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Appendix D, Comment Letters and Public Meeting: BMRI Comments (Cont.): Page 5 /3. Paragraph (e) of that same subsection describes the x~astex~ater sources. At the time of the permit application, there were three actual or potential sources including the backfill, t/re curtain wells and the seep water. At this lime, the contributing sources are the backfill x~el/s and the curtain x~el/s. At some paint, the downgradient containment wells rngy be included in the sources. Response: This updated infornration has been indicated in the rationale. 14. /V. B.4 -Discussion of Effluent Lirnitatiorrs, paragraph (e), Cyanide, Mercury and Silver As noted in our cornrnents on the permit document, BMRI does not believe there is any evidence of documentation to srtppon the development ojeither effluent limitations or monitoring and reponing requirements for cyanide, mercury or silver. We request that the drree parameters be eliminated from the eJjluent lirnitanons lists and that the requirements for monitoring and reporting 6e eliminated. /n the alternative, we request drat explicit language be included jar all three parameters drat allows the limitations and rnorritoring and reponing requirements to be eliminated after a period oJ6 months upon a demonstration of non-detects as defined by applicable analytical techniques during that period. We reiterate that the cyanide process was never used in the backfill area, no materials that were in contact with n~anide were returned to the backfill pit. /n fact, t/re facility was sired to eliminate the potential for cyanide to come in contact with any waters of the state. Moreover, cyanide has never been confirmed in groundwater or surface water monitoring at any of the Rito Seco or groundwater monitoring stations in the vicinity of the West Pit. Response: Rejer to the previarts response discussion under comment 1. a. on page 1 oJAppendix D. /5. !n the same section describing the /WCfor theJlox• rates, the distribution of wastewater versus receiving stream is incorrect and should be 88% rather than 78%. Response: 7Tre TWC value was changed. /6. Paragraph 6, Economic Reasonableness Ei•aluation There is a typographical error in the sentence that reads, in pan "that this is a new permit xhich was not in exist at the time. " replace exist xith existence. Response: This item was corrected. /n a letter dated Julv /9, 2000, BMR! submitted a repon for a Whole Effluent Tonicity (WET) test for dre San Luis facility. This test was conducted in April 2000jor both species, which resulted in passing tests for lethality and growth. BMRT requested that WET testing be eliminated from the final permit. Since some toricity did occur, the Division determined that WET testing is still required jar the penrrit. 8. USEPA Region V//I Comment Letter of May 5, 1000: The jol[oxing responses to cornrnents by the U. S. EPA are indexed to the EPA comment letter by the roman numeral as indicated on this letter. Comment: I. Water Ouality Data in the Antidepradation Array: "It appears that the baseline water quality data used in the anti- degradation review for developing effluent (irritations jar Outfall 001 was jrom station RS-5...... EPA believes a mare appropriate baseline water quality condition would be derived from station RS-/, which is approzirnately 2 miles upstream of the Battle Mountain mining activity. ..... ' Response.• Figure 5, which has now been added to dre permit, is a geologic map of the area encompassing the West Pit facilities at the San Luis Project. The map was reproducedfrorn a Colorado School ojMines Ph.D. dissenadon that was completed in /9976y Roben Benson in the Depanrnent aJGeo(ogy. The geologic map serves as the primary basis for the observation that historical water quality data measured at the upgradient surface water monitoring station RS-1 would not reasonably reJiect the naturally occurring hydrologic and geologic processes that ultimately result in ambient water quality conditions in the reach of the Rito Seca that could be influenced by the discharge of waters associated with rater treatment activities in the West Pit. As shox•n in this figure, the primary geologic formation in the vicinity ojthe RS-! location is the Precambrian bedrock. As a result, the geornorplrologic character of the Rito Seco at the surface water station RS-1 is best described as a bedrock controlled reach xith only a thin veneer of unconsolidated alluvial material overlying [he Precambrian bedrock channel. /n addition, the valley sidewa!!s are steep resulting in a more V-shaped valley that is characteristic of river channels that have jarred in weathering resistant, competent bedrock. In contrast to [he geologic and geornorplrologic conditions present at surface water station RS-l, the region of the Rito Seco in the vicinity of the West Pit is in a completely differeru geomorphologic regimen that is more characteristic of alluvial channels.