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I-430/I-630 Big Rock Interchange

Bridgefarmer developed the conceptual, schematic and final design for this, the largest and most expensive project that the Arkansas Highway and Transportation Department (AHTD) has ever let. The concept consisted of developing several alternatives for the AHTD to be able to compare and choose the best alternative. Extensive coordination was involved with regional planning agency Metroplan, City of Little Rock and local businesses including Baptist Medical Center.

The existing I-430 and I-630 two-level interchange in western Little Rock was an urban interstate to interstate cloverleaf design, which tended to back up traffic during both morning and evening rush hours. This single portion of highway interchange sees in excess of 180,000 vehicles in a single day and is one of the busiest intersections in the state. In order to improve the Level of Service (LOS) from E and F to LOS C and D for projected traffic volumes to the year 2025, Bridgefarmer designed a

four-level complex interchange with flyover direct connectors and cloverleaf ramps.

Revisions were made to the design and detailing of several bents’

foundations to address unforeseen geologic conditions, mainly a large rock

formation of hard sandstone in the southeast quadrant of the interchange that

was partially uncovered during construction. Using explosives to remove the

house-sized rock was out of the question due to its proximity to the Baptist Health Medical Center hospital. The contractor attempted to chisel away the rock, which rated 7 on a Mohs scale of 1 to 10, using their heavy construction equipment, but with little success. The decision was made to leave the unique and distinctive formation in place as a landmark, giving rise to the popularly adopted name, “Big Rock Interchange.”

 

Project Construction Cost: $135 Million

Completion Date: 2015

Client: Arkansas Highway & Transportation Dept.