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Thursday, 24 September, 2015

Indian River Inlet Bridge


The Indian River Inlet Bridge (IRIB) spans the Indian River Inlet in Sussex County, DE, and carries Delaware State Route 1 (SR-1). In April of 2002, the Delaware Department of Transportation (DelDOT) decided that a replacement for the existing IRIB was warranted. Shortly thereafter, DelDOT began the design of the IRIB Project comprised of a new bridge structure and approach roadways.

DelDOT awarded a contract for construction of the roadways and approaches portion of the overall replacement project. The roadway and approaches were to be supported by earthen embankments retained by Mechanically Stabilized Earth (MSE) walls. Monitoring during construction revealed that settlements and movements experienced by the earthen embankments and MSE walls were significantly greater than those anticipated. O’C&L was selected by DelDOT to provide a forensic engineering review of the design and construction of the earthen embankments.

O’C&L’s work was performed in two phases: Phase I (Construction and Inspection) and Phase II (Analysis of Design). Phase I focused on DelDOT’s contract administration and quality assurance / quality control (QA/QC) efforts, as well as the contractor’s efforts during construction. Specific tasks performed during this phase included a detailed review of construction documents--plans, specifications, submittals, shop drawings, as-built information--and geotechnical instrumentation data collected during construction. Interviews of key project personnel and inspection staff were conducted and the project documents were categorized, organized and entered into a database. Also during this phase, daily inspection, sampling, and testing were performed on the embankments as they were deconstructed; all were performed in order to determine if proper procedures and materials were used during construction. Phase II focused on the design of the embankments and MSE walls, including the site investigation and design work that was completed to prepare the construction documents for the project. O’C&L was retained to provide expert services in litigation between DelDOT and its designer.

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