Annual Report of the Chief of Engineers
on Civil Works Activities
Fiscal Year 1989
Department of the Army Corps of Engineers
Extract Report of Walla Walla District

Lower Granite Lock and Dam, Washington

Location. At River Mile 107.5 on Snake River at head of Lake Bryan (Little Goose Reservoir) and about 33 miles downstream from Lewiston, Idaho.

Existing project. The project includes a dam, powerplant, navigation lock, fish ladder, appurtenant facilities, and required about 8 miles of backwater levees along the Snake and Clearwater Rivers at Lewiston, Idaho. Project provides for slackwater navigation, hydroelectric power generation, recreation, and incidental irrigation. The reservoir has a normal operating range between Elevations 738 and 733 Mean Sea Level (MSL) in Lewiston, Idaho-Clarkston, Washington, area. Lower Granite pool extends upstream about 38 miles, and provides slackwater to the confluence of the Snake and Clearwater Rivers. Dam structure is about 3,200 feet long and about 146 feet high above streambed. Fish passage facilities include one ladder with entrances on both shores, with a fish channel through the spillway that connects to the powerhouse fish collection system and south shore ladder. Powerhouse has six 135,000 kilowatt generating units in operation, for a capacity of 810,000 kilowatts. Spillway dam is 512 feet long and overflow crest at Elevation 581 MSL is surmounted by 8 radial gates, 60 feet wide and 60.5 feet high, which provides the capacity to pass a design flood of 850,000 cubic feet per second. Navigation lock is single-lift type with clear plan dimensions of 86 by 675 feet and 15-foot minimum depth over the sills. A navigation channel 250 feet wide and 14 feet deep is provided form the dam to the confluence of the Snake and Clearwater Rivers. Principal data are set forth in table 39-J.

Construction of the original project started in July 1965 and was completed in 1984. Construction of the additional generating units was started in 1974 and completed in 1979. Power generation through September 1989 has been 40.60 billion kilowatt hours. Approximately $4,119,300 in potential flood damages have been prevented since the levees became functional.

Local cooperation. None required.

Operations during fiscal year. Maintenance: Contracts continue for powerplant control. Operation and Maintenance: During fiscal year, 25.4 billion kilowatt hours of electrical power were generated by the six generating units. Traffic through the navigation lock, consisting of grains, petroleum products, fertilizer, wood products, and miscellaneous cargo, amounted to 2,576,567 tons during calendar year 1988.

As the first collection point on the Snake River, Lower Granite Dam is a primary component of the District's Juvenile Fish Transport Program. Transport began in the 1960's as a study of methods of bypassing juvenile steelhead and salmon around turbines o the Corps' Snake and Columbia River dams. Transport became a routine operation in 1980, while other structural modifications, installation of screens, and development of bypass systems continue.

For the transport program, the District has collection facilities at Lower Granite, Little Goose, and McNary Dams. Juvenile salmon and steelhead collected at these dams are hauled by specially designed trucks or barges to release sites below Bonneville Dam. From there, they can travel unobstructed to the sea. In 1989, over 20,000,000 juvenile fish were collected. Due to fishery agency and Indian tribal policy, over 4.5 million, primarily yearling chinook, were bypassed back tot he river after being collected. Another million were bypassed at Lower Granite Dam because there was inadequate barge capacity to haul them. In all, over 15 million fish were transported. Increased hatchery production and improved collection facilities, especially at Little Goose Dam, should result in record numbers of fish being collected and transported in 1990.