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1 SOIL VAPOR EXTRACTION PILOT STUDY REPORT San Joaquin County Montgomery Ward Auto Service Center Public Health Services Deparnnent 5400 Pacific Avenue,Stockton CA Site Code 2163 t Product Lines ' In June 1986, after the gasoline USTs were removed, the underground piping associated with the USTs was rinsed, stubbed back, capped and left in place pursuant to approval from the SJCPHSD ' On September 12 and 13, 1991, 12 slant borings were hand augered to depths of approximately four feet bgs Soil samples PL-1 to PL-12 were collected along the product ' lines which extend between the former fuel islands and the former USTs locations (see Figure 2) No detectable concentrations of TPH were present in any soil samples tested, except for soil sample PL-7 (see Table 3) TPH (844 ppm), toluene (0 95 ppm) ethylbenzene (0 65 ppm) and xylenes (9 55 ppm) were detected in soil sample PL-7 @ 4-4 5' (see EAI, 1991A) ' PHASE IV INVESTIGATION (1992) ' In July 1992, EAI drilled and sampled four additional borings (borings B-7 through B-10) Barings B-7 and B-8 were located in the vicinity of the sewer line and former gasoline USTs, and borings B-9 and B-10 at the former fuel islands (see Figure 2) ' No TPH-G were detected in the samples collected from boring B-8 (see Table 4) Only one sample from boring B-7 (B-7 @ 5') contained a TPH-G concentration (43 ppm), and only one sample from boring B-10 (B-10 @ 5') contained a detectable concentration of TPH-G (8 ppm) TPH-G concentrations encountered in boring B-9 ranged from 1,220 to 3,490 ppm The total lead concentrations detected in samples collected from these four borings ranged from 5 72 to 13 4 ppm (see Table 4 and EAI, 1992) Further, selected soil samples also were analyzed for carbon chain breakdown (see Table 4) PHASE V INVESTIGATION (1993) In February 1993, three borings (borings B-11, MW-1 and MW-2) were drilled on the Montgomery Ward site Two of the borings (borings MW-1 and MW-2) were converted into ground water monitoring wells MW-1 and MW-2 (see Figure 2) The analytical testing results of the soil samples obtained from borings drilled as part of this investigation show that TPH-G concentrations ranging from 6 9 to 3,110 ppm were encountered The highest concentrations of TPH-G were detected in samples collected from boring location MW-2 at depths ranging between 20 and 60 feet bgs (see Table 5) Elevated hydrocarbon concentrations also were detected in the samples collected from boring B-11 between 40 and 50 feet bgs TPH-G were detected only in one sample (MW-1 @ 45 feet) collected from boring MW-1 BTEX were detected in many samples Several chlorinated ■ 1:ydrvCarb11VL aJJV�rl(ALed n1Lh 6U0 JL le also were deLC Ll.d aL a-JLl.VL4-U DaIL1il1C. 1VLdL1U11.7, e g , tetrachloroethene (PCE), trichloroethane (TCE), and 1,1,1-trichloroethane (1,1,1-TCA) (see Table 5) The source of these chlorinated hydrocarbons is unknown (see EAI, 1993) PHASE VI INVESTIGATION (1995) In January 1995, four ground water monitoring wells (MW-3 through MW-6) were drilled, installed, and sampled (see Figure 2) TPH-G and BTEX were identified in borings MW-3 and MW-4 near the top of the water table, at depths ranging from 45 to 50 feet bgs (see Table 6) TPH-G ranged in concentration from 72 to 670 ppm and BTEX ranged in concentration IProject No 1232 A-3 ENVIRONMENTAL AUDIT, INC e