No
Installation Schedules: As necessary – no impacted slopes on-site
Inspection and Maintenance plan: As necessary
Responsible Staff: Contractor
P a g e | 12
2.1.7 Element 7: Protect Drain Inlets
All storm drain inlets and culverts made operable during construction shall be protected to
prevent unfiltered or untreated water from entering the drainage conveyance system. However,
the first priority is to keep all access roads clean of sediment and keep street wash water
separate from entering storm drains until treatment can be provided. Storm Drain Inlet
Protection (BMP D.2.1.5.3) will be implemented for all drainage inlets and culverts that could
potentially be impacted by sediment-laden runoff on and near the project site.
If the BMP option listed above are deemed ineffective or inappropriate during construction to
satisfy the requirements set forth in the General NPDES Permit, the Certified Erosion and
Sediment Control Lead shall implement one or more of the alternative BMP inlet protection
options.
Installation Schedules: Prior to beginning construction activities
Inspection and Maintenance plan: Weekly inspection and after storm events
Responsible Staff: Contractor
P a g e | 13
2.1.8 Element 8: Stabilize Channels and Outlets
Where site runoff is to be conveyed in channels, or discharged to a stream or some other
natural drainage point, efforts will be taken to prevent downstream erosion. The specific BMPs
for channel and outlet stabilization that shall be used on this project include:
• N/A – no channels or outlets on-site or included in project
The project site is located west of the Cascade Mountain Crest. As such, all temporary on-site
conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the
expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval
storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate indicated by
an approved continuous runoff simulation model, increased by a factor of 1.6, shall be used.
Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent
streambanks, slopes, and downstream reaches shall be provided at the outlets of all
conveyance systems.
Provide stabilization, including armoring material, adequate to prevent erosion of outlets,
adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all
conveyance systems.
Installation Schedules: N/A
Inspection and Maintenance plan:N/A
Responsible Staff: N/A
P a g e | 14
2.1.9 Element 9: Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be
handled and disposed of in a manner that does not cause contamination of stormwater. Good
housekeeping and preventative measures will be taken to ensure that the site will be kept clean,
well organized, and free of debris. If required, BMPs to be implemented to control specific
sources of pollutants are discussed below.
Vehicles, construction equipment, and/or petroleum product storage/dispensing:
▪ All vehicles, equipment, and petroleum product storage/dispensing areas will be
inspected regularly to detect any leaks or spills, and to identify maintenance
needs to prevent leaks or spills.
▪ Fueling will be conducted on hard pavement.
▪ Spill prevention measures, such as drip pans, will be used when conducting
maintenance and repair of vehicles or equipment.
▪ In order to perform emergency repairs on site, temporary plastic will be placed
beneath and, if raining, over the vehicle.
▪ Contaminated surfaces shall be cleaned immediately following any discharge or
spill incident.
▪ Process water and slurry resulting from concrete work will be prevented from
entering water of the state by implementing Concrete Handling measures, pH
neutralization will be utilized if necessary.
If applicable, the Contractor shall prepare an SPCC Plan according to the Washington State
Department of Transportation (WSDOT) Requirements (see the WSDOT Standard
Specifications for Road, Bridge, and Municipal Construction 2018).
The following pollutants are anticipated to be present on-site:
Table 2 – Pollutants
Pollutant (List pollutants and source, if applicable)
Gasoline – Fuel for vehicles
Hydraulic Oil – Operator’s equipment
Installation Schedules: Implemented for the duration of construction
Inspection and Maintenance plan: Weekly inspection
Responsible Staff: Contractor
Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site?
Yes No
P a g e | 15
Will wheel wash or tire bath system BMPs be used during construction?
Yes No
Will pH-modifying sources be present on-site?
Yes No
Table 3 – pH-Modifying Sources
None
Bulk cement
Cement kiln dust
Fly ash
Other cementitious materials
New concrete washing or curing waters
Waste streams generated from concrete grinding and sawing
Exposed aggregate processes
Dewatering concrete vaults
Concrete pumping and mixer washout waters
Recycled concrete
Recycled concrete stockpiles
Other (i.e., calcium lignosulfate) [please describe: ]
Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches,
streets, or streams. Excess concrete must not be dumped on-site, except in designated
concrete washout areas with appropriate BMPs installed. Excess concrete must be returned to
the plant for recycling if there are no concrete washout areas with appropriate BMPs installed.
Will uncontaminated water from water-only based shaft drilling for construction of building, road,
and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits
discharge to surface waters?
Yes No
P a g e | 16
2.1.10 Element 10: Control Dewatering
All dewatering water from open cut excavation, tunneling, foundation work, trench, or
underground vaults shall be discharged into a controlled conveyance system prior to discharge
to a sediment trap or sediment pond. Channels will be stabilized, per Element #8. Clean, non-
turbid dewatering water will not be routed through stormwater sediment ponds, and will be
discharged to systems tributary to the receiving waters of the State in a manner that does not
cause erosion, flooding, or a violation of State water quality standards in the receiving water.
Highly turbid dewatering water from soils known or suspected to be contaminated, or from use
of construction equipment, will require additional monitoring and treatment as required for the
specific pollutants based on the receiving waters into which the discharge is occurring. Such
monitoring is the responsibility of the contractor.
However, the dewatering of soils known to be free of contamination will trigger BMPs to trap
sediment and reduce turbidity. At a minimum, geotextile fabric socks/bags/cells will be used to
filter this material.
To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will
promptly initiate the implementation of one or more of the alternative BMPs after the first sign
that existing BMPs are ineffective or failing.
Table 4 – Dewatering BMPs
Infiltration
Transport off-site in a vehicle (vacuum truck for legal disposal)
Ecology-approved on-site chemical treatment or other suitable treatment technologies
Sanitary or combined sewer discharge with local sewer district approval (last resort)
Use of sedimentation bag with discharge to ditch or swale (small volumes of localized
dewatering)
Installation Schedules: As necessary – dewatering is not anticipated
Inspection and Maintenance plan: As necessary
Responsible Staff: Contractor
P a g e | 17
2.1.11 Element 11: Maintain BMPs
All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained
and repaired as needed to ensure continued performance of their intended function.
Maintenance and repair shall be conducted in accordance with each particular BMP
specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW).
Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar
week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the
site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to
once every calendar month.
All temporary ESC BMPs shall be removed within 30 days after final site stabilization is
achieved or after the temporary BMPs are no longer needed.
Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal
of either BMPs or vegetation shall be permanently stabilized.
Additionally, protection must be provided for all BMPs installed for the permanent control of
stormwater from sediment and compaction. BMPs that are to remain in place following
completion of construction shall be examined and restored to full operating condition. If
sediment enters these BMPs during construction, the sediment shall be removed and the facility
shall be returned to conditions specified in the construction documents.
P a g e | 18
2.1.12 Element 12: Manage the Project
The project will be managed based on the following principles:
• Projects will be phased to the maximum extent practicable and seasonal work limitations
will be taken into account.
• Inspection and monitoring:
o Inspection, maintenance and repair of all BMPs will occur as needed to ensure
performance of their intended function.
o Site inspections and monitoring will be conducted in accordance with Special
Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map.
Sampling station(s) are located in accordance with applicable requirements of
the CSWGP.
• Maintain an updated SWPPP.
o The SWPPP will be updated, maintained, and implemented in accordance with
Special Conditions S3, S4, and S9 of the CSWGP.
As site work progresses the SWPPP will be modified routinely to reflect changing site
conditions. The SWPPP will be reviewed monthly to ensure the content is current.
Table 5 – Management
Design the project to fit the existing topography, soils, and drainage patterns
Emphasize erosion control rather than sediment control
Minimize the extent and duration of the area exposed
Keep runoff velocities low
Retain sediment on-site
Thoroughly monitor site and maintain all ESC measures
Schedule major earthwork during the dry season
Other (please describe)
P a g e | 19
Table 6 – BMP Implementation Schedule
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
P a g e | 20
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
P a g e | 21
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs
The project will not proposed any LID BMPs for this site. If it becomes necessary, the BMPs
listed in Elements 1-12 shall be used to protect LID BMPs.
P a g e | 22
3 Pollution Prevention Team
Table 7 – Team Information
Title Name(s) Phone Number
Certified Erosion and
Sediment Control Lead
(CESCL)
TBD TBD
Resident Engineer TBD 425-869-2670
Emergency Ecology
Contact
Rob Walls 425-649-7130
Emergency Permittee/
Owner Contact
Mark Clement 206-617-2944
Non-Emergency Owner
Contact
Mark Clement 206-617-2944
Monitoring Personnel TBD TBD
Ecology Regional Office Northwest Regional Office 425-649-7000
P a g e | 23
4 Monitoring and Sampling Requirements
Monitoring includes visual inspection, sampling for water quality parameters of concern, and
documentation of the inspection and sampling findings in a site log book. A site log book will be
maintained for all on-site construction activities and will include:
• A record of the implementation of the SWPPP and other permit requirements
• Site inspections
• Stormwater sampling data
The site log book must be maintained on-site within reasonable access to the site and be made
available upon request to Ecology or the local jurisdiction.
The receiving waterbody, Lake Washington, is impaired for: Bacteria and Total Phosphorus. All
stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for
pH and/or 25NTU for turbidity.
4.1 Site Inspection
Site inspections will be conducted at least once every calendar week and within 24 hours
following any discharge from the site. For sites that are temporarily stabilized and inactive, the
required frequency is reduced to once per calendar month.
The discharge point(s) is located at the existing catch basin structure at the west end of the
property.
4.2 Stormwater Quality Sampling
4.2.1 Turbidity Sampling
Requirements include calibrated turbidity meter or transparency tube to sample site discharges
for compliance with the CSWGP. Sampling will be conducted at all discharge points at least
once per calendar week.
Method for sampling turbidity:
Table 8 – Turbidity Sampling Method
Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size)
Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size)
The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency
less than 33 centimeters.
If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to
or greater than 6 cm, the following steps will be conducted:
1. Review the SWPPP for compliance with Special Condition S9. Make appropriate
revisions within 7 days of the date the discharge exceeded the benchmark.
P a g e | 24
2. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible. Address the problems within 10
days of the date the discharge exceeded the benchmark. If installation of necessary
treatment BMPs is not feasible within 10 days, Ecology may approve additional time
when the Permittee requests an extension within the initial 10-day response period.
3. Document BMP implementation and maintenance in the site log book.
If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following
steps will be conducted:
1. Telephone or submit an electronic report to the applicable Ecology Region’s
Environmental Report Tracking System (ERTS) within 24 hours.
• Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish,
Whatcom): (425) 649-7000 or
http://www.ecy.wa.gov/programs/spills/forms/nerts_online/NWRO_nerts_online.html
2. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible. Address the problems within 10
days of the date the discharge exceeded the benchmark. If installation of necessary
treatment BMPs is not feasible within 10 days, Ecology may approve additional time
when the Permittee requests an extension within the initial 10-day response period
3. Document BMP implementation and maintenance in the site log book.
4. Continue to sample discharges daily until one of the following is true:
• Turbidity is 25 NTU (or lower).
• Transparency is 33 cm (or greater).
• Compliance with the water quality limit for turbidity is achieved.
o 1 - 5 NTU over background turbidity, if background is less than 50 NTU
o 1% - 10% over background turbidity, if background is 50 NTU or greater
• The discharge stops or is eliminated.
P a g e | 25
4.2.2 pH Sampling
pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards
poured concrete over the life of the project). The use of recycled concrete or engineered soils
(soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln
dust [CKD] or fly ash) also requires pH monitoring.
For significant concrete work, pH sampling will start the first day concrete is poured and
continue until it is cured, typically three (3) weeks after the last pour.
For engineered soils and recycled concrete, pH sampling begins when engineered soils or
recycled concrete are first exposed to precipitation and continues until the area is fully
stabilized.
If the measured pH is 8.5 or greater, the following measures will be taken:
1. Prevent high pH water from entering storm sewer systems or surface water.
2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate
technology such as carbon dioxide (CO2) sparging (liquid or dry ice).
3. Written approval will be obtained from Ecology prior to the use of chemical treatment
other than CO2 sparging or dry ice.
Method for sampling pH:
Table 9 – pH Sampling Method
pH meter
pH test kit
Wide range pH indicator paper
P a g e | 26
5 Discharges to 303(d) or Total Maximum Daily Load (TMDL)
Waterbodies
5.1 303(d) Listed Waterbodies
Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH?
Yes No
List the impairment(s):
The receiving waterbody, Lake Washington, is impaired for: Bacteria and Total Phosphorus. All
stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for
pH and/or 25NTU for turbidity
5.2 TMDL Waterbodies
Waste Load Allocation for CWSGP discharges:
N/A
List and describe BMPs:
N/A
Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point
of discharge.
The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water
Body form is included in Appendix F.
P a g e | 27
6 Reporting and Record Keeping
6.1 Record Keeping
6.1.1 Site Log Book
A site log book will be maintained for all on-site construction activities and will include:
• A record of the implementation of the SWPPP and other permit requirements
• Site inspections
• Sample logs
6.1.2 Records Retention
Records will be retained during the life of the project and for a minimum of three (3) years
following the termination of permit coverage in accordance with Special Condition S5.C of the
CSWGP.
Permit documentation to be retained on-site:
• CSWGP
• Permit Coverage Letter
• SWPPP
• Site Log Book
Permit documentation will be provided within 14 days of receipt of a written request from
Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when
requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP.
6.1.3 Updating the SWPPP
The SWPPP will be modified if:
• Found ineffective in eliminating or significantly minimizing pollutants in stormwater
discharges from the site.
• There is a change in design, construction, operation, or maintenance at the construction
site that has, or could have, a significant effect on the discharge of pollutants to waters
of the State.
The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine
additional or modified BMPs are necessary for compliance. An updated timeline for BMP
implementation will be prepared.
P a g e | 28
6.2 Reporting
6.2.1 Discharge Monitoring Reports
Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring
Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given
monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR
due date is fifteen (15) days following the end of each calendar month.
DMRs will be reported online through Ecology’s WQWebDMR System.
6.2.2 Notification of Noncompliance
If any of the terms and conditions of the permit is not met, and the resulting noncompliance may
cause a threat to human health or the environment, the following actions will be taken:
1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable
Regional office ERTS phone number (Regional office numbers listed below).
2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or
correct the noncompliance. If applicable, sampling and analysis of any noncompliance
will be repeated immediately and the results submitted to Ecology within five (5) days of
becoming aware of the violation.
3. A detailed written report describing the noncompliance will be submitted to Ecology
within five (5) days, unless requested earlier by Ecology.
Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6
cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as
required by Special Condition S5.A of the CSWGP.
• Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit,
Snohomish, or Whatcom County
Include the following information:
1. Your name and / Phone number
2. Permit number
3. City / County of project
4. Sample results
5. Date / Time of call
6. Date / Time of sample
7. Project name
In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will
be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH
water.
P a g e | 29
A. Site Map
RENTON SITE
SITE PLAN
C3 C1
GALVANIZATION NOTE LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
GV Inlet
Outlet
CONTROL POINT TABLE
RENTON SITE
SITE PLAN
C4 C2
GALVANIZATION NOTE LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
CONTROL POINT TABLE
LAND USE PERMIT/SEPA
NOT FOR CONSTRUCTION
RENTON SITE
SITE PLAN
C5 C3
GALVANIZATION NOTE
P a g e | 30
B. BMP Detail
The following BMPs will be implemented for this project:
• Plastic or Metal Fence (BMP D.2.1.1.1) (if necessary)
• Plastic Covering (BMP D.2.1.2.4)
• Temporary and Permanent Seeding (BMP D.2.1.2.6) (if necessary)
• Triangular Silt Dike (BMP D.2.1.3.4)
• Stabilized Construction Entrance (BMP D.2.1.4.1) (if necessary)
• Construction Road/Parking Area Stabilization (BMP D.2.1.4.2)
• Wheel Wash (BMP D.2.1.4.3) (if necessary)
• Storm Drain Inlet Protection (BMP D.2.1.5.3)
• Dust Control (BMP D.2.1.8)
SECTION D.2.1 ESC MEASURES
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.
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 County 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 County 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 County 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.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-12
SECTION D.2.1 ESC MEASURES
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.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-20
D.2.1.2 COVER MEASURES
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.
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.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-21
SECTION D.2.1 ESC MEASURES
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 County'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. At 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 DPER inspector. The DPER 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 April 1 through June 30, and September 1 through October 15. Areas may be
seeded between July 1 and August 31, but irrigation may be required in order to grow adequate cover.
Areas may also be seeded during the winter months, but it may take several months 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 be firm but not 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).
4/24/2016 2016 Surface Water Design Manual – Appendix D D-24
D.2.1.2 COVER MEASURES
b) If seeding during the wet season, mulch is required.
c) The use of mulch may be required during the dry season at the County'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. During the wet season, the application rate shall be doubled because
the mulch and tackifier used in hydroseeding break down fairly rapidly. It may be necessary in some
applications to include straw with the wood fiber, but this can be detrimental to germination.
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 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 120 pounds per acre.
This rate may be reduced if soil amendments or slow-release fertilizers are used. Local suppliers
should be consulted for their recommendations because the appropriate mix depends on a variety of
factors, including exposure, soil type, slope, and expected foot traffic. Alternative seed mixes
approved by the County may be used.
Table D.2.1.2.B presents the standard mix for those areas where just a temporary vegetative cover is
required.
TABLE D.2.1.2.B TEMPORARY EROSION CONTROL SEED MIX
% Weight % Purity % Germination
Chewings or red fescue
Festuca rubra var. commutata or
Festuca rubra
40 98 90
Annual or perennial rye
Lolium multiflorum or Lolium perenne
40 98 90
Redtop or colonial bentgrass
Agrostis alba or Agrostis tenuis
10 92 85
White dutch clover
Trifolium repens
10 98 90
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-25
SECTION D.2.1 ESC MEASURES
Table D.2.1.2.C provides just one recommended possibility for landscaping seed.
TABLE D.2.1.2.C LANDSCAPING SEED MIX
% Weight % Purity % Germination
Perennial rye blend
Lolium perenne
70 98 90
Chewings and red fescue blend
Festuca rubra var. commutata or
Festuca rubra
30 98 90
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
% Weight % Purity % Germination
Dwarf tall fescue (several varieties)
Festuca arundinacea var.
45 98 90
Dwarf perennial rye (Barclay)
Lolium perenne var. barclay
30 98 90
Red fescue
Festuca rubra
20 98 90
Colonial bentgrass
Agrostis tenuis
5 98 90
Table D.2.1.2.E presents a mix recommended for bioswales and other intermittently wet areas. 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*
% Weight % Purity % Germination
Tall or meadow fescue
Festuca arundinacea or
Festuca elatior
75-80 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 92 85
Redtop bentgrass
Agrostis alba or Agrostis gigantea
5-10 90 80
* Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
4/24/2016 2016 Surface Water Design Manual – Appendix D D-26
D.2.1.2 COVER MEASURES
The seed mix shown in Table D.2.1.2.F is a recommended low-growing, relatively 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 King County Surface Water Design Manual). Other mixes may be appropriate, depending on
the soil type and hydrology of the area. Apply this mixture at a rate of 60 pounds per acre.
TABLE D.2.1.2.F WET AREA SEED MIX*
% Weight % Purity % Germination
Tall or meadow fescue
Festuca arundinacea or
Festuca elatior
60-70 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 98 85
Meadow foxtail
Alepocurus pratensis
10-15 90 80
Alsike clover
Trifolium hybridum
1-6 98 90
Redtop bentgrass
Agrostis alba
1-6 92 85
* Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
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. The appropriateness of clover in the mix may need to
be considered as this can be a fairly invasive species. If the soil is amended, the addition of clover may
not be necessary.
TABLE D.2.1.2.G MEADOW SEED MIX
% Weight % Purity % Germination
Redtop or Oregon bentgrass
Agrostis alba or Agrostis oregonensis
40 92 85
Red fescue
Festuca rubra
40 98 90
White dutch clover
Trifolium repens
20 98 90
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 grass growth, this time limit may be relaxed at the discretion of the County
when critical areas would otherwise be protected.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-27
SECTION D.2.1 ESC MEASURES
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).
Design and Installation Specifications
Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root
mat for mechanical strength.
The following steps are recommended for sod installation:
1. Shape and smooth the surface to final grade in accordance with the approved grading plan.
2. Amend four inches (minimum) of well-rotted compost into the top eight inches of the soil if the
organic content of the soil is less than ten percent. Compost used shall meet compost specifications
per SWDM Reference 11-C.
3. Fertilize according to the supplier's recommendations. Disturbed areas within 200 feet of water bodies
and wetlands must use non-phosphorus fertilizer.
4. Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface.
5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water
flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit.
Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V.
6. Roll the sodded area and irrigate.
7. When sodding is carried out in alternating strips or other patterns, seed the areas between the sod
immediately after sodding.
Maintenance Standards
If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a
healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation,
instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and
protected with a net or blanket.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-28
D.2.1.3 PERIMETER PROTECTION
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" on page D-33).
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 (p. D-11).
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.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-37
SECTION D.2.1 ESC MEASURES
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.
Design and Installation Specifications
1. TSDs must be made of urethane foam sewn into a woven geosynthetic fabric.
2. TSDs are triangular, 10 inches to 14 inches high in the center, with a 20-inch to 28-inch base. A 2-
foot apron extends beyond both sides of the triangle along its standard section of 7 feet. A sleeve at
one end allows attachment of additional sections as needed
3. Install TSDs with ends curved up to prevent water from flowing around the ends
4. Attach the TSDs and their fabric flaps to the ground with wire staples. Wire staples must be No. 11
gauge wire or stronger and shall be 200 mm to 300 mm in length.
5. When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the abutting
unit and be stapled.
6. TSDs must be located and installed as soon as construction will allow.
7. TSDs must be placed perpendicular to the flow of water.
8. When used as check dams, the leading edge must be secured with rocks, sandbags, or a small key slot
and staples.
9. When used in grass-lined ditches and swales, the TSD check dams and accumulated sediment shall be
removed when the grass has matured sufficiently to protect the ditch or swale unless the slope of the
swale is greater than 4 percent. The area beneath the TSD check dams shall be seeded and mulched
immediately after dam removal.
Maintenance Standards
1. Triangular silt dikes shall be monitored for performance and sediment accumulation during and after
each runoff producing rainfall event. Sediment shall be removed when it reaches one half the height
of the silt dike.
2. Anticipate submergence and deposition above the triangular silt dike and erosion from high flows
around the edges of the dike/dam. Immediately repair any damage or any undercutting of the
dike/dam.
D.2.1.3.5 COMPOST BERMS
Code: COBE Symbol:
Purpose
Compost berms are an option to meet the requirements of perimeter protection. Compost berms may
reduce the transport of sediment from a construction site by providing a temporary physical barrier to
sediment and reducing the runoff velocities of overland flow. Compost berms trap sediment by filtering
water passing through the berm and allowing water to pond, creating a settling area for solids behind the
berm. Organic materials in the compost can also reduce concentrations of metals and petroleum
hydrocarbons from construction runoff. Due to the increase in phosphorous seen in the effluent data from
compost berms, they should be used with some cautions in areas that drain to phosphorus sensitive water
4/24/2016 2016 Surface Water Design Manual – Appendix D D-38
SECTION D.2.1 ESC MEASURES
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.
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.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-42
D.2.1.4 TRAFFIC AREA STABILIZATION
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.
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 STABILIZED CONSTRUCTION ENTRANCE
•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'
M
I
N
.
EXISTI
N
G
R
O
A
D
15' MIN.
NOTES:
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-43
SECTION D.2.1 ESC MEASURES
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 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 (p. D-64) 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 County 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.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-44
D.2.1.4 TRAFFIC AREA STABILIZATION
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 6inches 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.
3. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck
tongues with water.
4. Midpoint spray nozzles are only needed in very muddy conditions.
5. Wheel wash systems should be designed with a small grade change, 6 to 12 inches for a 10-foot wide
pond, to allow sediment to flow to the low side of the pond and to help prevent re-suspension of
sediment.
6. A drainpipe with a 2 to 3 foot riser should be installed on the low side of the wheel wash pond to
allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation
in a closed-loop system.
7. Polyacrylamide (PAM) added to the wheel washwater at a rate of 0.25 – 0.5 pounds per 1,000 gallons
of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or
erosion control and is being applied by a water truck, the same truck may be used to change the
washwater.
Maintenance Standards
1. The wheel wash should start out each day with clean, fresh water.
2. The washwater should be changed a minimum of once per day. On large earthwork jobs where more
than 10-20 trucks per hour are expected, the washwater will need to be changed more often.
3. Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system, such as
a closed-loop recirculation system or land application, or to the sanitary sewer system with proper
local sewer district approval or permits.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-45
SECTION D.2.1 ESC MEASURES
FIGURE D.2.1.4.B WHEEL WASH AND PAVED CONSTRUCTION ENTRANCE
2%
SLOPE
15'15'20'15'50'
18'
12'
3'
5'
BUILD 8'x8' SUMP TO ACCOMODATE
CLEANING BY TRACKHOE.SECTION A-A
NTS
8'x8' SUMP,
SEE NOTE
LOCATE INVERT OF TOP
PIPE 1' ABOVE BOTTOM
OF WHEEL WASH
DRAIN PIPE 1:1 SLOPE
WATER LEVEL
ELEVATION VIEW
NTS
PLAN VIEW
NTS
6" SLEEVE
CURB
ASPHALT CURB ON THE
LOW ROAD SIDE TO DIRECT
WATER BACK TO POND
6" ATB CONSTRUCTION
ENTRANCE
1-1/2" SCHEDULE 40
FOR SPRAYERS
2% SLOPE
MIDPOINT SPRAY
NOZZLES, IF NEEDED
3" TRASH PUMP WITH FLOATS
ON SUCTION HOSE
2" SCHEDULE 40
6" SLEEVE UNDER ROAD
8'x8' SUMP WITH 5'
OF CATCH
6" SEWER PIPE WITH
BUTTERFLY VALVES
1:1 SLOPE
A
A
5:1
SLOPE
5:1
SLOPE
15' ATB APRON TO PROTECT
GROUND FROM SPLASHING WATER BALL VALVES
NOTE:
4/24/2016 2016 Surface Water Design Manual – Appendix D D-46
D.2.1.5 SEDIMENT RETENTION
FIGURE D.2.1.5.D SEDIMENT POND RISER DETAIL
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.2.1.5.3 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. 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. Both
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-53
SECTION D.2.1 ESC MEASURES
options provide adequate protection, but filter fabric is likely to result in ponding of water above the
catch basin, while the insert will not. Thus, filter fabric is only allowed where ponding will not be a
traffic concern and where slope erosion will not result if the curb is overtopped by ponded water.
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.
The placement of filter fabric under grates is generally prohibited and the use of filter fabric over
grates is strictly limited and discouraged.
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.
4/24/2016 2016 Surface Water Design Manual – Appendix D D-54
D.2.1.5 SEDIMENT RETENTION
• 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.
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 - 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.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-55
SECTION D.2.1 ESC MEASURES
FIGURE D.2.1.5.E FILTER FABRIC PROTECTION
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
GRATECATCH BASIN
POROUS
BOTTOM
SOLID
WALLS
FILTER
MEDIA FOR
DEWATERING
4/24/2016 2016 Surface Water Design Manual – Appendix D D-56
D.2.1.5 SEDIMENT RETENTION
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:
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-57
SECTION D.2.1 ESC MEASURES
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:
4/24/2016 2016 Surface Water Design Manual – Appendix D D-58
D.2.1.8 DUST CONTROL
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 King County and must have prior
approval prior to use from the DPER inspector assigned to specific projects.
2016 Surface Water Design Manual – Appendix D 4/24/2016 D-69
SECTION D.2.1 ESC MEASURES
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
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
4/24/2016 2016 Surface Water Design Manual – Appendix D D-70
P a g e | 31
C. Correspondence
P a g e | 32
D. Site Inspection Form
Project
Name
Permit # Inspection Date Time
Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre
Print Name:
Approximate rainfall amount since the last inspection (in inches):
Approximate rainfall amount in the last 24 hours (in inches):
Current Weather Clear Cloudy Mist Rain Wind Fog
A. Type of inspection: Weekly Post Storm Event Other
B. Phase of Active Construction (check all that apply):
Pre Construction/installation of erosion/sediment
controls
Clearing/Demo/Grading Infrastructure/storm/roads
Concrete pours Vertical
Construction/buildings
Utilities
Offsite improvements Site temporary stabilized Final stabilization
C. Questions:
1. Were all areas of construction and discharge points inspected? Yes No
2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No
3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No
4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No
5. If yes to #4 was it reported to Ecology? Yes No
6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No
If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken,
and when.
*If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparenc y is 33
cm or greater.
Sampling Results: Date:
Parameter Method (circle one) Result Other/Note
NTU cm pH
Turbidity tube, meter, laboratory
pH Paper, kit, meter
P a g e | 33
D. Check the observed status of all items. Provide “Action Required “details and dates.
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
1
Clearing
Limits
Before beginning land disturbing
activities are all clearing limits,
natural resource areas (streams,
wetlands, buffers, trees) protected
with barriers or similar BMPs? (high
visibility recommended)
2
Construction
Access
Construction access is stabilized
with quarry spalls or equivalent
BMP to prevent sediment from
being tracked onto roads?
Sediment tracked onto the road
way was cleaned thoroughly at the
end of the day or more frequent as
necessary.
3
Control Flow
Rates
Are flow control measures installed
to control stormwater volumes and
velocity during construction and do
they protect downstream
properties and waterways from
erosion?
If permanent infiltration ponds are
used for flow control during
construction, are they protected
from siltation?
4
Sediment
Controls
All perimeter sediment controls
(e.g. silt fence, wattles, compost
socks, berms, etc.) installed, and
maintained in accordance with the
Stormwater Pollution Prevention
Plan (SWPPP).
Sediment control BMPs (sediment
ponds, traps, filters etc.) have been
constructed and functional as the
first step of grading.
Stormwater runoff from disturbed
areas is directed to sediment
removal BMP.
5
Stabilize
Soils
Have exposed un-worked soils
been stabilized with effective BMP
to prevent erosion and sediment
deposition?
P a g e | 34
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
5
Stabilize Soils
Cont.
Are stockpiles stabilized from erosion,
protected with sediment trapping
measures and located away from drain
inlet, waterways, and drainage
channels?
Have soils been stabilized at the end of
the shift, before a holiday or weekend
if needed based on the weather
forecast?
6
Protect
Slopes
Has stormwater and ground water
been diverted away from slopes and
disturbed areas with interceptor dikes,
pipes and or swales?
Is off-site storm water managed
separately from stormwater generated
on the site?
Is excavated material placed on uphill
side of trenches consistent with safety
and space considerations?
Have check dams been placed at
regular intervals within constructed
channels that are cut down a slope?
7
Drain Inlets
Storm drain inlets made operable
during construction are protected.
Are existing storm drains within the
influence of the project protected?
8
Stabilize
Channel and
Outlets
Have all on-site conveyance channels
been designed, constructed and
stabilized to prevent erosion from
expected peak flows?
Is stabilization, including armoring
material, adequate to prevent erosion
of outlets, adjacent stream banks,
slopes and downstream conveyance
systems?
9
Control
Pollutants
Are waste materials and demolition
debris handled and disposed of to
prevent contamination of stormwater?
Has cover been provided for all
chemicals, liquid products, petroleum
products, and other material?
Has secondary containment been
provided capable of containing 110%
of the volume?
Were contaminated surfaces cleaned
immediately after a spill incident?
Were BMPs used to prevent
contamination of stormwater by a pH
modifying sources?
P a g e | 35
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
9
Cont.
Wheel wash wastewater is handled
and disposed of properly.
10
Control
Dewatering
Concrete washout in designated areas.
No washout or excess concrete on the
ground.
Dewatering has been done to an
approved source and in compliance
with the SWPPP.
Were there any clean non turbid
dewatering discharges?
11
Maintain
BMP
Are all temporary and permanent
erosion and sediment control BMPs
maintained to perform as intended?
12
Manage the
Project
Has the project been phased to the
maximum degree practicable?
Has regular inspection, monitoring and
maintenance been performed as
required by the permit?
Has the SWPPP been updated,
implemented and records maintained?
13
Protect LID
Is all Bioretention and Rain Garden
Facilities protected from
sedimentation with appropriate BMPs?
Is the Bioretention and Rain Garden
protected against over compaction of
construction equipment and foot
traffic to retain its infiltration
capabilities?
Permeable pavements are clean and
free of sediment and sediment laden-
water runoff. Muddy construction
equipment has not been on the base
material or pavement.
Have soiled permeable pavements
been cleaned of sediments and pass
infiltration test as required by
stormwater manual methodology?
Heavy equipment has been kept off
existing soils under LID facilities to
retain infiltration rate.
E. Check all areas that have been inspected.
All in place BMPs All disturbed soils All concrete wash out area All material storage areas
All discharge locations All equipment storage areas All construction entrances/exits
P a g e | 36
F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number;
be specific on location and work needed. Document, initial, and date when the corrective action has been completed
and inspected.
Element
#
Description and Location Action Required Completion
Date
Initials
Attach additional page if needed
Sign the following certification:
“I certify that this report is true, accurate, and complete, to the best of my knowledge and belief”
Inspected by: (print) (Signature) Date:
Title/Qualification of Inspector:
P a g e | 37
E. Construction Stormwater General Permit (CSWGP)
P a g e | 38
F. 303(d) List Waterbodies / TMDL Waterbodies Information
Listing ID: 12193
Main Listing Information
Listing ID: 12193 2014 Category: 5
Waterbody Name: WASHINGTON LAKE 2012 Category: 5
Medium: Water 2008 Category: 5
Parameter: Bacteria 2004 Category: 5
WQI Project: None Assigned On 1998 303(d) List?: Y
Designated Use: None Assigned On 1996 303(d) List?: N
Assessment Unit
Assessment Unit ID: 47122F2A0
Location Identification
Counties: King
Waterbody ID (WBID): WA-08-9350
Town/Range/Section (Legacy): None Assigned
WRIA: 8 - Cedar-Sammamish
Waterbody Class: LAK
Basis
King County unpublished data from station 0828SB show a geometric mean of 220 cfu/100mL
with 53% exceeding the percentile criterion during 1998. King County unpublished data from
station 0828SB show a geometric mean of 82 cfu/100mL with 35% exceeding the percentile
criterion during 1999. King County unpublished data from station 0828SB show a geometric mean
of 94 cfu/100mL with 56% exceeding the percentile criterion during 2000. King County
unpublished data from station 0828SB show a geometric mean of 31 cfu/100mL with 20%
exceeding the percentile criterion during 2001. King County unpublished data from station
0828SB show a geometric mean of 105 cfu/100mL with 50% exceeding the percentile criterion
during 2002.
Remarks
No Remarks Entered
EIM
No EIM Records Entered
Page 1 of 1Print Approved Listing
5/22/2019https://apps.ecology.wa.gov/approvedwqa/ApprovedPrintListing.aspx?LISTING_ID=12193
Listing ID: 52853
Main Listing Information
Listing ID: 52853 2014 Category: 5
Waterbody Name: WASHINGTON LAKE 2012 Category: 5
Medium: Water 2008 Category: 5
Parameter: Total Phosphorus 2004 Category: 3
WQI Project: None Assigned On 1998 303(d) List?: N
Designated Use: None Assigned On 1996 303(d) List?: N
Assessment Unit
Assessment Unit ID: 47122H2E6
Location Identification
Counties: King
Waterbody ID (WBID): None Assigned
Town/Range/Section (Legacy): None Assigned
WRIA: 8 - Cedar-Sammamish
Waterbody Class: LAK
Basis
Location ID [KCM-0804] -- In 2004 the summer epilimnetic mean concentration of total
phosphorus samples did not exceed the action value for this ecoregion (20 ug/L).
Location ID [KCM-0804] -- In 2005 the summer epilimnetic mean concentration of total
phosphorus samples did not exceed the action value for this ecoregion (20 ug/L).
Location ID [KCM-0804] -- In 2006 the summer epilimnetic mean concentration of total
phosphorus samples exceeded the action value for this ecoregion (20 ug/L).
Remarks
No Remarks Entered
EIM
User Study ID:User Location ID:
KClake-1 KCM-0804
KClake-1 KCM-0804
Page 1 of 1Print Approved Listing
5/22/2019https://apps.ecology.wa.gov/approvedwqa/ApprovedPrintListing.aspx?LISTING_ID=52853
P a g e | 39
G. Contaminated Site Information
P a g e | 40
H. Engineering Calculations
Appendix B
WWHM Report
WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: Apron E - Flow Rate
Site Name:
Site Address:
City :
Report Date: 6/13/2019
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2018/10/10
Version : 4.2.16
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : On-site Basin
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Lawn, Flat 1
Pervious Total 1
Impervious Land Use acre
ROADS FLAT 8.85
ROOF TOPS FLAT 0.28
Impervious Total 9.13
Basin Total 10.13
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : On-site Basin
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Lawn, Flat .89
Pervious Total 0.89
Impervious Land Use acre
ROADS FLAT 7.4
ROOF TOPS FLAT 1.84
Impervious Total 9.24
Basin Total 10.13
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
ANALYSIS RESULTS
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:1
Total Impervious Area:9.13
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.89
Total Impervious Area:9.24
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 3.545198
5 year 4.499727
10 year 5.150686
25 year 5.997548
50 year 6.64738
100 year 7.314334
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 3.580111
5 year 4.541324
10 year 5.196539
25 year 6.04863
50 year 6.702267
100 year 7.37296
___________________________________________________________________
WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: Boeing Apron E WQ Treatment - North
Site Name: Boeing Apron E
Site Address:
City : Renton
Report Date: 6/13/2019
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2017/04/14
Version : 4.2.13
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Flat 3.43
Pervious Total 3.43
Impervious Land Use acre
Impervious Total 0
Basin Total 3.43
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre
PARKING FLAT 3.43
Impervious Total 3.43
Basin Total 3.43
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:3.43
Total Impervious Area:0
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0
Total Impervious Area:3.43
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.100845
5 year 0.158381
10 year 0.190987
25 year 0.225531
50 year 0.246907
100 year 0.265088
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 1.307737
5 year 1.651824
10 year 1.885607
25 year 2.188858
50 year 2.420958
100 year 2.658694
___________________________________________________________________
___________________________________________________________________
Water Quality BMP Flow and Volume for POC #1
On-line facility volume: 0.4218 acre-feet
On-line facility target flow: 0.557 cfs.
Adjusted for 15 min: 0.557 cfs.
Off-line facility target flow: 0.3148 cfs. = 141.3 gpm
Adjusted for 15 min: 0.3148 cfs.
___________________________________________________________________
This program and accompanying documentation are provided 'as-is' without warranty of any kind. The
entire risk regarding the performance and results of this program is assumed by End User. Clear Creek
Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed
or implied, including but not limited to implied warranties of program and accompanying documentation.
In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without
limitation to damages for loss of business profits, loss of business information, business
interruption, and the like) arising out of the use of, or inability to use this program even if Clear
Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such
damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2019; All Rights Reserved.
WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: Boeing Apron E WQ Treatment - South
Site Name: Boeing Apron E
Site Address:
City : Renton
Report Date: 6/13/2019
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2017/04/14
Version : 4.2.13
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Flat 4.33
Pervious Total 4.33
Impervious Land Use acre
Impervious Total 0
Basin Total 4.33
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre
PARKING FLAT 4.33
Impervious Total 4.33
Basin Total 4.33
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:4.33
Total Impervious Area:0
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0
Total Impervious Area:4.33
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.127306
5 year 0.199938
10 year 0.241101
25 year 0.284708
50 year 0.311693
100 year 0.334645
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 1.650876
5 year 2.085247
10 year 2.380373
25 year 2.763193
50 year 3.056193
100 year 3.356309
___________________________________________________________________
___________________________________________________________________
Water Quality BMP Flow and Volume for POC #1
On-line facility volume: 0.5325 acre-feet
On-line facility target flow: 0.7032 cfs.
Adjusted for 15 min: 0.7032 cfs.
Off-line facility target flow: 0.3975 cfs. = 178.4 gpm
Adjusted for 15 min: 0.3975 cfs.
___________________________________________________________________
This program and accompanying documentation are provided 'as-is' without warranty of any kind. The
entire risk regarding the performance and results of this program is assumed by End User. Clear Creek
Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed
or implied, including but not limited to implied warranties of program and accompanying documentation.
In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without
limitation to damages for loss of business profits, loss of business information, business
interruption, and the like) arising out of the use of, or inability to use this program even if Clear
Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such
damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2019; All Rights Reserved.
Appendix C
Water Quality Treatment Standard Detail
STANDARD DETAIL
STORMWATER BIOFILTRATION SYSTEM
MWS-L-8-12-V
PLAN VIEW
ELEVATION VIEW
RIGHT END VIEW
LEFT END VIEW
GENERAL NOTES
INSTALLATION NOTES
SITE SPECIFIC DATA
STANDARD DETAIL
STORMWATER BIOFILTRATION SYSTEM
MWS-L-8-16-V
PLAN VIEW
ELEVATION VIEW
RIGHT END VIEW
LEFT END VIEW
GENERAL NOTES
INSTALLATION NOTES
SITE SPECIFIC DATA