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Peer Review of Geotechnical and Geologic Hazard Investigations BSK Project G2300051 11991 Dublin Canyon Road (Hana Japan) September 6, 2024 Pleasanton, California Page 4 7. Geotechnical Report, Section 4.5 (Laboratory Testing): Corrosivity testing consisted of pH and sulfate testing. It is a standard of practice to include resistivity testing as well. Consideration should be given to conducting resistivity testing after mass grading to help assess corrosion potential of buried metal. Depending on such test results, corrosivity mitigation measures may be needed, such as wrapping utility piping that is sensitive to corrosion. 8. Geotechnical Report, Section 5.1 (Expansive Soil): This section states that thicker colluvium soil was encountered on the eastern portion of the Site. Based on our review of the current explorations at the Site, the western portion of the Site has thicker colluvium soil deposits. ENGEO should evaluate whether this is a concern or not. 9. Geotechnical Report, Section 5.4.1 (Ground Rupture): Please refer to Comment #2.a above regarding the recommended building fault setbacks. Figure 2 may need to be revised accordingly. 10. Geotechnical Report, Section 5.4.3 (2007 CBC Seismic Design Parameters): We understand these parameters have been superseded by the those provided in the CBC Update Letter. However, please refer to Comment #1 above regarding Site Class characterization and seismic design values at the Site. 11. Geotechnical Report, Section 5.5 (Soil Corrosion Potential): Same as Comment #7 above 12. Geotechnical Report, Section 6 (Earthwork Recommendations): General Note: Throughout the Geotechnical Report, when referring to earthwork recommendations, Section 4 is referred to. These references should be updated to refer to the correct subsections in Section 6. 13. Geotechnical Report, Section 6.1 (Expansive Soil Mitigation): a. In the statement that indicates no expansive clay should be placed within the upper 3 feet of building pads, the top of the building pad should be defined such as finished subgrade or bottom of slab. b. This section of the report should state what type of soil material should be used to replace expansive (soil) material that is removed from the upper 3 feet of the building pads. BSK assumes the replacement soil material would consist of a low expansion potential soil having a plasticity index of less than 12 per Section 6.5 of the Geotechnical Report. 14. Geotechnical Report, Section 6.5 (Acceptable Fill): This section states that on-site soil and rock material is suitable as fill material. However, previous sections have indicated that the on-site soil consists of expansive soil and that expansive clay should not be placed within the upper 3 feet of building pads. Consideration should be given to clarifying what on-site soil and rock is acceptable as fill material or clarifying where it can be used. In addition, this section indicated that fill material should have a plasticity index of less than 12. Clarification should be given to whether this refers to on-site soil or imported fill. 15. Geotechnical Report, Section 6.6.2.2 (Structural Areas) Note 2: It appears that the second sentence in this note is incomplete. Please provide clarification if appropriate. 16. Geotechnical Report, Section 6.6.2.2 (Structural Areas): Consideration should be given to eliminating the option to use native clay soils for pipe bedding and backfill where utility trenches cross perimeter building foundations. Consideration should be given to only recommending sand cement slurry for this purpose because it is very difficult to properly compact clayey soils under the pipe haunches.