Photo courtesy of GZA Environmental.

After initial rounds of expanded well-testing in Door County, little was found to raise concerns about drinking water quality, a representative of the testing company told the Door County Board of Supervisors on Tuesday.

Last May, the County Board approved a $357,700 contract with GZA GeoEnvironmental Inc. for a private well-testing project. The project’s goal is to get Door County groundwater information up to date. Historically that information is inconsistent, gathered after groundwater contamination events, and only shows known contaminants at the time of the event. 

With approximately 8,000 private wells that get their drinking water from the aquifer below Door County’s crumbly karst geology, hard data about drinking water quality and “emerging contaminants” is of great concern to most residents, according to board discussion last year. 

Emerging contaminants include things like microplastics, personal care products and pharmaceuticals, as well as bacteria, nitrate, chloride, pesticides, herbicides, and PFAS and PAHS. The abbreviations are for perfluoroalkyl and polyfluoroalkyl substances, and polycyclic aromatic hydrocarbons respectively. Both are potentially harmful chemicals found in many common items like nonstick cookware and mothballs. 

The County Board last year allocated $800,000 of the county’s more than $5.3 million total in American Rescue Plan funding to environmental projects. Some of that money is being used for this well-testing project. 

At Tuesday’s County Board meeting, GZA geologist Sheryl Stephenson gave a presentation detailing the results of the first round of tests, which were performed between Sept. 25 and Oct. 12 last year. 

Door County sits on a thin layer of glacial deposits above the aquifer residents primarily get their drinking water from, according to Stephenson, and any activities taking place on top of Door County’s topsoil can easily send contaminants into the underlying aquifer. There are cracks and depressions in this karst layer. Cracks create a direct conduit for anything on the surface to travel to the aquifer. Shallow topsoil compounds this situation, and Door County has very thin topsoil, according to Stephenson. 

Over the last year, GZA publicized the well-testing program and recruited volunteers to have their private wells tested, she said, and 173 homeowners came forward. The 89 wells selected for testing were chosen based on depth and proximity to potential contaminant-producing sites like orchards and landfills, Stephenson said. The selected wells had good municipal representation, she added. 

Certain wells were further analyzed for breakdown products of common herbicides and pesticides, arsenic, and volatile organic compounds called VOCs.

GZA used a couple of standards to compare results, said Stephenson. For PFAs and PAHs, GZA used the Wisconsin Administrative Code regarding maximum contaminant levels. This value is 70 parts per trillion, but the EPA has recently proposed to change that level to 4 parts per trillion. GZA used both standards to be conservative, said Stephenson. 

“We were pleasantly surprised with the data, especially with PFAS and nitrates. Many places in Wisconsin are much higher,” said Stephenson in her report at the board meeting. 

GZA tested for PFAS in all 89 wells, and results were significantly below the 70 parts per trillion. Only one of them exceeded the EPA’s level of 4. Out of 23 wells selected for PAH analysis, only one had a small concentration higher than recommended. 

The project also sampled bacteria from  83 wells, with no detections of high concern. Nitrates, which are often a byproduct of agriculture, resulted in 61 detections. Only two of the detections exceeded drinking water recommendations, but they were not high enough to be of concern, according to Stephenson. 

Arsenic had 15 detections out of 61 wells tested. One of those was three times the maximum recommended concentration in drinking water, and GZA plans to look into that site further in 2024, said Stephenson. The others, though showing some detection, were not high enough to be of concern, she said. 

VOCS sampled from 34 of the wells showed only one detection and above the range of safe.

GZA issued a notification letter with results to each homeowner whose well was sampled. If there was an excess of contaminants in their well, the homeowner also was sent information from the Wisconsin Department of Natural Resources about those contaminants. 

The next round of testing will take place in spring, resampling some of the initial 89 wells and possibly additional ones, both to capture any differences when the water table is higher and flowing, and to survey spatial and historical data trends, said Stephenson. Future sampling will look at microplastics and pharmaceuticals as well, she added. 

Supervisor Jeffrey Miller, who represents parts of the Town of Nasewaupee, asked if results showed any particular areas of concern in the county for contamination. 

“At this point nothing is screaming out at us,” Stephenson said. 

James Drought, a GZA hydrogeologist who accompanied Stephenson during the company’s report, gave credit to the county for the mostly positive testing results. “This has a lot to do with the practices the county conservation department has implemented over the years in preventing releases to the subsurface, and the knowledge that has been promoted by the county itself in preventing releases and maintaining really high water quality,” he said.