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C r �? File No. A7-1909-J1 November 3, 1987 F A limited laboratory testing program was conducted for this preliminary investigation. The testing program consisted of obtaining moisture/density, IJj plasticity index, and grain size distribut on values from the collected soil samples. See Appendix B and the Logs of the Test Borings for a compilation of those laboratory test results. Results r : The site is level and is currently being utilized for agricultural usages. The site had been recently tilled, at the Vme of the field drilling program. A canal presently exists along the northwest boundry of the subject site. This canal is approximately 20 feet wide, 0 feet deep, and unlined. The canal appears to be related to agricultura use. There also is a small grove of trees at the southeast corner of the si e. �-J The following is a description of the near surface soil conditions, as observed by- .the project Soil Engineer during the field drilling operations. The surface soil consists of native soil which is composed of clayey silt with minor fine sand. This silt layer was approximately six inches thick in test boring nos. 1 and 2, the west and center ol the site, and approximately four feet thick in test boring no. 3, the east fortion of the site. This silt surface layer is generally dry and loose tc six inches, then very damp and medium dense. The silt layer exhibits a moderate shrink-swell (expansive) potential when .subjected to fluctuations ir water content. Underlying the a surface silt layer is a dark grey silty cly layer. This silty clay layer is four feet thick at the locations of test b ring nos. 1 and 2, the west and center of the site. The clay layer was no encountered in test boring no. 3, the -east portion of the site. This clay 1 yer is generally slightly moist, very stiff, and exhibits a high shr nk-swell (expansive) potential . Underlying the above described surface and near surface soils are additional f] silty clays, sandy clays, clayey silts, anc silty sands. These soils are generally very moist and very stiff or medium dense to loose. Free ground 'J water was encountered in each of the test torings. The water was encountered at depths of 9, 10, and 10 feet and subsequently rose to 6, 6, and 8 feet ! below the surface. An approximately 12—inch thick lajye_r of potentially liquefiable sand was encountered in test boring no. 1. No W6 sand layers were encountered in the other two test borings. However, it appears, from the limited data obtained during this investigation, that the sand layers underlying the ( ; subject site are sparce and disconnected. It is our opinion, therefore, that the potential for liquefaction at the site is low to moderate. i Site Geology Geologic Setting: The site is on the western edge of the San Joaquin Valley. ; (''i The valley has been filled by alluvial deposits derived from the bordering mountain ranges and deposited on the valle3 floor by streams flowing from the mountains across the valley. The valley fill is a result of the coalescence of numerous alluvial fans, cone-shaped stream deposits, and over-bank and flood plan deposits of the various streams which flow into and through the valley. These deposits are irregularly interbedded and consist of 3ppie Saii illicca�lcs