1710 W MARINE VIEW DR Geotech Report 2023-12-29

Based on the geophysical survey completed at the site, the project site is best characterized as a Site Class D per ASCE 7-16. We recommend the use of the following ASCE 7-16 mapped parameters for Site Class, short -period mapped MCER spectral response acceleration (SS), 1-second period mapped MCER spectral response acceleration (Si.), and seismic coefficients (FA and Fv) for the project site (Table 1). TABLE 1. ASCE 7-16 MAPPED SEISMIC DESIGN PARAMETERS Site Class ASCE 7-16 Parameter Recommended Value F Short -period mapped MCER spectral response acceleration, Ss (g) 1.2291 Long period mapped MCER spectral response acceleration, S1 (g) 0.4371 Short -period site coefficient, FA Long -period site coefficient. Fv 1.01 1.86 Notes: The project site is classified as a Site Class F. But Sd5 and Sdi are based on Site Class D per the code exception for building vibration period less than 0.5 seconds. 4.2. Liquefaction Potential Liquefaction is a phenomenon where soils experience a rapid loss of internal strength as a consequence of strong ground shaking. Ground settlement, lateral spreading and sand boils may result from liquefaction. In general, the soil that is susceptible to liquefaction include very loose to medium dense, clean to silty sands and some silts that are below the groundwater level. The structures supported on liquefied soils could suffer foundation settlement, downdrag loads, or lateral movement that could be severely damaging to the structures. The evaluation of liquefaction potential is complex and dependent on numerous parameters, including soil type, grain distribution, soil density, depth to groundwater, in -situ static ground stresses, earthquake -induced ground stresses and excess pore water pressure generated during seismic shaking. We evaluated the liquefaction potential of the site soils at the maximum -considered earthquake (MCE) level based on the previous SPTs (B-1, B-2, B-4, and B-101 through B-103). Table 2 below presents the seismic input parameters used in our liquefaction analyses, where the magnitude is the maximum magnitude amongthe mean and mode magnitudes from the deaggregation performed at the peak ground acceleration (PGA) using the 2014 United States Geological Survey (USGS) seismic source characterization (SSC) model; and the PGA was derived from ASCE 7-16 for Site Class D. TABLE 2. SEISMIC INPUT PRAMETERS FOR LIQUEFACTION EVALUATION Design Earthquake Mw PGA (g) MCE 7.22 0.580 The simplified triggering criteria proposed by Idriss and Boulanger (2008) and Youd et al. (2001) were used to evaluate the liquefaction potential of the site soils. An SPT hammer efficiency of 60 percent was assumed due to the lack of information on hammer type. Based on our simplified liquefaction analyses, the hydraulic fill and recent deposits are susceptible to liquefaction. Therefore, the depth of liquefaction is along the top of the glacially consolidated soils, as shown in Figure 4. GEOENGINEERS April 1.2022 Page File No. 0676-030-00