9 First American Way - Soils Report

Home Browse Search

Lutzky Associates Development, LP - Geotechnical Investigation MACTEC Project 4953-03-2631 September 18.2003 Dispersion in the ground motion attenuation relationships was considered by inclusion of the standard deviation of the ground motion data in the attenuation relationships used in the PSHA. For the fault rupture length versus magnitude relationship, we have used the relationship of Wells and Coppersmith (1994) for all the faults in the model. The estimated peak ground acceleration for the DBE and the UBE is 0.39g and 0.47g, fe#pectively.' 5.7 CONCLUSIONS Based on the available geologic data, active or potentially active faults with the potential for surface fault rupture are not known to be located beneath or projecting toward the site. In our opinion, the potential for surface rupture at the site due to fault plane displacement propagating to the ground surface during the design li fe of the project is considered low. Although the site could be subjected to strong ground shaking in the event of an.earthquake, this hazard is common in Southern Cali fornia and the effects of ground shaking can be mitigated by proper engineering design and construction in conformance with current building codes and engineering practices. The medium dense sand layers beneath the site, have the potential to liquefy during a DBE event. The liquefaction induced settlement is expected to be on the order of !/2 to % inch. The site is relatively level and the absence of nearby slopes precludes slope stability hazards. The potential for other geologic hazards such as tsunamis, inundation, seiches, flooding, and subsidence affecting the site is considered low. 6.0 RECOMMENDATIONS 6.1 GENERAL Based on the proposed elevation for the foundation of the Data Center and the information obtained from the borings, the existing fill soils will be removed as part of the proposed construction. However, if existing fill soils are encountered at the foundation levels, the existing fill soils should be excavated and replaced with properly compacted fill soils. 15