U.S. 6 Broadway Viaduct
Pottawattamie County, Iowa
Client:
Iowa Department of Transportation
Schemmer was retained by the Iowa Department of Transportation to design a replacement structure for the U.S. 6, Broadway Viaduct, a key transportation artery and a critical public structure in the City of Council Bluffs. RDG and GSI were subconsultants to Schemmer providing landscape architecture design and geotechnical engineering services. The project team collaborated extensively with the Iowa West Foundation (IWF) and Ed Carpenter who was selected by IWF to design and construct a public art sculpture on the proposed viaduct.
At 1,537 feet long, the Viaduct will stretch from approximately 9th Street to 14th Street. The new structure will consist of 12 spans, constructed with pretensioned / prestressed concrete bulb tee E beams. The viaduct crosses over the Indian Creek conduit, several City streets and the CNIC and UP Railroads. Due to the nearby location of residential and historic structures adjacent to the viaduct, vibrations from typical bridge construction activities had to be limited. To reduce vibrations drilled shafts, which have minor vibration when installing, were designed to support the piers and abutments. The drilled shafts will undergo a base grouting process after installation to increase capacity.
On the east and west ends of the bridge, a 525 ft. and 365 ft. approach embankment will be constructed to allow touch-down of the viaduct to the existing grade. Due to compressible soils under the approach embankment, lightweight foam concrete fill (LFCF) will be used for the embankment material. The LFCF material, along with some minor soil core-out, will result in zero net loading on the existing soil, thereby eliminating settlement and decreasing time necessary for construction. Aesthetic details will be incorporated into the structure, including a public art installation funded by the Iowa West Foundation. The project is scheduled to begin construction in April 2010 and be complete in the fall of 2011.