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330 Land Company, LLC Arroyo Lago <br />9785.004.001 Design-Level Geotechnical Report <br /> <br /> <br /> Page | 8 April 16, 2024 <br />Latest Revision October 31, 2025 <br />A groundwater study was prepared in March 2023 by the Zone 7 Water Agency for the Livermore <br />Valley Groundwater Basin, whose extents include the site within its boundary. According to the <br />groundwater gradient map prepared as a part of this study, the groundwater of the upper aquifer <br />is approximately sloping from Elevation 290 feet (NAVD88) at the southern end of the site to <br />approximately Elevation 272 feet (NAVD88) at the northern area of the site. <br /> <br />For analysis purposes, we have considered a design groundwater depth of 50 feet based on <br />current explorations and historical data. Fluctuations in groundwater levels should be expected <br />during seasonal changes or over a period of years because of precipitation changes, perched <br />zones, and changes in irrigation and drainage patterns. <br /> <br />2.7 LABORATORY TESTING <br /> <br />We performed geotechnical laboratory testing on select soil samples recovered during our field <br />exploration to evaluate their physical index properties and strength characteristics. The laboratory <br />tests that were performed, the associated ASTM procedures, and location of the results in this <br />report are shown in Appendix A. <br /> <br />TABLE 2.7-1: Laboratory Testing <br /> <br />SOIL CHARACTERISTIC TESTING METHOD LABORATORY TEST <br />RESULT LOCATION <br />Natural Unit Weight ASTM D7263 Appendices A and B <br />Natural Moisture Content ASTM D2216 Appendices A and B <br />Atterberg Limits ASTM D4318 Appendices A and B <br />Grain Size Distribution ASTM D1140 Appendices A and B <br />Unconsolidated-Undrained Isotropic Triaxial Compression ASTM D2850 Appendix B <br />Unconfined Compression ASTM D2166 Appendices A and B <br />Swell Test B ASTM D4546 Appendix B <br />Consolidation – Incremental Loading ASTM D2435 Appendix B <br /> <br />In addition to the tests listed in Table 2.7-1, corrosivity testing of a sample collected during our <br />exploration was performed by CERCO Analytical. The results are presented in Appendix C. <br /> <br />3.0 CONCLUSIONS <br /> <br />Based on the exploration and laboratory test results, the site is suitable for the proposed <br />residential development provided the geotechnical recommendations in this report are confirmed <br />by further explorations/evaluations and properly incorporated into the design plans and <br />specifications. <br /> <br />The primary geotechnical concerns for the proposed site redevelopment include the following. <br /> <br />• Presence of existing undocumented fill <br />• Presence of moderately to highly expansive soil <br />• Settlement of potentially compressible layers due to building loads and fill placement <br />• Strong ground motions <br /> <br />These and other pertinent design issues are discussed in the following sections.