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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> 2: ? Donna K.Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> a 304 East Weber Avenue, Third Floor <br /> N: =� Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • c.. �P • Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> QCi F oR°` p Robert McClellon,R.E.H.S. <br /> Laurie A.Cotulia,R.E.H.S. Fax: (209) 464-0138 <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> JOE ALDRIDGE MAR 0 7 2003 <br /> ULTRAMAR INC <br /> 685 W THIRD STREET <br /> HANFORD CA 93230 <br /> RE: Beacon #3641 SITE CODE: 1125 <br /> 1210 E. Hammer Lane ROM 000070 <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Quarterly Groundwater Monitoring Report— Fourth Quarter 2002 dated January <br /> 23, 2003, as submitted by your consultant, Horizon Environmental Inc, on <br /> January 27, 2003 and has the following comments. <br /> Included in the report was a request to modify the frequency of sampling some of <br /> the monitoring wells. This request was based on groundwater analytical data <br /> collected over the years and is Ultramar's attempt to reduce costs with the belief <br /> that the proposed reductions would not affect the quality of information needed <br /> to monitor and characterize the site. <br /> The modifications are approved with the following exceptions and/or conditions: <br /> • Annual sampling of MW5 is not approved. Samples from MW-5 indicate <br /> the water in this area has been most impacted by petroleum. The lowest <br /> concentrations of contamination in the samples from this well have <br /> occurred in the First Quarter of the year and the highest concentrations of <br /> contamination in the samples from this well have occurred in the Third <br /> Quarter of the year. Therefore, at a minimum semi-annual sampling (first <br /> and third quarters of the year) is required for this well. Any significant <br /> changes in sample results from this `sentinel well' would warrant this well <br /> being returned to quarterly sampling. <br /> • Previous modifications to quarterly sampling requirements, approved by <br /> EHD, were to reduce the number of analytes tested for. Due to major <br /> changes in the amount and type of oxygenates added to gasoline recently <br /> h/ and due to the occurrence of breakdown constituents, EHD requires that <br /> \ A - every well associated with this site (vapor, air sparge, etc) be sampled at <br /> ` least once a year for gasoline oxygenate constituents TBA, 1,2-DCA, <br /> Acetone, and MtBE by EPA Method 82608 and ethanol and methanol by <br /> 8015m. <br />