Study finds groundwater contamination from septics

Health officials say study has limitations

Rapid population growth in areas of the Flathead Basin not served by wastewater treatment facilities has resulted in a proliferation of private septic systems that could increase the area's risk for groundwater contamination. That was the message delivered by scientists and public health officials at the Flathead Basin Commission's July 20 meeting in Pablo.

Bonnie Ellis and Tyler Tappenback, from the University of Montana's Flathead Lake Biological Station, presented the results of Phase 1 and prospects for Phase 2 from the Flathead Basin Commission's "Mapping the Impact of Septic Systems: A Shallow Groundwater Study."

The commission says it chose to study shallow groundwater systems because they are "an important, but particularly vulnerable renewable resource, subject to a variety of sources of potential contamination."

In Phase 1, experts sampled 17 local wells in the Evergreen area between the Whitefish and Flathead rivers for volatile and semi-volatile organic compounds. Most of the sampled wells showed contamination, including some with traces of chloroform, arsenic or uranium.

Although the team gathered valuable data, further research is needed before researchers can issue definitive conclusions about the Flathead's complicated water systems, Ellis said.

"The complexity of the underground, particularly its connection to the river, makes it very difficult to get a handle on the system," she said. "It wasn't surprising to us that the data was very spotty. This is just a snapshot."

Phase 1 data also indicated that treatment-resistant pharmaceuticals and personal-care products could become a problem within the Flathead Basin. Acetaminophen, sunscreen, bug spray and caffeine are among the personal-care products found in Flathead wells.

"Those products are going right through the sewage treatment systems, so there's a potential source of contamination - and it goes right back into the aquifer," Ellis said.

Phase 1 cost about $23,000 to complete. Phase 2, which has been allocated $100,000, will examine similar issues, but in greater detail, Flathead Basin Commission executive director Caryn Miske said. Water samples will be processed at a lab equipped to detect lower levels of contaminants. Plans for a third phase have been put on hold until additional funding can be lined up, Miske said.

Government response

Officials from the Flathead City-County Health Department and the Montana Department of Environmental Quality caution that information from the study does not mean water in Flathead County is unsafe for drinking. They noted that samples were taken from a small group of shallow wells in an area of the valley known to be vulnerable to seepage from surface and ground sources, septic tank leakage and other pollution sources.

"The majority of public water supply wells generally take water from deep aquifers that are not subject to the same problems," noted Shelley Nolan, at the DEQ's Public Water Supply Program

Nolan also pointed out that public water supplies are routinely tested for all regulated contaminants. Many of the contaminants listed in the report currently are not regulated and would require further study to determine safe levels in drinking water.    

Flathead County Health Officer Joe Russell said it's not uncommon for unprotected wells to show pollution, especially shallow wells. In fact, DEQ will not approve new wells that are not at least 25 feet deep for public use or in new subdivisions, he said.

Landowners concerned about their private wells should test their water annually for coliform bacteria and nitrates. Additional testing can be done for contaminants that may be specific to the area.

Well owners should also test their water if there is a change in the water's taste, odor or appearance, after the well system is serviced, or after a flooding event. Information about how to collect samples is available at the closest water quality district, the local county health department, or from DEQ.

For more information visit online at www.deq.mt.gov/wqinfo/swp/StayWellCkYourWell.htm.