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Mr Kyle Christie Project 0805-146 03 January 24, 1996 Page 4 benzene concentrations ranged from 2,100 ppb in well MW-7 to 10,000 ppb in well MW-3 TOG was detected in well MW-2 at a concentration of 7,200 ppb, and in well MW-6 (located off site and upgradient) at a concentration of 29,000 ppb (see Table 2) Concentrations of TPHG and benzene are shown on Figure 2 ACTIVITIES PERFORMED DURING THE FOURTH QUARTER • EMCON performed quarterly groundwater sampling • EMCON compiled and evaluated groundwater monitoring data • EMCON finalized and submitted the "interim Soil. Remediation Plan" associated with removal of the underground storage tanks to the appropriate regulatory agencies ANTICIPATED WORK i' o ARCO will continue to perform quarterly groundwater monitoring. The next sampling event is tentatively scheduled for February 1996 o EMCON will collect groundwater samples that will be analyzed for TPHG, BTEX, and HVOCs In addition, samples collected from wells MW-2 and MW-6 will be analyzed for TOG CONCLUSIONS The direction of groundwater flow during the November 1995 sampling event was toward the northeast and southeast, which is generally consistent with previous sampling events Dissolved gasoline hydrocarbons were detected in samples collected from all wells TOG was detected in the samples collected from wells MW-2 and MW-6 No other samples were analyzed for TOG The highest concentration of dissolved hydrocarbons continues to be present in the upgradient and off-site monitoring well, MW-6 HVOC analyses will be performed on a semiannual basis (during the first and third quarters of each year). Because wells MW-2 and MW-5 are located within the dissolved hydrocarbon plume and other nearby monitoring wells provide lateral definition, EMCON recommends these wells be sampled on a semiannual basis SAON\PJ"80"80514b03Ds-95�pu i