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City of Stockton and County of San Joaquin Page 59 NPDES Permit CAS0083470 Response to Comments Permittees' actions necessary to comply with those narrative requirements to reduce or eliminate the mass of pollutants discharged. The Tentative Order requires the Permittees to demonstrate compliance by applying effective BMPs to the MEP. In summary, the reason to conduct a reasonable potential analysis is to determine whether or not it is necessary to include effluent limitations in a permit. Effluent limitations are not required to be included in MS4 permits and the Tentative Order does not seek to impose effluent limitations. Consequently, there is no reason to conduct a reasonable potential analysis. 13. Comment: (DK Comment 2(f)(4))mass limits are required for any impairing pollutants discharged through the storm system. The Tentative Permit fails to contain any mass limits. Thus, the permit is inconsistent with 40 C.F.R. Section 122.45(f)(1),which requires mass limits for all pollutants limited in permits. Mass limits based on current performance must be applied for all pollutants identified in the permit that are also listed on the 303(d) list for the permit's receiving waters. In other words,mass limits should be included for each of the pollutants identified as having a reasonable potential to cause or contribute to an exceedance of water quality standards. To the extent that numerig limitations don't apply,we would suggest that the reason"daily limits" (typical of numeric controls)might be infeasible is not applicable to "mass limits"which would be collected over time. Response: DeltaKeeper relies on 40 C.F.R. section 122.45(f)to support its claim that the Tentative Order must include mass limits. Mass limits are numeric limits expressed in terms of mass rather than concentration. The Defenders of Wildlife case specifically considered the requirement for municipal storm water permits to contain numeric effluent limitations in order to strictly comply with state water quality standards (Defenders of Wildlife v. Browner, 191 F.3d at 1161). As discussed above, the Defenders of Wildlife court determined that municipal storm water discharges need not include numeric water quality effluent limits. Therefore, mass limits are not required to be included in municipal storm water permits. Further, 40 CFR Section 122.44 supports that numeric limitations are not required for municipal storm water permits. Section 122.44(k)provides that permits shall include BMPs when"(2) authorized under section 402(p) of the CWA for the control of storm water discharges; or(3) Numeric effluent limitations are infeasible..." [40 C.F.R. § 122.44(k)]. The CWA specifically authorizes the use of BMPs for municipal storm water permits [33 U.S.C. § 1342(p)(3)(B)(iii)]. Further, the State Water Resources Control Board (State Board) has found that numeric effluent limits are infeasible for storm water discharges (State Water Resources Control Board Orders No. WQ 91-03 and No. WQ 91-04). The exceptions in subparts (2) and(3) of 40 CFR Section 122.44(k) therefore apply to municipal storm water permits. 14. Comment: (DK Comment 2(f)(5)) The Permit illegally authorizes non-storm water discharges. The MEP standard does not apply to non-storm water discharges. For such discharges, the Act establishes a flat prohibition. Section 402(p)(3)mandates that "[p]ermits for discharges from municipal storm sewers shall include a requirement to effectively prohibit non-storm water discharges into the storm sewers;. . ." 33 U.S.C. § 1342(p)(3)(B). The process established for