In 1997, the bridge was listed on the National Register of Historic Places due to its unique patented design. In 2004, KLJ was hired by the North Dakota Department of Transportation (NDDOT) to conduct an Environmental Assessment (EA)/Section 4(f) Evaluation to determine whether to rehabilitate or replace the historic Rainbow Arch Bridge, spanning the Sheyenne River. The EA studies several alternatives including: rehabilitation of the existing bridge for one-way traffic with a new bridge adjacent, replacement with a conventional bridge, and replacement with a new bridge following the original design. After an extensive public involvement process, the NDDOT selected the public’s preferred alternative: In-Kind Replacement with a new Marsh Arch bridge in accordance with current standards.
KLJ provided final design and construction engineering for the project which presented many unique design challenges, including:
Functioning reinforced concrete through arch design. The arches are largely reinforced with structural steel trusses designed as self-supporting during construction – no falsework in the channel was required to build the arches.
Abutment design consisting of 63 HP14X73 steel piles to resist arch forces, earth forces and vehicle live loadings.
22-foot tall abutment backwalls to retain the river bank.
Maintaining patented design elements while enlarging the structure (21 feet longer and 22 feet wider) and utilizing modern construction materials and techniques.
Establishing a construction sequence allowing contractors flexibility in means and methods.
Lighting design for this project included duplicating historic fixtures from the original design onto the new bridge. To better illuminate the roadway between the arches, an additional fixture was hidden on the structure to ensure safety and preserve the historic integrity of the bridge. As part of reconstructing the approaches to the bridge, several existing light fixtures were relocated or eliminated to provide a more efficient lighting pattern.
Other services include hydraulic analysis, environmental documentation, public involvement, and construction engineering. Additionally, as part of the mitigation for removal of the existing structure, KLJ prepared the Historic American Engineering Record document, preserving the original bridge in writing and photographs for future generations.
A new, wider Marsh Arch bridge was constructed. The new bridge was designed in strict conformance with the original Marsh Arch patent and received numerous awards including the ND Ready Mix Association Excellence in Concrete, ND ACEC Excellence in Engineering and ND APWA Public Works Project of the Year–Large Communities. KLJ also prepared and presented a paper on the project at the International Bridge Conference in Pittsburgh, PA.