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• Notes to Table 5 1 Elevations are based on temporary benchmark that has an elevation of 25 99 ft The benchmark is a center- punched bold in a light base about 22 ft east of the centerline of the railroad tracks which cross West Yosemite Avenue Benchmarks of record within one mile of site were found demolished 2 TOC=Top of casing Elevations of top of road boxes are 25 52 for MW-1,25 43 for MW-2 and 25 66 for MW-3 RESULTS—CHEMICAL ANALYSES The results of the chemical analyses of the groundwater samples collected on March 19, 1999 from the three monitoring wells on the site, MW-1,MW-2 and MW-3 (see Table 6 below), are consistent with, and confirm those of the samples collected from the same wells August 24, 1998 That is, the concentrations of TPH-D, benzene, ethylbenzene, toluene, xylenes, MTBE and Total Lead are all below the analytical method detection limits for the samples from all three wells Table 6. Petroleum hydrocarbon parameter concentrations in groundwater samples from monitoring wells MW-1 through MW-3, collected March 19, 1999. Monitoring TPH-D Benzene Ethylbenzene Toluene Xylenes MTBE Total Lead Well No (pg/1) (pg/1) Gig/l) (µg/1) (11g/1) (110) (m1/4 MW-1 < < < < < < < MW-2 < < < < < < < MW-3 < < < < < < < Method 50 0 5 0 5 0 5 05 0 5 0 1 Detection Limit • RECOMMENDATIONS CAL INC recommends that ABF Freight Systems, Inc apply to the San Joaquin County Public Health Services Environmental Health Division for closure of their underground storage removal stte at 2427 West Yosemite Avenue, Manteca, California The recommendation is based on the fact that analyses of two sets of groundwater samples collected 7 months apart from the three monitoring wells at the site failed to detect any concentrations of the petroleum hydrocarbon parameters analyzed This suggests that the diesel fuel contamination detected in the soil removed from the UST excavation was very localized and did not reach the groundwater table --tV4+J 5,3 8f"^ Jnr 3 j li 117,r�.►�� Well Destruction Plan CAL INC also recommends that ABF Freight Systems apply to the County of San Joaquin Environmental Health Division for a permit for the destruction of the three monitoring wells The purpose of the well destruction is to ensure that the quality of the groundwater is protected Destruction of the well eliminates the pathway that any surface contamination could potentially follow between the surface and the groundwater table The following well destruction plan is recommended It is based on the requirements in Bulletin 74-81, "Water Well Standards State of California", by the Department of Water Resources, December 1981, and its supplement, Bulletin 74-90, "California Well Standards" by the California Department of Water Resource, June 1991 The well destruction will be accomplished by filling and sealing them by pressure grouting The well destruction plan includes the following tasks . • Sounding the wells just before destruction to insure there are no obstructions in the well casings that will interfere with filling and sealing Any obstructions will be removed