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CLEAR�ATER G R o U P I N C Enr irnnrn rn�rl $rr rocs 5.4 Groundwater Analytical Results TPHg and BTEX were detected in concentrations exceeding method detection limits in groundwater samples collected from monitoring wells MW-1, MW-3, MW-5B, MW-6 MW-7 and MW-8 sampled on March 9, 2000 TPHg and benzene were also detected in concentrations exceeding method detection limits in groundwater samples collected from soil boring SB-9 sampled on March 8, 2000 Concentrations of analytes were highest in MW-5B, which is assessed as downgradient of the former UST pit Concentrations of TPHg and benzene in MW- 5B were 9,700 µgl and 460 µg/L, respectively MTBE was not detected by EPA method 8260 in any of the groundwater samples analyzed Dissolved hydrocarbon concentrations are summarized in Table 2 and are shown on Figure 6 The certified laboratory analytical report is presented with the chain of custody in Appendix D 6.0 SUMMARY AND CONCLUSIONS During well installation activities at the project site, petroleum hydrocarbons were detected in samples collected in both the soil and groundwater beneath the property and in groundwater on the other side of South Fresno Avenue Petroleum hydrocarbon concentrations in soil samples collected during well installation appeared to reach a maximum depth of 35 feet and its aerial extent is limited to approximately 150 feet downgradient of the former USTs During this quarter, groundwater was observed on site from a depth of 4 71 to 9 41 bgs Based on historical data of monitoring MW-1 through MW-6, groundwater levels appear to reach a low in September, and a high in March Water levels within each of these wells fluctuate annually from 5 to 6 feet Groundwater gradient, as in past quarters, appears to be toward the southeast approximately at 0 016 ft/ft Extent of Hydrocarbons in Soil Previous subsurface investigation have delineated the vertical extent of sorbed-phase hydrocarbons as being restricted to approximately 10 to 25 feet bgs depth interval Results from this phase of investigation have confirmed delineation of the extent of the sorbed- phase hydrocarbon plume in the saturated zone at a depth of 35 feet bgs in MW-5B, to the southeast of the: former USTs Soil samples collected at 5, 15, and 25 feet from MW-7 and MW-8 • ZB 178C 6 3/31/00