2013-07-09_REVISION - C1981010 (7)

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mining levels as surface water infiltrates more easily into the subsurface which has been disaggregated by mining. The most noticeable change in surface water quality will likely be an increase in the levels of total dissolved solids (mainly calcium sulfate) contributed by springs that discharge from the mined -out pits that have been back - filled with spoil and from Horse Gulch Fill structure. Following reclamation, each spoil - filled pit and fill structure will likely develop a flowing spring on the ground surface at the down -slope end of the pit or fill. The pit or fill effluent that discharges from a spring will be composed of water that is rich in the minerals that are dissolved from the spoil which fill the mined -out pit or that was used to construct the fill. The effluent discharging from a spoil spring or fill spring will flow downslope to the nearest drainage channel. As of 2008, the applicant considers only Johnson Gulch Spring and Spring 99 -1 to be spoil springs. All other springs on Trapper are believed to be natural springs. Water from Johnson Gulch Spring has a TDS level of around 4000 mg/l and an average iron content of 0.42 mg/l as found in samples taken in 1995 and 1996 (Appendix W of permit application). This spring supplies around 10% of the annual flow of Johnson Gulch within the permit area. The Johnson Gulch Spring water exceeds secondary drinking water standards although it is not currently used as drinking water downstream of the mine area. Cottonwood and Wapiti Springs are natural springs and have total dissolved solids concentrations usually around 1200 mg/l, similar to pre- mining levels. The applicant considers that Colt Seep, a seep that was mined through and reclaimed in 1988, discharged from a spoil aquifer. The applicant believes that during the last few years of the Colt Seep's existence, the seep's water quality was improving after having been degraded by mining. The spoil leachate that discharges from spoil springs and fill springs would be diluted during springtime runoff. The leachate from spoil springs has exceeded irrigation quality limits, but is not used for that purpose. Leachate should be acceptable for stock water and wildlife usage. Suspended solids may be elevated in surface waters in a drainage in the permit area early in the mining cycle or fill construction, until reclaimed vegetation is established to control erosion. Sediment control measures described in the permit application will reduce the sediment load added to surface waters. The applicant expects that total dissolved solids (TDS) in some surface water runoff will be higher for a few years after reclamation in an area. The higher TDS levels will occur periodically when the contribution from precipitation and snowmelt is at a minimum (base flow conditions). Leachate that may discharge from the toe of the Horse Gulch Fill probably will cause an increase in the dissolved solids content of natural stream flows in Horse Trapper Mine 27 July 9, 2013