• U.S.

Science: Grand Coulee Problems

3 minute read
TIME

Boulder Dam on the Colorado River is the world’s biggest dam, but the Grand Coulee project on the Columbia River will be much bigger. This mighty barrier in the wild heart of Washington, 92 miles west of Spokane, will be not only the world’s greatest but the costliest engineering job ever undertaken by man. The dam, power plant and irrigation canals will cost some $400,000,000—$25.000,000 more than the Panama Canal. The rampart across the Columbia, which has ten times the annual run-off of the Colorado, will be 4,300 ft. long, 500 ft. high. It will swallow up 9,500,000 cu. yd. of concrete, three times the quantity required for Boulder; produce 2,520,000 electric horsepower compared with 750,000 of Russia’s vaunted Dnieper. In the new dry and barren Columbia basin, Grand Coulee will irrigate and electrify 30,000 forty-acre farms capable of supporting 1,500,000 people. The lake behind it will back up 151 miles, almost to the Canadian border.

In an enterprise of such magnitude unprecedented problems and troubles have arisen. Thirty-six men have been killed in accidents, the last two on consecutive days in March. To slow down this fatality rate, the U. S. Bureau of Reclamation has instituted safety-first and first-aid instruction for the 6,000 employes. To quiet fears that the Columbia River salmon run would be ruined, plans for hatching and artificial propagation below the dam have been formulated.

One of the problems put up squarely to engineering science was that of landslides at the east bulwark. Last year while the excavators were scooping earth from a large gulch that runs 175 ft. below the low water surface of the river, 200,000 cu. yd. of clay began to slide down at the rate of two feet an hour, faster than the power shovels could get it out. The contractors were faced with a delay of several weeks and an additional excavation cost of $200,000. The engineers decided to try an old trick invented in Prussia but never before used in U. S. dam construction: freezing the front of the slide. They ran six miles of pipe into the clay, pumped in brine cooled by two big refrigerating machines, bought secondhand. The clay froze solid; the slide stopped. Cost: $30,000.

Last week came news of another novel counterattack to an onslaught of Nature. Long ago the idea of diverting the river through tunnels was discarded as too expensive and too risky, and cellular coffer dams of sheet steel were built to keep the river out of the excavation area. Three weeks ago one of these crumpled and water poured through the leak. The engineers tried vainly to stem the flow with earth, gravel, brush. Then they thought of volcanic ash. When this is moistened it swells— like oatmeal—to 15 times the dry volume, tightly plugging every crack & cranny. Tons of the puffy paste were poured into the breach and the flow of invading water shortly ceased.

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