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Wahlnu 6r&ve gevacr• Proje ct: fiooster Rr!isrt :;C-fsni, Raiy�:. i' Crux Rcojed: Nundi7r: LFC-O'lII:t. May Ve" 2007 liquefaction, as determined by the methods used. The state of the art in predicting liquefaction induced settlement is limited. Estimates of settlement are generally expected to vary on the order of a factor of 2. Our calculations of settlement due to liquefaction are based on the method described by Tokimatsu and Seed 6, the most commonly used method. The results of our analysis indicate that the site could experience differential settlement on the order of 11/2 to 51/2 inches. The amount of surface manifestation may be less due to the clay soils overlying the potentially liquefiable sands, Since the wet wells will extend in the upper medium dense sandy soils beneath the clay soils and the potentially liquefiable soils are below a depth of about 30 feet, In our opinion it is possible that the pump station will Incur significant settlement if liquefaction of the deeper sand soils does occur due to the proximity of the wet well foundations to the potentially liquefiable soils. Consequently, we recommend that flexible connections should be used for all pipelines to structure connections. Please note that these calculations are applicable only to the soils encountered in our borings• Liquefaction may potentially occur in soils below those encountered in our investigation; if deeper soils do liquefy, the potential for settlement of the site may ncrease. Due to the relatively flat nature of the site and the lack of a free face,. severe lateral spreading is not expected. However, ground oscillation and limited" lateral displacements may still occur. From a soil engineering standpoint, ow' oiflce concludes that the site is suitable for construction of the proposed sewer project. booster pump station; however, all of the conclusions and recommendations presented in this report should be incorporated into the design and construction to help reduce the potential for soil and foundation problems. GaS Grading The site should be initially cleared of all vegetation, trees, roots, debris, and deleterious material as outlined in Appendix A, Engineered Fill Specifications. Areas that are covered with light vegetation consisting of native weeds and grasses may be blended s TokimaLsu, l; and Seed, H.B., Evaluation of Sett/emenLs in Sands due to Earthqua/ce Sha/ring, Journal of Geotec/mica/Engineering, Vo% 1i3, No. �4 August, 1987 r'1 NEIL. O. ANDERSON 4 AND ASSOCIATES 901 Inianial Vni m odf. CA 95_dP ©2007 Nei( 0. Anderson & Assocides. Inc.