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HYDROGEOLfl131C ASSESSMENT RESULTS AND
<br /> QUARTERLY GROUNDWATER MONM)RING REPORT
<br /> 4445 Pershing Avenue Stockton California
<br /> 3.4 Groundwater Conditions
<br /> On January 21, 1992, Emcon personnel collected measurements of the
<br /> depths-to-groundwater in wells MW-1, MW-2, MW-3, and MW-4 Since October 1991,
<br /> groundwater levels had risen in three of the four wells, MW-1, MW-2, and MW-3
<br /> (Figure 3) Well MW-4 had only one data pont The rise ranged from 1 58 to 1 65 feet
<br /> (Table 2) On the basis of the January 21, 1992, measurements, groundwater is
<br /> estimated to flow to the northeast (Figure 4) at a gradient of approximately 0 004 ft/ft
<br /> Previous groundwater levels are summarized in Table 2 All groundwater elevation
<br /> measurements were made from the referenced wellhead elevations, measured to the
<br /> nearest 0 01 foot, and conducted according to the Emcon sampling procedures (SP)
<br /> included in Appendix B
<br /> 3.5 Water Sampling andAnalysis
<br /> On January 21, 1992 Emcon personnel collected groundwater samples from wells MW-1,
<br /> MW-2, MW-3, and MW-4 The samples were delivered under chain-of-custody to Sequoia
<br /> Analytical of Redwood City, California, a state-certified analytical laboratory, for chemical
<br /> analysis Sample collection was conducted according to the Emcon SP included in
<br /> Appendix B The samples were analyzed for concentrations of a) TPH, as gasoline, by
<br /> EPA Method 8015, b) BTEX by EPA Method 8020, c) ethylene dibromide by EPA
<br /> Method 624, and d) total lead by EPA Method 7421 In addition, one sample was
<br /> collected from MW-2 for analysis of fecal coliform by membrane filtration Concentrations
<br /> of TPH, as gasoline, were indicated at 0 110 ppm in MW-4, and below the detection limit
<br /> in MW-1, MW-2, and MW-3 The analysis indicated benzene concentrations in MW-4 of
<br /> 0 0012 ppm, and below the detection limit in MW-1, MW-2, and MW-3 The analytical
<br /> results are summarized in Table 3 The analytical reports and chain-of-custody forms are
<br /> included in Appendix C Concentrations of TPH, as gasoline, and benzene reported in
<br /> Table 3 are shown on Figure 5
<br /> 3.6 Drill Cuttings and Monitoring Well Purge Water
<br /> All drill cuttings were stored temporarilyon site, on and under plastic sheeting, pending
<br /> P 9, P 9
<br /> laboratory analysis of the sod samples collected from the stockpile Following receipt of
<br /> the laboratory results, the drill cuttings were transported, by Triangle Construction of
<br /> Sacramento, California, from the Shell site to an appropriate disposal facility
<br /> Rinsewater, development water, and purge water generated during the drilling,
<br /> development, and sampling of the wells was stored temporarily on site in DOT-approved
<br /> 55-gallon drums, pending laboratory analysis of the water samples Following receipt of
<br /> the laboratory results, the water will be transported from the Shell site to an appropriate
<br /> disposal facility
<br /> 09-016A QMR 5
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