To support economic development in the area, the Indiana Department of Transportation (INDOT) decided to replace 35 miles of old SR 25, a 2-lane rural highway with a 4-lane limited access freeway, since it represented a major commercial corridor for farmers wishing to move their supplies to market. Lochmueller Group (Lochgroup) was selected to design the Central Segment, consisting of 8.5 miles.
This portion generally crosses farmland and wooded terrain, some of which were home to Native American tribes and pioneers. As such, this section involved a number of complicated environmental and context-sensitive issues. While primarily a limited-access facility, the Central Section also features several at-grade intersections, as well as a diamond interchange at US 421, 17 bridges, and accommodations for a historic trail overpass.
Upon notice-to-proceed, Lochgroup r suggested several changes to provide for more efficient horizontal and vertical alignment. Several of these changes significantly reduced the amount of stream mitigation required. Lochgroup obtained the additional information in the Final Environmental Impact Statement to document these changes, assessed the impacts, and the required mitigation.
Among the suggested changes to alignment was relocation of a connector road to an extension of CR500N in order to significantly reduce impacts to a wetland at Robinson Branch. The wetland is unique in that it relies on seeps from a nearby bluff to support its habitat. Since this rare type of wetland had never been mitigated in Indiana, Lochgroup suggested changing the alignment of the connector road to be able to bridge the wetland seeps and avoid potential delays associated with permitting. The resulting twin 6-span bridges total 755 feet with span lengths controlled by the location of wetlands on the south spans and the location of a meandering branch on the north spans.
Situated in a low-lying area with poor soils surrounded by high bluffs, the area near Delphi posed several technical challenges requiring rock cuts, soil replacement, and a complex railroad crossing. In addition, the new road passes near the Deer Creek Valley Rural Historic District that served as a home to early settlers of the region. Given the rich history of the area, local residents and preservation groups had a number of concerns with regard to visual, cultural, and environmental impacts.
For this reason, a Citizen’s Advisory Group (CAG) was formed to help develop Context Sensitive Solutions (CSS) in addition to the corridor-level public involvement meetings. This was the first major project where INDOT used the CSS process. Among the stakeholders involved were the Deep Creek Valley Rural Historic District, the Carroll County Historical Society, the Historic Bridge Coalition, the Wabash & Erie Canal Association, Delphi Historic Trails, the Delphi Preservation Society, the city of Delphi, Carroll County, Indiana Department of Environmental Management, Indiana Department of Natural Resources, Federal Highway Administration, US Fish & Wildlife Service, and the State Historic Preservation Officer (SHPO).
The CAG identified key areas of concern: 1) design of the bridge near the historic district; 2) design of the roadway near the valley toward CR 300N; 3) the intersection with extended Main Street; and 4) connections to trailheads.
After meeting with various stakeholders, state and local agencies, local preservation groups and the SHPO, Lochgroup designers researched options for a the bridges over Deer Creek (505’) and Bridge Creek (300’) to identify solutions that would be both aesthetically pleasing and enrich the surrounding natural historic area. Lochgroup then presented several alternatives for piers and railings to the CAG that had been used on federally-approved projects in other states.
As a result the final design of the bridges features unique piers using a “faux” arch design using textured, colored concrete to match the blue-gray slate of the surrounding bluffs. A new type of bridge railing was also used to allow for more visibility to scenic vistas while crossing the bridge. Decorative lighting was designed on Main Street in Delphi from Robinson Branch to SR 25.
Another outcome of the CSS process was the inclusion of piers that support a historic Pennsylvania through-truss historic bridge relocated from Freedom, Indiana. The bridge spans SR 25 to link the Monon Trail which runs adjacent to the historic district.
The northern part of this area also required single-span composite steel plate girder bridges over the Norfolk Southern Railroad. Since the roadway alignment follows a horizontal curve with a 2,650-foot radius, the structures were built along the long chords. The northbound structure has a span length of 131 feet with a skew of 56°31’08” and the southbound structure has a span length of 120 feet with a skew of 54°00’39”.
To incorporate the new roadway alignment and in preparation of old SR 25 being relinquished back to the county, a number of revisions were also made to local roads at the request of local officials.
Originally scheduled to be let as one construction package, this Section was divided into smaller packages to initiate construction while allowing more time for permitting, coordination, right-of-way, and requested revisions by local public agencies. Smaller construction packages also allowed more local contractors to bid on the project. Despite various scope changes, Lochgroup exceeded the initial letting schedule by more than 2 months.