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In page Mammoth Cave National Park:

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At the same time, discoveries made outside the park by an independent group called the Central Kentucky Karst Coalition or CKKC resulted in the survey of tens of miles in Roppel Cave east of the park. Discovered in 1976, Roppel Cave was briefly on the list of the nation's longest caves before it was connected to the Proctor/Morrison's section of the Mammoth Cave System on September 10, 1983. The connection was made by two mixed parties of CRF and CKKC explorers. Each party entered through a separate entrance and met in the middle before continuing in the same direction to exit at the opposite entrance. The resulting total surveyed length was near 300 miles (480 km).[citation needed]