FAILURES OF DAMS.
The Bradford earth dam, Sheffield, England, failed in March, 1864. This dam, built to supply water and furnish power to the city of Sheffield, was about 90 feet in height, 13 feet wide, and 1250 feet long, with slopes of 21/4 to 1. The dam, except for a puddle wall extending from end to end and 60 feet into the ground, was of earth loosely dumped from carts. Cast-iron outlet pipes about 500 feet in length, surrounded by clay puddle, extended through the base of the dam. While the reservoir was being filled for the first time, a leak suddenly appeared, and enlarged so rapidly that in 30 minutes the reser voir had emptied itself. The flood reached Sheffield at midnight, without warning, causing great destruction of property and the loss of 238 lives. In the official inquiry made as to the cause of the failure, it was claimed that in a work of such great magnitude the outlet pipes should not have been placed through the dam itself.
The failure of the Mill River Dam at Wil liamsburg, Mass., in 1874. was a conspicuous example of improper construction which resulted in complete saturation of the embankment. No engineer had been employed in constructing the work, and no proper means used for consolidat ing the embankment. One morning, when the water was 4 feet from the top of the dam, masses of earth were observed to slide from the outer slope of the embankment. In 20 minutes the reservoir was emptied of 100,000,000 cubic feet of water, which drowned 143 persons and de stroyed $1,000,000 worth of property.
The most disastrous reservoir failure of the nineteenth century was the destruction of the South Fork Dam, which caused the famous Johnstown flood on June 1, 1889. That this disaster was due to an insufficient wasteway has been abundantly proved. The South Fork Dam was built on the headwaters of the Cone maugh Elver, about 3 miles above Johnstown. It was of earth, 70 feet in extreme height. The dam was built as far back as 1852, and, after various changes in ownership, the reservoir, in 1880, came into the possession of the South Fork Hunting and Fishing Club of Pittsburg, Pa. The original specifications for the dam required a waterway 150 feet wide. The waterway existing at the time of the disaster was 130 feet wide at its upper end. but was obstructed by a bridge and by screens to prevent the escape of fish. It extended across a channel 176 feet long, and at its lower end only 69 feet wide. In other words, the waste was only half that orig inally contemplated. besides which a brick out let culvert had been abandoned. CmBoally heavy rains had been falling for several days, and for hours before the break occurred the water had been flowing over the entire length of the dam. When the dam was carried away,
the reservoir emptied itself in about 45 minutes. Over 2000 lives were lost in this disaster, and between $3,000,000 and $4,000,000 worth of prop • erty.
The Walnut Grove Dam, in Arizona, failed on February 22, 1890. It was one of the highest rock-fill dams ever built, having been 110 feet in height, about 10 feet thick at the top and 140 feet at the base, with a top length of some 400 feet and a bottom length of 100 feet. Both faces were composed of granite blocks. laid by hand and derrick, these dry-face walls being 20 feet thick at the base and 5 feet thick at the top. It is supposed that a very heavy rainfall and an altogether inadequate spillway caused the destruction of the dam. which was over topped for a number of hours. Many deaths re sulted from the failure.
The failure of the Fuentes masonry dam, in Spain, in 1802, was clue to defective foundation, the central part of the dam resting upon piles, instead of being carried down to bed rock. In the Habra masonry dam, in Algiers (see table), whose failure caused the drowning of 400 per sons, the disaster was probably due to defective masonry work. The failure of the Bouzcy ma sonry darn, near Epinal, France, in 1895. was caused by defective construction between the base and the foundation, although in its dimen sions the dam was carried to the extreme of lightness. The failure of the dam on the Colo rado River, at Austin, Tex., which occurred in April, 1900, was due to defective foundation, largely on account of the soft limestone rock on which the foundation was laid. The darn was 1090 feet long, 66 feet high above the founda tion, and 60 feet above low water. The up stream face of the dam was vertical, and the down-stream face was curved, giving a thickness of 66 feet at the base and 20 feet near the top. On April 7, 1900, after a heavy rainfall of sev eral days, when the water was flowing over the crest of the darn to a depth of 11.07 feet, a por tion some 500 feet in length was detached from the remainder of the dam, broke into two parts, and was carried down-stream. Two sections were left standing upright in the stream a few feet below the original portion. One of these broke up in a few hours, but the other remained intact. \\lien the dam broke, eight people in the power-house were drowned by the sudden rush of water, and during the following night the power-house itself was partially destroyed.