7818 LARIMER RD B Geotech Report 2022-10-25

Crustal earthquakes are generally concentrated above a depth of approximately 10 to 20 km. Based on our literature review, the estimated maximum magnitudes of these crustal earthquakes are in the range of M6.0 to M6.5. Based on site geology, topography, and our preliminary evaluation, in our opinion, the site may be susceptible to severe ground shaking and landsliding during a major earthquake. Ground acceleration more than 0.3g may occur at the site. As mentioned above, it should be noted that most of the northwestern United States is susceptible to similar earthquake -related hazards. A detailed site -specific seismic evaluation of any kind was beyond the scope of this report. Based on the results of our subsurface explorations and review of available literature (2009 International Building Code), in our opinion, a site classification "C" and a design PGA of 0.35 may be used for this project. However, this site classification may be revised by performing a site -specific shear wave velocity study. The 1 Hz spectral acceleration with 2% probability of exceedance in 50 years is 120-140% g. Subsurface soil conditions at the site are susceptible to liquefaction. Seismically induced slope instability may also occur on a localized scale in the steep slope area; however, such an evaluation was beyond our scope of services. A detailed seismic hazards evaluation of the site was beyond our scope of services. CONCLUSIONS AND RECOMMENDATIONS Based on the results of our geotechnical evaluation, in our opinion, the site is suitable for the proposed construction provided following recommendations are strictly followed. It should be noted that our conclusions and recommendations are intended as design guidance. They are based on our interpretation of the geotechnical data obtained during our evaluation and following assumptions: • Proposed/Final site grades or grading plans will be reviewed and approved by us to provide geotechnical design and to assure that proposed cut and fill activities do not adversely impact site stability; • Proposed foundations will be constructed on level ground with the consideration of the results of our geologic hazards evaluation as described earlier; and • Structural loads will be typical of single family residence. Construction recommendations are provided to highlight aspects of construction that could affect the design of the project. Entities requiring information on various aspects of construction must Proposed Construction Project No: 0470-WA18 January 24, 2019 Page No: 5 of 17