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Groundwater and Well Information

In 2006, the Town of Morrison experienced a never before seen well contamination problem. Over 34% of the wells tested exceeded the state drinking water standard for nitrate/nitrite (ppm N) of 10 ppm and 19% tested positive for bacteria. While the Department of Natural Resources offically stated that the source of the problem was undetermined, the karst features in the area proved that significant well contamination issues could continue to plague the area.

Karst is any terrain based on a layer of soluble
bedrock, usually, though not always, of carbonate rocks. In Brown County, and most of northeast Wisconsin, karst forms on limestones (calcium carbonate) and dolomites (magnesium calcium carbonate), found primarily along the Niagara Escarpment or as locally refered to as "the ledge". Common natural Karst features include:
  1. Sinkholes - Depressions in the ground surface caused when sediment overlying the bedrock washes into bedrock into bedrock channels and cavities or by the collapse of cave roofs. Sinkholes vary in size and have slopes ranging from gradual to severe. Surface water draining into sinkholes can enter nearby wells quickly.
  2. Bedrock outcroppings - Limestone or dolomite bedrock protruding from the ground surface.
  3. Springs - Water flowing out of the ground from subsurface flow paths.
  4. Disappearing or sinking streams - Small surface streams that enter subsurface flow paths.
  5. Earth cracks - Cracks from a few inches to several feet formed when a limestone formation leans toward an unsupported area such as a valley.
  6. Flaggy soil - Soil with "flags" of small limestone pieces mixed with the soil. The mapping of flaggy soils is a useful indentifier of linestone bedrock a short distance beneath the surface.
Since the well contamination outbreak in the Town of Morrison in 2006, the Brown County Land and Water Conservation Department (LWCD) has been working to protect Morrison's drinking water from contamination due to the abundance of karst features and other groundwater conduits that are prevalent in the area. Locating these features provided the LWCD the opportunity to create an Agricultural Groundwater Management Zone Map (AGMZ) of Morrison showing which areas are more prone to groundwater contamination. The first AGMZ map was produced in 2006 and then revised again in 2011. Approximately 13% of the land in the Town of Morrison has been field verified for karst features and other groundwater conduits. These AGMZ maps are a great tool for potecting the groundwater in Morrison but are not yet complete. Other maps created include a depth to bedrock map, closed depressions map, and a percent slope map.

Karst makes for beautiful scenery, but it is very vulnerable to groundwater pollution, due to ease of water flow. Natural filtration is nearly non-existent in karst areas. To make matters worse, cave conduits act as natural sewer lines, and sinkholes become personal garbage dumps in small towns and rural areas, which puts the local drinking water supplies at risk. It is only recently that these problems are beginning to be addressed.


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