360 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



at the rate of 15-feet-plus in two hours. A tunneling team consisted 

 of 40 men. Ten worked on each face of the tunnel, perched on four 

 platforms on a movable scaffold known as a "jumbo." Up to 100 blast 

 holes 15 feet deep were drilled. Then the jumbo was pulled back and 

 the drill holes plugged with explosive. After the detonation the 

 broken rock was loaded into trolleys, dragged to the entrance, and 

 dumped. Then the cycle would be repeated. The tunneling con- 

 tinued round the clock, the men working shifts, for 20 months. On 

 December 2, 1953, two grimy miners grinned at each other through 

 a jagged hole deep inside the mountain. The tunnel from the east 

 had met the tunnel from the west — dead on center ! Three times the 

 world tunneling time had been cut; the final record was in 1953 when 

 282 feet were bored in a single 6-day week. (This was through 

 granodiorite, a most satisfactory material for drilling.) 



The completed tunnel was 10.1 miles long with a diameter of 25 

 feet. A second, following the same route but 300 feet away, is 

 envisaged in the final development. 



THE POWERHOUSE 



Kemano hydroelectric powerplant is to be the largest underground 

 powerhouse in the world. When the full complement of 16 150,000- 

 horsepower generators are installed it will have a total capacity over 

 three times the ultimate installed capacity of Harspranget in Sweden, 

 the closest rival. Work on digging out the powerhouse cavern began 

 at the end of the summer of 1951, and this job alone took nearly two 

 years. The plant is nearly a third of a mile inside the mountain, so a 

 27-foot-wide access tunnel had first to be driven as far as the location 

 of the power chamber. A total of 570,000 tons of rock made room for 

 this. The cavern necessary to house the full eight generators envisaged 

 at the completion of Stage I (the "6-year plan" for the scheme) is 

 ample to hold the Queen Elizabeth. Today the powerhouse is 82 feet 

 wide and 135 high, and is 700 feet long. To install the eight more 

 generators allowed for in the plans the building must be cut another 

 400 feet into the rock. It will then be more than a quarter of a mile 

 long. 



The Kemano generators are driven by the largest multinozzle 

 impulse-turbines ever devised. These turbines are vertical, single- 

 runner, 4-nozzle type designed to produce 150,000 horsepower at 327 

 revolutions per minute. They drive directly 3-phase, 60-cycle, 13,800- 

 volt generators rated at 122,000 kilovolt-amperes. The power from 

 each group of generators feeds into a bank of three single-phase 

 89,000 kilovolt-ampere transformers. A 300,000- volt, 4-inch-diameter 

 power cable, with 60 pounds per square inch oil pressure, carries the 

 transformer output 2,000 feet to the surface switchyard. (This power 



