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330 Land Company, LLC Arroyo Lago <br />9785.004.001 Design-Level Geotechnical Report <br /> <br /> <br /> Page | 23 April 16, 2024 <br />Latest Revision October 31, 2025 <br />PERIOD <br />(seconds) <br />PSEUDO-SPECTRAL ACCELERATION (g) <br />MCER DE <br />1.5 1.1 0.74 <br />2 0.88 0.59 <br />3 0.63 0.42 <br />4 0.45 0.3 <br />5 0.34 0.23 <br />7.5 0.19 0.12 <br />10 0.11 0.076 <br /> <br />TABLE 6.3-2: 2025 CBC Seismic Design Parameters, Latitude: 37.6786 Longitude: -121.8563 <br />PARAMETER VALUE <br />Site Class D <br />Mapped MCER Spectral Response Acceleration at Short Periods, SS (g) 1.91 <br />Mapped MCER Spectral Response Acceleration at 1-second Period, S1 (g) 0.76 <br />MCER Spectral Response Acceleration at Short Periods, SMS (g) 1.9 <br />MCER Spectral Response Acceleration at 1-second Period, SM1 (g) 1.7 <br />Design Spectral Response Acceleration at Short Periods, SDS (g) 1.27 <br />Design Spectral Response Acceleration at 1-second Period, SD1 (g) 1.13 <br />MCEG Peak Ground Acceleration adjusted for site Class effects, PGAM (g) 0.67 <br />Long period transition-period, TL (sec) 8 <br /> <br />6.4 EXTERIOR FLATWORK <br /> <br />Exterior flatwork includes items such as concrete sidewalks, steps, and outdoor courtyards <br />exposed to foot traffic only. Provide a minimum section of 6 inches of concrete over 6 inches of <br />aggregate base. Finished subgrade and aggregate base should be compacted in accordance with <br />Section 5.6. Flatwork edges should be thickened to at least below the aggregate base section to <br />help control moisture variations in the subgrade and place reinforcement within the middle third <br />of the slab to help control the width and offset of cracks. Control and construction joints should be <br />in accordance with current Portland Cement Association Guidelines. <br /> <br />7.0 RETAINING WALL RECOMMENDATIONS <br /> <br />7.1 LATERAL SOIL PRESSURES <br /> <br />Unrestrained walls constructed on level and sloped foreground should be designed for active <br />lateral fluid pressure as provided below. <br /> <br /> TABLE 7.1-1: Active Earth Pressure <br />BACKFILL SLOPE CONDITION ACTIVE PRESSURE (pcf) <br />Level 50 <br />3:1 60 <br />2:1 70 <br /> <br />The above lateral earth pressures assume level backfill conditions and sufficient drainage behind <br />the walls to prevent any buildup of hydrostatic pressures from surface water infiltration and/or a <br />rise in the groundwater level. If adequate drainage is not provided, we recommend that an