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<br />12/1712007 <br /> <br />VIII. SOilS AND GEOLOGY <br /> <br />A. Geotechnical Hazards Associated with Proiect Grading <br /> <br />Potential Impact 11-1: The interaction of existing geotechnical conditions on <br />the project site with the proposed grading, dredging, and surface modifications--and their <br />combined effect on surface settlement, seismic hazards, and soil erosion--have the potential to <br />result in significant adverse effects. The applicant's preliminary geotechnical investigation made <br />an initial assessment of these conditions, but a design-level geotechnical investigation would be <br />needed to adequately address all grading, dredging, and stabilization activities on the site. <br />Without such a study--and without the associated supervision of an engineering geologist or <br />geotechnical engineer during project grading, dredging, and construction--the safety and long- <br />term stability of project improvements could not be assured. These possible geotechnical <br />hazards represent a potentially significant impact. <br /> <br />Mitigation 11-1: As recommended by the applicant-commissioned Treadwell & <br />Rollo preliminary geotechnical investigation, require the applicant to retain a registered <br />engineering geologist or geotechnical engineer to prepare detailed, design-level geotechnical <br />investigations to guide the design of all project grading, dredging, and stabilization activities. <br />The detailed, design-level geotechnical investigations shall be performed for each of the <br />structures proposed for the project site. Subsurface conditions shall be explored and laboratory <br />tests conducted on selected soil samples to establish strength parameters for foundation design <br />and perimeter slope stability, and for corrosivity potential of the fill and Bay mud on foundation <br />elements and buried utilities. Specific recommendations shall be developed for foundation <br />support for each building, slab-on-grade floors, pavements, bulkheads, and slope inclinations for <br />permanent slopes. The detailed, design-level geotechnical investigations shall include <br />subsurface investigation to further identify the thickness and the consolidation characteristics of <br />the Bay mud underlying the project site. Recommendations from the investigation shall be <br />incorporated into project grading, dredging, and construction plans to the satisfaction of the City <br />Engineer. <br /> <br />The detailed, design-level investigations, relevant recommendations, and all <br />associated project grading, dredging, filling, and foundation plans, shall be subject to review and <br />approval by an independent engineering geologist or geotechnical engineer retained by the City <br />Engineer at applicant expense. In addition, the project civil engineer shall certify that all <br />relevant provisions of the investigation have been incorporated into the grading, dredging, and <br />construction plans. All earthwork and site preparation shall be performed under the direct <br />supervision of a registered engineering geologist or geotechnical engineer. <br /> <br />Findings: Implementation of these measures is feasible and would reduce <br />these potential impacts to a less-than-significant level. <br /> <br />B. Total and Differential Settlement <br /> <br />Potential Impact 11-2: The presence of weak, compressible Bay mud <br />underlying the on-site fill is the most significant factor influencing the selection of a foundation <br />system for the proposed project. The project's structural loads would be too great to be <br />supported on conventional shallow foundations bottomed in fill or weak Bay mud. Shallow <br />foundations would potentially experience excessive total and differential settlements. These <br />possible effects represent a potentially significant impact. <br /> <br />Atty/Reso/Reso.1772 <br />121707 <br /> <br />33 <br /> <br />14829 <br />Muff# 613 <br />