CORRELATING THE LOCATION OF A CAVE PASSAGE IN GYPSUM KARST TO A HIGHWAY RIGHT-OF-WAY USING A CAVE RADIO

The Oklahoma Department of Transportation plans to widen Highway 412 in western Oklahoma in an area underlain by the Blaine Gypsum Formation. The project would convert the highway from a two-lane divided to a four-lane divided highway and decrease the existing grades. One location of particular concern is in Major County where Nescatunga Cave passes under the highway at a relatively shallow (<30 meters) depth, but the location of the cave passage relative to the highway was not known. The preliminary plans for the highway-widening project specified lowering the grade by removing overburden in the vicinity of Nescatunga Cave. Concern regarding possible roadbed failure caused the Oklahoma Department of Transportation to seek methods to determine the location of Nescatunga Cave relative to the highway expansion project. Volunteers from the National Speleological Society used low-frequency radio direction finding equipment, commonly referred to as a cave radio, and a tape-and-compass survey to depict the position and dimensions of the Nescatunga Cave passages relative to the highway-widening project. A transmitter was placed sequentially at seven stations in the cave passage and a radio direction-finding receiver was used to identify and mark points on the surface directly above the transmitter stations. Transmitter stations, as well as the cave passage position and dimensions were surveyed using a tape and compass. The surface points were repeatable to within five centimeters. Subsequent core drilling by the Oklahoma Department of Transportation at three of the survey sites intercepted the cave passage--which ranged in width from 5.3 to 9.1 meters--at all three locations. Knowledge of the depth and location of the cave passages allowed the Oklahoma Department of Transportation to minimize drilling costs. The Oklahoma Department of Transportation is considering design changes for the highway-widening project to maintain more overburden above the cave passage.