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vegetation grows so heavily on the banksides that the Colorado Cooperative 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 ft/ft. <br />Flow. Flow in the West Lateral irrigation ditch is exclusively controlled by the Colorado Cooperative <br />Company. The ditch is "turned on" usually in mid-April, and continues to operate up until about <br />mid-October, depending on the length of each year's growing season. During the remainder of <br />each year, the ditch is temporarily turned on to provide water for filling cisterns and stock ponds. <br />Water delivered via this lateral and the rest of the surrounding ditch system provides a water source <br />for irrigation, drinking water and livestock use, and is the dominate seasonal influence of the <br />hydrologic regime in the vicinity of the New Horizon Mine. <br />As a part of baseline studies initiated in and near the New Horizon 2 mining area, three surface <br />water monitoring sites were established along the West Lateral for obtaining flow and water quality <br />baseline information. These sites were SW-N104, SW-N105 and SW-N106 and were located on <br />the West Lateral at points upstream, midway and downstream of the New Horizon 2 mining area <br />(see Map 2.04.7-1A). Flow and water quality data were collected at these sites since July of 1986, <br />and are presented as Stream Gaging Report and Water Quality Reports presented in Peabody <br />Appendices 7-5 and 7-9, respectively. Monitoring of the site SW-N106 has been discontinued. <br />However, New Horizon Mine continues to monitor SW-N104 and SW-N105. <br />Surface water Site SW-N104 is located on the West Lateral, in the city limits of Nucla. <br />Instantaneous discharge measurements were made at SW-N104 in the diversion splitte box, and <br />continuous flow monitoring were conducted at this site via a stilling well and a digital water level <br />recorder located in the channel upstream of the splitte box. Coupled with the continuous stage <br />record, measurement of instantaneous discharge over time will yield a stage versus discharge <br />rating curve for SW-N1 04. Discharge measurements indicated that irrigation flow varied from a high <br />of 27.6 cfs (August, 1986) to a low of 14.9 cfs (August, 1987). Flow occasionally receded to a <br />trickle during the irrigation season, when water in the ditch was temporarily turned off due to routine <br />maintenance or unforeseen problems up-stream in the main ditch. <br />Surface water Site SW-N105 is located on the West Lateral at about the midway point between <br />2.04.7-40