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FIRST QUARTER,2002
<br /> GROUNDWATER MONITORING REPORT
<br /> USA STATION#110, STOCKTON
<br /> APRIL 2002
<br /> 3.1 Groundwater Flow and Gradient
<br /> On January 8, 2002, groundwater data collected at the site indicated that depths to groundwater
<br /> ranged from 59.02-feet below ground surface (bgs) in MW-2 to 60.02-feet bgs in MW-6P. The
<br /> groundwater elevations ranged from-34.26-feet below mean sea level(MSL) in MW-3P to
<br /> -35.06-feet MSL in MW-1. Groundwater elevation measurements indicate groundwater was
<br /> flowing to the southeast at a hydraulic gradient of approximately 0.0007-foot/foot. Groundwater
<br /> elevations are shown on Figure 4.
<br /> A review of the historical field data suggests that the groundwater generally flows between
<br /> southeast and northeast. Historical groundwater elevation data can be found in Appendix C, it
<br /> includes data before 1999.
<br /> 3.2 Groundwater Analytical Results
<br /> For January 8, 2002, all petroleum compounds were non-detect (ND) at the method detection
<br /> r, limit in MW-4P, MW-5P, and MW-6P. TPH G was reported in monitoring wells MW-1P,
<br /> MW-2P,NW-3P, MW-1 and MW-2 at 70 micrograms per liter (pg/1), 1,300 Yg/l, 1,200 ugll,
<br /> 270µg/1 and 76 ggll, respectively. Benzene was detected in MW-2P and MW-1 at 49,ug/l and
<br /> 0.77,ug11, respectively. Toluene was reported in MW-1P,MW-2P and MW-31? at 1.6µg11, 13
<br /> gg/1 and 9.6 4g/l,respectively. Ethylbenzene was reported in MW-2P and MW-3P at 0.87µg11
<br /> and 1.014g/l,respectively. Xylenes were reported in MW-2P and MW-3P at 4.3 Ag/i and 8.0
<br /> ,ugll,respectively. Using EPA Method 8020,MTBE was reported in MW-2P, MW-3P, and
<br /> MW-1 at 100 gg/l,32,ugll, and 27 gg/l, respectively.
<br /> Using EPA Method 8260B, MTBE was reported in MW-1,MW-1P,MW-2, MW-2P and MW-
<br /> 3P at 18 jug/l, 0.65 1.zg11, 0.62/-zgll, 76 ug/1 and 26 gg/l, respectively. DIPE was reported in MW-
<br /> 1P and MW-5P at 19µg/1 and 77µg/1,respectively. TBA was reported in MW-2P at 93 ugll.
<br /> All other oxygenates were ND at the method detection limit for this sampling event. 1,2-DCA
<br /> was reported in MW-1P,MW-2P and MW-5P at concentrations of 11 µg11, 5.1 µg/l, and
<br /> 5.2µg/1,respectively. The groundwater analytical results for this sampling event are summarized
<br /> in Tables 2 and 3, and shown on Figures 5 and 6. Copies of laboratory reports with COC
<br /> documentation are included in Appendix B. Appendix D provides historical groundwater
<br /> analytical data from before 1999.
<br /> 4.0 SCHEDULE
<br /> The second quarter sampling event for 2002 will be conducted in April 2002 and the monitoring
<br /> report will be submitted within 30 days after receipt of the analytical test results.
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