15 ATTACHMENT 9 - Laserfiche WebLink

Project No. 9929.G Geotechnical Investigation/Vineyard Avenue, Pleasanton 8 August 2003 Since the property is situated on a hillside, some of the steeper portions of the site may be susceptible to landsliding during a strong seismic event in conjunction with a high rainfall event. However, the site is not susceptible to liquefaction, differential compaction and/or ground lurching due to the nature of the subsurface materials. The site will experience strong ground shaking if a large earthquake occurs along the Verona, Calaveras and/or Greenville Faults. The secondary hazards of tsunamis or seiches are unlikely. UBC Earthquake Design Criteria The 1997 Uniform Building Code (IJBC) Chapter 16, Division IV Earthquake Design requires that structures be designed using certain earthquake design criteria. The criteria are based in part on the seismic zone, soil profile and the proximity of the site to active seismic sources (faults). During an earthquake event, structures located very close to active faults can be subjected to near source energy motions that may be damaging to structures, if the effects of these energy motions are not considered in the structural design. The UBC indicates that the types of seismic sources (active faults) that generate near source (Na and N,,) greater than 1.0 are classified as Type A or Type B. The nearest Type A or Type B active fault to the site is the Calaveras Fault, which is located approximately 7 km west of the subject site and is categorized as a Type A fault. Based on the geotechnical data in the referenced report and the selection of criteria of the 1997 UBC, Chapter 16, Division IV, Earthquake Design, a summary of the earthquake design criteria for use in the design of the proposed structures is as follows: Seismic Zone = 4 Soil Profile Type = SD Near Source Factor Na = 1.12 Near Source Factor N~ = 1.44 Subsurface Conditions The subsurface conditions as encountered in the four borings were found to be fairly consistent across the site and generally consisted of a surface layer of silt up to 2 feet in thickness overlying TERRASEARC$ inc Page 10 of 53