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DURAY SILVER MINES <br /> Following test termination water was routed back into the ditch and the materials began to dry. OSMI <br /> collected composite samples from each stage of the system for Synthetic Precipitation Leachate <br /> Procedure tests to evaluate potential runoff quality. Results from the composite tests are attached.The <br /> leachate meets stormwater quality standards except for iron and zinc(where leachate is compared to <br /> the total standard). The material's leachate met groundwater and storm water standards except for the <br /> SRB composite as describes!below. <br /> • Cadmium in sample PILOT2018 SRBCOMP was detected at 0.00105 mg/L;above the <br /> groundwater standard of 0.001 mg/L and below the stormwater standard of 0.0045. <br /> • Copper in sample PILOT2018 SRBCOMP was detected at 0.0091 mg/L;above the groundwater <br /> standard of 0.009 mg/L,but below the stormwater standard of 0.0285 mg/L. <br /> • Iron in PILOT2018 SRBCOMP was detected at 1.72 mg/L;above h groundwater and storm water <br /> standards of 1 mg/L. <br /> • Lead in PILOT2018 SRBCOMP leachate was detected at 0.202 mg/L;above the groundwater <br /> standard of 0.044 mg/L but below the stormwater standard of 0.213 mg/L. <br /> • Silver in PILOT2018 SRBCOMP was 0.0016 mg/L;above the groundwater standard of 0.001 <br /> mg/L, but below the stormwater standard of 0.0138 mg/L. <br /> • Zinc in PILOT2018 SRBCOMP was 0.239 mg/L;above the stormwater standard of 0.23 mg/L but <br /> below the groundwater standard of 0.74 mg/L. <br /> OSMI believes the slightly elevated metals concentrations in the SRB composite sample are caused by <br /> two factors. firstly,the samples were(by necessity)taken from the top of the tanks where a small <br /> amount of are was likely incorporated. Second,the reducing conditions that had caused the <br /> sequestration of metals no longer existed at the time the sample was collected.While the system was <br /> running and reducing metals met ground and surface water standards leaving the SRB.Beyond the small <br /> amount of are accidentally incorporated into the SRBs,the only metal load to the materials is from <br /> water that would have gone through the existing water handling system.Reuse of the organic nutrient- <br /> rich material in top soil will encourage plant growth,reducing conditions,and limit overall metals <br /> mobility on the site. <br /> OSMI believes,that despite the slightly elevated metals from materials at top of the SRBs,that these <br /> materials are valuable soil amendments with significant nutrient value and requests permission to <br /> incorporate them into topsoil stock pile for later use in reclamation of the mine site slopes that will be <br /> disturbed during construction this summer of the passive water treatment system. <br /> OSMI does not believe the slightly elevated amounts of metals from the SRB would impact ground or <br /> surface waters since runoff would still be directed to the sedimentation ponds which are being <br /> incorporated into the overall passive water treatment system and therefore would be treated before <br /> said waters would leave the mine site_ <br /> Please do not hesitate to call me with concerns or questions at 970-325-9830. <br /> PO Box 564, 1900 Main Street, Unit 1,Ouray,Colorado, USA 81427 <br /> Tel.970-325-9830-,Fax. 970-325-4824 <br />