Indiana State Route 641 Bypass design
The Indiana Department of Transportation selected Hanson to provide survey and design services for Phase III of the State Route 641 Terre Haute Bypass (S.R. 641). The $31 million Phase III section consists of a 2.1 mile, four-lane divided highway with a diamond interchange at realigned State Route 46. The completed bypass will create a new 6.2 mile, four-lane divided highway connecting Interstate 70 (I-70) with U.S. 41, relieving congestion within Terre Haute and improving motorists’ safety. The construction team is building the roadway in four stages over the course of a few years.
The Hanson design team was asked to complete five alternate preliminary designs within an accelerated schedule. The geometric configuration and an economic analysis of the roads and five bridges were evaluated in each alternate. The selected alternate included a tight diamond interchange with a roundabout at each ramp junction. The roundabout was introduced due to constraints imposed by the Little Honey Creek Floodplain, located north of the interchange. This will be the first application of a roundabout at an INDOT interchange.
Phase III design required a total of five bridge structures. A set of three-span twin structures, in full superelevation, carries S.R. 641 over an unnamed tributary of Little Honey Creek. Another twin three-span, Bulb-Tee carries S.R. 641 over Little Honey Creek. The bridge over Little Honey Creek skews 45 degrees. The grade separation bridge carries S.R. 46 over S.R. 641 and is a two-span bridge connecting the roundabouts at the ramp junctions.
Both twin bridges required floodway construction permitting approval from the Indiana Department of Natural Resources and Federal Emergency Management Agency (FEMA) for delineation of the existing floodplain and floodway of Little Honey Creek — an adjacent stream that meanders in and out of the project corridor.
As part of the overall project, Hanson delineated the existing floodway and floodplain using advanced Geographical Information Systems (GIS) processes coupled with a geospatially correct river hydraulics model for Little Honey Creek and its adjacent unnamed tributaries. This process involved using GIS and river hydraulics modeling software to combine existing statewide terrain data with field surveys. The project also involved post-modeling processes to map the regulatory boundaries and to determine the effect these boundaries have on the alignment of the bypass.
Services provided by Hanson included surveying; scoping; roadway, bridge and traffic design; hydrologic analysis and hydraulic design; right-of-way engineering; and utility coordination.