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shallow soils and sandstone. Where the ditch crosses drainages, pipes and aquaducts have <br />• been constructed to carry the flow. The main ditch has an average gravity run of four <br />feet per mile from the San Miguel River to the First Park area (Mercer, 1967). For a more <br />historical discussion on the Colorado Co-operative Company's development of the regional <br />ditch system, the reader should refer to Tab 4, Land Use. <br />The West Lateral splits off the main ditch near the northern boundary of the Nucla <br />Townsite. The West Lateral follows a ridge-top course westward from Nucla to the main <br />north-south county road, then winds south and southwest until the conveyed irrigation <br />water is used by the various shareholders located along the ditch's course. A total of 18 <br />diversions have been identified on this lateral! many consist of wooden "splitte boxes" <br />that divert a consistent proportion of the irrigation water from the lateral to fields via <br />small ditches and channels. Some diversions simply consist of pipes and hoses that also <br />route irrigation water to slightly lower elevation fields. <br />The West Lateral irrigation ditch is an unlined open channel. Where the ditch courses on <br />the ridge top separating Tuttle Draw to the north and the Calamity .Draw Valley to the <br />south, the ditch has been excavated through shallow soils into the highly fractured and <br />• weathered sandstone. Over time, the ditch channel-hottom has been subsequently scoured <br />and eroded, resulting in significant reaches of exposed and fractured sandstone. Further <br />down the ditch course, the ditch channel is constructed through deeper soils, and features <br />a sandy channel bottom. In most reaches, vegetation grows so heavily on the banksides <br />that the Colorado Co-operative Lompany performs routine cutting and cleaning to ensure the <br />integrity of the ditch channel. Occasionally, where the ditch courses through the deeper <br />soils, the ditch bottom is periodically cleaned out (dredged). The overall gradient of <br />the West Lateral irrigation ditch is approximately .014 ft/ft. <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 <br />operate up until about mid-October, depending on the length of each year's growing season. <br />During the remainder of each year, the ditch is temporarily turned on to provide water for <br />filling cisterns and stock ponds. Water delivered via this lateral and the rest of the <br />surrounding ditch system provides a water source for irrigation, drinking water and <br />livestock use, and is the dominate seasonal influence of the hydrologic regime in the <br />• vicinity of both the Nucla Mine and Nucla East mining area. <br />7-164 Revised 04/11!88 <br />