Potential for Community Well Contamination from Impaired Stream Capture in the SE Piedmont

Kuyu, Kagan and Forsythe, Randall D., Dept. of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, rdforsyt@email.uncc.edu

The southeastern region of US. Piedmont aquifer system typically supports 6 to 8 wells with safe yields adequate for small community well systems (15-200 homes). In a 5 year, multi-stage, project funded in part from Region IV EPA and Gaston County, NC, we have developed a GIS-based delineation methodology for estimating wellhead protection areas (WHPA) in a manner consistent with simple shape approaches, as outlined by State/EPA guidelines. The WHPA is constrained in sized by available recharge (reflective of landcover and community well interference) and has an elliptical form due to fracture-influenced K anisotropy. The estimated protection areas are, to a first order, the capture zones (or recharge areas) for these community wells. In the county there are 237 permitted community well systems, or 1 well/ 4 sq. km. We are currently engaged in modeling the potential impairment of well water quality from various sources. One obvious source of potential contamination is from the discharge of waste-water from the counties 112 NPDES sites. Many of the NPDES receiving streams are 1st to 2nd order creeks with class C waters (unfit for human contact). A GIS analysis of potential stream capture by community well systems reveals that 81 of the 237, or 34%, of the WHPAs overlap with stream channels with perennial flow. In total 54 km of largely Class C streams are estimated to supply water to permitted community wells. Impact on water quality can estimated by the fraction of the WHPA that is cutoff from the well by the stream segment. Volumetric fractions in excess of 40% of total capture are likely to be from stream flow in some cases; predicting significant impact and impairment of tap water. In the future finite element flow modeling, followed by field validation, will be conducted to verify and quantify the level of impairment.