The hydrogeologic conditions around the Bardstown Sewage Treatment Plant were studied from August 1996 through December 1997. Hydraulic and geochemical data were collected from eight monitoring wells and four surface-water monitoring sites on the plant property.
There is a large hydraulic gradient between the lagoons at the plant and the surrounding stream, Town Creek. Initial water-level measurements in wells surrounding the site suggest no major leakage from the lagoons, however. Neither flowing artesian conditions nor unusually high water levels were observed in any of the wells. Water-level measurements collected by data loggers showed that shallow wells responded quickly to recharge, whereas bedrock wells were relatively unresponsive throughout most of the observation period. Slug tests indicate that the hydraulic conductivities of the unconsolidated material monitored by the shallow wells are several orders of magnitude greater than for the underlying bedrock.
Surface-water flow measurements indicate that Town Creek is a losing stream adjacent to the lagoons. This conclusion is supported by hydraulic data from the monitoring wells. These data suggest that it is unlikely the lagoons are leaking significantly into Town Creek. Town Creek appears to become a gaining stream along its lowest reaches on the northwestern side of the plant property.
Interpretation of chloride, bromide, fluoride, and major-ion chemistry data indicates that the water chemistry in the shallow wells is not affected significantly by the lagoons. Well-water chemistry is influenced by Town Creek, which recharges the shallow alluvial sediments during high flow. All metal concentrations appear to be below primary and secondary maximum contaminant levels (MCL's) in both the lagoons and the stream water. The only metals for which the MCL was exceeded at the site are iron and manganese; concentrations were relatively high in the shallow ground-water monitoring wells. Concentrations of these metals are commonly elevated in ground water derived from shallow, alluvial sediments in this physiographic region, however. These data suggest that the lagoons are having a minimal impact, if any, on the quality of ground water around the lagoons.
The results from a one-time sampling for bacteria indicate that the total coliform in the monitoring wells ranged from 10 to 1,920 colonies per 100 ml (col/100 ml). Analysis for E. coli bacteria showed that only one well, BT30, contained measurable counts (10 col/100 ml). The presence of E. coli in this well is inconsistent with other parameters that would indicate contamination from the lagoons, however; their presence may represent contamination during sampling.
The data from this investigation, as well as previous studies, indicate that the lagoons provide efficient primary water treatment without causing significant ground-water contamination. Moreover, the design and engineering used for the Bardstown plant may provide a model for cost-effective, efficient primary water-treatment systems capable of long-term operation without affecting the local ground-water system. Lagoons in other physiographic and geologic settings should be studied to determine the effect of large lagoons throughout the state. This is especially pertinent now, because public and regulatory agencies have expressed great interest in lagoon technology for managing wastes from large-scale livestock operations.
Report of Investigations 7
Digital Object Identifier (DOI)
Wunsch, David R.; Secrist, Gregory L.; and Sendlein, Lyle V.A., "Hydrogeologic Conditions Around Deep Aeration Lagoons at the Bardstown Wastewater Treatment Plant" (2001). Kentucky Geological Survey Report of Investigations. 10.