Nesbitt Dam: Perched on a Ledge

Abstract Only - (Background) Nesbitt Dam, owned and operated by Pennsylvania American Water, is a high hazard, large size PADEP Class A-1 dam located in Lackawanna County, Pennsylvania. This water supply dam is a 101-foot high, 538-foot long (including the spillway) composite earthfill embankment and stone masonry structure with a masonry core wall. Nesbitt Dam impounds 3,926 acre-feet of water at normal pool level and 5,335 acre-feet at top of dam level. The left side of the dam is perched on a nearly 50-foot high ledge that defines the left abutment. The spillway is 200 feet long and is comprised of stone masonry components. The main portion of the spillway creates a 140-foot long section that overflows directly into the spillway apron prior to entering the stream below. The remaining 60-foot long section of the principal spillway discharges into what functionally serves as a “side channel” that conveys spillway flow approximately parallel to the axis of the dam prior to directing discharges precipitously over the ledge into the spillway apron below.