2013-07-09_REVISION - C1981010 (7)

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Gulch. This stream segment is classified as "Aquatic Life Warm 2 ", indicating waters that are not capable of sustaining a wide variety of cold or warm water biota, including sensitive species, due to physical habitat, water flows or levels, or uncorrectable water quality conditions that result in substantial impairment of the abundance and diversity of species. The discharge rate of leachate from the toe of the Horse Gulch Fill can be expected to average approximately 31 gallons per minute over several months each year (permit application page 4 -235). Rain or snowmelt provides most natural surface water flows in Horse Gulch. A natural spring, the Horse Gulch Spring, also provides flow. This spring is located approximately 2,000 feet downstream from the toe of the Horse Gulch Fill. The Horse Gulch spring has flowed at rates between 1 and 25 gpm for several months in wetter years, and has been dry when visited in some years, as documented in Trapper's annual hydrology reports. Although flows from the Horse Gulch spring have not been adjudicated, the spring probably is an important water source for livestock and wildlife. Total dissolved solids in Horse Gulch spring water have typically been between 590 and 840 mg /1. Total dissolved solids in leachate from the Horse Gulch Fill can be expected to range between 1,000 mg /l and 4,000 mg, based on analogy with leachates discharging from Trapper's pits. If leachate discharging from the fill causes water in Horse Gulch to increase to 4,000 mg /1, it will not impair use of the spring by livestock or wildlife, based on an informal 5,000 mg /l use - suitability standard for livestock and wildlife (a value widely accepted as a use - suitability standard for livestock and wildlife). Although loading of Horse Gulch surface flows with dissolved solids from the fill would be a major local impact, it does not rise to the level of material damage because use or potential use is not likely to be impaired. An exceedance of an instream standard in Horse Gulch is unlikely because leachate from the fill will probably be alkaline (like all other Trapper leachates) and is not likely to contain high concentrations of the inorganic or metals constituents for which there are numeric standards in Horse Gulch. IV. Topsoil Soil information can be found in Section 2.6, Volume II and Section 4.9, Vol. IV. 1. The Division previously granted a variance from topsoil removal in accordance with Rule 4.06.2(2)(a). Specific areas which the operator will not strip topsoil are limited to rocky areas which occur over limited areas throughout the mine area. Each area approved is handled separately as a minor revision to the permit and no general variance is currently approved. V. Sealing of Drilled Holes and Underground Openings Sealing of wells, holes, and other openings is discussed in Section 3.3 of Vol. III of the permit application. Trapper Mining Inc. has bonded for the sealing of up to 75 exploration drill holes at an average depth of 170'. Trapper Mine 28 July 9, 2013