Micropile Bridge Substructure Replacements: Innovative Approaches to Overcoming Unique Design and Construction Challenges through the Design/Build Process

Replacement foundation installations for three of the six bridge locations along the Saw Mill River Parkway included under a New York State Department of Transportation (NYSDOT) design/build contract presented significant challenges for the project team. At two of the locations, the existing columns supporting the traffic deck were founded in the middle of a river directly beneath historic stone arched bridges carrying local traffic. During a storm event, tree limbs and other debris would catch against the columns, forming dam structures sufficient to cause local community flooding. Micropiles were selected to replace the river bearing columns and abutments and also to provide lateral restraint for support of the above roadway and embankment. Design and installation of the micropiles at these locations demanded an innovative approach to technical challenges. This paper will discuss the solutions to the challenges presented at all three locations, the technical success of which was a direct result of close collaboration and cooperation by all members of the design/build team throughout the work.