Evaluation of the Potential for Arsenic Release in Two Cones of Depression in Northeastern Wisconsin

Project Objectives
This study is a collaboration between the University of Wisconsin – Green Bay (UWGB) and the Wisconsin Geological and Natural History Survey (WGNHS) which is part of UW – Madison, Division of Extension. This study focuses on evaluating groundwater management strategies associated with two cones of depression in the Green Bay – Fox Cities region, which is part of the Northeast Groundwater Management Area (GMA). In the northern part of the GMA, drawdown in the confined sandstone aquifers has been recovering since the late 2000s, as a result of the villages surrounding Green Bay transitioning municipal water sources from groundwater to surface water. In the southern part of the GMA, continued groundwater use has sustained a cone of depression near the Fox Cities, including Kimberly and Kaukauna. The overall goal of this study is to evaluate how groundwater recovery or continued drawdown impacts groundwater quality in these two regions of the GMA, with a focus on metals concentrations. This project builds upon previous studies in the confined sandstone aquifer, but takes a unique focus evaluating water quality at a downdip portion of the aquifer farther from the recharge area, within cones of depression that may have (historically or currently) dewatered portions of the Ancell Group. Project deliverables include installation of a monitoring well in the southern region of the GMA, a summary of groundwater chemistry in the region, an evaluation of the aquifer dewatering in the region, and results from a suite of batch leaching experiments with well cuttings. Results from this 18-month study lay the groundwork for continued evaluation of groundwater resources and water quality in the Northeast GMA.

The main objectives include:

1. Facilitate improved monitoring in the southern cone of depression in the Northeast Wisconsin Groundwater Management Area (GMA) by installing an additional monitoring well.
2. Determine potential water quality risks associated with oxidative metals mobilization through analyzing well water chemistry and conducting batch experiments with aquifer materials.
3. Evaluate aquifer water connectivity using water chemistry data from existing well data and 19 additional wells sampled in this study.
4. Evaluate areas of the GMA at risk of dewatering and potential arsenic and other metals release.