Item 18 - Appeal Application Nos. 2023-02 and 2023-03 for Cabrillo Town Center project

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3.0 CONCL USIONS Based on the results of our geotechnical evaluation and review, it is our opinion that the proposed site development is feasible from a geotechnical standpoint, provided the following recommendations included in this report are incorporated into the project plans and specifications, and followed during site grading and construction. Our geotechnical conclusions are as follows: • The site is not located within an Earthquake Fault Zone. • No groundwater was encountered in our geotechnical borings across the site. We do not anticipate that the site excavation will encounter groundwater. Design groundwater should be considered at a depth of below 40 feet below the existing grades. • The site is not located within an area deemed to have a potential for liquefaction (CGS, 2002). Based on our site assessment, liquefaction potential is low and subsequent seismically induced settlement was found to be on the order of 3 inches or less. • Total static (1 inch or less) and seismically induced settlements (3 inches or less) of up to 4 inches with differential settlements of up to 2 inches in 30 feet should be considered in the foundation design. • Based on the subsurface exploration and our review, the site is underlain by alluvium. The existing fills and alluvial soils are considered potentially compressible/collapsible in the upper approximately 5 to 10 feet. • The anticipated site excavation and the proposed construction will not have an adverse impact on the adjacent properties. • Active or potentially active faults are not known to exist on the site. • Laboratory test results of the onsite soils indicate a medium to high expansion potential. For preliminary design purposes a high expansion potential should be considered in foundation design. • Laboratory test results of the onsite soils indicate negligible soluble sulfate contents and should be considered corrosive to metals. • Laboratory test results of the onsite soils indicate a negligible potential of hydro -collapse underlying the recommended remedial removals. • The onsite soils below recommended remedial grading/excavation depths have a low potential for static settlement (i.e., slightly compressible). • From a geotechnical perspective, the existing onsite soils are suitable for use as fill, provided they are relatively free from rocks (larger than 6 inches in maximum dimension), construction debris, and organic material. Percolation testing conclusions are as follows: • From a geotechnical perspective, allowing storm water to infiltrate the onsite soil in concentrated areas increases the potential for settlement, liquefaction, and water -related damage to structures/improvements, such as wet or pumping subgrade, and should be avoided where possible. If infiltration systems are required on this site, care should be taken in designing systems that control the storm water as much as possible. • Preliminary infiltration testing was conducted at the site as part of the previous site investigation by ACG. Based on the previous testing and results by ACG, site infiltration rates for P-1 through P-3 were calculated to be 4.1-inches per hour, 5.0-inches per hour and 6.2-inches per hour, respectively. The results do not include a factor of safety. Test P-1 through P-3 were conducted in silty sand lenses of the younger fan deposits at approximately 5-feet below the ground surface. Project i y ouncil 18 — 826 1 3 , 2021