Gavins Point Dam - Omaha District US Army Corps of Engineers

OMAHA DISTRICT

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Statistics: (Cubic Feet per Second = CFS; Mean Sea Level = MSL; Kilowatts = Kw; Revolutions per Minute = RPM)

Significant Dates:

  • Operating Since: 1940
  • Construction Start: 1933
  • Closure: June 24, 1937
  • Reservoir filling initiated: November 1937
  • Reservoir first reached minimum operating pool: May 27, 1942
  • Initial Power Generation – First and Last Units: June 1943 – June 1961

Powerplant

  • Number of turbines: 5 Francis,
    • Powerhouse #1-2: 128.5 rpm, 1-164 rpm
    • Powerhouse#2-2: 128.6 rpm
  • Max power generation capability: 185,250 Kw

Size

  • Ranking: Largest hydraulically filled dam in the United States, 5th largest reservoir in the United States
  • Length of Dam: 21,026 feet (excluding spillway)
  • Damming Height: 220 feet (low water to maximum operating pool)
  • Maximum Height: 250.5 feet
  • Maximum width at base: 4,900 feet (total)
  • Maximum width at base: 2,700 feet (without berms)
  • Elevation at crest: 2,280.5 feet msl

Construction

  • Abutment formations (under dam & embankment): Bearpaw shale & glacial fill
  • Type of Fill: Hydraulic & rolled-earth fill
  • Amount of Fill: 125,628,000 cubic yards of fill
  • Amount of Concrete: 1,200,000 cubic yards

Spillway

  • Location: Right bank - remote
  • Width: 820 feet gated
  • Number of gates: 16
  • Dimension of gates: 40-foot x 25-foot vertical lift gates
  • Design discharge capacity: 275,000 cfs at 2,253.5 msl pool elevation
  • Discharge capacity at maximum operating pool: 230,000 cfs at 2,250 msl
  • Top of Spillway Gates (closed): 2,250 feet msl

Intake structures

  • Number: 4
  • Size:  24-foot 8-inch diameter
  • Length:
    • Tunnel #1: 5,636.7 feet long
    • Tunnel #2: 6,309.5 feet long
    • Tunnel #3: 6,614.78 feet long
    • Tunnel #4: 7,239.66 feet long

Outlet works

  • Number: 4 = 2 lead to powerhouses and 2 are for bypass
  • Size: 24-foot 8-inch diameter
  • Length: see above tunnel information
  • Release capacity: 25,000 CFS/conduit, Combined powerhouses release capacity 15,000 CFS, Total for bypass tunnels and powerhouses is 65,000 CFS

Lake/Reservoir

  • Upstream Drainage: 57,500 square miles
  • Tributaries: Missouri River, Musselshell River, Fourchette Creek, Dry Creek
  • Shoreline length: 1,520 miles at 2,234 feet msl
  • Length of full reservoir: 134 miles
  • Surface acres: 245,000 acres
  • Storage capacity: 18,463,000 acre-feet
  • Maximum depth: 220 feet
  • Annual Flood Ctrl & Multi-Use Zone (Elevation): 2,234 feet msl – 2,246 feet msl
  • Exclusive Flood Ctrl Zone (Elevation): 2,246 feet msl – 2,250 feet msl
  • Record Pool Elevation (Date): 2,251.6 feet msl (1975); 2,252.3 feet msl (June 15, 2011)
  • Record Flow Prior to 2011 (Year): 35,000 cfs (1975)
  • Record Flow (2011): 65,900 cfs (Mid June)