Lower Monumental Dam is located 41.6 miles above the mouth of the Snake River and 35 miles northeast of Pasco, Washington. Maximum heat on the project is 103 ft; the project design discharge is 850,000 cfs. Excavation requirements, diversion plans, structures locations, and methods of operation were studied in a 1:100-scale model that reproduced 2.4 miles of river channel and pertinent overbank topography. The first-step cofferdam and diversion channel were designed to protect the work area against discharges to 250,000 cfs. The diversion channel and cofferdam cells were revised and the location of a temporary fishway was determined by means of the model study. Tests of the second-step cofferdam, designed for 200,000 cfs, indicated that the height of four upstream cells should be increased 3 ft, the three downstream temporary fishway entrance. (Modified author abstract).

Lower Monumental Dam is located 41.6 miles above the mouth of the Snake River and 35 miles northeast of Pasco, Washington. Maximum heat on the project is 103 ft; the project design discharge is 850,000 cfs. Excavation requirements, diversion plans, structures locations, and methods of operation were studied in a 1:100-scale model that reproduced 2.4 miles of river channel and pertinent overbank topography. The first-step cofferdam and diversion channel were designed to protect the work area against discharges to 250,000 cfs. The diversion channel and cofferdam cells were revised and the location of a temporary fishway was determined by means of the model study. Tests of the second-step cofferdam, designed for 200,000 cfs, indicated that the height of four upstream cells should be increased 3 ft, the three downstream temporary fishway entrance. (Modified author abstract).