I-255 EXTENSION
CONSTRUCTION COST: $41,000,000
COMPLETION DATE: 1998
CLIENT: ILLINOIS DEPARTMENT OF TRANSPORTATION

A new 4-lane fully access controlled divided highway extending I-255 3.5 miles north of I-270. Oates Associates had previously designed the last 2 miles of I-255 and the interchange with I-270 as part of another project. Services provided were:

Aerial mapping was provided by client. Supplemental topographic survey performed by in-house staff using electronic data collection equipment integrated into CADD system. Property and right of way surveys and right of way staking were also performed by Oates Associates staff.

The project involved completion of the interchange with I-270 and a new interchange with a county road. Design of highway in American Bottoms flood plain required extensive hydraulic analysis and significant earthwork. Wetlands replacement and compensatory storage design were also included.

The project involved a total of 8 major bridge structures crossing I-270, 2 county roads, one ramp and several streams. One of these structures was a complex 3-span splayed beam dual bridge (shown here). The project location in Seismic Performance Category B required special considerations including seismic analysis of the structures and piles designed for pockets of liquified soil up to 30 feet deep.