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_ z,• File No.2070.2 19 Decembet 1991 y Fags 3 to the Constant migration of streams common to fluvial environments, the deposits tend to be laterally and vertically discontinuous. Grain sizes within alluvial deposits can range from gay-sized particles (c,.•0.74 mm) to gravel (>4.75 mm). The coarser grain sizes, which represent ancient stream cbanm-ls, occur as lenses. Generally, only these lenses of coarse-grained sediments are permeable enough to yield adequate water quantities for wells. 2.0 D£SCRIMON OF M-.D WORK 2.1 Site Specific Health and Safety Plan Prior to the commencement of work on this project, a site specific health and safety plan was prepared in accordance with the Occupational Safety and Health Administration (OSHA) "Hazardous Waste Operations and Emergency Response" (29 CFR 1910.120)guidelines. The health and safety plan designated potential hazards to watch for while performing onsite investigations and noted emergency phone numbers and directions to the nearest hospital: Also included was a discussion of required safety equipment to be worn during onsite investigations and proper emergency response protocol. A copy of the health and safety plan is included as Appendix H. 2.2 Advancement of Soil Borings _�. On 14 February 1990,ACG advanced two soil borings (Boring 90-1 and Boring 90-2) in the vicinity of the 1987 tank excavations. The soil borings were performed at the request of Mr. Gordon Boggs of the RWQCB in an attempt to better interpret soi! stratigraphy and extent of potential contamination within the vicinity of the tank cluster (stye Figure 2). The borings were performed utilizing a five foot continuous core sampling device, thits allowing more accurate sub3urface soil -• conditions to be determined. Subsurface soil conditions were logged by an onsite geologist during o, advancement of both borings (see Appendix III for boring logs). In addition to the five foot cores, relatively undisturbed soil samples were obtained at five feet vertical intervals as well as at hor,',zons of noticeable lithologic changes. All soil samples were field- screened using a handheld photo-ionization detector, properly containerized and stored on ice. At -. lest two samples from each boring, most notably those samples which exhibited the highest readings on the handheld photo-ionization detector, were transported to a State of California certified analytical laboratory. At lite laboratory, the soil samples were analyzed for the presence of total petroleum hydrocarbons (EPA method 8015 modified), aromatic volatile organics (EPA method 8020) and organic lead (method DOHS). Soil cuttings derived from tie advancement of the soil borings were containerized in 55-gallon drums. The drums were stored on the site pending analyses determining whether soil cow3mination was detected. 2.3 Installation of Monitoring Wells On 27 January 1988,ACG installed on the subject property monitoring wells 4 and 5 (AIW-4 and MW-5; see Figure 2 for locations and Appendix IV for well permits). Both wells were advanced to a depth of 53 feet utilizing hollow stem, flighted augers driven by a truck-mounted drill rig. Subsurface soil conditions were logged by an onsite geologist during advancement of the well ANDERSON CONSULTING GROUP s �fdl ;a �