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REGIONAL BOARD RESP(SE(SWRCB/OCC FILE A-1483) I STA TE BOARD DRAFT WATER QUALITY ORDER PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NOS.R5-2002-0083 AND R5-2002-0084 CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY those regulations and must do so regardless of cost. The Regional Board, therefore,requests the Draft Order be revised to clarify that the Regional Board is not required to address the section 13241 factors when it is applying a numeric or narrative water quality objective to protect a beneficial use that is different than the use addressed by the CTR criteria. The Regional Board also requests the Draft Order be revised to state that the remand includes the option of applying the CTR criterion for dichloromethane rather than conducting a 13241 analysis. Note the Draft Order appears to have an unintended error in the last sentence of the first partial paragraph on page 5. The word"chloroform"should be replaced with the word"dichloromethane". The Regional Board recommends the following revision to the last 2 sentences of the first partial paragraph in page 5 of the Draft Order: "While the Regional Board does not abuse its discretion by deriving a more stringent effluent limitation than would exist from the CTR criterion that was developed for protection of the same beneficial use as the water quality objective,when doing so, the Regional Board must address the section 13241 factors. Accordingly we remand the effluent limitation for ehlere€erm dichloromethane for consideration of the section 13241 factors or to revise the permit to apply the CTR criterion." Chloroform The Draft Order finds that the Regional Board inappropriately applied unadopted criteria for chloroform. Stockton's permit was adopted prior to the adoption of State Board Order WQO 2002-15 for the City of Vacaville, which recently addressed this issue. The Regional Board will address this issue and make necessary modifications to the permit. Diazinon The Draft Order finds that the interim effluent limit of 0.1 µg/1 is appropriate for Diazinon. However, the Draft Order finds that the permit is not clear as to whether the limit is an interim or final limit. The Draft Order remands the permit to the Regional Board to provide clarification. The Regional Board will address this issue and make necessary modifications to the permit. CONCLUSION The determination of dilution credits, ammonia reasonable potential evaluation, and the need for tertiary treatment requirements are significant permitting issues for the Stockton permit. Real-time flow data during above average wet years shows periods of little or no dilution. USEPA provided guidance and written and verbal support for the ammonia reasonable potential evaluation and DHS recommends tertiary treatment for the protection of public health. The Regional Board is pleased the State Board understands the seriousness of these issues and strongly supports the Draft Order, which upholds the Regional Board on these critical decisions. Furthermore, the Regional Board appreciates the State Board's level of effort in providing clear direction in remanding portions of Order No. R5-2002-0083. The Regional Board does not have any reservations regarding the suggested permit changes stipulated in the Draft Order.