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PHASE VII SUBSURFACE INVESTIGATION San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue Stockton CA Site Code 2163 2.3 GASOLINE USTS ' On June 26, 1986, two 10,000-gallon capacity gasoline USTs were removed from the Montgomery Ward site (see Figure 2) The USTs were used to store regular and unleaded gasoline A representative of the County was reportedly on-site during USTs removal ' activities The underground product lines were triple rinsed, stubbed and abandoned in place A concrete slab on which the USTs were located was also abandoned in place The following summarizes the investigation activities completed to date at the Montgomery Ward site ' 2.3.1 Phase I Investigation In May 1988, A D Selditch & Associates, Inc (ADS) drilled and sampled five borings on the Montgomery Ward site to determine whether any release had occurred in the former vicinity of the gasoline USTs (see Figure 2) Four of the borings (borings 1 through 4) were located in the former area of the gasoline USTs, and one boring (boring 5) was located in the ' west corner of the Montgomery Ward site to determine background soil conditions Borings 1 and 2, located at the southwest and southeast corners of the USTs, respectively, were drilled to a depth of 20 feet below ground surface (bgs) Borings 3 and 4 encountered auger refusal at 12 feet bgs, i e , the slab on which the USTs had been located was apparently encountered Detectable concentrations of TPH ranging from 8 to 38 ppm were encountered in only three of the samples tested (see Table 1) The detectable concentrations were all present in soil 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) 2.3.2 Phase 11 Investigation In March 1991, EAI drilled and sampled two borings (borings B-5 and B-6) at the I Montgomery Ward site to determine whether operation of the former gasoline USTs impacted the environment (see Figure 2) Barings 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) _ A Phaco ITT Tntractirratinn �.�../ A lA[11V JI..AA ;}i.y.}4��uFaV•a 2 3 3 1 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 Project No 1232 - 2 - ENVIRONMENTAL AUDIT, INC eD