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F✓q 00! 300b <br /> California Aonal Water Quality*ntrol Board <br /> Central Valley Region <br /> Steven T.Butler,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretaryfor Sacramento Main Office Governor <br /> Environmental lntemet Address: http://w .sw b.ca.gov/—mgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 10 November 1999 <br /> Mr. Terry Gardner <br /> City of Lathrop <br /> Public Works Department <br /> 16775 Howland Road <br /> Lathrop, CA 95330 <br /> DISINFECTION OF WELL MW-3 TO TREAT COLIFORM BACTERIA, CITY OF LATHROP <br /> WASTE WATER TREATMENT PLANT, SAN JOAQUIN COUNTY <br /> This letter confirms our telephone conversation on 4 November 1999 regarding the City of Lathrop's <br /> inquiry into disinfecting monitoring well MW-3 to treat elevated concentrations of coliform bacteria. <br /> The City's monitoring report for the month of September 1999 reported elevated coliform bacteria <br /> concentrations in well MW-3; reportedly, the coliform has persisted and was detected in the October <br /> 1999 monitoring event.. Review of the monitoring data in the Board's files indicates coliform has <br /> occasionally been detected in well MW-3. <br /> Development and disinfection of the well is an acceptable way to proceed. The work must be performed <br /> by a licensed water well contractor, experienced in well disinfection procedures. Subsequent to the <br /> disinfection procedure, and prior to sampling the well for coliform bacteria, the well should be pumped <br /> to adequately remove the chemicals used in the disinfection procedure. To ensure the sample collected <br /> after the disinfection procedure is representative of aquifer conditions and that the disinfectant chemical <br /> has been purged, the Board requires an additional sample be collected and analyzed for the chemical(s) <br /> used in the disinfection procedure. Submit a report of well disinfection with material safety data sheets <br /> (MSDSs) for the disinfectant used with the City's December 1999 monthly monitoring results. <br /> If you have any questions on this information,please telephone me at (916) 255-3116. <br /> TIMOTHY R. O'BRIEN <br /> Waste Discharge to Land Unit <br /> Lower Sacramento River Watershed <br /> Enclosure <br /> cc: Mike Huggins, San Joaquin County Environmental Health Department, Stockton <br /> California Environmental Protection Amency <br /> ea Recycled Paper <br />