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BATTLE MOUNTAIN RESOURCES INC./BATTLE MOUNTA/N GOLD COMPANY SAN LUIS PROTECT FAC/CITY NUMBER: CO-0045675, COSTILLA COUNTY Appendix D Responses to Cornmeal Letters: A. Battle Mountain Resources, Inc. (BMRI) Comments, May 1, 2000: These comments and the Division's responses are given in sequential order beginning with the permit and jollorving through to the rationale. /. Part I -Effluent Limimtions -Discharge Point OOIa, 0016, and Lblc a. There is no evidence provided by BMRI, or in the Division's records, that suppar the development and imposition of effluent limitations or monitoring requirements jar dvee parameters. Specifically, those are weak acid dissociable (WAD) ryanide, mercury and silver. Based on the history of the facility, and the data in the records, !here is no reasonable potential to discharge any of these constituents. Mercury is clearly discussed in the rationale. Additional discussion regarding cyanide and silver are included in this comment. These parameters should al[ be addressed in a similar fashion within the permit and rationale. That is, they should be eliminated from the effluent lirnils list and from the monitoring and reporting requirements. /n the alternative, iJlhe Division c/nooses to retain the monitoring and reporing requirements, then the parameters should be eliminated upon a 6-month demonstration period of non-detects. Cyanide is included ostensibly because it was part of the beneficiation process at t/re mine. Hox~ever, the description aj the project clearly identifies that the ryanide was used only in the mill process, x'/rich x~as designed to contain and route any upset conditions to the limed railings facility. Furhernore, at no time in the operational history of the BMRI San Luis Mine x~ere any materials associated with the cyanide process ever returned to the West Pit. Tlterejore, there is no reasonable potential jar cyanide to occur in any of the sources associated with this discharge permit. Similar to the discussion for ryanide and mercury, silver has generally not been detected at confirmed values greater than the analytical detection limit in the contributing x~astewaler sources, the treated discharge, or instreatn tnoniloring samples. Response: The Division has reevalttaled the existing data for these three parameters. For rnercurv, no detectable levels have occurred in the wastewater sources, discharge, or in the Rito Seco in the vicinity irnrnediately above or below the backfil[ed West Pit dischwrge location. The Division does concur that there is no reasonable potentiaf for rnercurv m cause or contribute to an ezceedance of a water quality standard. Thus, mercury has been added to the list of six monlhly samples to be monitored in Pan I.B.3. of the permit. Comparably, for ryanide in the samples collected by BMRI, generally no detectable levels have occurred in the wastewater sources, discharge, or in the Rito Seco in the vicinity immediately above or below the backfilled West Pit dischwrge location. However, in one sample collected at Station RS-5 by the WQCD on Jmruary 24, 2000, cyanide was found at a detectable concentration (0.01 mg/l), with dre two subsequent samples (2-8 and 3-22-2000) occurring below the minimum level of detection (<0.01 tag/I). Thus, the Division is requiring semiannual rnonitorimg for WAD C}~anide from the 001 ouffalls for a two year period, along with submission of instreatn data for WAD Cyanide located downstream of the discharge (RS-2 and RS-5) and alluvial groundwater data to verify that no cyanide continues to be detected. For silver, since detectable concentrations have been previously found in the wastewater sources at levels above the proposed chronic permit limitation, the same limits and monitoring xdll apply for silver. b. T/re most restrictive ojdte effluent (imitations from a treatment perspective are those for sulfate and dissolved manganese (secondary drinking xater standards set for aesthetic purposes). The entire treatment system has been designed to treat for those constituents using Best Available Technology (BAT). There is no evidence to suggest that any drinking xater supplies exist within 5 miles of the discharge point. Additionally, t/re historical data for monitoring points at RS-3 and RS-5 (instream monitoring locations on the Rito Seco) indicate that there are naturally-occurring sources of rwnganese in the Rito Seco. Refer to Figure 3-6 in Technical Revision 26 (/R-26) submitted in suppor of this permit application. Data at RS-3 represent the contribution from a tributary to the Rito Seco that is south of the West Pit area and unaffected by the raining activity. RS-5 is downstream of the West Pit area. Response: Wrth compliance of the limitations in this permit, the drinking water standards xdll be protected for any drinking water supplies located dox•ns[remn of this facility. Most ajlhese permit limitations are actually at much more stringent levels !Iran water quality standard-based calculated [imitations that would exist only to protect drinking water uses, since these arrtidegradation-based limits are generally at much lower levels than the water quality standard-based calculated limitations.