Madison Water Utility first discovered PFAS at Well 15 in 2017 while conducting limited testing at wells near landfills and the airport. Well 15 located on E. Washington Avenue was shut down in 2019 amid community concerns about PFAS chemicals found there. The utility believes the chemicals detected in that well likely migrated from Truax Air Field, about a mile away.  Since then, in addition to further testing, the utility conducted a Groundwater Modeling Study, a Feasibility Study for PFAS Removal, and is currently evaluating treatment options – granular activated carbon [GAC], ion exchange [IX] or a combined GAC-IX system – to implement.  

Well 15 Feasibility Study for PFAS Removal

The Well 15 feasibility study was completed in April 2021 presented to the Water Quality Technical Advisory Committee and Water Utility Board.

Goals of the study:
  • Evaluate treatment technologies

  • Get a general estimate of upfront and ongoing costs for effective treatments

  • Provide a recommended treatment design that would:

    • Remove PFAS.

    • Remove PCE and TCE, eliminating the need for the air stripper system that’s currently set up at Well 15.

    • Allow 1000 gallons per minute of water to be produced from the well.

Study results:

A granular activated carbon system was the recommended treatment technology.

  • Granular activated carbon successfully removed PFAS, PCE, and TCE.

  • The estimated initial cost of the recommended system was $825,000.
    Note: This is a general estimate for the treatment system only. There would be additional costs to modify the building at Well 15 because it is not tall enough.

  • The estimated ongoing costs would depend on how frequently the carbon is replaced. The preliminary estimate was $50,000 to $300,000 a year.

  • The major components for the recommended system (ex: bag filter units, steel pipes, tank) have a life expectancy of approximately 30 years.

Read the full report:  Well 15 Feasibility Study for PFAS Removal: Bench-Scale Testing Report

Next Steps

Madison Water Utility is working with an engineering consultant – AECOM – to evaluate different treatment options (GAC and IX) to identify the best, most cost-effective solution to meet water supply needs on Madison’s east side.  Preliminary design concepts for a treatment system are expected in fall 2022.  Planning and final design will continue into 2023 with construction of a treatment system planned for 2024.


Well 15 Testing

In 2017, Madison Water Utility first detected low-level concentrations of PFAS at Well 15. Five PFAS [PFOA, PFOS, PFHxS, PFBS, and PFHpA] were found at an estimated total concentration of 35 parts per trillion (ppt).  Previously, PFAS were detected at high levels in shallow groundwater at the Truax Air National Guard base, which sits just one mile from Well 15.As the testing technology advanced, the utility increased the number of PFAS tested from six to eventually test for 36 PFAS compounds.  To date, thirteen different PFAS compounds have been found at Well 15.

In 2019, WI Department of Health Services recommended groundwater standards for PFOA & PFOS at 20 ppt.  In 2020, DHS recommended groundwater standards for an additional 16 PFAS, and proposed a Hazard Index approach to assess potential risk associated with exposures to mixtures of PFAS.  

Wisconsin DHS recommends taking action to reduce exposures to PFAS if the Hazard Index is greater than 1.  The calculated Hazard Index for Well 15 is 1.1 while the index at other Madison wells ranges from 0 to 0.2.  

  • View the 2021 Hazard Index figure here PDF .

Well 15 has been out of service since March 2019 due to PFAS.  The Hazard Index value of 1.1 prompted Madison Water Utility to keep the well off-line and ultimately add a treatment system to remove PFAS.  Madison Water Utility will be applying for funding under the Bipartisan Infrastructure Law to help pay for the treatment system. 


Well 15 Modeling & Groundwater Study report

This groundwater study was initiated by Madison Water Utility to evaluate the time of travel for PFAS contamination from the Truax Air Field to Well 15 and update the Well 15 capture zones to determine if Truax could be the source of PFAS at Well 15.The study confirmed that Truax is inside Well 15’s groundwater capture zone. It also showed that the time of travel for groundwater from Truax to Well 15 is about 35 to 50 years. Based on the study, Madison Water Utility concluded that Truax Air Field is the likely source of low levels of PFAS detected at Well 15.