Year constructed: 1958
Bridge type: Steel Continuous Stringer/Beam/Girder
National Register of Historic Places status:
Listed
Length: 320 feet
Width: 52 feet
Spans: 3
FHWA: 031570
Jurisdiction: Iowa DOT
Location: U.S. 6 over the Iowa River in Iowa City, 0.2 mile east of east Jct. Iowa 1, Section 15, T79N-R6W (University Heights Township)
Details
In May 1955, the ISHC began surveying for the possible relocation of Highway 6. Traffic studies conducted by ISHC in the mid-1950s indicated that approximately 38% of the traffic on the highway was through traffic; thus, they recommended that a bypass be constructed to alleviate congestion in Iowa City (Iowa City Press-Citizen , September 24, 1956:1). By the spring of 1956, the route was set along the southern edge of Iowa City from the junction of Highways 1 and 218 to Lower Muscatine Road to the southeast. On December 11, 1956, the contract for the bridge construction was let to A. Olson Construction Company of Waterloo for $223,807 (Iowa City Press-Citizen December 12, 1956:1). In April 1957, work began on the wood pilings for the bridge (Iowa City Press-Citizen April 17, 1957:3). By November 1957, all four concrete piers were in place and work was expected to continue through the winter (Iowa City Press-Citizen November 14, 1957:1).
The US Highway 6 Bridge was included for Phase II evaluation under Criterion A as it was a new bridge built for a relocation of US Highway 6. Registration requirements outlined in the MPD state that a bridge can be eligible under Criterion A if it "established a new highway transportation corridor, and can be shown to have been the direct cause of significant development or changes in land use." A new Proctor & Gamble plant was constructed on Lower Muscatine Road in 1955/56. This, along with the construction of the Highway 6 bypass, caused significant residential, commercial, and industrial developments along the newly built highway corridor. Aerial photographs from the 1950s, 1960s, and 1970s show residential developments mainly north of the new highway. Commercial businesses were constructed along the highway just east of the river as was the Sycamore Mall, constructed in 1966-69. Residential developments also grew significantly on the east side of the city, though that may have been influenced more by topography than proximity to the new highway. In October 1957, the City proposed to annex tracts along the new highway (Iowa City Press-Citizen, October 31, 1957:1). Given these facts, LBG concludes that the US Highway 6 Bridge does meet registration requirements under Criterion A as part of a new highway corridor that was the direct cause of significant development in southern Iowa City. The bridge does not meet any of the other registrations requirements for Type 402 bridges.
The Steel Continuous Stringer, Multi-beam or Girder bridge (Type 402) is in most ways identical to its simple span version with the primary difference being the continuation of the structural member over one or more intermediate piers, and the resultant need for only a single bearing at the intermediate pier rather than two separate bearings (see description of Type 302 above). Riveted, bolted or welded butt splices of the structural members to make them structurally a continuous beam are often located not over the piers but roughly at the third-points of the span where the positive and negative bending moments cancel each other.