Rain and snowmelt that collects on impervious surfaces like roofs, roads and parking areas, becomes stormwater runoff. Runoff that reaches our rivers or infiltrates into our groundwater often carries harmful pollutants. Heavy metals, lawn and garden chemicals, animal waste, sediment, petroleum products, and trash are common pollutants found in stormwater. In fact, urban runoff is responsible for more than 60% of the water pollution in Washington State!

Even though Pasco only receives an average of 8 inches of rainfall annually, the pollutant load here can actually be even greater than in cities that receive much more rainfall. That’s because the pollutants have a longer time to collect and concentrate on impervious surfaces between our infrequent storm events.

To ensure the health and safety of our citizens and our rivers, the City of Pasco operates a Municipal Separate Storm Sewer System (MS4) under a Phase II Eastern Washington Stormwater Permit (Permit (PDF)) issued by the state of Washington.  In accordance with the Permit, the City developed the 2021 Stormwater Management Program Plan (SWMPP) to inform the public of actions and activities that are planned during the upcoming annual reporting cycle of the MS4 Permit.

The SWMPP is updated annually and submitted to Ecology with the MS4 Annual Report in accordance with Permit Requirements S9.  In general, the SWMPP is designed to reduce the discharge of pollutants from the City's regulated MS4 to the Maximum Extent Practicable (MEP), satisfy the state requirement under RCW 90.48 to apply All Known, Available, and Reasonable methods of prevention, control, and Treatment (AKART) prior to discharge, and to protect water quality.

On March 31, 2021, a draft 2021 SWMPP was made available on the City's website and open to public comment through April 30, 2021.  No comments were received from the public.  Click here to view the final 2021 Stormwater Management Program (PDF) (SWMPP).

The City’s annual report (PDF) documents the steps we’ve taken to comply with the conditions of the Permit.

The good news is that we can all do something to help to keep our stormwater clean!

If you are having problems with road drainage, blocked storm drains, property or basement flooding, or to report illicit discharges to the City’s stormwater system please call the STORMWATER HOTLINE at 509-543-5777


City of Pasco Standards & Specifications

City of Pasco Comprehensive Stormwater Plan (2016)

Stormwater Management Manual for Eastern Washignton

Eastern Washington Low Impact Development (LID) Guidance Manual