Anderson Ranch Dam and Powerplant is a multiple purpose structure that provides benefits of irrigation, power, and flood and silt control. The dam is 456 feet high and is on the South Fork of the Boise River, 28 miles northeast of Mountain Home. It has a total storage capacity of474,900 acre-feet (active413,100 acre-feet) and was the world's highest earthfill dam at the time of its completion in 1950. The power plant had a rated capacity of 27,000 kilowatts with two units installed. These units were up-rated in 1986, increasing the capacity to 20,000 kilowatts each for a total of 40,000 kilowatts.
Geology
Anderson Ranch Dam is located near the southwestern edge of Idaho Batholith which is composed of a series of closely related, coarse-grained intrusions. Major normal faulting in the region includes faults in and adjacent to the Batholith, faults bounding the northeast and southwest margin on the adjacent Snake River Plain, and faults forming Camas Prairie Basin east of the dam. These faults show a low to moderate seismic activity level. The dam is located in a narrow steep-sided valley cut through several hundred of igneous extrusive and extrusive rock. In the dam foundation, the rock was found to be intensely fractured and cut by numerous shears and fractures of varying widths. Several dikes were also found normal to the canyon axis. The dikes present a reduction of fractures and shears reducing the foundation permeability and making a tight foundation. Materials within the canyon include talus, colluvium, alluvium, residual soil and intact rock. These materials form the foundation of the dam and have performed well with respect to deformation and seepage.
General
Project
Boise
Dam Type
Zoned Earthfill
Longitude
-115.4501724
Latitude
43.3595096
Reservoir
Anderson Ranch
Original Construction
1941-1950
National ID Number
ID00279
Location
28 miles northeast of Mountain Home, Idaho
Watercourse
South Fork of the Boise River
Dimensions
Crest Elevation
4206.0 ft
Structural Height
456.0 ft
Hydraulic Height (Normal Operating Depth at Dam)
330.0 ft
Top of Joint Use Pool (Elevation)
4196.0 ft
Top of Active Conservation Pool (Elevation)
4196.0 ft
Top of Inactive Conservation Pool (Elevation)
4039.6 ft
Top of Dead Storage Pool (Elevation)
3992.0 ft
Streambed at Dam Axis
3866.0 ft
Spillway Crest Elevation
4174.0 ft
Crest Length
1350.0 ft
Hydraulics & Hydrology
Normal Water Surface Elevation
4196.0 ft
Spillway Capacity at Elevation
20,000 cfs at 4198 ft
Auxiliary Spillway
No
Outlet Works Capacity at Elevation
10,000 cfs at 4198.0 ft
Drainage Area
960 sq mi
Hydrometeorological Report (HMR)
HMR 57
Total Water Storage at Elevation
474,900 ac-ft at 4196 ft
Spillway Type
Concrete-lined chute located on left abutment, controlled by two 25-by-22 foot radial gates
Net Generation
151,014,000 kWh in 2011
Contact
Owner
Title: Area Office Manager Organization: Snake River Area Office Address: 230 Collins Road City: Boise, ID 83702-4520 Fax: 208-383-2275 Phone: 208-383-2248
Operator
Title: Area Office Manager Organization: Snake River Area Office Address: 230 Collins Road City: Boise, ID 83702-4520 Fax: 208-383-2275 Phone: 208-383-2248
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