Several projects planned at Kalispell sewer plant

A leaky roof over the control room. A digester tank losing its fight with corrosive methane gas. And a worn-out sludge press that’s been needing more work than it’s worth.

Kalispell may have doubled the treatment capacity of its wastewater plant for $22 million a few years ago.

But the work doesn’t stop there: The city plans to do some big repairs this spring and summer.

Officials are accepting bids until Feb. 7 to overhaul the plant’s primary digester, a job budgeted to cost $865,000.

The project would open and empty the 50-foot-wide by 32-foot deep tank, redo its internal elastomeric coating, replace its mixer and seal it up with a new concrete lid.

If bids are low enough, the project also would replace various piping, meters, valves and controls on the tank. If not, those repairs will be put in budget requests for next year.

The primary digester is part of the plant’s solids-reduction process. A secondary digester would go online for the six months the primary digester must remain down for the overhaul.

Inside the tank, microbes digest solids sent over from the plant’s primary clarifiers and fermenters. The biological process generates methane gas that is collected and burned to keep the tank a steady 93 degrees Fahrenheit.

Kalispell hired a contractor in the late 1990s to reseal the lid and the top of the tank where methane gathers, a move that bought some time. But the corrosive methane has eaten away at that coating and the tank’s lid.

“It finds the holes and cracks and starts to break it away,” Public Works Director Susie Turner said. “Then it gets through the rebar and the insulation and that’s why we see the lid bulging.”

That deterioration has made the digester lid unsafe for workers to go out and inspect gas piping and other components on it. The digester and its lid were built in 1984 and with the proposed overhaul should be good for 20-plus years.

OFFICIALS PLAN to replace one of the plant’s two belt-driven sludge presses with a new screw-driven press. Kalispell is developing a request for qualifications to select a contractor for that project, budgeted to cost about $560,000.

“We’re trying to wrap that up before June. That’s the goal,” Turner said. “It will be a hard one, but we’ll try. We’re kind of getting a late start on it.”

One of the last steps in the plant’s solids treatment process, the presses are used to squeeze any remaining liquid out of sludge.

“We have two belt filter presses in our system so we’ll replace one with a screw press and use the old one as our backup,” Turner said. “They are old. We’re putting a lot of maintenance into it and they’ve pretty much served their life.”

The city also expects to issue a request for bids for a contractor to replace 11,000 square feet of roof liner over the plant’s control room. That work is budgeted to cost $110,000.

Installed in 1992, the roof liner has deteriorated and quite a few leaks are starting to occur. “We have a busy summer coming up,” Turner said about the projects.

Reporter Tom Lotshaw may be reached at 758-4483 or by email at tlotshaw@dailyinterlake.com.