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aCalifornia Regional Water Quality Control Board <br /> Central Valley Region <br /> Winston H.Hickox Steven T.Butler,Chair Gray Davis <br /> Secretaryfor Govemor <br /> Environmental _ . _ _ _ - . Sacramento Main ounce <br /> Protection Internet Address: hup://www.swrcb.m.gov/—mgcb5 <br /> 3443 Roufier Road Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 20 December 1999 <br /> Mr.Morris Allen,Director <br /> Department of Municipal Utilities <br /> 2500 Navy Drive. <br /> Stockton, CA 95206-1191 <br /> TRANSMITTAL OF HEALTH RISK ASSESSMENT COMMENTS AND REQUEST FOR <br /> TECHNICAL REPORT,STOCKTON REGIONAL WATER QUALITY CONTROL PLANT, <br /> SAN JOAQUIN COUNTY <br /> We recently received a letter(enclosed) from the Department of Health Services (DHS), dated <br /> 23 November 1999, that provided comments regarding the Comprehensive Health Risk Assessment <br /> (HRA)Final Report prepared for the City of Stockton by EOA,Inc, and submitted in May 1996. The <br /> HRA was required per Provision F.1. of Order No. 94-324 (NPDES No. CA0079138) due to indications <br /> that the discharge from the Stockton Regional Water Quality Control Plant has the reasonable potential <br /> to cause a health risk for contact recreation in the San Joaquin River in the vicinity of the discharge. <br /> DHS has determined that the HRA did not provide adequate information on scenarios that might result <br /> in illness to the recreating public, the frequency with which these situations might occur, and what can <br /> be done to prevent them. In addition to the comments, the DHS letter also presents recommendations <br /> for further analysis/actions. These recommendations require the HRA model to be re-run under specific <br /> conditions or scenarios. <br /> However,based upon the information available at this time,DHS is recommending that the Regional <br /> Board require Stockton to modify its treatment to enhance pathogen reduction, including filtration and <br /> improved disinfection. Recognizing that it will take some time to renew the entire permit for Stockton, <br /> it is our intent to propose interim actions that require Stockton to operate its existing treatment plant in a <br /> manner that minimizes the health risk for those recreating in the vicinity of the discharge, and requires <br /> additional information be developed to address the questions raised by DHS. We plan to accomplish <br /> this by reopening the existing permit, as allowed by Provision F.1. <br /> Pursuant to Section 13267 of the California Water Code, the City of Stockton is required to submit a <br /> technical report to the Regional Water Quality Control Board by 31 January 2000. The report shall <br /> evaluate the capability of the City to operate the tertiary treatment processes on a continuous basis in <br /> order to protect public health. The report should address, at a minimum, the hydraulic capacity of the <br /> filters,and the operation and maintenance costs associated with continuous operation of the filters. The <br /> report shall also summarize the City's response to the comments by DHS. If Stockton does not dispute <br /> the need for treatment plant upgrades to provide tertiary treatment,further examination of health risk <br /> will not be necessary. If, however, the City of Stockton desires to conduct further analysis prior to <br /> California Environmental Protection Agency <br /> Q* Recycled Paper , <br />