DECIPHERING THE KARST HYDROGEOLOGY OF CASTLEWOOD, VA: A WORK IN PROGRESS

In the Fall of 2022, earth and environmental science students from the University of Virginia’s College at Wise conducted field and remote sensing reconnaissance in the Castlewood area of western Russell County, Virginia. Castlewood is an unincorporated community with a densely-packed population of approximately 1300, including small businesses and a high school located on top of a mature karst sinkhole plain. Most of the homes and businesses are served by conventional or pre-regulation-era septic systems, and all stormwater drainage from roofs, parking lots, roads, quarries, and pastures disappears into the subsurface via sinkholes and swallets. The study area encompasses approximately 74 square kilometers and is underlain by Cambrian-aged limestone, dolomite, and shale. The structural geology is complicated by two northeastward-trending thrust faults and a prominent northwestward-trending joint set identified through fracture trace analyses. Several caves, swallets, and springs are targeted for additional monitoring for fecal indicator bacteria and background fluorescence in the coming months. The motivation for the study is to develop a dye tracer test proposal for consideration by the two counties most impacted by potential nonpoint sources (NPS) of pollution in the Clinch River. Known as “Virginia’s Hidden River”, the Clinch is one of the most biodiverse tributaries to the Upper Tennessee River, the water supply for tens of thousands of downstream residents, and namesake of the new Clinch River State Park. Delineating subsurface flow paths and travel times will benefit stormwater management and emergency/spill response practices, improve source water protection and water supply protection, and serve as a blueprint for enhancing water quality for native aquatic species and recreational watersports alike.