The Mica hydro development (Fig. 1) is being constructed on the Columbia River in Canada, 135 km north of the city of P~velstoke. The hydro development (Fig. 2) is composed of a gravel-earth dam, 244 m high, 823 m long at the crest, 014 m wide at the bass, and fill volume of 32.1 million mS; underground powerhouse (Fig. 3) measuring 213 by 23 m and 49 m high with six units of 333 MW each, total capacity 2000 MW, located on the right bank; water intake for the six units, about 80 m high; left-bank open spillway designed for a maximum discharge of 4250 mS/ssc. Two 13.7-m-diamet~ tunnels, 893 and 1036 m long, designed for a maximum discharge of 4250 mS/see, were provided for on the left bank for passage of discharges during construction. The dam forms a reservoir with a volume of 23 km 3, of which the useful storage is 14.8 km s. Construction of the Mica hydro development for streamflow control and production of electrical energy is being accomplished in accord with an agreement between Canada and the USA. Additional production will be possible by equalizing the stream flow at hydro developments located on the Columbia River in the USA, which will compensate the Canadian side with 250 million dollars. In addition, the sum paid by the USA for flood control amounted to 60 miUion dollars.The transportation system for construction of the hydro development called for delivery of tl~ main freight by railroad to Rcvelstoke and thence by motor transport to the construction site. Cement is delivered from plants in the neighboring province of Alberta by motor transport over a distance of about 500 kin.Construction of the hydro development began in 1964 with development of the construction sits. In that year a temporary residential village for 2500 persons, designed for 10-15 years, was constructed south of the dam site on the bank of the Columbia. The construction administration, dining hall, clubhouse, shopping center, school, hospital, hotel, bank, etc., are located in the village. As a rule the houses are two-story, four-apartment, and of the dormitory type. * Based on materials of an official business trip.

The Bennett dam forms a reservoir with a volume of 71 km 3, of which the useful storage is 37.5 kin3," the length of the reservoir is 360 kin, and the surface area is 14,000 km 2. The dam is located in a canyon whose flanks and base are composed of sedimentary rocks, intercalating beds of sandstones and shales with interlayers of coal up to 1 m thick. The bedrocks are covered by lacustrine deposits containing clay and sand. Construction of the hydro development began in the fall of 1961 by decision of the government o f the province of British Columbia.The temporary residential village, subsidiary enterprises, a small air field, and roads within the construction area were built in 1962-1963, and the access road, about 85 km long, connecting the construction site with the railroad, was reconstructed. At this time three diversion tunnels, each 760 m long and 14.4 m in diameter with a concrete lining, were driven in the right bank. In September 1963 the river was dammed, after which construction of the 36-m-high earth cofferdam and preparation of the dam foundation began. The loose deposits and weathered rock were removed, with the exception of the foundation of the upstream cofferdam, which became a part of the upstream shoulder of the dam.To prevent subsequent differential settlement of the dam, the step slopes of the canyon flanks were flattened to 1: 1, the considerable depressions in the core abutment zone were filled with concrete, and all roughnesses on the flanks were gunited. Under the entire core of the dam the rock was grouted to a depth of 18 m. A grout curtain up to 20 m wide and up to 105 m deep was made along the entire dam front.