Early Tests of Drinking Water Promising

A preview of results from well water samples taken across the peninsula reveals nothing alarming with the safety of the groundwater that is the primary source of drinking water for nearly all county residents and visitors.

“As of right now, we’re pleasantly surprised with the data, particularly with the PFAS and the nitrates,” said Sheryl Stephenson, project hydrologist with GZA GeoEnvironmental. “At this point, nothing is screaming out at us.”

Stephenson presented the groundwater sampling protocol and preliminary screen results to the full Door County Board of Supervisors, Jan. 23. The datasheets she presented for the nitrate sampling, for example, showed 61 detections out of 89 samples, all but two of those below safety standards. For PFAS, there were 10 detections out of 89 samples, with one of those exceeding safety standards; and arsenic showed up in 15 out of 89 samples, one exceeding standards and in this case, significantly so, at three times acceptable safety levels.

“We want to look at that more,” she said.

A total 173 volunteers signed up for the well testing. Of those, 89 were selected for sampling for the first go-round. Source: GZA GeoEnvironmental.

Stephenson and the GZA team will be looking at a lot more throughout the course of a four-year Door County Groundwater Sampling Protocol and Preliminary Screening project the county hired GZA in May 2023 to perform. The first year of sampling was expected to be broad, with more focus on subsequent years on areas of identified concern. The testing will vary on a well-by-well basis, but the list includes sampling for per- and poly-fluorinated substances (PFAS), polycyclic aromatic hydrocarbons (PAHs), quantified total coliform and E. coli bacteria, nitrate and nitrite, arsenic, chloride, pesticides, personal-care substances, pharmaceuticals and eventually, Stephenson said, phosphates.

One of several data summaries presented to the Door County Board of Supervisors, Jan. 23. Source: GZA GeoEnvironmental.

The goal of the project is to screen private wells for the contaminants – there are approximately 8,000 private wells on the peninsula, according to Greg Coulthurst, Door County Soil and Water Department (SWCD) conservationist – to understand more about their occurrence and distribution. Existing data on groundwater in Door County is “relatively inconsistent and primarily based on accounts of historic groundwater contamination events,” with no information on emerging contaminants – such as forever chemicals like PFAS – or the concentrations that might exist in the drinking water supply, Coulthurst wrote in a summary of the four-year project. 

Door County’s fragile karst geology lends itself to a high potential for groundwater contamination due to thin layers of topsoil over features like fractured bedrock, sinkholes, caves and wetlands. 

“Any surface activities in areas of thin topsoil do have the potential to impact the aquifer below,” Stephenson said – with even more potential for contamination in Northern Door County where the soils are thinnest, she said.

For the first of the 2023 testing, 173 volunteers signed up from Brussels to Washington Island. Wells were selected based upon parameters that included well depth, topsoil thickness and proximity to sites like orchard mixing sites, orchards, active mines and landfills. 

The sampling was free for the well owners and all chosen participants received a copy of their results.

The new study is separate from the Door County Well Monitoring Program that’s performed by the University of Wisconsin-Oshkosh. The most recent 2023 results from that program’s ongoing testing – presented to the Door County Land Conservation Committee in December – showed similar results to GZA’s preliminary data. For nitrates for example, only three of the 114 wells tested showed levels unsafe for drinking, one of those on the eastern side of the peninsula in Sevastopol, the other two south of Sturgeon Bay. 

“Our results are similar to UW-Oshkosh and the difference is, we did the sampling; Oshkosh sent them out to homeowners [who sample themselves],” Stephenson said. 

The difference in methodology between professionals and homeowners could yield different results given the short window to get samples to labs and how easily kits can become contaminated. Stephenson said she was at one property for well testing and the homeowner asked her if she would take the test for him with the kit he received. 

“He rolled it across his basement floor,” she said. “Those containers are highly susceptible to bacteria. You can’t do that.”

The Door County Board of Supervisors authorized the four-year study in May 2023 after the SWCD reviewed two bids earlier that month, and selected GZA. The study costs $357,700 and the SWCD is paying for it with its portion of county-allocated, American Rescue Plan Act (ARPA) dollars (leaving an available ARPA balance for the SWCD, at that time, of $291,139.05).