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THIRD AND FOURTH QUARTER,2001
<br /> . GROUNDWATER MONITORING REPORT
<br /> USA STATION#110,STOCKTON
<br /> JANUARY 2002
<br /> Benzene was detected in MW-2P at 42 µg11. Toluene was reported in MW-2P,MW-3P,MW-1,
<br /> and MW-2 at 13 µg/l,4.5 µg11, 7.3 µg11, and 3.0 µg/l, respectively. Ethylbenzene was reported
<br /> in MW-2P at 1.2µg/l. Xylenes were reported in MW-2P at 6.1 µg11. Using EPA Method 8020,
<br /> MTBE was reported in MW-2P,NIW-3P, and MW-1 at 74 µg11, 25 µg/l, and 44µg11,
<br /> respectively.
<br /> For the sampling event of October 17,2001,using EPA Method 8260B, MTBE was reported in
<br /> MW-1, MW-2, MW-1P,MW-2P,MW-3P, MW-4P, and MW-5P at 43 ,ug/l, 0.77 1,4g11, 0.69µg11,
<br /> 59 µg11, 23 µg/l, 1.5µg11, and 0.50 µg11, respectively. DIPE was reported in MW-3P, MW-5P
<br /> and MW-6P at 7.1 AA 110,ug/l, and 16µg11, respectively. All other oxygenates were ND at the
<br /> method detection limit for this sampling event. 1,2-DCA was reported in MW-1, MW-1P,MW-
<br /> 2P,MW-3P,MW-5P, and MW-6P at concentrations of 1.7µg/1, 5.9 µg/l,4.8 µg11,2.3 µg/l, 5.9
<br /> µg11, and 2.0µg11, respectively. The groundwater analytical results for this sampling event are
<br /> summarized in Tables 2 and 3, and shown on Figures 9 and 10. Copies of laboratory reports
<br /> with COC documentation are included in Appendix B.
<br /> 3.3 Discussion
<br /> The appearance of DIPE and MTBE in the perimeter wells(MW-1P,MW-3P, MW-5P and MW-
<br /> 6P)and not in the interior wells seems to support our earlier suspicions that the groundwater at
<br /> this site is being impacted by an off-site source.
<br /> 4.0 SCHEDULE
<br /> The first quarter sampling event for 2002 will be conducted in January 2002 and the monitoring
<br /> report will be submitted within 30 days after receipt of the analytical test results.
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