3A Public Hearing 2006 1204 - Laserfiche WebLink

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GEOTECNIA Project Number: 060805 2888 Darius Way, San Leandro October 27, 2006 Page 13 Slabs should be adequately reinforced or structurally separated to reduce offsets and cracking caused by differential movement between slab sections and between foundations and slabs. We estimate that differential movements on the order of 1 to 2 inches should be anticipated between conventional slabs-on-grade and pier foundations. Slabs should be provided with cold joints or crack control joints at a spacing of not more than 10 feet in each direction. The reinforcing steel should pass through joints to tie slab sections together. The project structural engineer should use the above criteria as a guideline for design of the slabs. Proposed Drivewav Pavement Based on the two R-value test results (see bottom of Appendix C), we recommend using a subgrade R-value of 50 for design of the pavement section along the proposed driveway. We anticipate that the Traffic Index (TI) value for the proposed driveway may be 4.0 to 5.0; however, the actual design TI value needs to be determined by the project civil engineer. The recommended pavement section for the proposed driveway should consist of a minimum 3-inch-thick layer of Asphalt Concrete (AC) over 6 inches of Aggregate Base (AB). The pavement areas near proposed garbage bins and where trucks may make sharp turns should be made thicker or reinforced concrete slabs should be used to resist the lateral shear forces from the wheel-turning motion. Adequate surface and subsurface drainage (edge drains) should be provided to prevent ponding of water on the pavement surface and saturation of the base layer and pavement subgrade. The subgrade soils should be scarified to a depth of 6 inches, moisture conditioned to at least 3 percent over the optimum moisture content, and compacted to at least 95 percent relative compaction in accordance with ASTM test method D 1557. The pavement section materials should also be compacted to 95 percent relative compaction. Drainae:e Improvements The surface drainage at the site should be improved by collecting and conveying surface runoff to appropriate outlets. Positive drainage should be provided away from the structures. Roof downspouts should discharge into closed conduits that drain into the site stonn drain system or onto concrete slabs that drain at least 15 feet away from the improvements to appropriate outlets. Surface runoff should be kept from flowing onto the slopes or from ponding at the site. The existing concrete~lined ditches on the slopes above and below the access road should be maintained so they continue to function as intended, and new concrete-lined ditches should be constructed along the tops of new retaining walls to collect surface runoff, as applicable. Collected runoff should be conveyed to catch basins and discharged into the stonn drain system through solid collector pipes.