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T� s cow ' P �7 File No.2070-2 19 Dtcctnber 1991 Pesc l to the constant migration of streams common to fluvial environments, the deposits tend to be laterally and vertically discontinuous, Grain sizes within alluvial deposits ran range from clay-sized particles (<0.74-nim) to grave% (>4.76 mm). The coarser grain sizes, which represent ancient strEam channels, occur as lenses. Generally, only uwse lenses of coarse-grained sediments are permeable enough to yield adequate water quantities f,,ir wells. 2 G DFS .RTP1T N__CjF FIELD WORK 2.1 Site Specific 11calth and Safety Plan Prior to the commencement of work on this project, a site. specific health and safety plan wa,, prepared in accordance with the Occupational Safety and Health Administration (t?SHA) "Hazardous 'Waste Operat'sons and Emergency Response" (29 CFR 1910.120)guidelines. The health and safaty plan designated potential hazards to watch. for while performing onsite investigations and noted emergency phone numbers and directions to the nearest hospital. Alsn included was a discussion of required saferp equipment to be worn during onsite investigations and proper emergency response protocol. A copy of the health and safety plan is included as Appendix II. 2.2 Advancement of Solt 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 soil stratigraphy and extent of potential contamination wita`lin the vicinity of the tank cluster (see Figure 2). The borings were performed util'17_ing a five fool continuous core sampling device, thus allowing more accurate subsurface soil conditions to be determined. Subsurface soil conditions were logged by an onsite geologist during a;idancement 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 horizons of noticeable lith6logic changes. All soil samples were field- screened using a handheld photo-ionization detector., properly cornalne:ized and stored on ice. At ieaS2 two samples from each boring, most notably those samples which exhibited the highas: readings on the handheld photo-ionization detector, were transported to a State of California certified analytical laboratory. At the laboratory, the soil samples were analyzed for the p:esence rf total petroleum hydrocarbons (EPA method 8015 modified), aromatic volatile GrgaY:ics (EPA method 8020) and organic lead (method DOHS), Soil cuttings derived from the advancement of the soil borings wen's containerized iii 55-gallon drums. The drums were stored oto the sita pending analyses determinipg whether soil conlamination was detected. 2.3 InstAlztion of Monitoring Wells On 27 Janu:ry 1988, ACG installed an the subsea property monitoring wells 4 and 5 (MW-4 and '!1V-5; see Figure 2 for locations and Appendix IV for well permits). Both wells were advanced to a depth of 53 feet utilizing hollow stern, flighted augers driven by .a truck-maunted drill rig. Subsurface soil conditions were logged by an onsite geologist during advancement of the well ANDERSON GROUP E