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PUBLIC YfEALTH SER�iCES <br /> PaurN <br /> SAN JOAQUIN COUNTY . <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> ;. <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 9520 <br /> 209/468-3420 <br /> BRETT HUNTER JUN 2 51997 <br /> CHEVRON USA INC <br /> P O BOX 5004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron Service Station#9-444.8 4235 SITE CODE: 1952 <br /> 2905 West Benjamin Holt Drive in Stockton CA <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD)has completed review of the <br /> Blaine Tech Services"Second Quarter 1997 Monitoring Report"dated June 13, 1997. PHS/EHD has the following <br /> comments for your consideration. <br /> The report included the groundwater results of the samples collected on April 1, 1997 from the air sparge wells, GM1 <br /> -GM9 and the samples collected on May 6, 1997 from the monitoring wells, MW1 -MW9. <br /> A sample was not collected from the City of Stockton Municipal Well#10. Chevron agreed in correspondence <br /> dated January 15, 1997 to sample this well quarterly. Arrangements should be made with the City of Stockton to <br /> have this well sampled immediately. <br /> The cumulative table of well data and analytical results failed to include the results obtained from groundwater <br /> samples collected on April 1, 1997 from the air sparge wells. The table should be corrected immediately. <br /> The cumulative table of well data and analytical results indicated that 3,500 ppb methyl tertiary butyl either(MTBE) <br /> was detected in the sample collected on February 25, 1997 from the City of Stockton Municipal Well#10. PHS/EHD <br /> had reviewed the first quarter 1997 report that was dated March 25, 1997 and did not notice this sample result. <br /> Upon further investigation, it appears to be a typographical error of extreme significance. PHS/EHD verifies that <br /> analytical results which are tabulated correlate with the laboratory analytical reports that are submitted. PHS/EHD <br /> does not however verify that historical data, such as last quarter's results,are correct. The table should be corrected <br /> immediately. <br /> The cumulative table of well data and analytical results failed to include a very important laboratory notation <br /> regarding the analytical results obtained from the sample collected on May 6, 1997 from MW4. The lab noted that <br /> the TPH-gas value that was 1,400 ppb(which was reported <50 ppb)was attributed to the presence of MTBE. <br /> Laboratory notations of this nature must be noted on summary tables. The table should be corrected immediately. <br /> Monitoring well, MW4 previously has been considered a cross gradient boundary well. The results of the May <br /> sampling event suggest that there may be migrating contamination or that the newly upgraded tank system may be <br /> leaking. MTBE sample results obtained from MW4 previously ranged from 16 to 65 ppb; however, the sample <br /> results obtained most recently indicate MTBE contamination of 3,600 ppb. PHS/EHD will review next quarters <br /> analytical results which should be submitted by September 5, 1997 and determine if an additional well(s)will be <br /> necessary to define the extent of groundwater contamination. <br /> If you have any questions, please contact me at(209)468-0337. <br /> Donna Heran, REHS, Director <br /> IEnnvirronmental Health Division <br /> Y ' 1 <br /> Mary Meays, Senior REHS Margaret Lagorio, REHS <br /> Site Mitigation Unit Supervisor <br /> c: Elizabeth Thayer, CVRWQCB c: David Irey, SJC, DA Environmental Prosecution Unit <br /> c: Ed Formosa, City of Stockton MUD c: Paul Supple,ARCO <br /> c: Aaron O'Brien, Geraghty and Miller <br /> A Division of San Joaquin County Health Care Services <br />