Dayton has shuttered two Mad River well field drinking water production sites over fears of the potential for contamination from a firefighting foam contaminant that could eventually threaten dozens of additional groundwater wells, a city leader said.
Dayton stopped pumping drinking water at seven groundwater wells at the Huffman Dam well field last April where an early warning groundwater monitoring network showed per- and polyfluoroalkyl (PFAS) substances city officials believe were part of a contamination plume migrating from Wright-Patterson Air Force Base.
The two sources of separate contamination could eventually poise a threat to dozens of city groundwater wells in the Mad River well field, Dayton authorities said.
The Huffman Dam and Tait’s Hill well fields — more than three miles apart — are the “bookends” of the city’s Mad River well field system that counts more than 60 groundwater drinking wells, officials said.
If Dayton detects PFAS contamination over the threshold level of 70 parts per trillion in monitoring well between the fire training site and the operating production wells, it must alert the Ohio EPA and sample the production wells closest to the contamination, Butler added.
Dayton also must determine if the firefighting training site is the source of detected PFAS levels of less than 10 parts per trillion at the Ottawa treatment plant by submitted a work plan by April 30, Butler wrote.
A May 2017 sampling of groundwater monitoring wells at Tait’s Hill found at least one sample registered 1,200 parts per trillion – similar to hot spots found inside Wright-Patterson, Dayton officials said.
The Environmental Protection Agency health advisory threshold for lifetime exposure in drinking water is 70 parts per trillion.
A city-owned early warning system of monitoring wells at Huffman detected at least one sample with 35 parts per trillion of the contaminant, according to the city.
“It warns us in enough time that we can mitigate a problem before it actually reaches the (drinking) production wells.” Dickstein outlined the two sources of contamination in a Feb. 21 letter sent to city managers.