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

2.2.1. Geophysical Survey As shown in Figure 2, the existing test pits, SPT, and CPT borings are all located outside of the proposed building footprint. Therefore, a geophysical survey was performed at the project site and also at some nearby locations that overlay with some previous borings (e.g., B-1 and B-4), so that correlations between the geophysical survey results and the nearby geotechnical information can be done to characterize the subsurface conditions at the site, including site class and the depth of the glacially consolidated soils. The geophysical survey was completed by conducting multichannel analysis of surface waves (MASW) along five transects (Line 1 through Line 5) and one microtremor array measurements (MAM) across the project site (shown as blue stars), as shown in the Geophysical Survey Arrays, Figure 3. Through the MASW, five two-dimensional (2D) shear wave velocity (Vs) profiles were developed along the five transects, going down to about 70 feet below ground surface (bgs); and a deeper one-dimensional (1D) Vs profile (about 300 feet deep) was developed through the MAM. After calibrated with the nearby boring information (B-1 and B-4), the geophysical survey indicates that the depth of the glacially consolidated soils ranges from 27.5 feet to 35.0 feet bgs across the building footprint. The correlations between the geophysical survey results and the nearby geotechnical information are used in our geotechnical analyses completed as the basis of the geotechnical recommendations. The locations of the survey arrays are shown in Figure 3 and the geophysical survey report is presented in Appendix B. 2.3. Groundwater Conditions Based on the reviewed information, the design groundwater level was assumed at Elevation 0.00 feet on the water side in front of the bulkhead and at Elevation +11.11 feet on the land side behind the bulkhead. 3.0 DESIGN CROSS SECTION Cross Section AW, the location of which is shown in Figure 2, was selected for use in our geotechnical analyses. The soil delineation for Cross Section AW is presented in Figure 4. Due to the lack of survey and subsurface exploration information on the water side, based on our communication with the Port and PND, and review of the previous engineering drawings for the nearby sites, we assumed a riprap rock slope in front of the dike with a 1.5H:1V slope from Elevation +16.00 feet to Elevation +1.00 feet, and with a 5.5H:1V slope from Elevation +1.00 feet to Elevation -12.00 feet. The soil profile behind the dike was horizontally extended to the water side. 4.0 EARTHQUAKE ENGINEERING 4.1. ASCE 7-16 Seismic Design Information The project site is classified as a Site Class F due to the presence of the liquefiable soils below the proposed buildings. Based on our discussions with PND, it is our understanding that the building vibration period will be less than 0.5 seconds. Consequently, the project can be completed usingthe code -based seismic design per American Society of Civil Engineers (ASCE) 7-16; and a site -specific response analysis is not required. GEOENGINEERS April 1. 2022 Page 3 File No 0676 030-00