Columbia City Council considers $7 million in wastewater plant upgrades

The Columbia City Council approved $7 million worth of improvements to part of the city’s wastewater treatment plant.

The council unanimously passed the improvements to the plant’s digester complex at the plant off Gillespie Bridge Road. The improvements include new covers for the four individual digesters, a new mixing system and roof and brick work on the building itself.

The plant’s digester takes solids from the waste that makes it from the city’s sewer system to the plant and turns it into products such as fertilizer. City staff said the complex produces hundreds of tons of biosolids every year. The methane gas created in the process is used to heat the parts of the plant, and the rest of it is burned off.

Kori Thompson, engineering supervisor at the wastewater treatment plant, said many of the digester complex’s parts are originals from its construction in the 1970s and 1980s. The new equipment and repairs will help save energy at the complex and create the biosolids more efficiently.

“We’re looking at it as, ‘What do we need to do to maintain our facilities and proper working order,’ and then also, ‘How do we do it better to save money and to save spend the ratepayers’ dollars wisely?'” Thompson said.

The council will also consider hiring a “manager-at-risk” for the project. Thompson said the process allows the city to bring in potential contractors to view the complex prior to designing the improvements in order to get a cost estimate for the individual projects.

City council members questioned the method of choosing a contractor through those means. Mayor Brian Treece said it seemed unclear of the firm would be accountable to the city for the duration of the project.

Money for the improvements come from a mix of bonds issued in 2013 for sewer projects and current utility money. Assistant utility director David Sorrell said the project was first estimated at $4.1 million in 2013, but grew when they decided to add safety features to the plant. Right now, the plant does not conform to modern safety standards, such as the size of the railings around the top of the digesters. Sorrell said workers face a risk of falling through the skylights of the building and into the machine.

“They’d go right into the building because they’re not up to safety codes,” Sorrell said.