Failure of a Small Gravity Dam and the Repair

Late in the summer of 1980, the dam for Snowbird Lake in Forestport, New York, U.S.A., experienced a serious foundation leak made evident by a suddenly erupting geyser near the downstream toe. Subsequent investigation indicated that a severe piping condition had occurred in the soil foundation. Some degree of erosion had effected the foundation earth for more than half of the dam length. Repairs were performed after dewatering the dam work area. The original dam was retained but provided with a new concrete foundation which included a constructed underdrain. A clay blanket was installed on the dam\u27s upstream side to retard future underdam seepage. An emergency spillway circumventing the dam area was established to protect the dam abutments from being topped should the lake reach flood levels