Northside Decant Facility

About the Project

The Northside Decant Facility project involved construction of a regional vactor-truck decant facility for north Spokane. The facility will protect water quality in area rivers, streams, and Spokane’s sole-source aquifer, and will serve Spokane County, the City of Spokane, and the Washington State Department of Transportation.

The decant facility is at the site of the Spokane County Old Corral Facility at 12807 N Mayfair, Parcel 36056.9018. There is adequate space within the boundaries of the 51.93-acre site to support the construction, access, and ongoing maintenance of the Decant Facility. Prior to construction, all vactor loads from the region were either untreated or delivered to Waste Management’s Graham Road Facility, which is approximately 20 miles away.

The facility consists of a covered concrete pad, an oil/water separator, bio-infiltration swale, site utilities such as water and power, allows for future sewer connection, and has an asphalt paved road to the facility. Only vactor waste from storm sewers, and waste from street sweepers will be allowed at this facility.

Decant Facility

The City of Spokane has also constructed a decant facility. The Northside Decant Facility will be similar, with the exception of the treatment train. The City of Spokane utilizes an evaporation pond for treatment/disposal of water. The County facility will include a bio-infiltration swale with drywells for treatment and disposal.

The Northside Decant Facility assists Spokane County in meeting requirements of the Eastern WA Phase II Municipal Stormwater Permit and the Spokane River and Lake Spokane Dissolved Oxygen total maximum daily load (TMDL) by providing water quality treatment for polluted sediments and water from catch basins and drywells. The facility will help improve both surface water quality within the Spokane River, Little Spokane River, Deadman Creek, and groundwater within the Spokane Valley-Rathdrum Prairie aquifer.

This project was designed in accordance with the Spokane Regional Stormwater Manual which is an Ecology-approved, equivalent manual to the Stormwater Management Manual for Eastern Washington.

Project Funding

Funding for this project, estimated to cost $1,500,000, comes from local stormwater fees (25%) and grant funds from Washington State Department of Ecology (75%).