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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 for this 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 suggest <br />that shallow ground water discharge into Calamity from irrigated lands provided a fairly continuous <br />source of baseflow to Calamity Draw during the non-irrigation season. Monitoring of this site was <br />discontinued after the New Horizon 2 Mine became operational. It was replaced by two surface <br />monitoring stations SW-N108 and SW-N109. The upstream station, SW-N108 is located just west <br />of Lincoln Street as it flows from under the road. This station defines water quality and quantity <br />before it enters the area potentially influenced by the mine. SW-N109 is located on Calamity Draw <br />west of the mine permit boundary but east of the Nucla waste water lagoons. As of August of 2009, <br />this surface water sample point will no longer be used as the downstream point on Calamity Draw. <br />The downstream sample point will be SW-N1 03, a point previously used in pre-mine data gathering <br />by Peabody. This sample point is located southwest of the New Horizon #2 Mine area, and will <br />include all discharge water from the full mine area on the south side. <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 />influenced by irrigation, although the limited discharge measurements made since July 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 ranged <br />from .088 cfs (October) to 2.18 cfs (August). During periods of no irrigation, flow observations <br />made at SW-N2 ranged from zero (February, March and early April) up to .031 cfs (January). This <br />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 />measurements were only periodically collected at this site since July of 1986. A crest-stage gage <br />has been installed at this site for the purpose of recording high water marks of large runoff events <br />(rainfall or spring snowmelt runoff). These high water marks were used to determine the peak <br />discharge of large runoff events using indirect discharge measurement techniques. Since <br />2.04.7-32