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STATE OF CALIFORNIA GEORIH 0€UKME,11AN, (iOVerilpr <br />CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br />CENTRAL VALLEY REGION <br />3443 ROUTIER ROAD <br />SACRAMENTO, CA 95827-3098 <br />29 September 1989 <br />Ms. Diane Hinson, Registered Sanitarian <br />Environmertal Health Division <br />San Joaquin County Public Health Services <br />P.O. Box 2009 <br />Stockton, CA 95201 <br />"/VVRoCT '; 0198S9 <br />FRA%l�SFR�/C9/T y <br />U <br />STN <br />ROBERTS PETROLEUM SERVICES, 930 VICTOR ROAn, LOOT, JULY QUARTERLY GROUND WATER <br />AONIT©RING REPORT <br />We have reviewed the 7 September 1989 quarterly ground water monitnrino report <br />prepared by Ensco Environmental Services, Inc., for this Sita. The report <br />provides the analytical results for samples obtained from the on-site <br />water monitoring wells on 18 July 1989. <br />No hydrocarbon contaminants were detected in the ground water samples dur <br />this round of sampling. However, hydrocarbons were detected in samples <br />obtained from the on-site wells during the 13 January 1989 round of same <br />In addition, MW -1 which contained free -phase hydrocarbon product during <br />previnus investigations, is now dry. <br />Although the analytical results for two consecutive rounds of sampling have <br />shown no detectable levels of hydrocarbon contamination, we are concerned that <br />the free -phase hydrocarbons, previously detected in MW -1, may be migrating. <br />Therefore; we recommc A that MW --1 be replaced. This replacement well should <br />be constructed with nominal 4 -inch diameter or greater casing acid well screen <br />so that it may be used for extraction well in the event that ground water <br />remediation is necessary. <br />We also note that ground water samples obtained on 13 July 1989 were analyzed <br />on 1 August 1989. Therefore, the allowable holding time for thaw, samo1ras may <br />have been exceeded. To assure reliable analytical results, we request that <br />ground water samples obtained during future rounds of sampling be analyzed <br />more promptly. <br />If you have any questions, please call me at (916) 361--5731_ <br />THOMAS P. PELTIER <br />Engineer, g Geologist <br />TOP/tdo <br />