Client
Illinois Department of Transportation
Services provided
Civil engineering
Structural engineering
Surveying
Project overview
With $425 million in planned improvements, Interstate Route 74 required Phase II engineering design for the complete reconstruction of the $70 million, 1.1 mile section from Forrest Hill Avenue to Sheridan Road.
Approach
During the course of the project, STS provided route surveys, six-lane freeway design, two complete interchange designs, five overhead bridges, closed drainage systems, double and triple box culverts, 0.4 miles of drainage flume, 10 retaining walls, city street improvements, traffic staging and maintenance of traffic plans, and all other related improvements. The signal systems also used video detection systems.
STS served as the prime consultant overseeing and reviewing the work of a MBE subconsultant designing two bridges and a large box culvert extension. The complete design of four bridges required PPC I beams and one steel curved girder bridge to span the interstate; the bridges ranged from 174 to 256 feet long. The project also involved the design of several retaining walls, the larger requiring multiple wall types including drilled soldier pile walls with cast-in-place concrete facing. Walls used both free-standing vertical cantilever soldier piles and where appropriate, soldier piles with helical anchor tie-backs.
The structural design rehabilitated a 0.4 mile long, 30-foot wide, 12-foot deep drainage flume in the interstate median. Flume work included rehabilitation, repair and raising the sides three to five feet by placing a mechanically stabilized earth (MSE) wall with a cast-in-place face over the existing flume wall to minimize the bearing pressure on the existing flume walls. The outlet settling basin structure was modified by extending a triple box culvert and the upstream inlet structure was extended using PPC deck beams, supported on piling outside the existing flume walls.
Client benefits
Using a team approach that considered highway and structural engineer input allowed STS to develop solutions that reduced total construction costs. STS' active participation with the IDOT District and Bureau of Bridges offices helped facilitate decision making and kept the project on schedule. |
