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Project 113-26-04, 05, Page 7 November 17,1995 Undisturbed soil samples were procured at five foot intervals during monitoring well drilling. Brass sampler liners were cleaned with a TSP solution and rinsed in tap water prior to insertion into the sampler, a California modified split barrel The sampler was then inserted through the augers to the boring bottom The sampler was advanced by successive blows from a 140 pound hammer utilizing about a 30 inch drop BIow counts per six inch interval were recorded when using the 140# hammer The sampler was extracted from the boring and the liners removed The samples were utilized for logging of soil characteristics, and possibly selected for chemical analysis Only completely full sampler liners representing the lower foot of the sampled interval were selected for analysis At the soil boring locations a small slide hammer with a sampling shoe containing a single brass sample tube was used to obtain undisturbed samples Sample retention within the sample tube was about 75% at most locations Selected soil samples were sealed at each end with teflon sheets or aluminum foil and plastic caps The samples were then labeled and placed into a cooler with ice and chain of custody documentation and procedures were initiated (Appendix B Sampling Documentation) At the lab, the selected soil samples were analyzed for TPH as gasoline and BTEX It was apparent during drilling and sampling that gasoline contaminated soil was present beneath much of the investigated area between about 5 5 and 7 feet depth BGS, which likely represents the capillary fringe of the water bearing zone and/or the highest seasonal groundwater level The exceptions were all of the down gradient data points B-14, MW-6, MW-7, and B-20 (B-20 may be cross gradient to off site plume axis), as well as the cross gradient point B-21 Petroleum odors and soil discoloration were not noted during drilling and soil and groundwater samples from these locations did not appear to contain gasoline Site Geology Soils encountered during drilling were continuously logged by a geologist using the Unified Soil Classification System (USCS)(Appendix C Boring & Well Completion Logs) The monitor well drilling and installation was performed under the supervision of a State Certified Engineering Geologist The soils encountered during drilling were found to be similar at the eighteen locations Each location had asphalt or concrete at the surface From beneath the pavement down to about 1 foot depth was base rock or sand fill. Beneath that the native soil consisted primarily of silty clay or clayey silt, (CL) which was olive brown to light yellowish brown, silty 20-30%, sandy very fine grained <10%, damp, and stiff Between about 5.5 and 7 feet depth BGS, the soil was silty sand, (SM, ML), colored light yellowish brown to brown-olive brown Where impacted by gasoline these soils were green-gray to blue-gray These sands were generally very fine to fine grained, and contained up to 30-40% silt CIay was minor within these soils First Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 Phone (510) 439-1024 Fax (510) 439-2566