Report of the Secretary of the Army
on Civil Works Activities for Fiscal Year 1996
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 681 msl is surmounted by eight radial gates, 50 feet wide and 60 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 674 feet and 15-foot minimum depth over the sills. A navigation channel 250 feet wide, 14 feet deep, and 39.3 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 1996 was 54.79 billion kw hours. Approximately $9,455,000 (adjusted to October 1996 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 fish-trap repair. Contract completed for repair of Lewiston Water Intake. Purchased and installed fishway bulkheads. Operation and Maintenance: During the fiscal year, 3.4 billion kw 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 2,414,283 tons during Calendar Year 1995.

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 1996 transport season was marked by very high river flows compared to drought conditions that have prevailed in the Columbia and Snake Rivers for most years since 1987. Snake River flows in 1996 were approximately 143 percent of the 30-year average. Juvenile fish collection totaled 5,227,672 at Lower Granite, compared to 9,733,482 in 1994 and 6,910,701 in 1993. High spill levels and reduced numbers of juvenile chinook salmon resulted in fewer juvenile fish being collected in 1996. Daily collection peaked at 407,550 on April 27, compared to a peak of 910,051 in 1995. A yearly total of 102,430 fish were bypassed back to the river for research projects and various other reasons. At Little Goose Dam, 1,889,552 juvenile salmon and steelhead were collected compared to the 3,070,040 collected in 1995. Approximately 5,000 fish were bypassed at Little Goose in 1996. Lower Monumental Dam collected 1,334,693 juvenile salmon and steelhead, a decrease from the 2,733,494 collected in 1995. A total of 68,230 juvenile fish were bypassed for various reasons in 1996. At McNary Dam, 4,642,979 juvenile fish were collected in 1996, approximately half the number of fish of the fish collected in 1995. An estimated 1,469,000 fish were bypassed at McNary Dam in 1996 for various research projects. Juvenile fish collected during the spring were bypassed in compliance with National Marine Fisheries Service's biological opinion for endangered species act consultation. A total of 1,644,628 juvenile fish were bypassed in 1996 for this reason and for various research projects. Transportation began in late June when subyearling chinook salmon predominated the collection. A grand total of 13,094,896 fish were collected at all projects in 1996, compared to the record collection of 24,556,390 in 1995. A total of 11,222,622 juvenile fish were transported 85.7 percent of those collected. Of those transported, 1,387,921 (12.4 percent) were by truck and 9,834,701 (87.6 percent) were by barge.