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<br /> SECOND QUARTER,2001
<br /> . GROUNDWATER MONITORING REPORT
<br /> USA STATION#110, STOCKTON
<br />' JUNE 2001
<br /> A review of the historical field data suggests that the groundwater generally flows to the east with
<br /> minor fluctuations to the north and south, as shown on Figure 5.
<br />' 3.2 Groundwater Analytical Results
<br /> 1 All petroleum compounds were non-detect(ND) at the method detection limit in MW-4P and
<br /> MW-5P. TPH G and BTEX were ND at the method detection limit in MW-5P and MW-6P. TPH
<br /> 1 G was reported in monitoring wells MW-2P,MW-3P, MW-1 and MW-2 at 590 micrograms per
<br /> liter(µg/1), 91 µg11, 610µg11, and 65 ug/l, respectively. Benzene was detected in MW-2P and
<br /> MW-1 at 15 ktg/l and 0.77 µg/1, respectively. Toluene was reported in MW-2P, MW-3P, MW-1,
<br />' AND MW-2 at 8.0,ug/l, 4.2µg/1, 20,ug/l, and 92 µg/1, respectively. Ethylbenzene was reported
<br /> in MW-2P at 1.6µg/1 and 1.1 µg11, respectively. Xylenes were also reported in MW-2P, MW-3P,
<br /> MW-1, and MW-2 at 6.0µg/1, 3.9µg11, 2.1 µg/1, and 2.1 4g/1,respectively. Using EPA Method
<br /> r 8020, MTBE was reported in MW-1P, MW-2P, MW-3P, MW-6P, MW-1, and MW-2 at 8.2
<br /> µg11, 36µg/1, 30µg/1, 36,ug/1, 47,ug/l, and 65 µg/1, respectively.
<br /> 1 Using EPA Method 8260B MTBE was reported in MW-1, MW-1P, MW-2P,MW-3P, and MW-
<br /> 6P at 51 µg11, 8.2µg11, 40 µg/1, 30µg11, and 34µg11, respectively. DIPE was reported in
<br /> MW-1P, MW-3P and MW-51? at 14 µg11, 120 µg/1 and 180µg11, respectively. TBA was reported
<br /> liein MW-1, MW-2 and MW-6P at 97 µg/l, 18 µg/1 and 46µg11, respectively. All other oxygenates
<br /> were ND at the method detection limit for this sampling event. 1,2-DCA was reported in five of
<br /> the eight wells sampled (MW-1, MW-1P, MW-3P,MW-5P, and MW-6P) at concentrations of 88
<br /> 1 µg11, 25 µg11, 10µg11, 8.7 µg11, and 4.4µg11, respectively. The groundwater analytical results for
<br /> this sampling event are summarized in Tables 2 and 3, and shown on Figures 6 and 7. Copies of
<br /> laboratory reports with COC documentation are included in Appendix B.
<br /> r3.3 Discussion
<br /> rThe 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 /> r this site is being impacted by an off-site source,probably the former Chevron site across from
<br /> Farmington Road.
<br /> 1 4.0 SCHEDULE
<br /> The third quarter sampling event for 2001 will be conducted in July 2001 and the monitoring
<br />' report will be submitted within 30 days of sampling event.
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