3632 RUCKER AVE THE LANDING AT PORT GARDNER Geotech Report 2023-04-10

MTT Construction LLC JN 18188 April 16, 2018 Page 2 liquefaction be evaluated for the peak ground acceleration of the Maximum Considered Earthquake (MCE), which has a probability of occurring once in 2,475 years (2 percent probability of occurring in a 50-year period). The MCE peak ground acceleration is adjusted for site class effects (FpGA) and equals 0.56g. The soils beneath the site are not susceptible seismic liquefaction under the ground motions of the MCE because of their dense nature. Sections 1803.5 of the SBC and 11.8 of ASCE 7 require that other seismic-related geotechnical design parameters (seismic surcharge for retaining wall design and slope stability) include the potential effects of the Design Earthquake. The peak ground acceleration for the Design Earthquake is defined in Section 11.2 of ASCE 7 as two- thirds (2/3) of the MCE peak ground acceleration, or 0.37g. The surcharge wall loads on foundation and retaining walls that could be imposed by the MCE can be modeled by adding a uniform lateral pressure to the above-recommended active pressure. The recommended surcharge pressure is 8H pounds per square foot (psf), where H is the design retention height of the wall. Using this increased pressure, the safety factor against sliding and overturning can be reduced to 1.2 for the seismic analysis. Geotech Consultants, Inc. should be allowed to review the final development plans if they change from the current plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report and our 1999 study, in their entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. LIMITATIONS The conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the test pits are representative of subsurface conditions on the site at this time. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. This report has been prepared for the exclusive use of MTT Construction LLC and their representatives for specific application to this project and site. Our conclusions and recommendations are professional opinions derived in accordance with our understanding of current local standards of practice, and within the scope of our services. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Our services also do not include assessing or minimizing the potential for biological hazards, such as mold, bacteria, mildew and fungi in either the existing or proposed site development. GEOTECH CONSULTANTS,INC.