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REGIONAL WATER BOARD REWNSE (SWRCB/OCC FILE A-1886) -6- PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0113 (NPDES NO. CA0079243) CITY OF LODI, WHITE SLOUGH WATER POLLUTION CONTROL FACILITY CONTENTION D: INCORRECT HARDNESS USED FOR ESTABLISHING EFFLUENT LIMITATIONS FOR METALS The Permit establishes Effluent Limitations for metals based on the hardness of the effluent as opposed to the ambient upstream receiving water hardness as required by Federal Regulations, the California Toxics Rule (CTR, 40 CFR 131.38(c)(4)). The Order has established the CTR metals hardness-dependent criteria based on the reasonable worst-case effluent and receiving water hardness. Effluent limitations for the discharge must be set to protect the beneficial uses of the receiving water for all discharge conditions. In the absence of the option of including condition-dependent, "floating" effluent limitations that are reflective of actual conditions at the time of discharge, effluent limitations must be set using a reasonable worst-case condition in order to protect beneficial uses for all discharge conditions. The petitioner contends that the CTR requires the use of the ambient "upstream" receiving water hardness for calculating CTR hardness-dependent metal criteria. The petitioner has misquoted the regulations. The federal regulations at 40 CFR 131.38(c)(4)(i) state, in part, "For purposes of calculating freshwater aquatic life criteria for metals from the equations in paragraph (b)(2) of this section, for waters with a hardness of 400 mg/1 or less as calcium carbonate, the actual ambient hardness of the surface water shall be used in those equations..." It does not state that the "upstream" ambient surface water hardness, it simply states the ambient hardness. The term "ambient" is not defined by statute, so it cannot be assumed to mean the upstream surface water hardness. Using the ambient hardness that is a mixture of effluent and receiving water (i.e. downstream of the discharge), is the critical hardness for calculating the CTR hardness dependent metals criteria, because, this is the area of the receiving stream that is affected by the discharge. A recent study developed by Dr. Robert Emerick, titled, Developing Protective Hardness-based Metal Effluent Limitations, indicates that using the lowest upstream receiving water hardness for establishing water quality criteria is not always the most protective for the receiving water. The study describes methodologies for assigning fixed effluent limitations for hardness based metals that will be protective under all dilution conditions when the final mixed receiving water/effluent hardness is less than 400 mg/L, without being overly restrictive. The Regional Water Board has evaluated the study and concurs that for some parameters, the beneficial uses of the receiving water are best protected using the lowest hardness value of the effluent, while for other parameters, using both the lowest hardness value of the receiving water and the lowest hardness value of the effluent is the most protective. The approach presented in Dr. Emerick's study was used for calculating the CTR hardness-dependent metals criteria in the Order.