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April 3, 2012 <br />RN4 <br />The applicant has also committed to replacement of any adjudicated source of water <br />that may be impacted by the proposed mining operation, as would be required by <br />Colorado water law. <br />b. Surface Water <br />The probable hydrologic consequences resulting from the mining activities to surface <br />water at the Hamilton Mine permit area will result from alterations to runoff <br />characteristics, surface configuration, and water quality. Total dissolved solids (TDS) <br />for Naturita Creek, vary from 900 to 1,750 mg/1, and are much higher than for the San <br />Miguel River, which has a weighted average TDS of 316 mg/1. According to data <br />provided by Honeywood Coal Company, sulfates vary from 500 to 963 mg/1 in <br />Naturita Creek water, whereas San Miguel River water generally has less than 100 <br />mg/1. Levels of calcium, magnesium and potassium are also higher in Naturita Creek <br />than in the San Miguel River. Naturita Creek is suitable for livestock use. To date, <br />mining activities have not contributed to changes in water quality parameters of either <br />of these streams since there have been no recorded flows from the mine site. Total <br />suspended solids (TSS) is still expected to decrease as a result of interception of water <br />by sediment ponds. Total salt loading is still expected to increase somewhat due to <br />exposure of materials not previously in contact with surface water, breakup of <br />overburden by mining activities and concentration due to evaporation of water during <br />retention in sediment ponds. <br />Samples taken during runoff resulting from 1988 snowmelt and storm events along <br />Long, Center, Section 33 and Hamilton (referred to as Broad Creek in the permit <br />application) Creeks show variability in TDS from 5,080 mg/1 on upper Hamilton <br />Creek following a storm, to 110 mg/1 on Upper Center Creek following snowmelt. <br />Sulfates varied from 3,680 mg/1 on Upper Hamilton Creek during the same storm <br />event to 110 mg/1 on Upper Center Creek during the same snowmelt runoff sampling. <br />No runoff from the disturbed area is expected during dry periods or during minor <br />precipitation and snowmelt events, due to high surface infiltration rates, evaporation <br />and interception of minor runoff by sediment ponds. <br />There is very little contribution of flow to Naturita Creek from the permit area <br />drainage While flow in Naturita Creek does increase from above the permit area to <br />its confluence with the San Miguel, the increase appears to be due primarily to <br />irrigation return flow and minor subsurface flow. Except during significant snowmelt <br />and storm events, there appears to be insufficient runoff to allow flow in the draws <br />across the proposed permit area. In those rare instances where runoff does develop, <br />little water actually reaches Naturita Creek. For example, an October 2 -3, 1988 storm <br />event contributed to flow in all draws across the permit area, yet there was no flow in <br />lower Hamilton Creek at its confluence with Naturita Creek, below where it received <br />water from the proposed permit area. This indicates that either the flow event was <br />extremely short- lived, or that flow infiltrated prior to reaching the confluence with <br />Naturita Creek. <br />Except during infrequent high precipitation events, surface runoff within the permit <br />area is insufficient to routinely mobilize constituents and transport them to receiving <br />17 <br />