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Geotechnical Re ort "z 1 -2& Identify and summarize any special geologic conditions, including, but not limited to, compressible and expansive soils, tunnels and mine shafts, unstable slopes, active seismic zones, excessive ground water and areas prone to liquefaction. Indicate if these conditions will prevent the use or significantly increase the cost of developing the site for a public library building. According to the Lowney Associates Geotechnical Investigation, dated November 2002, the project site is feasible for the proposed library design, provided the project is designed in accordance with the preliminary recommendations presented in the geotechnical report. The predominant geological condition at this, and every site within Redwood Shores, is the existence of a deep layer of bay mud immediately under the topsoil layer. Therefore, the design provides for an extensive foundation system to address the existing soils conditions. A cost premium is associated with the foundation system of this building in comparison to a foundation system that might be designed for a flat inland site with ideal soils conditions. Since the entirety of the Redwood Shores Library Service Area exists on San Francisco Bay infill, a site with "ideal soils conditions" does not exist in Redwood Shores. The primary geotechnical concem is the potential for substantial total and differential settlements of shallow foundations, such as spread footings or a reinforced concrete mat. To address this condition, the proposed foundation system is comprised of driven - oncrete piles. Another concern is significant differential settlement between a pile- supported building and the ground adjacent to the building, due to the long -term settlement of the approximately twenty -two feet of highly compressible bay mud immediately under the existing fill materials blanketing the site. The bay mud will experience total and differential settlement due to the weight of new 611, and building and parking loads. Significant additional differential settlement is expected to occur in areas where the thickness if existing fill and any additional new fill varies abruptly, as well as in areas where building loads supported on fill vary abruptly. In xder to minimize this potential, the building design provides for a consistent building height, and minimal differential massing of the Finish grading plans for the site, and the structural system of the building, are designed to minimize abrupt grade changes and Ilar concentration of building loads to decrease differential settlement. The building is also located away from the raised which is advised in the report. Describe any necessary demolition of structures and the associated costs involved with the site. Version 1.3 (5130/02) 21 (If no demolition, indicate by *N/A*) Structure(s) to be Demolished Demolition Cost Estimate 1. > Site Clearing, Demolition $ 51,961 2. > N/A $ 3. > N/A $ 4. > N/A $ 5. > N/A $ 6. > N/A $ Total Demolition: > $ 51,961 Version 1.3 (5130/02) 21