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based -~e:als limits at Out:al] JOi dewed .`tom C:;lorade Reaula?io, `;c. 3! :able vase standard (TVS) is 3a me9 as CaCO,, ye; ?he hardness =alue at RS-' which ~s mcst ret'.~aive of natural conditions i; 39 mg, fJ5/I `;off camping ?ve,~;j - 1r:~~ and `-larcenese: &aszd or, rata cci'.ec::;d b; the state and c?.9, the st:earn consistent!•: sxcceds water quality standards for iron and mangznese at ,ration RS-5 ins stated in the drarl per-ritj, therefore it appears likei~; ,hat a discharge fro;r. Gutfal 002 •x~ould carrr.'bure to the ~xezedemce of u•vrer quality rrmrdards artd may cause cxceedmvices for other merits. EPA believes i? is appropriate tF.at the permit conditicns require compl:arce a-ith iron and ;ranganese water quality standards ter discharges from Ou:fail 002. Other Potentiai Water uality i3ased E1?.'uent Limir~~ EPA is aiso concerned :at there is a lack of evait:ating all potential pollutants present in the West Pit :or compliance with water quality standards. and the absence of rumcric limits `'or pollutants having a ;,otential to exceaj :eater quality standards through dischaz3e `tom Outfall 002. EPA is concerned that :he TR-26 and TR- 28 documems may not address all pollutants for which there are :eater euality standards in the Rito Seco. E?A is al<o concemed abcut the lack of a distir.C. point of compliance and ebsortce of pollutant monitoring for discharges from Outfall 002. We believe one approach that could be used in this situation is aaitLStrearn poirrt of compliance at an apprep.*iate )ocatic» bel~~w Outfall 002 which would demonstrate compliance with the standards. In the draft permit, that a are no numeric limitations proposed for putfatl 002, except for provisions expressed in TR-26 ard'1'R- 28 {with TR-28 not ;-et appro~cd.) Since these documents wort simple incorporated ty reference into the permit, EPA does not have sutEcient information from the permit rationale to :enclude that the conditions of iR-26 and the yet to be approved i R-28 will ensure protection ~~f water quality standards in the Rito Seco. EPA suggests that tare Division evaluate the condicons ofTR- 26 and TR-28, that will ensure compliance with water quality standards, and incorporate numeric limitations and appropriate monitoring into the permit and rationale for the permit. One passible alternative approach to ensure water gvaiity standards are met through discharges from Outfall 002 would be to requirc installation of a monitoring well which intercepts a representative flow of the seepage which directly enters the Rao Seco, and rmpose trnutauons at that totartinttatang~i+ fi It monitoring conditions To ensure compliance can be demonstrated. To demonstrate representativeness of the monitoring and compliance location, the Division should clearly deeine the lateral and vertical extent of the setpage from and fully explain where all the seepage are located with respect to the geologic formations at the site, i.e. in the alluvium, etc. 'uminu EPA is concerned that there are no limits in this permit to control discharge of aluminum even though there appears to exist a reasonable potertial for aluminum water quality criteria to be exceeded. EPA believe the provisions in 40 C.F.R. ?art 122.44(d)(1)(i) and (d)(l}(vi) require compliance with state narrative standards especially in those cases where the state has established designated uses and numeric criteria, but net necessarily numeric sandards, for a pdtlutant of concern (i.e., aluminum).