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' SOIL VAPOR EXTRACTION PILOT STOWORK PLAN � San oaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue, Stockton, CA Site Code 2163 samples obtained from borings 3 and 4 Total lead concentrations ranging from 6 to 36 ppm were present in all of the samples tested (see ADS, 1988) ' PHASE II INVESTIGATION (1991) ' In March 1991, Environmental Audit, Inc (EAI) drilled and sampled two borings (borings 13- 5 and B-6) at the Montgomery Ward site to determine whether operation of the former gasoline USTs impacted the environment (see Figure 2) Borings B-5 and B-6 were terminated at a depth of approximately 31 5 and 51 5 feet bgs, respectively Ground water was not ' encountered during drilling No total petroleum hydrocarbons as gasoline (TPH-G), benzene, xylenes or ethylbenzene were detected in any of the samples collected from boring B-5 (see Table 2) Toluene (ranging from 0 01 to 0 14 ppm) was the only aromatic hydrocarbon ' encountered in the samples obtained from boring B-5 Elevated concentrations of TPH-G, toluene, xylenes, and ethylbenzene were detected in seven of the ten samples obtained at depths from six to 50 feet bgs in boring B-6 (see Table 2) A solvent odor was noted during drilling of boring B-6 No organic lead was detected in any of the samples tested, and the ' TPH-G concentration in the sample collected at 50 feet bgs was 7 3 ppm The concentrations of total and organic lead detected were well below the standards contained in Title 22, California Code of Regulations (see EAI, 1991) PHASE III INVESTIGATION (1991) Sewer Line Montgomery Ward suspected that a broken sewer line may be the source of contamination in boring B-6 On June 9, 1991, Pacific Pipeline Survey (PPS) was retained by Montgomery ' Ward to investigate the existence of a possible break in the sanitary sewer manhole, associated piping, and a clarifier which are located in close proximity to the former location of the gasoline USTs According to this investigation, about one foot of the sewer line was broken ' On September 12, 1991, representatives of Stone Brothers excavated a trench around the suspected broken sewer line to an approximate depth of 2 5 feet bgs (see Figure 2) Two slant ' borings were drilled around the sewer line using a hand auger Commencing near the base of the clay pipe (2 5 feet bgs), slant boring SB-1 was hand angered to a calculated vertical depth of 5 75 feet bgs Two soil samples (SS-1 and SS-2) were collected from slant boring SB-1 at a depth of 3 5 and 5 5 bgs, respectively Slant boring SB-2 was hand augered to an estimated ' depth of 4 75 feet bgs in the sidewall of the excavation and a soil sample (SS-3) was collected at the termination depth The boring was terminated approximately beneath a second sewer line that extends west of the manhole 1 NT- 'I't)" iwr vo riatartari in nn�r Of the three Snil QnmT*)1PS agcnrintPd with the Sewer line �¢PP 11 V A 1 11 11—V �.F I�-l- \--- Table 3) However, minor concentrations of BTEX, bromoform, carbon disulfide, chloroform, tetrachloroethene, trichloroethene, 1,1,2,2-tetrachloroethane, 1,1,1- ' trichloroethane and 1,1,2-trichloroethane were detected in the soil samples tested (see Table 3 and EAI, 1991A) ' Project No 1232 A-2 ENVIRONMENTAL AUDIT, INC