Evaluation of aquifer interconnection from aquifer characteristics computed by using specific capacity data within the vicinity of the Tremont Barrel Fill site, Clark County, Ohio

The Tremont Barrel Fill site is immediately north of the Tremont City Landfill near Tremont City, Clark County, Ohio. The site was an unlined pit used as a repository for disposing industrial liquid wastes and sludge from 1976 through 1979. Previous investigations led the U.S. Environmental Protection Agency (USEPA) to conclude that the site poses a contamination risk to nearby residents relying on private supply wells opened to the underlying deep sand and gravel and limestone aquifers. The USEPA also concluded there is a potential risk to the residents of the nearby Tremont City; the city obtains its municipal water supply from the Mad River Valley aquifer, which is recharged by the adjacent limestone aquifer. The U.S. Geological Survey (USGS) assessed the degree of hydraulic interconnection, and thus possible contaminant pathway(s), between the two aquifers (the sand and gravel and the limestone) underlying the Barrel Fill site, with consideration for the impact of an identified interconnection between the limestone and the Mad River Valley aquifer used for municipal supply.

Aquifer interconnection between the sand and gravel aquifer overlying the limestone aquifer is assessed by analysis of specific capacity data from well-construction logs for derivation of estimates of transmissivity (T) and horizontal hydraulic conductivity (K_h). Data of this nature is limited in the control or knowledge about how well these data were collected and reported; therefore, the T and K_h are estimations. Similar values of T and K_h are used to infer the degree of aquifer interconnection based on the USEPA Hazard Ranking System, which states that aquifers are considered interconnected when the hydraulic conductivities are within two orders of magnitude.

The results of the hydraulic analysis from 127 wells open to either the sand and gravel or the limestone aquifer indicate that the transmissivity of these aquifers is within one order of magnitude and horizontal hydraulic conductivity is within two orders of magnitude. As such, on the basis of the applied ranking system the two aquifers can be considered hydraulically interconnected.