H&H is providing movable bridge design for a unique bridge with a high volume of marine traffic in Slaughter Beach, DE. The Cedar Creek Bridge is one of the state’s most frequently operated movable bridges. As a subconsultant, H&H performed an initial study of various bridge replacement alternatives for DelDOT, including preliminary costs and advantages of each bridge type. Ultimately a single-span Dutch-style bascule bridge was selected.
The existing bridge, a bobtail swing span, had shown various signs of deterioration and had reached the end of its service life. Increasingly frequent high water events resulted in mechanical and electrical equipment being submerged, requiring ongoing maintenance and repair. A key objective for the project is to relocate mechanical components of the movable bridge above flood elevation to ensure that equipment stays out of the flood zone.
The new bridge maintains current roadway approach profiles, featuring new precast concrete approach spans on both sides of the movable span. The upper balance frame and counterweight are supported by an “A” frame tower. The bascule leaf opens to an 80-degree angle, taking 90 seconds to reach the fully open position. The new structure widens the roadway to accommodate a shared-use bicycle lane/shoulder while maintaining the existing roadway profile. All new clearances will either match or exceed existing clearances. An innovative system was developed to install the piles and sheet and tie-back system for the new abutments behind the existing abutments to minimize the environmental impacts, in-water work and maintain the necessary hydraulic opening of the channel.
Installation of new traffic signals and cameras, CCTV, and new security systems in the control house and around the project site will improve the facility’s safety and integrate the bridge into DelDOT’s statewide traffic and TMC operations system. The hydraulic system is located within the new control house, and the hydraulic cylinders that raise and lower the leaf are located on the A-frame towers. The bridge has been designed to have a 75-year design life, and the approximate construction cost is $30 million.
As part of the design team, H&H was additionally responsible for coordinating with the United States Coast Guard and other key stakeholders to minimize disruptions to the public during construction. In addition to meeting with local town councils, virtual and in-person community outreach meetings were held to provide project information to the residents and businesses and obtain feedback for evaluation and incorporation into the final design.