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Page 2 COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale -Page 29 Penult No. CO-0045675 17, M-18, M-19, M-30, M-31. M-32, and M-33. The groundwater levels will be used to develop a groundwater potentiometric surface map jot the purpose ojdetermining the direction ojgroundwater flow in the vicinity of the West Pit. IJthe measured and calculated groundwater flow direction is toward the West Pit. and the groundwater mb(e elevations in the bac~l( groundwater monitoring wells BF-4 and BF-5 are below 8381 ft ams(. then the permittee will continue to observe any flow at the seeps while conducting daily measurements of the groundwater table elevations in the West Pit bac~l( (BF-4 and BF-S) and Rito Seco alluvial aquifer (M-l6 and M-10) throughout the period of time flow occurs at the seep(s) in a volume that would allow collection of a representative wafer quality sample, unless a lesser frequency of observation is approved by WQCD. The regular monitoring program would then be followed if cessation ojJlaw at the seep(s) occurs. C) lj the groundwater potentiometric surface map or bac~ll groundwater table elevation indicates a direction aj groundwaterJlow jrom the West Pit toward the Rtto Seco alluvium, the permittee shall be required to initiate the compliance schedule response as described jorgroundwater table elevation monitoring in Section A.5(3). D) Within 3 calendar days ojidentifying seep(s) as described in this section, (he permittee steal! also: (i) confirm that the average steady-state groundwater table elevation in the downgradient Rito Seco alluvial extraction wells (M-31 and M-33) is equal fo or below 8540] amsl and (ii) collect a water quality sample jrom RS-1 to confirm that water quality standards are being met in the Rito Seco. The results ojthese measurements or observations shall be transmitted in a report to WQCD within l4 calendar days ojcompleting all ojthe measurements and observations. A separate compliance schedule activity, may be required under Sections A.5(bJ and A.S(7) ij any of these inspections or measurements indicate conditions ojthe groundwater system that are not consistent with the terms and (imitations set josh in this permit. 3) Compliance Schedule (or Downgradient Groundwater /jthe average monthly groundwater !able elevation measured in the Rito Seco alluvial aquifer at M-31 and M-33 is greater than 8540 j7 amsl, the permittee shall initiate the jollowing compliance schedule within 14 hours of the determination of groundwater mble elevation exceedance. A) The permittee steal! re-measure the groundwater levels in M-31 and M-33 within 3 days of the initial groundwater level measurements. B) !f the second round ojgroundwater level measurements confirm that the average groundwater table elevation in M- 31 and M-33 is greater than 8540 jt amsl, the permittee will be required to conduct an inspection ojthe M-32 and M-33 groundwater pumping system. C) /jthe M-31 and M-33 groundwater pumping system is deemed fully junctional and the average groundwater table elevation remains above 8540)! amsl, the permittee shall, by the end oj(he jollowing calendar day, increase the rate ojgroundwater pumping jrom M-31 and M-33 to the maximum extent possible given the ambient hydraulic properites of the the Rilo Seco alluvia! aquifer for the purpose of lowing the average groundwater table elevation below 8540 fi amsl. DJ /)the groundwater table elevation in M-31 and M-33 is equal to or below an elevation of 8540 jr ams/ by the end of the T" calendar day jollowing the start ojthe increased pumping, norms( monitoring ojthe groundwater table elevation at M-31 and M-33 will resume in accordance with the monitoring requirements set forth in Paragraph 6. E) If the groundwater fable elevation in M-31 and M-33 is not at or below 8540 jeer amsl within 7 calendar days, the permittee shall submit to the WQCD within 30 days a response plan that will result in groundwater table elevation equal to or less than 8.540 ft. ams! to re-establish hydraulic capture of Rito Seco alluvial aquifer groundwaferf]ow in M-32 and M-33. Implementation of the response plan must be in accordance with a schedule approved by the WQCD. Additionally, the WQCD may reopen the COPS permit to consider additional pit or alluvial groundwater measurement requirements, based upon the results obtained jrom implementation of the response plan, if necessary to assure maintenance ojthe hydraulic gradient reversal.