Karst groundwater basin delineation, Fort Knox, Kentucky

Abstract

Evaluation of karst groundwater quality concern at Fort Knox Kentucky has required the development of a sitewide karst groundwater flow model and basin delineation investigation. The karst aquifer underlying Fort Knox is developed within approximately 60 m of the St. Louis Limestone and is bounded on three sides by surface streams that represent the local base level. The underlying Salem Limestone acts as a regional aquitard and provides a lower limit to karst aquifer development. The study area covers over 130 km 2 and contains over 200-inventoried karst features. As a part of this investigation, innovative multiple dye trace events were conducted throughout the study area using up to six dyes per event with a total of eight dyes used to conduct 14 dye traces during three seasonal events. Dye trace results, structural and topographic controls, spring characteristics, and normalized base flow were used to establish groundwater basin limits and boundary zones and to develop a conceptual sitewide groundwater flow model. The primary finding of this work indicates sitewide groundwater flow is controlled directly or indirectly by local stratigraphy, geologic structure, and changes in stream levels in the geologic past, and that two groundwater basins dominate the study area, accounting for approximately 80% of measured sitewide groundwater discharge. The findings of this investigation will be used to assess the groundwater contaminant contribution from source areas in individual basins, develop an effective groundwater monitoring program, and guide future groundwater management strategies.