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based :nrals limits at Outfall JOl derived from Colorado Fegvla?ion `.o. 31 table valor standard (TVS) is 6a m¢ll as CaCOs, yet the hazdness value at RS-1 ~xltic't is mcst re<',ectivt of natural conditions is 39 mgt (05/1 ti99 Sampling eve:.t). lren and?rfan}anese Based on data collec:cd by the state and'cP.A, the stream wnsistenth exceeds water quality standards for iron and manganese at station RS-5 (as stated in the draft pe. snit), therefore it appears liicei,: that a disc!targe from Octfalf 002 ~xovld corrrr.'bute rc the exceedarrce of worer quality standards and may cause exeeedances far other metals. L-PA believes it is appropriate that the penr$t conditions :ecui:e ccmpl:aree with iron and manganese water qualit;• standards far discharges from Outfall OQ2. Other Potential Water Quality Based Errluent Limit~~ EPp is also concerned ;`tat there is a lack of evaluating all potential pollutants present in the West Pa for compliance with water qualit;+ standards, and the absence of numeric limits for pollutants having a potential to exceed :voter quality standards through disc}:az3e from Outfa11002. EPA is concerned that the TR•26 and TR- 28 docs:merts may not address ail pollutants for w!tich there are water quality standards in the Rito Stcc. EPA is also concerned about the lack of a distira point of compliance and absence of pollutant monitoring for discharges from Outfall 002. We believe one approach that scold be used in this si:uativn is an in-stream poirrt of compliance at an appropriate location below Outfall 002 which would demonstrate compliance with the standards. In rite draft permit, there are no numeric iir„itations proposed for OutfaU CC2, except foe provisions expressed in TR-2E and 7'R- 28 (with TiL-Z8 not yet approved.) Since these doarments were simply incorporated by reference into the permit, EPA does not have sufEcient infornat•'on from the permit rationale :o conclude that the ccnditions of i R-26 and the vet to be approved TR-28 will ensure protection of water quality standazds in the Rito Seco. EPA suggests that the Division evaluate tht conditions ofTR- 26 and TR•28, thu will ensure compliance wish aster quality standards, and incorporate numeric limitations and approp: fate monitarirg into the permit and rationale for the permit. One possible a]ternative approach to ensure ware: quality standards aze met threug}: discharges from Outfall 002 would be io require installation of a monitoring well which intercepts a representative flow of ;he seepage which directly enters the Rro Seco, and impose limitations at that iocatiott along with monitoring conditions to ensure compliance can be demonstrated. To demonstrate representativeness of the monitoring and compliance location, the Division should clearly de.5ne the lateral and vertical extent of the seepage from and fully explain where all the seepage are located with respect to the geologic (ormatians at the site, i.e. in the alluvium, etc. P.iu~,.inum EPA is concerned that there art no limits in this permit to control discharge of aluminum even though theta appears to exist a reasonable potential for aluminum water quality criteria to be eeceeded. EP.9 believes the provisions in 40 C.F.R. Part 122.44(d)(2)(i) and (d)(l)(vi) rtquire compliance with state narrative standards espetially in those cases where the state has established designated uses and numeric criteria, but net necessarily numeric standards, for a polhtant of concern ~.e.. aluminum},