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One lab analysis exceeded nitrate levels with 30 mg/1 (primary <br /> drinking water standards = 10 mg/1). TDS levels were <br /> 782 mg/l and 720 mg/l at two labs. The amount of leachate <br /> flow in the underdrains is expected to be low and will be <br /> diluted in the sediment ponds with surface runoff. <br /> The lower refuse pile is expected to have no significant effects <br /> to the surface water system even under worst-case low flow <br /> conditions. The amount of leachate expected to be generated <br /> from the pile is small in relation to the adjacent drainage areas. <br /> The quality of the leachate is predicted to be comparable to <br /> similar waste piles in the North Fork valley with moderately <br /> high TDS, elevated sodium and sulfates, and low <br /> concentrations of metals. <br /> A worst-case discharge projection from the lower refuse pile <br /> has been estimated. Based on an estimated annual infiltration <br /> of 5.7 inches, an annual leachate production of about 19 <br /> acre-feet is predicted from the 40-acre upper refuse site. A <br /> seasonal maximum leaching rate was estimated at twice the <br /> average annual leaching discharging rate of 11.8 gpm. When <br /> added to the leaching rates estimated for the lower refuse pile, <br /> a worst case total seasonal discharge of nearly 50 gpm could <br /> result. <br /> No adverse impact would be anticipated with respect to <br /> arsenic, boron, cadmium, chloride, manganese, nitrate, lead, <br /> selenium and zinc since concentrations of these parameters in <br /> the leaching tests were well below the stream standards on the <br /> North Fork Gunnison River. Furthermore, no adverse impact <br /> would be anticipated with respect to total and dissolved iron, <br /> sulfate, TDS and SAR. <br /> Concerns were raised by the Division regarding surface water <br /> effects of the lower waste pile leachate reaching the North <br /> Fork Gunnison River after the waste pile sediment pond is <br /> removed and the mine site has been permanently reclaimed. In <br /> response, MCC provided an analysis of the worst case effects <br /> to the North Fork of the Gunnison from leachate generated by <br /> the lower waste pile. For the analysis, MCC assumed a <br /> 10-year 7-day low flow in the river, maximum leachate <br /> production, and that all of the leachate would reach the river <br /> undispersed and undiluted. The results of the analysis showed <br /> that the discharge would not jeopardize any receiving stream <br /> standards. The amount of discharge is so low in relation to the <br /> stream flow that there will be no adverse effects to the <br /> hydrologic balance outside the permit area. <br /> 38 <br />