I-255 FROM IL-162 TO I-270
CONSTRUCTION COST: $32,000,000
COMPLETION DATE: 1989
CLIENT: ILLINOIS DEPARTMENT OF TRANSPORTATION

Two miles of new 6-lane interstate, plus a major interchange with existing I-270 and improvements to 4 miles of I-270. Our services included:

Aerial mapping was provided by client with supplemental topographic survey performed by in house staff. Property and right of way surveys and right of way staking were completed by in-house staff and a sub-consultant.

Significant maintenance of traffic was required for this project due to heavy volume on I-270. Design included widening of existing I-270 on both the outside and in the median and resurfacing of the existing driving surface.

The project incorporated aesthetic guidelines for the design of all visual elements in the highway complex (including bridges, sign structures, fencing, guardrail, landscaping and grading). The firm had previously developed these guidelines for the entire Illinois section of the 25-mile interstate by-pass around St. Louis.

Two major bridge structures were designed as part of this project, both of which crossed existing I-270. Seismic analysis of structure design was necessary due to project location in Seismic Performance Category B.

The I-255 / I-270 interchange included a major two-lane, high-speed directional ramp and collector-distributor roadways. The design was phased to allow construction of a partial interchange that could be expanded as I-255 was extended north. Also included was the reconstruction of two ramps at the I-270 / IL-157 interchange east of the project.

Design included analysis of County Ditch at the crossing of I-270 and it's downstream capacity for the addition of several new drainage ditches to improve drainage on adjacent property. Studies included compensatory storage for flooded areas occupied by roadway fill.