Phase II Engineering for US 6/IL 7 from Will Cook Road to West of US 45

Lochner was selected to provide the Illinois Department of Transportation (IDOT) with Phase II engineering services for the widening and reconstruction of approximately 2.5 miles of US 6/IL 7 (159th Street) from Will Cook Road to west of US 45 (LaGrange Road).

The existing two‐lane roadway is being reconstructed with a four‐lane cross section consisting of two 12‐foot lanes in each direction, a 28‐foot‐wide landscaped center barrier median, curb and gutter at the outside edges of pavement with a closed drainage system, and two 10‐foot, shared‐use paths.

Lochner prepared plans, specifications, and cost estimates for the roadway reconstruction, the reconstruction of four dry land bridges (with the longest bridge being 800 feet long), the replacement of bridges over Spring Creek and Marley Creek, the construction of new retaining walls (over 3,000 feet), drainage design, maintenance of traffic, railroad crossing design, and traffic signal modernization of US 6/IL 7 in Orland Park.

The project included Phase II drainage design and verification of in‐line detention, inlet spacing, ditch design, two multi‐cell box culverts, and layout of two compensatory storage basins. Box culverts designs showed embedment within the existing channel and flanker cells to meet permitting requirements. The project impact to existing wetlands was minimized but is over the one‐acre threshold so an individual 404 permit has been prepared and submitted to the U.S. Army Corps of Engineers.

The structural elements were designed with consideration of two key factors. The first factor was a large, deep existing layer of peat necessitating the land bridges, which also required careful design of foundation type and pile selection for a significant segment of the project. The second factor is the repetitive nature of the land bridge and retaining walls in this segment. The design was standardized for certain structural elements, providing consistency and streamlining design, review, and construction.

Three intersections were designed for reconstruction: Wolf Road, 108th Avenue, and 104th Avenue. Staging the intersection improvement considered the local commercial properties. The intersection of 104th Avenue is pile‐supported due to the poor soil conditions

Lochner worked closely with IDOT and the utility companies to identify conflicts prior to completing the design. Lochner also worked with IDOT and the Village of Orland Park to identify conflicts and provide bicycle/pedestrian accommodations tying the roadway improvement to local parkland.