Lower Granite Dam

(509)
843-1493

   With Construction of Lower Granite Lock and Dam on the Snake River, by the United States Government Corps of Engineers, a 464 mile deep water route from Lewiston and Clarkston to the Pacific Ocean was opened up.  In addition to navigation, the dam provides electric power generation, port facilities, recreation activities, fish and wildlife areas, and jobs for many.

     Lower Granite is the fourth and last dam on the Lower Snake River Project which was authorized by Congress under the River and Harbor Act of 1945.  The first dam started in the project was Ice Harbor Lock and Dam in 1956.  Lower Granite was completed in 1975.  Joining Lower Granite, in addition to Ice Harbor on the Snake River, are Little Goose and Lower Monumental.

     Lower Granite Dam's main structure consists of a powerhouse, spillway, three concrete non-overflow sections, navigation lock, and a rock and gravel embankment with impervious core.  The length of the dam at the crest is  3,200 feet.  There are eight bays with controllable gates in the spillway section.  The navigation lock is 675 feet long and 86 feet wide.  The maximum of the operating lock life is 105 feet.  The rock embankment is 45 feet wide at the top, and slopes one foot on two feet both on the upstream and downstream sides.

     The powerhouse has six generators capable of producing a total of 810,000 kilowatts of electricity.  The power generated is fed into Bonneville Power Administration system and the Northwest Power Grid.

     Lower Granite Dam has extensive fish passage and handling facilities.  These include a fish trapping station where biologist impound adult anadromous fish for inspection, evaluation, and study.  There is also a fingerling handling facility where downstream migrants are trapped, marked, loaded into trucks and hauled downstream to a point below Bonneville Dam on the Columbia River.  Corps' biologists are working to provide replacement habitat for wildlife species adversely affected by the project

     Lower Granite Lock and Dam is named for Granite Point, approximately six miles upstream of the dam.  The point is of geological interest because it is the only granite outcropping in a sea of basalt.  Granite from the point was hauled downstream on old sternwheelers and used in construction of a number of buildings in early Portland.  The old US Custom House, a headquarters for the North Pacific Division, Army Corps of Engineers, was built of stone from Granite Point.

     While Lower Granite was being constructed, the Walla Walla District worked very closely with Washington State University, and other educational institutions on excavations and investigations of archaeological materials.  Artifacts, petroglyphs, and grave sites were carefully excavated and catalogued.  Much important material was salvaged.

     Approximately 275 Indian graves were relocated from the reservoir area at the request of the Nez Perce Tribe.  The Corps, in cooperation with the University of Idaho and the Nez Perce Tribal Committee, removed the ancestral remains for interment in common graves at Nez Perce Historical Park at Spaulding, Idaho.

     A visitors' building, with a fish viewing room and the power house gallery in the dam, is open to the public daily, coincidental with seasonal dam crossing hours.  Guided tours for groups and organizations can also be arranged by calling the dam at (509) 843-1493.