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-33- The cumulative effect of impounding water in sediment ponds at all three mines will also be insignificant. Because of the small relative surface disturbance at each mine, pond storage volumes are likewise small and sedimentation ponds at all mines are dewatered within 72 hours to minimize any water loss to the hydrologic system. The total worse case depletion to the Roaring Fork River by mine inflows is small. If all mine inflows were consumed and not discharged back to the receiving stream, a total of 456 acre-feet/year would be depleted from the Roaring Fork. This is only 0.06% of the total flow. Even during the low flow of 179 cfs for the period of record on Roaring Fork, the total depletion would be 0.4%. This amount is insignificant to the surface water system. (Refer to Table 4.) The impact of all mine discharges on the salt load to the Roaring Fork River can be calculated assuming a worse case mine discharge and average salt content. The total salt load to the Roaring Fork River at Glenwood Springs from mine discharges would be increased by 2.2 mg/l. This is 0.8°~ of the mean annual salt load normally carried by the Roaring Fork River. This should not cause any measurable change in the water quality of the Roaring fork River. The mine discharges are not anticipated to change the ionic characteristics of the Roaring Fork River. Total discharges are a small portion of total flow (0.06% mean annual), and do not exhibit significantly different characteristics. Trace elements and heavy metals are also not found in any high concentrations which would affect the quality in the Roaring Fork River. Any elevated levels will be diluted. The Division finds that pursuant to Rule 2.07.6(2)(c)the proposed operation will minimize effects to the prevailing hydrologic balance; and is designed to prevent damage to the hydrologic balance outside the proposed permit area.