Expert Insight

LIRR Post Avenue Bridge
orchestrated precision

Infrastructure Engineering Firm
Gerard Bartucci, PE

A historic transformation of the Long Island Railroad has recently been underway to strengthen the region’s transportation infrastructure and usher in a new era of economic growth starting with LIRR Post Avenue Bridge. According to NY Governor Andrew Cuomo, “The LIRR is the backbone of the region’s economy, and the strength and resiliency of Long Island requires bold, transformative investments to bolster our transportation network. By rebuilding the LIRR Post Avenue bridge and paving the way for the historic Third Track project, we are showing that it’s possible to upgrade the rail on time, on budget, and with community input at every step of the way. While others talk about infrastructure, New York is getting it done”. With the complete renovation of the LIRR line, New York has aimed to make significant upgrades to its infrastructure and service, incorporating the considerations of the community throughout the entire scope of the project. 

As part of the LIRR upgrades, the Third Track project was approved to add a tertiary track to 9.8 miles along the congested Main Line of the LIRR between Floral Park and Hicksville. The first completed project initiative since the Main Line Expansion Project has been the Replacement of the Post Avenue Bridge in Westbury, NY.

History of LIRR
Post Avenue Bridge

LIRR Post Avenue Replacement Bridge LIRR Track Addition SMPT
SMPT Removal of Old Bridge with lower clearance.  
Originally built in 1914, The LIRR Post Avenue Bridge was a 63-foot single span structure carrying two tracks supported by steel thru plate girders with a concrete deck and reinforced abutments made of concrete. The 100+ year structure has been a conduit for train traffic that cars and buses pass under with an original roadway clearance of only 11 feet 10 inches. The dimensions had made it extremely vulnerable to vehicular strikes, particularly from trucks failing to clear the underpass. Although still considered in good condition, the bridge was struck over 80 times, causing numerous train and roadway delays in both directions.


LIRR Post Avenue Replacement Bridge LIRR Track Addition
New Bridge being lifted off shoring and onto SMPTs.

The proposed replacement of the bridge encompassed strengthening and repairing the existing abutments, relocating the existing overhead utilities, constructing new retaining walls to accommodate the new track profiles, raising the existing station platforms and replacing the existing stairs from parking lot to the platform. However, there were three distinct challenges that required extensive orchestration efforts.

1 First the new bridge needed to be 13 feet wider than the existing structure in order to accommodate the Third Track.

2 Second, the clearance of the bridge needed to be raised to the state DOT standard of 14 feet to eliminate bridge strikes at the location.

3 Third, the bulk of the replacement work needed to be completed within 48 hours to minimize any disruption to the community.

Design-Build of
LIRR Post Avenue Bridge

McLaren Engineering Group in association with Halmar International was awarded the $9.7 million Long Island Railroad design-build contract for the replacement of the Post Avenue Bridge. As engineer-of-record, McLaren was responsible for completing the final design by expanding preliminary work developed during the RFP process. McLaren was tasked with designing the replacement of the two-track bridge with a three-track bridge and increasing the vertical clearance to 14 feet to reduce outages. The team effort required extensive planning and precision to keep the project on schedule and within budget.
LIRR Post Avenue Replacement Bridge LIRR Track Addition
Bridge assembled in adjacent parking lot.

Five months prior to replacement, the bridge superstructure began to be assembled in a parking lot adjacent to the bridge on temporary shoring towers in order to minimize rail disruptions. As part of this design-build contract, McLaren was responsible for completing the final design in order to provide LIRR with the most economical design with the least amount of impact to the community. The new bridge was installed entirely during a 48-hour weekend track outage. Throughout this meticulously planned 48-hour period, the existing bridge superstructure was rolled out and the new superstructure was rolled into its new position via self-propelled modular transporters (SPMTs) from the adjacent parking lot. Crews from Halmar International, Inc. worked around the clock using a unique construction method with a remote-controlled lifting device. That transporter lifted the 103-year-old bridge, which remained intact after it was cut away from its connection to the abutments, and placed into an adjacent parking lot. The contractor then had to modify the abutments to support the new bridge height. Then, the new bridge was lifted, in its entirety, and put into place over the roadway.

LIRR Post Avenue Replacement Bridge LIRR Track Addition
New bridge being put into place on SMPTs.

Work was completed in just 36 hours, all timed down to the minute to ensure no disruptions to the first train of the Monday morning rush hour. Additional work to fully complete the project included adjustments to the station platforms, installation of stairs and concrete painting and sealing work. The roadway underneath the bridge is being re-graded to provide improved sight lines for motorists, enhancing safety and meeting the latest design standards and requirements of the New York State Department of Transportation.

The LIRR Post Avenue Bridge is now 50 feet wide — 13 feet wider than its predecessor — a width that allowed for a section of third track to be placed with a clearance of 14 feet. Traffic disruptions were minimized and a strategic plan to accommodate commuters during the 48-hour rail shutdown was accomplished. The industry-wide collaboration of many moving parts proved to make the entire project a huge success.
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Header photo credit of Metropolitan Transportation Authority of the State of New York Creative Commons — Attribution 2.0 Generic — CC BY 2.0

Award Winning Project

2020 Engineering Excellence Platinum Award in Category C: Structural Systems by the ACEC New York

2018 Project of the Year by the American Society of Civil Engineers, Long Island Branch