Underwater Bridge Inspection & Survey

Underwater Inspection, Fathometric Survey & Multibeam Survey of Marine Parkway Bridge & Underwater Inspection of Cross Bay Bridge

New York

In 2012 W.J. Castle, P.E. & Associates, P.C. completed the underwater inspection, Fathometric Survey, and Multibeam Survey of Marine Parkway Bridge, BIN 5521240 which is a vertical lift bridge connecting Queens and Brooklyn, NY.  As requested by MTA, an addition in-depth inspection of the fender system was performed which included the timber sheets, walers and bracing as well as steel sheet cells and all hardware connections. NDT Testing was performed on the steel cells to determine the extent of deterioration. Due to the scouring of the channel bottom and fluctuations in depths over the previous years’ findings, TBTA requested a multibeam survey this cycle to more accurately evaluate the scouring conditions. This data also aided in the preparation of scour remediation plans to ensure that the countermeasures be designed in the correct locations and in the quantities needed to protect the bridge from future scouring. The hydrographic survey and multi-beam survey were done on a 20 foot grid extending from shoreline to shoreline and approximately 150 feet from each fascia. Water depths ranged from less than 10 feet up to 60 feet deep. Volumetric changes between the current channel bottom and the previous years’ findings were calculated as part of this contract.

The underwater inspection of the Cross Bay Boulevard Bridge was also completed at this time. The Cross Bay Boulevard Bridge, B.I.N. 5521239 consists of 17 spans and four approach ramps on the south end of the bridge.  These approach ramps are considered separate bridges and were documented in separate reports as per MTA requirements. Cross Bay Boulevard, at the span’s northern end, runs through the Jamaica Bay marshes while the southern end leads to the Rockaway Peninsula.

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