Reservoir EQUALIZING RESERVOIR DAMS and THE FEEDER CANAL Columbia Basin Project Purpose: Serves as a balancing reservoir for water pumped from Lake Roosevelt for use on the project lands Location: In upper Grand Coulee between North Dam near Grand Coulee Dam and Dry Falls Dam near Coulee City, Wash. Constructed: 1946-1951 Water supply: Columbia River water pumped from Lake Roosevelt Area: 27, 800 acres Storage: Total--1, 484, 000 acre-feet Live--696, 000 acre-feet between elevations 1540 and 1570 North Dam Type: Zoned rolled-earth and rockfillembankment Foundation: Granite on south abutment, basalt on north abutment, and reworked shale in channel Slope protection: Riprap on a rockfill Dimensions: Dry blanket on the upstream face, rockfill on the downstream face Height: 90 feet above coulee floor, 145 feet above excavation Crest length: 1,400 feet Crest elevation: 1580.0 Volume: 1, 472, 500 cubic yards Slopes: Zone 1--upstream, 1-1/2 to 1, downstream 1/2 to 1 Rockfill--upstream, 3 to 1 down to elevation 1530 and 10 to 1 below, downstream, 2 to 1 down to elevation 1520 and 6 to 1 below Cutoff trench: 50 feet wide on abutments; in the channel section, 50 feet wide at elevation 1450 with 4 to 1 slopes, and 35 feet wide at eleva tion 1435 with 1-1/2 to 1 slopes; 5-foot concrete cutoff wall on rock abutments Spillway and outlet: None, outlet through Main canal headworks at Dry Falls Dam Dry Falls Dam (Formerly South Coulee Dam) Type: Zoned rolled-earth and rockfill embankment Crest elevation: 1580.0 Volume: 1,657, 800 cubic yards Slopes: Zone 1--3/4 to 1 upstream and downstream Rockfill-upstream, 2-1/4 to 1 down to elevation 1570, 2-1/2 to 1 between elevations 1550 and 1570, and 6 to 1 below 1550 downstream, 1-3/4 to 1 down to elevation 1562, 2 to 1 between elevations 1550 and 1562, and 4 to 1 below 1550 Cutoff trench: 30-foot bottom width with 1-1/2 to 1 side slopes, 5-foot concrete cutoff wall for entire length Main canal headworks: Purpose: Regulates flow into Main canal, serves as the only outlet to the reservoir Type: Rectangular six-cell barrel conduit with a gate chamber near the middle extending to the top of the embankment Gates: One 12- by 18-foot top-seal radial gate per cell Discharge: 13, 200 cubic feet per sec ond at a reservoir level of 1540 with 0.65-foot head loss Sill elevation: 1516.81 Feeder Canal Purpose: Conveys water from the pump discharge outlet of Grand Coulee pumping plant to the Type: Reinforced concrete lined section and twin-barrel conduit Dimensions-- Canal: Length: 6130.3 feet Section: 50-foot base width, 1-1/2 to 1 slopes, 25-foot depth Hydraulics: Q = 16,000 cubic feet per second S = 0.000435 Dimensions--Conduit: Section: Two 25-foot-diameter reinforced concrete barrels Hydraulics: Q = 16,000 cubic feet per second S = 0.00215 Appurtenances: Check structure with three 24- by 25-foot radial gates, a 410-foot-long concrete-lined chute, and a wasteway |