Hello, Beacon readers! I’ve been following the progress on Lakeside County Water and Sewer District’s new wastewater treatment facility, which has been in the works since 2021. Because the proposed site of the facility is located a mile north of Flathead Lake, it’s garnered some controversy along the way. (If you’re fuzzy on the details of how this all started, scroll to the bottom of the newsletter for some background in the archives.)

One of the more controversial components is the method of wastewater disposal proposed – rapid infiltration basins (RIBs). Without getting too deep in the weeds here, the system essentially allows treated wastewater to seep into groundwater through the soil. It’s cost-effective, takes up less land area, and it requires a more intensive wastewater-treatment protocol than what the district is currently using — all qualities that district members have put forward to explain why they’ve adopted the proposed plan.

There’s been a missing piece from this puzzle, however – exactly how will the district treat the water before it enters the RIBs?

The district’s board members finally answered that question during their last meeting on Aug. 21.

During the packed meeting, district engineers Brad Koenig and Austin Wargo presented three different options for treatment: a membrane bioreactor, a sequence batch reactor and an oxidation ditch. The district selected a sequence batch reactor that operates using cycles, or batches, where the treatment and settling of solids occur in the same tank.

Compared to the other two options, the batch reactor technology requires a smaller footprint, consisting of three basins with dimensions of 67 feet by 67 feet. The sequence batch reactor method also allows operators to change the flow quickly and easily, adjusting for flow variability and load conditions.

The capital cost of the treatment is estimated at $18.7 million, cheaper than the other two options. Operation and management costs are currently priced at $314,700, which is a midpoint between the oxidation ditch’s $288,100 and the membrane reactor at $456,300. It’s the same treatment used by the city of Whitefish and in Glacier National Park’s administrative headquarters in West Glacier, as well as facilities near Lake McDonald.

In public comment, Flathead Valley residents reiterated concerns about the treatment and location of the site. Craig Spencer, a retired scientist who spent more than 20 years researching freshwater ecology in the Flathead Basin, called the proposed design likely to result in “cleaner effluent” than the current facility. He had reservations, however, that the RIB system would fail, with wastewater traveling through the area’s unique network of aquifers — a water quality scenario that an independent report suggested the Montana Department of Environmental Quality (DEQ) failed to consider in approving the facility’s groundwater discharge permit.

“I think there’s risk that the proposed groundwater injection will not achieve the desired results,” Spencer said. “I think the risk of failure will increase rapidly as the plant ramps up to treating 900,000 gallons per day. Along the way I think we’re gambling with water quality and Flathead Lake.”

When the district’s board members questioned engineers on the three options, they were informed that the treatments were equal in their viability for the area, considering the proximity of Flathead Lake.

In a unanimous vote, board members approved construction of a 600,000-gallon-per-day plant with sequence batch reactor technology, with aluminum sulfate as an additional treatment process. The plan will include space for potential expansion to 900,000 gallons per day.

I’m Zoë Buhrmaster – let’s get our heads out of the sewer and into the rest of today’s Daily Roundup.