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STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Dnparlmeni of Natural Resources I ill Sherman 51., Room 21 5 Dem~cr, Colorado RO'?OS Phone: 0(131 N66-3567 FAX: 11031 N}_-RI06 May 20, 1998 Thomas C. Anderson Oxbow Mining, Inc. P.O. Box 535 Somerset, Colorado 81434 Re: Sanborn Creek Mine (Permit No. C-81-022) 1996 and 1997 Annual Hydrology Reports Dear Mr. Anderson: I~~ llEPARTMENT OF NATURAL RESOURCES Rev Rnme~ Governor tames 5. lne hheul Execmne Direanr .wchael B Lonq Dimsinn Direanr The Division has completed a review of Oxbow Mining, Inc.'s (OMI) 1997 Annual Hydrology Report and responses to our questions regarding the 1996 Annual Hydrology Report at the Sanborn Creek Mine. As a result of our review, we have the following comments: 1996 AHR l.a. Response accepted. OMI should continue monitoring well WSC DH12 as they have been doing in the past. Although the well is essentially dry, this still provides important information on the potential for flooding of the abandoned Hawk's Nest Mine. I.b. No further response is necessary at this time. The Division is receptive to changing the sampling and analysis plan if improvemenzs can be made to the monitoring program. If the ephemeral drainages (Sanborn Creek, Coal Gulch, and Hawksnest Creek) truly only flow for three months out of the year, then the monitoring program should be modified to annual full suite analyses for these drainages. Any proposed changes to the approved monitoring plan should be submitted to the Division in the form of a technical revision. l.c. No further response is necessary, as discussed in 1.b. above. 2. Response accepted. It appears that the increase in conductivity is within predictions in the PHC for the site. 3. Response accepted. Total dissolved solid concentrations have indeed increased in SC-1 and SC-2. However, OMI has no explanation for the increase. 4. Response accepted. It appears that the increase in TDS is within predictions in the PHC for the site.