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• year to year. Water from the West Lateral is also used primarily for irrigation and secondarily for <br />maintaining water levels in stock ponds and domestic cisterns. Because of the operation of this <br />ditch, the majority of flow in Calamity Draw is irrigation return water. Due to the relatively limited <br />but heavily cultivated and developed watershed area in the upper portion of Calamity Draw, little <br />supplemental flow from precipitation and snowmelt runoff occurs. <br />Surface water monitoring Site SW-N101 was established in Calamity Draw above the eastern <br />boundary of the New Horizon 2 Mining Area (see Map 2.04.7-1A). SW-N101 was monitored for <br />flow since July of 1986, as part of the baseline monitoring program established forthis mining area. <br />Attachment 2.04.7-8 (Peabody Appendix 7-5) contains instantaneous discharge measurement <br />collected at this site since 1986. During the irrigation season, measured discharge ranged from <br />.605 in April up to 13.4 cfs during July. Measured flows during the non-irrigation season ranged <br />between 1.04 and 2.06 cfs. Interestingly, the short record of discharge measurements may <br />suggest that shallow ground water discharge into Calamity from irrigated lands provided a fairly <br />continuous source of baseflow to Calamity Draw during the non-irrigation season. Monitoring of <br />this site was discontinued after the New Horizon 2 Mine became operational. It was replaced by <br />• 'two surface monitoring stations SW-N108 and SW-N109. The upstream station, SW-N108 is <br />located just west of Lincoln Street as it flows from under the road. This station defines water quality <br />and quantity before it enters the area potentially influenced by the mine. SW-N109 is located on <br />Calamity Draw west of the mine permit boundary but east of the Nucla waste water lagoons. This <br />station will define the water quality and quantity as it leaves the site but before it is influenced by <br />the waste water lagoons. <br />SW-N102 was established on a small tributary of Calamity Draw that returns irrigation tail waters <br />from irrigated fields to the main channel of Calamity Draw. Flow at this site was almost entirely <br />ihfluenced by irrigation, although the limited discharge measurements made since Juiy of 1986 <br />indicated that residual discharge of shallow ground water from the irrigated fields above the site <br />contributed some flow up through even January. During the irrigation period, measured flow <br />ranged from .088 cfs (October) to 2.18 cfs (August). During periods of no irrigation, flow <br />observations made at SW-N2 ranged from zero (February, March and early April) up to .031 cfs <br />(January). This site is now being monitored as NPDES Outfall No. 007. <br />• SW-N107 was located about a mile and a half below SW-N101 on Calamity Draw. Flow <br />REVISED JULY 2006 2.04.7-31 <br />