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During Water Year 1982, the conditional right to withdraw <br /> water from the North Fork was deemed absolute. When this <br /> water right is in priority, water can be pumped from the <br /> intake point to the freshwater pond. This water right is <br /> expected to be out of priority from July to September. <br /> The freshwater pond (FW-1) has a ten acre-foot capacity. <br /> Average withdrawals from the North Fork of the Gunnison are <br /> not expected to exceed 400,000 gallons per day (gpd) during <br /> the tern of the permit and are likely to be on the order of <br /> 200,000 gpd. The freshwater pond is filled during spring <br /> runoff tmd kept full until water rights are out: of <br /> priority. The water is either treated to meet potable and <br /> sanitanr water requirements, used and then treated as <br /> sanitary waste water, or withdrawn for dust suppression in <br /> the mine and becomes mine water. <br /> The potential effects of this water diversion on North Fork <br /> flows are developed for both flow rates and flow volumes. <br /> With the existing pump capacity, 450 gallons per minute <br /> (gpm) , this diversion would result in a measurable change <br /> in flow for low flows with return periods of about 200 <br /> years or greater. Additionally, during the extreme low <br /> flow periods, MCC's water rights would be out of priority <br /> and diversion would not be undertaken. <br /> It is presumed that any change in flow that is less than <br /> five percent and within the measurement error of a stream <br /> gauge would not result in a hydrologic impact. Table 5 <br /> shows the estimated percent changes in North Fork flow <br /> volumes due to withdrawals for projected mine requirements. <br /> The NPDES permit allows for a discharge of 10,000 gpd, <br /> based On a 30-day average, from the sanitary waste water <br /> treatment plant. The potential impact of discharge of <br /> waste water effluent would be greatest when the dilution <br /> ratio for effluent is smallest- <br /> Total mine water inflow in the F seam is estimated to not <br /> have exceeded 15 acre-feet in any one year. The quality of <br /> mine water is considered good and offers no problem for <br /> treatment and discharge. Mine water discharge is treated <br /> in sedimentation pond MB-1. B seam inflow amounts are <br /> expectedi to be similar to the mine water inflow amounts of <br /> the F seam. <br /> Overland runoff passes over disturbed areas within the <br /> permit area to one of the five sedimentation ponds, <br /> mentioned previously in this section. This water may be <br /> discharged to the North Fork or stored when water rights <br /> are in priority. From previous Annual Hydrology Reports, <br /> it appears that these discharges have had no adverse effect <br /> on the North Fork. In fact, the quality of the discharge <br /> usually exceeds the quality of the North Fork. <br /> i . Refuse Material Disposal Impacts on Surface Water - <br /> Lower Refuse Disposal Area - Runoff from the Lower <br /> Permanent Waste Disposal site will be routed through <br /> the sediment control system and must meet effluent <br /> limitations. Final designs for the waste rock pile, <br /> which include surface and subsurface drainage <br /> systems, allow for the collection of water leachate <br /> from the pile. Analysis of sample rock provided by <br /> MCC indicates that potential toxicity levels are <br /> below the Environmental Protection Agency (EPA) <br /> 38 <br />