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• of the Colorado Co-operative Company's main ditch system that originates on the San Miguel River <br />just upstream of Cottonwood Canyon (about 12 miles upstream of Naturita). Construction of the <br />main ditch commenced in 1896, and water began flowing to the First Park area (see Map <br />2.04.7-1A) via the ditch in the spring of 1904 (Mercer, 1967). The main ditch, as well as the main <br />laterals, is basically an unlined open-channel excavated in shallow soils and sandstone. Where <br />the ditch crosses drainages, pipes and aquaducts have been constructed to carry the flow. The <br />main ditch has an average gravity run of four feet per mile from the San Miguel River to the First <br />Park area (Mercer, 1967). For a more historical discussion on the Colorado Co-operative <br />Company's development of the regional ditch system, the reader should refer to Section 2.04.3, <br />Site Description and Land Use Information. <br />The West Lateral splits off the main ditch near the northern boundary of the Nucla Townsite. The <br />West Lateral follows aridge-top course westward from Nucla to the main north-south county road, <br />then winds south and southwest until the conveyed irrigation water is used by the various <br />shareholders located along the ditch's course. A total of 18 diversions have been identified on this <br />lateral; many consist of wooden "splitte boxes" that divert a consistent proportion of the irrigation <br />• water from the lateral to fields via small ditches and channels. Some diversions simply consist of <br />pipes and hoses that also route irrigation water to slightly lower elevation fields. <br />The West Lateral irrigation ditch is an unlined open channel. Where the ditch courses on the <br />ridge-top separating Tuttle Draw to the north and the Calamity Draw Valley to the south, the ditch <br />has been excavated through shallow soils into the highlyfractured and weathered sandstone. Over <br />time, the ditch channel-bottom has been subsequently scoured and eroded, resulting insignificant <br />reaches of exposed and fractured sandstone. Further down the ditch course, the ditch channel is <br />constructed through deeper soils, and features a sandy channel bottom. In most reaches, <br />vegetation grows so heavily on the banksides that the Colorado Co-operative Company performs <br />routine cutting and cleaning to ensure the integrity of the ditch channel. Occasionally, where the <br />ditch courses through the deeper soils, the ditch bottom is periodically cleaned out (dredged). The <br />overall gradient of the West Lateral irrigation ditch is approximately .014 fUft. <br />Flow. Flow in the West Lateral irrigation ditch is exclusively controlled by the Colorado <br />Co-operative Company. The ditch is "turned on" usually in mid-April, and continues to operate up <br />• until about mid-October,. depending on the length of each year's growing season. During the <br />REVISED JULY 2006 2.04.7-34 <br />