One block and two block wide alignments were studied and three grade concepts were considered for the freeway. The below grade concept included tunnels under the Union Pacific Railroad (UPRR) yards. However due to high ground water table and numerous utility lines in the project area, the depressed grade concept was dropped. The at-grade proposal required bridge structures for side streets and pedestrians. The large number of structures needed to accommodate the sloped approaches for these spans resulted in this option being discontinued.
Interstate 80 east from the Central Avenue Interchange with U.S. 85/87 was not completed until 1977. Options considered for modifying the half opened diamond interchange with Central Avenue for I-180 included a full cloverleaf, a folded diamond, and a directional interchange. The directional interchange was discarded due to terrain conditions at the site.
Prior to construction of Interstate 180, Central Avenue consisted of a two lane street and a narrow viaduct over the Union Pacific Railroad yards with two 14 foot wide lanes and 6.5 foot wide sidewalks. The Riner Viaduct was constructed in 1929 and maintained by the city of Cheyenne and the UPRR until the 1950s, when legislation passed shifted maintenance responsibilities to the Wyoming State Highway Department.1
A new viaduct connecting with the Central Avenue/Warren Avenue couplet was included in the 1965 recommended transportation plan for the Cheyenne Urban Area. Traffic volumes were high enough that a four lane facility was required. The Wyoming State Highway Department requested Interstate status for the improvement on November 27, 1967. Received on February 2, 1968, the new facility was to be a limited access highway with no at-grade intersections.1 I-180 was added to the Interstate system by the American Association of State Highway Officials (AASHO) on June 30, 1970.
The report covering the Central Avenue Corridor Study was submitted to the Federal Highway Administration (FHWA) on September 2, 1970. It specified that the proposed improvement be constructed as a freeway with full access control and that the Central Avenue Interchange be rebuilt as a cloverleaf. Following a right of way centered on Central Avenue between Capitol Avenue and Warren Avenue, the facility north from I-80 would be elevated to the UPRR yards, where it would partition into separate structures to 16th Street at Central and Warren Avenues. Service roads would also be built and an extra right of way would provide a buffer on either side of I-180.1
The elevated grade concept was proposed because it would cause the least community disruption, minimize impacts to utilities, and allow existing streets to remain open. The FHWA denied approval for the freeway on December 14, 1970 due to the cost, which was estimated at $16.77 million for the overall project.1
A subsequent corridor study evaluated how to build the improvement at a lower cost while still serving public needs. A report on the study was submitted to the FHWA on February 11, 1971. The facility was redesigned from a fully access controlled freeway into an expressway permitting access at designated points. The change was made on assumptions that full control of access and a free flow interchange at the south end would not be required, building an elevated structure was cost prohititive and that it would be uneconomical to purchase a two block area for right of way.
Interstate 180 was outlined as follows:1
- Construct the facility as an at-grade, controlled access expressway south of the UPRR yards with access limited to two major street intersections.
- Modify the existing Central Avenue Interchange by adding a free flow right turn lane from I-80 west to I-180 north.
- Provide signalized intersections at 5th and 9th Streets.
- Repurpose Central and Warren Avenues as service roads.
- Build an elevated structure over the UPRR yards that diverges with one branch to Central Avenue at 16th Street and the other at Warren Avenue at 16th Street.
- Landscaping the right of way.
Using the existing Central Avenue Interchange reduced the right of way needed. Adding traffic lights provided adequate safety for motorists while the free flow turn from I-80 west to I-180 maintained mobility. With the expressway concept estimated to cost $8.63 million, overall costs for the I-180 improvements were reduced by $8.1 million. FHWA granted location approval for the route on March 11, 1971.1
The I-180, Cheyenne Interstate Spur: Environmental Impact Statement (EIS) submitted on April 14, 1975 indicated that the Wyoming State Highway Department intended to start construction in 1978 and finish work in 1984. Covered by Federal-aid Interstate funds matching state funds, costs were estimated at $14.25 million.
Construction for Interstate 180 got underway in 1977 with expansion of U.S. 85 (Central Avenue) to four lanes. The at-grade expressway was completed in 1979.2
Work on the replacement of the Riner Viaduct started in May 1980. The first span across the UPRR opened to traffic in 1982, at the same time shields for Interstate 180 were erected along Central Avenue. The second span was completed in Spring 1984.2