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THIRD AND FOURTH QUARTER,2001
<br /> GROUNDWATER MONITORING REPORT
<br /> USA STATION#110, STOCKTON
<br /> JANUARY 2002
<br /> 3.1 Groundwater Flow and Gradient
<br /> On August 1, 2001, groundwater data collected at the site indicates that depths to groundwater
<br /> ranged from 57.44-feet below ground surface(bgs) in MW-1 to 58.39-feet bgs in MW-6P. The
<br /> groundwater elevations ranged from -31.83-feet below mean sea level (MSL) in MW-1 to-32.78
<br /> -feet MSL in MW-4P, MW-5P, and MW-6P. Groundwater elevation measurements indicate
<br /> groundwater was flowing to the east at a hydraulic gradient of approximately 0.001-feet/feet,
<br /> Groundwater elevations for August 1,2001 are shown on Figure 4.
<br /> On October 17, 2001, groundwater data collected at the site indicates that depths to groundwater
<br /> ranged from 59.51-feet below ground surface(bgs) in MW-1 to 60.59-feet bgs in MW-2P. The
<br /> groundwater elevations ranged from-33.90-feet below mean sea level (MSL)in MW-1 to-34.96
<br /> -feet MSL in MW-4P. Groundwater elevation measurements indicate groundwater was flowing
<br /> to the cast at a hydraulic gradient of approximately 0.001-feet/feet. Groundwater elevations for
<br /> October 17, 2001 are shown on Figure 5.
<br /> A review of the historical field data suggests that the groundwater generally flows to the east
<br /> with minor fluctuations to the north and south, as shown on Figure 6.
<br /> 3.2 Groundwater Analytical Results
<br /> For August 1,2001, all petroleum compounds were non-detect(ND) at the method detection
<br /> limit in MW-1P,MW-4P,MW-5P, and MW-6P. TPH G was reported in monitoring wells MW-
<br /> 2P,MW-3P, MW-1 and MW-2 at 2400 micrograms per liter(µg11), 82 µg/l, 240µg11, and 63
<br /> µg11, respectively. Benzene was detected in MW-2P at 100µg/i. Toluene was reported in MW-
<br /> 2P, MW-3P,MW-1, and MW-2 at 11 µg/l, 2.5µg11, 4.7 µg/1, and 2.3 µg/l, respectively.
<br /> Ethylbenzene was reported in MW-2P at 5.1 µg/1. Xylenes were reported in MW-2P at 15 µg/1_
<br /> Using EPA Method 8020, MTBE was reported in MW-2P, MW-3P, and MW-1 at 51 µg/l, 20
<br /> µg/l, and 29µg/1,respectively.
<br /> Using EPA Method 8260B MTBE was reported in MW-1, MW-2P,MW-3P, and MW-6P at 40
<br /> 1.4g11, 54µg11, 29µg11, and 4.8 µg/1, respectively. DIPE was reported in MW-5P and MW-6P at
<br /> 110µg/1 and 13 µg11, respectively. TBA was reported in MW-1, MW-2, MW-2P, and MW-3P at
<br /> 35 µg11, 11 µg/l, 130µg11, and 17µg11, respectively. All other oxygenates were ND at the
<br /> method detection limit for this sampling event. 1,2-DCA was reported in MVV-1P,MW-2P,
<br /> MW-5P, and MW-6P at concentrations of 10 µg/l, 13µg11, 5.7µg11, and 1.8 µg11, respectively.
<br /> The groundwater analytical results for this sampling event are summarized in Tables 2 and 3,
<br /> and shown on Figures 7 and 8. Copies of laboratory reports with COC documentation are
<br /> included in Appendix B.
<br /> For the sampling event of October 17, 2001, all petroleum compounds were non-detect(ND) at
<br /> the method detection limit in MW-1P, MW4P,MW-5P, and MW-6P. TPH G was reported in
<br /> monitoring wells MW-2P,MW-3P, and MW-1 at 1000 µg/1, 93 µg/l, and 100 µg/l, respectively.
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