GEOLOGIC STRUCTURAL ANALYSIS AND DYE TRACE EXPERIMENT OF THE ROCK HOUSE SPRINGSHED IN JOHNSON CITY, TENNESSEE

Much of East Tennessee is underlain by Ordovician Knox Group carbonates. In the vicinity of Johnson City, TN these carbonates have been overthrust by the Buffalo Mountain block creating folds, joints, and fractures making this area highly susceptible to the formation of sinkholes, springs, and caves. These karst features create pathways for groundwater flow and have established hydrologic connections between surface streams and groundwater supplies. The city of Elizabethton obtained its public water supply from Rock House Cave until the late 1960s. This research describes results of a study of the Rock House Springshed, which includes Rock House Cave, Carter Saltpeter Cave, and Cave Springs Cave. Structural mapping indicates that major cave passage orientation has developed along joint strike and secondary passages have formed along bedding plane strike. Three concurrent dye trace experiments were used to examine surface water-groundwater connectivity. Dye recovery results indicate multiple flows paths into and through the Rock House Springshed. Rhodamine WT injected in the forward section of Carter Saltpeter Cave traveled west to the Cave Springs Cave ISCO sampler within 1 hour of injection and flowed into Buffalo Creek. Eosin injected into Dry Creek first appeared in Rock House Cave 25 hours after injection and flowed through the forward section of Carter Saltpeter Cave before emerging from Cave Springs Cave 36 hours after injection. Fluoroscein was injected into Anderson Creek and first appeared in the Carter Saltpeter Cave ISCO 53 hours after injection, peaked in Carter Saltpeter after 135 hours, but was not detected in the other caves. The results from this experiment illustrate that these caves are interconnected by multiple and complex flow paths and connections with surface streams increases susceptibility for groundwater contamination. An understanding of flow paths would aid in mitigation and remediation in the event of point or non-point source pollution.