City Commissioners voted unanimously during their April 21 meeting to approve a $4,734,600 contract to COP Construction for upgrades to the sedimentation basins at the water treatment plant.
The project will replace two of the oldest mechanical settling basin components within two existing sedimentation basins of the plant.
Last year, the city hired Advanced Engineering and Environmental Services, Inc., or AE2S, to design, facilitate bidding, provide construction administration and complete as-built drawings for this project.
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The water treatment plant, at 1301 Lower River Road, treats Missouri River surface water using conventional flocculation, sedimentation, filtration and disinfection processes.
The facility has five settling basins, four of which were built in the 1930s and one in the 1950, Chris Gaub, city public works director, told commissioners during the meeting.
Within the basins is a mechanical chain and skid system, that dates to the 1930s, using steel chains and pulleys to collect and remove the sludge that settles at the bottom.
Gaub said that because of the system’s age, they’re seeing failing components and replacement parts are increasingly difficult to find.
He said some pieces have to be custom-fabricated, increasing cost and time.
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Gaub said construction would start in the fall, during lower usage months, so the plant remains operational. Approving the contract now also allows for long lead times for some components.
City staff anticipated a significant mechanical failure in at least one of the existing basins within the next three years, according to the staff report.
The existing five basins have a capacity of 38 million gallons daily.
The two upgraded bins will have an estimated capacity of about 54 million gallons daily, without using the remaining three basins, according to staff.
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The remaining three basins will remain in place to be repaired and updated as funding is available. They’ll serve as backup or potential future plant capacity if development increases demand.
Other Montana cities are already using, or upgrading to, similar systems, according to city staff.
It’s a “high priority upgrade,” Gaub said, and if a basin failed during the summer when usage is high, the plant would lose about 8 million gallons per day of treatment capacity, which would likely lead to water restrictions.
He said the project will improve water quality at the front of the treatment process, protecting downstream components such as the filter media the city replaced recently.
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Commissioner Shannon Wilson moved to approve the contract and said she was happy to see improvements, since there’s some “ancient equipment,” in the plant.
She said the project won’t trigger rate increases.
The city received three bids for the project with COP Construction providing the lowest bid.
The project is prioritized in public works’ capital improvement plan and is being funded through the state revolving loan fund by issuing $5,020,000 in revenue bonds over 20 years at a 2.5 percent interest rate.
The city will pay the estimated $320,000 of annual debt service with water rate funds, according to the project description.
