LaGrande Dam

Built in 1945, LaGrande Dam generates enough electricity to power nearly 25,000 homes each year. It is 217 feet high and 710 feet long and includes four 6,000-kilowatt generators and a 40,000-kilowatt generator. Along with Alder Dam, it is one of two Tacoma Power dams on the Nisqually River.

To enhance Chinook and coho salmon spawning habitat, we maintain a continuous flow of water along the 1.7-mile stretch of river between LaGrande Dam and its powerhouse.

The reservoir behind the dam covers 45 acres, but it is not publicly accessible because of the steep, rugged terrain surrounding it. However, Alder Lake Park offers outdoor recreation in the immediate area.

Statistics

  • Year completed – powerhouse, 1912; new dam, 1945
  • River system – Nisqually
  • Original investment – $9.7 million
  • Type of dam – concrete gravity and embankment
  • Height – above riverbed, 192 feet; above bedrock, 217 feet
  • Length – 710 feet
  • Width – top, 12 feet; base, 85 feet
  • Volume of concrete in dam – 85,000 cubic yards
  • Average flow – 1,400 cubic feet/second
  • Drainage area – 292 square miles
  • Reservoir length – 1.5 miles
  • Miles of shoreline – 3.5 miles
  • Reservoir area at maximum elevation – 45 acres
  • Reservoir elevation – full, 935 feet; lowest allowable, 910 feet
  • Average annual generation – 345 million kilowatt-hours
  • Equivalent number of NW homes served – 24,500
  • Number of generators – four 6,000 kilowatt generators; one 40,000 kilowatt generator
  • Installed capacity (nameplate rating) – 64,000 kilowatts
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