ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306855
Replacing the deteriorated Elwha River Bridge in Clallam County, Wash., with a new segmental cast-in-place concrete design gave rise to a variety of challenges to ensure the project balanced the needs of the local community, historic- preservation groups, and the tribal jurisdictions. Foremost was the need to overcome severe terrain and other natural obstacles. Another constraint included suspending a pedestrian deck beneath the superstructure. These site- specific challenges required a tremendous effort even before construction of the bridge could be addressed. The $19.7-million structure replaced a 1914 steel-truss bridge closed to traffic in 2007 because of advanced deterioration. Listed on the National Register of Historic Places, the one- lane Elwha River structure had been downgraded to load-restricted after serious structural deficiencies were found in 1992. In 2003, the county hired BergerABAM Engineers to begin the design process. Bids submitted exceeded the original budget and an innovative combination of funding sources was needed before construction could proceed. Design of the replacement bridge included a main vehicular structure and a separate pedestrian and bicycle deck. The main structure is 589 ft long and features cast-in-place concrete box girders built using the balanced cantilever and cast-on-falsework construction methods. The cantilever technique minimized disturbances to sensitive environmental areas along the river. Access Proved Difficult The terrain surrounding the remote site posed considerable challenges. Access to Pier 3 on the east bank required construction of a 2-mile-long access road that utilized an old railroad right- of-way. Access to Pier 2 on the west bank proved to be one of the most difficult aspects of the project. Situated on a rocky knoll approximately 50 vertical ft down a steep embankment from the existing west abutment, it was bounded to the north and east by vertical drop-offs and to the south by an existing crib wall of unknown s t a b i l i t y t h a t re t a i n e d a p re v i o u s landslide area. Contract documents were silent about access means. As a result, Parsons had to design-build a ramp and work pad. Environmental constraints prohibited blasting, so specialized rock-grinding equipment was used in addition to conventional excavation methods. A provision to facilitate continuous access required a split-ramp design. profile ELWHA RIVER BRIDGE / CLALLAM COUNTY, WASHINGTON DESIGN ENGINEER: BergerABAM Engineers, Seattle, Wash. CONSTRUCTION ENGINEER: International Bridge Technologies, San Diego, Calif. TRAVELER ENGINEER: John Parkin & Associates, Vancouver, Wash. FASLEWORK ENGINEER: VAK Engineering, Beaverton, Ore. PRIME CONTRACTOR: Parsons Construction Group, Sumner, Wash. PRECASTER (PEDESTRIAN BRIDGE): Concrete Technology, Tacoma, Wash., a PCI-certified plant by Greg Bennett, Warren Hallam, and Scott Nelson, Parsons Construction Group BATTLING THE TERRAIN Constructing the new Elwha River Bridge in Washington State required confronting steep, rocky banks, as well as flooding and environmental restraints The Elwha River Bridge in Clallam County, Wash., used cast-in-place segmental concrete to meet significant challenges of terrain. The bridge includes a lower pedestrian deck consisting of precast concrete bulb-tee girders and deck panels. Photos: Parsons Construction Group. The terrain surrounding the remote site posed considerable challenges. 24 | ASPIRE , Spring 2010 Elwha_spr10-1.indd 24 4/30/14 11:06 AM