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Show PROBLEMS OF IMPERIAL VALLEY AND VICINITY. 69 CANAL LOCATION AT PLOT KNOB AND THENCE WESTEBLY. The,range of hills which parallels Colorado River on its right or West bank in California terminates at Pilot Knob, which lies in the extreme southeasterly corner of California. While not very high nor of largd surface exent, Pilot Knob is nevertheless a conspicuous topographic feature. This is due in a measure to its isolation. It is separated from the chain of hills and mountains to the north by a somewhat broken section of the mesa which forms the flat eastern slope of Imperial Valley, extending from the base of this mountain range to the lower-lying Imperial Valley lands. Pilot Knob is surrounded by this mesa formation on three sides, to the north, to the west, and to the south,. On its remaining easterly side its base has at times been washed by the waters of the Colorado River, and a spur of the mountain has been cut away to provide suitable foundation for the Hanlon gate with which since 1906 the flow of water into the Imperial Canal has been controlled. Southward from Pilot Knob the mesa formation is much broken up by washes which have been cut deep and wide to an outfall upon the lower delta land of the river. The mesa elevation around the base of Pilot Knob is generally at or above 200 feet in elevation. The bottoms of the sand washes on the proposed canal line are generally at about 130 to 140 feet in elevation. Between" them the remnants of the mesa, in long narrow ridges, with tops more or less broken, extend off toward the south into Mexico. The boundary line is just far enough south of Pilot Knob to leave space for a canal which, at the elevation attainable under use of Lagjuna Dam as the point of diversion, will cut through these mesa ridges and cross the intervening washes, with water grade practically at or slightly below the surface of the sand in the larger washes. At a point a little less than 2 miles from Hanlon's the canal will be out of this broken ground and the deep cut into the mesa will be continuous and uniform for about a mile and a quarter to the easterly edge of the sand hills. Entering the sand area the course of the canal fqr another mile and a quarter will continue parallel with the boundary, being here located across an area over which 'low dunes are drifting. TThese dunes are irregularly distributed. Any course through them is as good as any other course. There was, therefore, no object in departing from a direct course westerly. But a continuation of this course would send the canal through a broad area of high sand ridges. It was found that by deflecting the course of the canal toward the northwest it could be kept for a mile in a location on which the surface of the sand was but little above the surface of the mesa and that one of the main sand ridges could then be pierced in a cut only a little over one-half mile in length westerly to a long, narrow, bare stretch of mesa surface which Ijas been designated on trie maps as Government Gap. The adopted canal location will follow this gap for 1£ miles to its westerly extremity. For three-fourths of a mile thence, still on a westerly course, the canal will cut through a mass of sand with a number of summits at elevations approximately 50 feet above the surface of the mesa. It is on this stretch of canal tnat the drifting sand is most likely-to prove troublesome. Upon leaving tthis three-quarter-mile stretch the canal will be cut for about one-half mile through the westernmost ridge of sand, |
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Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : |