Septic Leachate
Suspected septic leachate contamination in Whitefish Lake was reported in a study conducted by the Flathead Lake Biological Station in the mid-1980s. In 2012. the Whitefish Lake Institute (WLI) published a study that confirmed the presence of septic contaminants at several shoreline locations. The issue has existed for over 40 years, and as more septic systems age and fail, our clean drinking water is at risk.
In response to this ongoing threat to water quality, the Flathead Basin Commission (FBC) (now Western Montana Conservation Commission) developed a Geographic Information Systems (GIS) risk model to assess the density and age of Flathead County septic systems using publicly available data. The model overlays physical risk factors such as depth to groundwater, soil suitability, slope, and distance to surface water.
Data from the FBC model shows roughly half of the permitted septic systems in the basin will soon be older than 30 years. The model’s data corroborates the areas of concern on Whitefish Lake identified by the 2012 WLI report.
While water quality monitoring identifies the presence of septic leachate in waterbodies it does not identify the source of the contaminants. To better address this question, WLI and FBC partnered with Cornell University to conduct a pilot Synthetic DNA study on Whitefish Lake and Lake Mary Ronan in 2022. Synthetic DNA tracers are benign and have a unique signature and allowed the research team to pinpoint contamination sources in the upland area. Of all tracers introduced into participant septic systems, all were found in the lake. WLI also partnered with the Flathead Lake Biological Station on a pilot pharmaceutical and personal care product sampling on Whitefish Lake where dozens of chemical compounds were found in the water.
WLI also participated on a team funded by a National Science Foundation Smart & Connected Communities grant to explore solutions to the septic issue. The group hosted a septic leachate summit in May 2022 at the Flathead Lake Biological Station. Experts from across the nation shared information to develop strategies.
