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The hydrologic balance, previously discussed, will be protected <br />_ through a number of procedures designed to mitigate any potential <br />• impact from mining. Temporary and permanent diversions will route <br />runoff away from disturbed areas to minimize erosion and sediment <br />loss. Temporary channels are designed to safely pass the runoff from <br />a 10-year, 24-hour precipitation event and, where necessary, will be <br />constructed using bank stabilization methods including energy <br />dissipators, sediment traps, and dug outs or a combination of these <br />methods. Drainage culverts will also use energy dissipators at the <br />outlets if necessary so that runoff will not cause additional erosion <br />and subsequently increased total suspended solids (TSS) levels. <br />Detention ponds will be used to detain runoff water from the disturbed <br />areas to allow the TSS to settle out and to attain acceptable <br />concentrations for other parameters consistent with the requirements <br />of the NPDES Permit. Any Small Area Exemptions (SAE's) employed will <br />be designed to minimize contributions of TSS to the hydrologic <br />balance. <br />infiltration and percolation of precipitation in the mine area may be <br />enhanced by the reclamation techniques of contour furrowing on <br />hillsides and the continued excellent revegetation success at Colowyo. <br />Infiltration rates for the pre-mined and post-mine condition of the <br />land were presented earlier. Striffler and Rhodes (1981) showed <br />through field measurements, using an intense rainfall simulation, that <br />infiltration capacities of the mulched and revegetated areas were much <br />greater than the pre-mine estimates. Runoff from the revegetated and <br />contour-furrowed areas has been minor to date, as documented by <br />Colowyo Mine personnel. Flows from Streeter Gulch will be moderated <br />with the detention pond. <br />Moderated flows will continue to pass through the historic drain- <br />ages. Recharge of the limited groundwater systems in the mine will <br />not be inhibited and may be enhanced through the use of the above <br />techniques. <br />Groundwater protection, per se, is not necessary in the permit area as <br />essentially no continuous groundwater system exists. Perched aquifers <br />of limited nature will be impacted only in the mine area property. <br />This water will be evaporated. The quantity of ground- water is <br />minimal as evidenced by the lack of water in test holes and the dry <br />active pit. <br />Revision Subm'~tled 6 - ~ - o I <br />n S_ ~ a Rerisfo0 No. T R- S' 1 <br />