2020-06-04_PERMIT FILE - C1981008A (2)

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Streams - Flow This section presents discussions of flow data collected at surface water monitoring sites established at the New Horizon 2 mining area. All historic data (prior to December, 1987) for each site has been compiled and is presented in Attachment 2.04.7-8 (Peabody Appendix 7-5). Please see Map 2.04.7-1 for stream monitoring site locations. Flow variability in Calamity Draw is artificially controlled by irrigation water for most of the year. From about mid-April to mid-October, the West Lateral irrigation ditch (managed by the CCC) is in continuous operation. Exact dates for turning this ditch on and off varies from year to year. Water from the West Lateral is also used primarily for irrigation and secondarily for maintaining water levels in stock ponds and domestic cisterns. Because of the operation of this ditch, the majority of flow in Calamity Draw is irrigation return water. Due to the relatively limited but heavily cultivated and developed watershed area in the upper portion of Calamity Draw, little supplemental flow from precipitation and snowmelt runoff occurs. Surface water monitoring site SW -N101 was established in Calamity Draw above the eastern boundary of the New Horizon 2 Mining Area (see Map 2.04.7-1A). SW -N101 was monitored for flow since July of 1986, as part of the baseline monitoring program established for this mining area. Attachment 2.04.7-8 (Peabody Appendix 7-5) contains instantaneous discharge measurement collected at this site since 1986. During the irrigation season, measured discharge ranged from .605 in April up to 13.4 cfs during July. Measured flows during the non -irrigation season ranged between 1.04 and 2.06 cfs. Interestingly, the short record of discharge measurements may suggest that shallow ground water discharge into Calamity from irrigated lands provided a fairly continuous source of baseflow to Calamity Draw during the non -irrigation season. Monitoring of this site was discontinued after the New Horizon 2 Mine became operational. It was replaced by two surface monitoring stations SW -N108 and SW -N109. The upstream station, SW -N108 is located just west of Lincoln Street as it flows from under the road. This station defines water quality and quantity before it enters the area potentially influenced by the mine. SW -N109 is located on Calamity Draw west of the mine permit boundary but east of the Nucla waste water lagoons. As of August of 2009, this surface water sample point will no longer be used as the downstream point on Calamity Draw. The downstream sample point will be SW -N 103, a point previously used in pre -mine data gathering by Peabody. This sample point is located southwest of the New Horizon 2 Mine area, and will include all discharge water from the full mine area on the south side. SW -N102 is established on a small tributary of Calamity Draw that returns irrigation tail waters from irrigated fields to the main channel of Calamity Draw. Flow at this site was almost entirely influenced by irrigation, although the limited discharge measurements made since July of 1986 indicated that residual discharge of shallow ground water from the irrigated fields above the site contributed some flow up through even January. During the irrigation period, measured flow ranged from .088 cfs (October) to 2.18 cfs (August). During periods of no irrigation, flow observations made at SW -N102 ranged from zero (February, March and early April) up to .031 cfs (January). SW -N107 was located about a mile and a half below SW -N101 on Calamity Draw. Flow measurements were only periodically collected at this site since July of 1986. A crest -stage gage has been installed at this site for the purpose of recording high water marks of large runoff events (rainfall or spring snowmelt runoff). These high water marks were used to determine the peak discharge of large runoff events using indirect discharge measurement techniques. Since monitoring began (July, 1986), only four events were calculated using indirect techniques: 1) 39 cfs, 11/11/86; 2) 35 cfs, 5/20/87; 3) 34 cfs, 6/22/87; and 4) 96 cfs, 8/27/87. The listed dates represent the respective visit dates that high water marks were measured at the crest gage. Page 2.04.7-19 March 2017 (TR -77)