Investigating groundwater recharge to the Cambrian-Ordovician aquifer through fine-grained glacial deposits in the Fox River Valley, Wisconsin

Unlithified glacial sediment covers a large part of the landscape along the Fox River valley in east-central Wisconsin. Most of this sediment consists of silt and clay which can limit infiltration of surface water to recharge important bedrock aquifers in the region. The thickness of this fine-grain sediment varies dramatically over the region, from a few to a hundred meters, and surface water infiltration is thought to occur only where the sediment is thin (LeRoux, 1957; Krohelski, 1986; Batten and Bradbury, 1996). To test this idea, a series of multilevel (nested) monitoring wells were installed at various locations in a well-defined area in Outagamie County where the thickness of fine-grained sediment varies. Data collected from the wells, including hydrogeologic and chemical analyses of groundwater samples, reveal that where the sediment is thick (>100 feet, ~30m) there is virtually no infiltration of surface water to deep bedrock aquifers. However, where the sediment is thin (<50 feet, ~15 m), infiltration of surface water does occur and may be responsible for the majority of recharge to bedrock aquifers. This result also has implications for land use planning issues such as landfill siting and manure management. In this report we present the results of our study and use depth to bedrock geology data to identify potential areas of groundwater recharge in Outagamie County.