Another Great Dam Bursts.
At about two o’clock on the morning of Saturday, February 22, the great upper dam of the Walnut Grove Storage Company across the Hassayampa river, in Northern Arizona, about thirty miles south of the city of Prescott, broke, and the confined water in the reservoir swept down the valley, carried away the lower dam, and rushed on in a wall forty or fifty feet high, taking everything before it in its course. The loss of life is known to reach between thirty and forty souls and may be twice as large.
The only accounts as yet received are those telegraphed to the daily papers, and the cause of the giving way of the dam can therefore not be arrived at with any certainty.
From these dispatches, however, it appears that about a hundred workmen camped about the dam first heard the rush of the water, and realizing the danger which impended, attempted to open the water weir, but were too late as the water was then dashing through a large break in the upper dam. Quoting from a press dispatch:
In less than five minutes the structure gave way and the deluge swept on to the lower dam. This structure, which was built, it was built to withstand any pressure that might be brought against it, wavered for a moment as the flood came and then melted away like a bank of sand. Through the breach the flood rolled, and sweeping down the narrow defile, the wall of dirty water, fifty feet high, carried everything before it. The valley below the lower dam is narrow and the water had no opportunity to spread out over a flat. The top of the watery wall was crested with a curling crown, in which men, animals and houses were tossed about like corks. It is known that at least thirty-three men and women were lost from the little settlement that had been built at the foot of the lower dam. What further loss of life there was lower down in the valley is not yet known. For a time it was feared that the town of Wickenburg, which lies close along the Hassayampa, where the valley widens out some miles below the reservoirs, had been wrecked in the deluge, but it now proves that the village is safe. The stream rose rapidly in its course through the town, but no great damage resulted. The entire valley, from the dam to Wickenburg, is inhabited principally by Mexican miners and ranchmen. The fall of rain and snow has been very heavy in the mountains far to the north and east, and the water in the stream was very high.
The locality chosen for the dam by the Walnut Grove Water Storage Company was one particularly well adapted to the purpose. The site, which is thirty miles south of Prescott, was once closed by a barrier of solid granite formation impounding a natural lake of vast proportions. It was gradually worn away, and when the projectors of the placer mining and irrigation scheme took it in hand all that had to be done was to replace the natural barrier with a dam. The dam was designed by Professor W. D. Blake, the well-known mining expert, but work was completed under the direction and supervision of the company and its contractors. The material used in its construction was granite, blasted away from the hill sides above the crest of the embankment.
At its base the cross section thickness of the dam was 140 feet, and at the crest 15 feet. The height was no feet, and the length at the top 400 feet. The heart of the embankment was of blasted granite dumped in from a track, and on each face were granite blocks, hoisted in by derricks. The layers of stone were graduated from twenty feet in thickness at the base to five feet at the top. The facing upon the reservoir side consisted of cedar logs imbedded vertically in the face of the masonry, and to these pine timbers, 8×8, were notched and bolted horizontally at intervals of three feet in the clear. Upon these was placed a vertical sheathing of pine planks 3×8 inches, calked and covered with tarred paper one-eighth inch thick, and then an outside sheathing of 3 x 8 inch planks.
The gatehouse was of timber and was six feet square. Twenty feet below the bottom of the gate chamber were two gates corresponding to two twenty inch iron pipes that passed through the dam. Another opening five feet square admitted water to the water tower in case of emergency. The iron pipes were imbedded in the cemented masonry part of the way through the embankment, but passed through a rock spur at the axis of the dam. The flume was of wood, with inside dimensions of 5 x 3 feet, and it had heavy outside timber frames and was set in cemented masonry extending to the bed rock throughout its length.
The waste weir was blasted out of solid rock and was twenty feet broad and five feet deep. The 12.000 cubic yards of stone taken out in its construction was dumped over the face of the dam, giving it great additional strength. Fifty thousand cubic yards of granite was used in the work upon the embankment proper. The surface of the water stored was 1000 feet above the level of the placer mines, and it was decided to use the large reservoir for storage only and a smaller dam was constructed just above the placer workings. The smaller dam was 25 feet high and 250 feet long It is understood that the works of the company have been entirely destroyed. The money losses by the calamity will reach about $1,000,000.
Later.—Press dispatches of a later date state that the water made a clean sweep down the narrow valley for seventyfive miles, to the spot where the Hassayampa empties into the Gila ; that the village of Wickenburg was wiped out, and that the loss of life will exceed 150 souls, while the damage to property will be fully $2,000,000.