Water-made Dams.

Timaru Herald, Volume LXXVIII, Issue 12021, 21 March 1903, Page 1 (Supplement)

Water-made Dams.

Some of the old-time operations of the miners for placer gold and the use of the hydraulic " giant" have suggested an, ingenious method of constructing dams for reservoirs in the West. The hydraulic giant was found to b,e a most effective and powerful agent in removing even cqm-_ pact oodies of earthen material.' A stream of -water brought from an elevation under great pressure and directed against the face of a hill in which gold was supposed to be tore its way into the. mass with tremendous force, cutting out large .'--mounts of the materials and washing them away, the waste water assorting the fine from the coarse particles. The sand and gravel thus washed away was carefully examined for the precious metal. Of recent years hydraulic power has been employed to almost reverse this process. Engineers, appreciating the great transporting and assorting power of water used in this way, have availed themselves of it to build up instead of tear down- the land ; and by carefully guiding the material loosened by the force of the water they have been able to accumulate and arrange it almost at will. The process has been found especially useful in the construction of dams. For example, if an earth dam is to be built, the material rolled nlcng by the water is carried in flumes to the selected spot. On leaving the flume small boulders and coarse gravel are at 01 ce deposited. The sand flows on farther, and the fine mud is carried in suspension for considerable distances. It is thus possible to deposit the gravel on the outer slope of the dam and the finer material in the centre, thus making a- central impervious clay wall and heavy coating of coarser gravel on the upper rnd lower faces of the dam. The material being deposited under water is thoroughly compacted, and there is less danger of settlement or of porous layers being formed than in the case of dirt placed by carts or scrapers. A number of dams, rotably in Southern California and in Texas, have been built with extraordinary speed and small expense in this way. and even high railroad embankments hqve been constructed in like manner. This method of construction of dams is being made the subject of study by the division of hydrography of the United States Geological Survey in connection with investigations as to the feasibility of reclaiming the arid lands of the West.—("Mining," Spokane, Washington, U.S.A.)