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TECHNICAL INFORMATION REPORT
Renton Park Elementary School
ADA Improvements
16828 128th Ave SE
Renton, WA 98058
April 14, 2023
PREPARED FOR:
Renton School District – Capital Planning & Construction
Mike Cato
7812 South 124th Street
Seattle, WA 98178
PREPARED THROUGH:
Renton School District – Capital Planning & Construction
Alisha Smothers
7812 South 124th Street
Seattle, WA 98178
PREPARED BY:
Jacobson Consulting Engineers
Sascha Eastman
206.426.2600
sascha@jacobsonengineers.com
DEVELOPMENT ENGINEERING
SAMorman 04/28/2023
i
Technical Information Report for
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
JCE Project No. C220041-0159
April 14, 2023
TABLE OF CONTENTS
1. PROJECT OVERVIEW ................................................................................................................................ 3
GENERAL DESCRIPTION .............................................................................................................................. 3
EXISTING CONDITIONS ................................................................................................................................. 3
PROPOSED DRAINAGE SYSTEM ................................................................................................................. 4
2. CONDITIONS AND REQUIREMENTS SUMMARY ......................................................................................... 5
CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION ................... 5
SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS ........................... 5
SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION ..................................................... 6
SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES ............................................................ 6
SPECIAL REQUIREMENT #4: SOURCE CONTROLS .................................................................................. 6
SPECIAL REQUIREMENT #6: AQUIFER PROTECTION AREA .................................................................. 6
3. OFFSITE ANALYSIS .................................................................................................................................. 7
FIELD INSPECTION ........................................................................................................................................ 7
DRAINAGE SYSTEM PROBLEM DESCRIPTIONS ....................................................................................... 7
UPSTREAM ANALYSIS ................................................................................................................................... 7
DOWNSTREAM ANALYSIS ............................................................................................................................ 7
MITIGATION OF EXISTING OR POTENTIAL PROBLEMS ........................................................................... 7
4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND
DESIGN ........................................................................................................................................................... 8
FLOW CONTROL SYSTEM ............................................................................................................................ 8
LOW IMPACT DEVELOPMENT (LID) ............................................................................................................. 8
WATER QUALITY SYSTEM ............................................................................................................................ 8
5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ........................................................................................ 9
DEVELOPED STORM SYSTEM DESCRIPTION ........................................................................................... 9
OUTFALLS ....................................................................................................................................................... 9
CONVEYANCE REQUIREMENTS.................................................................................................................. 9
6. SPECIAL REPORTS AND SUMMARY ........................................................................................................ 10
7. OTHER PERMITS ................................................................................................................................... 11
8. CSWPP ANALYSIS AND DESIGN ............................................................................................................. 12
STANDARD REQUIREMENTS .....................................................................................................................12
9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ....................................... 13
BOND QUANTITIES WORKSHEET..............................................................................................................13
FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH .......................13
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ
FACILITIES .....................................................................................................................................................13
DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL BMP’S .................13
10. OPERATIONS AND MAINTENANCE MANUAL ........................................................................................... 14
11. FIGURES ............................................................................................................................................... 15
12. APPENDICES ......................................................................................................................................... 16
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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1. PROJECT OVERVIEW
GENERAL DESCRIPTION
The following Drainage Report provides the design narrative and discussion for the Renton Park Elementary School
ADA Improvements project scheduled to begin construction in the Summer of 2023. The storm water design for
the project was based on the requirements set forth in the 2022 City of Renton Water Design Manual (RSWDM).
Renton Park Elementary School is with the City of Renton jurisdictional limits and located at 16828 128th Ave SE,
Renton, WA 98058 (Parcel Number 282305-9084). The site is bordered on north side of the site by SE 168th
Street, to the west is 128th Ave SE, single family residential homes to the south, and Renton Park to the east of the
school’s property. See Figure 2 - Vicinity Map.
The project will occur in the NW corner of the site adjacent to and west of the main entrance to the school on the
north side of the bus and parent drop-off pickup loop. Work consists of replacing and modifying the existing ADA
parking stalls and portion of existing sidewalk from ADA parking stalls to the school entrance as required to meet
accessibility code requirements.
Some additional security improvements are also proposed for the project, that will involve removing the existing
non-traffic rated bollards that near the school building entrance and replacing with heavy duty traffic rated security
bollards. The new bollards will provide security measures to parents, staff, and students to keep vehicles from
“jumping” the curb and driving onto the sidewalk. To install the new bollards, the existing concrete sidewalk will
be sawcut and removed and replaced as necessary.
EXISTING CONDITIONS
Renton Park Elementary School is a developed campus consisting of single primary school building in the middle
of the campus, parking and drive areas on the west and north side of building, hard surface play areas with covered
play shelter and natural grass playfield to the east, and landscaping around the property perimeter and in the
parking lots, and south of the school building. The main building is surrounded by low landscaping and concrete
sidewalks. Storm water from the existing impervious asphalt and sidewalk in the project vicinity drains to a central
landscape island that is developed with an existing grass bioswale that collects the stormwater and conveys it to
the NW corner of the site to another existing grass bioswale, that treats the stormwater prior to discharging the
stormwater to an existing catch basin in 128th Ave SE at the approximate SE corner of the intersection with SE
168th Street. See Figure 3 – Storm Drainage As-Built.
Table 1A below summarizes the land cover characteristics of the of the existing current project site area (See Civil
Sheet C100 – Demolition and TESC Plan and Figure 4 – Existing Conditions).
TABLE 1A – PROJECT SITE AREA EXISTING SITE CONDITIONS
Land Cover Area (square feet)
Impervious Area – ADA Parking Lot,
Driveway (Asphalt), & Concrete Sidewalks
4,209
Pervious Area - Grass 244
*Total Project Area 4,453
% Impervious of Project Area 94.5%
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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PROPOSED DRAINAGE SYSTEM
The storm water runoff for the disturbed areas at both the ADA parking stalls and concrete sidewalk to the north
will continue to sheet flow and drain uninterrupted in its natural current drainage course and conveyed off-site as
described above in Existing Conditions Section. However, the ADA Parking Stalls are being regraded to meet ADA
accessibility code requirements, and as such, a new low point is being created that will require and additional
catch basin and roughly 21 feet of 6” storm pipe to be installed and connected to the existing catch basin located
near the NE corner of the ADA parking area.
The project is not proposing any further storm drainage mitigation efforts as the project will only create 85 sq ft of
new impervious surface area and will continue to utilize the existing stormwater BMPs that are in place – bioswale
in both the center island and north of the project improvements in the NW corner of the school campus. The
project will install more than 2,000 square feet (sf) of new plus replaced impervious surface (see Table 2 below),
which triggers Full Drainage Review per the City of Renton SWDM Section 1.1.2.4, however after discussions with
the City of Renton, due to the limited scope of the project with only 85 sq ft of new impervious surface being
constructed and the rest being replaced to meet ADA code, a Targeted Drainage Review (TDR) Project Category 1
was determined to be more applicable. The requirements for a TDR Project Category 1 are set forth in the 2022
City of Renton SWDM Section 1.1.2.2 – see 1-18 of the RSWDM.
Table 2 summarizes the land cover characteristics of the proposed project disturbed site area (See Figure 5 – New
+ Replaced Impervious Areas).
TABLE 2 – DEVELOPED PROJECT SITE CONDITIONS AREA BREAKDOWN
Land Cover Area (square feet)
Impervious Area – ADA Parking Lot,
Driveway (Asphalt), & Concrete Sidewalks
4,294
Pervious Area - Grass 159
*Total Project Area 4,453
% Impervious of Project Area 96.4%
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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2. CONDITIONS AND REQUIREMENTS SUMMARY
The project will install more than 2,000 square feet (sf) of new plus replaced impervious surface (see Table 2
below), which triggers Full Drainage Review per the City of Renton SWDM Section 1.1.2.4, however after
discussions with the City of Renton, due to the limited scope of the project with only 85 sq ft of new impervious
surface being constructed and the rest being replaced to meet ADA code, a Targeted Drainage Review (TDR)
Project Category 1 was determined to be more applicable. The requirements for a TDR Project Category 1 are set
forth in the 2022 City of Renton SWDM Section 1.1.2.2 – see 1-18 of the RSWDM.
This section of the report will address the Core Requirement #5 and Special Requirements #1-4, and #6 for TDR
Project Category #1 as set forth by Section 1.1.2.2 of the 2022 RSWDM.
CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION
All proposed projects that will clear, grade, or otherwise disturb the site must provide erosion and sediment
controls to prevent, to the maximum extent practicable, the transport of sediment from the project site to
downstream drainage facilities, water resources, and adjacent properties. All proposed projects that will conduct
construction activities onsite or offsite must provide stormwater pollution prevention and spill controls to prevent,
reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses. To
prevent sediment transport and pollutant discharges as well as other impacts related to land-disturbing and
construction activities, Erosion and Sediment Control (ESC) measures and Stormwater Pollution Prevention and
Spill Control (SWPPS) measures that are appropriate to the project site must be applied through a comprehensive
Construction Stormwater Pollution Prevention (CSWPP) plan as described in Sections 1.2.5.1 and 1.2.5.3 and
shall perform as described in Section 1.2.5.2. See Appendix B – Construction Stormwater Pollution Prevention
Plan (CSWPPP). In addition, these measures, both temporary and permanent, shall be implemented consistent
with the requirements in Section 1.2.5.3 that apply to the proposed project.
In order to prevent erosion and trap sediments within the project site, the following BMPs will be implemented
approximately as indicated and noted on Sheets C100 and C110, and will include, but are not limited to the
following:
· Clearing limits will be marked by fencing or other means on the ground.
· Cleared areas will be seeded and mulched.
· Runoff will not be allowed to concentrate, and no water will be allowed to point discharge off the site.
· Straw wattles will be placed at all curb openings of the center curb island located south of the project
improvements.
· Mulch will be spread over all cleared areas of the site when they are not being worked. Mulch will consist
of air-dried straw and chipped site vegetation.
· Filter Fabric protection will be installed in existing storm drainage structures and remain until the site is
stabilized.
SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS
The RSWDM is one of several adopted regulations in in the City of Renton that apply requirements for controlling
drainage on an area-specific basis. Other adopted area-specific regulations with requirements that have a
direct bearing on the drainage design of a proposed project are found in Section 1.3.1 of the RSWDM.
To the best of our knowledge, there are no adopted area-specific requirements in the area of the proposed project
site development that would impact the current Renton Surface Water Design Manual (RSWDM) requirements for
this project. Therefore, the project will adhere to the requirements set forth in the 2022 RSWDM.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION
Flood hazard areas are composed of the 100-year floodplain, zero-rise flood fringe, zero-rise floodway, FEMA
floodway. If a proposed project contains or is adjacent to a flood hazard area as determined by CED, this special
requirement requires the project to determine those components that are applicable and delineate them on the
project’s site improvement plans and recorded maps.
To the best of our knowledge in reviewing both FEMA Flood Insurance Rate Maps and the King County iMap, the
proposed project site area in not located within a 100-year floodplain.
SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES
Flood protection facilities, such as levees and revetments, require a high level of confidence in their structural
integrity and performance. Proper analysis, design, and construction is necessary to protect against the potentially
catastrophic consequences if such facilities should fail.
To the best of our knowledge in reviewing both FEMA Flood Insurance Rate Maps and the King County iMap, the
proposed project site area is not located within a 100-year floodplain and not located adjacent to any rivers,
streams, creeks, or other water bodies, and does not have any existing flood protection facilities installed on the
existing property, nor are any new flood protection facilities proposed to be installed or warranted for this project.
SPECIAL REQUIREMENT #4: SOURCE CONTROLS
If a proposed project requires a commercial building or commercial site development permit then water quality
source controls applicable to the proposed project shall be applied as described below in accordance with the King
County Stormwater Pollution Prevention Manual and King County Code 9.12.
No structural improvements are proposed that will require source controls.
SPECIAL REQUIREMENT #6: AQUIFER PROTECTION AREA
Aquifer Protection Area(s) (APA) are identified in the RMC 4-3-050. If a proposed project is located within the
APA, this special requirement requires the project to determine those components that are applicable and
delineate them on the project’s site improvements plans. APA zones are depicted in the Wellhead Protection Area
Zones layer of COR Maps (<https://maps.rentonwa.gov/Html5viewer/Index.html?viewer=cormaps>).
The subject project is not located in an aquifer protection area according to the online City of Renton COR Maps.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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3. OFFSITE ANALYSIS
FIELD INSPECTION
A Site visit has been made to gather information about the existing campus, including, but not limited to, review of
parking lots on west, sidewalks and loop drive, including the bioswales and existing drainage system. This field
visit took place in the Fall of 2022. Please refer to Downstream Analysis below for more information.
DRAINAGE SYSTEM PROBLEM DESCRIPTIONS
There are no known drainage concerns or any existing drainage problems per review of the site with the Renton
School District and the King County iMap and City of Renton COR Maps ‘Drainage Complaints’ Layer. As such, no
drainage problems are anticipated to be present in the redevelopment as a result of any previous existing problems.
UPSTREAM ANALYSIS
Due to the topography of the site falling from the south to the north, with stormwater runoff for the loop drive,
generally draining to the center landscape islands, upstream runoff onto the site is anticipated to be negligible,
with upstream stormwater runoff being diverted around the project site areas via a piped storm drainage system.
DOWNSTREAM ANALYSIS
According to both the project’s record of survey and the City of Renton COR Maps website, stormwater from the
project area, storm water from the ADA Parking Lot and concrete sidewalk in the project vicinity drains to a central
landscape island that is developed with an existing grass bioswale that collects the stormwater and conveys it to
the NW corner of the site to another existing grass bioswale, that treats the stormwater prior to discharging the
stormwater to an existing catch basin in 128th Ave SE at the approximate SE corner of the intersection with SE
168th Street. The stormwater is then conveyed west in the storm system in SE 168th Street, then north in the
storm system in 126th Ave SE, then continues north and northwest through a series of storm structures and pipes,
until it outfalls to a regional stormwater facility in Tiffany Cascade Connector located northwest of the intersection
of SE 160th Street and 132nd Ave SE approximately 3/4 mile downstream.
MITIGATION OF EXISTING OR POTENTIAL PROBLEMS
The site is not within or near any FEMA flood zones, no existing problems are known, and no potential problems are
expected as a result of the proposed development.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER
QUALITY FACILITY ANALYSIS AND DESIGN
FLOW CONTROL SYSTEM
This project is not required to comply with Core Requirement #3 and also proposes less than 5,000 square-feet of
new plus replaced impervious surfaces and less than ¾ acre of new pervious surface, therefore flow control is not
proposed.
LOW IMPACT DEVELOPMENT (LID)
The project will create more than 2,000 sq ft of new plus replaced impervious surface are, but less than 7,000
square feet of land, but will only create 85 sq ft of new impervious surface area, with the remaining being replaced
to meet ADA code (4,209 sq ft) and will therefore continue to utilize the existing functioning bioswales located in
the center curb island located south of improvements across the drive aisle, and north of the improvements in the
NW corner of the existing site.
WATER QUALITY SYSTEM
The project is not required to comply with Core Requirement #8 and also proposes less than 5,000 square-feet of
new plus replaced pollution generating impervious surfaces and less than ¾ acre of new pollution generating
pervious surfaces, therefore water quality treatment is not proposed.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
This section discusses the criteria that will be used to analyze and design the proposed storm conveyance system.
DEVELOPED STORM SYSTEM DESCRIPTION
The ADA Parking Stalls are being regraded to meet ADA accessibility code requirements, and as such, a new low
point is being created that will require and additional catch basin and roughly 21 feet of 6” storm pipe to be
installed and connected to the existing catch basin located near the NE corner of the ADA parking area. The new
storm pipe will be able to convey the 100-year peak flow rate. See Appendix C – Engineering Calculations.
OUTFALLS
The proposed redevelopment does not include any systems which utilize an outfall requiring outfall protection. The
majority of stormwater will sheet flow to the existing drainage swale in the center curb island before the stormwater
is conveyed north where it will outfall to the existing bioswale in the NW corner of the existing site.
CONVEYANCE REQUIREMENTS
· Pipe systems shall be designed with sufficient capacity to convey and contain the 25-year peak flow. Pipe
system structures may overtop for events that exceed the 25-year design capacity, provided that flow from
the 100-year runoff event does not create a severe flooding or erosion problem. The proposed 6-inch
Storm Pipe in ADA Parking Lot has been designed to convey the 100-year storm event. See Appendix C –
Engineering Calculations.
· New culverts shall be designed with sufficient capacity to meet headwater requirements and convey the
25-year peak flow. New culverts must also convey as much of the 100-year peak flow as necessary to
prevent severe flooding or erosion. New culverts proposed in streams with salmonids shall be designed to
provide for fish passage. No new culverts are proposed with this project.
· New ditches or channels shall be designed with sufficient capacity to convey and contain the 25-year
peak flow. New ditches and channels must also convey as much of the 100-year peak flow as necessary to
prevent severe flooding or erosion. No new ditches or channels are proposed with this project.
· New tightline conveyance systems traversing slopes steeper than 15% and greater than 20 feet in height
or are within a steep slope hazard area shall be designed with sufficient capacity to convey and contain
the 100-year peak flow. There are no slopes greater than 15% that are present within the project site area
or on-site.
· New bridges shall be designed to accommodate the 100-year peak flow in accordance with floodplain
development standards. No bridges are proposed with this project.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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6. SPECIAL REPORTS AND SUMMARY
No additional reports are included.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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7. OTHER PERMITS
City of Renton Building Permit for Striping Revisions is Required and will be applied for.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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8. CSWPP ANALYSIS AND DESIGN
This section lists the requirements that were met when designing the TESC Plan for this site.
STANDARD REQUIREMENTS
Erosion/Sedimentation Plan shall include the following:
1. Clearing Limits – Construction limits are delineated or noted on the project erosion control plans and
shall be physically laid out on the project site.
2. Cover Measures – Contractor will use plastic sheeting, hydroseeding, and mulching to protect soils
from erosion. Gravel borrow or “hog fuel” may be used in areas of excessively moist soils that will support
traffic loads, if necessary.
3. Perimeter Protection – Temporary construction fencing will be used to delineate and protect the
project clearing limits and provide a secure site. Straw wattles will be used to prevent sediment-laden
water from discharging from the site.
4. Traffic Area Stabilization – The existing drive aisles and parking lot will be utilized for construction
access, staging, and laydown as needed.
5. Sediment Retention – Filter fabric protect will also be installed in all new area drain structures and
remain until the site is stabilized.
6. Surface Water Collection – Straw wattles and filter fabric inserts placed in existing and new drainage
structures will be utilized as necessary to collect stormwater runoff.
7. Dewatering Control – Dewatering is not necessary for this site; therefore, no dewatering control
measures are implemented.
8. Dust Control – Dry soils will be appropriately sprinkled with water to limit airborne dust during dry
weather.
9. Flow Control – Discharge will be restricted and will therefore serve as a flow control measure.
10. Control Pollutants – BMPs shall be implemented to prevent or treat contamination of stormwater runoff
by pH modifying sources. Carbon dioxide sparging, using dry ice or a gas diffuser as a source of CO2 will
be used as needed to adjust the pH level and prevent discharge of water with elevated pH levels to the
City’s Storm System. In addition, dust control will be implemented as needed to prevent fugitive dust
during the treatment process. In addition, all waste materials from the site will be removed in a manner
that does not cause contamination of stormwater.
11. Protect Existing and Proposed Flow Control BMPs – The native vegetation will be protected with silt
fencing and perimeter construction fencing.
12. Maintain BMPs – BMPs for the project will be monitored for effectiveness on a regular basis to
ensure they are repaired and replaced as necessary.
13. Manage the Project – The project will be phased to take weather and seasonal work limits into
account. The BMPs will be inspected, maintained, and repaired as needed to ensure their intended
performance.
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9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF
COVENANT
BOND QUANTITIES WORKSHEET
A bond quantities worksheet has been completed and included in Appendix A.
FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH
No flow control or water quality facilities are proposed with this project.
DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ
FACILITIES
No flow control or water quality facilities are proposed with this project.
DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL BMP’S
No new flow control or water quality BMPs are proposed with this project.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
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10. OPERATIONS AND MAINTENANCE MANUAL
As stated in the Renton Surface Water Design Manual (RSWDM), the owner will maintain facilities. Though the
project is not proposing to install new Stormwater BMPs, but will instead utilize and maintain the existing
bioswales in the vicinity of the project site area, the project will issue O&M documentation to maintain those
existing Stormwater BMPs. Sections of the RSWDM outlining the operations and maintenance of these existing
facilities have been included in this section.
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2022 City of Renton Surface Water Design Manual 6/22/2022
A-1
APPENDIX A
MAINTENANCE REQUIREMENTS FOR
STORMWATER FACILITIES AND ON-SITE
BMPS
This appendix contains the maintenance requirements for the following typical stormwater flow control
and water quality facilities and on-site BMPs (ctrl/click the title to follow the link):
No. 1 – Detention Ponds
No. 2 – Infiltration Facilities
No. 3 – Detention Tanks and Vaults
No. 4 – Control Structure/Flow Restrictor
No. 5 – Catch Basins and Manholes
No. 6 – Conveyance Pipes and Ditches
No. 7 – Debris Barriers (e.g., trash racks)
No. 8 – Energy Dissipaters
No. 9 – Fencing
No. 10 – Gates/Bollards/Access Barriers
No. 11 – Grounds (landscaping)
No. 12 – Access Roads
No. 13 – Basic Bioswale (grass)
No. 14 – Wet Bioswale
No. 15 – Filter Strip
No. 16 – Wetpond
No. 17 – Wetvault
No. 18 – Stormwater Wetland
No. 19 – Sand Filter Pond
No. 20 – Sand Filter Vault
No. 21 – Proprietary Facility Cartridge Filter Systems
No. 22 – Baffle Oil/Water Separator
No. 23 – Coalescing Plate Oil/Water Separator
For Existing Bioswales
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
6/22/2022 2022 City of Renton Surface Water Design Manual
A-2
No. 24 – Catch Basin Insert (not allowed in the city for oil control)
No. 25 – Drywell BMP
No. 26 – Gravel Filled Infiltration Trench BMP
No. 27 – Gravel Filled Dispersion Trench BMP
No. 28 – Native Vegetated Surface/Native Vegetated Landscape BMP
No. 29 – Perforated Pipe Connections BMP
No. 30 – Permeable Pavement BMP
No. 31 – Bioretention BMP
No. 32 – RainWater Harvesting BMP
No. 33 – Rock Pad BMP
No. 34 – Sheet Flow BMP
No. 35 – Splash Block BMP
No. 36 – Vegetated Roof BMP
No. 37 – Rain Garden BMP
No. 38 – Soil Amendment BMP
No. 39 – Retained Trees
No. 40 – Filterra System
No. 41 – Compost Amended Vegetated Filter Strip (CAVFS)
No. 42 – Media Filter Drain (MFD)
No. 43 – Compost-Amended Biofiltration Swale
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
6/22/2022 2022 City of Renton Surface Water Design Manual
A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment
accumulation
Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert
of the lowest pipe into or out of the catch
basin or is within 6 inches of the invert of
the lowest pipe into or out of the catch
basin.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot
which is located immediately in front of the
catch basin opening or is blocking capacity
of the catch basin by more than 10%.
No Trash or debris blocking or potentially
blocking entrance to catch basin.
Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of
basin to invert the lowest pipe into or out of
the basin.
No trash or debris in the catch basin.
Dead animals or vegetation that could
generate odors that could cause
complaints or dangerous gases (e.g.,
methane).
No dead animals or vegetation present
within catch basin.
Deposits of garbage exceeding 1 cubic
foot in volume.
No condition present which would attract or
support the breeding of insects or rodents.
Damage to frame
and/or top slab
Corner of frame extends more than ¾ inch
past curb face into the street (If
applicable).
Frame is even with curb.
Top slab has holes larger than 2 square
inches or cracks wider than ¼ inch.
Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e.,
separation of more than ¾ inch of the
frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or
bottom
Cracks wider than ½ inch and longer than
3 feet, any evidence of soil particles
entering catch basin through cracks, or
maintenance person judges that catch
basin is unsound.
Catch basin is sealed and is structurally
sound.
Cracks wider than ½ inch and longer than
1 foot at the joint of any inlet/outlet pipe or
any evidence of soil particles entering
catch basin through cracks.
No cracks more than 1/4 inch wide at the
joint of inlet/outlet pipe.
Settlement/
misalignment
Catch basin has settled more than 1 inch
or has rotated more than 2 inches out of
alignment.
Basin replaced or repaired to design
standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering the catch basin at the joint of the
inlet/outlet pipes.
No cracks more than ¼-inch wide at the
joint of inlet/outlet pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and
non-floatables).
No trash or debris in pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2022 City of Renton Surface Water Design Manual 6/22/2022
A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe
(cont.)
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil
entering at the joints of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Metal Grates
(Catch Basins)
Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more
than 20% of grate surface. Grate free of trash and debris.
Damaged or missing
grate
Grate missing or broken member(s) of the
grate. Any open structure requires
urgent maintenance.
Grate is in place and meets design
standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in
place. Any open structure requires
urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools.
Bolts cannot be seated. Self-locking
cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to
remove
One maintenance person cannot remove
cover/lid after applying 80 lbs. of lift.
Cover/lid can be removed and reinstalled
by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
6/22/2022 2022 City of Renton Surface Water Design Manual
A-12
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment & debris
accumulation
Accumulated sediment or debris that
exceeds 20% of the diameter of the pipe.
Water flows freely through pipes.
Vegetation/root
growth in pipe
Vegetation/roots that reduce free
movement of water through pipes.
Water flows freely through pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Damage to protective
coating or corrosion
Protective coating is damaged; rust or
corrosion is weakening the structural
integrity of any part of pipe.
Pipe repaired or replaced.
Damaged pipes Any dent that decreases the cross section
area of pipe by more than 20% or is
determined to have weakened structural
integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per
1,000 square feet of ditch and slopes.
Trash and debris cleared from ditches.
Sediment
accumulation
Accumulated sediment that exceeds 20%
of the design depth.
Ditch cleaned/flushed of all sediment and
debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which
may constitute a hazard to City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
personnel or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Excessive vegetation
growth
Vegetation that reduces free movement of
water through ditches.
Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of
place or missing (If
applicable)
One layer or less of rock exists above
native soil area 5 square feet or more, any
exposed native soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
6/22/2022 2022 City of Renton Surface Water Design Manual
A-16
NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Chain Link Fencing
Gate
Damaged or missing
members
Missing gate. Gates in place.
Broken or missing hinges such that gate
cannot be easily opened and closed by a
maintenance person.
Hinges intact and lubed. Gate is working
freely.
Gate is out of plumb more than 6 inches
and more than 1 foot out of design
alignment.
Gate is aligned and vertical.
Missing stretcher bar, stretcher bands, and
ties.
Stretcher bar, bands, and ties in place.
Locking mechanism
does not lock gate
Locking device missing, non-functioning or
does not link to all parts.
Locking mechanism prevents opening of
gate.
Openings in fabric Openings in fabric are such that an 8-inch
diameter ball could fit through.
Fabric mesh openings within 50% of grid
size.
Bar Gate Damaged or missing
cross bar
Cross bar does not swing open or closed,
is missing or is bent to where it does not
prevent vehicle access.
Cross bar swings fully open and closed
and prevents vehicle access.
Locking mechanism
does not lock gate
Locking device missing, non-functioning or
does not link to all parts.
Locking mechanism prevents opening of
gate.
Support post
damaged
Support post does not hold cross bar up. Cross bar held up preventing vehicle
access into facility.
Bollards Damaged or missing
bollards
Bollard broken, missing, does not fit into
support hole or hinge broken or missing.
No access for motorized vehicles to get
into facility.
Bollards do not lock Locking assembly or lock missing or
cannot be attached to lock bollard in place.
No access for motorized vehicles to get
into facility.
Boulders Dislodged boulders Boulders not located to prevent motorized
vehicle access.
No access for motorized vehicles to get
into facility.
Evidence of vehicles
circumventing
boulders
Motorized vehicles going around or
between boulders.
No access for motorized vehicles to get
into facility.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2022 City of Renton Surface Water Design Manual 6/22/2022
A-17
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about
equal to the amount of trash it would take
to fill up one standard size office garbage
can). In general, there should be no visual
evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which
may constitute a hazard to City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
personnel or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Excessive growth of
grass/groundcover
Grass or groundcover exceeds 18 inches
in height.
Grass or groundcover mowed to a height
no greater than 6 inches.
Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as
having a potential to fall and cause
property damage or threaten human life. A
hazard tree identified by a qualified arborist must be removed as soon as
possible.
No hazard trees in facility.
Damaged tree or
shrub identified
Limbs or parts of trees or shrubs that are
split or broken which affect more than 25%
of the total foliage of the tree or shrub.
Trees and shrubs with less than 5% of total
foliage with split or broken limbs.
Trees or shrubs that have been blown
down or knocked over.
No blown down vegetation or knocked over
vegetation. Trees or shrubs free of injury.
Trees or shrubs which are not adequately
supported or are leaning over, causing
exposure of the roots.
Tree or shrub in place and adequately
supported; dead or diseased trees
removed.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2022 City of Renton Surface Water Design Manual 6/22/2022
A-19
NO. 13 – BASIC BIOSWALE (GRASS)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and/or debris accumulated on
the bioswale site.
No trash or debris on the bioswale site.
Contaminants and
pollution
Any evidence of contaminants or pollution
such as oil, gasoline, concrete slurries or
paint.
Materials removed and disposed of
according to applicable regulations. Source
control BMPs implemented if appropriate.
No contaminants present other than a
surface oil film.
Swale Section Sediment
accumulation
Sediment depth exceeds 2 inches in 10%
of the swale treatment area.
No sediment deposits in grass treatment
area of the bioswale.
Sediment inhibits grass growth over 10%
of swale length.
Grass growth not inhibited by sediment.
Sediment inhibits even spreading of flow. Flow spreads evenly through swale
Erosion/scouring Eroded or scoured swale bottom due to
channelization or high flows.
No eroded or scoured areas in bioswale.
Cause of erosion or scour addressed.
Poor vegetation
coverage
Grass is sparse or bare or eroded patches
occur in more than 10% of the swale
bottom.
Swale has no bare spots and grass is thick
and healthy.
Excessive vegetation
growth
Grass excessively tall (greater than 10
inches), grass is thin or nuisance weeds
and other vegetation have taken over.
Grass is between 3 and 4 inches tall, thick
and healthy. No nuisance vegetation
present.
Excessive shade Grass growth is poor because sunlight
does not reach swale.
Healthy grass growth or swale converted
to a wet bioswale.
Constant baseflow Continuous flow through the swale, even
when it has been dry for weeks or an
eroded, muddy channel has formed in the
swale bottom.
Baseflow removed from swale by a low-
flow pea-gravel drain or bypassed around
the swale.
Standing water Water pools in the swale between storms
or does not drain freely.
Swale freely drains and there is no
standing water in swale between storms.
Channelization Flow concentrates and erodes channel
through swale.
No flow channels in swale.
Flow Spreader Concentrated flow Flow from spreader not uniformly
distributed across entire swale width.
Flows are spread evenly over entire swale
width.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and
non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil
entering at the joints of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2022 City of Renton Surface Water Design Manual 6/22/2022
A-47
NO. 38 – SOIL AMENDMENT BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Soil Media Unhealthy vegetation Vegetation not fully covering ground
surface or vegetation health is poor.
Yellowing: possible Nitrogen (N)
deficiency. Poor growth: possible
Phosphorous (P) deficiency. Poor
flowering, spotting or curled leaves, or
weak roots or stems: possible Potassium
(K) deficiency.
Plants are healthy and appropriate for site
conditions
Inadequate soil
nutrients and
structure
In the fall, return leaf fall and shredded
woody materials from the landscape to the
site when possible
Soil providing plant nutrients and structure
Excessive vegetation
growth
Grass becomes excessively tall (greater
than 10 inches); nuisance weeds and other
vegetation start to take over.
Healthy turf- “grasscycle” (mulch-mow or
leave the clippings) to build turf health
Weeds Preventive maintenance Avoid use of pesticides (bug and weed
killers), like “weed & feed,” which damage
the soil
Fertilizer needed Where fertilization is needed (mainly turf
and annual flower beds), a moderate
fertilization program should be used which
relies on compost, natural fertilizers or
slow-release synthetic balanced fertilizers
Integrated Pest Management (IPM)
protocols for fertilization followed
Bare spots Bare spots on soil No bare spots, area covered with
vegetation or mulch mixed into the
underlying soil.
Compaction Poor infiltration due to soil compaction
To remediate compaction, aerate
soil, till to at least 8-inch depth, or
further amend soil with compost and
re-till
If areas are turf, aerate compacted
areas and top dress them with 1/4 to
1/2 inch of compost to renovate them
If drainage is still slow, consider
investigating alternative causes (e.g.,
high wet season groundwater levels,
low permeability soils)
Also consider site use and protection
from compacting activities
No soil compaction
Poor infiltration Soils become waterlogged, do not appear
to be infiltrating.
Facility infiltrating properly
Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow
entering area, channelization of runoff)
identified and damaged area stabilized
(regrade, rock, vegetation, erosion control
matting).For deep channels or cuts (over 3
inches in ponding depth), temporary
erosion control measures in place until
permanent repairs can be made
Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is
healthy with a generally good appearance.
Healthy vegetation. Unhealthy plants
removed/replaced. Appropriate vegetation
planted in terms of exposure, soil and soil
moisture.
Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer
to current County noxious weed list).
No noxious weeds present.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
15
11. FIGURES
FIGURE 1 – TIR WORKSHEET
FIGURE 2 – VICINITY MAP
FIGURE 3 – STORM DRAINAGE AS-BUILT
FIGURE 4 – EXISTING CONDITIONS
FIGURE 5 - NEW + REPLACED IMPERVIOUS AREAS
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2022 City of Renton Surface Water Design Manual 6/22/2022
8-A-1
REFERENCE 8-A
TECHNICAL INFORMATION REPORT (TIR)
WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner _____________________________
Phone ___________________________________
Address __________________________________
_________________________________________
Project Engineer ___________________________
Company _________________________________
Phone ___________________________________
Project Name __________________________
CED Permit # ________________________
Location Township ________________
Range __________________
Section _________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Land Use (e.g., Subdivision / Short Subd.)
Building (e.g., M/F / Commercial / SFR)
Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline
Management
Structural
Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
(check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
__________________
__________________
__________________
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
__________________
__________________
__________________
FIGURE 1: TIR WORKSHEET
Renton School District
attn: Alisha Smothers
(425) 531-2577
7812 South 124th Street
Seattle, WA 98178
Sascha Eastman
Jacobson Consulting Engineers
(206) 426-2600
Renton Park ES School -
ADA Improvements
16828 128th Ave SE
Renton, WA 98058
23N
5E
28
Civil Construction Permit
N/A
03/03/2023
04/14/2023
03/03/2023
04/14/2023
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: _______________________
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: SWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: _____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
FIGURE 1: TIR WORKSHEET
N/A
N/A
Soos Creek
N/A
Lower Cedar River and Soos Creek
>2,000 sf; Stormwater BMPs (Utilize Ex Bioswales)
N/A
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-3
Part 10 SOILS
Soil Type
______________________
______________________
______________________
______________________
Slopes
________________________
________________________
________________________
________________________
Erosion Potential
_________________________
_________________________
_________________________
_________________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 9 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Standard: _______________________________
or Exemption Number: ____________
Conveyance System Spill containment located at: _____________________________
Erosion and Sediment Control /
Construction Stormwater Pollution
Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Ur 0% - 2%Low
N/A
Parking Lot Curb Island and NW Corner Bioswales
FIGURE 1: TIR WORKSHEET
< 5,000 SF
TBD
TBD
TBD
1
N/A
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
On-site BMPs Describe:
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
FIGURE 1: TIR WORKSHEET
< 5,000 SF
Bioswales in Curb Island and NW Corner of Site
N/A
N/A
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed
BMPs/Facilities
Maintain Protective BMPs / Manage
Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure
operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Description Water Quality Description On-site BMPs Description
Detention
Infiltration
Regional
Facility
Shared
Facility
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
Vegetated
Flowpath
Wetpool
Filtration
Oil Control
Spill Control
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
Full Dispersion
Full Infiltration
Limited Infiltration
Rain Gardens
Bioretention
Permeable
Pavement
Basic Dispersion
Soil Amendment
Perforated Pipe
Connection
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
FIGURE 1: TIR WORKSHEET
N/A N/A
N/A
Bioswales
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4′ High
Structural on Steep Slope
Other _______________________________
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were
incorporated into this worksheet and the attached Technical Information Report. To the best of my
knowledge the information provided here is accurate.
____________________________________________________________________________________
Signed/Date
FIGURE 1: TIR WORKSHEET
N/A N/A
04/14/2023
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 2: VICINITY MAP
SCALE: NTS
206.426.2600
Renton
Park
Project Sites
Project Site
FIGURE 3: STORM DRAINAGE AS-BUILTNOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALE
FIGURE 4: EXISTING CONDITIONSNOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALE
NOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALEFIGURE 5: NEW + REPLACED IMPERVIOUS AREAS
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
16
12. APPENDICES
APPENDIX A – BOND QUANTITY WORKSHEET
APPENDIX B – STORMWATER POLLUTION PREVENTION PLAN (SWPPP)
APPENDIX C – ENGINEERING CALCULATIONS
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
17
APPENDIX A
BOND QUANTITY WORKSHEET
Page 1 of 15
Ref 8-H Bond Quantity Worksheet INSTRUCTIONS
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
BOND QUANTITY WORKSHEET INSTRUCTIONS
1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200
This worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial
submittal to project close-out approval.
Submit this workbook, in its entirety, as follows:
•(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for civil construction permit submittal. Hard copies are to be included as part
of the Technical Information Report (TIR).
•(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for final close-out submittal.
The following forms are to be completed by the engineer/developer/applicant as applicable to the project:
Section I: Project Information
•This section includes all pertinent information for the project
•This section must be completed in its entirety
•Information from this section auto-populates to all other relevant areas of the workbook
Section II: Bond Quantities Worksheets
•Section II contains a separate spreadsheet TAB for each of the following specialties:
•Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC))
•Section II.b TRANSPORTATION (Street and Site Improvements)
•Section II.c DRAINAGE (Drainage and Stormwater Facilities):
•Section II.d WATER - ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON
•Section II.e SANITARY SEWER - ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON
•Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right-of-Way (ROW), Future Public Improvements and Private
Improvements.
•Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the
form. Stormwater facilities (public and private) are required to be included in the bond amount.
•The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the
project with the exception of the maintenance period reduction.
•Excel will auto-calculate and auto-populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need
completing.
•Additional items not included in the lists can be added under the "write-in" sections. Provide a complete description, cost estimate and unit of measure
for each write-in item.
•All unit prices include labor, equipment, materials, overhead, profit, and taxes.
The Bond Worksheet form will auto-calculate and auto-populate from the information provided in Section I and Section II.
Section III. Bond Worksheet
•This section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close-out
submittals to release the permit bond on a project.
Page 2 of 15
Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
PROJECT INFORMATION
1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200
Date Prepared: 11/8/2022 Project Phase 1 FOR APPROVAL
Prepared by:Engineer Stamp Required
(all cost estimates must have original wet stamp and signature)Name:Alan Jacobson
PE Registration No:43667
Firm Name:Jacobson Consulting Engineers
Firm Address:255 S King ST, Suite 800, Seattle, WA 98104
Phone No.(206) 426-2600
Email Address:alan@jacobsonengineers.com
Project Location and Description Project Owner Information
Project Name: Honey Dew ES - Saftey Upgrades Project Owner:Alisha Smothers c/o Rent School District
CED Plan # (LUA):##-######Phone:(206) 531-2577
CED Permit # (C):##-######Address: 7812 South 124th Street
Site Address:16828 128th Ave SE Seattle, WA 98178-4830
Street Intersection:128th Ave SE & SE 168th Street Addt'l Project Owner:Additional Project Owner
Parcel #(s):282305-9084 Phone:Phone
Abbreviated Legal
Description:
W 1/2 OF NE 1/4 OF SE 1/4 & W 45 FT OF E 1/2 OF NE 1/4 OF SE 1/4
LESS S 724FT THOF LESS CO RD Address: Address
City, State, Zip
Clearing and Grading Utility Providers
Clearing and grading greater than or equal to 5,000 board feet of timber?
Yes/No:NO Water Service Provided by:CITY OF RENTON
If Yes, Provide Forest Practice Permit #:N/A Sewer Service Provided by: CITY OF RENTON
Page 3 of 15
Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
Estimated Civil Construction Permit - Construction Costs2
As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance.
Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees.
Water A $-
Wastewater (Sanitary Sewer)B $-
Stormwater (Drainage)C $3,517.70
Roadway (Erosion Control + Transportation)D $347,410.64
Total Estimated Construction Costs E
A + B + C + D $350,928.34
1 Select the current project status/phase from the following options:
For Approval - Preliminary Data Enclosed, pending approval from the City;
For Construction - Estimated Data Enclosed, Plans have been approved for contruction by the City;
Project Closeout - Final Costs and Quantities Enclosed for Project Close-out Submittal
2 All prices include labor, equipment, materials, overhead, profit, and taxes. City of Renton Sales Tax is:10.1%
Page 4 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR EROSION & SEDIMENT CONTROL
CED Permit #:##-######
Description No.
Unit (A)
Reference #Price Unit Quantity Cost
Backfill & compaction-embankment ESC-1 $7.50 CY
Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 $90.00 Each
Catch Basin Protection ESC-3 $145.00 Each 4 580.00
Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)$110.00 CY
Ditching ESC-5 $10.50 CY
Excavation-bulk ESC-6 $2.30 CY
Fence, silt ESC-7 SWDM 5.4.3.1 $5.00 LF
Fence, Temporary (NGPE)ESC-8 $1.75 LF 500 875.00
Geotextile Fabric ESC-9 $3.00 SY
Hay Bale Silt Trap ESC-10 $0.60 Each
Hydroseeding ESC-11 SWDM 5.4.2.4 $0.90 SY
Interceptor Swale / Dike ESC-12 $1.15 LF
Jute Mesh ESC-13 SWDM 5.4.2.2 $4.00 SY
Level Spreader ESC-14 $2.00 LF
Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 $2.90 SY
Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 $2.30 SY
Piping, temporary, CPP, 6"ESC-17 $13.75 LF
Piping, temporary, CPP, 8"ESC-18 $16.00 LF
Piping, temporary, CPP, 12"ESC-19 $20.50 LF
Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 $4.60 SY
Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)$51.00 CY
Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 $2,050.00 Each
Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 $3,675.00 Each
Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 $2,525.00 Each
Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 $22.00 LF
Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 $80.00 LF
Seeding, by hand ESC-27 SWDM 5.4.2.4 $1.15 SY 20 23.00
Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 $9.20 SY
Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 $11.50 SY
TESC Supervisor ESC-30 $125.00 HR 8 1,000.00
Water truck, dust control ESC-31 SWDM 5.4.7 $160.00 HR
WRITE-IN-ITEMS Unit
Reference #Price Unit Quantity Cost
Straw Wattles SWDM D.2.1.2.5 $4.00 LF 1720 6,880.00
EROSION/SEDIMENT SUBTOTAL:9,358.00
SALES TAX @ 10.1%945.16
EROSION/SEDIMENT TOTAL:10,303.16
(A)
Page 5 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
GENERAL ITEMS
Backfill & Compaction- embankment GI-1 $7.00 CY
Backfill & Compaction- trench GI-2 $10.25 CY
Clear/Remove Brush, by hand (SY)GI-3 $1.15 SY
Bollards - fixed GI-4 $275.00 Each 9 2,475.00
Bollards - removable GI-5 $520.00 Each 2 1,040.00
Clearing/Grubbing/Tree Removal GI-6 $11,475.00 Acre
Excavation - bulk GI-7 $2.30 CY 65 149.50
Excavation - Trench GI-8 $5.75 CY
Fencing, cedar, 6' high GI-9 $23.00 LF
Fencing, chain link, 4'GI-10 $44.00 LF
Fencing, chain link, vinyl coated, 6' high GI-11 $23.00 LF
Fencing, chain link, gate, vinyl coated, 20' GI-12 $1,600.00 Each
Fill & compact - common barrow GI-13 $28.75 CY 20 575.00
Fill & compact - gravel base GI-14 $31.00 CY
Fill & compact - screened topsoil GI-15 $44.75 CY
Gabion, 12" deep, stone filled mesh GI-16 $74.50 SY
Gabion, 18" deep, stone filled mesh GI-17 $103.25 SY
Gabion, 36" deep, stone filled mesh GI-18 $172.00 SY
Grading, fine, by hand GI-19 $2.90 SY 495 1,435.50
Grading, fine, with grader GI-20 $2.30 SY 495 1,138.50
Monuments, 3' Long GI-21 $1,025.00 Each
Sensitive Areas Sign GI-22 $8.00 Each
Sodding, 1" deep, sloped ground GI-23 $9.25 SY
Surveying, line & grade GI-24 $975.00 Day
Surveying, lot location/lines GI-25 $2,050.00 Acre
Topsoil Type A (imported)GI-26 $32.75 CY
Traffic control crew ( 2 flaggers )GI-27 $137.75 HR
Trail, 4" chipped wood GI-28 $9.15 SY
Trail, 4" crushed cinder GI-29 $10.25 SY
Trail, 4" top course GI-30 $13.75 SY
Conduit, 2"GI-31 $5.75 LF
Wall, retaining, concrete GI-32 $63.00 SF
Wall, rockery GI-33 $17.25 SF
SUBTOTAL THIS PAGE:6,813.50
(B)(C)(D)(E)
Page 6 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
ROAD IMPROVEMENT/PAVEMENT/SURFACING
AC Grinding, 4' wide machine < 1000sy RI-1 $34.50 SY
AC Grinding, 4' wide machine 1000-2000sy RI-2 $18.25 SY
AC Grinding, 4' wide machine > 2000sy RI-3 $11.50 SY
AC Removal/Disposal RI-4 $40.00 SY 160 6,400.00
Barricade, Type III ( Permanent )RI-5 $64.25 LF
Guard Rail RI-6 $34.50 LF
Curb & Gutter, rolled RI-7 $19.50 LF
Curb & Gutter, vertical RI-8 $14.25 LF 270 3,847.50
Curb and Gutter, demolition and disposal RI-9 $20.50 LF
Curb, extruded asphalt RI-10 $6.25 LF
Curb, extruded concrete RI-11 $8.00 LF
Sawcut, asphalt, 3" depth RI-12 $3.00 LF 215 645.00
Sawcut, concrete, per 1" depth RI-13 $5.00 LF 95 475.00
Sealant, asphalt RI-14 $2.25 LF 215 483.75
Shoulder, gravel, 4" thick RI-15 $17.25 SY
Sidewalk, 4" thick RI-16 $43.50 SY 2780 120,930.00
Sidewalk, 4" thick, demolition and disposal RI-17 $37.00 SY 2790 103,230.00
Sidewalk, 5" thick RI-18 $47.00 SY 1230 57,810.00
Sidewalk, 5" thick, demolition and disposal RI-19 $46.00 SY
Sign, Handicap RI-20 $97.00 Each 4 388.00
Striping, per stall RI-21 $8.00 Each 7 56.00
Striping, thermoplastic, ( for crosswalk )RI-22 $3.50 SF
Striping, 4" reflectorized line RI-23 $0.55 LF
Additional 2.5" Crushed Surfacing RI-24 $4.15 SY
HMA 1/2" Overlay 1.5" RI-25 $16.00 SY
HMA 1/2" Overlay 2"RI-26 $20.75 SY
HMA Road, 2", 4" rock, First 2500 SY RI-27 $32.25 SY
HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 $24.00 SY
HMA Road, 4", 6" rock, First 2500 SY RI-29 $51.75 SY
HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 $42.50 SY
HMA Road, 4", 4.5" ATB RI-31 $43.50 SY
Gravel Road, 4" rock, First 2500 SY RI-32 $17.25 SY
Gravel Road, 4" rock, Qty. over 2500 SY RI-33 $11.50 SY
Thickened Edge RI-34 $10.00 LF
SUBTOTAL THIS PAGE:294,265.25
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 7 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
PARKING LOT SURFACING No.
2" AC, 2" top course rock & 4" borrow PL-1 $24.00 SY 32 768.00
2" AC, 1.5" top course & 2.5" base course PL-2 $32.00 SY
4" select borrow PL-3 $5.75 SY
1.5" top course rock & 2.5" base course PL-4 $16.00 SY
SUBTOTAL PARKING LOT SURFACING:768.00
(B)(C)(D)(E)
LANDSCAPING & VEGETATION No.
Street Trees LA-1
Median Landscaping LA-2
Right-of-Way Landscaping LA-3
Wetland Landscaping LA-4
SUBTOTAL LANDSCAPING & VEGETATION:
(B)(C)(D)(E)
TRAFFIC & LIGHTING No.
Signs TR-1
Street Light System ( # of Poles)TR-2
Traffic Signal TR-3
Traffic Signal Modification TR-4
SUBTOTAL TRAFFIC & LIGHTING:
(B)(C)(D)(E)
WRITE-IN-ITEMS
Sealcoat Parking Lot WI-1 $0.85 SF 3925 3,336.25
Wheel Stops WI-2 $250.00 EA 4 1,000.00
SUBTOTAL WRITE-IN ITEMS:4,336.25
STREET AND SITE IMPROVEMENTS SUBTOTAL:306,183.00
SALES TAX @ 10.1%30,924.48
STREET AND SITE IMPROVEMENTS TOTAL:337,107.48
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 8 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.)
Access Road, R/D D-1 $30.00 SY
* (CBs include frame and lid)
Beehive D-2 $103.00 Each
Through-curb Inlet Framework D-3 $460.00 Each
CB Type I D-4 $1,725.00 Each 1 1,725.00
CB Type IL D-5 $2,000.00 Each
CB Type II, 48" diameter D-6 $3,500.00 Each
for additional depth over 4' D-7 $550.00 FT
CB Type II, 54" diameter D-8 $4,075.00 Each
for additional depth over 4'D-9 $570.00 FT
CB Type II, 60" diameter D-10 $4,225.00 Each
for additional depth over 4'D-11 $690.00 FT
CB Type II, 72" diameter D-12 $6,900.00 Each
for additional depth over 4'D-13 $975.00 FT
CB Type II, 96" diameter D-14 $16,000.00 Each
for additional depth over 4'D-15 $1,050.00 FT
Trash Rack, 12"D-16 $400.00 Each
Trash Rack, 15"D-17 $470.00 Each
Trash Rack, 18"D-18 $550.00 Each
Trash Rack, 21"D-19 $630.00 Each
Cleanout, PVC, 4"D-20 $170.00 Each
Cleanout, PVC, 6"D-21 $195.00 Each
Cleanout, PVC, 8"D-22 $230.00 Each
Culvert, PVC, 4" D-23 $11.50 LF
Culvert, PVC, 6" D-24 $15.00 LF
Culvert, PVC, 8" D-25 $17.00 LF
Culvert, PVC, 12" D-26 $26.00 LF
Culvert, PVC, 15" D-27 $40.00 LF
Culvert, PVC, 18" D-28 $47.00 LF
Culvert, PVC, 24"D-29 $65.00 LF
Culvert, PVC, 30" D-30 $90.00 LF
Culvert, PVC, 36" D-31 $150.00 LF
Culvert, CMP, 8"D-32 $22.00 LF
Culvert, CMP, 12"D-33 $33.00 LF
SUBTOTAL THIS PAGE:1,725.00
(B)(C)(D)(E)
Page 9 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
DRAINAGE (Continued)
Culvert, CMP, 15"D-34 $40.00 LF
Culvert, CMP, 18"D-35 $47.00 LF
Culvert, CMP, 24"D-36 $64.00 LF
Culvert, CMP, 30"D-37 $90.00 LF
Culvert, CMP, 36"D-38 $150.00 LF
Culvert, CMP, 48"D-39 $218.00 LF
Culvert, CMP, 60"D-40 $310.00 LF
Culvert, CMP, 72"D-41 $400.00 LF
Culvert, Concrete, 8"D-42 $48.00 LF
Culvert, Concrete, 12"D-43 $55.00 LF
Culvert, Concrete, 15"D-44 $89.00 LF
Culvert, Concrete, 18"D-45 $100.00 LF
Culvert, Concrete, 24"D-46 $120.00 LF
Culvert, Concrete, 30"D-47 $145.00 LF
Culvert, Concrete, 36"D-48 $175.00 LF
Culvert, Concrete, 42"D-49 $200.00 LF
Culvert, Concrete, 48"D-50 $235.00 LF
Culvert, CPE Triple Wall, 6" D-51 $16.00 LF
Culvert, CPE Triple Wall, 8" D-52 $18.00 LF
Culvert, CPE Triple Wall, 12" D-53 $27.00 LF
Culvert, CPE Triple Wall, 15" D-54 $40.00 LF
Culvert, CPE Triple Wall, 18" D-55 $47.00 LF
Culvert, CPE Triple Wall, 24"D-56 $64.00 LF
Culvert, CPE Triple Wall, 30" D-57 $90.00 LF
Culvert, CPE Triple Wall, 36" D-58 $149.00 LF
Culvert, LCPE, 6"D-59 $69.00 LF
Culvert, LCPE, 8"D-60 $83.00 LF
Culvert, LCPE, 12"D-61 $96.00 LF
Culvert, LCPE, 15"D-62 $110.00 LF
Culvert, LCPE, 18"D-63 $124.00 LF
Culvert, LCPE, 24"D-64 $138.00 LF
Culvert, LCPE, 30"D-65 $151.00 LF
Culvert, LCPE, 36"D-66 $165.00 LF
Culvert, LCPE, 48"D-67 $179.00 LF
Culvert, LCPE, 54"D-68 $193.00 LF
SUBTOTAL THIS PAGE:
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 10 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
DRAINAGE (Continued)
Culvert, LCPE, 60"D-69 $206.00 LF
Culvert, LCPE, 72"D-70 $220.00 LF
Culvert, HDPE, 6"D-71 $48.00 LF
Culvert, HDPE, 8"D-72 $60.00 LF
Culvert, HDPE, 12"D-73 $85.00 LF
Culvert, HDPE, 15"D-74 $122.00 LF
Culvert, HDPE, 18"D-75 $158.00 LF
Culvert, HDPE, 24"D-76 $254.00 LF
Culvert, HDPE, 30"D-77 $317.00 LF
Culvert, HDPE, 36"D-78 $380.00 LF
Culvert, HDPE, 48"D-79 $443.00 LF
Culvert, HDPE, 54"D-80 $506.00 LF
Culvert, HDPE, 60"D-81 $570.00 LF
Culvert, HDPE, 72"D-82 $632.00 LF
Pipe, Polypropylene, 6"D-83 $96.00 LF
Pipe, Polypropylene, 8"D-84 $100.00 LF
Pipe, Polypropylene, 12"D-85 $100.00 LF
Pipe, Polypropylene, 15"D-86 $103.00 LF
Pipe, Polypropylene, 18"D-87 $106.00 LF
Pipe, Polypropylene, 24"D-88 $119.00 LF
Pipe, Polypropylene, 30"D-89 $136.00 LF
Pipe, Polypropylene, 36"D-90 $185.00 LF
Pipe, Polypropylene, 48"D-91 $260.00 LF
Pipe, Polypropylene, 54"D-92 $381.00 LF
Pipe, Polypropylene, 60"D-93 $504.00 LF
Pipe, Polypropylene, 72"D-94 $625.00 LF
Culvert, DI, 6"D-95 $70.00 LF 21 1,470.00
Culvert, DI, 8"D-96 $101.00 LF
Culvert, DI, 12"D-97 $121.00 LF
Culvert, DI, 15"D-98 $148.00 LF
Culvert, DI, 18"D-99 $175.00 LF
Culvert, DI, 24"D-100 $200.00 LF
Culvert, DI, 30"D-101 $227.00 LF
Culvert, DI, 36"D-102 $252.00 LF
Culvert, DI, 48"D-103 $279.00 LF
Culvert, DI, 54"D-104 $305.00 LF
Culvert, DI, 60"D-105 $331.00 LF
Culvert, DI, 72"D-106 $357.00 LF
SUBTOTAL THIS PAGE:1,470.00
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 11 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
Specialty Drainage Items
Ditching SD-1 $10.90 CY
Flow Dispersal Trench (1,436 base+)SD-3 $32.00 LF
French Drain (3' depth)SD-4 $30.00 LF
Geotextile, laid in trench, polypropylene SD-5 $3.40 SY
Mid-tank Access Riser, 48" dia, 6' deep SD-6 $2,300.00 Each
Pond Overflow Spillway SD-7 $18.25 SY
Restrictor/Oil Separator, 12"SD-8 $1,320.00 Each
Restrictor/Oil Separator, 15"SD-9 $1,550.00 Each
Restrictor/Oil Separator, 18"SD-10 $1,950.00 Each
Riprap, placed SD-11 $48.20 CY
Tank End Reducer (36" diameter)SD-12 $1,375.00 Each
Infiltration pond testing SD-13 $143.00 HR
Permeable Pavement SD-14
Permeable Concrete Sidewalk SD-15
Culvert, Box __ ft x __ ft SD-16
SUBTOTAL SPECIALTY DRAINAGE ITEMS:
(B)(C)(D)(E)
STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)
Detention Pond SF-1 Each
Detention Tank SF-2 Each
Detention Vault SF-3 Each
Infiltration Pond SF-4 Each
Infiltration Tank SF-5 Each
Infiltration Vault SF-6 Each
Infiltration Trenches SF-7 Each
Basic Biofiltration Swale SF-8 Each
Wet Biofiltration Swale SF-9 Each
Wetpond SF-10 Each
Wetvault SF-11 Each
Sand Filter SF-12 Each
Sand Filter Vault SF-13 Each
Linear Sand Filter SF-14 Each
Proprietary Facility SF-15 Each
Bioretention Facility SF-16 Each
SUBTOTAL STORMWATER FACILITIES:
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 12 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)
WI-1
WI-2
WI-3
WI-4
WI-5
WI-6
WI-7
WI-8
WI-9
WI-10
WI-11
WI-12
WI-13
WI-14
WI-15
SUBTOTAL WRITE-IN ITEMS:
DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:3,195.00
SALES TAX @ 10.1%322.70
DRAINAGE AND STORMWATER FACILITIES TOTAL:3,517.70
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Page 13 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.d WATER
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR WATER
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Connection to Existing Watermain W-1 $3,400.00 Each
Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 $58.00 LF
Ductile Iron Watermain, CL 52, 6 Inch Diameter W-3 $65.00 LF
Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 $75.00 LF
Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 $80.00 LF
Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 $145.00 LF
Gate Valve, 4 inch Diameter W-7 $1,225.00 Each
Gate Valve, 6 inch Diameter W-8 $1,350.00 Each
Gate Valve, 8 Inch Diameter W-9 $1,550.00 Each
Gate Valve, 10 Inch Diameter W-10 $2,100.00 Each
Gate Valve, 12 Inch Diameter W-11 $2,500.00 Each
Fire Hydrant Assembly W-12 $5,000.00 Each
Permanent Blow-Off Assembly W-13 $1,950.00 Each
Air-Vac Assembly, 2-Inch Diameter W-14 $3,050.00 Each
Air-Vac Assembly, 1-Inch Diameter W-15 $1,725.00 Each
Compound Meter Assembly 3-inch Diameter W-16 $9,200.00 Each
Compound Meter Assembly 4-inch Diameter W-17 $10,500.00 Each
Compound Meter Assembly 6-inch Diameter W-18 $11,500.00 Each
Pressure Reducing Valve Station 8-inch to 10-inch W-19 $23,000.00 Each
WATER SUBTOTAL:
SALES TAX @ 10.1%
WATER TOTAL:
(B)(C)(D)(E)
Page 14 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR SANITARY SEWER
CED Permit #:##-######
Existing Future Public Private Quantity Remaining
(Bond Reduction)Right-of-Way Improvements Improvements
(B)(C)(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Clean Outs SS-1 $1,150.00 Each
Grease Interceptor, 500 gallon SS-2 $9,200.00 Each
Grease Interceptor, 1000 gallon SS-3 $11,500.00 Each
Grease Interceptor, 1500 gallon SS-4 $17,200.00 Each
Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 $92.00 LF
Side Sewer Pipe, PVC. 6 Inch Diameter SS-6 $110.00 LF
Sewer Pipe, PVC, 8 inch Diameter SS-7 $120.00 LF
Sewer Pipe, PVC, 12 Inch Diameter SS-8 $144.00 LF
Sewer Pipe, DI, 8 inch Diameter SS-9 $130.00 LF
Sewer Pipe, DI, 12 Inch Diameter SS-10 $150.00 LF
Manhole, 48 Inch Diameter SS-11 $6,900.00 Each
Manhole, 54 Inch Diameter SS-13 $6,800.00 Each
Manhole, 60 Inch Diameter SS-15 $7,600.00 Each
Manhole, 72 Inch Diameter SS-17 $10,600.00 Each
Manhole, 96 Inch Diameter SS-19 $16,000.00 Each
Pipe, C-900, 12 Inch Diameter SS-21 $205.00 LF
Outside Drop SS-24 $1,700.00 LS
Inside Drop SS-25 $1,150.00 LS
Sewer Pipe, PVC, ____ Inch Diameter SS-26
Lift Station (Entire System)SS-27 LS
SANITARY SEWER SUBTOTAL:
SALES TAX @ 10.1%
SANITARY SEWER TOTAL:
(B)(C)(D)(E)
Page 15 of 15
Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET
Unit Prices Updated: 01/07/2022
Version: 01/07/2022
Printed 4/13/2023
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
BOND CALCULATIONS
1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200
Date:11/8/2022
Prepared by:Project Information
Name:Alan Jacobson Project Name: Honey Dew ES - Saftey Upgrades
PE Registration No:43667 CED Plan # (LUA):##-######
Firm Name:Jacobson Consulting Engineers CED Permit # (C):##-######
Firm Address:255 S King ST, Suite 800, Seattle, WA 98104 Site Address:16828 128th Ave SE
Phone No.(206) 426-2600 Parcel #(s):282305-9084
Email Address:alan@jacobsonengineers.com Project Phase: FOR APPROVAL
CONSTRUCTION BOND AMOUNT */**
(prior to permit issuance)
MAINTENANCE BOND */**
(after final acceptance of construction)
Site Restoration/Erosion Sediment Control Subtotal (a)$10,303.16
Existing Right-of-Way Improvements Subtotal (b)$-(b)$-
Future Public Improvements Subtotal (c)$-
Stormwater & Drainage Facilities (Public & Private) Subtotal (d)$3,517.70 (d)$3,517.70
Bond Reduction: Existing Right-of-Way Improvements (Quantity
Remaining)2 (e)$-
Bond Reduction: Stormwater & Drainage Facilities (Quantity
Remaining)2 (f)$-
Site Restoration P
(a) x 100%$10,303.16
Existing Right-of-Way and Storm Drainage Improvements R
((b x 150%) + (d x 100%))$3,517.70
Maintenance Bond EST1
((b) + (c) + (d)) x 20%$703.54
Bond Reduction2 S
(e) x 150% + (f) x 100%$-
Construction Permit Bond Amount 3 T
(P +R - S)
$13,820.85
Minimum Bond Amount is $10,000.00
1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering.
2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will
cover all remaining items to be constructed.
3 Required Bond Amounts are subject to review and modification by Development Engineering.
* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.
** Note: All prices include labor, equipment, materials, overhead, profit, and taxes.
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
18
APPENDIX B
STORMWATER POLLUTION PREVENTION PLAN (SWPPP)
Construction Stormwater General Permit (CSWGP)
Stormwater Pollution Prevention Plan
(SWPPP)
for
Renton Park Elementary School – ADA Improvements
Prepared for:
Renton School District and Project Contractor (TBD)
Permittee / Owner Developer Operator / Contractor
Renton School District Renton School District TBD
16828 128th Ave SE, Renton, WA 98058
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Sascha Eastman Jacobson Consulting
Engineers
Office: (206) 426-2600
SWPPP Preparation Date
03 / 03 / 2023
Project Construction Dates
Activity / Phase Start Date End Date
Sitework Construction 06 / 2023 08 / 2023
Page | 1
Table of Contents
1. Project Information .......................................................................................................................... 4
1.1 Existing Conditions ......................................................................................................................... 4
1.2 Proposed Construction Activities .................................................................................................... 5
2. Construction Stormwater Best Management Practices (BMPs) .................................................... 7
2.1 The 13 Elements ............................................................................................................................. 7
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................................... 7
2.1.2 Element 2: Establish Construction Access ............................................................................... 8
2.1.3 Element 3: Control Flow Rates ................................................................................................. 9
2.1.4 Element 4: Install Sediment Controls ...................................................................................... 10
2.1.5 Element 5: Stabilize Soils ........................................................................................................11
2.1.6 Element 6: Protect Slopes........................................................................................................12
2.1.7 Element 7: Protect Drain Inlets ................................................................................................13
2.1.8 Element 8: Stabilize Channels and Outlets .............................................................................14
2.1.9 Element 9: Control Pollutants ..................................................................................................15
2.1.10 Element 10: Control Dewatering .............................................................................................18
2.1.11 Element 11: Maintain BMPs ....................................................................................................19
2.1.12 Element 12: Manage the Project .............................................................................................20
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs ....................................................23
3. Pollution Prevention Team .............................................................................................................24
4. Monitoring and Sampling Requirements ........................................................................................25
4.1 Site Inspection ...............................................................................................................................25
4.2 Stormwater Quality Sampling ........................................................................................................25
4.2.1 Turbidity Sampling ..................................................................................................................25
4.2.2 pH Sampling ...........................................................................................................................28
5. Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies ....................................29
5.1 303(d) Listed Waterbodies .............................................................................................................29
5.2 TMDL Waterbodies .......................................................................................................................29
6. Reporting and Record Keeping ......................................................................................................30
6.1 Record Keeping .............................................................................................................................30
6.1.1 Site Logbook ...........................................................................................................................30
6.1.2 Records Retention ..................................................................................................................30
6.1.3 Updating the SWPPP ..............................................................................................................30
6.2 Reporting .......................................................................................................................................31
6.2.1 Discharge Monitoring Reports .................................................................................................31
6.2.2 Notification of Noncompliance .................................................................................................31
Page | 2
List of Tables
Table 1 – Summary of Site Pollutant Constituents ....................................................................... 5
Table 2 – Pollutants .....................................................................................................................15
Table 3 – pH-Modifying Sources .................................................................................................17
Table 4 – Dewatering BMPs ........................................................................................................18
Table 5 – Management ................................................................................................................20
Table 6 – BMP Implementation Schedule ....................................................................................21
Table 7 – Team Information .........................................................................................................24
Table 8 – Turbidity Sampling Method ..........................................................................................26
Table 9 – pH Sampling Method ...................................................................................................28
List of Appendices
A. Site Map
B. BMP Detail
C. Correspondence – N/A
D. Site Inspection Form
E. Construction Stormwater General Permit (CSWGP) – N/A
F. 303(d) List Waterbodies / TMDL Waterbodies Information – N/A
G. Contaminated Site Information – N/A
H. Engineering Calculations – N/A
Page | 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
Page | 4
1 Project Information
Project/Site Name: Renton Park Elementary School – ADA Improvements
Street/Location: 16828 128th Ave SE
City: Renton State: WA Zip code: 98058
Subdivision: N/A
Receiving waterbody: Lower Cedar River
1.1 Existing Conditions
Renton Park Elementary School is a developed campus consisting of single primary school
building in the middle of the campus, parking and drive areas on the west and north side of
building, hard surface play areas with covered play shelter and natural grass playfield to the
east, and landscaping around the property perimeter and in the parking lots, and south of the
school building. The main building is surrounded by low landscaping and concrete sidewalks.
Storm water from the existing impervious asphalt and sidewalk in the project vicinity drains to a
central landscape island that is developed with an existing grass bioswale that collects the
stormwater and conveys it to the NW corner of the site to another existing grass bioswale, that
treats the stormwater prior to discharging the stormwater to an existing catch basin in 128th Ave
SE at the approximate SE corner of the intersection with SE 168th Street.
Total acreage: 7.8-acres
Disturbed acreage: 0.10-acres
Landscape topography: In general, the site topography of Renton Park Elementary School
in the area of the proposed project work scope is relatively flat at
roughly 2%-4% for existing parking lot and sidewalk.
Drainage patterns: Stormwater from the project site is described above.
Existing Vegetation: The site is already fully developed with grass bioswales in the
existing curb island south of project work area and north of it in the
NW corner of the existing site. Elsewhere it is mostly lawn.
Critical Areas: No critical areas exist on the project parcel.
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the
receiving waterbody: The project eventually discharges to an existing regional stormwater
facility located approximately 3/4 mile downstream, which is not a 303d listed impaired for
water, sediment, and fish tissue.
Page | 5
Table 1 below 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
Oil and Grease Parking Lot Surface Typical concentration
from parking lots
Total Suspended
Solids
Buildings and
Parking Lots
Surface N/A
pH Newly installed
concrete areas
Surface N/A
1.2 Proposed Construction Activities
Description of site development:
The project will occur in the NW corner of the site adjacent to and west of the main entrance to
the school on the north side of the bus and parent drop-off pickup loop. Work consists of
replacing and modifying the existing ADA parking stalls and portion of existing sidewalk from
ADA parking stalls to the school entrance as required to meet accessibility code requirements.
Some additional security improvements are also proposed for the project, that will involve
removing the existing non-traffic rated bollards that near the school building entrance and
replacing with heavy duty traffic rated security bollards. The new bollards will provide security
measures to parents, staff, and students to keep vehicles from “jumping” the curb and driving
onto the sidewalk. To install the new bollards, the existing concrete sidewalk will be sawcut and
removed and replaced as necessary.
Description of construction activities (example: site preparation, demolition, excavation):
Project will consist of site preparation, demolition, and excavation for pavements (asphalt and
concrete).
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
There will be a new Catch Basin and associated storm piping associated with the regrading of
the ADA parking stalls that will connect to the existing catch basin located in the NE corner of
the ADA parking area. Otherwise, the existing drainage courses and systems will be maintained
and protected during construction. The existing bioswales in the south curb island and north of
the project site in the NW corner of the existing site will be utilized as Stormwater BMPs for the
project and will be required to be protected during construction.
Page | 6
Generally, the existing school is surrounded by established public Right-of-Way with its own
drainage systems. Therefore, there are no substantial areas of offsite flow entering the existing
parcel.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
At final stabilization the project areas (parking lot and sidewalks) will include new pavements
(asphalt and concrete) and exposed areas shall be hydroseeded at a minimum at completion of
construction.
Contaminated Site Information:
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
There is no contaminated soil or groundwater conditions known at the project site and therefore
no proposed activities for the cleanup of existing contamination.
Page | 7
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 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, if any, shall be clearly delineated,
both in the field and on the plans. In general, natural vegetation and native topsoil shall be
retained in an undisturbed state to the maximum extent possible. The BMPs relevant to marking
the clearing limits that will be applied for this project include:
List and describe BMPs:
· Preserving Natural Vegetation (BMP C101)
· High-Visibility Fence (BMP C103)
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction.
Page | 8
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. No
additional BMPs are proposed to be installed or placed to establish additional construction
access.
List and describe BMPs:
· N/A
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction.
Page | 9
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. The specific BMPs for flow control that shall be used
on this project include:
Will you construct stormwater retention and/or detention facilities?
No
Will you use permanent infiltration ponds or other low impact development (example: rain
gardens, bio-retention, porous pavement) to control flow during construction?
No
List and describe BMPs:
N/A
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized, and permanent flow control facilities are functioning.
Page | 10
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.
Specific BMPs to be used for controlling sediment on this project include:
List and describe BMPs:
· Inlet Protection (BMP C220)
· Straw Wattles (BMP C235)
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction.
Page | 11
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 are listed below:
List and describe BMPs:
· Temporary and Permanent Seeding (BMP C120)
· Mulching (BMP C121)
· Plastic Covering (BMP C123)
· Dust Control (BMP C140)
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.
Will you construct during the wet season? No
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized.
Page | 12
2.1.6 Element 6: Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes
erosion during construction.
Will steep slopes be present at the site during construction? No
List and describe BMPs:
· N/A
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized.
Page | 13
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 C220) will be implemented for all drainage inlets and culverts that could
potentially be impacted by sediment-laden runoff on and near the project site. All inlets will be
inspected weekly at a minimum and daily during storm events. Inlet protection devices will be
cleaned or replaced when sediment has reached 1/3 capacity or as specified by the product
manufacturer.
List and describe BMPs:
· Inlet Protection (BMP C220)
· Straw Wattles (BMP C235)
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized, and permanent flow control facilities are functioning.
Page | 14
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
discharge point, efforts will be taken to prevent downstream erosion. There are no existing
downstream channels or streams that site will directly discharge stormwater runoff to, therefore
no BMPs are proposed for Element 8.
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.
List and describe BMPs:
N/A
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized, and permanent flow control facilities are functioning.
Page | 15
2.1.9 Element 9: Control Pollutants
The following pollutants are anticipated to be present on-site:
Table 2 – Pollutants
Pollutant (and source, if applicable)
Vehicles and construction equipment
Demolition
Concrete and grout
Sanitary wastewater
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.
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.
· On-site fueling tanks and petroleum product storage containers shall include secondary
containment.
· 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.
Demolition:
· Dust released from demolished sidewalks, buildings, or structures will be controlled
using Dust Control measures (BMP C140).
· Storm drain inlets vulnerable to stormwater discharge carrying dust, soil, or debris will be
protected using Storm Drain Inlet Protection (BMP C220 as described above for Element
7).
· Process water and slurry resulting from sawcutting and surfacing operations will be
prevented from entering the waters of the State by implementing Sawcutting and
Surfacing Pollution Prevention measures (BMP C152).
Page | 16
Concrete and grout:
· Process water and slurry resulting from concrete work will be prevented from entering
the waters of the State by implementing Concrete Handling measures (BMP C151)
Sanitary wastewater:
· Portable sanitation facilities will be firmly secured, regularly maintained, and emptied
when necessary.
List and describe BMPs:
· Dust Control (BMP C140)
· Materials on Hand (BMP C150)
· Concrete Handling (BMP C151)
· Sawcutting and Surfacing Pollution Prevention (BMP C152)
· Material Delivery, Storage, and Containment (BMP C153)
· Concrete Washout Area (BMP C154)
Installation Schedules: BMP’s will be implemented at the beginning of construction and
be inspected and maintained throughout construction until site is
fully stabilized.
Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site?
No
Will wheel wash or tire bath system BMPs be used during construction?
No
List and describe BMPs:
N/A
Installation Schedules: BMP’s will be installed at the beginning of construction and be
inspected and maintained throughout construction until site is fully
stabilized and wheel wash is no longer needed.
Page | 17
Will pH-modifying sources be present on-site?
YES
Table 3 – pH-Modifying Sources
None
X Bulk cement
Cement kiln dust
Fly ash
X Other cementitious materials
X New concrete washing or curing waters
X Waste streams generated from concrete grinding and sawing
Exposed aggregate processes
Dewatering concrete vaults
Concrete pumping and mixer washout waters
Recycled concrete
Other (i.e. calcium lignosulfate) [please describe]
List and describe BMPs:
· Materials on Hand (BMP C150)
· Concrete Handling (BMP C151)
· Sawcutting and Surfacing Pollution Prevention (BMP C152)
· Material Delivery, Storage and Containment (BMP C153)
· Concrete Washout Area (BMP C154)
· Treating and Disposing of High pH Water (BMP C252)
Installation Schedules: BMP’s will be implemented at the beginning of construction and
be inspected and maintained throughout construction as required.
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.
Page | 18
2.1.10 Element 10: Control Dewatering
This project does not propose dewatering and therefore will not be implementing any
dewatering BMPs associated with Element 10.
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)
List and describe BMPs: N/A
Page | 19
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).
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.
Page | 20
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. However, the project site area is less than 1 acre and
therefore a CSWGP (NPDES Permit) will not be required for this project.
· Maintain an updated SWPPP.
o The SWPPP will be updated, maintained, and implemented in accordance with
the City of Renton Standards and the 2022 Renton SWDM.
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
X Design the project to fit the existing topography, soils, and drainage patterns
X Emphasize erosion control rather than sediment control
X Minimize the extent and duration of the area exposed
X Keep runoff velocities low
X Retain sediment on-site
X Thoroughly monitor site and maintain all ESC measures
X Schedule major earthwork during the dry season
Other (please describe)
Page | 21
Table 6 – BMP Implementation Schedule
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
Page | 22
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
Page | 23
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs
The project will be implementing BMP T5.13 for Post-Construction Soil Quality and Depth. To
comply with the requirements of this BMP, the duff layer and native topsoil will be stockpiled and
retained on site during grading activities to be reapplied for use in post-construction soils prior to
planting. Existing vegetation or landscaped areas will be protected during construction (BMP
C101 and C103). Topsoil will be imported as needed to meet BMP T5.13 requirements. Soil
quality and depth will be established at the end of construction to prevent compaction from
heavy machinery.
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3 Pollution Prevention Team
Table 7 – Team Information
Title Name(s) Phone Number
Certified Erosion and
Sediment Control Lead
(CESCL)
TBD
Resident Engineer TBD
Emergency Ecology
Contact
TBD
Emergency Permittee/
Owner Contact
TBD
Non-Emergency Owner
Contact
TBD
Monitoring Personnel TBD
Ecology Regional Office Northwest Regional Office 425-649-7098
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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 logbook. A site logbook 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
· NOTE: The project site area is less than 1 acre and therefore a CSWGP (NPDES
Permit) will not be required for this project.
File a blank form under Appendix D: N/A
The site logbook must be maintained on-site within reasonable access to the site and be made
available upon request to Ecology or the local jurisdiction.
Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See
CSWGP Special Condition S8 and Section 5 of this template.
Complete the following paragraph for sites that discharge to impaired waterbodies for fine
sediment, turbidity, phosphorus, or pH:
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) are indicated on the Site Map (see Appendix A) and in accordance with
the applicable requirements of the CSWGP.
4.2 Stormwater Quality Sampling
4.2.1 Turbidity Sampling N/A
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)
Page | 26
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.
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 logbook.
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.
https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue
· Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima):
(509) 575-2490
· Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant,
Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400
· Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish,
Whatcom): (425) 649-7000
· Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis,
Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300
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 logbook.
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.
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4.2.2 pH Sampling
pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards
poured concrete or recycled concrete over the life of the project). The use of 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
X pH meter
pH test kit
Wide range pH indicator paper
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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?
No
List the impairment(s): N/A
List and describe BMPs: N/A
5.2 TMDL Waterbodies
Waste Load Allocation for CWSGP discharges:
This project site discharges to a regional stormwater facility. The proposed development is not
providing water quality treatment and does not discharge to a TMDL Waterbody.
Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point
of discharge.
Page | 29
6 Reporting and Record Keeping
6.1 Record Keeping
6.1.1 Site Logbook
A site logbook 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 N/A
· Permit Coverage Letter N/A
· SWPPP
· Site Logbook
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.
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6.2 Reporting
6.2.1 Discharge Monitoring Reports
Cumulative soil disturbance is less than one (1) acre or larger; therefore, Discharge
Monitoring Reports (DMRs) will NOT 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 N/A
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.
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Appendix/Glossary
A. Site Map
B. BMP Detail
C. Correspondence - N/A
D. Site Inspection Form
E. Construction Stormwater General Permit (CSWGP) – N/A
F. 303(d) List Waterbodies / TMDL Waterbodies Information – N/A
G. Contaminated Site Information - N/A
H. Engineering Calculations – N/A
Page | 32
Appendix A – Site Map
Vicinity Map
Temporary Erosion and Sediment Control (TESC) Plan
TESC Details
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
VICINITY MAP
SCALE: NTS
206.426.2600
Renton
Park
Project Sites
Project Site
NOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALE
NOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALE
Page | 33
Appendix B – BMP Details
Preserving Natural Vegetation (BMP C101)
High Visibility Fence (BMP C103)
Temporary and Permanent Seeding (BMP C120)
Mulching (BMP C121)
Plastic Covering (BMP C123)
Dust Control (BMP C140)
Materials on Hand (BMP C150)
Concrete Handling (BMP C151)
Sawcutting and Surfacing Pollution Prevention (BMP C152)
Material Delivery, Storage and Containment (BMP C153)
Concrete Washout Area (BMP C154)
Certified Erosion and Sediment Control Lead (BMP C160)
Scheduling (BMP C162)
Storm Drain Inlet Protection (BMP C220)
Straw Wattles (BMP C235)
Construction Stormwater Chemical Treatment (BMP C250)
Construction Stormwater Filtration (BMP C251)
High pH Neutralization Using CO2 (BMP C252)
BMP C101: Preserving Natural Vegetation
Purpose
The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site
disturbance is the single most effective method for reducing erosion. For example, conifers can hold
up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never
reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the
tree can be released slowly to the ground after the storm.
Conditions of Use
Natural vegetation should be preserved on steep slopes, near perennial and intermittent water-
courses or swales, and on building sites in wooded areas.
l As required by local governments.
l Phase construction to preserve natural vegetation on the project site for as long as possible
during the construction period.
Design and Installation Specifications
Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines.
The preservation of individual plants is more difficult because heavy equipment is generally used to
remove unwanted vegetation. The points to remember when attempting to save individual plants
are:
l Is the plant worth saving? Consider the location, species, size, age, vigor, and the work
involved. Local governments may also have ordinances to save natural vegetation and trees.
l Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground
disturbance away from the trees at least as far out as the dripline.
Plants need protection from three kinds of injuries:
l Construction Equipment - This injury can be above or below the ground level. Damage results
from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around
plants to be saved prior to construction can prevent construction equipment injuries.
l Grade Changes - Changing the natural ground level will alter grades, which affects the plant's
ability to obtain the necessary air, water, and minerals. Minor fills usually do not cause prob-
lems although sensitivity between species does vary and should be checked. Trees can typ-
ically tolerate fill of 6 inches or less. For shrubs and other plants, the fill should be less.
When there are major changes in grade, it may become necessary to supply air to the roots of
plants. This can be done by placing a layer of gravel and a tile system over the roots before the
fill is made. The tile system should be laid out on the original grade leading from a dry well
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around the tree trunk. The system should then be covered with small stones to allow air to cir-
culate over the root area.
Lowering the natural ground level can seriously damage trees and shrubs. The highest per-
centage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can
cause serious injury. To protect the roots it may be necessary to terrace the immediate area
around the plants to be saved. If roots are exposed, construction of retaining walls may be
needed to keep the soil in place. Plants can also be preserved by leaving them on an undis-
turbed, gently sloping mound. To increase the chances for survival, it is best to limit grade
changes and other soil disturbances to areas outside the dripline of the plant.
l Excavations - Protect trees and other plants when excavating for drainfields, power, water,
and sewer lines. Where possible, the trenches should be routed around trees and large
shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand
tools or with power augers. If it is not possible to route the trench around plants to be saved,
then the following should be observed:
o Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a
wood dressing like asphalt base paint if roots will be exposed for more than 24-hours.
o Backfill the trench as soon as possible.
o Tunnel beneath root systems as close to the center of the main trunk to preserve most
of the important feeder roots.
Some problems that can be encountered with a few specific trees are:
l Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not
readily adjust to changes in environment and special care should be taken to protect these
trees.
l The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock
is moderate. The danger of windthrow increases where dense stands have been thinned.
Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low
windthrow hazard.
l Cottonwoods, maples, and willows have water-seeking roots. These can cause trouble in
sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions
that other trees would not.
l Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, Sitka
spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause ser-
ious disease problems. Disease can become established through damaged limbs, trunks,
roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect
attack.
Maintenance Standards
Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been
removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be
repaired or replaced immediately and visibility restored.
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If tree roots have been exposed or injured, “prune” cleanly with an appropriate pruning saw or lop-
pers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees
(fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier.
BMP C102: Buffer Zones
Purpose
Creation of an undisturbed area or strip of natural vegetation or an established suitable planting that
will provide a living filter to reduce soil erosion and stormwater runoff velocities.
Conditions of Use
Buffer zones are used along streams, wetlands and other bodies of water that need protection from
erosion and sedimentation. Contractors can use vegetative buffer zone BMPs to protect natural
swales and they can incorporate them into the natural landscaping of an area.
Do not use critical-areas buffer zones as sediment treatment areas. These areas shall remain com-
pletely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow
the use of the expanded area for removal of sediment.
The types of buffer zones can change the level of protection required as shown below:
Designated Critical Area Buffers - buffers that protect Critical Areas, as defined by the Washington
State Growth Management Act, and are established and managed by the local permitting authority.
These should not be disturbed and must protected with sediment control BMPs to prevent impacts.
The local permitting authority may expand the buffer widths temporarily to allow the use of the expan-
ded area for removal of sediment.
Vegetative Buffer Zones - areas that may be identified in undisturbed vegetation areas or managed
vegetation areas that are outside any Designated Critical Area Buffer. They may be utilized to
provide an additional sediment control area and/or reduce runoff velocities. If being used for pre-
servation of natural vegetation, they should be arranged in clumps or strips. They can be used to pro-
tect natural swales and incorporated into the natural landscaping area.
Design and Installation Specifications
l Preserving natural vegetation or plantings in clumps, blocks, or strips is generally the easiest
and most successful method.
l Leave all unstable steep slopes in natural vegetation.
l Mark clearing limits and keep all equipment and construction debris out of the natural areas
and buffer zones. Steel construction fencing is the most effective method to protect sensitive
areas and buffers. Alternatively, wire-backed silt fence on steel posts is marginally effective.
Flagging alone is typically not effective.
l Keep all excavations outside the dripline of trees and shrubs.
l Do not push debris or extra soil into the buffer zone area because it will cause damage by
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N/A
burying and smothering vegetation.
l Vegetative buffer zones for streams, lakes or other waterways shall be established by the
local permitting authority or other state or federal permits or approvals.
Maintenance Standards
Inspect the area frequently to make sure flagging remains in place and the area remains undis-
turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area
that may impede the ability of the vegetation to act as a filter.
BMP C103: High-Visibility Fence
Purpose
High-visibility fencing is intended to:
l Restrict clearing to approved limits.
l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis-
turbed.
l Limit construction traffic to designated construction entrances, exits, or internal roads.
l Protect areas where marking with survey tape may not provide adequate protection.
Conditions of Use
To establish clearing limits plastic, fabric, or metal fence may be used:
l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared.
l As necessary to control vehicle access to and on the site.
Design and Installation Specifications
High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at
least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center
(maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches
with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as
a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The
fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method.
If appropriate install fabric silt fence in accordance with BMP C233: Silt Fence to act as high-visibility
fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of
this BMP.
Metal fences shall be designed and installed according to the manufacturer's specifications.
Metal fences shall be at least 3 feet high and must be highly visible.
Fences shall not be wired or stapled to trees.
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Maintenance Standards
If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and
visibility restored.
BMP C105: Stabilized Construction Access
Purpose
Stabilized construction accesses are established to reduce the amount of sediment transported onto
paved roads outside the project site by vehicles or equipment. This is done by constructing a sta-
bilized pad of quarry spalls at entrances and exits for project sites.
Conditions of Use
Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction
site if paved roads or other paved areas are within 1,000 feet of the site.
For residential subdivision construction sites, provide a stabilized construction access for each res-
idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient
length/width to provide vehicle access/parking, based on lot size and configuration.
On large commercial, highway, and road projects, the designer should include enough extra mater-
ials in the contract to allow for additional stabilized accesses not shown in the initial Construction
SWPPP. It is difficult to determine exactly where access to these projects will take place; additional
materials will enable the contractor to install them where needed.
Design and Installation Specifications
See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the
access shall be reduced to the maximum practicable size when the size or configuration of the site
does not allow the full length (100’).
Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls,
a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con-
crete, cement, or calcium chloride for construction access stabilization because these products raise
pH levels in stormwater and concrete discharge to waters of the State is prohibited.
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 standards listed in Table II-3.2: Stabilized Con-
struction Access Geotextile Standards.
Geotextile Property Required Value
Grab Tensile Strength (ASTM D4751)200 psi min.
Table II-3.2: Stabilized Construction Access
Geotextile Standards
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Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and
to stabilize any areas that have eroded.
Following construction, these areas shall be restored to pre-construction condition or better to pre-
vent future erosion.
Perform street cleaning at the end of each day or more often if necessary.
BMP C120: Temporary and Permanent Seeding
Purpose
Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of
the most effective methods of reducing erosion.
Conditions of Use
Use seeding throughout the project on disturbed areas that have reached final grade or that will
remain unworked for more than 30 days.
The optimum seeding windows for western Washington are April 1 through June 30 and September
1 through October 1.
Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established.
Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket
until 75 percent grass cover is established.
Review all disturbed areas in late August to early September and complete all seeding by the end of
September. Otherwise, vegetation will not establish itself enough to provide more than average pro-
tection.
Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and
transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding.
See BMP C121: Mulching for specifications.
Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta-
bilization means the completion of all soil disturbing activities at the site and the establishment of a
permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement,
riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil
Quality and Depth.
Design and Installation Specifications
General
l Install channels intended for vegetation before starting major earthwork and hydroseed with a
Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control
blankets over the top of hydroseed. Before allowing water to flow in vegetated channels,
establish 75 percent vegetation cover. If vegetated channels cannot be established by seed
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before water flow; install sod in the channel bottom — over top of hydromulch and erosion con-
trol blankets.
l Confirm the installation of all required surface water control measures to prevent seed from
washing away.
l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per-
cent tackifier. See BMP C121: Mulching for specifications.
l Areas that will have seeding only and not landscaping may need compost or meal-based
mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on
the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality
and Depth.
l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up
in contact with the soil surface. This reduces the ability to establish a good stand of grass
quickly. To overcome this, consider increasing seed quantities by up to 50 percent.
l Enhance vegetation establishment by dividing the hydromulch operation into two phases:
o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in
the first lift.
o Phase 2- Install the rest of the mulch and tackifier over the first lift.
Or, enhance vegetation by:
o Installing the mulch, seed, fertilizer, and tackifier in one lift.
o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per
acre.
o Hold straw in place with a standard tackifier.
Both of these approaches will increase cost moderately but will greatly improve and enhance
vegetative establishment. The increased cost may be offset by the reduced need for:
o Irrigation.
o Reapplication of mulch.
o Repair of failed slope surfaces.
This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon-
ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre
minimum).
l Seed may be installed by hand if:
o Temporary and covered by straw, mulch, or topsoil.
o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or
erosion blankets.
l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include
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recommended mixes for both temporary and permanent seeding.
l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per
acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply
the wet area seed mix at a rate of 60 pounds per acre.
l Consult the local suppliers or the local conservation district for their recommendations. The
appropriate mix depends on a variety of factors, including location, exposure, soil type, slope,
and expected foot traffic. Alternative seed mixes approved by the local authority may be used,
depending on the soil type and hydrology of the area.
Common Name Latin Name % Weight % Purity % Germination
Temporary Erosion Control Seed Mix
A standard mix for areas requiring a temporary vegetative cover.
Chewings or
annual blue grass
Festuca rubra var.
commutata or Poa
anna
40 98 90
Perennial rye Lolium perenne 50 98 90
Redtop or colonial
bentgrass
Agrostis alba or
Agrostis tenuis 5 92 85
White dutch clover Trifolium repens 5 98 90
Landscaping Seed Mix
A recommended mix for landscaping seed.
Perennial rye blend Lolium perenne 70 98 90
Chewings and red
fescue blend
Festuca rubra var.
commutata or Fes-
tuca rubra
30 98 90
Low-Growing Turf Seed Mix
A turf seed mix for dry situations where there is no need for watering. This mix requires very little main-
tenance.
Dwarf tall fescue
(several varieties)
Festuca arundin-
acea 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
Bioswale Seed Mix
A seed mix for bioswales and other intermittently wet areas.
Tall or meadow fes-Festuca arundin-75-80 98 90
Table II-3.4: Temporary and Permanent Seed Mixes
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Common Name Latin Name % Weight % Purity % Germination
cue acea or Festuca
elatior
Seaside/Creeping
bentgrass Agrostis palustris 10-15 92 85
Redtop bentgrass Agrostis alba or
Agrostis gigantea 5-10 90 80
Wet Area Seed Mix
A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet-
lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable.
Tall or meadow fes-
cue
Festuca arundin-
acea or Festuca
elatior
60-70 98 90
Seaside/Creeping
bentgrass Agrostis palustris 10-15 98 85
Meadow foxtail Alepocurus praten-
sis 10-15 90 80
Alsike clover Trifolium hybridum 1-6 98 90
Redtop bentgrass Agrostis alba 1-6 92 85
Meadow Seed Mix
A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col-
onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed-
ing should take place in September or very early October in order to obtain adequate establishment prior to
the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending
the soil can reduce the need for clover.
Redtop or Oregon
bentgrass
Agrostis alba or
Agrostis ore-
gonensis
20 92 85
Red fescue Festuca rubra 70 98 90
White dutch clover Trifolium repens 10 98 90
Table II-3.4: Temporary and Permanent Seed Mixes (continued)
Roughening and Rototilling
l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk
slopes before seeding if engineering purposes require compaction. Backblading or smoothing
of slopes greater than 4H:1V is not allowed if they are to be seeded.
l Restoration-based landscape practices require deeper incorporation than that provided by a
simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to
improve long-term permeability, infiltration, and water inflow qualities. At a minimum,
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permanent areas shall use soil amendments to achieve organic matter and permeability per-
formance defined in engineered soil/landscape systems. For systems that are deeper than 8
inches complete the rototilling process in multiple lifts, or prepare the engineered soil system
per specifications and place to achieve the specified depth.
Fertilizers
l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended.
This will prevent the over-application of fertilizer.
l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ-
ing nitrogen, phosphorus, and potassium) in the least water-soluble form.
l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90
pounds per acre. Always use slow-release fertilizers because they are more efficient and
have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit-
ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating.
l There are numerous products available that take the place of chemical fertilizers. These
include several with seaweed extracts that are beneficial to soil microbes and organisms. If
100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be
necessary. Cottonseed meal provides a good source of long-term, slow-release, available
nitrogen.
Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix
l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix
(MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre
with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during
application. Numerous products are available commercially. Most products require 24-36
hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally,
products come in 40-50 pound bags and include all necessary ingredients except for seed and
fertilizer.
l Install products per manufacturer's instructions.
l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation
establishment. Advantages over blankets include:
o BFM and MBFMs do not require surface preparation.
o Helicopters can assist in installing BFM and MBFMs in remote areas.
o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses
for safety.
o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets.
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Maintenance Standards
Reseed any seeded areas that fail to establish at least 75 percent cover (100 percent cover for areas
that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such
as sodding, mulching, nets, or blankets.
l Reseed and protect by mulch any areas that experience erosion after achieving adequate
cover. Reseed and protect by mulch any eroded area.
l Supply seeded areas with adequate moisture, but do not water to the extent that it causes run-
off.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C121: Mulching
Purpose
Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant
establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating
soil temperatures. There are a variety of mulches that can be used. This section discusses only the
most common types of mulch.
Conditions of Use
As a temporary cover measure, mulch should be used:
l For less than 30 days on disturbed areas that require cover.
l At all times for seeded areas, especially during the wet season and during the hot summer
months.
l During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief.
Mulch may be applied at any time of the year and must be refreshed periodically.
For seeded areas, mulch may be made up of 100 percent:
l cottonseed meal;
l fibers made of wood, recycled cellulose, hemp, or kenaf;
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l compost;
l or blends of these.
Tackifier shall be plant-based, such as guar or alpha plantago, or chemical-based such as poly-
acrylamide or polymers.
Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application.
Recycled cellulose may contain polychlorinated biphenyl (PCBs). Ecology recommends that
products should be evaluated for PCBs prior to use.
Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM
shall not be directly applied to water or allowed to enter a water body.
Any mulch or tackifier product used shall be installed per the manufacturer’s instructions.
Design and Installation Specifications
For mulch materials, application rates, and specifications, see Table II-3.6: Mulch Standards and
Guidelines. Consult with the local supplier or the local conservation district for their recom-
mendations. Increase the application rate until the ground is 95% covered (i.e. not visible under the
mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or
other areas highly susceptible to erosion.
Where the option of “Compost” is selected, it should be a coarse compost that meets the size grad-
ations listed in Table II-3.5: Size Gradations of Compost as Mulch Material when tested in accord-
ance with Test Method 02.02-B found in Test Methods for the Examination of Composting and
Compost (Thompson, 2001).
Sieve Size Percent Passing
3"100%
1"90% - 100%
3/4"70% - 100%
1/4"40% - 100%
Table II-3.5: Size Gradations of Compost as Mulch Material
Mulch used within the ordinary high-water mark of surface waters should be selected to minimize
potential flotation of organic matter. Composted organic materials have higher specific gravities
(densities) than straw, wood, or chipped material. Consult the Hydraulic Permit Authority (HPA) for
mulch mixes if applicable.
Maintenance Standards
The thickness of the mulch cover must be maintained.
Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the
erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched.
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Mulch Mater-
ial Guideline Description
Straw
Quality
Standards Air-dried; free from undesirable seed and coarse material.
Application
Rates 2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre
Remarks
Cost-effective protection when applied with adequate thickness. Hand-
application generally requires greater thickness than blown straw. The
thickness of straw may be reduced by half when used in conjunction with
seeding. In windy areas straw must be held in place by crimping, using a
tackifier, or covering with netting. Blown straw always has to be held in
place with a tackifier as even light winds will blow it away. Straw, however,
has several deficiencies that should be considered when selecting mulch
materials. It often introduces and/or encourages the propagation of weed
species and it has no significant long-term benefits It should also not be
used within the ordinary high-water elevation of surface waters (due to flot-
ation).
Hydromulch
Quality
Standards No growth inhibiting factors.
Application
Rates Approx. 35-45 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre
Remarks
Shall be applied with hydromulcher. Shall not be used without seed and
tackifier unless the application rate is at least doubled. Fibers longer than
about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less
than 3/4 inch.
Compost
Quality
Standards
No visible water or dust during handling. Must be produced per WAC 173-
350, Solid Waste Handling Standards, but may have up to 35% biosolids.
Application
Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs per cubic yard)
Remarks
More effective control can be obtained by increasing thickness to 3". Excel-
lent mulch for protecting final grades until landscaping because it can be dir-
ectly seeded or tilled into soil as an amendment. Compost used for mulch
has a coarser size gradation than compost used for BMP C125: Topsoiling
/ Composting or BMP T5.13: Post-Construction Soil Quality and Depth. It
is more stable and practical to use in wet areas and during rainy weather
conditions. Do not use near wetlands or near phosphorous impaired water
bodies.
Chipped
Site Veget-
ation
Quality
Standards
Gradations from fines to 6 inches in length for texture, variation, and inter-
locking properties. Include a mix of various sizes so that the average size
is between 2- and 4- inches.
Application
Rates 2" thick min.;
Table II-3.6: Mulch Standards and Guidelines
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Mulch Mater-
ial Guideline Description
Remarks
This is a cost-effective way to dispose of debris from clearing and grub-
bing, and it eliminates the problems associated with burning. Generally, it
should not be used on slopes above approx. 10% because of its tendency
to be transported by runoff. It is not recommended within 200 feet of sur-
face waters. If permanent seeding or planting is expected shortly after
mulch, the decomposition of the chipped vegetation may tie up nutrients
important to grass establishment.
Note: thick application of this material over existing grass, herbaceous spe-
cies, and some groundcovers could smother and kill vegetation.
Wood-
Based
Mulch
Quality
Standards
No visible water or dust during handling. Must be purchased from a supplier
with a Solid Waste Handling Permit or one exempt from solid waste reg-
ulations.
Application
Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs. per cubic yard)
Remarks
This material is often called "wood straw" or "hog fuel". The use of mulch
ultimately improves the organic matter in the soil. Special caution is
advised regarding the source and composition of wood-based mulches. Its
preparation typically does not provide any weed seed control, so evidence
of residual vegetation in its composition or known inclusion of weed plants
or seeds should be monitored and prevented (or minimized).
Wood
Strand
Mulch
Quality
Standards
A blend of loose, long, thin wood pieces derived from native conifer or
deciduous trees with high length-to-width ratio.
Application
Rates 2" thick min.
Remarks
Cost-effective protection when applied with adequate thickness. A min-
imum of 95-percent of the wood strand shall have lengths between 2 and
10-inches, with a width and thickness between 1/16 and 1/2-inches. The
mulch shall not contain resin, tannin, or other compounds in quantities that
would be detrimental to plant life. Sawdust or wood shavings shall not be
used as mulch. [Specification 9-14.4(4) from the Standard Specifications
for Road, Bridge, and Municipal Construction (WSDOT, 2016)
Table II-3.6: Mulch Standards and Guidelines (continued)
BMP C122: Nets and Blankets
Purpose
Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place
on steep slopes and in channels so that vegetation can become well established. In addition, some
nets and blankets can be used to permanently reinforce turf to protect drainage ways during high
flows.
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N/A
Nets (commonly called matting) are strands of material woven into an open, but high-tensile strength
net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven,
but instead form a layer of interlocking fibers, typically held together by a biodegradable or pho-
todegradable netting (for example, excelsior or straw blankets). They generally have lower tensile
strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both
nets and blankets.
Conditions of Use
Erosion control netting and blankets shall be made of natural plant fibers unaltered by synthetic
materials.
Erosion control nets and blankets should be used:
l To aid permanent vegetated stabilization of slopes 2H:1V or greater and with more than 10
feet of vertical relief.
l For drainage ditches and swales (highly recommended). The application of appropriate net-
ting or blanket to drainage ditches and swales can protect bare soil from channelized runoff
while vegetation is established. Nets and blankets also can capture a great deal of sediment
due to their open, porous structure. Nets and blankets can be used to permanently stabilize
channels and may provide a cost-effective, environmentally preferable alternative to riprap.
Disadvantages of nets and blankets include:
l Surface preparation is required.
l On slopes steeper than 2.5H:1V, net and blanket installers may need to be roped and har-
nessed for safety.
l They cost at least $4,000-6,000 per acre installed.
Advantages of nets and blankets include:
l Installation without mobilizing special equipment.
l Installation by anyone with minimal training
l Installation in stages or phases as the project progresses.
l Installers can hand place seed and fertilizer as they progress down the slope.
l Installation in any weather.
l There are numerous types of nets and blankets that can be designed with various parameters
in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability,
cost, and availability.
An alternative to nets and blankets in some limited conditions is BMP C202: Riprap Channel Lining.
Ensure that BMP C202: Riprap Channel Lining is appropriate before using it as a substitute for nets
and blankets.
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Design and Installation Specifications
l See Figure II-3.3: Channel Installation (Clackamas County et al., 2008) and Figure II-3.4:
Slope Installation for typical orientation and installation of nets and blankets used in channels
and as slope protection. Note: these are typical only; all nets and blankets must be installed
per manufacturer’s installation instructions.
l Installation is critical to the effectiveness of these products. If good ground contact is not
achieved, runoff can concentrate under the product, resulting in significant erosion.
l Installation of nets and blankets on slopes:
1. Complete final grade and track walk up and down the slope.
2. Install hydromulch with seed and fertilizer.
3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the
slope.
4. Install the leading edge of the net/blanket into the small trench and staple approximately
every 18 inches. NOTE: Staples are metal, “U”-shaped, and a minimum of 6 inches
long. Longer staples are used in sandy soils. Biodegradable stakes are also available.
5. Roll the net/blanket slowly down the slope as the installer walks backward. NOTE: The
net/blanket rests against the installer’s legs. Staples are installed as the net/blanket is
unrolled. It is critical that the proper staple pattern is used for the net/blanket being
installed. The net/blanket is not to be allowed to roll down the slope on its own as this
stretches the net/blanket, making it impossible to maintain soil contact. In addition, no
one is allowed to walk on the net/blanket after it is in place.
6. If the net/blanket is not long enough to cover the entire slope length, the trailing edge of
the upper net/blanket should overlap the leading edge of the lower net/blanket and be
stapled. On steeper slopes, this overlap should be installed in a small trench, stapled,
and covered with soil.
l With the variety of products available, it is impossible to cover all the details of appropriate use
and installation. Therefore, it is critical that the designer consult the manufacturer's inform-
ation and that a site visit takes place in order to ensure that the product specified is appro-
priate. Information is also available in WSDOT's Standard Specifications for Road, Bridge,
and Municipal Construction Division 8-01 and Division 9-14 (WSDOT, 2016).
l Use jute matting in conjunction with mulch (BMP C121: Mulching). Excelsior, woven straw
blankets and coir (coconut fiber) blankets may be installed without mulch. There are many
other types of erosion control nets and blankets on the market that may be appropriate in cer-
tain circumstances.
l In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because
they have a fairly open structure. Blankets typically do not require mulch because they usually
provide complete protection of the surface.
l Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of
synthetic blankets, as are riverbanks, beaches and other high-energy environments. If
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synthetic blankets are used, the soil should be hydromulched first.
l 100-percent biodegradable blankets are available for use in sensitive areas. These organic
blankets are usually held together with a paper or fiber mesh and stitching which may last up
to a year.
l Most netting used with blankets is photodegradable, meaning it breaks down under sunlight
(not UV stabilized). However, this process can take months or years even under bright sun.
Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find
non-degraded netting still in place several years after installation. This can be a problem if
maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and
small animals can become trapped in the netting.
Maintenance Standards
l Maintain good contact with the ground. Erosion must not occur beneath the net or blanket.
l Repair and staple any areas of the net or blanket that are damaged or not in close contact with
the ground.
l Fix and protect eroded areas if erosion occurs due to poorly controlled drainage.
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Figure II-3.3: Channel Installation
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NOT TO SCALE
f,V-
**/
** z fmmWmv. '?■>12m wm'Sz
6"-~J AV')/Xya'/a//
TERMINAL SLOPE AND CHANNELLONGITUDINAL ANCHOR TRENCH
ANCHOR TRENCH
ij -¥
■*
*-if 574AF AIT J-5'
INTERVALS.
-V
* * Jt f
f -tf
#
ff
e
CHECK SLOT AT 25’ INTERVALSw-w ISOMETRIC VIEW
ft
ft a.4^
ffPf*XKm•■:' e>/\X /\
INITIAL CHANNEL ANCHOR TRENCH
Z2
INTERMITTENT CHECK SLOT
Notes:
1. Check slots to be constructed per manufacturers specifications.
2. Staking or stapling layout per manufacturers specifications.(Clackamas County et al., 2008)
Channel Installation
Revised July 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Figure II-3.4: Slope Installation
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Volume II -Chapter 3 -Page 297
Anchor in 6" x 6" min.
trench and staple at
12" intervals
s’.
IMin. 2" overlap
i
Min. 6" overlap
t'.'.vVr:F'»• "V.
Staple overlaps
max. 5" spacingtrainIi
i—i
Bring material down to a level
area, turn the end under 4"
and staple at 12" intervals
Notes:
1.Slope surface shall be smooth before placement for
proper soil contact.
Stapling pattern as per manufacturer's recommendations.
Do not stretch blankets/mattings tight - allow the rolls to
mold to any irregularities.
For slopes less than 3H:1V, rolls may be placed in
horizontal strips.
If there is a berm at the top of the slope, anchor upslope
of the berm.
Lime, fertilize, and seed before installation. Planting of
shrubs, trees, etc. should occur after installation.
2.
3.
4.
5.
6.
NOT TO SCALE
Slope Installation
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
BMP C123: Plastic Covering
Purpose
Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.
Conditions of Use
Plastic covering may be used on disturbed areas that require cover measures for less than 30 days,
except as stated below.
l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel-
atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications
greater than six months.
l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that
might be adversely impacted by concentrated runoff. Such areas include steep and/or
unstable slopes.
l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on-
site measures to counteract the increases. Creating a trough with wattles or other material
can convey clean water away from these areas.
l To prevent undercutting, trench and backfill rolled plastic covering products.
l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance,
removal, and disposal add to the total costs of this BMP.
l Whenever plastic is used to protect slopes, install water collection measures at the base of the
slope. These measures include plastic-covered berms, channels, and pipes used to convey
clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a
plastic covered slope with dirty runoff from a project.
l Other uses for plastic include:
o Temporary ditch liner.
o Pond liner in temporary sediment pond.
o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel
being stored.
o Emergency slope protection during heavy rains.
o Temporary drainpipe (“elephant trunk”) used to direct water.
Design and Installation Specifications
l Plastic slope cover must be installed as follows:
1. Run plastic up and down the slope, not across the slope.
2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet.
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3. Provide a minimum of 8-inch overlap at the seams.
4. On long or wide slopes, or slopes subject to wind, tape all seams.
5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope
and backfill with soil to keep water from flowing underneath.
6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them
together with twine to hold them in place.
7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This
prevents high velocity runoff from contacting bare soil, which causes extreme erosion.
8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be
staked in place.
l Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
l 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.
Maintenance Standards
l Torn sheets must be replaced and open seams repaired.
l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi-
ation.
l Completely remove plastic when no longer needed.
l Dispose of old tires used to weight down plastic sheeting appropriately.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C124: Sodding
Purpose
The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage
paths where concentrated overland flow will occur.
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N/A
BMP C140: Dust Control
Purpose
Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage
ways, and surface waters.
Conditions of Use
Use dust control in areas (including roadways) subject to surface and air movement of dust where
on-site or off-site impacts to roadways, drainage ways, or surface waters are likely.
Design and Installation Specifications
l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching,
or paving is impractical, apply gravel or landscaping rock.
l Limit dust generation by clearing only those areas where immediate activity will take place,
leaving the remaining area(s) in the original condition. Maintain the original ground cover as
long as practical.
l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos-
ures for small dust sources.
l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of
mud onto the street, refer to BMP C105: Stabilized Construction Access and BMP C106:
Wheel Wash.
l Irrigation water can be used for dust control. Irrigation systems should be installed as a first
step on sites where dust control is a concern.
l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and
cautions regarding handling and application. Used oil is prohibited from use as a dust sup-
pressant. Local governments may approve other dust palliatives such as calcium chloride or
PAM.
l PAM (BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate
of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect-
ive than water alone. This is due to increased infiltration of water into the soil and reduced
evaporation. In addition, small soil particles are bonded together and are not as easily trans-
ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note
that the application rate specified here applies to this BMP, and is not the same application
rate that is specified in BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection, but the
downstream protections still apply.
Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use.
PAM shall not be directly applied to water or allowed to enter a water body.
l Contact your local Air Pollution Control Authority for guidance and training on other dust con-
trol measures. Compliance with the local Air Pollution Control Authority constitutes
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compliance with this BMP.
l Use vacuum street sweepers.
l Remove mud and other dirt promptly so it does not dry and then turn into dust.
l Techniques that can be used for unpaved roads and lots include:
o Lower speed limits. High vehicle speed increases the amount of dust stirred up from
unpaved roads and lots.
o Upgrade the road surface strength by improving particle size, shape, and mineral types
that make up the surface and base materials.
o Add surface gravel to reduce the source of dust emission. Limit the amount of fine
particles (those smaller than .075 mm) to 10 to 20 percent.
o Use geotextile fabrics to increase the strength of new roads or roads undergoing recon-
struction.
o Encourage the use of alternate, paved routes, if available.
o Apply chemical dust suppressants using the admix method, blending the product with
the top few inches of surface material. Suppressants may also be applied as surface
treatments.
o Limit dust-causing work on windy days.
o Pave unpaved permanent roads and other trafficked areas.
Maintenance Standards
Respray area as necessary to keep dust to a minimum.
BMP C150: Materials on Hand
Purpose
Keep quantities of erosion prevention and sediment control materials on the project site at all times
to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav-
ing these materials on-site reduces the time needed to replace existing or implement new BMPs
when inspections indicate that existing BMPs are not meeting the Construction SWPPP require-
ments. In addition, contractors can save money by buying some materials in bulk and storing them at
their office or yard.
Conditions of Use
l Construction projects of any size or type can benefit from having materials on hand. A small
commercial development project could have a roll of plastic and some gravel available for
immediate protection of bare soil and temporary berm construction. A large earthwork project,
such as highway construction, might have several tons of straw, several rolls of plastic, flexible
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pipe, sandbags, geotextile fabric and steel “T” posts.
l Materials should be stockpiled and readily available before any site clearing, grubbing, or
earthwork begins. A large contractor or project proponent could keep a stockpile of materials
that are available for use on several projects.
l If storage space at the project site is at a premium, the contractor could maintain the materials
at their office or yard. The office or yard must be less than an hour from the project site.
Design and Installation Specifications
Depending on project type, size, complexity, and length, materials and quantities will vary. A good
minimum list of items that will cover numerous situations includes:
l Clear Plastic, 6 mil
l Drainpipe, 6 or 8 inch diameter
l Sandbags, filled
l Straw Bales for mulching
l Quarry Spalls
l Washed Gravel
l Geotextile Fabric
l Catch Basin Inserts
l Steel "T" Posts
l Silt fence material
l Straw Wattles
Maintenance Standards
l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept
covered and out of both sun and rain.
l Re-stock materials as needed.
BMP C151: Concrete Handling
Purpose
Concrete work can generate process water and slurry that contain fine particles and high pH, both of
which can violate water quality standards in the receiving water. Concrete spillage or concrete dis-
charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con-
crete process water, and concrete slurry from entering waters of the State.
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Conditions of Use
Any time concrete is used, utilize these management practices. Concrete construction project com-
ponents include, but are not limited to:
l Curbs
l Sidewalks
l Roads
l Bridges
l Foundations
l Floors
l Runways
Disposal options for concrete, in order of preference are:
1. Off-site disposal
2. Concrete wash-out areas (see BMP C154: Concrete Washout Area)
3. De minimus washout to formed areas awaiting concrete
Design and Installation Specifications
l Wash concrete truck drums at an approved off-site location or in designated concrete
washout areas only. Do not wash out concrete trucks onto the ground (including formed areas
awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP
C154: Concrete Washout Area for information on concrete washout areas.
o Return unused concrete remaining in the truck and pump to the originating batch plant
for recycling. Do not dump excess concrete on site, except in designated concrete
washout areas as allowed in BMP C154: Concrete Washout Area.
l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats,
trowels, and wheelbarrows) into designated concrete washout areas or into formed areas
awaiting concrete pour.
l At no time shall concrete be washed off into the footprint of an area where an infiltration fea-
ture will be installed.
l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir-
ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.
l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly
(without detention or treatment) to natural or constructed stormwater conveyances.
l Contain washwater and leftover product in a lined container when no designated concrete
washout areas (or formed areas, allowed as described above) are available. Dispose of con-
tained concrete and concrete washwater (process water) properly.
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l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface
waters.
l Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment require-
ments.
l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require-
ments if the project involves one of the following activities:
o Significant concrete work (as defined in the CSWGP).
o The use of soils amended with (but not limited to) Portland cement-treated base,
cement kiln dust or fly ash.
o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for
high pH.
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repair the same day.
BMP C152: Sawcutting and Surfacing Pollution
Prevention
Purpose
Sawcutting and surfacing operations generate slurry and process water that contains fine particles
and high pH (concrete cutting), both of which can violate the water quality standards in the receiving
water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to
minimize and eliminate process water and slurry created through sawcutting or surfacing from enter-
ing waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting or surfacing operations take place. Saw-
cutting and surfacing operations include, but are not limited to:
l Sawing
l Coring
l Grinding
l Roughening
l Hydro-demolition
l Bridge and road surfacing
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Design and Installation Specifications
l Vacuum slurry and cuttings during cutting and surfacing operations.
l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.
l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ-
ing stormwater systems. This may require temporarily blocking catch basins.
l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur-
face water quality standards.
l Do not allow process water generated during hydro-demolition, surface roughening or similar
operations to drain to any natural or constructed drainage conveyance including stormwater
systems. Dispose of process water in a manner that does not violate ground water or surface
water quality standards.
l Handle and dispose of cleaning waste material and demolition debris in a manner that does
not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an
appropriate disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry, cuttings, or process water could enter
waters of the state. If inspections show that a violation of water quality standards could occur, stop
operations and immediately implement preventive measures such as berms, barriers, secondary
containment, and/or vacuum trucks.
BMP C153: Material Delivery, Storage, and
Containment
Purpose
Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses
from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater-
ials in a designated area, and install secondary containment.
Conditions of Use
Use at construction sites with delivery and storage of the following materials:
l Petroleum products such as fuel, oil and grease
l Soil stabilizers and binders (e.g., Polyacrylamide)
l Fertilizers, pesticides and herbicides
l Detergents
l Asphalt and concrete compounds
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l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds
l Any other material that may be detrimental if released to the environment
Design and Installation Specifications
l The temporary storage area should be located away from vehicular traffic, near the con-
struction entrance(s), and away from waterways or storm drains.
l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be
kept in their original labeled containers.
l Hazardous material storage on-site should be minimized.
l Hazardous materials should be handled as infrequently as possible.
l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered
area.
l Materials should be stored in secondary containments, such as an earthen dike, horse trough,
or even a children’s wading pool for non-reactive materials such as detergents, oil, grease,
and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con-
crete mixing trays.
l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items
on a pallet and, when possible, within secondary containment.
l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater
on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of
drums, preventing water from collecting.
l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be
stored in approved containers and drums and shall not be overfilled. Containers and drums
shall be stored in temporary secondary containment facilities.
l Temporary secondary containment facilities shall provide for a spill containment volume able
to contain 10% of the total enclosed container volume of all containers, or 110% of the capa-
city of the largest container within its boundary, whichever is greater.
l Secondary containment facilities shall be impervious to the materials stored therein for a min-
imum contact time of 72 hours.
l Sufficient separation should be provided between stored containers to allow for spill cleanup
and emergency response access.
l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall
be covered during non-working days, prior to and during rain events.
l Keep material storage areas clean, organized and equipped with an ample supply of appro-
priate spill clean-up material (spill kit).
l The spill kit should include, at a minimum:
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o 1-Water Resistant Nylon Bag
o 3-Oil Absorbent Socks 3”x 4’
o 2-Oil Absorbent Socks 3”x 10’
o 12-Oil Absorbent Pads 17”x19”
o 1-Pair Splash Resistant Goggles
o 3-Pair Nitrile Gloves
o 10-Disposable Bags with Ties
o Instructions
Maintenance Standards
l Secondary containment facilities shall be maintained free of accumulated rainwater and spills.
In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed
into drums. These liquids shall be handled as hazardous waste unless testing determines
them to be non-hazardous.
l Re-stock spill kit materials as needed.
BMP C154: Concrete Washout Area
Purpose
Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting
washout off-site, or performing on-site washout in a designated area.
Conditions of Use
Concrete washout areas are implemented on construction projects where:
l Concrete is used as a construction material
l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant,
etc.).
l Concrete truck drums are washed on-site.
Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete
handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel-
barrows) may be washed into formed areas awaiting concrete pour.
At no time shall concrete be washed off into the footprint of an area where an infiltration feature will
be installed.
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Design and Installation Specifications
Implementation
l Perform washout of concrete truck drums at an approved off-site location or in designated con-
crete washout areas only.
l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets,
or streams.
l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir-
ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.
l Do not allow excess concrete to be dumped on-site, except in designated concrete washout
areas as allowed above.
l Concrete washout areas may be prefabricated concrete washout containers, or self-installed
structures (above-grade or below-grade).
l Prefabricated containers are most resistant to damage and protect against spills and leaks.
Companies may offer delivery service and provide regular maintenance and disposal of solid
and liquid waste.
l If self-installed concrete washout areas are used, below-grade structures are preferred over
above-grade structures because they are less prone to spills and leaks.
l Self-installed above-grade structures should only be used if excavation is not practical.
l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to
contain all liquid and concrete waste generated by washout operations.
Education
l Discuss the concrete management techniques described in this BMP with the ready-mix con-
crete supplier before any deliveries are made.
l Educate employees and subcontractors on the concrete waste management techniques
described in this BMP.
l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead
(CESCL) to oversee and enforce concrete waste management procedures.
l A sign should be installed adjacent to each concrete washout area to inform concrete equip-
ment operators to utilize the proper facilities.
Contracts
Incorporate requirements for concrete waste management into concrete supplier and subcontractor
agreements.
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Location and Placement
l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains,
open ditches, water bodies, or wetlands.
l Allow convenient access to the concrete washout area for concrete trucks, preferably near the
area where the concrete is being poured.
l If trucks need to leave a paved area to access the concrete washout area, prevent track-out
with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Access). These
areas should be far enough away from other construction traffic to reduce the likelihood of acci-
dental damage and spills.
l The number of concrete washout areas you install should depend on the expected demand
for storage capacity.
l On large sites with extensive concrete work, concrete washout areas should be placed in mul-
tiple locations for ease of use by concrete truck drivers.
Concrete Truck Washout Procedures
l Washout of concrete truck drums shall be performed in designated concrete washout areas
only.
l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks
and discharged into designated concrete washout areas or properly disposed of off-site.
Concrete Washout Area Installation
l Concrete washout areas should be constructed as shown in the figures below, with a recom-
mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to
contain all liquid and concrete waste generated by washout operations.
l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free
of holes, tears, or other defects that compromise the impermeability of the material.
l Lath and flagging should be commercial type.
l Liner seams shall be installed in accordance with manufacturers’ recommendations.
l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the
plastic lining material.
Maintenance Standards
Inspection and Maintenance
l Inspect and verify that concrete washout areas are in place prior to the commencement of con-
crete work.
l Once concrete wastes are washed into the designated washout area and allowed to harden,
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the concrete should be broken up, removed, and disposed of per applicable solid waste reg-
ulations. Dispose of hardened concrete on a regular basis.
l During periods of concrete work, inspect the concrete washout areas daily to verify continued
performance.
o Check overall condition and performance.
o Check remaining capacity (% full).
o If using self-installed concrete washout areas, verify plastic liners are intact and side-
walls are not damaged.
o If using prefabricated containers, check for leaks.
l Maintain the concrete washout areas to provide adequate holding capacity with a minimum
freeboard of 12 inches.
l Concrete washout areas must be cleaned, or new concrete washout areas must be con-
structed and ready for use once the concrete washout area is 75% full.
l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in
an approved manner.
l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground.
l Do not discharge to the sanitary sewer without local approval.
l Place a secure, non-collapsing, non-water collecting cover over the concrete washout
area prior to predicted wet weather to prevent accumulation and overflow of pre-
cipitation.
l Remove and dispose of hardened concrete and return the structure to a functional con-
dition. Concrete may be reused on-site or hauled away for disposal or recycling.
l When you remove materials from a self-installed concrete washout area, build a new struc-
ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and
make any necessary repairs. Re-line the structure with new plastic after each cleaning.
Removal of Concrete Washout Areas
l When concrete washout areas are no longer required for the work, the hardened concrete,
slurries and liquids shall be removed and properly disposed of.
l Materials used to construct concrete washout areas shall be removed from the site of the work
and disposed of or recycled.
l Holes, depressions or other ground disturbance caused by the removal of the concrete
washout areas shall be backfilled, repaired, and stabilized to prevent erosion.
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Volume II -Chapter 3 -Page 323
Figure II-3.7: Concrete Washout Area with Wood Planks
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Volume II -Chapter 3 -Page 324
3m Minimum
-e- -e-Lath and flagging
on 3 sides
Sandbag0□ CD □
'>TI SandbagBermc>
10 mil plastic lining□Varies A iAf 'Xo-o-1 m •x
Q —I Berm
10 CD CD Section A-A6
10 mil plastic liningPlan Notes:
1.Actual layout
determined in the field.
A concrete washout
sign shall be installed
within 10 m of the
temporary concrete
washout facility.
Type "Below Grade ii 2.
3m Minimum
JSL JHL
T8T
Wood frame
securely fastened
around entire
perimeter with two
stakes
B BtI■s-a ■s-a
Varies 10 mil
plastic lining
S 3 E VStake (typ.)
M Section B-Bw
10 mil plastic lining
Two-stacked
2x12 rough
wood frame
Plan
Type "Above Grade" with Wood Planks
NOT TO SCALE
Concrete Washout Area with Wood Planks
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Figure II-3.8: Concrete Washout Area with Straw Bales
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Volume II -Chapter 3 -Page 325
Straw bale
10 mil plastic lining Binding wire
Staples
(2 per bale)Native material
(optional)
Wood or
metal stakes
(2 per bale)
Plywood
1200 mm x 610 mm
painted white
Wood post
(89 mm x 89 mm
x 2.4 m)Lag screws
(12.5 mm)Section B-B Black letters
150 mm heightILCONCRETE
WASHOUT'
U915 mm
f 915 mm
T3m Minimum Concrete Washout Sign
Detail (or equivalent)Stake (typ)A
B Bt1 i 50 mm
3.05 mm dia.
steel wire
Varies
200 mm
f
Staple Detail
10 mil plastic lining Notes:Straw bale
(typ)1. Actual layout
determined in the field.
The concrete washout
sign shall be installed
within 10 m of the
temporary concrete
washout facility.
Plan 2.
Type "Above Grade" with Straw Bales
NOT TO SCALE
Concrete Washout Area with Straw Bales
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp
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Volume II -Chapter 3 -Page 326
■•-0
\riy
l-j
X
-
NOT TO SCALE
Prefabricated Concrete Washout Container
w/Ramp
Revised June 2016DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyright.htmMor copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
BMP C160: Certified Erosion and Sediment Control
Lead
Purpose
The project proponent designates at least one person as the responsible representative in charge of
erosion and sediment control (ESC), and water quality protection. The designated person shall be
responsible for ensuring compliance with all local, state, and federal erosion and sediment control
and water quality requirements. Construction sites one acre or larger that discharge to waters of the
State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible
representative.
Conditions of Use
A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur-
face waters of the state. Sites less than one acre may have a person without CESCL certification
conduct inspections.
The CESCL shall:
l Have a current certificate proving attendance in an erosion and sediment control training
course that meets the minimum ESC training and certification requirements established by
Ecology.
Ecology has provided the minimum requirements for CESCL course training, as well as a list
of ESC training and certification providers at:
https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed-
iment-control
OR
l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform-
ation go to:
http://www.envirocertintl.org/cpesc/
Specifications
l CESCL certification shall remain valid for three years.
l The CESCL shall have authority to act on behalf of the contractor or project proponent and
shall be available, or on-call, 24 hours per day throughout the period of construction.
l The Construction SWPPP shall include the name, telephone number, fax number, and
address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention
Plans (Construction SWPPPs).
l A CESCL may provide inspection and compliance services for multiple construction projects
in the same geographic region, but must be on site whenever earthwork activities are
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occurring that could generate release of turbid water.
l Duties and responsibilities of the CESCL shall include, but are not limited to the following:
o Maintaining a permit file on site at all times which includes the Construction SWPPP
and any associated permits and plans.
o Directing BMP installation, inspection, maintenance, modification, and removal.
o Updating all project drawings and the Construction SWPPP with changes made.
o Completing any sampling requirements including reporting results using electronic Dis-
charge Monitoring Reports (WebDMR).
o Facilitate, participate in, and take corrective actions resulting from inspections per-
formed by outside agencies or the owner.
o Keeping daily logs, and inspection reports. Inspection reports should include:
n Inspection date/time.
n Weather information; general conditions during inspection and approximate
amount of precipitation since the last inspection.
n Visual monitoring results, including a description of discharged stormwater. The
presence of suspended sediment, turbid water, discoloration, and oil sheen shall
be noted, as applicable.
n Any water quality monitoring performed during inspection.
n General comments and notes, including a brief description of any BMP repairs,
maintenance or installations made as a result of the inspection.
n A summary or list of all BMPs implemented, including observations of all
erosion/sediment control structures or practices. The following shall be noted:
1. Locations of BMPs inspected.
2. Locations of BMPs that need maintenance.
3. Locations of BMPs that failed to operate as designed or intended.
4. Locations of where additional or different BMPs are required.
BMP C162: Scheduling
Purpose
Sequencing a construction project reduces the amount and duration of soil exposed to erosion by
wind, rain, runoff, and vehicle tracking.
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Conditions of Use
The construction sequence schedule is an orderly listing of all major land-disturbing activities
together with the necessary erosion and sedimentation control measures planned for the project.
This type of schedule guides the contractor on work to be done before other work is started so that
serious erosion and sedimentation problems can be avoided.
Following a specified work schedule that coordinates the timing of land-disturbing activities and the
installation of control measures is perhaps the most cost-effective way of controlling erosion during
construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen-
cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and
restores protective cover quickly can significantly reduce the erosion potential of a site.
Design Considerations
l Minimize construction during rainy periods.
l Schedule projects to disturb only small portions of the site at any one time. Complete grading
as soon as possible. Immediately stabilize the disturbed portion before grading the next por-
tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses.
II-3.3 Construction Runoff BMPs
BMP C200: Interceptor Dike and Swale
Purpose
Provide a dike of compacted soil or a swale at the top or base of a disturbed slope or along the peri-
meter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept
the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can
prevent storm runoff from entering the work area or sediment-laden runoff from leaving the con-
struction site.
Conditions of Use
Use an interceptor dike or swale where runoff from an exposed site or disturbed slope must be con-
veyed to an erosion control BMP which can safely convey the stormwater.
l Locate upslope of a construction site to prevent runoff from entering the disturbed area.
l When placed horizontally across a disturbed slope, it reduces the amount and velocity of run-
off flowing down the slope.
l Locate downslope to collect runoff from a disturbed area and direct it to a sediment BMP (e.g.
BMP C240: Sediment Trap or BMP C241: Sediment Pond (Temporary)).
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thickness is 2 feet.
o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an
engineered energy dissipator.
o Filter fabric or erosion control blankets should always be used under riprap to prevent
scour and channel erosion. See BMP C122: Nets and Blankets.
l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas.
This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart-
ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals.
Maintenance Standards
l Inspect and repair as needed.
l Add rock as needed to maintain the intended function.
l Clean energy dissipator if sediment builds up.
BMP C220: Inlet Protection
Purpose
Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta-
bilization of the disturbed area.
Conditions of Use
Use inlet protection at inlets that are operational before permanent stabilization of the disturbed
areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and
within 500 feet of a disturbed or construction area, unless those inlets are preceded by a sediment
trapping BMP.
Also consider inlet protection for lawn and yard drains on new home construction. These small and
numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof
drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap
these drains to prevent sediment from entering the system until completion of landscaping. Provide
18-inches of sod around each finished lawn and yard drain.
Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods
for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain-
age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with
additional end-of-pipe treatment where stormwater ponding would cause a hazard.
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Type of Inlet Pro-
tection
Emergency
Overflow
Applicable for
Paved/ Earthen Sur-
faces
Conditions of Use
Drop Inlet Protection
Excavated drop
inlet protection
Yes, temporary
flooding may
occur
Earthen
Applicable for heavy flows. Easy
to maintain. Large area requirement:
30'x30'/acre
Block and gravel
drop inlet pro-
tection
Yes Paved or Earthen Applicable for heavy concentrated flows.
Will not pond.
Gravel and wire
drop inlet pro-
tection
No Paved or Earthen Applicable for heavy concentrated flows.
Will pond. Can withstand traffic.
Catch basin filters Yes Paved or Earthen Frequent maintenance required.
Curb Inlet Protection
Curb inlet pro-
tection with
wooden weir
Small capacity
overflow Paved Used for sturdy, more compact install-
ation.
Block and gravel
curb inlet pro-
tection
Yes Paved Sturdy, but limited filtration.
Culvert Inlet Protection
Culvert inlet sed-
iment trap N/A N/A 18 month expected life.
Table II-3.10: Storm Drain Inlet Protection
Design and Installation Specifications
Excavated Drop Inlet Protection
Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet.
Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe-
cifications for excavated drop inlet protection include:
l Provide a depth of 1-2 ft as measured from the crest of the inlet structure.
l Slope sides of excavation should be no steeper than 2H:1V.
l Minimum volume of excavation is 35 cubic yards.
l Shape the excavation to fit the site, with the longest dimension oriented toward the longest
inflow area.
l Install provisions for draining to prevent standing water.
l Clear the area of all debris.
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l Grade the approach to the inlet uniformly.
l Drill weep holes into the side of the inlet.
l Protect weep holes with screen wire and washed aggregate.
l Seal weep holes when removing structure and stabilizing area.
l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass
flow.
Block and Gravel Filter
A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel.
See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil-
ters include:
l Provide a height of 1 to 2 feet above the inlet.
l Recess the first row of blocks 2-inches into the ground for stability.
l Support subsequent courses by placing a pressure treated wood 2x4 through the block open-
ing.
l Do not use mortar.
l Lay some blocks in the bottom row on their side to allow for dewatering the pool.
l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings.
l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter.
l An alternative design is a gravel berm surrounding the inlet, as follows:
o Provide a slope of 3H:1V on the upstream side of the berm.
o Provide a slope of 2H:1V on the downstream side of the berm.
o Provide a 1-foot wide level stone area between the gravel berm and the inlet.
o Use stones 3 inches in diameter or larger on the upstream slope of the berm.
o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of
the berm.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 358
Figure II-3.17: Block and Gravel Filter
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 359
A
Drain grate r>Aft> QS, SSL ogjfe Q. ~ _
?rygioSOso^cy.;Concrete block
Sfei A*
o• o>cr> °i?o
^•Pa-
■sPc^I?
4 STTO <&',
Gravel backfill■osVf\
A-°i
° _?o
“■'frvSPP^
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to.
gdp> §0-^<S> q®
v«r.^4y A
Plan View
Concrete block Wire screen or
filter fabric
Overflow
water
Gravel backfill Ponding height
|5»S Water'^n iplllpfls^Drop inlet
Section A-A
Notes:
1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas, (less
than 5%)
2. Excavate a basin of sufficient size adjacent to the drop inlet.
3. The top of the structure (ponding height) must be well below the ground elevation
downslope to prevent runoff from bypassing the inlet. A temporary dike may be
necessary on the downslope side of the structure.
NOT TO SCALE
Block and Gravel Filter
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Gravel and Wire Mesh Filter
Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not
provide an overflow. Design and installation specifications for gravel and wire mesh filters include:
l Use a hardware cloth or comparable wire mesh with ½-inch openings.
o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey-
ond each side of the inlet structure.
o Overlap the strips if more than one strip of mesh is necessary.
l Place coarse aggregate over the wire mesh.
o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at
least 18-inches on all sides.
Catch Basin Filters
Catch basin filters are designed by manufacturers for construction sites. The limited sediment stor-
age capacity increases the amount of inspection and maintenance required, which may be daily for
heavy sediment loads. To reduce maintenance requirements, combine a catch basin filter with
another type of inlet protection. This type of inlet protection provides flow bypass without overflow
and therefore may be a better method for inlets located along active rights-of-way. Design and install-
ation specifications for catch basin filters include:
l Provides 5 cubic feet of storage.
l Requires dewatering provisions.
l Provides a high-flow bypass that will not clog under normal use at a construction site.
l Insert the catch basin filter in the catch basin just below the grating.
Curb Inlet Protection with Wooden Weir
Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb
inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection
with wooden weirs include:
l Use wire mesh with ½-inch openings.
l Use extra strength filter cloth.
l Construct a frame.
l Attach the wire and filter fabric to the frame.
l Pile coarse washed aggregate against the wire and fabric.
l Place weight on the frame anchors.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 360
Block and Gravel Curb Inlet Protection
Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and
gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe-
cifications for block and gravel curb inlet protection include:
l Use wire mesh with ½-inch openings.
l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening.
These are spacer blocks.
l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks.
l Place blocks on their sides across the front of the inlet and abutting the spacer blocks.
l Place wire mesh over the outside vertical face.
l Pile coarse aggregate against the wire to the top of the barrier.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 361
Figure II-3.18: Block and Gravel Curb Inlet Protection
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 362
A
Catch basin
Back of sidewalk
2x4 Wood stud
Curb inletBack of curb Concrete block
pt
< 1'[ ]o a &
Wire screen or
filter fabric
3c§
i?$C5 3Ko..om,o jOjsQi 0»Wm JS SS
A Concrete block% inch (20 mm)
Drain gravel Plan View
Ponding height
% inch (20 mm)
Drain gravel Overflow
w I□Curb inlet
Wire screen or
filter fabric r2x4 Wood stud
(100x50 Timber stud)/iCatch basin
Concrete block
Section A-A
Notes:
1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street
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.NOT TO SCALE
Block and Gravel Curb Inlet Protection
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Curb and Gutter Sediment Barrier
Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3
feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation
specifications for curb and gutter sediment barrier include:
l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high
and 3 feet wide, at least 2 feet from the inlet.
l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the
trap to sediment trap standards for protecting a culvert inlet.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 363
Figure II-3.19: Curb and Gutter Barrier
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 364
Back of sidewalk
Burlap sacks to
overlap onto curb Back of curb
Curb inletRunoff
SpillwayRunoff
Catch basin
Plan View
Gravel filled sandbags
stacked tightly
Notes:
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.NOT TO SCALE
Curb and Gutter Barrier
Revised June 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Maintenance Standards
l Inspect all forms of inlet protection frequently, especially after storm events. Clean and
replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the
inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and
put fresh rock around the inlet.
l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly
over the surrounding land area or stockpile and stabilize as appropriate.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C231: Brush Barrier
Purpose
The purpose of brush barriers is to 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
l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre.
l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub-
stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap-
ping BMP. The only circumstance in which overland flow can be treated solely by a brush
barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is
small.
l Brush barriers should only be installed on contours.
Design and Installation Specifications
l Height: 2 feet (minimum) to 5 feet (maximum).
l Width: 5 feet at base (minimum) to 15 feet (maximum).
l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability
of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 365
N/A
Design and Installation Specifications
l The vegetated strip shall consist of a continuous strip of dense vegetation with topsoil for a min-
imum of a 25-foot length along the flowpath. 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.
l The slope within the vegetated strip shall not exceed 4H:1V.
l The uphill boundary of the vegetated strip shall be delineated with clearing limits.
Maintenance Standards
l Any areas damaged by erosion or construction activity shall be seeded immediately and pro-
tected by mulch.
l If more than 5 feet of the original vegetated strip width has had vegetation removed or is being
eroded, sod must be installed.
l If there are indications that concentrated flows are traveling across the vegetated strip, storm-
water runoff controls must be installed to reduce the flows entering the vegetated strip, or addi-
tional perimeter protection must be installed.
BMP C235: Wattles
Purpose
Wattles are temporary erosion and sediment control barriers consisting of straw, compost, or other
material that is wrapped in netting made of natural plant fiber or similar encasing material. They
reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sed-
iment.
Conditions of Use
l Wattles shall consist of cylinders of plant material such as weed-free straw, coir, wood chips,
excelsior, or wood fiber or shavings encased within netting made of natural plant fibers
unaltered by synthetic materials.
l Use wattles:
o In disturbed areas that require immediate erosion protection.
o On exposed soils during the period of short construction delays, or over winter months.
o On slopes requiring stabilization until permanent vegetation can be established.
l The material used dictates the effectiveness period of the wattle. Generally, wattles are effect-
ive for one to two seasons.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 377
l Prevent rilling beneath wattles by entrenching and overlapping wattles to prevent water from
passing between them.
Design Criteria
l See Figure II-3.24: Wattles for typical construction details.
l Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length.
l Install wattles perpendicular to the flow direction and parallel to the slope contour.
l Place wattles in shallow trenches, staked along the contour of disturbed or newly constructed
slopes. Dig narrow trenches 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 areas with high rainfall,
the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the
wattle.
l Start building trenches and installing wattles from the base of the slope and work up. Spread
excavated material evenly along the uphill slope and compact it using hand tamping or other
methods.
l Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil
type, and rainfall. The steeper the slope the closer together the trenches.
l Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches
behind one another.
l Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle.
l If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle
and into the soil.
l Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow cuttings or 3/8-
inch rebar can also be used for stakes.
l Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake pro-
truding above the wattle.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 378
Figure II-3.24: Wattles
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 379
3' -4'
(1,2 m)
jjlSi\fc Viz Overlap adjacent
rolls 12" behind
one another
/
/■y
\Straw rolls must be
placed along slope
contours
///
\/
\
v-C
»S
\J/10' - 25' (3-8m)d
■■■
Spacing depends
on soil type and
slope steepness
y.
Sediment, organic matter,
and native seeds are
captured behind the rolls.*3
3"-5" (75-125mm)
N\
8"-10" Dia.
(200-250mm)A///-<A.//A
Live Stake //
//
// 1"x1" Stake
£/ (25 x 25mm)/
\/
V NOTE:l 1. Straw roll installation requires the placement and secure staking
of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour.
Runoff must not be allowed to run under or around roll.
A
NOT TO SCALE
Wattles
Revised December 2016
DEPARTMENT OF
ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions,
limitation of liability, and disclaimer.State of Washington
Maintenance Standards
l Wattles may require maintenance to ensure they are in contact with soil and thoroughly
entrenched, especially after significant rainfall on steep sandy soils.
l Inspect the slope after significant storms and repair any areas where wattles are not tightly
abutted or water has scoured beneath the wattles.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C236: Vegetative Filtration
Purpose
Vegetative filtration as a BMP is used in conjunction with detention storage in the form of portable
tanks or BMP C241: Sediment Pond (Temporary), BMP C206: Level Spreader, and a pumping sys-
tem with surface intake. Vegetative filtration improves turbidity levels of stormwater discharges by fil-
tering runoff through existing vegetation where undisturbed forest floor duff layer or established lawn
with thatch layer are present. Vegetative filtration can also be used to infiltrate dewatering waste
from foundations, vaults, and trenches as long as runoff does not occur.
Conditions of Use
l For every five acres of disturbed soil use one acre of grass field, farm pasture, or wooded
area. Reduce or increase this area depending on project size, ground water table height, and
other site conditions.
l Wetlands shall not be used for vegetative filtration.
l Do not use this BMP in areas with a high ground water table, or in areas that will have a high
seasonal ground water table during the use of this BMP.
l This BMP may be less effective on soils that prevent the infiltration of the water, such as hard
till.
l Using other effective source control measures throughout a construction site will prevent the
generation of additional highly turbid water and may reduce the time period or area need for
this BMP.
l Stop distributing water into the vegetated filtration area if standing water or erosion results.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 380
Maintenance Standards
l Remove sediment from the pond when it reaches 1 foot in depth.
l Repair any damage to the pond embankments or slopes.
BMP C250: Construction Stormwater Chemical
Treatment
Purpose
This BMP applies when using chemicals to treat turbidity in stormwater by either batch or flow-
through chemical treatment.
Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a con-
struction site. BMP C241: Sediment Pond (Temporary) is effective at removing larger particulate
matter by gravity settling, but is ineffective at removing smaller particulates such as clay and fine silt.
Traditional Construction Stormwater BMPs may not be adequate to ensure compliance with the
water quality standards for turbidity in the receiving water.
Chemical treatment can reliably provide exceptional reductions of turbidity and associated pol-
lutants. Chemical treatment may be required to meet turbidity stormwater discharge requirements,
especially when construction proceeds through the wet season.
Conditions of Use
Formal written approval from Ecology is required for the use of chemical treatment, regardless of
site size. See https://fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of
the Request for Chemical Treatment form. The Local Permitting Authority may also require review
and approval. When authorized, the chemical treatment systems must be included in the Con-
struction Stormwater Pollution Prevention Plan (SWPPP).
Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic organ-
isms. The Chemical Technology Assessment Protocol - Ecology (CTAPE) must be used to evaluate
chemicals proposed for stormwater treatment. Only chemicals approved by Ecology under the
CTAPE may be used for stormwater treatment. The approved chemicals, their allowable application
techniques (batch treatment or flow-through treatment), allowable application rates, and conditions
of use can be found at the Department of Ecology Emerging Technologies website:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee-
guidance-resources/Emerging-stormwater-treatment-technologies
Background on Chemical Treatment Systems
Coagulation and flocculation have been used for over a century to treat water. The use of coagu-
lation and flocculation to treat stormwater is a very recent application. Experience with the treatment
of water and wastewater has resulted in a basic understanding of the process, in particular factors
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 396
that affect performance. This experience can provide insights as to how to most effectively design
and operate similar systems in the treatment of stormwater.
Fine particles suspended in water give it a milky appearance, measured as turbidity. Their small size,
often much less than 1 µm in diameter, give them a very large surface area relative to their volume.
These fine particles typically carry a negative surface charge. Largely because of these two factors
(small size and negative charge), these particles tend to stay in suspension for extended periods of
time. Thus, removal is not practical by gravity settling. These are called stable suspensions. Chem-
icals like polymers, as well as inorganic chemicals such as alum, speed the settling process. The
added chemical destabilizes the suspension and causes the smaller particles to flocculate. The pro-
cess consists of three primary steps: coagulation, flocculation, and settling or clarification. Ecology
requires a fourth step, filtration, on all stormwater chemical treatment systems to reduce floc dis-
charge and to provide monitoring prior to discharge.
General Design and Installation Specifications
l Chemicals approved for use in Washington State are listed on Ecology's TAPE website,
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/technologies.html, under the "Con-
struction" tab.
l Care must be taken in the design of the withdrawal system to minimize outflow velocities and
to prevent floc discharge. Stormwater that has been chemically treated must be filtered
through BMP C251: Construction Stormwater Filtration for filtration and monitoring prior to dis-
charge.
l System discharge rates must take into account downstream conveyance integrity.
l The following equipment should be located on site in a lockable shed:
o The chemical injector.
o Secondary containment for acid, caustic, buffering compound, and treatment chemical.
o Emergency shower and eyewash.
o Monitoring equipment which consists of a pH meter and a turbidimeter.
l There are two types of systems for applying the chemical treatment process to stormwater:
the batch chemical treatment system and the flow-through chemical treatment system. See
below for further details for both types of systems.
Batch Chemical Treatment Systems
A batch chemical treatment system consists of four steps: coagulation, flocculation, clarification, and
polishing and monitoring via filtration.
Step 1: Coagulation
Coagulation is the process by which negative charges on the fine particles are disrupted. By dis-
rupting the negative charges, the fine particles are able to flocculate. Chemical addition is one
method of destabilizing the suspension, and polymers are one class of chemicals that are generally
effective. Chemicals that are used for this purpose are called coagulants. Coagulation is complete
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 397
when the suspension is destabilized by the neutralization of the negative charges. Coagulants per-
form best when they are thoroughly and evenly dispersed under relatively intense mixing. This rapid
mixing involves adding the coagulant in a manner that promotes rapid dispersion, followed by a short
time period for destabilization of the particle suspension. The particles are still very small and are not
readily separated by clarification until flocculation occurs.
Step 2: Flocculation
Flocculation is the process by which fine particles that have been destabilized bind together to form
larger particles that settle rapidly. Flocculation begins naturally following coagulation, but is
enhanced by gentle mixing of the destabilized suspension. Gentle mixing helps to bring particles in
contact with one another such that they bind and continually grow to form "flocs." As the size of the
flocs increase, they become heavier and settle.
Step 3: Clarification
The final step is the settling of the particles, or clarification. Particle density, size and shape are
important during settling. Dense, compact flocs settle more readily than less dense, fluffy flocs.
Because of this, flocculation to form dense, compact flocs is particularly important during chemical
treatment. Water temperature is important during settling. Both the density and viscosity of water are
affected by temperature; these in turn affect settling. Cold temperatures increase viscosity and dens-
ity, thus slowing down the rate at which the particles settle.
The conditions under which clarification is achieved can affect performance. Currents can affect set-
tling. Currents can be produced by wind, by differences between the temperature of the incoming
water and the water in the clarifier, and by flow conditions near the inlets and outlets. Quiescent
water, such as that which occurs during batch clarification, provides a good environment for settling.
One source of currents in batch chemical treatment systems is movement of the water leaving the
clarifier unit. Because flocs are relatively small and light, the velocity of the water must be as low as
possible. Settled flocs can be resuspended and removed by fairly modest currents.
Step 4: Filtration
After clarification, Ecology requires stormwater that has been chemically treated to be filtered and
monitored prior to discharge. The sand filtration system continually monitors the stormwater effluent
for turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the
water is returned to the untreated stormwater pond where it will begin the treatment process again.
Design and Installation of Batch Chemical Treatment Systems
A batch chemical treatment system consists of a stormwater collection system (either a temporary
diversion or the permanent site drainage system), an untreated stormwater storage pond, pumps, a
chemical feed system, treatment cells, a filtering and monitoring system, and interconnecting piping.
The batch treatment system uses a storage pond for untreated stormwater, followed by a minimum
of two lined treatment cells. Multiple treatment cells allow for clarification of chemically treated water
in one cell, while other cells are being filled or emptied. Treatment cells may be ponds or tanks.
Ponds with constructed earthen embankments greater than six feet high or which impound more
than 10 acre-feet are subject to the Washington Dam Safety Regulations (Chapter 173-175 WAC).
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 398
See BMP D.1: Detention Ponds for more information regarding dam safety considerations for
ponds.
Stormwater is collected at interception point(s) on the site and is diverted by gravity or by pumping to
an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater
is stored until treatment occurs. It is important that the storage pond is large enough to provide
adequate storage.
The first step in the treatment sequence is to check the pH of the stormwater in the untreated storm-
water storage pond. The pH is adjusted by the application of carbon dioxide or a base until the storm-
water in the untreated storage pond is within the desired pH range, 6.5 to 8.5. When used, carbon
dioxide is added immediately downstream of the transfer pump. Typically sodium bicarbonate (bak-
ing soda) is used as a base, although other bases may be used. When needed, base is added dir-
ectly to the untreated stormwater storage pond. The stormwater is recirculated with the treatment
pump to provide mixing in the storage pond. Initial pH adjustments should be based on daily bench
tests. Further pH adjustments can be made at any point in the process. See BMP C252: Treating
and Disposing of High pH Water for more information on pH adjustments as a part of chemical treat-
ment.
Once the stormwater is within the desired pH range (which is dependant on the coagulant being
used), the stormwater is pumped from the untreated stormwater storage pond to a lined treatment
cell as a coagulant is added. The coagulant is added upstream of the pump to facilitate rapid mixing.
The water is kept in the lined treatment cell for clarification. In a batch mode process, clarification typ-
ically takes from 30 minutes to several hours. Prior to discharge, samples are withdrawn for analysis
of pH, coagulant concentration, and turbidity. If these levels are acceptable, the treated water is with-
drawn, filtered, and discharged.
Several configurations have been developed to withdraw treated water from the treatment cell. The
original configuration is a device that withdraws the treated water from just beneath the water sur-
face using a float with adjustable struts that prevent the float from settling on the cell bottom. This
reduces the possibility of picking up floc from the bottom of the cell. The struts are usually set at a min-
imum clearance of about 12 inches; that is, the float will come within 12 inches of the bottom of the
cell. Other systems have used vertical guides or cables which constrain the float, allowing it to drift up
and down with the water level. More recent designs have an H-shaped array of pipes, set on the hori-
zontal.This scheme provides for withdrawal from four points rather than one. This configuration
reduces the likelihood of sucking settled solids from the bottom. It also reduces the tendency for a vor-
tex to form. Inlet diffusers, a long floating or fixed pipe with many small holes in it, are also an option.
Safety is a primary concern. Design should consider the hazards associated with operations, such
as sampling. Facilities should be designed to reduce slip hazards and drowning. Tanks and ponds
should have life rings, ladders, or steps extending from the bottom to the top.
Sizing Batch Chemical Treatment Systems
Chemical treatment systems must be designed to control the velocity and peak volumetric flow rate
that is discharged from the system and consequently the project site. See Element 3: Control Flow
Rates for further details on this requirement.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 399
The total volume of the untreated stormwater storage pond and treatment cells must be large
enough to treat stormwater that is produced during multiple day storm events. It is recommended
that at a minimum the untreated stormwater storage pond be sized to hold 1.5 times the volume of
runoff generated from the site during the 10-year, 24-hour storm event. Bypass should be provided
around the chemical treatment system to accommodate extreme storm events. Runoff volume shall
be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case
land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases,
this would be the land cover conditions just prior to final landscaping).
Primary settling should be encouraged in the untreated stormwater storage pond. A forebay with
access for maintenance may be beneficial.
There are two opposing considerations in sizing the treatment cells. A larger cell is able to treat a lar-
ger volume of water each time a batch is processed. However, the larger the cell, the longer the time
required to empty the cell. A larger cell may also be less effective at flocculation and therefore
require a longer settling time. The simplest approach to sizing the treatment cell is to multiply the
allowable discharge flow rate (as determined by the guidance in Element 3: Control Flow Rates)
times the desired drawdown time. A 4-hour drawdown time allows one batch per cell per 8-hour
work period, given 1 hour of flocculation followed by two hours of settling.
See BMP C251: Construction Stormwater Filtration for details on sizing the filtration system at the
end of the batch chemical treatment system.
If the chemical treatment system design does not allow you to discharge at the rates as required by
Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the
planned development, the discharge from the chemical treatment system may be directed to the per-
manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge
(including water passing through the treatment system and stormwater bypassing the treatment sys-
tem) will be directed into the permanent Flow Control BMP. If site constraints make locating the
untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to
serve as the untreated stormwater storage pond and the post-treatment temporary flow control
pond. A berm or barrier must be used in this case so the untreated water does not mix with the
treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow
control must be achieved. The designer must document in the Construction SWPPP how the per-
manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements
of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified
for temporary construction flow control purposes, the construction of the permanent Flow Control
BMP must be finalized, as designed for its permanent function, at project completion.
Flow-Through Chemical Treatment Systems
Background on Flow-Through Chemical Treatment Systems
A flow-through chemical treatment system adds a sand filtration component to the batch chemical
treatment system's treatment train following flocculation. The coagulant is added to the stormwater
upstream of the sand filter so that the coagulation and flocculation step occur immediately prior to the
filter. The advantage of a flow-through chemical treatment system is the time saved by immediately
filtering the water, as opposed to waiting for the clarification process necessary in a batch chemical
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treatment system. See BMP C251: Construction Stormwater Filtration for more information on fil-
tration.
Design and Installation of Flow-Through Chemical Treatment Systems
At a minimum, a flow-through chemical treatment system consists of a stormwater collection system
(either a temporary diversion or the permanent site drainage system), an untreated stormwater stor-
age pond, and a chemically enhanced sand filtration system.
As with a batch treatment system, stormwater is collected at interception point(s) on the site and is
diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated storm-
water holding area. The stormwater is stored until treatment occurs. It is important that the holding
pond be large enough to provide adequate storage.
Stormwater is then pumped from the untreated stormwater storage pond to the chemically
enhanced sand filtration system where a coagulant is added. Adjustments to pH may be necessary
before coagulant addition. The sand filtration system continually monitors the stormwater effluent for
turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the
water is returned to the untreated stormwater pond where it will begin the treatment process again.
Sizing Flow-Through Chemical Treatment Systems
Refer to BMP C251: Construction Stormwater Filtration for sizing requirements of flow-through
chemical treatment systems.
Factors Affecting the Chemical Treatment Process
Coagulants
Cationic polymers can be used as coagulants to destabilize negatively charged turbidity particles
present in natural waters, wastewater and stormwater. Polymers are large organic molecules that
are made up of subunits linked together in a chain-like structure. Attached to these chain-like struc-
tures are other groups that carry positive or negative charges, or have no charge. Polymers that
carry groups with positive charges are called cationic, those with negative charges are called
anionic, and those with no charge (neutral) are called nonionic. In practice, the only way to determ-
ine whether a polymer is effective for a specific application is to perform preliminary or on-site test-
ing.
Aluminum sulfate (alum) can also be used as a coagulant, as this chemical becomes positively
charged when dispersed in water.
Polymers are available as powders, concentrated liquids, and emulsions (which appear as milky
liquids). The latter are petroleum based, which are not allowed for construction stormwater treat-
ment. Polymer effectiveness can degrade with time and also from other influences. Thus, man-
ufacturers' recommendations for storage should be followed. Manufacturer’s recommendations
usually do not provide assurance of water quality protection or safety to aquatic organisms. Con-
sideration of water quality protection is necessary in the selection and use of all polymers.
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Application
Application of coagulants at the appropriate concentration or dosage rate for optimum turbidity
removal is important for management of chemical cost, for effective performance, and to avoid
aquatic toxicity. The optimum dose in a given application depends on several site-specific features.
Turbidity of untreated water can be important with turbidities greater than 5,000 NTU. The surface
charge of particles to be removed is also important. Environmental factors that can influence dosage
rate are water temperature, pH, and the presence of constituents that consume or otherwise affect
coagulant effectiveness. Laboratory experiments indicate that mixing previously settled sediment
(floc sludge) with the untreated stormwater significantly improves clarification, therefore reducing
the effective dosage rate. Preparation of working solutions and thorough dispersal of coagulants in
water to be treated is also important to establish the appropriate dosage rate.
For a given water sample, there is generally an optimum dosage rate that yields the lowest residual
turbidity after settling. When dosage rates below this optimum value (underdosing) are applied,
there is an insufficient quantity of coagulant to react with, and therefore destabilize, all of the turbidity
present. The result is residual turbidity (after flocculation and settling) that is higher than with the
optimum dose. Overdosing, application of dosage rates greater than the optimum value, can also
negatively impact performance. Like underdosing, the result of overdosing is higher residual turbidity
than that with the optimum dose.
Mixing
The G-value, or just "G", is often used as a measure of the mixing intensity applied during coagu-
lation and flocculation. The symbol G stands for “velocity gradient”, which is related in part to the
degree of turbulence generated during mixing. High G-values mean high turbulence, and vice versa.
High G-values provide the best conditions for coagulant addition. With high G's, turbulence is high
and coagulants are rapidly dispersed to their appropriate concentrations for effective destabilization
of particle suspensions.
Low G-values provide the best conditions for flocculation. Here, the goal is to promote formation of
dense, compact flocs that will settle readily. Low G's provide low turbulence to promote particle col-
lisions so that flocs can form. Low G's generate sufficient turbulence such that collisions are effective
in floc formation, but do not break up flocs that have already formed.
pH Adjustment
The pH must be in the proper range for the coagulants to be effective, which is typically 6.5 to 8.5. As
polymers tend to lower the pH, it is important that the stormwater have sufficient buffering capacity.
Buffering capacity is a function of alkalinity. Without sufficient alkalinity, the application of the polymer
may lower the pH to below 6.5. A pH below 6.5 not only reduces the effectiveness of the polymer as
a coagulant, but it may also create a toxic condition for aquatic organisms. Stormwater may not be
discharged without readjustment of the pH to above 6.5. The target pH should be within 0.2 stand-
ard units of the receiving water's pH.
Experience gained at several projects in the City of Redmond has shown that the alkalinity needs to
be at least 50 mg/L to prevent a drop in pH to below 6.5 when the polymer is added.
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Maintenance Standards
Monitoring
At a minimum, the following monitoring shall be conducted. Test results shall be recorded on a daily
log kept on site. Additional testing may be required by the NPDES permit based on site conditions.
l Operational Monitoring
o Total volume treated and discharged.
o Flow must be continuously monitored and recorded at not greater than 15-minute inter-
vals.
o Type and amount of chemical used for pH adjustment.
o Type and amount of coagulant used for treatment.
o Settling time.
l Compliance Monitoring
o Influent and effluent pH, flocculent chemical concentration, and turbidity must be con-
tinuously monitored and recorded at not greater than 15-minute intervals.
o pH and turbidity of the receiving water.
l Biomonitoring
o Treated stormwater must be non-toxic to aquatic organisms. Treated stormwater must
be tested for aquatic toxicity or residual chemicals. Frequency of biomonitoring will be
determined by Ecology.
o Residual chemical tests must be approved by Ecology prior to their use.
o If testing treated stormwater for aquatic toxicity, you must test for acute (lethal) toxicity.
Bioassays shall be conducted by a laboratory accredited by Ecology, unless otherwise
approved by Ecology. Acute toxicity tests shall be conducted per the CTAPE protocol
and Appendix G of Whole Effluent Toxicity Testing Guidance and Test Review Criteria
(Marshall, 2016).
Discharge Compliance
Prior to discharge, treated stormwater must be sampled and tested for compliance with pH, floc-
culent chemical concentration, and turbidity limits. These limits may be established by the Con-
struction Stormwater General Permit or a site-specific discharge permit. Sampling and testing for
other pollutants may also be necessary at some sites. pH must be within the range of 6.5 to 8.5 stand-
ard units and not cause a change in the pH of the receiving water by more than 0.2 standard units.
Treated stormwater samples and measurements shall be taken from the discharge pipe or another
location representative of the nature of the treated stormwater discharge. Samples used for determ-
ining compliance with the water quality standards in the receiving water shall not be taken from the
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treatment pond prior to decanting. Compliance with the water quality standards is determined in the
receiving water.
Operator Training
Each project site using chemical treatment must have a trained operator who is certified for oper-
ation of an Enhanced Chemical Treatment system. The operator must be trained and certified by an
organization approved by Ecology. Organizations approved for operator training are found at the fol-
lowing website:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee-
guidance-resources/Contaminated-water-on-construction-sites
Sediment Removal and Disposal
l Sediment shall be removed from the untreated stormwater storage pond and treatment cells
as necessary. Typically, sediment removal is required at least once during a wet season and
at the decommissioning of the chemical treatment system. Sediment remaining in the cells
between batches may enhance the settling process and reduce the required chemical
dosage.
l Sediment that is known to be non-toxic may be incorporated into the site away from drain-
ages.
BMP C251: Construction Stormwater Filtration
Purpose
Filtration removes sediment from runoff originating from disturbed areas of the site.
Conditions of Use
Traditional Construction Stormwater BMPs used to control soil erosion and sediment loss from con-
struction sites may not be adequate to ensure compliance with the water quality standard for tur-
bidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove
sediment as small as fine silt (0.5 µm). The reduction in turbidity will be dependent on the particle
size distribution of the sediment in the stormwater. In some circumstances, sedimentation and fil-
tration may achieve compliance with the water quality standard for turbidity.
The use of construction stormwater filtration does not require approval from Ecology as long as treat-
ment chemicals are not used. Filtration in conjunction with BMP C250: Construction Stormwater
Chemical Treatment requires testing under the Chemical Technology Assessment Protocol – Eco-
logy (CTAPE) before it can be initiated. Approval from Ecology must be obtained at each site where
chemical use is proposed prior to use. See https://-
fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of the Request for
Chemical Treatment form.
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Design and Installation Specifications
Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow.
Rapid filtration systems are the typical system used for water and wastewater treatment. They can
achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have auto-
matic backwash systems to remove accumulated solids.
Slow filtration systems have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do
not have backwash systems. Slow filtration systems have generally been used as post construction
BMPs to treat stormwater (see V-6 Filtration BMPs). Slow filtration is mechanically simple in com-
parison to rapid filtration, but requires a much larger filter area.
Filter Types and Efficiencies
Sand media filters are available with automatic backwashing features that can filter to 50 µm particle
size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to
0.5 µm. Filters should be sequenced from the largest to the smallest pore opening. Sediment
removal efficiency will be related to particle size distribution in the stormwater.
Treatment Process and Description
Stormwater is collected at interception point(s) on the site and diverted to an untreated stormwater
sediment pond or tank for removal of large sediment, and storage of the stormwater before it is
treated by the filtration system. In a rapid filtration system, the untreated stormwater is pumped from
the pond or tank through the filtration media. Slow filtration systems are designed using gravity to
convey water from the pond or tank to and through the filtration media.
Sizing
Filtration treatment systems must be designed to control the velocity and peak volumetric flow rate
that is discharged from the system and consequently the project site. See Element 3: Control Flow
Rates for further details on this requirement.
The untreated stormwater storage pond or tank should be sized to hold 1.5 times the volume of run-
off generated from the site during the 10-year, 24-hour storm event, minus the filtration treatment
system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the filtration
treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ft2. Other
hydraulic loading rates may be more appropriate for other systems. Bypass should be provided
around the filtration treatment system to accommodate extreme storm events. Runoff volume shall
be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case
land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases,
this would be the land cover conditions just prior to final landscaping).
If the filtration treatment system design does not allow you to discharge at the rates as required by
Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the
planned development, the discharge from the filtration treatment system may be directed to the per-
manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge
(including water passing through the treatment system and stormwater bypassing the treatment
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system) will be directed into the permanent Flow Control BMP. If site constraints make locating the
untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to
serve as the untreated stormwater storage pond and the post-treatment temporary flow control
pond. A berm or barrier must be used in this case so the untreated water does not mix with the
treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow
control must be achieved. The designer must document in the Construction SWPPP how the per-
manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements
of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified
for temporary construction flow control purposes, the construction of the permanent Flow Control
BMP must be finalized, as designed for its permanent function, at project completion.
Maintenance Standards
l Rapid sand filters typically have automatic backwash systems that are triggered by a pre-set
pressure drop across the filter. If the backwash water volume is not large or substantially more
turbid than the untreated stormwater stored in the holding pond or tank, backwash return to
the untreated stormwater pond or tank may be appropriate. However, other means of treat-
ment and disposal may be necessary.
l Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged.
l Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically,
sediment removal is required once or twice during a wet season and at the decommissioning
of the ponds.
l Disposal of filtration equipment must comply with applicable local, state, and federal reg-
ulations.
BMP C252: Treating and Disposing of High pH Water
Purpose
When pH levels in stormwater rise above 8.5, it is necessary to lower the pH levels to the acceptable
range of 6.5 to 8.5 prior to discharge to surface or ground water. A pH level range of 6.5 to 8.5 is typ-
ical for most natural watercourses, and this neutral pH range is required for the survival of aquatic
organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may
become stressed and may die.
Conditions of Use
l The water quality standard for pH in Washington State is in the range of 6.5 to 8.5. Storm-
water with pH levels exceeding water quality standards may be either neutralized on site or
disposed of to a sanitary sewer or concrete batch plant with pH neutralization capabilities.
l Neutralized stormwater may be discharged to surface waters under the Construction Storm-
water General permit.
l Neutralized process water such as concrete truck wash-out, hydro-demolition, or saw-cutting
slurry must be managed to prevent discharge to surface waters. Any stormwater
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contaminated during concrete work is considered process wastewater and must not be dis-
charged to waters of the State or stormwater collection systems.
l The process used for neutralizing and/or disposing of high pH stormwater from the site must
be documented in the Construction Stormwater Pollution Prevention Plan.
Causes of High pH
High pH at construction sites is most commonly caused by the contact of stormwater with poured or
recycled concrete, cement, mortars, and other Portland cement or lime containing construction
materials. (See BMP C151: Concrete Handling for more information on concrete handling pro-
cedures). The principal caustic agent in cement is calcium hydroxide (free lime).
Calcium hardness can contribute to high pH values and cause toxicity that is associated with high pH
conditions. A high level of calcium hardness in waters of the state is not allowed. Ground water stand-
ard for calcium and other dissolved solids in Washington State is less than 500 mg/l.
Treating High pH Stormwater by Carbon Dioxide Sparging
Advantages of Carbon Dioxide Sparging
l Rapidly neutralizes high pH water.
l Cost effective and safer to handle than acid compounds.
l CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels.
l Material is readily available.
The Chemical Process of Carbon Dioxide Sparging
When carbon dioxide (CO2) is added to water (H2O), carbonic acid (H2CO3) is formed which can
further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below:
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reac-
tion as well. The colder the water temperature is, the slower the reaction occurs. The warmer the
water temperature is, the quicker the reaction occurs. Most construction applications in Washington
State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous.
The Treatment Process of Carbon Dioxide Sparging
High pH water may be treated using continuous treatment, continuous discharge systems. These
manufactured systems continuously monitor influent and effluent pH to ensure that pH values are
within an acceptable range before being discharged. All systems must have fail safe automatic shut
off switches in the event that pH is not within the acceptable discharge range. Only trained operators
may operate manufactured systems. System manufacturers often provide trained operators or train-
ing on their devices.
The following procedure may be used when not using a continuous discharge system:
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1. Prior to treatment, the appropriate jurisdiction should be notified in accordance with the reg-
ulations set by the jurisdiction.
2. Every effort should be made to isolate the potential high pH water in order to treat it separately
from other stormwater on-site.
3. Water should be stored in an acceptable storage facility, detention pond, or containment cell
prior to pH treatment.
4. Transfer water to be treated for pH to the pH treatment structure. Ensure that the pH treat-
ment structure size is sufficient to hold the amount of water that is to be treated. Do not fill the
pH treatment structure completely, allow at least 2 feet of freeboard.
5. The operator samples the water within the pH treatment structure for pH and notes the clarity
of the water. As a rule of thumb, less CO2 is necessary for clearer water. The results of the
samples and water clarity observations should be recorded.
6. In the pH treatment structure, add CO2 until the pH falls into the range of 6.9-7.1. Adjusting
pH to within 0.2 pH units of receiving water (background pH) is recommended. It is unlikely
that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas
should be introduced to the water using a carbon dioxide diffuser located near the bottom of
the pH treatment structure, this will allow carbon dioxide to bubble up through the water and
diffuse more evenly.
7. Slowly discharge the water, making sure water does not get stirred up in the process. Release
about 80% of the water from the pH treatment structure leaving any sludge behind. If turbidity
remains above the maximum allowable, consider adding filtration to the treatment train. See
BMP C251: Construction Stormwater Filtration.
8. Discharge treated water through a pond or drainage system.
9. Excess sludge needs to be disposed of properly as concrete waste. If several batches of
water are undergoing pH treatment, sludge can be left in the treatment structure for the next
batch treatment. Dispose of sludge when it fills 50% of the treatment structure volume.
10. Disposal must comply with applicable local, state, and federal regulations.
Treating High pH Stormwater by Food Grade Vinegar
Food grade vinegar that meets FDA standards may be used to neutralize high pH water. Food
grade vinegar is only 4% to 18% acetic acid with the remainder being water. Food grade vinegar
may be used if dosed just enough to lower pH sufficiently. Use a treatment process as described
above for CO2 sparging, but add food grade vinegar instead of CO2.
This treatment option for high pH stormwater does not apply to anything but food grade vinegar.
Acetic acid does not equal vinegar. Any other product or waste containing acetic acid must go
through the evaluation process in Appendix G of Whole Effluent Toxicity Testing Guidance and Test
Review Criteria (Marshall, 2016).
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Disposal of High pH Stormwater
Sanitary Sewer Disposal
Local sewer authority approval is required prior to disposal via the sanitary sewer.
Concrete Batch Plant Disposal
l Only permitted facilities may accept high pH water.
l Contact the facility to ensure they can accept the high pH water.
Maintenance Standards
Safety and materials handling:
l All equipment should be handled in accordance with OSHA rules and regulations.
l Follow manufacturer guidelines for materials handling.
Each operator should provide:
l A diagram of the monitoring and treatment equipment.
l A description of the pumping rates and capacity the treatment equipment is capable of treat-
ing.
Each operator should keep a written record of the following:
l Client name and phone number.
l Date of treatment.
l Weather conditions.
l Project name and location.
l Volume of water treated.
l pH of untreated water.
l Amount of CO2 or food grade vinegar needed to adjust water to a pH range of 6.9-7.1.
l pH of treated water.
l Discharge point location and description.
A copy of this record should be given to the client/contractor who should retain the record for three
years.
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Page | 34
Appendix D – Site Inspection Form
Construction Stormwater Site Inspection Form
Page 1
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/ transparency 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
Construction Stormwater Site Inspection Form
Page 2
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?
Construction Stormwater Site Inspection Form
Page 3
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?
Construction Stormwater Site Inspection Form
Page 4
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
Construction Stormwater Site Inspection Form
Page 5
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:
RENTON PARK ELEMENTARY SCHOOL – ADA IMPROVEMENTS
19
APPENDIX C
ENGINEERING CALCULATIONS
MGS Flood Calculation for
Developed 100-yr Storm
Draining to CB and New 6"
Storm Pipe = 0.08 cfs; OK
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.58
Program License Number: 201910001
Project Simulation Performed on: 04/13/2023 3:32 PM
Report Generation Date: 04/13/2023 3:37 PM
—————————————————————————————————
Input File Name: Renton Park_Conveyance Flow Calc_230413.fld
Project Name: Renton Park ES ADA Improvements
Analysis Title: Conveyance Flow Calc - 6" Pipe
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 5
Extended Precipitation Time Series Selected
Full Period of Record Available used for Routing
Climatic Region Number: 16
Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961044 Puget East 44 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : Ecology Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.050 0.050
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 0.050 0.050
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Predeveloped ----------
-------Area (Acres) --------
A/B, Forest, Steep 0.050
----------------------------------------------
CONVEYANCE CALCULATION - 100 YR STORM EVENT
Subbasin Total 0.050
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Post Developed ----------
-------Area (Acres) --------
ROADS/FLAT 0.050
----------------------------------------------
Subbasin Total 0.050
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: Outflow
Link Type: Copy
Downstream Link: None
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Predeveloped 15.621
_____________________________________
Total: 15.621
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
CONVEYANCE CALCULATION - 100 YR STORM EVENT
-----------------------------------------------------------------------------------------------
Subbasin: Post Developed 0.000
Link: Outflow 0.000
_____________________________________
Total: 0.000
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.099 ac-ft/year, Post Developed: 0.000 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: Outflow **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 25.07
Inflow Volume Including PPT-Evap (ac-ft): 25.07
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 25.07
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Predeveloped
Scenario Postdeveloped Compliance Link: Outflow
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 1.138E-04 2-Year 2.620E-02
5-Year 1.198E-04 5-Year 3.374E-02
10-Year 1.209E-04 10-Year 4.282E-02
25-Year 4.012E-04 25-Year 5.128E-02
50-Year 4.726E-04 50-Year 6.426E-02
100-Year 9.924E-04 100-Year 7.773E-02
200-Year 1.140E-03 200-Year 9.388E-02
500-Year 1.319E-03 500-Year 0.115
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
CONVEYANCE CALCULATION - 100 YR STORM EVENT