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Replacement of Historic Broad Street Bridge (U.S. Route 206) over Assunpink Creek

Location: Trenton, New Jersey

Client: AECOM

Phase: Preliminary Engineering

Status: Preliminary Engineering Completed


This project entailed the replacement of one of two adjoining stone arch culverts that carry Assunpink Creek under Broad Street (U.S. Route 206) in downtown Trenton, New Jersey.  AECOM was the lead design consultant for the NJDOT.  KMA was retained by AECOM to design a plan of excavation to allow access to the underside of the historic stone arch structure.  KMA was also responsible for performing subsurface utility engineering (SUE) and supplemental survey to support the design work.

KMA, in conjunction with a construction contractor, designed and built a box structure that was advanced in three-foot lifts to a depth of twenty feet below grade; the purpose of which was to allow access to structural engineers and cultural resource specialists to the underside of the arch culvert for inspection and photo documentation.

SUE work included locating underground utilities by two methods: utility designation and test holes.  Designation was performed with electromagnetic methods (pipe locators and duct rodders) to determine the approximate horizontal location of underground utilities.  The results of the designation work were compared with preliminary design plans to identify areas of potential utility conflict with underground project features, such as stormwater pipes.  Excavations were then done using the vacuum excavation method to exact horizontal and vertical locations of underground utilities.

Supplemental survey work included location of stormwater drainage structures (e.g., inlets and pipes) in the project area.