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330 Land Company, LLC Arroyo Lago <br />9785.004.001 Design-Level Geotechnical Report <br /> <br /> <br /> Page | 1 April 16, 2024 <br />Latest Revision October 31, 2025 <br />1.0 INTRODUCTION <br /> <br />1.1 PURPOSE AND SCOPE <br /> <br />We prepared this design geotechnical report for the proposed Arroyo Lago residential <br />development project located in Unincorporated Alameda County, adjacent to the City of <br />Pleasanton’s eastern city limits. This study was undertaken to characterize subsurface conditions <br />at the site to present our design-level conclusions and recommendations to support grading and <br />utility construction. ENGEO previously prepared a preliminary geotechnical report for the project <br />in 2023. We prepared this report as outlined in our agreement dated September 12, 2022, revised <br />May 15, 2023. We are authorized to conduct the following scope of services. <br /> <br />• Review of relevant background information, including available literature, geologic maps, and <br />reports pertinent to the site <br />• Subsurface exploration, including up to four additional borings to a depth of up to 100 feet <br />below the existing ground surface and laboratory testing of select samples <br />• Assessment of geological and geotechnical hazards at the site <br />• Assessment of existing fill material and conclusions regarding ground improvement treatment <br />• Refinement of our preliminary surcharge recommendations, including a surcharge plan that <br />will include the extent of the surcharge program with recommended height, instrument <br />locations, details, and monitoring <br />• Site preparation and grading recommendations <br />• Foundation design recommendations for the proposed residences <br />• Retaining wall recommendations <br />• Flexible and rigid pavement design recommendations based on the anticipated subgrade <br /> <br />For our use, we received the following pertinent documents. <br /> <br />• CBG Civil Engineers. 2025. Arroyo Lago, Planned Unit Development & Vesting Tentative <br />Map, Tract 8423, City of Pleasanton, Alameda County, California. July 11, 2025. Job No. <br />3435-010. <br />• Haley & Aldrich. 2013. Geotechnical Services During Construction, Filling of Busch Pit, <br />Pleasanton Lakes Development, Pleasanton, California. December 18, 2013. File No. <br />130540-002. <br />• Haley & Aldrich. 2017. Report on Preliminary Geotechnical Investigation, Unincorporated <br />Alameda County, California. June 1, 2017. File No. 130540-002. <br />• Haley & Aldrich. 2019. Final Grading Summary – Geotechnical Services During Construction, <br />Filling of Busch Pit, Pleasanton Lakes Development, Pleasanton, California. <br />December 12, 2019. File No. 130540. <br />• Haley & Aldrich. 2021. Report on Preliminary Subsurface Conditions Report, Unincorporated <br />Alameda County, California. December 15, 2021. File No. 130540-002. <br />• Haley & Aldrich. 2023. Report on ASTM Phase I Environmental Site Assessment. Arroyo Lago <br />Residential Community, Pleasanton, California. June 22, 2023. File No. 0207936-001.