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3.0 SUBSURFACE INVESTIGATION 3.1 SOIL i 1 The borings were drilled using an 8 -inch outer diameter, hollow -stem auger to depths between 20.5 and 50.5 feet below existing ground surface, at the locations shown on Figure 3. The rationale for placement of the borings was to locate at least one boring in the vicinity of each of the proposed structures with additional borings located for addressing environmental concerns. A SECOR staff engineer was onsite to observe field operations, log subsurface soil conditions, and to collect soil samples for physical and chemical analysis. Drive samples were obtained from the borings by driving a 2.5 -inch inside diameter split -spoon sampler or 1.4 -inch inside diameter Stand and Penetrometer (SPT) sampler with a 140 -pound hammer, free -falling 30 inches. The sampler was advanced 18 inches at each sample interval and the blow counts required to advance the sampler each 6 -inch drive length were recorded on the boring logs. The blow counts are used in the evaluation of the consistency of the soils and are correlated to various engineering properties. The boring cavities were backfilled with a neat cement grout. Generalized logs of the interpreted soil profile at each boring location based upon observations of auger cuttings and material retained in the samples are presented in Appendix A. At the request of ARCO, borings MW -1, MW -2, MW -3 and MW -4 were converted to groundwater monitoring wells. The wells were constructed by inserting the two-inch diameter Schedule 40 PVC casing through the annulus of the auger and then tremming the filter sand (Monterey, #2/12) through the auger annulus while slowly retracting the auger. The filter sand was placed to approximately 2 feet above the top of the 0.01 -inch slotted screen, at which point the well was sealed with hydrated bentonite chips. Each well was protected with a cap and a traffic -rated well cover box. The wells were screened in the interval of approximately 7 to 22 feet bgs. The boring logs, including well construction details, are presented in Appendix A. The following laboratory tests were performed on samples collected at the subject site by Converse Consultants, Redlands, California, in accordance with the American Society for Testing and Materials, or contemporary practices of the soil engineering profession. Direct Shear Test (ASTM D3080): The shear test was performed using a direct shear machine on an undisturbed sample. The sample was sheared in a single horizontal configuration at a constant strain rate. Normal loads were applied vertically, and the ultimate soil shear strength was determined at this load. Normal load was varied in order to evaluate the internal friction angle and cohesion. The sample was tested at near saturated moisture condition. JN 40007-095-01 ft\rnsw\97-06jun\atr *0.doc 3-1