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Levels in MW--3 changed as follows : benzene decreased from 103 to <br /> 101 ug/L; toluene decreased from 12 . 0 to 6 .0 ug/L; ethylbenzene <br /> decreased from 18 . 0 to 13 .0 ug/L; xylene decreased from 36 0 to <br /> 22 0 ug/L, and TPHg decreased from 0 . 91 to 0 55 mg/L MTBE <br /> increased from 8 .0 ug/L to 12 . 0 ug/L <br /> Both MW-4 & MW-5 continue to be below detection levels for all <br /> compounds <br /> PLATES II through VI show the estimated lines of equal concen- <br /> tration of benzene, ethylbenzene, toluene, xylene, & TPHg based <br /> on the latest test results . They continue to show that the <br /> center of the plume is in the vicinity of MW-1, which has been <br /> confirmed by prior work. The shape of the plume has not changed <br /> significantly since monitoring began, indicating that it has <br /> stabilized. <br /> CONCLUSIONS : <br /> 1 The limits of the soil & water plumes have been defined in <br /> all directions . There is no indication of an offsite source . <br /> 2 The groundwater plume has migrated no more than 100 feet to <br /> . the north and 125 feet to the west of the site of UST' s, which <br /> were removed in 1989 . The highest Levels of BTEX & TPHg have <br /> consistently been recorded from MW-1, indicating that there has <br /> been very little movement of the groundwater. <br /> 3 Because the highest levels of contamination in both the soil <br /> and groundwater have been in the area of MW--1 and the north pump <br /> .island, there is a good possibility that leaking product lines <br /> and/or the fuel dispensers on the north island contributed to the <br /> soil & water contamination. <br /> On October 3, 1996, WJH submitted a workplan addendum to the San <br /> Joaquin County EHD to place seven (7) shallow soil borings or <br /> geoprobe holes in an attempt to characterize the amount & volume <br /> of contaminated soil that exists beneath the property. That <br /> workplan was approved by the County EHD on October 16, 1996 The <br /> State Cleanup Fund staff has approved the cost estimate submitted <br /> by WJH, and the work is scheduled to be completed within the next <br /> two weeks . Upon completion, a report will be prepared and sub- <br /> jittto t San Joaquin EHD for review and response. <br /> er Associates v�� VV_DGEOfSanchez 4 WLLWAJ itL'NTER <br /> • CB C""rN •ar9J <br /> * NO &I'd � <br /> 2 X21 OF CP&#'3���'i- <br />