This study addresses concerns of surface water contamination entering a valley-train aquifer used by the Springfield Water Treatment Plant in Clark County, Ohio. Ground water is derived partly from infiltration of surface water through the riverbed of the adjacent Mad River. Of particular concern is biological pathogen Cryptosporidium parvum that is resistant to conventional treatment.
Transient, finite-difference ground water flow modeling and particle tracking are conducted, based on a geologically similar model near Dayton, Ohio. Site-specific parameters used for modeling are derived from previous investigations, pump tests, and gain-loss studies conducted at the SWTP.
Modeling is conducted for a flooding event when the aquifer is most sensitive to surface infiltration. Minimum travel times from Mad River to the production wells were estimated at around a day, but do not account for river bank filtration. The results provide a basis for additional study on the sensitivity of infiltration of surface contaminants.