Model Study of Monongahela Dam #4 Lock Replacements, Monongahela River, Pittsburgh, Pennsylvania

Abstract : Navigation improvements are being investigated for several existing projects on the Monongahela River. A hydraulic model study was conducted to evaluate filling and emptying system design alternatives and flow conditions in the upper and lower approaches for the lock replacements at Locks and Dam #4. A 1:25-scale model was constructed to determine the range of lock performance for both locks. The proposed filling and emptying system for the locks is an In-Chamber Longitudinal Culvert Filling and Emptying System. The filling time for acceptable chamber performance with the 6.035-m (19.8-ft) lift was 8.3 min. This filling time was achieved with a 3.0-min valve. The emptying time for the same lift was 8.75 min, and it was achieved with a valve time between 1.0 and 2.0 min. Experiments were also performed to measure the surge created in the vicinity of the proposed down- stream lock approach during emptying operations. Results showed that the water-surface elevation in the lower approach increased by 0.37 ft and occurred approximately 1.5 to 3.0 min into the emptying cycle.