EXPLORING SEDIMENT PATHWAYS 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. Lower levels of the cave system contain continually flowing water, while upper levels are only submerged during flood events. Hidden River Cave has a history of contamination due to improper domestic and industrial waste disposal and misunderstanding of local hydrogeology. 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. Remediation efforts began in 1989 with a sewage treatment plant, and sewage systems were diverted from the Hidden River Cave system.

Research is being conducted in Hidden River Cave to determine how water and sediment are being transported through the system and 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. Microfossils, including thecamoebians (testate amoebae), found within the sediment aid in delineation of sediment sources and transport pathways, sedimentation rates, and can be used to assess the past health of the cave. Integrating various sources of sedimentological data enhances the understanding of modern sedimentation processes, the depositional history of sediments within the cave system, and their record of paleoenvironmental change. Understanding these processes within this unique cave system will contribute toward establishing improved water management policies for this and similar cave systems found elsewhere.