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~' "`, ~~ Weiland Sugnet. lnc. ~nviranm~ntal Solutions June 8, 2001 Yijun Jin Rocky Mountain Consultants, Inc envlrenmental Support !or • Transportation • Land Development 825 Delaware Avenue, Suite 500 Mlning Longmont, Colorado 80501 Industry Re: Response to Request for Additional Information Letter Dated February 5, 2001 For Challenger Pit TSSP (DivIG M-85-026) Deaz Mr Jin: I have made the requested changes to the Challenger TSSP. Direct responses to your comments are given below that refer to the revised TSSP enclosed. 1. Precipitation credit has been applied to replacement (see Tables 2.3-1 and 2.3-2) 2. A recent aerial photograph has been provided in Figure 2. The appropriate free surface water area is 6.57 acres. This number has been used foc gross evaporation calculations (see Tables 2.2-1 and 2.1-2). 3. Water will not be used for reclamation irrigation. The section has been removed from the accounting form. Native grasses will thrive under normal precipitation. 4. The plan does not calculate lag evaporations and mining depletions because the outer edge of the pit is within 100 ft of the river (see page 3). If further clarification on this matter is required please contact Kathleen Sullivan at SEO. 5. A dry year water budget has been provided in the plan. 6. Water will be diverted from the through the ditch on a monthly basis during the irrigation season and measured by flow meter. Values are to be recorded in monthly accounting sheet. 7. Al has been included. 8. 20% has been used for ditch loss calculation (see Tables 2.2-1 and 2.2-2) 9. Return flows from historic ditch seepage will be maintained by running pro-rata water through ditch. 10. Surface returns have been included at 30% (see Tables 2.2-1 and 2.2-2) 11. 500 ft has been used for lagged return flow model 12. Net stream depletions have been calculated as prorata diversions less lagged return