Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [84]
It was in 1933 when the explosive din suddenly stopped and an eerie silence descended on Boulder Canyon. The canyon walls were finally clean, the abutments sculpted, the cofferdams in place. Nearly three years after work had begun, the dam was still a figment of the imagination. Now it was time to dig down to bedrock.
The bed of the Mississippi River is hundreds, even thousands, of feet deep in silt. The Columbia and the Missouri flow over alluvial wash as thick as Arctic glaciers. On the Colorado, however, to everyone’s amazement, bedrock was struck at forty feet. A milled piece of sawtimber was found resting at the bottom of the muck, obviously of very recent origin. Since white men had begun to settle the region, perhaps eighty years before, a huge flood had evidently washed the entire channel clean. No one seemed bothered by the certainty that all of the silt constantly being relocated along the entire 1,450-mile length of the river would be forever imprisoned behind Hoover and the other dams soon to be built.
In June of 1933, the foundation was finally ready, and the first of the wooden forms that would be used to lay concrete was being built. The concrete—sixty-six million tons of it—created one of the most vexing problems the engineers had faced, a problem peculiar to large dams. The dam’s size and weight would generate superpressures and insulating mass that would both generate and retain heat. Though the dam would appear solid, it would be, in reality, a pyramid of warm pudding. Left to its own devices, Boulder Dam would require 100 years to cool down. Moreover, the cooling would be uneven, and the resultant shrinkage and warping would leave the structure fissured and cracked. After weeks of wondering what to do, the engineers finally agreed on a solution. As each form was poured, one-inch pipe would be laid through it at five-foot intervals; frigid water from a cooling plant would then be run through the pipes until convection cooling had lowered the temperature of the concrete to forty-three degrees near the base and seventy-two degrees near the crest. Since the amount of pipe required, if it had been laid out in a straight line, would have reached to Big Sur on the central California coast, this was no mean refrigeration plant. Converted to ice-making, it could have chilled a couple of million cocktails a day. Instead, it reduced a century of cooling time to something like twenty months.
When visitors were led to the canyon rim to watch Boulder Dam on the rise, there was usually a long moment of silence, a moment when the visitors groped for something appropriate to say, something that expressed proper awe and reverence for the dazzling, half-formed monstrosity they saw. The dam defied description; it defied belief. Standing on the upstream side of it, two on each flank, were the intake towers, marvelous fluted concrete columns rising 395 feet from platforms that had been blasted halfway up the canyon walls. The towers were as high as forty-story buildings, and someone who had never been to New York or Chicago or Philadelphia would never have seen a man-made stucture that high. But the crest of the dam rose nearly to the tops of the towers, and its foundation was hundreds of feet below their base. Its seamless curve swept across the canyon and imbedded itself in each side, a gigantic but somehow graceful intrusion. The men working