Report of the Secretary of the Army
on Civil Works Activities for Fiscal Year 1994
Department of the Army Corps of Engineers
Extract Report of the Walla Walla District

Lower Granite Lock and Dam, Washington

Existing project. The project includes a dam, powerplant, navigation lock, fish ladder, appurtenant facilities, and required about 8 miles of slackwater levees along the Snake and Clearwater Rivers at Lewiston, Idaho. The project provides for slackwater navigation, hydroelectric power generation, recreation, and incidental irrigation. The reservoir has a normal operating range between elevations 738 and 733 msl in Lewiston, Idaho, and Clarkston, Washington. Lower Granite pool extends upstream about 38 miles and provides slackwater to the confluence of the Snake and Clearwater Rivers. The dam structure is about 3,200 feet long and about 146 feet above the streambed. Fish passage facilities include one ladder with entrances on both shores with a fish channel through the spillway, which connects to the powerhouse fish collection system and south shore ladder. The powerhouse has six 135,000 kw generating units in operation for a capacity of 810,000 kw. Spillway dam is 512 feet long and the overflow crest at elevation 581 msl is surmounted by eight radial gates, 60 feet wide and 60.5 feet high, which provide the capacity to pass a design flood of 850,000 cfs. 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, 14 feet deep, and 38.0 miles long is provided from 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, was placed in operation in 1975, and was completed in 1984. Construction of additional generating units was started in 1974 and completed in 1979. Power generation through September 1994 was 48.49 billion kw hours. Approximately $4,347,000 (adjusted to October 1994 price index) in potential flood damage has been prevented since the levees became functional.

Local cooperation. None required.

Operations during fiscal year. Maintenance: Contract completed for fishway controls. Contract completed for navigation lock guidewall timber replacement. Contract awarded for powerhouse roof repair. Operation and Maintenance: During fiscal year, 1.75 billion kilowatt hours of electrical power were generated by the six generating units. Traffic through the navigation lock consisted of grains, petroleum products, fertilizer, wood products, and miscellaneous cargo; and amounted to 2,200,488 tons during Calendar Year 1993.

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

The 1994 trasnport season was marked by the continuation of drought conditions that have prevailed in the Columbia and Snake Rivers for most years since 1987. Collection totaled 6,910,701 at Lower Granite compared with 8,025,621 in 1993 and 6,911,174 in 1992. Daily collection in 1994 peaked at 507,700 on May 10, down from the daily collection record of 893,100 juveniles set in 1993. High fish numbers for several days in a row resulted in over 53,000 fish being released back to the river on May 10 due to exceeding barge and raceway carrying capacity. At Little Goose Dam, 1,513,538 juvenile salmon and steelhead were collected, a decrease from the 2,012,599 collected in 1992. Approximately 50,000 fish were bypassed at Little Goose in 1994 as a result of lack of barging space or for various research projects. Lower Monumental Dam collected 1,632,458 juvenile salmon and steelhead, up from the 1,337,339 collected in 1993. A total of 195,673 were bypassed for the same reasons as at Little Goose Dam. 1994 was the first year of operation for the new collection and transportation facilities at McNary Dam. A total of 8,759,448 fish were collected, an increase from the 6,659,623 collected in 1993. Peak collection was 189,150 on May 7 when yearling fish dominated collection, and 510,800 on July 9 when subyearling fish comprised 99.3 percent of the collection. A total of 956,830 salmon and steelhead were bypassed at McNary Dam due to lack of barge space and for research purposes. A fish loss at McNary Dam due to warm water temperatures on July 16 resulted in the plugging of the facility dewatering structure and loss of water to the juvenile fish holding facilities. Approximately 57,000 fish died and 567,486 juvenile fish were released back to the river before the facilities ran out of water. These fish are not included in the above seasonal collection numbers. River flows in the Snake and Columbia Rivers were below the trigger levels for bypassing fish back to the river for increasing inriver migrations. At the request of National Marine Fisheries Service, a spill program was implemented from late May through mid June to improve inriver migration of juvenile salmonids. A grand total of 18,816,145 fish were collected in 1994, well below the record of 22,261,661 fish collected in 1990. A total of 17,370,462 fish were transported, 92.3 percent of those collected. Of those transported, 473,518 (2.7 percent) were by truck and 16,896,944 (97.3 percent) were by barge.