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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale -Page 24 Permit No. CO-0045675 VIII. CHANGES TO PERMIT AND RATIONALE FOLLOWING PUBLIC NOT/CE Public Notice Period, Comment Letters and Public Meeting: (Cont.): Comment: The permit should be issued to both operator (Bartle Mountain Resources, Inc.) and owner (Battle Mountain Gold Company) Response: A number of Ilse comments asserted t/rat both Battle Mountain Gold as wet! as Battle Mountain Resources Inc. ("BMR/ ") be identified as Ilse pennittee on the final permit. /n strict accordance with the Colorado Discharge Permit System Regulations Rr~le 61.4(1), Ilse original permit application for the jaciliry identified BMR/ as the applicant because BMR/ owned.t/re land, BMR/ employees operated the jaciliry and BMR/ is the pennittee on virtually all other permits which have been in place for the facility since its initial construction. However, as BMR! has indicated in discussions with the WQCD thrortghort[ this process, Battle Mountain is committed to a satisfactory technical resolution of the West Pit issues and will respond to such comments by amending i(s application to reflect both entities as co-permittees for the jaciliN. An mnended applicant identification information xill be submi[ted. Comments: Issues related to outfall 00I: - TJre basis for determining the antidegrodation reviex~/antidegrodation limitations (using Station RS-5 vs. RS-/ or RS-2) - Including limitations and monitoring jar aluminum (for 00/ and 002) - Concerns related m radioactive constituents in the wastewater sources and the discharges (00/ and 002) - Defining the initial and later time periods jar the discharge (jar 001 and 002) Response: Arrtidegradation: Several letters contained comments regarding the antidegrodation review and the antidegrodation-based limitations. BMR/ commented that antidegrodation should not apply jar this permit. The Division has determined that the antidegrodation-based limitations in this permit are still applicable, since the discharge will be occurring for a longer term (more than one year), and this is not a temporary activity. Other comment letters stated that the baseline should be determined jrom data at Rito Seco Monitoring Station RS-I and/or RS-2, rattier than Station RS-5. The Division has reevaluated the data and conditions associated xdth each of these three surface xater sampling stations, and determined that the RS-/ location is not a representative area jar a baseline assessment. (See further discussions related to this comment in pages 5-6 of Appendix D, EPA comments, item I.) The Division also determined the baseline loading jar both of the downstream stations RS-2 and RS-5 and compared the antidegrodation-based limits for each baseline loading (as is summarized in Appendix C jar the 250 gpm discharge flow, along xith a comparison with the calculated xater quality standard-based limitations). Based upon this evaluation, the Division has concluded that the baseline loading will still be based upon Station RS-5, which overall results in more stringent and protective limitations in the permit. Further related comments and responses to the antidegrodation issues are included in Appendix D. Aluminum: Based upon the concentrations of alurninurn t/tat have been detected in the pit backfill monitoring wastewater source (as indicated in Appendix A), Ilse Division finds tlwt there is a reasonable potential for alurninurn to occur in the untreated ground rater source. Thus, limitations and rnanitoring have been added jar potentially dissolved aluminum for the 001 outfalls. Since there should be no discharge from Ilse West Pit to 002, !here ore no limits or routine monitoring jar alurninurn at this location. However, if seeps should be identified within the historically defined area as shox•n in figure 2 of the permit, parameters such as potentially dissolved alurninurn, dissolved iron, and dissolved manganese must be analyzed in samples collected. Radioactive Constituents: Witlr respect ro the radioactive constituents [hat are associated xit/r Gross Alpha Activity, disc/verge permits in Colorado have specifically identified dmt this is primarily associated with radium (226+228) and uranium. Where radioactive constituents are limited for other mining discharge permits, limits and monitoring are specified jar these two constituents, and these limits are based upon the statexade standards jar all surface waters. The BMR/ discharge permit explicitly sets limits on the concentrations ojuranium and radium discharged from the rater treatment facility. Time Periods: /n the original public noticed draft permit, there was reference m an initial tune period that included a higher discharge flow rate (400 gpm), with a later time period when disclwrge flows would be expected to decrease. Thus, nered [imimdons in t/repernrit were developed and these limits along xith dischargeJlow rate limits are based upon dischargeJlow values of 400, 250, and /00 gallons per minute (gpnr). Witlr the revisions and updates made jar this facility's permit, there is no longer any defined periods jar initial and later discharge flox~s. Thus, previous comments related to flows are no longer applicable. The tiered-disclwrge approach jar Discharge Paint 00/ provides the flexibility necessary to reasowbly represent the probable range of flows that are expected to occur during the extraction of groundwater from the West Pit. For the purposes of the COPS permit, BMR/ will pump the backfilled Wes[ Pit as necessary, up [o a rnarirnum flaw rare of 400 gpm (30 day average), to maintain a reversed hydraulic gradient jrom the Rito Seco alluvial aquifer to the West Pit.