SWPPP (6)Construction Stormwater
Pollution Prevention Plan
(SWPPP)
for
Rainier View Estates
9910 Durant St. SE
Yelm, WA 98597
TPN 21724420501
City of Yelm Project No. ________
Olympic Engineering Project No. 20046
February 6, 2025
Prepared by:
PO Box 12690
Olympia WA 98508
360.705.2474
www.olyeng.com
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Certified Erosion and Sediment Control Lead (CESCL)
_______________________________
_______________________________
_______________________________
_______________________________
Civil Engineer
Chris Merritt, PE
Olympic Engineering, Inc.
PO Box 12690
Olympia, WA 98508
(360) 705-2474
chris@olyeng.com
Applicant
C & E Developments, LLC
Ashlynne Solseth
PO Box 2983
Yelm, WA 98597
(360) 400-0432
cedevelopment05@gmail.com
Contractor
_______________________________
_______________________________
_______________________________
_______________________________
This SWPPP has been prepared by Olympic Engineering based on our estimate of anticipated site
conditions throughout construction along with anticipated construction methods and sequencing used
by the contractor. The BMPs suggested in this SWPPP are simply suggestions and the contractor
and/or owner is responsible for implementing all BMPs necessary to minimize and prevent erosion
and sedimentation throughout construction and through final site stabilization.
The owner retains the ultimate responsibility for environmental protection at the site and for ensuring
the project is in compliance at all times.
2/6/2025
“I hereby state that this Construction SWPPP for the Rainier
View Estates project has been prepared by me or under my
supervision and meets the standard of care and expertise
which is usual and customary in this community for
professional engineers. I understand that the City of Yelm
does not and will not assume liability for the sufficiency,
suitability, or performance of drainage facilities designed by
me."
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Objective
To control erosion and prevent sediment and other pollutants from leaving the site during the
construction phase of a project. To have fully functional stormwater facilities and BMPs for the
developed site upon completion of construction.
The Thirteen Required Elements are listed and addressed below.
Project Overview
Project Description
The proposal is to subdivide a 5.28-acre parcel into 23 residential lots with associated roadway, storm
drainage, and public and private utility improvements. 19 lots will contain single-family residences and
4 lots will contain duplexes for 27 total units. The parcel is zoned R-4.
Access will be taken from both Durant Drive SE to the east and by an unnamed roadway to the north,
creating a looped connection between Tahoma Blvd. SE and Longmire St. SE.
A 0.78-acre open space and stormwater tract is proposed in the west and southwest corner of the site.
Stormwater Improvements
All disturbed, roadside planter, stormwater dispersion, and individual lot lawn/landscape areas will
contain soils meeting the Post-Construction Soil Quality and Depth (BMP T5.13) requirements.
Stormwater runoff from the individual lot roof areas will be routed to downspout infiltration trenches
(BMP T5.10A) for detention and 100% infiltration. These will be sized per prescriptive sizing methods
at the time of building permit application.
Stormwater runoff from the new public roadways will be routed to a bioretention facility (BMP T7.30).
Stormwater runoff from the emergency vehicle turnaround area will be sheet flow dispersed (BMP
T5.12) onto adjacent lawn/landscape areas with soils meeting BMP T5.13 requirements.
Stormwater runoff from the individual lot driveway, walkway, and patio areas will be sheet flow
dispersed (BMP T5.12) onto adjacent lawn/landscape areas with soils meeting BMP T5.13
requirements.
Project Areas
Project Area: 5.279 acres
Proposed Hard Surface Area: 0.791 acres
Proposed Area to be Disturbed: 5.1 acres
Proposed Grading Quantities: 6,675 cy cut/fill (source of any off-site fill TBD)
Construction Schedule and Phasing
The site work will be completed in one phase. The following estimated timeframes are subject to
change based on the plan approval timeframe, contractor’s schedule, etc.
Mark Clearing Limits May 2025 – May 2025
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Establish Construction Access May 2025 – May 2025
Install Erosion and Sediment Controls May 2025 – June 2025
Demolition/Clearing/Grading June 2025 – June 2025
Utility Construction July 2025 – September 2025
Asphalt/Concrete Paving September 2025 – October 2025
Building Construction Unknown
Existing Conditions
Site vegetation consists mainly of field grass with some brush. The subject parcels and surrounding
areas are generally flat. A slight ridge runs east to west through the middle portion of the parcel and
site topography generally slopes down from this ridge to the south, west, and north. The lowest
elevation is in the southwest corner of the project site.
No fuel tanks were located during a site inspection or during the soils evaluation work. Olympic
Engineering reviewed the latest “LUST” list (Leaking Underground Storage Tank) and found no listing
for the subject site.
There are no known on-site wells or off-site wells within 200-feet of this project’s boundaries.
There does not appear to be any noticeable stormwater run-on from adjacent parcels.
Critical Areas
There are no known critical areas (i.e. wetlands, landslide hazards, streams, etc.) located on-site or
within the immediate vicinity of the site based on review of Thurston County critical areas maps and a
site visit.
The project is located within a Category I Critical Aquifer Recharge Area (CARA) and a 10 -year time
of travel zone of a wellhead protection area.
Per FEMA FIRM Map Panel #53067C0353F, the site and surrounding areas are within Zone X. The
Zone X designation signifies areas of minimal flood hazard.
Soils
The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston County classifies the
on-site soils as Spanaway Gravely Sandy Loam (HSG A).
Per the Geotechnical Consultation report prepared by Quality Geo NW (see Appendix) the soils consist
of topsoil overlying gravel with silt and sand to depths of 10’ below -grade. Per the Soils Report
prepared by Parnell Engineering (see appendix), gravelly loam overlying an extremely gravelly and
cobbled coarse-fine sand were encountered to 14.3’ below-grade.
Seasonal groundwater was encountered in one test pit at 13.6’ below-grade per the Parnell
Engineering soils report. This test pit was located in the lowest point of the site, in the southwest
corner. The proposed bioretention facility bottom will be approximately 10.8’ above the seasonal high
groundwater elevation.
Design Calculations
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See the Drainage Design Report for sizing calculations of the permanent stormwater BMPs (e.g
bioretention pond).
The sediment pond surface area was sized per BMP C241 in Volume II of the Ecology Stormwater
Management Manual for Western Washington (SMMWW), 2024 ed.. A 2-year flow rate of 0.51 cfs
results in a pond surface area requirement of 1,060 sf (2,080 sf per 1 cfs inflow = 2,080 sf x 0.51 cfs
= 1,060 sf). The civil plans encourage the contractor to utilize the entire bioretention pond area for a
sediment pond since no emergency overflow is being provided.
Adjacent Areas
The project site is bordered by single-family residential to the south, east, and west, and by recently
developed apartment buildings to the north.
Financial/Ownership Responsibilities
The HOA will be responsible for any bonds and/or other financial securities as required by the City of
Yelm.
Supplemental Guidelines
If a Construction SWPPP is found to be inadequate (with respect to erosion and sediment control
requirements), then the Plan Approval Authority within the City shall require that other BMPs be
implemented, as appropriate.
The Plan Approval Authority may allow development of generic Construction SWPPP’s that apply to
commonly conducted public road activities, such as road surface replacement, that trigger this core
requirement. They may also develop an abbreviated SWPPP format for project sites that will disturb
less than 1 acre.
Based on the information provided and/or local weather conditions, the local permitting authority may
expand or restrict the seasonal limitation on site disturbance. The local permitting authority shall take
enforcement action - such as a notice of violation, administrative order, penalty, or stop-work order
under the following circumstances:
• If, during the course of any construction activity or soil disturbance during the seasonal
limitation period, sediment leaves the construction site causing a violation of the surface water
quality standard; or
• If clearing and grading limits or erosion and sediment control measures shown in the approved
plan are not maintained.
General Requirements
Clearing and grading activities for developments shall be permitted only if conducted pursuant to an
approved site development plan (e.g., subdivision approval) that establishes permitted areas of
clearing, grading, cutting, and filling. These permitted clearing and grading areas and any other areas
required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree
retention areas shall be delineated on the site plans and the development site.
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The SWPPP shall be implemented beginning with initial land disturbance through final stabilization.
Sediment and Erosion control BMPs shall be consistent with the BMPs contained in Volume II of the
Ecology Stormwater Management Manual for Western Washington (SMMWW), 2024 ed.
Seasonal Work Limitations - From October 1 through April 30, clearing, grading, and other soil
disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority
that silt-laden runoff will be prevented from leaving the site. See Element #12 below for additional
information.
Project Requirements - Construction SWPPP Elements
In most cases, all of the following elements shall apply and be implemented throughout construction.
Self-contained sites (discharges only to groundwater) must comply with all elements with the exception
of Element 3: Control Flow Rates.
The suggested BMPs underlined and in bold are proposed for use in all phases of construction.
Additional BMPs shall be implemented as necessary to minimize and prevent erosion and
sedimentation throughout construction. See Chapter 5 of the SDM for reference. All BMPs shall be
maintained until final site stabilization.
Element #1: Preserve Vegetation/Mark Clearing Limits
• Before beginning land disturbing activities, including clearing and grading, clearly mark all
clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the
construction area.
• Retain the duff layer, native topsoil, and natural vegetation in an undisturbed state to the
maximum degree practicable.
• Plastic, metal, fabric fence, or other physical barriers may be used to mark the clearing limits.
Note the difference between the practical use and proper installation of BMP C233: Silt Fence,
and the proper use of BMP C103: High-Visibility Fence.
• If it is not practical to retain the duff layer in place, then stockpile it on site, cover it to prevent
erosion, and replace it immediately when you finish disturbing the site. See the
postconstruction soil quality and depth BMP in the SMMWW, for more information.
Suggested BMPs:
o BMP C101: Preserving Natural Vegetation
o BMP C102: Buffer Zones
o BMP C103: High Visibility Plastic Fence.
o BMP C233: Silt Fence
Element #2: Establish Construction Access
• Limit construction vehicle access and exit to one route, if possible. Minimize construction site
access points along linear projects, such as roadways.
• Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to
minimize tracking of sediment onto roads and accesses. o Other equivalent BMPs may include
Foreign Object Debris System (FODS) trackout control mats and Track CleanTM Construction
Entrance Plates.
• Locate wheel wash or tire baths on site if the stabilized construction access is not effective in
preventing tracking sediment onto roads/accesses.
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• Sediment must not be tracked off-site. If sediment is tracked off-site, clean the affected
roadway/access thoroughly at the end of each day, or more frequently as necessary (for
example, during wet weather). Remove sediment from roads by shoveling, sweeping, or
picking up and transporting the sediment to a controlled sediment disposal area.
• Conduct street washing only after sediment is removed in accordance with the above bullet.
• Control street wash wastewater by pumping back on site to an approved infiltration BMP, or
otherwise preventing it from discharging into systems tributary to the City municipal separated
storm sewer system (MS4), wetlands, or waters of the State. Options include discharge to the
sanitary sewer, or discharge to an approved off-site treatment system. Note that a permit may
need to be obtained by the City depending on the nature of the discharge.
Suggested BMPs:
o BMP C105: Stabilized Construction Access
o BMP C106: Wheel Wash
o BMP C107: Construction Road/Parking Area Stabilization
Element #3: Control Flow Rates
• Protect properties and waterways downstream from development sites from erosion and
the associated discharge of turbid waters due to increases in the velocity and peak
volumetric flow rate of stormwater runoff from the project site.
• Where necessary to comply with the bullet above, construct stormwater infiltration or
detention BMPs as one of the first steps in grading. Ensure that detention BMPs function
properly before constructing site improvements (e.g., impervious surfaces).
• Sites that must implement flow control for the developed site condition must also control
stormwater release rates during construction. Construction site stormwater discharges
must meet the discharge requirements listed in Chapter 2, Section 2.2.7.
• This restriction on release rates can affect the size of the storage pond and treatment cells.
The City may require designs that provide additional or different stormwater flow control if
necessary to address local conditions or to protect properties and waterways downstream
from high flow impacts.
• If permanent infiltration BMPs are used for temporary flow control during construction,
protect these BMPs from siltation during the construction phase.
• Conduct downstream analysis if changes in flows could impair or alter conveyance systems,
streambanks, bed sediment, or aquatic habitat. See Chapter 1 for potential off-site analysis
guidelines.
• Even gently sloped areas need flow controls such as BMP C235: Wattles or other energy
dissipation/filtration structures. Place dissipation BMPs closer together on steeper slopes.
These methods prevent water from building higher velocities as it flows downstream within
the construction site.
• Control structures designed for permanent detention BMPs are not appropriate for use
during construction without modification. If used during construction, modify the control
structure to allow for long-term storage of runoff and enable sediment to settle. Verify that
the BMP is sized appropriately for this purpose. Restore BMPs to their original design
dimensions, remove sediment, and install a final control structure at completion of the
project.
• Erosion has the potential to occur because of increases in the volume, velocity, and peak
flow rate of stormwater runoff from the project site. The local permitting agency may require
infiltration or detention BMP designs that provide additional or different stormwater flow
control than the designs detailed in this manual. These requirements may be necessary to
address local conditions or to protect properties and waterways downstream.
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• Velocity of water leaving the site should not exceed 3 feet/second if the discharge is to a
stream or ditch. Install velocity dissipation, such as BMP C207: Check Dams or BMP C202:
Riprap Channel Lining to ensure reduction of the flow velocity to a non-erosive level.
• If the discharge from a project site is to a municipal storm drainage system, the allowable
discharge rate may be limited by the capacity of the public system. It may be necessary to
clean the municipal storm drainage system prior to the start of the discharge to prevent
scouring solids from the drainage system. Obtain permission from the City before
discharging to the public drainage system. Ensure that no downstream pipes are
surcharged as a result of increased flows from the project site.
• If the discharge from a project site is directly to a flow control exempt receiving water (Puget
Sound or the Nisqually River) or to an infiltration BMP, there is no discharge flow limit.
Suggested BMPs:
o BMP C203: Water Bars
o BMP C207: Check Dams
o BMP C209: Outlet Protection
o BMP C235: Wattles
o BMP C240: Sediment Trap
o BMP C241: Sediment Pond (Temporary)
Element #4: Install Sediment Controls
Design, install, and maintain effective erosion controls and sediment controls to minimize the
discharge of pollutants.
• Construct sediment control BMPs (sediment ponds, traps, filters, etc.) as one of the first steps
in grading. These BMPs shall be functional before other land disturbing activities take place.
• Minimize sediment discharges from the site. The design, installation, and maintenance of
construction stormwater BMPs must address factors such as the amount, frequency, intensity,
and duration of precipitation; the nature of resulting stormwater runoff; and soil characteristics,
including the range of soil particle sizes expected to be present on the site.
• Direct stormwater runoff from disturbed areas through BMP C241: Sediment Pond
(Temporary) or other appropriate sediment removal BMP, before the runoff leaves a
construction site or before discharge to an infiltration facility. Runoff from fully stabilized areas
may be discharged without a sediment removal BMP, but must control flow rates per Element
#3: Control Flow Rates.
• Locate BMPs intended to trap sediment on site in a manner to avoid interference with the
movement of juvenile salmonids attempting to enter off-channel areas or drainages.
• Provide and maintain natural buffers around surface waters, direct stormwater to vegetated
areas to increase sediment removal and maximize stormwater infiltration, unless infeasible.
• Where feasible, design outlet structures that withdraw impounded stormwater from the surface
to avoid discharging sediment that is still suspended lower in the water column.
• Outlet structures that withdraw impounded stormwater from the surface to avoid discharging
sediment that is still suspended lower in the water column are for the construction period only.
If installing a floating pump structure, include a stopper to prevent the pump basket from hitting
the bottom of the pond.
• If a sediment trapping BMP utilizes a control structure that will also be used in a permanent
detention BMP application, the control structure must be finalized for the permanent BMP
application upon project completion.
• Install sediment controls in a manner that protects the sensitive areas and their buffers marked
in accordance with Element #1: Preserve Vegetation / Mark Clearing Limits.
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• Where feasible, direct stormwater to vegetated areas to increase sediment removal and
maximize stormwater infiltration.
• Seed and mulch earthen structures such as dams, dikes, and diversions according to the
timing indicated in Element #5: Stabilize Soils.
• Full stabilization includes concrete or asphalt paving; quarry spalls used as ditch lining; or the
use of rolled erosion products, a bonded fiber matrix product, or vegetative cover in a manner
that will fully prevent soil erosion.
• The City may inspect and approve areas fully stabilized by means other than pavement or
quarry spalls.
Suggested BMPs:
o BMP C231: Brush Barrier
o BMP C232: Gravel Filter Berm
o BMP C233: Silt Fence
o BMP C234: Vegetated Strip
o BMP C235: Wattles
o BMP C240: Sediment Trap
o BMP C241: Sediment Pond (Temporary)
o BMP C250: Construction Stormwater Chemical Treatment
o BMP C251: Construction Stormwater Filtration
Element #5: Stabilize Soils
• Stabilize exposed and unworked soils by application of effective BMPs that prevent erosion.
Applicable BMPs include, but are not limited to: temporary and permanent seeding, sodding,
mulching, plastic covering, erosion control fabrics and matting, soil application of
polyacrylamide (PAM), the early application of gravel base on areas to be paved, and dust
control.
• Full stabilization means all soil disturbing activities at the site have been completed and areas
where the soil or natural vegetative cover has been disturbed have been properly covered and
accepted to meet permanent erosion control. Permanent erosion control can include concrete
or asphalt paving; quarry spalls used as ditch lining; application of thick layers of gravel or
mulch; or vegetative cover in a manner that will fully prevent soil erosion. Where the term “fully
established” is used to describe vegetative cover or plantings, it shall be understood to mean
that healthy vegetation covers 90 percent of exposed bare soil. The application of
hydroseeding, even in conjunction with a bonded fiber matrix (BFM) or rolled erosion product,
will not be accepted as fully established permanent erosion control before the necessary
development and ground cover requirements of the plantings are met. The strong root
structures of well-established vegetation are an essential mechanism in controlling soil
erosion. The City will inspect and must approve all areas as fully stabilized before the release
of financial guarantees.
• Control stormwater volume and velocity within the site to minimize soil erosion.
• Control stormwater discharges, including both peak flow rates and total stormwater volume, to
minimize erosion at outlets and to minimize downstream channel and stream bank erosion.
• Soils must not remain exposed and unworked for more than the time periods set forth below
to prevent erosion.
o During the dry season (May 1–September 30): 7 days
o During the wet season (October 1–April 30): 2 days
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• Stabilize soils at the end of the shift before a holiday or weekend if needed based on the
weather forecast.
• Stabilize soil stockpiles from erosion; protect with sediment trapping measures; and where
possible, locate away from storm drain inlets, waterways, and drainage channels.
• Minimize the amount of soil exposed during construction activity.
• Minimize the disturbance of steep slopes.
• Minimize soil compaction and, unless infeasible, preserve topsoil.
• Soil stabilization measures must be appropriate for the time of year, site conditions, estimated
duration of use, and potential water quality impacts that stabilization agents may have on
downstream waters or groundwater.
• Ensure that gravel base used for stabilization is clean and does not contain fines or sediment.
• Prevent wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and
surface waters. Refer to BMP C140: Dust Control/
Suggested BMPs:
o BMP C120: Temporary and Permanent Seeding
o BMP C121: Mulching
o BMP C122: Nets and Blankets
o BMP C123: Plastic Covering
o BMP C124: Sodding
o BMP C125: Topsoiling/Composting
o BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection
o BMP C130: Surface Roughening
o BMP C131: Gradient Terraces
o BMP C140: Dust Control
Element #6: Protect Slopes
• Design and construct cut-and-fill slopes in a manner to minimize erosion. Applicable practices
include, but are not limited to, reducing continuous length of slope with terracing and
diversions, reducing slope steepness, and roughening slope surfaces (for example, track
walking).
• Divert off-site stormwater (run-on) or groundwater away from slopes and disturbed areas with
interceptor dikes, pipes, and/or swales. Off-site stormwater must be managed separately from
stormwater generated on the site.
• At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent
erosion.
• Temporary pipe slope drains must be sized to convey the flow rate calculated by one of the
following methods:
o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a
10-minute time step from a Type 1A, 10-year, 24-hour frequency storm
OR
o Continuous Simulation Method: The 10-year peak flow rate, as determined by an
approved continuous runoff model with a 15-minute time step.
• The hydrologic analysis must use the existing land cover condition for predicting flow rates
from tributary areas outside the project limits. For tributary areas on the project site, the
analysis must use the temporary or permanent project land cover condi tion, whichever will
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produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM)
to predict flows, bare soil areas should be modeled as “landscaped” area.
• Place excavated material on the uphill side of trenches, consistent with safety and space
considerations.
• Place check dams at regular intervals within constructed channels that are cut down a slope.
• Consider soil type and its potential for erosion.
• Stabilize soils on slopes, as specified in Element #5: Stabilize Soils.
• BMP combinations are the most effective method of protecting slopes with disturbed soils. For
example, use both BMP C121: Mulching and BMP C122: Nets and Blankets in combination.
Suggested BMPs:
o BMP C120: Temporary and Permanent Seeding
o BMP C121: Mulching
o BMP C122: Nets and Blankets
o BMP C123: Plastic Covering
o BMP C124: Sodding
o BMP C130: Surface Roughening
o BMP C131: Gradient Terraces
o BMP C200: Interceptor Dike and Swale
o BMP C201: Grass-Lined Channels
o BMP C203: Water Bars
o BMP C204: Pipe Slope Drains
o BMP C205: Subsurface Drains
o BMP C206: Level Spreader
o BMP C207: Check Dams
o BMP C208: Triangular Silt Dike (TSD).
Element #7: Protect Drain Inlets
• Protect all storm drain inlets made operable during construction so that stormwater
runoff does not enter the conveyance system without first being filtered or treated to
remove sediment.
• Clean or remove and replace inlet protection devices when sediment has filled one-third
of the available storage (unless a different standard is specified by the product
manufacturer).
• Inlets shall be inspected weekly at a minimum and daily during storm events.
• Protect all existing storm drain inlets so that stormwater runoff does not enter the
conveyance system without first being filtered or treated to remove sediment.
• Keep all approach roads clean. Do not allow sediment and street wash water to enter
storm drains without prior and adequate treatment (as defined above) unless treatment
is provided before the storm drain discharges to waters of the State.
Suggested BMPs:
o BMP C220: Inlet Protection
Element #8: Stabilize Channels and Outlets
• Design, construct, and stabilize all on-site conveyance channels to prevent erosion from the
flow rate calculated by one of the following methods:
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o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a
10-minute time step from a Type 1A 10-year, 24-hour frequency storm.
OR
o Continuous Simulation Method: The 10-year peak flow rate, as determined by an
approved continuous runoff model with a 15-minute time step.
• The hydrologic analysis must use the existing land cover condition for predicting flow rates
from tributary areas outside the project limits. For tributary areas on the project site, the
analysis must use the temporary or permanent project land cover condi tion, whichever will
produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM)
to predict flows, bare soil areas shall be modeled as “landscaped” area.
• Provide stabilization, including armoring material, adequate to prevent erosion of outlets,
adjacent stream banks, slopes, and downstream reaches at the outlets of all conveyance
systems.
• The best method for stabilizing channels is to completely line the channel with BMP C122:
Nets and Blankets first, then add BMP C207: Check Dams as necessary to function as an
anchor and to slow the flow of water.
Suggested BMPs:
o BMP C122: Nets and Blankets
o BMP C202: Riprap Channel Lining
o BMP C207: Check Dams
o BMP C209: Outlet Protection
Element #9: Control Pollutants
Design, install, implement and maintain effective pollution prevention measures to minimize the
discharge of pollutants. The project proponent must:
• Handle and dispose of all pollutants, including waste materials and demolition debris that occur
on site in a manner that does not cause contamination of stormwater. Woody debris may be
chopped and spread on site.
• Provide cover, containment, and protection from vandalism for all chemicals, liquid products,
petroleum products, and other materials that have the potential to pose a threat to human
health or the environment. On-site fueling tanks must include secondary containment.
Secondary containment means placing tanks or containers within an impervious structure
capable of containing 110 percent of the volume contained in the largest tank within the
containment structure. Double-walled tanks do not require additional secondary containment.
• Conduct maintenance, fueling, and repair of heavy equipment and vehicles using spill
prevention and control measures. Clean contaminated surfaces immediately following any spill
incident.
• Conduct oil changes, hydraulic system drain down, solvent and degreasing cleaning
operations, fuel tank drain down and removal, and other activities that may result in discharge
or spillage of pollutants to the ground or into stormwater runoff only when using spill prevention
measures, such as drip pans.
• Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that
prevents discharge to surface water, or to the sanitary sewer. For discharges to the sanitary
sewer, permits must be obtained from the City.
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• Apply fertilizers and pesticides in a manner and at application rates that will not result in loss
of chemical to stormwater runoff. Follow manufacturers’ label requirements for application
rates and procedures.
• Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources. The
sources for this contamination include, but are not limited to: recycled concrete stockpiles, bulk
cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams
generated from concrete grinding and sawing, exposed aggregate processes, dewatering
concrete vaults, concrete pumping, and mixer washout waters.
• Adjust the pH of stormwater if necessary to prevent violations of the water quality standards.
• Ensure that washout of concrete trucks is performed off-site or in designated concrete washout
areas only. Do not wash out concrete truck drums or concrete handling equipment onto the
ground, or into storm drains, open ditches, streets, or streams. Washout of small concrete
handling equipment may be disposed of in a formed area awaiting concrete where it will not
contaminate surface or ground water. Do not dump excess concrete on site, except in
designated concrete washout areas. Concrete spillage or concrete discharge directly to
ground water or surface waters of the State is prohibited. Do not wash out to formed areas
awaiting infiltration BMPs.
• Obtain written approval from Ecology before using chemical treatment other than CO2, dry
ice, or food grade vinegar to adjust pH.
• Uncontaminated water from water-only based shaft drilling for construction of building, road,
and bridge foundations may be infiltrated provided the wastewater is managed in a way that
prohibits discharge to surface waters. Prior to infiltration, water from water-only based shaft
drilling that comes into contact with curing concrete must be neutralized until pH is in the range
of 6.5 to 8.5 (su).
• Wheel wash and/or tire bath wastewater can be combined with wastewater from concrete
washout areas if the wastewaters will be properly disposed of at an off-site location or
treatment BMP.
• Do not use upland land applications for discharging wastewater from concrete washout areas.
• Clean contaminated surfaces immediately following any discharge or spill incident. Emergency
repairs may be performed on site using temporary plastic placed beneath and, if raining, over
the vehicle.
Suggested BMPs:
o BMP C151: Concrete Handling
o BMP C152: Sawcutting and Surfacing Pollution Prevention
o BMP C153: Material Delivery, Storage and Containment
o BMP C154: Concrete Washout Area
o BMP C250: Construction Stormwater Chemical Treatment
o BMP C251: Construction Stormwater Filtration
o BMP C252: Treating and Disposing of High pH Water
o See Chapter 9 – Source Control for Developed Sites
Element #10: Control Dewatering
• Discharge foundation, vault, and trench dewatering water, which have similar characteristics
to stormwater runoff at the site, into a controlled conveyance system before discharge to BMP
C240: Sediment Trap or BMP C241: Sediment Pond (Temporary).
• Discharge clean, non-turbid dewatering water, such as well-point groundwater, to systems
tributary to, or directly into surface waters of the State, as specified in Element #8: Characterize
Channels and Outlets, provided the dewatering flow does not cause erosion or flooding of
receiving waters. Do not route clean dewatering water through stormwater sediment BMPs.
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Note that “surface waters of the State” may exist on a construction site as well as off-site; for
example, a creek running through a site.
• Handle highly turbid or otherwise contaminated dewatering water separately from stormwater.
• Dewatering operations must be observed by a site representative at all times to ensure highly
turbid or otherwise contaminated dewatering water is not discharged to surface waters of the
State.
• Other dewatering treatment or disposal options may include:
o Infiltration.
o Transport off-site in a vehicle, such as a vacuum flush truck, for legal disposal in a
manner that does not pollute state waters.
o Ecology-approved on-site chemical treatment or other suitable treatment technologies.
o Sanitary or combined sewer discharge with local sewer district approval, if there is no
other option. For discharges to the sanitary sewer, permits must be obtained from the
City.
o Use of a sedimentation bag that discharges to a ditch or swale for small volumes of
localized dewatering.
• Channels must be stabilized, as specified in Element #8: Stabilize Channels and Outlets.
• Construction equipment operation, clamshell digging, concrete tremie pour, or work inside a
cofferdam can create highly turbid or contaminated dewatering water.
• Discharging sediment-laden (muddy) water into waters of the State likely constitutes violation
of water quality standards for turbidity. The easiest way to avoid discharging muddy water is
through infiltration and preserving vegetation.
• Dewatering water from contaminated sites must be handled separately from stormwater. Direct
contaminated stormwater to a sanitary sewer only where allowed by the City Wastewater Utility
Department, or to other approved treatment.
Suggested BMPs:
o BMP C203: Water Bars
o BMP C236: Vegetative Filtration
Element #11: Maintain BMPs
• Maintain and repair all temporary and permanent construction stormwater BMPs as needed to
ensure continued performance of their intended function in accordance with BMP
specifications.
• Remove all temporary construction stormwater BMPs within 30 days after achieving final site
stabilization or after the temporary BMPs are no longer needed.
• Some temporary construction stormwater BMPs are biodegradable and designed to remain in
place following construction. BMP C122: Nets and Blankets is an example of a BMP with
biodegradable options.
• Provide protection to all BMPs installed for the permanent control of stormwater from sediment
and compaction. All BMPs that are to remain in place following completion of construction shall
be examined and placed in full operating conditions. If sediment enters the BMPs during
construction, it shall be removed and the BMP shall be returned to the conditions specified in
the construction documents.
• Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting
from removal of BMPs or vegetation.
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Suggested BMPs
o BMP C150: Materials On Hand
o BMP C160: Certified Erosion and Sediment Control Lead
Element #12: Manage the Project
• Phase development projects to the maximum degree practicable and take into account
seasonal work limitations.
• Inspect, maintain, and repair all BMPs as needed to ensure continued performance of their
intended function. Projects regulated under the CSWGP must conduct site inspections and
monitoring in accordance with Special Condition S4 of the CSWGP.
• Maintain, update, and implement the Construction SWPPP.
• Project sites that require a Construction SWPPP must have site inspections conducted by a
CESCL. The Construction SWPPP must identify the CESCL or inspector, who shall be present
on site or on call at all times.
Phasing of Construction
Phase development projects where feasible in order to prevent soil erosion and transporting of
sediment from the site during construction. Revegetate exposed areas and maintain that vegetation
as an integral part of the clearing activities for any phase.
Clearing and grading activities for developments shall be permitted only if conducted using an
approved site development plan (e.g., subdivision approval) that establishes permitted areas of
clearing, grading, cutting, and filling. Minimize removing trees and disturbing or compacting native
soils when establishing permitted clearing and grading areas. Show on the site plans and the
development site permitted clearing and grading areas and any other areas required to preserve
critical or sensitive areas, buffers, native growth protection easements, or tree retention areas as may
be required.
Seasonal Work Limitations
Construction activity presents an increased risk to water resources during the typically wet fall through
spring periods in the Pacific Northwest. As such, particular attention must be given to proper selection,
design, and installation of erosion and sediment control BMPs. From October 1 through April 30,
clearing, grading, and other soil disturbing activities may be permitted only if shown to the satisfaction
of the City that the site operator will prevent silt-laden runoff from leaving the site through activities
including but not limited to the following:
• Compliance with Element #5: Stabilize Soils
• Minimization of areas of site disturbance
• Limitation of construction activities that will disturb soil or increase the potential for soil erosion
and transport
• Installation and regular inspection of all proposed construction stormwater BMPs.
• Completion, submission, and approval of a wet-season amendment to the SWPPP, which may
include additional construction BMPs (e.g., stabilized parking, dewatering provisions etc.),
stopping work during the wettest months, and/or a bond for maintenance of the downstream
system.
Based on the information provided and/or local weather conditions, the City may expand or restrict the
seasonal limitation on site disturbance. The City may take enforcement action—such as a notice of
violation, administrative order, penalty, or stop-work order under the following circumstances:
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• If, during the course of any construction activity or soil disturbance during the seasonal
limitation period, sediment leaves the construction site, potentially causing a violation of the
surface water quality standard.
• If clearing and grading limits or construction stormwater BMPs shown in the approved plan are
not maintained.
The following activities are exempt from the seasonal clearing and grading limitations:
• Routine maintenance and necessary repair of construction stormwater BMPs
• Routine maintenance of public BMPs or existing utility structures that do not expose the soil
or result in the removal of the vegetative cover to soil
• Activities where there is 100 percent infiltration of surface water runoff within the site in
approved and installed construction stormwater BMPs.
Coordination with Utilities and Other Contractors
The primary project applicant shall evaluate, with input from utilities and other contractors, the
stormwater management requirements for the entire project, including the utilities, when preparing the
Construction SWPPP.
Inspection
All BMPs must be inspected, maintained, and repaired as needed to ensure continued performance
of their intended function. Site inspections must be conducted by a person knowledgeable in the
principles and practices of erosion and sediment control. The person must have the skills to assess:
1. The site conditions and construction activities that could impact the quality of stormwater, and
2. The effectiveness of erosion and sediment control measures used to control the quality of
stormwater discharges.
For all project sites that require a construction SWPPP, a CESCL must be identified in the construction
SWPPP; this person must be on-site or on-call at all times. Certification must be obtained through an
approved training program that meets the erosion and sediment control training standards established
by Ecology. See BMP C160: Certified Erosion and Sediment Control Lead.
Appropriate BMPs or design changes shall be implemented as soon as possible whenever inspection
and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to
the actual discharge of/or potential to discharge a significant amount of any pollutant.
The CESCL or inspector must examine stormwater visually for the presence of suspended sediment,
turbidity, discoloration, and oil sheen. They must evaluate the effectiveness of BMPs and determine if
it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges.
Based on the results of the inspection, construction site operators must correct the problems identified
by:
• Reviewing the Construction SWPPP for compliance with the 13 elements and making
appropriate revisions to the Construction SWPPP within 7 days of the inspection during the
dry season and within 3 days during the wet season.
• Immediately begin the process of fully implementing and maintaining appropriate source
control and/or treatment BMPs as soon as possible.
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o During the dry season (May 1 through September 30): Address the problems within
10 days of the inspection. If installation of necessary treatment BMPs is not feasible
within 10 days, the construction site operator may request an extension within the initial
10-day response period.
o During the wet season (October 1 through April 30): Address the problems within
24 hours upon receiving notification from the City inspector.
• Documenting BMP implementation and maintenance in the site log book (applies only to sites
that have coverage under the CSWGP).
The CESCL or inspector must inspect all areas disturbed by construction activities, all BMPs, and
all stormwater discharge points at the following frequency:
• During the dry season (May 1 through September 30): At least once every calendar week
and within 24 hours of any discharge from the site. If there are rain showers, the frequency
should be at least twice per week.
o For purposes of this condition, individual discharge events that last more than 1 day
do not require daily inspections. For example, if a stormwater pond discharges
continuously over the course of a week, only one inspection is required that week.
o The CESCL or inspector may reduce the inspection frequency for temporary stabilized,
inactive sites to once every calendar month during the dry season only.
• During the wet season (October 1 through April 30): At least once every other day and
within 24 hours of any discharge from the site.
Note that additional requirements may apply per the project specific SWPPP and/or permits, as
applicable.
Maintaining an Updated Construction SWPPP
• Retain the Construction SWPPP on site or within reasonable access to the site.
• Modify the Construction SWPPP whenever there is a change in the 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 Construction SWPPP must be modified if, during inspections or investigations conducted
by the owner/operator, the City, or state regulatory authority, it is determined that the
Construction SWPPP is ineffective in eliminating or significantly minimizing pollutants in
stormwater discharges from the site. Modify the Construction SWPPP as necessary to include
additional or modified BMPs designed to correct problems identified. Complete revisions to
the Construction SWPPP within 7 days following the inspection.
Suggested BMPs
o BMP C150: Materials On Hand
o BMP C160: Certified Erosion and Sediment Control Lead
o BMP C162: Scheduling
Element #13: Protect Low Impact Development BMPs
The primary purpose of On-Site Stormwater Management is to reduce the disruption of the natural site
hydrology through infiltration. BMPs used to meet CR5: On-Site Stormwater Management (often called
LID BMPs) are permanent BMPs.
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• Protect all LID BMPs (including, but not limited to BMP T7.30: Bioretention, BMP T5.14: Rain
Gardens, and BMP T5.15: Permeable Pavements) from sedimentation through installation and
maintenance of erosion and sediment control BMPs on portions of the site that drain into the
LID BMPs. Restore the BMPs to their fully functioning condition if they accumulate sediment
during construction. Restoring the BMP must include removal of sediment and any sediment-
laden Bioretention/Rain Garden soils, and replacing the removed soils with soils meeting the
design specification.
• Maintain the infiltration capabilities of LID BMPs by protecting against compaction by
construction equipment and foot traffic. Protect completed lawn and landscaped areas from
compaction due to construction equipment.
Control erosion and avoid introducing sediment from surrounding land uses onto BMP T5.15:
Permeable Pavements. Do not allow muddy construction equipment on the base material or
permeable pavements. Do not allow sediment-laden runoff on the base material or permeable
pavements. Do not stockpile material on the base material or permeable pavements.
Permeable pavement fouled with sediments or no longer passing an initial infiltration test must
be cleaned using procedures in accordance with the SMMWW.
Keep all heavy equipment off existing soils under LID BMPs that have been excavated to final
grade to retain the infiltration rate of the soils.
• See Section 5.3 and Chapter 5: Precision Site Preparation, Construction & Inspection of LID
Facilities in the Low Impact Development Technical Guidance Manual for Puget Sound
(Hinman and Wulkan 2012) for more details on protecting LID integrated management
practices.
Note that the Low Impact Development Technical Guidance Manual for Puget Sound is for
additional informational purposes only. You must follow the guidance within this manual if there
are any discrepancies between this manual and the Low Impact Development Technical
Guidance Manual for Puget Sound.
Suggested BMPs
o BMP C102: Buffer Zone
o BMP C103: High Visibility Fence
o BMP C200: Interceptor Dike and Swale
o BMP C201: Grass-Lined Channels
o BMP C207: Check Dams
o BMP C208: Triangular Silt Dike (TSD)
o BMP C231: Brush Barrier
o BMP C233: Silt Fence
o BMP C234: Vegetated Strip