An Analysis of Arsenic Replacement Wells to Determine Validity of Current Department of Natural Resources Guidance

Background/Need: The occurrence of arsenic in groundwater in parts of Northeast Wisconsin was first identified in 1987 during a routine feasibility study for a proposed landfill location in the town of Vinland, Winnebago County, and has been an ongoing problem since that discovery. Drinking water wells near the proposed landfill site were sampled for background parameters to develop baseline data on groundwater quality in the area. When many of the samples were found to have higher arsenic levels than would be expected for background parameters, an investigation ensued and it was determined that the arsenic in this area 1s naturally occurring. Since that time, several studies have been undertaken to determine the extent of the problem. Some of these studies have focused on providing solutions to property owners who rely on private wells for drinking water and well drillers who need to be able to advise their customers on the best well drilling techniques to prevent or dramatically reduce the amount of arsenic in potable wells. Based on these studies, the Wisconsin Department of Natural Resources (WDNR) delineated an Arsenic Advisory Area (AAA) and provided recommendations for drilling wells in this area. To determine if the WDNR’s recommendations were having the intended result of eliminating or dramatically reducing the amount of arsenic in potable wells, it was necessary to conduct arsenic sampling of wells in the AAA that were constructed according to these recommendations and compare these results to other wells in this area that were not constructed with any precautionary measures. This study attempted to test the validity of the WDNR’s recommendations, and ultimately to advise the WDNR if the guidance should become mandatory or if modifications to the guidance are warranted.