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Work Plan for Additional Groundwater Investigation <br /> Quik Stop Market No. 132 <br /> 3555 West Hammer Lane <br /> Stockton,California <br /> The maximum benzene concentration was 3.9 mg/kg in the soil sample obtained from B-3 at a <br /> depth of 15 feet bgs. TPHg was present in the groundwater sample obtained from MW-1[320 <br /> micrograms per liter (ug/L)]. BTEX (at least one constituent) were present in the groundwater <br /> samples obtained from MW-I and MW-2. The maximum benzene concentraiion was 34 ug/L in <br /> the groundwater sample obtained from groundwater monitoring well MW-1. The locations of <br /> soil borings and groundwater monitoring wells are shown on Figure 2. <br /> Review of the site geology indicates that two separate groundwater bearing zones may exist <br /> beneath the site. The upper groundwater bearing zone appears to be present from approximately <br /> 14 to 19 feet bgs, and the lower groundwater bearing zone appears to be present from <br /> approximately 20 to 30 feet bgs. Consequently, on October 3, 1990, Exceltech abandoned <br /> groundwater monitoring well MW-1 due to the concern that this groundwater monitoring well <br /> could possibly connect the two groundwater bearing zones. <br /> On April 2, 1991, Exceltech completed an additional site assessment consisting of the installation <br /> of two additional groundwater monitoring wells (MW-IA and MW-5). The soil and <br /> groundwater samples (from new and existing groundwater monitoring wells) were analyzed for <br /> TPHg and BTEX in accordance with EPA test methods 8015 and 8020, respectively. TPHg and <br /> BTEX were not present in any of the soil borings. TPHg was present in the groundwater sample <br /> obtained from MW-5 (210 ug/L). Benzene (3.4 ug/L) and xylenes (2.1 ug/L) were present in <br /> r� groundwater sample obtained from groundwater monitoring well MW-5. <br /> f` On December 9, 1992, RESNA Industries Inc. (RESNA) completed an additional site assessment <br /> ' consisting of the installation of two additional off-site groundwater monitoring wells (MW-6 and <br /> { MW-7). The soil and groundwater samples (from new and existing groundwater monitoring <br /> E-1 wells) were analyzed for TPHg and BTEX in accordance with EPA test methods 8015 and 8020, <br /> respectively. TPHg and BTEX were not present in any of the soil borings. TPHg was present in <br /> L groundwater sample obtained from MW-5 (350 ug/L). BTEX (at least one constituent) were <br /> present in groundwater samples obtained from MW-2 and MW-5. The maximum benzene <br /> C concentration was 0.66 ug/L in the groundwater sample obtained from groundwater monitoring <br /> well MW 2. <br /> In March 1996, groundwater samples obtained from groundwater monitoring wells MW-1R, <br /> MW-2, MW-5, MW-6 and MW-7 were first analyzed for methyl tert-butyl ether (MTBE) in <br /> accordance with EPA test method 8020. MTBE was present in groundwater samples obtained <br /> from MW-1R, MW-2 and MW-5. The maximum MTBE concentration was present in <br /> groundwater sample obtained from MW-5 .(1,100 ug/L). MTBE concentrations in MW-5 <br /> subsequently decreased steadily for five quarters until September 1997 when the MTBE <br /> n concentrations rose back to 1,100 ug/L. <br /> In a letter to Quik Stop Markets Inc.; dated April 1, 1997, the San Joaquin County Public Health <br /> Services Environmental Health Division stated the that "the only remaining issue at the site is <br /> \\PLEASANTONWd.,.T.kW.mma\Q.,B.P\WOB PLAN(Gmpmbe)d« 2 <br /> l � <br />