Indian River Inlet Bridge - Rising Above the Ordinary
W. Denney Pate, P.E.
Construction will begin late this fall on the new Indian River Inlet Bridge - a striking concrete cable-stayed arch that will blend with the sand dunes of the Delaware State Seashore Park as it crosses the Indian River Inlet. Designed with significant input from the public, the bridge will span the entire inlet with a 1,000' main span, thereby eliminating concerns over scour around piers in the inlet - the nemesis of previous bridges at this location.
The Delaware Department of Transportation, under the direction of Secretary Nathan Hayward, III, empowered interested parties in southern Delaware to actively participate in the selection of aesthetic features for this unique bridge, the first major highway bridge of its type. Community design charettes, held over a sixmonth period in 2003, attracted hundreds of involved citizens and stakeholders. Through consensus voting, they determined the bridge type, shapes, colors, lighting and all aesthetic elements, resulting in a bridge design that is being closely watched and greatly anticipated by bridge enthusiasts nationwide.
Figg Bridge Engineers is responsible for the bridge design and is leading the design team, with member Rummel, Klepper & Kahl, LLP for highway design; public participation and community liaison team member Kramer & Associates, Inc.; geotechnical design by MACTEC; landscape design by LDR, Inc. and lighting design provided by The Mintz Lighting Group Inc.
DelDOT had taken active measures in the past twenty years to address scour issues in the Inlet, however, the long-term economical solution is to remove all piers from the water with a 1,000' main span. Piers for the new bridge will be founded on land both north and south of the Inlet. This configuration also provides for potential future expansion of the Inlet width to mitigate navigational challenges of the swift water flow. Concurrent with the bridge construction, significant enhancement plans for the Delaware State Seashore Park will be undertaken. The enhancements include an inlet promenade, park buildings, campground facilities, and playgrounds.
At the first community design charette, participants voted for a design theme of “Harmony with Nature”. This influenced the future design alternatives created by the team and presented in subsequent charettes for participant voting. The need to span the inlet drove the decision for a cable-supported bridge type; however, based on input at the first charette, the arch design was selected instead of a more traditional pylon shape. Subsequent public input resulted in the single plane of radial stays, open back spans, a tulip shape for the arch cross section, subtle blue feature lighting, an ornamental pedestrian railing that incorporates natural elements and a surface for the pedestrian pathway that mimics the beach.
Final design activities for this unique structure are underway and will be completed principally under the requirements of the AASHTO LRFD Design Specifications. The bridge arrangement includes spans of 150' - 1000' - 150'. The 150' back spans, selected by the charette participants, provide additional visual openness below the bridge to accentuate the below deck arch supports. The unique cross section of the bridge deck consists transversely of a precast southbound box girder, a cast-in-place arch tie beam and a precast northbound box girder. The northbound girder includes additional width for the 12' pedestrian sidewalk on the east (or ocean) side of the structure.
Construction of the bridge is anticipated over a three-year time frame with the entire project completed in four years. Numerous events and activities involving the public, who assisted in the creation of this unique structure, are planned beginning with a groundbreaking ceremony in October.
W. Denney Pate, P.E. is Senior Vice President/Principal Bridge Engineer for Figg Bridge Engineers, Inc.
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