railroad by electric locomotives equipped for both battery and third-rail operation. The railroad was carried along the Nevada side of the canyon, at elevation 720, and was extended along the abutment of the dam by a steel bent trestle which reached as far as the downstream toe of the dam. Concrete from the mixers was emptied directly into 8cubic yard buckets, loaded on specially built flat-cars provided with four openings for the buckets. Each car carried two loaded buckets from the mixing plant to the point of delivery where two empty buckets were received and the two loaded buckets removed. After the concrete in the dam had reached such a height that the use of the trestle at elevation 720 became impracticable, a large stiff-leg derrick was provided to remove the buckets from the railroad at the upstream face of the dam and transfer the buckets for delivery to the point of placement. When storage was commenced in the reservoir, the lowlevel mixing plant and railroad were abandoned and the high-level plant was used. A railroad along the rim of the canyon between the mixing plant and the Nevada spillway was provided for the transportation of concrete from the high-level mixing plant. The operation of the railroad was similar in detail to the low-level method of procedure. Considerable use of trucks was also made to haul concrete from the plant to the various parts of the job. A system of five cableways, spanning the canyon, was provided by the contractor to handle concrete and other materials. All five cableways were designed for normal operation with 20-ton loads and infrequent loadings up to a maximum of 40 tons. The two longest units required a span of 2,575 feet to cover the two spillways. These cableways were identical units with head and tail towers traveling on parallel tracks 800 feet long, the towers being 90 feet high to provide clearance over the intake towers. Two cableways, operating on concentric radial tracks, were provided for the downstream portion of the dam and central portion of the powerhouse. The span for these cableways was 1,405 feet. Each head tower was 75 feet in height, and each tail tower 42 feet in height. A radialtraveling type cableway, with the head tower fixed and the tail tower movable throughout a spanning radius of 1,374 feet and an arc of approximately 600 feet was provided to cover most of the powerhouse area. COSTS Payments were made to Six Companies, Inc., the principal labor contractor, under the schedule of the original specifications, 18 orders for changes and 39 extra work orders. The separate items for payment numbered nearly 600, of which a few are given in the following tabulation: Boulder Dam Today. (Two articles.) Engineering NewsRecord, Feb. 6, 1930. Construction of the Boulder Dam. Compressed Air Mag- Boulder Dam Cement Specifications Tentatively Formu- Mass Concrete Research for Boulder Dam. Journal, Boulder Dam Research. (Five articles.) Journal, American Concrete Institute, September-October 1933. Second Stage at Boulder Dam. (Special issue.) Engineering News-Record, Dec. 21, 1933. Boulder Dam Cement and Concrete Studies. Engineering News-Record, Nov. 22, 1934. Cableway Places Concrete in Boulder Dam. Construction Methods, February and March 1934. Construction Features at Boulder Dam. (Series of articles.) Mechanical Engineering, July 1934 through December 1934. Cooling Boulder Dam Concrete. Engineering NewsRecord, Oct. 11, 1934. Mass Concrete Tests in Large Cylinders. Journal, American Concrete Institute, January-February 1935. Geology of Boulder and Norris Dam Sites. Civil Engineering, January 1935. An Investigation of the Permeability of Mass Concrete With Particular Reference to Boulder Dam. Journal, American Concrete Institute, March-April 1935. Boulder Dam. Industrial and Engineering Chemistry, March 1935. Extensive Rock Grouting at Boulder Dam. Engineering News-Record, June 6, 1935. Boulder Dam: Past Construction and Work Yet to Be Done. Engineering News-Record, Dec. 26, 1935. GRAND COULEE DAM COLUMBIA BASIN PROJECT, WASHINGTON BY C. H. CARTER, ASSOCIATE ENGINEER, BUREAU OF RECLAMATION THE COLUMBIA BASIN PROJECT, embracing a large area in eastern Washington, has progressed through successive stages of investigation to the construction of the first and principal feature, Grand Coulee Dam. Situated on the Columbia River about 90 miles west of Spokane, the construction site has been the scene of intense activity since excavation work began in December 1933. The project, as planned, ultimately will irrigate about 1,200,000 acres in the Big Bend of the Columbia River, extending as far south as its confluence with the Snake. River. Various proposals of development have been combined into a comprehensive plan which will provide the essential construction features for ultimate development. The ultimate project combines irrigation with power development by constructing a high dam across the Columbia River, creating a reservoir from which the irrigation supply will be pumped into the Grand Coulee regulating reservoir and conveyed by gravity canals to the project lands. The power plant, with an installation of 18 main generating units having a total capacity of 1,890,000 kilowatts, will produce 8,100,000,000 kilowatt-hours annually of firm continuous electrical energy, in addition to a considerable amount of secondary energy, part of which will be used to meet pumping requirements. Conserving the river flow and applying it to dry lands which at present cannot be cultivated profitably, will produce crops and create homes for tens of thousands of families. RESERVOIR The headwaters of the Columbia River originate in Columbia Lake of the Canadian Rockies and are augmented by the principal supply from the western slope of the Rocky Mountains and from the Selkirk and Bitterroot Mountains. The drainage area of 74,000 square miles is roughly triangular in shape and includes heavily timbered, mountainous regions in parts of British Columbia, Idaho, Montana, and Washington. Deep snow at high altitudes and numerous large natural lakes near the headwaters serve to regulate the stream flow by retarding flood peaks and supplying the heavy run-off for maximum irrigation requirements during the summer months. As a potential source of power development the Columbia ranks first among our rivers. It produces the second largest run-off in the United States. The river has a total drop of 1,300 feet between the International Boundary and the Pacific Ocean. The territory surrounding the dam site is generally rugged in topography, increasing in roughness to precipitous slopes and ledges adjacent to the river channel. The unusual difference in elevation between the stream bed and lands which are susceptible of irrigation, constitutes the principal problem in the diversion of water. The river discharge during the period of record at Grand Coulee, from 1913 to 1935, varied from 17,000 to 492,000 second-feet, amounting to an average annual run-off of 80,000,000 acre-feet. The reservoir impounded by the dam will have a maximum capacity of 9,645,000 acre-feet and will extend 150 miles upstream to the International Boundary. The lake will have a surface area of 82,000 acres when filled and will supply 5,200,000 acre-feet of storage by being drawn down a maximum of 80 feet during seasons of low run-off. The annual diversion requirements for the project are estimated at 5,300,000 acre-feet, or approximately one-tenth the minimum annual run-off of 53,200,000 acre-feet. GEOLOGY Bedrock at the dam site is generally uniform in elevation, and bears only slight evidence of deterioration from weather-ing, except isolated areas where the condition of the rock necessitated excavation to depths of from 5 to 20 feet. Surface irregularities consist of eroded grooves and channels and three pronounced depressions over the foundation area, one being a minor fault zone near the right abutment. The river bed is approximately 3,000 feet wide between the rock abutments which arise from the canyon floor on about 12:1 and 1:1 slopes, respectively, at the right and left canyon walls. The river bends sharply from a westerly to a northerly course, just upstream from the dam site. Field tests to determine the depth of overburden and quality of bedrock were begun in 1921. Fourteen diamond drill holes were put down at that time and additional holes were drilled in 1930. In 1933 a more extensive drilling program was begun, to obtain samples representative of the entire foundation area. The explorations included a series of vertical and inclined borings into bedrock, test shafts and Artists conception of the completed Grand Coulee Dam and Power Plant with Government town at the right. trenches, and a geophysical survey. The total length of the diamond drill holes exceeds 7 miles and the core samples provided early information that the bedrock possesses adequate bearing capacity. The foundation and abutment material is composed of granite, ranging from a massive or coarse-grained type on the right side to a fine-grained porphyritic type approaching the left abutment. The rock has proved to be hard and sound and well suited to resist the pressures transmitted by the dam. A heavy overburden of silt, with occasional strata of sand or gravel and an upper layer of river drift containing boulders, gravel, and sand in various proportions, covered the bedrock to depths ranging from 20 to 150 feet. GRAND COULEE Grand Coulee begins a short distance upstream from the left abutment of the dam and extends more than 50 miles along an irregular course in a southwesterly direction, varying in width from 2 to 5 miles. The rock formation consists of an underlying granite floor which was subsequently covered by successive lava flows. The gorge was eroded when an advancing glacier diverted the Columbia River from its natural course to cut a new outlet at a much higher elevation through the layers of lava which are more than 600 feet in height above the coulee floor. When the glacier receded, the Columbia returned to its original course, leaving the dry channel 600 feet above river level. The ancient granite is exposed for a short distance entirely across the coulee floor in addition to a considerable length of margin near the upper end of the basin. The major portions of the floor are covered with variable depths of fine grained silt which has been most heavily deposited by wind action against the east wall. The west side of the floor is strewn with numerous eroded mounds resulting from glacial deposits or broken ledges which reach massive proportions. The base of the west wall is covered to a considerable depth by talus slopes formed by an accumulation of broken ledge fragments. The upper part of the Grand Coulee gorge will be used for a regulatory reservoir in connection with pumping operations by constructing earth and rockfill dams across the north and south ends, approximately 23 miles apart. PRESENT CONSTRUCTION SCHEDULE The present construction program is a modification of the one initiated in 1933 because it is better suited to the extensive development of the Columbia River which is now accepted as the ultimate project. Although the initial development included only the lower section of the dam, Congress has authorized and appropriated funds for its completion. The contract for completion of the dam, the west |