The Spokane City Council awarded in December a $7.7 million contract to Garco Construction Inc., of Spokane, to build a 1.5 million gallon combined sewer overflow (CSO) tank, says city spokeswoman Marlene Feist. 

Construction of the tank is slated to begin in March, Feist says, and should last about 18 months. 

The tank, Feist says, will be located mostly underneath the parking lot at Underhill Park, near the intersection of Hartson Avenue and Fiske Street, in south Spokane. Once in place, it also will surpass the 1 million gallon CSO tank currently being constructed at 21st Avenue and Ray Street as the largest tank the city has built to date. 

The primary function of the tanks, Feist says, is to reduce overflows from combined sewers, which contain both wastewater and stormwater, to the Spokane River. During large storms, when pipes become too full, they will overflow to the tank. 

“We will hold combined stormwater and wastewater in the tank until the storm surge subsides, and then meter it to the city’s wastewater treatment plant,” Feist says. 

Clearwater Construction & Management LLC, of Spokane, is building the $4.7 million tank at 21st and Ray, Feist says. That tank is slated to be completed in November 2014. It, too, is intended keep storm and sewer overflow from entering the Spokane River during storm surges. The tank also is expected to help reduce localized flooding in Lincoln Heights. 

“We’ve had issues with basement flooding in the area, and this will help,” Feist says. 

The two tank projects are part of a larger integrated clean water plan that the city has enacted to better manage wastewater and stormwater runoff. The goal is to reduce pollutants entering waterways, as required by the Federal Clean Water Act and other regulations. 

“Where we’re at right now is we are finalizing the plan,” Feist says. “We expect to submit it to the Department of Ecology for review in March.”

The city also is considering a project to manage stormwater runoff from the Cochran Basin on Spokane’s North Side. Feist says the city is doing testing on three areas in northwest Spokane as possible sites for the project. She says the project hasn’t been fully designed yet, but could include a CSO tank and some sort of bio-filtration facility. 

Spokane must substantially reduce its combined sewer and stormwater runoff by year-end 2017, as mandated by the U.S. Environmental Protection Agency and the Washington state Department of Ecology. Expenditures of about $300 million are expected for projects during the next five years to seek to comply with those mandates. Projects will include combined sewers, stormwater drainage, and an additional treatment level at Riverside Park Water Reclamation Facility.