MISSOULA — A Flathead Lake watchdog group and the Confederated Salish and Kootenai Tribes are suing the state of Montana for approving a new sewage treatment plant that they say could add nutrient pollution to Flathead Lake.
On May 28, Citizens for a Better Flathead and the CSKT filed a complaint in Flathead County District Court alleging that the Montana Department of Environmental Quality issued a discharge permit for a new wastewater facility without properly analyzing how the nutrients in sewage — nitrogen and phosphorus — could seep through the ground to degrade nearby Ashley Creek and Flathead Lake.
“DEQ’s refusal to evaluate best-available science demonstrating inappropriate levels of treatment and a terrible disposal location for massive volumes of new pollution near Flathead Lake is a disservice to citizens and taxpayers, and a real threat to the Flathead’s cherished water quality and its economy,” said Mayre Flowers, Citizens for a Better Flathead executive director.
Flathead County is one of the fastest-growing counties in Montana, and its infrastructure is struggling to keep up with the surging influx of people. Since 2020, Flathead County has gained more than 10,100 new residents, according to the U.S. Census. The city of Kalispell has grown almost 25% since 2020 and Kalispell City Manager Doug Russell told the Daily Montanan a few weeks ago that the public works department is using growth models ‘to anticipate where we’ll need to prioritize infrastructure projects.”
Many new subdivisions are built with individual septic systems, which can add nitrogen and phosphorus pollution to groundwater. For example, a DEQ water quality assessment of the Flathead-Stillwater watersheds estimates that more than 3,350 septic systems exist in the Lower Ashley Creek watershed between Kalispell and Flathead Lake. Lower Ashley Creek is impaired because of nutrients, and those septic systems contribute 15% of the nitrogen and 20% of the phosphorus loads in Lower Ashley Creek.
Nitrogen or phosphorus compounds, collectively called “nutrients,” can be harmful in excess amounts and can feed the growth of various algae called algae blooms. When significant amounts of algae infest streams or lakes, the resulting low concentration of oxygen dissolved in the water can kill fish and other aquatic organisms. Blue-green algae can also release toxins that can poison fish and people.
DEQ's water-quality assessment, called a Total Maximum Daily Load assessment or TMDL, calculates the extent to which various types of pollution should be reduced to ensure waters are clean enough to support aquatic life or human use. Until that happens, no more pollution should be added.
Ashley Creek empties into Flathead Lake, which has its own TMDL that calls for a 25% reduction in nitrogen and phosphorus loads from tributaries and human sources to prevent algal blooms and preserve water quality.
Fortunately, some subdivisions are connected to sewer systems, which tend to be less polluting than septic systems due to water treatment. But some treatment plants in Flathead County are already maxing out.
Since septic systems aren’t really regulated, it’s difficult to reduce their contribution to pollution. But treated wastewater is regulated through the use of discharge permits. So, before a discharge permit is issued, the Clean Water Act requires the state to ensure that wastewater is cleaned prior to entering impaired waters such as Ashley Creek to prevent the addition of more pollution.
In September 2023, Flathead County set out to improve its sewage infrastructure and bought property on the banks of Wiley Slough, which feeds into Lower Ashley Creek, to build a treatment facility large enough to accept septage from across the county. The county also contracted with Lakeside County Water and Sewer District to run the facility and dispose of the wastewater. However, the district would need to obtain a wastewater discharge permit from DEQ before Flathead County would pay $23.5 million to build the facility.
In December 2024, DEQ published a draft permit that would allow Phase 1 of the new facility to discharge 200,000 gallons of wastewater per day into the groundwater. The accompanying fact sheet said the aquifer was “hydrologically connected to surface waters.” So the wastewater would eventually surface, enter Ashley Creek and, ultimately, Flathead Lake.
DEQ said that wouldn’t be a problem, because the wastewater would be cleaned of nutrients while underground. So DEQ said the discharges were nonsignificant, and therefore only a basic environmental assessment was needed.
But that’s where Citizens for a Better Flathead disagreed in their complaint. Using findings from studies carried out by independent companies, they say DEQ’s groundwater modeling was flawed. It assumes the subsurface soils are all the same and doesn’t account for a greater volume of groundwater pushing through due to the addition of wastewater.
DEQ said it would take 3.5 to almost 8 years for nitrogen compounds to seep into Wiley Slough and Ashley Creek, but the companies say it could percolate faster so the remaining nutrients could pollute downstream waters. Plus, there are plans to eventually expand the facility to increase the discharge rate to 900,000 gallons per day.
“DEQ's decision also wholly ignored record evidence from experts identifying fatal flaws in the water quality modeling on which its nonsignificance finding rests. In doing so, DEQ failed to consider all pertinent data and made a clear error of judgment,” the plaintiffs alleged in their complaint.
The plaintiffs also assert that DEQ should have analyzed the cumulative additions of nitrogen and phosphorus from all sources, particularly as they affect Flathead Lake. The CSKT have jurisdiction over the southern half of Flathead Lake and use both narrative and numerical water quality standards to control nutrients so the water “can support the growth and propagation of salmonid fishes and associated aquatic life.” According to the complaint, DEQ didn’t analyze whether the additional discharge would affect Flathead Lake, so it couldn’t say whether the permit would cause nutrient levels to worsen in the southern end of the lake.
Both plaintiffs submitted their concerns before DEQ issued the final permit on April 28. Now, they ask the court to void the discharge permit and to find that DEQ violated the Clean Water Act and the Montana Environmental Policy Act.
Citizens for a Better Flathead also recently sued the Lakeside County Water and Sewer District for not properly informing the public before approving construction of another wastewater treatment facility for a proposed resort and golf development above Lakeside.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.
