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exceed 400,000 gallons per day (gpd) during the term of the permit and <br />are likely to be on the order of 200,000 gpd. The freshwater pond is <br />filled during spring runoff and kept full until water rights are out of <br />priority. The water is either treated to meet potable and sanitary water <br />requirements, used and then treated as sanitary waste water, or <br />withdrawn for dust suppression in the mine and becomes mine water. <br />The potential effects of this water diversion on North Fork flows are <br />developed for both flow rates and flow volumes. With the existing <br />pump capacity, 450 gallons per minute (gpm), this diversion would <br />result in a measurable change in flow for low flows with return periods <br />of about 200 years or greater. Additionally, during [he extreme low <br />flow periods, MCC's water rights would be out of priority and <br />diversion would not be undertaken. <br />It is presumed that any change in flow that is less than five percent and <br />within the measurement error of a stream gauge would not result in a <br />hydrologic impact. Table 4 of this document shows the estimated <br />percent changes in North Fork flow volumes due to withdrawals for <br />projected mine requirements. <br />The NPDES permit allows for a discharge of 20,000 gpd, based on a <br />30-day average, from the sanitary waste water treatment plant. The <br />potential impact of discharge of waste water effluent would be greatest <br />when the dilution ratio for effluent is smallest. However the discharge <br />from the plant is routed through sedimentation pond MR-2R prior [o <br />discharge to the North Fork. <br />The quality of mine water is considered good and offers no problem for <br />treatment and discharge. Mine water discharge is treated in <br />sedimentation pond MB-1 and/or MB-2R or is alternatively discharged <br />through the Long Pine mine water discharge pipeline. In the near <br />future, mine water will be discharged through the Sylvester Gulch <br />mine water treatment pond. <br />Overland runoff passes over disturbed areas within the permit area to <br />one of the eight sedimentation ponds, mentioned previously in this <br />section. This water may be discharged to the North Fork or stored in <br />MB-1, MB-2R or MB-3 when water rights are in priority. From <br />previous Annual Hydrology Reports, it appears that these discharges <br />have had no adverse effect on the North Fork. In fact, the quality of <br />the discharge usually exceeds the quality of the North Fork. <br />43 <br />