Stormwater & water quality

Follow these procedures to comply with stormwater and water quality regulations.

Identify existing contamination

Use the Hazardous Materials webpage and coordinate with the HazMat program.

Identify receiving waters

Use the Wetlands & other waters page during scoping to identify waters in your project area based on how those waters are used. Look up the applicable water quality standards and mixing zones by designated use.

Determine if your project will discharge to impaired water bodies

Use Ecology’s Water Quality Atlas or our GIS Environmental Workbench to:

  • Find out if any of the receiving waters where the project will have an outfall (temporary or permanent) are impaired. Impaired water bodies include those on the 303(d) list or covered by a Total Maximum Daily Load (TMDL).
  • Identify all potential discharge points (i.e., temporary outfalls for construction or permanent outfalls) to surface water bodies. Coordinate with the project hydraulic engineer(s) as needed.

Inventory stormwater discharge points

When preparing the hydraulics report for your project, use the following tools to identify where the project will discharge stormwater to receiving waters:

Determine permit needs

Section 401 Water Quality Certification (WQC)

Work that needs a Federal permit or approval (Section 404 discharge permit, Section 10 structure permit, or Section 9 Bridge Permit) and discharges or has the potential to discharge pollutants into WOTUS must receive a Clean Water Act Section 401 Water Quality Certification (WQC) from the appropriate Section 401 certifying agency or tribe.

Determine certifying agency

For work not on tribal lands, the Washington State Department of Ecology (Ecology) has authority.

For work on tribal lands, see contacts for a list of tribes that have WQC authority. If your project is on tribal lands for a tribe not listed, the Environmental Protection Agency has authority.

Determine if you need an Individual WQC

Use the Wetlands, streams, & tidal waters webpage to determine if your work requires a Section 404,10, or Bridge permit.

If you qualify for a Nationwide Permit (NWP), use the NWP guidance and resources on the Wetlands, streams, & tidal waters webpage to determine if you may need an Individual WQC from the certifying agency or if you fit the conditions to be covered under the programmatic WQC.

For Individual 404, 10, and Bridge permits, you will always need an Individual WQC, or WQC Order.

Coordinate with liaisons

Coordinate with the Corps and Ecology Liaisons if you need help scoping the permitting needs. 

Section 402 general permits

Section 402 permits regulate sources of pollutants that could make their way to surface waters like streams, lakes, and the Puget Sound. They contain limits on what WSDOT can discharge, monitoring and reporting requirements, and other requirements to protect water quality. Determine if your project can be covered under a general permit listed below.

Construction Stormwater General Permit

Apply for coverage under the CSWGP during final design if your project has the potential to discharge stormwater to surface waters and will either disturb one or more acres of soil or is part of a larger plan that will end up disturbing one or more acres of soil.

If your project is smaller than one acre with known contamination, you may be required to apply for coverage under the CSWGP and be issued an Administrative Order (AO), particularly if your project will discharge to a jurisdictional storm sewer system. Coordinate early with Ecology to determine coverage needs and prevent permitting delays.

WSDOT Municipal Stormwater General Permit

Projects located within areas covered by a Phase I or Phase II Municipal Stormwater General Permit must comply with specific conditions in this permit. This permit authorizes the discharge of stormwater from stormwater systems owned or operated by WSDOT along highways, at ferry terminals, rest areas, park & ride lots, maintenance facilities, vactor decant and street sweepings facilities, and winter chemical storage facilities.

Use the following links to access details on this permit and how to comply with its conditions:

Industrial Stormwater General Permit

A permit may be required for certain industrial activities. It authorizes stormwater and conditionally approved non-stormwater discharges associated with industrial activities. WSDOT has coverage under this permit at the Washington State Ferries Eagle Harbor Repair Facility.

See Ecology’s Industrial Stormwater General Permit for details on this permit and how to comply with its conditions.

Bridge & Ferry Terminal Washing General Permit

A permit is required when you discharge water associated with work on bridges, ferry terminal transfer spans, or associated overwater structures.

See Ecology’s Bridge and Ferry Terminal Washing General Permit for details on this permit and how to comply with its conditions.

Aquatic Noxious Weed Control General Permit

A permit is required for herbicide applications made near surface water to manage noxious and quarantine weeds. WSDOT has permit coverage statewide for all aquatic herbicide applications on our property.

Use the following links to access details on this permit and how to comply with its conditions:

Aquatic Plant & Algae Management General Permit

A permit is required for herbicide applications made in or near surface water to manage nuisance vegetation not on the state noxious weed list. It authorizes direct and indirect discharges of specific herbicides and other chemicals into surface waters. WSDOT has permit coverage statewide for all aquatic herbicide applications on our property.

Use the following links to access details on this permit and how to comply with its conditions:

Aquatic Mosquito Control General Permit

A permit is required for pesticide applications in or near surface water to control mosquitos. WSDOT has permit coverage statewide for all pesticide applications for mosquito control on our property.

Use the following links to access details on this permit and how to comply with its conditions:

Section 402 Administrative Order

If existing site contamination will be disturbed and potentially discharged, Ecology may issue an AO that adds additional project-specific requirements. It is highly recommended that early coordination with Ecology occurs to avoid or prepare for an AO.

Review the questions below to consider site contamination and determine the likelihood of an AO:

  1. Are you aware of contaminated soils present on the site? 
  2. Are you aware of groundwater contamination located within the site boundary (i.e., parcel boundary or larger project area including off-site support areas)?
  3. If you answered yes to questions 1 or 2, will any contaminated soils be disturbed or will any contaminated groundwater be discharged due to the proposed construction activity?

Identify existing best management practices (BMPs)

Identify existing BMPs using as-builts, WSDOT’s GIS Workbench, hydraulics reports, the Stormwater BMP Specifications (SWABS) database, field verification, and guidance in the HRM.

Look for opportunities for stormwater retrofits

Many existing highways either do not have any stormwater flow control or treatment facilities, or do not have enough to manage the runoff from all impervious surfaces.

Use the information below to improve stormwater management in these areas and comply with permits:

  • Determine retrofit obligations and identify stormwater retrofit opportunities for your project using the guidelines in chapter 2-1 Stormwater Planning and Design Integration and chapter 3-4 Stormwater Retrofit Guidelines of the Highway Runoff Manual.

To find out if an area is in a high, medium, or low priority area for stormwater retrofit, contact Sheena Pietzold, Sheena.Pietzold@wsdot.wa.gov.

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