Final designs are complete for the City of Whitefish’s water treatment expansion project and the city will soon be accepting bids on the project.

City Council last week approved the estimated $9.6 million project.

The city is being required by the Montana Department of Environmental Quality to complete the upgrade to increase its water treatment capacity at the plant. Construction for the project is expected to begin in August.

Public Works Director Craig Workman said the city only hits its peak water treatment capacity a few days per year during peak demand, but it’s being required to increase its firm capacity to allow for water main extension and future growth.

A Trident treatment units system has been selected for the plant expansion and are similar in operation to the existing treatment units at the plant. Adding treatment units at the plant requires expansion of the treatment building and minor rehabilitation of the current units.

Implementing treatment units similar to what’s already existing has advantages, according to Workman, including familiarity of operations for staff, continued production of high-quality water with a relatively simple operation and continuity of operation between the new and old treatment units.

The expansion of the plant will include space for four 1 million gallon per day treatment units, but only two units are being installed at the current time.

The project, designed by engineer Morrison-Maierle, includes a suite of work in addition to the actual expansion of the plant. It also involves the expansion of the city’s water intake pump station at Whitefish Lake, installation of a parallel water main to the water treatment plant and an extension of the city’s sanitary sewer to the water plant.

Increasing the water source intake capacity includes retrofitting new pumps, piping, values and electrical controls into the existing pump station.

A new 24-inch parallel water main is required to provide adequate transmission of main capacity water into the distribution system. The systems’ current 18-inch main is not large enough to convey the water at full build-out capacity of the plant.

An extension of the city’s sanitary sewer to the water treatment plant is necessary to coincide with the plant expansion. Workman said as water demand increases and the city relies more heavily on the lake for water it will subsequently require more frequent backwashes, and additional plant capacity also increases the amount of backwash waste generated.

The Montana Department of Environmental Quality last spring began prohibiting any new water extension or connections due to concerns that the city was approaching its threshold for water storage and water source treatment capacity. In August, DEQ granted the city a deviation variance that allows new water connections again while the city works to increase its water system capacity.

Whitefish operates what’s termed as 3 million gallons of firm capacity water treatment plant that treats water drawn from Second and Third creeks in Haskill Basin and during peak usage times from Whitefish Lake.

The expansion will add two additional 1 million gallon per day treatment systems, bringing the plant’s firm treatment capacity to 5 million gallons per day, which is calculated with one filter taken out of service.