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Stormwater monitoring

Stormwater runoff can flow directly into fresh or marine waters, or it may go into a storm drain system and continue through storm pipes until discharging into the environment. Stormwater management activities include keeping rainwater clean and using best management practices to infiltrate and clean polluted stormwater prior to its discharge.

Monitoring the results of these activities provides critical information to know how well stormwater management actions are working.

Cooperative monitoring is underway for jurisdictions that are subject to municipal stormwater permits.

  • Stormwater Action Monitoring (SAM) is a collaborative program focused on Western Washington pollution source control and effectiveness studies. It includes studies on Puget Sound-focused receiving water.
  • Eastern Washington's stormwater group is a coordinated program focusing on effectiveness studies of best management practices.
  • Southwest Washington’s Lower Columbia status and trends efforts study small streams in the Lower Columbia basin.

We provide tools to support monitoring for the state's construction, industrial, and sand and gravel permits, including:

  • Stormwater and best management practices monitoring studies
  • Discharge monitoring reports (DMRs)
  • Monitoring guidance, operating procedures, and resources for permits

Stormwater permits require discharge and outfall monitoring

Monitoring is required for businesses and jurisdictions to stay in compliance with construction, industrial, and municipal stormwater permits. Monitoring for construction and industrial permittees is done at the point of discharge or from the site.

For municipal stormwater permittees, there are so many hundreds of outfalls that monitoring all of them is not feasible.

Cooperative monitoring for municipal stormwater permittees
Municipal stormwater outfall monitoring results

Strategic stormwater initiatives

We are partnering with Puget Sound Partnership on the National Estuary Program strategic stormwater initiatives.

Stormwater treatment effectiveness monitoring

Best management practices (BMPs) are monitored for their effectiveness under two distinct programs that we administer:

Each program has a different focus, however, results from one program inform the other. Results also inform our stormwater management manual.

We fund stormwater treatment projects through grants. An active area of Low Impact Development (LID) monitoring is on bioretention soil media.

Submitting discharge monitoring reports

Reporting on your stormwater discharges is an important step to understand compliance with a permit and impacts to fresh, marine, or groundwater. Discharge Monitoring Reports (DMRs) characterize important apects of your system like stormwater volumes, pollutant concentrations, and suspended stormwater sediment concentrations.

Why do we track stormwater data?

Monitoring data collected by permittees provides the needed information on how well a permit is working to manage stormwater. Our industrial, construction, and sand and gravel stormwater permits require discharge monitoring to know if the water is clean enough to protect the water quality of the receiving water body.

DMRs are a federal requirement

The federal Clean Water Act permits we administer require the permittees to submit discharge monitoring reports (DMRs) to report pollution discharge data.

Permittees are required to submit DMRs each reporting period even if no sampling or discharge occurred. Stormwater permit compliance data collected by permittees are stored in the Permit and Reporting Information System (PARIS) database. In PARIS you can find current and historical permit data.

How to sample stormwater discharges: Compliance-related monitoring resources for permittees

Compliance monitoring can be required by the industrial, construction, municipal, sand and gravel, or boatyard permits.


Standard operating procedures (SOPs)

We have three SOPs specific for outfall monitoring used under the municipal permits that follow our quality assurance guidelines.

Industrial Construction Sand & Gravel