The bridge is owned by the Terminal Railroad Association of St. Louis (TRRA) and was completed about 1890.  Aging and deterioration of the original structure required replacement of three east and three west approach spans in 2005.  Studies were undertaken in 2015 to replace the main truss spans across the river and seismically retrofitting the main piers.  

Over the past two decades, Shannon & Wilson’s Saint Louis office has been providing geotechnical and environmental services for the Merchants Bridge while working with Modjeski & Masters and TRRA.  Projects have included the deck truss replacement for the east and west approaches and the preliminary investigation for the main span replacement.

Geotechnical services included explorations, laboratory testing, engineering analysis and design recommendations for deep foundations and seismic design, and preparation of geotechnical reports.  

Environmental services included an assessment of potential impacts to Waters of the U.S. and completing a NEPA Categorical Exclusion report which included coordination with the Missouri and Illinois State Historic Preservation Offices for a Section 106, addressing potential impacts to threatened and endangered species, and determination of the bridge’s eligibility for the National Register of Historic Places.