Challenge: The City of West Bend relies on nine groundwater wells to supply an average of over 4 million gallons per day (mgd) to 30,000 people. Various Per- and polyfluoroalkyl substances (PFAS) have been detected in three of their wells (Wells 4, 11, and 12), representing nearly 40% of the total supply capacity. West Bend asked INTERA to assist with efforts to obtain grant funding to offset the cost of PFAS treatment and other mitigation measures, and to use available hydrogeologic and environmental site data to determine which wells may be at potential risk for PFAS contamination.
Solution: INTERA performed a desktop evaluation of former and current regulated facilities located within the 10-year contributing zone for the affected wells with operations known to be commonly associated with the use of PFAS. Site records were examined for releases and a risk scale was developed for all potential sources of PFAS contamination within or adjacent to the contributing zones. Together, with analysis of historical water quality, this was used to identify wells at greater risk of potential PFAS contamination. Four solutions were developed including point source treatment, well replacement, and well modification(s), with a total project value of approximately $12 million. In addition, documentation was submitted for inclusion in the Drinking Water State Revolving Fund (DWSRF) Intended Use Plan for Emerging Contaminants.
Results: Study results indicated that two previously untested wells were at risk for potential PFAS contamination. Subsequent testing confirmed the presence of PFAS in one of these wells. Additional hydrogeological assessment work was completed along with packer testing that was conducted in one of the contaminated dolomite bedrock wells. These tasks were completed to determine if the well could be re-constructed to reduce PFAS concentrations and reduce on-going operating costs for planned treatment.
