Spokane’s secondary digester for sewage waste will soon have a No. 2.
The City Council approved Monday $11.3 million for the construction of a new sewage digester to serve as back-up for the two steel, egg-shaped digesters that have turned solid waste into fertilizer since 2008.
“We need the digester a lot for redundancy,” said utilities spokeswoman Marlene Feist. “But it will help with capacity.”
The low bid for the project came from IMCO General Contractors, of Ferndale, Washington. Local builders Garco Construction also bid on the work, but their estimate was almost $2 million higher than IMCO’s.
At Monday’s meeting, City Council President Ben Stuckart said he had investigated concerns over the bidding process, but found no wrongdoing.
“IMCO is a great company,” he said.
The Riverside Park Water Reclamation Facility receives an average of 34 million gallons of wastewater every day, which the two existing digesters easily work through. Unlike the liquid part of the waste, which is skimmed off, treated and put back in the river, the digesters use a microbial process to convert the raw solids into 6,500 tons of bio-solids annually. Local farmers use the final product as fertilizer on crops not intended for human consumption.
The new digester will be silo-shaped and made of concrete. It will act as back-up for the secondary digester during maintenance, and it meets the state Ecology department’s redundancy requirements.
Feist said the city doesn’t anticipate having to build another digester anytime soon.
“These are 50- to 100-year assets,” she said.