2016-12-01_PERMIT FILE - C1980007A

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HYDROLOGIC CHARACTERIZATION AND MONITORING PLAN The north fork of the South Prong Creek watershed encompasses an area of about 0.5 square miles. The drainage is about 0.1 miles long, extends from an elevation of approximately 8,400 to 7,800 feet amsl, and has an average gradient of about 10 percent. The north fork of South Prong Creek is a steep narrow drainage with a limited alluvial valley floor. The incised channel restricts the width of alluvium. The baseflow in this drainage originates from several springs. MCC preliminarily monitored flows and collected water quality data in South Prong Creek in the spring of 2005 and will begin actual monitoring at least one year prior to mining in the area. 2.2 Stock Ponds, Springs, and Seeps In July 2004 Wright Water Engineers (WWE) completed a stock pond, spring and seep survey of the SOD area (WWE, 2005). The boundaries of the WWE study area for this survey extended beyond the designated boundaries of the SOD and DFL areas. Stock ponds were included in the survey results if they held water at least seasonally. Stock ponds were not included if they were in disrepair and/or could no longer hold water. For survey purposes, springs were defined as "areas where groundwater issues for at least part of the year, and there is observable flow". Seeps were defined as "areas where groundwater saturates soils but do not have flowing water". A total of 25 stock ponds, 16 springs, and 82 seeps were inventoried in the WWE SOD study area during the WWE survey (WWE, 2005). Stock ponds in the SOD and DFL areas are filled by natural surface water runoff or are fed by springs or seeps. Stock ponds are not part of the monitoring program. There are three different types of springs and seeps in the SOD and DFL areas, including those which issue from alluvium, colluvium, and bedrock. Data from the West Elk Mine Permit Revision for the West Flatiron lease (PR -11) indicate that about 65 percent of the springs and seeps issue from alluvium or colluvium, 35 percent issue from bedrock, and only about 5 percent issue from the Upper or Lower Coal Series strata (CDRMS, 2005a). The flow activity of the springs and seeps is seasonal and also varies with long-term climatic conditions such as droughts. Typically, flows are greatest in the spring months and/or during wet climatic periods. Flows generally decrease in late summer and fall and/or during dry climatic periods. Some springs are ephemeral, indicating that they originate from shallow and localized water -bearing zones such as landslide deposits, colluvium, or lenticular strata. Baseline water quality data are available for 17 springs in the SOD and DFL areas including Springs J-1, J-2, J-4, J-5, J-7, WCC -5, WCC -24 Deer Creek Spring, 35-3, 96-2-2 Spring, Deep Creek Spring #2, Deep Creek Trail Spring, J-10, 2012-1, 2012-2, 2012-3, and 2012-4 (Plate 1). A summary of the water quality data for select parameters for these springs is presented in Table 2. The WY 2015 water quality and flow data for these springs are presented in Appendix C. Complete historical spring water quality and flow data are presented in AHRs completed by HydroGeo (2002 through 2016a). Monitoring data indicate that there have been no mining related impacts to any of these springs. There is only one decreed spring in the SOD and DFL areas, Deer Creek Domestic Spring (aka Deer Creek Spring) (Plate 1), which is located in Deer Creek (tributary to Dry Fork). This spring is owned by MCC and was adjudicated in 1950 for 0.1 cubic feet per second (cfs). Revised 09/07- PR12; 08/16- TR139 HydroGeo, Inc