Project Number:
DNR-191
Other Project Number:
WR05R016
Funding Year:
2005
Contract Period:
7/1/2006 - 6/30/2007
Funding Source:
DNR
Investigator(s):
PIs:- David Hart, Wisconsin Geological and Natural History Survey
- Kenneth Bradbury, Wisconsin Geological and Natural History Survey
- Daniel Feinstein, USGS
- Basil Tikoff, UW-Madison
Abstract:
Background/Need
Groundwater use in southeastern Wisconsin has resulted in more than 400 feet of drawdown in the deep sandstone aquifer since pumping begin in the 1860’s. Because of this drawdown, the area was designated as a critical groundwater management area in the 2003 Groundwater Protection Act 310. The deep sandstone aquifer is confined by a regional aquitard, the Maquoketa Formation, over much of southeastern Wisconsin. This aquitard is important because it controls how much water can enter the deep sandstone aquifer. Currently pumping from the deep sandstone aquifer is 33 million gallons per day. Of this amount, around 8 mgd is estimated to flow downward across the Maquoketa Formation through poorly understood pathways.
Objectives
We sought to understand how groundwater is flowing across the Maquoketa Formation, whether through multiaquifer wells or the Waukesha fault.
Methods
We conducted two simultaneous investigations to determine whether significant flow can occur through multaquifer wells or the Waukesha fault. Our hypotheses and approach to testing them are below. Possibility 1: Significant flow moves downward through cross-connecting multiaquifer wells. Our approach to explore this possibility included: 1) A records search to identify the number and location of multiaquifer wells in southeastern Wisconsin. 2) A review of well abandonment history to determine how many of these wells still exist. 3) Simulation of the wells using a numerical flow model. 4) A sensitivity analysis to determine the potential importance of the existing wells to the regional flow system. Possibility 2: Significant flow moves downward along the Waukesha fault. Our approach to explore this possibility included: 1) A literature review of the Waukesha fault and the tectonic setting of the Michigan Basin. 2) A field visit to a quarry exposure of the Waukesha fault and other joints and fractures. 3) Incorporation of the Waukesha fault into a regional groundwater flow model. 4) Sensitivity analysis to determine the potential importance of the fault to the regional flow system. 5) Rehabilitation of borehole WK-1376 to allow study of the horizontal fractures through the Maquoketa Formation.