CONNECTING CONTAMINATION EVENTS TO THE SEDIMENT RECORD IN HIDDEN RIVER CAVE, KENTUCKY

Hidden River Cave is a multi-level, active cave system in the town of Horse Cave, Kentucky, located southeast of Mammoth Cave National Park, and is hydrogeologically related to the Mammoth Cave system. The cave system has approximately 25km of mapped passages with expectations of more to be found. Lower levels of the cave system contain continually flowing water, while upper levels are only submerged during extreme flood events. Hidden River Cave has a history of contamination due to improper domestic and industrial waste disposal. In the early 20^th century the cave system was used as a potable water source and for hydroelectric power generation. Due to severe contamination it was closed to the public in 1943 and remained closed for almost 50 years. Serious remediation efforts began in 1989 with a sewage treatment plant and sewage systems being diverted from the Hidden River Cave system.

This paper will explore current research taking place in Hidden River Cave to determine how water and sediment are being transported through the cave system. This further understanding of sediment transport is used to assess the impact of past contaminant input on the cave environment. Concentrations of selected contaminants were determined using water samples, sediment cores, and surface sediment samples collected in the cave. Water samples were tested for one or all of chromium (Cr(VI) and Cr(III)), aluminum, nickel and lead, with pH, water temperature, total dissolved solids and conductivity measured in situ. Sediment cores were analyzed using an Itrax core scanner to obtain elemental concentrations, radiography, and magnetic susceptibility data. Identification of distinct horizons of metal concentrations in sediment cores allows for sedimentation event correlation within the cave system. The chronology of sedimentation events was determined using Pb-210 analysis of core sediment and indicates a strong connection between historical contaminating events in the town of Horse Cave and cave sediment deposition. Sediment core analysis has thus allowed depositional patterns in the cave system to be determined and related to historic surficial processes. These findings can be applied to enhance understanding of the combined effects of landscape evolution and anthropogenic impacts which may be used to inform decision making processes for communities overlying both Hidden River Cave and other karstic cave systems.