Design-Build Replacement of Wreck Lead Bridge Submarine Cables
Location:
Nassau County, NY
Client:
MTA Long Island Rail Road
Contract Value:
$3.8 Million
Project Dates:
December 2015 - May 2018
• Trenching 280 LF, bridge pier to bridge pier
• Submerged submarine armored cables and HDPE ducts
• Installed a protective concrete mattress and backfilled
• Installed and shielded conduit under the bridge deck
• Turned over project, ready for tie-in
• Coordinated with LIRR departments
PROJECT OVERVIEW
The Wreck Lead Bridge is a vital part of the Long Beach branch where trains cross over Reynolds Channel using a single-track bascule bridge and viaduct. The Long Beach branch was severely damaged by Superstorm Sandy. Underwater cables, a crucial component of the bridge, were heavily affected. Following the storm, infrastructure replacement and rehabilitation along the Long Beach branch became vital to ensure that LIRR maintained its service and performance for daily commuters. The contract scope entailed the replacement of power, signal and communications underwater cables located across Reynolds Channel between Long Beach and Island Park as part of storm hardening measures to restore the branch’s infrastructure.
WHAT MADE THIS JOB COMPLEX
The design-build team had to work closely with various LIRR departments to finalize a design that worked for all parties involved and maintained railroad operations at all times. Excavations were required to be performed underwater, and quickly to prevent fill-in by currents in the channel. Marine work is subject to adverse weather conditions including wind, rough waters and extreme tides.
HOW POSILLICO SOLVED IT
Posillico excavated an underwater trench, bridge pier to bridge pier, of about 280 linear feet, and submerged 12 each 2000kcmil armored cables for LIRR’s 750 VDC traction power cable and negative returns, and 3 each armored submarine cables for signals. In addition to the submarine cables, Posillico also submerged 3 each 4” HDPE Ducts and 3 each 6” HDPE Ducts, to house LIRR signal and communications cables. A protective articulating concrete mattress was placed over the cables and the ducts, and the trench was backfilled. Conduit was also installed under the bridge deck and shielded with steel protective plates. Lastly, in accordance with the performance specifications, Posillico terminated the cables on land, installed pull boxes and support, as well as precast concrete manholes at the bridge approaches, all to enable the LIRR to run their cables through the new conduit and connect easily with their existing system. To ensure that the project ran smoothly and was both safe and successful, Posillico coordinated with the Long Island Railroad’s Power, Signal and Communications individual departments to maintain bridge and LIRR operations throughout construction. The team also coordinated with the US Coast Guard to maintain maritime traffic.
