Steve Young, head dam operator at Indian Rock Dam, located about three miles upstream from York, Pennsylvania, Aug. 17, 2020. (U.S. Army photo by Christopher Fincham) Indian Rock Dam is a dry dam, which means it typically doesn't hold any water unless its gates are closed and water accumulates following heavy rains. An earth and rock structure, the dam is 1,000 feet long rising 83 feet above the streambed, with a side-channel spillway and gated outlet conduit in the right abutment. The normally dry reservoir area has a storage capacity of 28,000 acre-feet (9.1 billion gallons) at spillway crest and controls a drainage area of 94 square miles, equivalent to 41 percent of the watershed upstream from York.