Stormwater Logo

Stormwater is defined as the runoff from hard surfaces following storms and snowmelt. Stormwater is a concern because it can transport pollutants to the aquifer or surface waters.

The City of Spokane's stormwater drainage system is a large, complex network of conveyances that are designed to take rainfall and direct it away from roads, buildings, and other public and private property. It consists of several different components, including:

  • More than 300 miles of separate storm sewers that discharge stormwater to infiltration facilities, the Spokane River and Latah Creek at over 100 locations, including many bridges. About 1 billion gallons of untreated stormwater enters the River annually.
  • More than 400 miles of combined stormwater and wastewater sewers that carry stormwater to the City's wastewater treatment plant when it rains. During moderate to heavy rainfall and snowmelt events, a combination of stormwater and untreated sewage can overflow to the Spokane River to prevent overloading the plant.
  • Thousands of swale bioinfiltration treatment facilities that discharge stormwater into the ground after treating the water by trapping sediments, oil, grease, and other pollutants.

Discover more about the dedicated work happening behind-the-scenes to manage stormwater and keep our water safe and clean. The Wastewater Management Department works in tandem with Mother Nature to protect our beautiful Spokane River from pollutants, in addition to being responsible stewards of our region's sole-source aquifer.

As a City, we are putting increasing effort on managing stormwater to improve the health of the Spokane River. The City has developed an Integrated Clean Water Plan that prioritizes projects based on their positive environmental impact to the river. The plan is designed to be both environmentally and financially responsible.

In particular, the plan will reduce the amount of stormwater and wastewater entering the River without treatment. Projects to reduce untreated discharges to the river from both separated storm sewers and combined sanitary and stormwater sewers are a big part of the effort. The work will include new green technologies for managing stormwater on site as well as more traditional "gray" storage tanks.

Additionally, the City is working to manage more stormwater on site. As we improve streets, we are committed to removing stormwater from existing combined sewers and separated storm sewers to reduce and managing it through on-site infiltration and evaporation techniques. We are combining planning work for streets and utility capital needs to gain greater value for our citizens.


Stormwater Managemnet Program Plan

Comments on the SWMP Plan may be submitted by email at from now until May 5th, 2022