304 Powerplant Road
Dilliner, PA 15327-9603
Point Marion Lock and Dam is one of nine navigation structures which provide for year-round navigation on the Monongahela River between Pittsburgh, Pa., and Fairmont, W.Va. Point Marion maintains a pool for 11.2 miles upstream to Morgantown Lock and Dam.
Point Marion Lock and Dam is located at river mile 90.8 near the community of Point Marion, Pa. The lock chamber and operations buildings are situated along the left descending bank of the river. Road access to the project is from Power Plant Road, leading south from State Route 88 at the Point Marion bridge.
The original Point Marion Lock and Dam, previously known as Lock and Dam 8, was built between 1923 - 1926. In 1959, the dam was changed from a fixed crest to a gated type. The Water Resources Development Act of 1986 authorized replacement of the existing lock chamber with a larger lock chamber (84 feet by 720 feet) on the landward side of the existing chamber. Using an innovative, award-winning design in constructing the chamber, the new lock was dedicated in September 1994.
Point Marion Lock and Dam consists of one lock chamber and a gated dam. This type of dam is constructed to permit increased control over the water level in the navigation pool upstream of the dam. Machinery mounted on tall concrete piers moves large chains which lift gates that are hinged into the body of the piers. As the gates are raised or lowered to control the amount of water flowing under them, the upstream pool is maintained at a relatively constant level for an authorized depth of at least 9 feet throughout its length. The dam, however, cannot be operated to control flood flows. An incidental benefit derived from the pool formed by the dam is the availability of a source of municipal and industrial water supply.