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. The City created a 2021 Stormwater Management Program (PDF) (SWMPP) to comply with the requirements of the Permit.  If you are interested in providing feedback on the 2021 SWMPP, please feel free to participate in the public comment period through April 30, 2021 by sending comments and questions to   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