New Mississippi River Bridge Crossing Project: A Case Study

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The New Mississippi River Bridge Crossing project in St. Louis, IL, presented a unique set of challenges and required innovative solutions to map underground utilities across approximately 23,000 feet of terrain.

This case study details the work undertaken by a Subsurface Utility Engineering (SUE) consultant for the Illinois Department of Transportation (IDOT) District 8, highlighting the methodologies employed, the challenges faced due to the project's location and the absence of utility records, and the coordination efforts with multiple railroads.

Project Overview

The project area included a significant portion of unimproved land over a landfill, for which no utility records were available.

The task at hand was to identify both metallic and non-metallic utilities to prevent any disruptions during the construction of the new bridge crossing the Mississippi River.

The project's complexity was further heightened by the need to coordinate with several railroads that intersected the project area, necessitating a high level of precision and communication.

Methodologies Employed

To tackle the absence of utility records and the diverse nature of utilities (both metallic and non-metallic), the SUE consultant employed a range of utility search and trace techniques. These included, but were not limited to:

  • Electromagnetic Locators for detecting metallic utilities.
  • Ground Penetrating Radar (GPR) for identifying non-metallic utilities.
  • Acoustic Locators for pinpointing underground pipes and conduits.

This comprehensive approach ensured that all possible utilities, regardless of their composition, were accounted for during the preliminary stages of the project.

Challenges and Solutions

Lack of Utility Records
The absence of utility records for the landfill area posed a significant challenge. To overcome this, the team employed a variety of search and trace techniques, ensuring a thorough investigation of the site. This proactive approach allowed for the identification and mapping of utilities that would otherwise have remained undetected.

Coordination with Railroads
The project's location required meticulous planning and coordination with several railroads. Navigating these logistical hurdles necessitated clear communication and scheduling to ensure that the utility mapping efforts did not disrupt railway operations. This coordination was paramount in maintaining the safety and efficiency of both the SUE activities and the ongoing railroad operations.

Impact and Outcomes

The New Mississippi River Bridge Crossing project exemplifies the importance of SUE in infrastructure projects, especially in areas with complex underground environments or lacking comprehensive utility records.

The successful mapping of approximately 23,000 feet of utilities, in a challenging and unimproved area, highlighted the consultant's ability to adapt and employ a variety of techniques to ensure the project's needs were met.

Moreover, the effective coordination with multiple railroads set a precedent for how such projects can be managed in the future, showcasing the necessity of collaboration among different stakeholders in infrastructure projects.


The New Mississippi River Bridge Crossing project underscores the critical role of SUE consultants in navigating the complexities of modern infrastructure development.

Through innovative methodologies, proactive problem-solving, and effective coordination, the project achieved its utility mapping objectives, laying the groundwork for the successful construction of the bridge.

This case study not only highlights the challenges faced during such projects but also the strategic approaches that can lead to their successful resolution.

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