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REGIONAL BOARD RESPONSE (SNrRCB/OCC FILE A-1483) -20-
<br /> PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS
<br /> ORDER NOS. R5-2002-0083 AND R5-2002-0084
<br /> CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY
<br /> should be the permitted flow (55 mgd), since the permit allows flows up to this amount. The harmonic
<br /> mean river flow was calculated using the available SJR flow monitoring data at Stockton. This flow is
<br /> likely elevated, since the flow monitoring data are from above average wet years. The harmonic dilution
<br /> was estimated to be 10:1,but could be less, if a more robust dataset was available.
<br /> The effluent limitation calculation procedures, in Section 1.4 of the SIP, allow for the granting of a
<br /> dilution credit, for human carcinogens, in this case 10:1 as discussed above. However, the Regional
<br /> Board found that granting of this dilution credit would allocate an unnecessarily large portion of the
<br /> River's assimilative capacity for these constituents and could violate the Antidegradation Policy.
<br /> Instead, effluent limitations were developed based on the amount of dilution that would be required, not
<br /> to exceed 10:1, such that receiving water concentrations for these constituents would be met when
<br /> effluent concentrations are at estimated maximum levels as determined by the USEPA methodology in
<br /> Section 3.3.2, pg. 52 of the TSD. The permit contains final effluent limitations for chloroform,
<br /> dichloromethane, and TCE. Only in the case of TCE was the dilution credit reduced(from 10 to 9.8).
<br /> For the remaining human carcinogens, the permit contains performance-based interim limits, which were
<br /> calculated based on Section 3.3.2, of the TSD. For more details concerning the method for calculating
<br /> the effluent limitations, please see the Fact Sheet (Section 11.4) and Table 11-5 from Order
<br /> R5-2002-0083.
<br /> "86. The effluent limitations for chloroform, dichloromethane, DBCM, BDCM, PCE, TCE, 1,1-
<br /> DCE, and bis-2 ethylhexyl phthalate were adopted without compliance with Water Code sections
<br /> 13241 and 13263."
<br /> The effluent limitations for chloroform, dichloromethane,DBCM, BDCM, PCE, 1,1-DCE, and bis-2
<br /> ethylhexyl phthalate were calculated in accordance with the SIP utilizing CTR and NTR water quality
<br /> criteria and, therefore, are not subject to Water Code sections 13241 and 13263. The effluent limitation
<br /> for TCE was calculated in accordance with the SIP except the dilution credit was reduced from 10:1 to
<br /> 9.8:1 in order to comply with the Antidegradation Policy. Based on historical performance, the RWCF
<br /> has the ability to meet the new effluent limitation for TCE without any equipment or operational
<br /> changes. Therefore, there are not significant economic impacts associated with the more stringent
<br /> interpretation of the SIP used in the calculation of the final effluent limits for TCE.
<br /> "87 The effluent limitations far chloroform, dichloromethane, DBCM, BDCM,PCE, TCE, 1,1-
<br /> DCE, and bis-2 ethylhexyl phthalate are not based on evidence in the record or adequate findings in
<br /> the Order."
<br /> The Fact Sheet(Section 11.4) and Table 11-1 from Order R5-2002-0083 provides detailed discussion
<br /> regarding the reasonable potential analysis and is referenced in Finding 27. This is the evidence in the
<br /> record that provides the basis for the need for effluent limitations for the above constituents.
<br /> "88. The effluent limitations for chloroform, 1,1-DCE, and TCE are inappropriate and
<br /> unsupported and were adopted in violation of the SIP method for calculating human health
<br /> harmonic dilution."
<br /> See response to item 85 above.
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