Res07 14829 - Laserfiche WebLink

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12/17/2007 Mitigation 11-2: The detailed, design-level geotechnical investigations required under Mitigation 11-1 shall include laboratory analyses of all dredged material and all materials proposed for use as fill. These analyses shall be sufficient to adequately estimate the rate and total amount of fill consolidation following compaction, and the resulting likelihood of differential settlement, especially in the areas of the reduced and reconfigured marina. Design of all fills shall incorporate the results of these analyses to minimize the destructive effects of future settlement, and the investigation shall set forth guidelines that address, at a minimum, the composition of fill materials, methods of fill placement, the required degree of fill compaction, and the layout of the subsurface drainage systems needed to adequately dewater the fill. In addition, all improvements to be constructed on top of or within fills shall be designed in accordance with the recommendations of the detailed, design-level geotechnical investigations. Once a final grading plan has been prepared and building loads determined, estimates of potential settlements for the ground- and pile-supported structures, as well as for downdrag loads, shall be provided. Following completion of fills, settlement shall be monitored and improvement plans shall be modified as necessary. The results of the analyses of dredged material shall be included in any request or application for disposal or reuse of dredged material. All recommendations contained in and derived from the detailed, design-level geotechnical investigations shall be incorporated into the conditions of approval for each structure or construction phase, with implementation enforced by the City throughout the construction period. In general, these recommendations are expected to include, but not be limited to, the following provisions: 1. Support all project buildings on driven piles. At this preliminary point in the geotechnical analysis, Treadwell & Rollo recommends precast, prestressed concrete piles with 100-ton capacity (12 inch) and 125-ton capacity (14 inch) at lengths of 75 to 90 feet and 80 to 95 feet, respectively. Perform pile load tests to evaluate the ultimate capacity and required length of the piles.' 2. If settlements are found to be excessive, consider a surcharge program to reduce the effects of settlement, especially when filling in portions of the former marina. 3. Design ground floor slabs to span between the pile caps and/or grade beams. Fill should not be relied upon for support. 4. Use flexible connections for utilities entering buildings in order to protect against breakage caused by differential settlement. 5. Hinge exterior slabs and ramps attached to buildings in order to protect against breakage caused by differential settlement between the buildings and the outside ground. 6. If settlements are found to be excessive, especially when filling in portions of the existing and former marinas, consider a surcharge program to reduce the effects of settlement. Surcharging consists of placing excess fill in areas where settlements are a concern and leaving it in place a sufficient amount of time to partially pre-consolidate the underlying compressible soil. Atty/Reso/Reso.1772 121707 34 14829 Muff# 613