Well 14 - Chloride Mitigation Project
About the Project
The Water Utility is preparing to initiate a groundwater/borehole characterization study at UW 14. This study is necessary in mitigating the elevated levels of sodium and chloride in the water here.
Well 14 is a water supply well that was drilled and constructed in 1960. Located at 5130 University Avenue, it serves Madison’s West side neighborhoods including Spring Harbor, Old Middleton Greenway, Sunset Village, and Regent. Well 14 also serves the Village of Shorewood Hills and parts of the University of Wisconsin campus.
The well is 715 feet deep and gets water from both the upper and lower sandstone aquifers that exist beneath Madison. Its far west location and high specific capacity characteristics (78 gpm per foot of drawdown) make it an important source of water in MWU’s system. Over the last 5 years, it has supplied an average of 750 million gallons of water annually making it the Utility’s largest producer.
In terms of water quality, Well 14 continues to show a dramatic rise in sodium and chloride levels. Over recent years, concentrations of both ions have steadily increased and it is estimated water pumped from the well will soon exceed EPA recommended guidelines. Road salting applications likely contribute to the elevated sodium and chloride levels pumped at this well.
The well’s borehole was recently logged with a variety of geophysical tools. From this exercise, it was determined that the majority of water produced at this well was coming from several different depths/levels within the upper aquifer. There appears to be very little water originating from the lower aquifer.
Water samples were subsequently taken at these and other depths/levels within the borehole to characterize the quality of the groundwater entering the borehole. Samples were collected under “non-pumping” conditions. Results indicated that the water entering from the upper aquifer is elevated in terms of NaCl while the lower aquifer water is not.
It was determined that additional study is needed to further characterize the quality of the water entering the borehole under “pumping” conditions. The results of this study will be used to formulate an extension of the well’s casing which will alleviate the sodium and chloride levels here. SCS Engineers, a local environmental engineering company, has been retained to assist with the study. Water Well Solutions, a licensed well driller, has been selected to perform the downhole tasks necessary to complete this work. Total estimated cost is $220,000. It is hoped that this study will be complete in March of 2023.