Synthetic DNA Study

To validate the results of the septic risk models, the committee recommended conducting a synthetic DNA tracer study to track leachate from specific septic systems. Synthetic DNA are short, unique strands of lab-created DNA that are encased in a biodegradable polymer. The tracers are flushed down the toilets of homeowners who live in close proximity to surface water, and nearshore samples are collected and analyzed to see if tracers are present. Each participating homeowner gets a unique tracer that acts as a barcode for their septic system.

The pilot study began in the spring of 2022 on Whitefish Lake and Lake Mary Ronan because areas surrounding both lakes were found to be high risk according to the septic risk models. Eight homeowners on both lakes agreed to participate, and a groundwater flow and nitrogen plume models were used to determine nearshore sampling locations. Tracers were deployed in the spring, and nearshore samples were collected by staff and volunteers regularly through October.

The results of this study are being analyzed and will inform if similar tracer studies in the basin should be performed. This technology has not been studied before in our ecoregion, so if successful, we would have another tool in our toolbox to better understand septic leachate in the Flathead Watershed. The committee will continue to assess all means of addressing this issue, including but not limited to regulatory modifications, funding and incentives, enhancing training opportunities, and targeted outreach.

FBC staff, Friends of Lake Mary Ronan volunteer, and Whitefish Lake Institute intern take samples for the synthetic DNA study.