ADAPTING TO PFAS CONTAMINATION OF PRIVATE DRINKING WATER WELLS NEAR A PFAS PRODUCTION FACILITY IN THE ATLANTIC COASTAL PLAIN OF NORTH CAROLINA

Elevated concentrations of per- and polyfluoroalkyl substances (PFAS) have been observed in private drinking water wells within a 40-km radius of the Chemours PFAS manufacturing plant. Almost 7,000 such wells are known to be contaminated with PFAS. We evaluated whether the water quality in deeper aquifers supports their use for drinking water, as an alternative to shallower PFAS-contaminated wells in the Chemours area.

Groundwater quality data from over 100 wells show that Cl concentrations increase and GenX concentrations decrease with increasing depth through the 4 aquifers in the area (surficial to Black Creek to Upper Cape Fear to bedrock). The bedrock aquifer was also relatively low in Fe and Mn. Well yield was similar and adequate in all 4 aquifers.

A more detailed look at groundwater quality based on 143 constituents in 9 deep wells (2 Upper Cape Fear, 7 bedrock) showed only 18 exceedances of drinking water standards among the 1287 results, and 9 of the 18 were exceedances of the 20 mg/L drinking water health advisory for sodium. In the bedrock aquifer, the only other exceedances were 4 values slightly over the secondary MCLs for Mn (2) and Cl (1) and primary MCL for gross alpha (1).

Comparison of regulatory responses to PFAS contamination of drinking water between Chemours and three PFAS manufacturing facilities in VT, WV, and NH showed that deeper wells are mentioned as an alternate drinking water source in the VT consent order. VT is currently evaluating if deeper wells, with casing that extends at least 50 feet below bedrock and fully grouted annular space, limit shallow PFAS migration into deeper groundwater.

Over the 20-year period stipulated by the consent order, Chemours could pay up to $93,000 per home for municipal water connection and water use fees, and up to $64,000 to install and maintain a whole-house GAC system. Deeper wells are included in the consent order as an option for public buildings, but not for private residences. A new bedrock well may cost roughly $30,000 which appears to be the most economic option but may be cost-prohibitive for many residents given socio-economic indicators in the area. While the bedrock aquifer generally has good water quality with comparable well yields to overlying sedimentary aquifers, additional testing would be necessary to evaluate its long-term sustainability