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<br />.' ') <br />,. , ",.) <br />'}..... <br />..... 20 <br /> <br />~, E THO POL I T ,\ N IV ATE H D] S T R leT <br /> <br />~ <br /> <br />of 84 days: 22 days in July 1950, 14 in August 1950, 21 in April <br />1951. and 27 in June 1951. <br /> <br />'Maintenance and operation of canals, conduits, siphons, tunnels. <br />and reservoirs from the Colorado River to the West Coach ell a tun. <br />nels, a distance of 168 miles, was under the direction of a superin- <br />tendent of aqueduct maintenance and a crew of 7 men with head- <br />quarters at Iron Mountain camp. The remaining 74 miles of <br />main aqueduct to Lake Mathews was maintained and operated by <br />the maintenance superintendent and his crew stationed at Lake <br />Mathews. Theil' work included regular and frequent patrols of the <br />open lined canal, inspection and sampling of stored water, cleaning <br />of brush and tu]e, from reservoir shorelines, spot application of <br />copper sulfate for algae control, removal of blow sand and debris <br />from sand t.raps and canals. and maintenance of all structures and <br />District roads on the aqueduct. <br /> <br />The removal of blow sand cuntinues to be one of the most time- <br />consuming jobs of the aqueduct maintenance forces. The canal <br />system was constructed with small sand traps consisting of con- <br />crete lined depressions 81"2 feet deep, with square openings the full <br />width of the canal bottom, located at about half-mile intervals in <br />the 14-mile section east and in the 5.mile section west of Iron <br />Mountain. The mixture of sand and algae that is dropped out in <br />these depressions is removed by pumping or by excavating with a <br />truck crane. At the end of the last canal section p"eceding Iron <br />Mountain, Eagle Mountain, and Hayfield pumping plants the flow- <br />ing water passes through more elaborate sand trap structures, each <br />consisting of ten large settlement basins, and equipped with travel- <br />ing dredge pumps for the removal of accumulated sand and other <br />debris. The velocit,' of the flowing water in canal sections with <br />three or more pumps operating at each plant will normally be suffi- <br />cient to carry most of the blow sand to the traps. At the relatively <br />low velocity resulting from a single pump flow, however, much of <br />the sand is deposited on the bottom of the canal. This condition is <br />particularly severe in the sections preceding the large sand traps <br />at Iron Mountain and Eagle Mountain. With only a one-pump flow, <br />backwater of very low velocity at these locations allows most of the <br />sand to drop out ahead of the traps, and also permits the growth of <br />water grass and algae. Removal of the sand is accomplished by <br />moving it to the traps with drag scrapers or, if it is sufficiently <br />concentrated, b," exca,'ating directly from the canal bottom using a <br />truck crane with a clamshell bucket. This operating problem will <br />