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Geotechnical Engineering and Geological Hazard Study Lincoln Elementary School I'v4odernization Project Manteca, California Page 9 they have already experienced settlemnent during historic earthquakes. The potential for liquefaction as a result of ground shaking is possible but low, while the potential for dynamic settlement is moderate. Results of the liquefaction analyses are presented in Appendix B. The settlement analyses suggest that surface ground settlements resulting from liquefaction of the susceptible deposits would average less than 1 inch with a maximum estimated settlement of about 2 inches (at BS). Differential settlements across a typical building footprint due to liquefaction are estimated to range from 0.5 to 1 inch. 6.2.1 Potential Seismically Lateral Spreading Although methods have been proposed for estimating the magnitude of lateral spreading (Bartlett and Youd, 1995), results from such analyses are not valid if the zone of liquefaction is discontinuous or the liquefied layers are not exposed along a free surface. The site is located on a flat alluvial plain, with no free surface in the vicinity. Therefore, due to the absence of a free surface and the discontinuous lateral extent of the potentially liquefiable deposits, the potential for lateral spreading is considered negligible in the event of a maior earthquake. 6.2.2 Seismic Design Considerations A variety of methods are commonly used to mitigate the threat of structural damage posed by potentially liquefiable deposits, including: • Supporting structures on deep driven piles or drilled shaft foundations that derive support from the soils below the depth of potentially liquefiable layers. • Using ground improvement methods such as excavation of liquefiable deposits, dynamic deep compaction, stone columns, or grouting. • Supporting structures on engineered fill supporting shallow foundations, slabs, or mats designed to accommodate the predicted ground deformation. Deep foundations may be appropriate for specific situations where particularly heavy building loads occur or where control of settlement is critical (i.e. bridges); however, for conventional lightly loaded structures, this foundation system is relatively costly. We consider engineered fill supporting shallow foundations, slabs, or mats to be the most appropriate means of foundation support for lightly loaded structures and small amount of settlement. The predicted seismically -induced ground deformation is not substantially greater than can be accommodated by typical construction. 7.0 CONCLUSIONS AND RECOMMENDATIONS 7.1 GENERAL Based on our findings, it is our professional opinion that the site should be suitable from a geotechnical standpoint for construction of the proposed Lincoln Elementary School Modernization Project provided the geotechnical recommendations contained herein are incorporated into the project design. Given the site conditions encountered, we conclude that engineered fill supporting shallow foundations, slabs, or mats should provide adequate support for the anticipated structural loading. The primary geotechnical consideration from a development standpoint is: M