The Columbia Basin Project (CBP) is the largest Bureau of Reclamation project in Washington. At 670,000 acres under irrigation today, the CBP, while huge is still unfinished as it is planned to irrigate over 1,095,000 in the project area (U. S. Department of the Interior, Bureau of Reclamation, 2004, p. 44 and Warne, 1973, p.127). The project area is in Adams, Douglas, Franklin, Lincoln and Grant Counties and turned dry-farmed lands and sagebrush into one of the most productive agricultural areas in Washington. This project was also to spur settlement of new farms for veterans returning from World War II.
After World War II the boom experienced in the development of the CBP was highest from 1952-1959 with about 50,000 acres of land a year coming into irrigation, which was the largest growth to date in the planned 1 million acres (Warne, 1973, p. 138). Water is pumped up from behind Grand Coulee Dam and impounded in Banks Lake behind Dry Falls Dam then makes its way down through the system in a series of six main canals and three reservoirs to reach all of the irrigatible acreage in the Columbia Basin. This system alone consists of over 300 miles of main canals, approximately 2,000 miles of laterals, and 3,500 miles of drains and wasteways. The period of significance of the CBP is from 1946-1959 as those were the major construction years for the project. For more information see http://www.usbr.gov/projects and the Columbia Basin Project History.
South Coulee Dam When built, this structure was designated as the South Coulee Dam, but by 1954 it was called Dry Falls Dam (U.S. Department of the Interior, Bureau of Reclamation, 1954, p. 11). No information has been found as to why it was renamed. For this report South Coulee Dam will be referred to its current name of Dry Falls Dam. This 9800 ft. long rock-faced earthfill dam was constructed from 1946-1949 to impound water for the main balancing reservoir (Banks Lake) and to regulate flow into the Main Canal for the Columbia Basin Project. Roy L. Blair and Company and James Crick and Sons both of Spokane had the lowest bid of the six received at $2,771,887 and this contracting team was chosen on June 18, 1946 to construct a dam across the south end of the Grand Coulee.
Contract No. 12r-16203 also called for the construction of “the Main Canal approach channel, headworks structure on the dam, control gates and transition, and the Main canal from Station 2+29 to 24+00” (U.S. Department of the Interior, Bureau of Reclamation 1954, p. 137). Starting in the early fall of 1946 rock excavations cleared the site down to bedrock and built a 30 foot wide cutoff trench in bedrock along the entire length of the dam. During this period there were three blasting fatalities (U.S. Department of the Interior, Bureau of Reclamation 1954, pp. 123 & 140). A 5 to 10 foot high continuous concrete cutoff wall was built, to prevent seepage of water under the dam, into the center line of the cutoff trench three feet or more down into the bedrock (U.S. Department of the Interior, Bureau of Reclamation 1954, p. 144).
Dry Falls Dam was designed as a zoned earth embankment structure with a narrow impervious central core, a semi-pervious layer on either side of the core, and a layer of rockfill over the semi-pervious layer. Horizontal layers were broken out into three zones. Zone 1 and 2 were built with sheepsfoot rolled earth fill 699,657 total cubic yards of earthen material and Zone 3, the rockfill layer had 930,742 cubic yards of rock (U.S. Department of the Interior, Bureau of Reclamation 1954, pp. 151 & 153). This material was taken from a quarries east and west of Coulee City plus the excavation area for the dam (U.S. Department of the Interior, Bureau of Reclamation, 1948, p. 179).
The Main canal headworks was started in March 1948 and completed by June 1949. The headworks also serves as the reservoir outlet as there is no spillway. A total of 7,979.4 cubic yards of concrete were used in the headworks structure. This was nearly half of the 15,639.7 cubic yards of concrete were used in the whole dam. Six 12- by 18-foot radial gates with screw lift vertical gate hoists were installed in the headworks to control the discharge into the canal. The motors for each gate were driven by a totally enclosed 5-horsepower, 60-cycle, 2-speed, 3-phase induction motor and there were three hoist motor controls installed for operation of the six motors (U.S. Department of the Interior, Bureau of Reclamation 1954, pp. 161-162 & 164).
Washington State Highway No. 10A from Everett to Spokane was relocated during dam construction into the reservoir area. This highway later became United States (Washington State) Highway No. 2 that stretched from Houlton, Maine to Everett, Washington (U. S. Department of Transportation, Federal Highway Administration, 2009, p. 1). Upon completion of Dry Falls Dam in September 9, 1949 the highway was moved to the crest of the dam. The wooden guardrails on the crest for the highway were in the original plan, but concrete and steel-beam guardrails were installed per extra work order No. 2 in 1948 (U.S. Department of the Interior, Bureau of Reclamation, 1946, p. 205 & U.S. Department of the Interior, Bureau of Reclamation, 1948, p. 188). The highway on the crest was paved in 1950 (U.S. Department of the Interior, Bureau of Reclamation, 1949, p. 268).
The CBP is the largest Reclamation project in Washington and Dry Falls Dam is the headworks for the CBP. The massive scale of the main CBP irrigation features are distinctive characteristics of the project and therefore Dry Falls Dam is eligible under Criterion C as a significant form of 1940s CBP construction. Dry Falls Dam is clearly associated with the irrigation of the Columbia Basin. For without Dry Falls Dam the project could not function, it’s a vital part for the whole system. Therefore Dry Falls Dam also qualifies under Criterion A for the National Register for its association to the CBP.
Dry Falls Dam is situated in the Grand Coulee 30 miles south of Grand Coulee Dam (U. S. Department of the Interior, Bureau of Reclamation, 1954, p. 21). It is 9,880 feet long with a maximum height being 63 feet above the floor of the Grand Coulee to the crest of the dam. The dam is a three zone earthfill construction with basalt riprap on top. The headworks structure, approach transition, outlet transition are all made of reinforced concrete. Inside of the headworks structure there are six 12' x 18' radial gates that control discharge into the main canal. These gates are controlled by screw-lift radial gates hoists. A 27 mile long reservoir is behind Dry Falls Dam (Banks Lake) that holds 715,000 acre-feet of water (U.S. Department of the Interior, Bureau of Reclamation, 2010, p. 1). Washington State highway No. 2 crosses over the dam crest. Today Dry Falls Dam retains a majority of its original construction when built. Riprap has added to or repaired on the dam over the last 61 years when needed along with two jettisons added in 1986 near the headworks. Changes that have occurred over the last 50 years to the crest are Washington State Department of Transportation repaving the highway and replaced the guardrails with wood/steel ones as the originals were concrete/steel guardrails. The only major modifications to the dam are on the headworks. By 1964 the hoist gate motors were covered in individual metal housings (U.S. Department of the Interior, Bureau of Reclamation, 1965, p. 7). In 1986 the electrical controls were redone and a control center was installed in the center of the headworks where an existing hoist motor control had been.
U. S. Department of the Interior, Bureau of Reclamation. (1946) Columbia Basin Project History Calendar Year 1946, Volume 1. U. S. Department of the Interior, Bureau of Reclamation. (1948) Columbia Basin Project History Calendar Year 1948, Volume 1. U. S. Department of the Interior, Bureau of Reclamation. (1949) Columbia Basin Project History Calendar Year 1949, Volume 1. U. S. Department of the Interior, Bureau of Reclamation. (1954) Equalizing Reservoir Dams and the Feeder Canal Technical Record of Design and Construction. Denver, CO: Reclamation Printing Office. U. S. Department of the Interior, Bureau of Reclamation. (1965) Condition of Major Irrigation Structures and Facilities Region 1. Boise, ID: Reclamation Printing Office. U.S. Department of the Interior, Bureau of Reclamation. (2004) Oral History of William Gray, Bureau of Reclamation Oral History Program, By Brit Storey, April 5-6, 2004. U. S. Department of Transportation, Federal Highway Administration. (2009) U. S. 2: Houlton, Maine, to Everett, Washington. Retrieved from http://www.fhwa.dot.gov/infrastructure on May 11, 2010. U. S. Department of the Interior, Bureau of Reclamation. (2010) Dry Falls Dam. Retrieved May 11, 2010, from http://www.usbr.gov/projects Warne, W. E. (1973) The Bureau of Reclamation New York: Prager.
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