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WASTE DISCHARGE REQUIREMENTS -12- CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY SAN JOAQUIN COUNTY LATE REVISIONS Regional Board to consider relevant numerical criteria and guidelines developed by other agencies in determining compliance with the narrative toxicity objective. (Basin Plan, IV-17.00) In March 2000 the California Department of Fish and Game (DFG) established acute and chronic criteria for these compounds applicable to fresh water aquatic protection. Monitoring of the Delta by the Regional Board finds recurring OP pesticides concentrations exceeding the DFG criteria, affirming that no assimilative capacity exists for OP pesticides. Based on evaluation of the information provided, the discharge does have the reasonable potential to cause or contribute to an excursion above the narrative toxicity objective in the Basin Plan. The RWCF does not currently have treatment capabilities designed to meet DFG criteria applied at the outfall. It is, therefore, appropriate to establish a compliance schedule to allow time for the RWCF to comply with the DFG criteria Howev he-aw rite.ia ,,vee feleased aAer the Basin -Plaiqna_rFativey e;it eThe Basin Plan allows for a ca apliance schedule of up to ten years from the date of implementation of the new criteria in this situation, because use of the March 2000 DFG criteria is a new intMretation of the cNisting narrative toxicity water quality objective.; Ma. 2010. As a result, a time schedule for compliance with the new corresponding effluent limitation is allowable. The compliance schedule includes developing a pollution prevention plan in compliance with CWC 13263.3(d)(3) and performing a treatment feasibility study as described in Provisions G.6 and G.7. The findings of the feasibility study will be used in developing the remainder of the compliance schedule and final discharge limitations as appropriate in the next Order renewal. If the Discharger fails to conduct the studies as required in Provisions G.6 and G.7, the Regional Board will reopen this Order and impose final effluent limitations as indicated in Section 12.2, Table 12-1 of the Fact Sheet. MRP No. R5-2002-_requires continued effluent and receiving water monitoring for these pollutants with analytical reporting levels that are sensitive enough to adequately compare the results against the criteria. Chlorine 32. Chlorine is used as a disinfectant at the RWCF and is known to cause toxicity to aquatic organisms, and based on the effectiveness of dechlorination, it may, at times, be present in the effluent. Thus, there is a reasonable potential that the discharge will cause or contribute to an excursion above the narrative toxicity objective. The federal regulations at 40 CFR Section 122.44(d)(1)(vi)(B), allows the state to establish the effluent limitation using USEPA's water quality criteria. The previous Order included a daily average limitation of 0.018 mg/1 and a monthly average limitation of 0.011 mg/l, which were intended to address short-duration chlorine discharges. This revised Order sets effluent limitations of residual chlorine to be reflective of the USEPA criteria, 0.02 mg/1 as a one- hour average and 0.01 mg/l as a 4-day average. No dilution credit is granted because of the periods of little or no dilution it +he - wing water. The pr -,ribed limitations require the Discharger t� conduct c ,Li total residual chic monitoring which is currently in place at the RWCF. The Re ,onal Board finds that _ Discharger is capable of complying with the new limitations.