The Johnstown Flood by David McCullough

gardens; cows gazing upward with a stupid indifference; men in their shirt-sleeves looking on at their unfinished houses, planning out tomorrow’s work; and we riding onward, high above them, like a whirlwind.
    The adventurous journey also included, just to the east of Johnstown, a ride through the first railroad tunnel in the country and, in Pittsburgh, a ride across the first suspension bridge, an aqueduct over the Allegheny River designed by German-born John Augustus Roebling, who would later conjure up that wonder of wonders of the 1880’s, the Brooklyn Bridge.
    But from Johnstown west the canal was troubled by water shortages nearly every summer. Operations were interrupted. Business suffered at a time when business had to be especially good to make up for winter, when virtually every moving thing stopped in the mountains for weeks on end, and spring, when the floods came. Particularly troublesome was the canal basin in Johnstown. Despite all the water that rushed into the valley in springtime, along toward mid-July the basin came close to running dry.
    The solution seemed obvious enough. Put a dam in the mountains where it could hold a sufficient supply of water to keep the basin working and the canals open, even during those summers when creeks vanished and only weeds grew.
    Work began on the Western Reservoir above South Fork in 1838, after some 400 acres had been cleared of timber. The site had been selected and surveyed by Sylvester Welsh, head engineer for the canal. He proposed an earth dam of 850 feet in length, with a spillway at one or both ends “of sufficient size to discharge the waste water during freshets, and sluices to regulate the supply for the canal.” It was also important, he said, that the bed of the spillway be solid rock and that no water be permitted to pass over the top of the dam. The design of the dam was worked out by a young state engineer named William E. Morris, who approved the location because, as he stated in a report made in 1839, it was in an area where there was enough drainage to provide a “certain” supply of water. He too proposed an earth dam 850 feet across the top and 62 feet high. He estimated that it would take a year to do the job.
    The contractors chosen were James N. Moorhead of Pittsburgh and Hezekiah Packer of Williamsport. According to lengthy studies made by civil engineering experts years later, they did a competent job. Certainly they went about it with considerable care and patience and despite continuing delays. For, as it turned out, fifteen years passed before the dam was finished.
    In 1842 work was halted because the state’s finances were in such bad shape that there was simply no more money to continue the job. For the next four years nothing was done. Then when the work did start again, it was only for another two years. A local cholera epidemic caused “a general derangement in the business,” until 1850, when the project again resumed, and for the final time.
    The construction technique was the accepted one for earth dams, and, it should be said, earth dams have been accepted for thousands of years as a perfectly fine way to hold back water. They were in fact the most common kind of dam at the time the South Fork work began and they were the most economical. The basic construction material was readily available at almost any site, it was cheap, and it required a minimum of skilled labor. Virtually any gang of day laborers, and particularly any who had had some experience working on railroad embankments, was suitable. But since the basic raw material, earth, is also highly subject to erosion and scour, it is absolutely essential that a dam built of earth, no matter how thick, be engineered so that the water never goes over the top and so that no internal seepage develops. Otherwise, if properly built and maintained, an earth dam can safely contain tremendous bodies of water.
    The South Fork embankment was built of successive horizontal layers of