Assessing Seasonal Variations in Recharge and Water Quality in the Silurian Aquifer in Areas with Thicker Soil Cover

Background: The fractured Silurian dolomite aquifer is an important, but vulnerable, source of drinking water in northeast Wisconsin (Sherrill, 1978; Bradbury and Muldoon, 1992). Well contamination events in the Town of Morrison in Brown County (Green Bay Press Gazette, Feb 8, 2006) and Cooperstown in Manitowoc County (Green Bay Press Gazette, May 12, 2008) refocused public attention on the aquifer’s susceptibility to contamination. In both events, it appears that manure-contaminated recharge impacted several domestic wells completed in the underlying dolomite aquifer. In Cooperstown, 17 of 31 wells sampled during the March 2008 snowmelt event tested positive for E. Coli bacteria. While these events generated media attention, they are not isolated incidents. Historically, “brown-water” events during spring have been noted in several other counties underlain by the Silurian aquifer — specifically in Door, Calumet, Kewaunee and Manitowoc Counties (Erb and Steiglitz, 2007). In response to these events, Kevin Erb of UW-Extension organized a Northeast Wisconsin Karst Task Force that was charged with developing recommendations for best management practices (BMPs) that would help minimize groundwater contamination in areas underlain by shallow carbonate aquifers with specific attention to BMPs relating to the storage and application of animal wastes.