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What is dewatering?

Dewatering is the process of pumping groundwater or stormwater away from an active construction site. This water should be pretreated and sent to a surface water body, either directly or through a storm drain.

Construction wastewater is wastewater generated during construction activities. It includes process wastewater and co-mingled construction dewatering water from active construction areas. Treated stormwater and/or groundwater that is co-mingled with construction process water (wheel wash water, concrete wastewater, pre-treated slurry wastewater, well development wastewater), may be sent into the sanitary sewer, with permission from the appropriate authorities.

Construction Dewatering Authorization Frequently Asked Questions

Water pooling at a construction site. Construction dewatering authorization allows projects to pump this water away from the jobsite.
Dewatering is the process of pumping groundwater and stormwater away from a jobsite.

Who needs authorization from King County?

Authorization required in King County's wastewater service area

Most construction projects that generate wastewater or stormwater need written approval to discharge into sanitary sewer. This includes wastewater discharged into:

  • Seattle's combined sewers (pipes that carry stormwater and sewage)
  • Stormwater sewers
  • Surface water body

Projects done on single family residences do not need written approval.

You must get permission from both the King County Industrial Waste Program and your local sewer agency to send wastewater to the sewer.

The same is true when direct or indirect discharge to stormwater sewers or a surface water body is unavailable. You must get permission from King County and your local sewer agency to send treated water to the sewer.

  • For construction projects located in the City of Seattle service area, please contact Seattle Department of Construction and Inspections (SDCI) for approval to discharge to the sanitary sewer (SDCI must provide: discharge location, flow rate (in gpm), other conditions for discharge to their system, and contact information for who you worked with at the agency) at or 206-684-5362.

KCIW will not process your application if it is missing local sewer agency discharge approval information.

Authorization not required in King County's waste service area

Single-family residential construction projects

King County does not require an application for single-family residential construction projects, however, you must check with the local city or sewer agency before starting. Check with the local city or sewer agency before starting. For City of Seattle, contact SDCI Side Sewer & Drainage Counter at or 206-684-5362.

Projects discharging to dedicated storm drains or surface water bodies

Projects discharging to separated storm sewers or surface water bodies do not need approval from the King County Industrial Waste Program. However, these projects may need authorization for surface water discharge from your local sewer agency or from the Washington State Department of Ecology.

 Site characteristics  Agency to contact
Contaminated site, any size Washington State Department of Ecology 206-594-0000
Clean site, one acre or more  Washington State Department of Ecology 206-594-0000
Clean site, less than one acre  Local jurisdiction's stormwater utility

Steps to get formal authorization

  • Determine which form is appropriate for your project

    Projects that meet all criteria for issuance of a General Letter of Authorization (GLA) as listed below and on page 2 of the general authorization application should complete and submit the general authorization application. All other projects must use the individual authorization application.

  • Contact the local sewer agency where your project is located

    For construction projects in the City of Seattle: Contact the Side Sewer & Drainage Counter at the Seattle Department of Construction & Inspection (SDCI) at Visit SDCI for more information.

    Verify with the agency that your project can discharge to their sewers. The agency must provide to the applicant and the applicant must include in the KCIW application the following:

    • Approved location for the discharge (maintenance hole number or the address for the side sewer connection, or other location identifier)
    • Maximum allowable flow rate in gallons per minute (gpm)
    • Any other conditions or requirements for discharge to the sewer system
    • Name and contact information for person at agency providing the above information.
  • Download and complete the appropriate King County construction dewatering application from the KCIW Construction dewatering webpage

    We prefer that you fill out your application on your computer, but KCIW will accept scanned handwritten applications.

    • Include all the required exhibits listed on page 12 of the individual application
    • Refer to the application checklist on page 2 to verify that you have completed and included each required application component.
    • Print and sign the application. Scan the signed documents and email it to the King County Industrial Waste program at

Which King County form to use

The King County Industrial Waste program has two types of authorizations for discharging construction water to sanitary sewers.

General authorization application

General authorization is easier and has less documentation (no exhibits) than individual authorization. Projects must meet the following criteria to use general authorization:

  • The jobsite is clean and uncontaminated
  • The jobsite is less than 1 acre
  • The total discharge to sanitary sewers is less than 25,000 gallons per day (gpd)
  • The jobsite has a sedimentation tank

Application form

General Authorization Application for Construction Dewatering

Individual authorization application

Projects that do not meet all four criteria for general authorization must use the individual application.


Individual authorizations permitting the discharge of construction wastewater into the sewer system typically require daily self-monitoring. Sampling and reporting requirements vary depending on the site, size, and risk potential of the project.

Find more information and download the self-reporting forms

Application form

Individual Authorization Application for Construction Dewatering

How long does the application process take?

Make sure to allow enough time for your application to process before starting your project. 

General authorization

The general authorization process can be completed in as few as 3 to 10 business days.

Individual authorization

The individual authorization issuance process typically takes longer than the general authorization. The process can take 1 to 3 months to complete depending on the complexity of your project. 

Is there an authorization fee?

  • General authorization has a set fee.
  • Fees for individual authorization and permits vary based on the complexity of the project.

Authorization fees are non-refundable and must be paid even if your plans change and you are no longer discharging to the sewer system.

Visit the fees and surcharges page for more information