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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale -Page 25 Permit No. CO-0045675 <br />V!!/. CHANGES TO PERM/T AND RAT/ONALE FOLLOWING PUBLIC NOT/CE <br />Public Notice Period, Comment Letters and Public Meeting.• (Cont.): <br />Responses to Comment Letters: (Cont.) <br />Comments: /slues related to outfall 002: <br />- Better definitions for the location and requirements jor outfalf 002 <br />- Utilizing monitoring wells !o define ourfall 002 <br />- Addressing specific flow and other [imitations and rnanitoring requirements jor outfall 002 <br />- Identifying seepage contributions as pan of the mass balance rater quality standard-based calculations <br />- Nor referencing the CDMG requirements for TR-26 and TR-28 in association x•ith the requirements for outfall 002 in the CDPS <br />discharge permit <br />- Concerns related to short-term West Pit groundwater discharge issues and long-term water groundx~ater discharge issues <br />(defining a window for identification of ground water fiox•ing through a restricted zone as points ojcornpliance; utilization of <br />additional ground rater monitoring x~ells; installation of a slurry wall) <br />- Concerns regarding the Best Management Practices requirements described for outfa[l 002 <br />Response: <br />There were a number of comments related to ourfa[l 002. /n response to these comments, severs( major revisions were made <br />relating to ourfall LYJ2. Descriptive language, as well as frgure 2 of the permit, have been revised to define the window and <br />boundary for 002. Also, a limitation that is associated with this outfall has been added in the permit which defines 002 xdth respect <br />!o maintaining a required water level depth in the West Pit that is below the water level of the Rito Seco to ensure that the hydraulic <br />gradient is reversed resulting in permanent elimination ofJlow frarn [he West Pit to the seeps on the bank of the Rito Seco. A <br />compliance schedule has also been incorporated and the Best Management Practices requirements for this outfal[ have been revised <br />in the permit to father address the existing situation. Refer to the revisions jor 002 and the compliance schedule in the permit <br />(Part /.A.S) and rationale (Sections I/.F, /V.A.1. and Vl.A.2) jor funkier information, as well as addirional discussions relating to <br />comments and responses jor outfall 002 in Appendix D of the ratiowle. <br />Comments: Including additional outfalls (or discharge points), limits, and monitoring jor the jour surface seeps; ensuring that the <br />seeps are contained and will not discharge to surface waters <br />Response: <br />No additional outfalls need to be identified in [his permit for the jour historic surface seeps, since there /tas not been flow in any of <br />the original seep locations since February 8, 2000. This issue is further discussed in pages 6, 8 and 9 ojAppendix D. <br />Comments: Other Groundx~ater Related Issues: <br />- Concerns x~itit the mining operation and reclamation activities impacting the ground water hydrology in the vicinity <br />- Impacts upon wells downgradient of the facility <br />- Indications of locations of drinking rater sources in the vicinity (Shalom Ranch, San Luis alluvial wells, etc.) <br />Response: <br />Issues relating to groundwater are addressed in the Colorado Division of Minerals and Geology (CDMG) mining permit jor this <br />facility, since impacts to groundwater jrorn the mining operation are under the jurisdiction ojtltat agency. Further injonwtion is <br />included in the General Cornrnents (page 23), as well as in conunents and responses related m groundwater on pages 8-10 of <br />Appendix D. <br />In addition, with protection ojsurjace rater quality standards through compliance xv[h [he limitations jor this permit, the <br />applicable groundx~ater standards would also be protected. <br />An indication ojthe concerns relating to the locations of the downgradient alluvial/groundwater drinking water sources (wells) have <br />been included in that portion of t/re rationale. <br />Corrvnenr: Issues Relating to the Impact to the Rilo Seco/Surface Waters/Downstream: <br />- Issues related to water quality data (surface sampling loca[iorts utilized, hardness values, seasonal considerations, stream low <br />Jlow detenniwtion, etc.) <br />Concerns regarding the impact ojthe facility's discharges upon Hater quality in tlae Rito Seco, water drawn jor irrigation and <br />other agricultural purposes, drinking wafer supplies (alluvial and ground water) downs[ream of the vicinity, and ground water <br />downgradient ojthe facility <br />Concern regarding potential impacts to existing Watershed projects in the area. <br />