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02i09i00 WED 19:58 FAd <br />~"t~~'Fo <br />~~ <br />~Kf,~ <br />DRAFT <br />Ref: 8EPR-EP <br />• <br />• <br />UNITED STATES ENVIRONMENTAL PROTECTION AGENCY <br />REGION 8 <br />999 79TM STREET .SUITE 500 <br />DENVER, CO 90202-2466 <br />http://www. a pa.g ov/region09 <br />Ms. Kathleen Reilly <br />Outreach and Assistance Unit <br />Water Quality Coatrol Division <br />Colorado Department of Public Health and Environment <br />4300 South Cherry Creek Drive <br />Denver, Colorado 80246-1530 <br />RE: Clarification on Recommendations for <br />Ground-Water Monitoring in the San Luis <br />Area <br />Dear Ms. Reilly: <br />In my letter to you dated January 18, 2000, I provided a simplistic analytical evaluation of <br />ground-water flow in the area azound the Town of San Luis with an estimated time of travel from <br />the Battle Mountain Gold facility to the town's drinking water-supply wells. I would like to <br />clarify the approach and purpose of this work in regard to the San Luis Water and Sanitation <br />District's (SLWSD) monitoring project. <br />Current State policy on drinking water protection within the EPA-approved ~Uellhead <br />Protection and Source Water Assessment and Protection programs calls for the delineation of <br />wellhead protection azeas (WHPAs) /source water assessment areas (SWAAs) using analytical <br />methods based on ultraconservative assumptions (ie., single input values for aquifer properties <br />and no consideration of dilution, dispersion, or other conram;nant attenuation mechmtisms). <br />State policy is to use a 5-yeaz time of travel in the determination of WHPAs/SWAAs for use in <br />these programs. The approach used in my work was an ultraconservative ground-water velocity <br />calculation which is scientifically consistent with and applied based on the recommended <br />methods for WPHA/SWAA delineation within the State's programs. The resulting value of time <br />of travel was presented for comparison versus the existing State policy of 5 years to show <br />whether or not the facility in question would be located within the WI-IPA/S WAA that would be <br />delineated based on ground-water flow time of travel determinations. <br />I~j002 <br />O (,~ ~PrinMd an RBCyCIed Paper <br />