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time. The mean dischazge of the river is 351 cfs. San Miguel River waters aze suitable for domestic <br />usage except at low flow periods when sulfate levels are high. <br />The Colorado Cooperative Ditch Company diverts as much as 145 cfs of water from the San Miguel <br />River approximately ten miles east of the town of Nucla. The main diversion ditch then flows <br />westerly passing just north of the town of Nucla and then flows northwestwazd passing north of the <br />New Horizon Mine 1. Diversion ditches distribute water to mainly agricultural users in the azea. <br />Since the completion of the irrigation system for this area in about 1910, these areas have been <br />intensively reworked for imgated agriculture. Additional uses include domestic, municipal and stock <br />pond consumption. <br />The New Horizon Mine 2 site is just west of the town of Nucla and is located in the mildly sloping <br />upland azea of both Tuttle Draw and Calamity Draw, approximately in the middle of First Pazk. <br />Especially in the New Horizon Mine 2 mining azea, the surface water system is chazacterized by a <br />"disjointed" tributazy drainage system almost completely controlled by return flow ditches of the <br />local irrigation network. <br />West Lateral Irrigation Ditch -The West Lateral irrigation ditch is part of the Colorado Co-operative <br />Company's main ditch system that originates on the San Miguel River just upstream of Cottonwood <br />Canyon (about 12 miles upstream of Naturita). Construction of the main ditch commenced in 1896, <br />and water began flowing to the First Pazk azea via the ditch in the spring of 1904 (Mercer, 1967). <br />The main ditch, as well as the main laterals, is basically an unlined open-channel excavated in <br />shallow soils and sandstone. Where the ditch crosses drainages, pipes and aquaducts have been <br />constructed to carry the flow. The main ditch has an average gravity run of four feet per mile from <br />the San Miguel River to the First Pazk azea (Mercer, 1967). For a more historical discussion on the <br />Colorado Co-operative Company's development of the regional ditch system, the reader should refer <br />to Section 2.04.3, Site Description and Land Use Information. <br />The West Lateral splits off the main ditch neaz the northern boundary of the Nucla Townsite. The <br />West Lateral follows aridge-top course westward from Nucla through the New Horizon Mine 2 azea <br />to the main north-south county road, then winds south and southwest until the conveyed imgation <br />water is used by the various shareholders located along the ditch's course. A total of 18 diversions <br />have been identified on this lateral; many consist of wooden "sputter boxes" that divert a consistent <br />proportion of the irrigation water from the lateral to fields via small ditches and channels. Some <br />diversions simply consist of pipes and hoses that also route imgation water to slightly lower <br />elevation fields. <br />The West Lateral irrigation ditch is an unlined open channel. Where the ditch courses on the <br />ridge-top sepazating Tuttle Draw to the north and the Calamity Draw Valley to the south, the ditch <br />has been excavated through shallow soils into the highly fractured and weathered sandstone. Over <br />time, the ditch channel-bottom has been subsequently scoured and eroded, resulting in significant <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. Inmost reaches, vegetation <br />grows so heavily on the banks that the Colorado Co-operative Company performs routine cutting and <br />cleaning to ensure the integrity of the ditch channel. Occasionally, where the ditch courses through <br />