2018-03-09_REPORT - C1982056 (3)

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Historically, when pumping mine water from the Fish Creek Borehole (mine discharge site 115) the flow becomes a contributor to sulfate levels in Fish Creek. Fish Creek in turn contributes to the sulfate levels in Trout Creek. Trout Creek currently had a secondary drinking water standard limiting sulfate concentrations above 250 mg/l. Table 53a provides historical water quality data. 3.8 2017 Inflow Survey An inflow study was conducted underground in the fall and winter. Flow rates and field parameters were recorded for measurable inflows from the accessible areas of the underground mine. Results of this survey are presented on Figure 117, 2017 Inflow Study Mined Area (in map pouch at back of report). Note that this map also includes historic data for older underground areas, the majority of which have subsequently dried up and since moving to the Wolf Creek coal seam in 2015 only one seep remains active. Background WMD: The old WMD was closed in 1996. At that time inflows were 52 gpm. Note that water elevations for the old WMD were monitored periodically at the Fish Creek Borehole. Our best estimate is that inflows for the old WMD are still on the order of 50 to 60 gpm. Freeboard in the old WMD in the fall of 2017 was on the order of 30 feet. EMD: Longwall mining was completed in the EMD by early -January 2001. Production from the NMD, 12 Rt Longwall Panel, was underway by late January 2001. The EMD was permanently sealed in October 2001 removing all access to the 6 Rt and 7 Rt gate roads. Thus, no measurements are available in this area for 2006. Historical data is available in previous AHRs. The last flows measured for 2000 showed seasonal variations, with an average annual flow of approximately 65 gpm. Water levels for the EMD are monitored on a periodic basis at the l ORT well shaft. Freeboard in the EMD in the fall of 2017 was on the order of 80 feet. NMD: At the time of the 2010 inflow study, the mine operation had completed the 23 Rt panel. The primary sources of water came from the two most recent shafts in the 6MN area, and two fault crossings. Total inflow was estimated to be on the order of 80 gpm. Inflows continued in the Northeast Submains, although there appears to be a continued decrease in ceiling dripping. The highest inflows were about 20 gpm for the new 6MN shaft, and about 15 gpm from a floor sump at inflow site 8 (IF8) with a conductivity of 2270 (Trout Creek Water). This may have been impacted by the addition of roof drip collection to the sump system. The next highest inflow was at raise bore area (IF 38 and IF 37), which was on the order of 10-gpm (down from an estimated 20 gpm in 2005), Field conductivity measurements were about 1500 umhos/cm. This site is a blend of Wadge and Twentymile Sandstone water. Inflow at the remaining sites (primarily roof drippers) were either dry or significantly lower, often less than a gallon per minute. New Western Mining District (new WMD): The most recent inspection along the new gate roads indicated estimated inflows of less than 10 gpm. The majority of sites were modest roof drippers. Sites 70 and 72 16