Reso 2007-083 - Laserfiche WebLink

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Obiectives of the Proiect The purpose of the project is to close one of the last maj or gaps in the Alameda County portion of the Bay Trail, a planned pedestrian and bicycle trail that circles San Francisco Bay. The objectives for the project include th~ following: · Provide an architecturally pleasing bridge across Oyster Bay Slough; · Provide a bridge that requires low maintenance; · Provide a bridge that can support a 10,000 pound (4,536 kilogram) emergency vehicle; · Minimize environmental impact; · Provide an overall bridge length of approximately 348 feet (1 06.1 meters), with a railing height of 54 inches (1.4 meters), and bridge clear travel lane of 10 feet (3.1 meters); · Provide a minimum clearance of 5 feet (1.5 meters) above Mean Higher High Water; · Complete the 630-foot (192-meter) gap in the Bay Trail by constructing a new trail on or adjacent to the levee; · Design the Bay Trail connection to comply with applicable trail standards and allow the continued use of the levee by city of San Leandro maintenance vehicles. Detailed Proiect Description Oyster Bay Slough Bridge A four-span steel bridge supported on large diameter concrete-filled steel pipe piles has been recommended to meet the construction, architecture, and engineering objectives (Figure 4). With only three water piers, the design would minimize environmental impact and foundation work in the water. The three large diameter steel pipes would be driven with a large mechanical hammer and they would also provide the lateral strength and stiffhess needed for seismic loads. The proposed bridge would be approximately 348 feet (l 06.1 meters) long, with a clear travel width of 10 feet (3.1 meters) and railing height of 54 inches (1.4 meters). The bridge structure consists of four prefabricated steel truss pieces, measuring approximately 83.5 feet (25 meters) in length (Figure 4). The bridge would be anchored to abutments on the south and north sides of the Oyster Bay channel by short seat type abutments on precast concrete pile foundations. The elevation of the bridge abutments would be 15.0 feet (4.5 meters) on the north side and 17.4 feet (5.2 meters) on the south side (elevations in NA VD 88). The bridge structure would be supported by three piers consisting offour-foot (lA-meter) diameter cast-in-steel-shell (CISS) concrete piles. The CISS piles (steel with concrete fill) would require significantly more construction effort than precast piles; e.g., the requirement to drill and remove soil inside the casing. However, precast piles would require an 80-foot (24.4-meter) crane to install. CISS piles are proposed because they can be installed with a smaller crane, which would minimize equipment height encroachment into the regulated FAA airspace during pile driving activities. CISS piles can be driven in shorter sections with a smaller crane and spliced together, thereby minimizing intrusion into the regulated FAA airspace (Mark Thomas & Co., 2004b). Y4204IS.00693.doc - 4/5/07 -2-