2010-07-27_PERMIT FILE - M2009076 (12)

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these operating conditions (pH range of 7.5-9) as shown in the attached A Water Handbook for Metal Minim • erations, by Thomas R. Wildeman. Additionally, all process water and leachate is reclaimed/recycled by the means of a pontoon mounted pump or sump pump from the impoundment to the Mobile Mill Site Water Holding Pond, conveyed via a double-walled HDPE pipeline. Due to the remote nature of the disposal site location, visual nuisance impact to the public is minimal if not non- existent. The site cannot be seen from any public roadways. The waste has no adverse odor. Because the waste stream is water carried, there is very limited noise pollution as heavy equipment is only needed during maintenance procedures and for placement of cover materials and re-vegetation. 6.3.3(1)(1) Please refer to 6.13(1)(i), 6.3.3(1)0), and Exhibit D for a detailed explanation of how this operation will minimize disturbance to the hydrologic balance, prevent off.-site damage, and provide a stable configuration of the reclaimed area. 6.3.3(1)(m) There will be mineral processing conducted on-site within the area designated Mobile Mill Site. Mine waste rock dumps and/or ore are subjected to processing by gravity & flotation separation to remove the pyrites (FeS2)/chalcopyrites (CuFeS2)(sulfide minerals), gold, silver, lead, zinc, copper, and other trace heavy metals that associate with the sulfides (the acid producing materials). Lime and/or soda ash is added to adjust pH to 7.5-9 to precipitate metal salts as insoluble hydroxides and/or carbonates and for corrosion control (reference A Water Handbook for Metal Mining Operations, by Thomas R. Wildeman for a detailed explanation of the chemistry relative to this process). is Waste produced is inorganic, consisting of silica & alumino silicate minerals, which are essentially inert and meet SPLP standards for RCRA metals as shown in the attached lab results for waste stream characterization. The waste rock has been finely ground and resembles sand and clay (see the tailings gradation analysis included in the appendix within TRI/Environmental's geotechnical report). The toxic sulfides have been mostly removed during the milling process. The sand portion is composed of vein type material such as quartz gangue and quartz monzonite porphyries with some of the surrounding wall rock composed of metamorphic gneisses. The clays are formed from altered wall rock and feldspars and are non-expansive. This waste is water carried via a double walled pipeline to a lined settling impoundment. There is zero water discharge and the water is nearly 100% recycled back to the mill as process water. Processing can be described as follows: 1. Dump truck and/or loader arrive at the Mobile Mill Site and unload into the sheltered Crusher Feed Pile next to the crushing plant. a. This pile is a short-term stock pile that will have stormwater management measures in place to control the potential of any acid run-off. See Exhibit Drawing E15. 2. A loader will begin feeding the Crusher Feed Bin that feeds a jaw crusher. This jaw crusher will reduce any larger rock to a diameter < 1.0". 3. Once through the jaw crusher, the material is feed to a roll crusher which further reduces the material to a diameter < 1/8". This two-stage crushing operation is a dry operation and the crushed material is collected in a weather-tite Crushed Rock Bin, containing approximately 80 tons. 4. The crushed material is then feed to a ball mill. a. Here we begin to add water and lime and/or soda ash to control the pH. Water is added at a rate to achieve 60% - 70% pulp density. Ball mill solution volume is approx. 15 cu. ft. b. The rotating action of this cylindrical mill with a charge of round steel balls produces a grinding process. c. The raw dump material is capable of showing a pH of 3.5, highly acidic. • Page 9 of 35