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Sod Excavation and Second Quarter Post-Treatment Mondonng and Sampling Report 6 . The Southland Corporation,Store#20.304,455 Grant Line Road,Tracy,CA _---- June 9,1998 4 4 Soil Sample Analytical Results Table 1 summarizes the laboratory analytical results for soil sample collected on May 8, 1998 BTEX, TPH-G, and MTBE were not detected in the sample collected during the Installation of well MW-16 Copies of the analytical results and chain-of-custody documents are Included In Appendix D 5 0 QUARTERLY GROUNDWATER MONITORING AND SAMPLING The second quarter monitoring and sampling event was conducted at the site on May 15, 1998 Activities conducted are summarized below ■ Depth to water(DTW) was gauged In nine groundwater monitoring wells and two groundwater extraction wells(Figure 2) ■ Groundwater samples were collected from three wells MW-4, MW-5, and newly installed well MWA 6, and submitted to a certified laboratory for analysis for BTEX,TPH-G, and the oxygenates, MTBE,TBA, DIPE, ETRE, and TAME 51 Groundwater Monitoring Data Groundwater monitoring was performed on May 15, 1998 Prior to monitoring,the well caps were opened to allow the water level in each well to stabilize to atmospheric pressure The DTW was measured to the nearest 0 01 foot from the top of the well casing using an ORS Environmental Equipment INTERFACE PROBE Well Monitoring System Separate-phase(SP) hydrocarbons were not detected In any of the monitoring wells The water table elevations,calculated from the May 15, 1998 monitoring data,were used to prepare a potenttometric surface map (Figure 2) The groundwater flow is generally toward the north-northeast at a hydraulic gradient of 0 003 ftfft Groundwater monitoring results from the May 15, 1998 monitoring and sampling event are presented In Table 2, and historical results are summarized in Table 2A Field data sheets are Included in Appendix B Prior to purging,dissolved oxygen levels were recorded in each well using afield Instrument Dissolved oxygen data taken from nine monitoring wells and two extraction wells on May 15, 1998 Indicate depletion of oxygen through intrinsic biodegradation in wells GWE-1, GWE-2,MW 1 and MW-16 Dissolved oxygen levels ranged from 1 0 milligrams per Ider(mg/L)in well GWE-1 to 5 8 mg/L In well MW-4 Generally, In the center of the plume and near the downgradient edge of the plume,dissolved oxygen levels are low, indicating oxygen depletion Dissolved oxygen data collected on May 15, 1998 are presented In Table 2 i FLUOR DANIEL GTI zaoo"xrpi