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�w Fairview Street Bridge Rehabilitation v.•. RFP No. 111 SEISMIC ANALYSIS WKE is one of the few firms that have widened and retrofit bridges in this stretch of the Santa Ana River. An understanding of the river history is important to understanding the potential seismic collapse mechanisms of these bridges. In the mid 90's, this reach of the Santa Ana River was concrete lined, lowering the riverbed about 9' -0" from the original design grade of many of the structures, leaving the bottom of footing 4' -0" above ground. The river was lowering reduces the pile vertical and lateral capacity, and exacerbating liquefaction instability. The bridge was seismically retrofitted in the mid 90's as part of the riverbed lowering completed by the County. The retrofit included casing the exposed piles and adding pipe restrainers at the hinges. Many of these early retrofits did not include liquefaction as a consideration in overall bridge stability, both vertical and lateral. In our experience on Fifth Street and the old First Street bridges over the Santa Ana River, the pile concrete casing did not adequately address the bridge stability during an earthquake. In both cases, a 'foundation retrofit was required in addition to hinge restrainers. In the case of Fifth Street, we used innovative solution of micropiles for the foundation retrofit since these can be installed under low overhead clearance situations. WKE's past experience on these bridges drives our alternatives development and ensures a cost effective design is chosen from the start. BRIDGE AESTHETICS One of the keys to a successful project is the acceptance by the local community using the structure on a daily basis. This includes school children attending the Spurgeon Intermediate School, users of the Santa Ana Bike Trail, and visitors to the nearby parks. Our team will work with the :200*• WKE's enhanced Aesthetic design incorporated colored river rock finish and custom hand rails on concrete barriers for Foothill Boulevard Bridge over San Dimas Wash. City and members of the general community in a process to arrive at a design that respects the recent surrounding park improvements, provides a level of aesthetic detail beyond a standard Caltrans solution, and provides a project that enhances the community beyond the basic functionality of crossing over the Santa Ana River. Solutions may include the use of the open railing Type 80 concrete barrier, with the additional of architectural finish included in the bridge. On Foothill Blvd in relatively rural San Dimas, the Type 80 barrier was chosen with a colored river rock finish to pay tribute to the many rock walls and foundations of the surrounding craftsman homes. BIKE TRAIL The existing Orange County Regional Bike Path crosses underneath both ends of the Fairview Street. The jurisdiction of this bike trail is under the County of Orange Harbor, Beaches and Parks Division of the Resources and Development Management Department. They require that the trail be open at all times with maximum closures for construction activity of 15 minutes. Longer closures require bike detours which must be approved by the agency. This requirement will be difficult to meet during foundation construction as bents 2 and 7 are embedded in the bike path slope requiring extensive excavation. Aviable alternative is to detour bike traffic to the bottom of the river. We have 40V K Design Services for Fairview Street Bridge Rehabilitation Understanding of Noed 117 25C -23