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7C <br /> Page 54 <br /> VIII. SO[LS AND GEOLOGY <br /> A. Geote�hniaal Hazards Associated with Proiect Gradinq <br /> Potential tmpact 11-1: The interactian of existing geotechnical conditi�ns 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 wou{d 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 geologisf or <br /> geotechnical engineer during project grading, dredging, and construction--the safe#y and long- <br /> term s#ability of project improvements coufd nat be assured. These possible geotechnical <br /> hazards represent a potentially signi�cant impact. <br /> Allitigation i1-1: As recommended by the applicant-commissianed i readwell & <br /> Rollo preliminary geotechnicaf investigation, require the appficant to retain a registered <br /> engineering geologist ar geotechnical engineer to prepare detailed, design-level geotechnical <br /> investigations to guide the design of al! project grading, dredging, and stabilization activities. <br /> The detailed, design-level geotechnica{ investigatians shall be performed for each of the <br /> structures propased for#he project site. Subsurface conditions shall be explored and faboratory <br /> #ests conducted on selected soil samples to es#ablish 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 shaEl be developed far foundation <br /> support for each building, slab-on-grade floors, pavements, buikheads, and slope inclinations for <br /> permanent slopes. The detailed, design-levei geotechnical investigations shall include <br /> subsurface investigation to further iden#ify 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 satisfacfion of the City <br /> Enginesr. <br /> The detailed, design-level investigations, relevant recommendations, and all <br /> asso�iated project grading, dredging, filling, and foundation plans, shall be subject to review and <br /> approval by an independent engineering geofogist ar geotechnical engineer retained by the City <br /> Engineer at applicant expense. In addition, the project civil engineer shall certify that al! <br /> relevant provisions of #he investiga#ion 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 /> Findings: ]mplementatian of these measures is feasible and would reduce <br /> these potentiai impacts to a Jess-fhan-significant level. <br /> B. Total and Differentiaf Settlement <br /> Potentiat Impact 11-2: The presence of weak, campressible Bay mud <br /> underlying the on-site fll is the most significant factor influencing the sefection o# a foundation <br /> system for the proposed project. The project's structural loads would be too great to be <br /> supported on conventional shallaw foundations bottomed in fi[l or wsak Bay mud. Shallow <br /> foundations wouid potentiaiiy expe�ience excessive tatal and differential seitlements. These <br /> possible effects represent a pafentially significant impact. <br /> AttylReso/Reso.1772 33 <br /> 121307 <br />