Overview
Horner & Shifrin was the Prime Design Consultant for Phases 1 and 2 for a replacement of the 5,450-ft long dual structures carrying I-270 over the Mississippi River.
Horner & Shifrin completed the preliminary engineering and environmental study to replace the aging mile-long bridge carrying I-270 over the Mississippi River which connects Madison County, Illinois to St. Louis, Missouri. Locally known as the Chain of Rocks Bridge, this bridge is a vital link for the Illinois metroeast and St. Louis metro regions which accommodates over 50,000 drivers per day. Because of the proximity of the Riverview Drive interchange in Missouri to the Bridge, the study required an interchange alternative analysis in order to ensure the proposed bridge improvements fit with MoDOT’s proposed interchange improvements. Over course of the study, continual coordination with both IDOT and MoDOT took place resulting in a streamlined decision-making process during milestones of study.
The study included preparation of a project report, coordination of bicycle and pedestrian facilities, subsurface utility engineering, surveying, location drainage studies, a major river hydraulic report, bridge condition report, interchange alternative analysis, maintenance of traffic studies, regional traffic modeling, HSM safety study, and a crash report. A key event during the study process was a Design Charrette that brought together key decision makers from both State DOTs and personnel from FHWA’s national office. The charrette expedited the study by establishing clear and defined alternatives. In addition, environmental studies were conducted as required by NEPA and multiple Federal and State (IL & MO) environmental regulatory agencies were coordinated with. This coordination included extensive coordination with the U.S Army Corps of Engineers regarding section 404, 10, and 408 permitting. All environmental studies were included and summarized in a federally approved categorical exclusion.
The study’s public involvement utilized Context Sensitive Solutions tools including a Community Advisory Group and Public Meetings. Working with the local and regional stakeholders, CAG members, and listening to the public led to the completion of a successful study and a bridge replacement alternative that will address the public’s key issues and concerns.
The federally approved categorical exclusion report was approved by FHWA on July 11, 2018. The study was completed on schedule and under budget.
H&S completed full design for Units 1 and 2. Unit 1 includes dual 383-ft long 3-span steel plate girder bridges with skewed piers founded on drilled shafts. Each roadway accommodates four 12-ft lanes of traffic with 10-ft inside and 6-ft outside shoulders. Unit 2 includes dual 7-span, 1583-ft long bridges over the river also supported by concrete drilled shaft piers socketed into bedrock. The steel girder framing includes spans as large as 236-ft and features spans of flared girders to accommodate exit and entrance lanes for the Riverview Drive interchange. The rest of the structure is being designed by teaming partners. The bridge is designated as critical and will be designed for seismic performance zone 2 with varying soil site classes.
