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Regulatory and Permitting Information Desktop Toolkit

Washington Construction Storm Water Permit (6-WA-b)

In Washington, a developer may need to obtain a Construction Storm Water General Permit (CSWGP) from the Washington State Department of Ecology (WSDE) if construction activities will discharge storm water to surface waters in Washington and will disturb one or more acres of land or are part of a common plan of development or sale that will disturb one or more acres of land. The WSDE regulates discharges from construction storm water through RCW 90.48 and Washington Administrative Code 173-226. The CSWGP is the primary regulatory measure in Washington to help developers prevent muddy water from leaving construction sites. The CSWGP covers all areas of Washington State, except for federal and Tribal lands as specified in the CSWGP.

In addition, the WSDE may require a construction storm water permit for any size construction activity discharging storm water into surface waters in Washington if the WSDE:

  • Determines the construction activity to be a significant contributor of pollutants to waters of Washington; and
  • Reasonably expects the construction activity to cause a violation of any water quality standards in Washington.

If the construction storm water discharge causes less than one acre of surface disturbance and the WSDE does not otherwise require the developer to obtain a construction storm water permit, the developer does not need a permit for construction storm water activities.

See Washington Construction Storm Water General Permit.

Construction activities that discharge all storm water and non-storm water to ground water, sanitary sewer, or combined sewer and have no point source discharge to either surface water or a storm sewer system that drains surface waters of Washington are not required to seek coverage under the NPDES construction storm water program. Washington Construction Storm Water General Permit.

Construction Storm Water Permit Process

6-WA-b.1 to 6-WA-b.2 – Will the Activity Disturb Less Than 5 Acres and Have an R-Factor of Less Than 5 During the Construction Period

If the construction activity will disturb less than five acres and have an Erosivity “R” Factor of less than five during the construction period, the construction site may qualify for an erosivity waiver from the CSWGP. In calculating the R factor for the construction period, the developer must use EPA’s Calculator. In addition, the entire period of the construction activity must fall within the following timeframes:

  • For sites west of the Cascades Crest: June 15-September 15; and
  • For sites east of the Cascades Crest, excluding the Central Basin: June 15-October 15.

Note: the “Central Basin” is defined as the portions of Eastern Washington with mean annual precipitation of less than 12 inches. If the construction activity qualifies for the erosivity waiver, the developer must submit a complete Erosivity Waiver Certification Form at least one week before disturbing the land. The certification form must include statements that the developer will:

  • Comply with applicable local storm water requirements; and
  • Implement appropriation erosion and sediment control best management practices (BMPs) to prevent violations of Washington water quality standards.

Of note, the waiver is not available for facilities declared significant contributors of pollutants as defined in the CSWGP nor does the waiver apply to construction activities which include non-storm water discharges. In addition, if the construction activity extends beyond the certified waiver period and the R factor for the entire construction project is above 5 or extends outside of the applicable regional timeframe, the developer must complete and submit a CSWGP NOI to the WSDE before the end of the certified waiver period.

See Washington Construction Storm Water General Permit.

6-WA-b.3 to 6-WA-b.4 – Does the WSDE Determine that the Construction Storm Water General Permit Provides Adequate Protection to Water Quality

The WSDE may require any discharger to apply for and obtain coverage under an individual permit or another more specific general permit. The WSDE will require such alternative coverage if the WSDE determines that the CSWGP does not provide adequate assurance that the construction activity will protect water quality or there is a reasonable potential for the project to cause or contribute to a violation of water quality standards. The following discharges to the waters of Washington, including ground water are prohibited:

  • Concrete wastewater;
  • Wastewater from washout and clean-up of stucco, paint, form release oils, curing compounds and other construction materials;
  • Process wastewater as defined by 40 CFR 122.1;
  • Slurry materials and waste from shaft drilling;
  • Fuels, oils, or other pollutants used in vehicle and equipment washing;
  • Wheel wash wastewater, unless discharged according to CSWGP Special Condition S9.D.9.d; and
  • Discharges from dewatering activities, including discharges from dewatering of trenches and excavations, unless managed according to CSWGP Special Condition S9.D.10.

In addition, the following storm water discharges are not covered by the CSWGP:

  • Post-construction storm water discharges that originate from the site after completion of the construction activities and the site has undergone final stabilization;
  • Non-point source silvicultural activities such as nursery operations, site preparation, reforestation, and subsequent cultural treatment, thinning, prescribed burning, pest and fire control, harvesting operations, surface drainage, or road construction and maintenance, from which there is natural runoff as excluded in 40 CFR 122;
  • Storm water from any federal project or project on federal land or land within an Indian Reservation except for the Puyallup Reservation (within the Puyallup Reservation, any project that discharges to surface water on land held in trust by the federal government may be covered under the CSWGP);
  • Storm water from any site covered under an existing NPDES individual permit in which storm water management and/or treatment requirements are included for all storm water discharges associated with construction activity; and
  • Storm water from a site where an applicable Total Maximum Daily Load (TMDL) requirement specifically precludes or prohibits discharges from construction activity.

For an example of a CSWGP, including a listing of the above prohibited discharges and discharges not covered under the CSWGP, see Washington Construction Storm Water General Permit.

Where the discharge is either prohibited or not covered, developers must initiate the State NPDES Permitting Process:

6-WA-b.5 – Storm Water Pollution Prevention Plan (SWPPP)

The developer must prepare and properly implement an adequate Storm Water Pollution Prevention Plan (SWPPP) for construction activity in accordance with the requirements of the CSWGP, beginning with initial soil disturbance and until final stabilization. The SWPPP must meet the following objectives:

  • To implement BMPs to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent storm water contamination and water pollution from construction activity.
  • To prevent violations of surface water quality, ground water quality, or sediment management standards.
  • To control peak volumetric flow rates and velocities of storm water discharges.

The SWPPP must include a narrative and drawings. All developer must clearly reference all BMPs in the narrative and marked on the drawings. The SWPPP narrative must include documentation to explain and justify the pollution prevention decisions made for the construction activity. Documentation must include:

  • Information about existing site conditions (topography, drainage, soils, vegetation, etc.);
  • Potential erosion problem areas;
  • The 12 elements of a SWPPP in Special Condition S9.D1-12 of the CSWGP, including BMPs used to address each element;
  • Construction phasing/sequence and general BMP implementation schedule;
  • Actions to be taken if BMP performance goals are not achieved;
  • Engineering calculations for ponds and any other designed structures.

For more information on SWPPP requirements, including storm water BMPs and narrative contents and requirements consult the Washington Construction Storm Water General Permit.

6-WA-b.6 – Notice of Intent (NOI) for Construction Storm Water General Permit

Developers of new or previously unpermitted construction activities must submit a complete and accurate Notice of Intent (NOI) for Construction Storm Water General Permit Application to the WSDE at least 60 days before discharging storm water from construction activities. In addition, the developer must submit the NOI on or before the date of the first public notice. The developer may complete and submit the NOI online at the WSDE’s NOI webpage. The NOI application form includes:

  • Information about the developer/permittee, property owner and on-site contact person, including name, phone number, and mailing address;
  • Site information;
  • Existing site conditions;
  • SWPPP;
  • BMPs;
  • Discharge/receiving water information;
  • Location of discharge into surface waterbody;
  • State Environmental Policy Act Requirements;
  • Public notice requirements; and
  • Certification of the developer/permittee.

Developers who propose to discharge to a storm or sewer system operated by Seattle, King County, Snohomish County, Tacoma, Pierce County, or Clark County must also submit a copy of the NOI to the appropriate jurisdiction.

See Washington Construction Storm Water General Permit.

6-WA-b.7 to 6-WA-b.8 – Public Notice of NOI

The developer seeking coverage under the CSWGP must publish notice at least one time each week for two consecutive weeks (at least 7 days apart) in a newspaper with general circulation in the county where the construction is to take place. The notice must contain:

  • A statement that “The applicant is seeking coverage under the Washington State Department of Ecology’s Construction Storm Water NPEDES and State Waste Discharge General Permit”;
  • The name, address, and location of the construction site;
  • The name and address of the developer;
  • The type of construction activity that will result in a discharge and the number of acres the discharge will disturb;
  • The name of the receiving water(s) or if discharge is through a storm sewer system, the name of the operator of the system; and
  • The statement “Any person desiring to present their views to the department of ecology regarding this application may do so in writing within thirty days of the last date of publication of this notice. Comments shall be submitted to the department of ecology. Any person interested in the department’s actions on this application may notify the department of their interest within thirty days of the last date of publication of this notice.”

As addressed directly above, the public has thirty days from the last date of publication of the notice to submit comments to the WSDE.

See Washington Construction Storm Water General Permit and WAC 173-226-130.

6-WA-b.9 to 6-WA-b.10 – Construction Storm Water General Permit

Unless the WSDE responds to the complete application in writing, based on public comments, or any other relevant factors, coverage under the CSWGP automatically begins on the 31st day following receipt by the WSDE of a completed NOI. If the WSDE responds in writing, they may specify a later date for the CSWGP to commence. Once the CSWGP goes into effect, the developer may being the construction storm water discharge activities.

See Washington Construction Storm Water General Permit.

6-WA-b.11 – Notice of Termination

The construction site is eligible for termination of coverage when it has met any of the following conditions:

  • The site has undergone final stabilization, the developer has removed all temporary BMPs (except biodegradable BMPs clearly manufactured with the intention for the material to be left in place and not interfere with maintenance or land use), and all storm water discharges associated with construction activities have been eliminated; or
  • All portions of the site that have not undergone final stabilization (per CSWGP Special Condition S10.A.1) have been sold and/or transferred and the developer no longer has operation control of the construction activity.

When the site is eligible for termination, the developer must submit a complete and accurate Notice of Termination (NOT) form, signed in accordance with General Condition G2 of the CSWGP to the WSDE. The termination is effective on the date the WSDE receives the NOT form, unless the WSDE notifies the developer within 30 days that the termination request is denied.

See Washington Construction Storm Water General Permit.

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