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<br />Trapper expects that total dissolved solids (TDS) in some surface water runoff <br />will be higher for a few years after reclamation in an area. The higher TDS levels <br />will occur periodically when the contribution from precipitation and snowmelt is <br />at a minimum (base flow conditions). <br /> <br />Leachate that may discharge from the toe of the Horse Gulch Fill probably will <br />cause an increase in the dissolved solids content of natural stream flows in Horse <br />that this segment contains waters that are not capable of sustaining a wide variety <br />of cold or warm water biota, including sensitive species, due to physical habitat, <br />water flows or levels, or uncorrectable water quality conditions that result in <br />substantial impairment of the abundance and diversity of species. The discharge <br />rate of leachate from the toe of the Horse Gulch Fill can be expected to average <br />approximately 31 gallons per minute over several months each year (permit <br />application page 4-235). <br /> <br />Rain or snowmelt provides most natural surface water flows in Horse Gulch. A <br />natural spring, the Horse Gulch Spring, also provides flow. This spring is located <br />approximately 2,000 feet downstream from the toe of the Horse Gulch Fill. The <br />Horse Gulch spring has flowed at rates between 1 and 25 gpm for several months <br />in wetter years, and has been dry when visited in some years, as documented in <br />have not been adjudicated, the spring probably is an important water source for <br />livestock and wildlife. <br /> <br />Total dissolved solids in Horse Gulch spring water have typically been between <br />590 and 840 mg/l. Total dissolved solids in leachate from the Horse Gulch Fill <br />can be expected to range between 1,000 mg/l and 4,000 mg, based on analogy <br />with leachates discharging from the Trapper Mpits. If leachate discharging <br />from the fill causes water in Horse Gulch to increase to 4,000 mg/l, it will not <br />impair use of the spring by livestock or wildlife, based on an informal 5,000 mg/l <br />use-suitability standard for livestock and wildlife (a value widely accepted as a <br />use-suitability standard for livestock and wildlife). Although loading of Horse <br />Gulch surface flows with dissolved solids from the fill would be a major local <br />impact, it does not rise to the level of material damage because use or potential <br />use is not likely to be impaired. An exceedance of an instream standard in Horse <br />Gulch is unlikely because leachate from the fill will probably be alkaline (like all <br />other Trapper Mine leachates) and is not likely to contain high concentrations of <br />the inorganic or metals constituents for which there are numeric standards in <br />Horse Gulch. <br /> <br />IV. Topsoil <br /> <br /> Soil information can be found in Section 2.6, Volume II and Section 4.9, Vol. IV. <br /> <br /> <br /> <br />34 <br /> <br />Trapper MineJuly 9, 2013 <br /> <br />