SR 05:277 - Laserfiche WebLink

Design Options: There are two design options for the proposed new bridge, and five options for railings for the existing historic bridge. New Bridge Historic Concrete Option: This option uses a concrete rail system designed to replicate the historic era of the existing bridge. The rail is constructed of concrete with arches formed through the concrete rail. A steel vertical member bar is installed in the concrete arches to pay homage to the adjacent steel bridge, and concrete pilasters with reveals are placed with equal spacing along the bridge. These elements create a balanced design for the new bridge. Three options for the railing on the existing historic bridge have been developed to tie the two bridges together with a design element. Options Band D each use an element from the new bridge design, the concrete pilaster, but differ in the design of the metal railing. Option Fuses just the metal railing. New Bridge Hybrid Railing Option: This option uses a steel frame railing installed between solid metallic panels with a City of Pleasanton symbol located in the panel. According to the Architect, the design introduces strong horizontal elements interrupted by double vertical post and panel pilasters that blend the metal railing with both historical and contemporary aesthetics. This railing would be mirrored with the option D railing on the existing historic bridge. An alternate railing on the existing bridge, option A, is similar to this railing with the panel pilasters, but the detailing on the pilasters is modified, and there is a single vertical post in place of the double posts. Staff is recommending the historic concrete option in combination with option B of the existing bridge railing options. This combination provides a balanced new bridge: both railings on the new bridge are identical. Using option B brings components of the new bridge (pilasters at both ends of the bridge, and a metal railing) to the existing historic bridge, but recognizes the separate identities of the two bridges. Option B also provides metalwork that is more similar to the metal work of the historic bridge by the use of crossing steel members at the bottom of the railing. While the hybrid option would provide railings on the outside of both bridges that are identical or similar, the new bridge would have railings that do not match. The reason is that the metal railing is insufficient to act as a guardrail for vehicles; so, two additional concrete guardrails must be installed. In addition to creating an asymmetric new bridge with respect to the railings, the design requires additional width as the extra guardrail between the sidewalk and metal rail takes up space in the bike lane and sidewalk. This will add to the structure costs for the bridge. Funding: The original funding plan for the Bernal Avenue bridge(s) and interim and ultimate alignments, involved the Laguna Oaks project (The De Silva Group) paying for roughly half the costs and the SFWD paying for the other half. Under the original bridge plan, the SFWD property developers were to pay for the cost of an additional 3-lane bridge that was to replace the existing steel truss bridge. The cost of the replacement of the old bridge and the ultimate Bernal Avenue improvements were expected to be more or less equivalent to the cost of the "interim" bridge, the "interim" improvements to the existing bridge, and the interim Bernal Avenue improvements that the Laguna Oaks project was to construct. SR:05:277 Page 3 of 4