The $26.2 million rehabilitation of three aging MTA Long Island Rail Road bridges in Hampton Bays is getting underway next month, a major East End infrastructure improvement financed by the Federal Transit Administration and the MTA Capital Program.

The work on the North Highway Bridge, the Montauk Highway Bridge and the Shinnecock Canal Bridge, all constructed in the early part of the 20th Century, will take two years to complete and is expected to extend the life of each bridge by 35 to 40 years.

“Rebuilding these bridges, the oldest of which has stood for more than 100 years, will provide a much-needed boost to the economy on the East End of Long Island by creating construction jobs and making travel on the Montauk Branch smoother and more reliable,” said LIRR President Helena Williams. “It also signals the MTA’s long term commitment to improving service on the East End and the importance of sustaining the MTA Capital Program to finance that effort beyond 2014. Transportation is a key to the future growth of eastern Suffolk County.”

The reconstruction will be carried out in large part over the next two years by a private contractor who will employ approximately 45 workers at the height of the project. The Long Island Rail Road’s own work force will simultaneously carry out a number of supportive assignments.

On Wednesday, the MTA Board will consider the LIRR’s proposal to name the construction and engineering firm Conti of New York, LLC as the project’s general contractor with the award of an initial $10 million contract. Conti is a century-old company with infrastructure projects worldwide and is currently rehabilitating bridges for MTA Bridges & Tunnels and the New Jersey Turnpike Authority. The firm was selected after a competitive bidding process that involved seven construction firms.

The LIRR’s North Highway Bridge was built in 1907, the Montauk Highway Bridge in 1929 and the Shinnecock Canal Bridge in 1931. Based on routine bridge inspections, the LIRR determined that these bridges were in need of rehabilitation.

“They are showing their age, no question about it.” Williams said. “So it’s important that we reverse that. The project will help ensure reliability and on-time performance on the Montauk Branch.”

LIRR inspections found that the superstructures of the bridges are in fair to good condition, but in need waterproofing and painting. The substructures of the bridges, including abutments, wing walls and pedestals, are in poor to fair condition. All deteriorated superstructure and substructure elements will be repaired. The above-deck waterproofing, drainage system, bearings and bridge seats will be replaced. Additional work includes painting and other site improvements.

As part of the repairs, the vertical roadway clearance of Montauk Highway and North Highway Bridges will be increased by approximately 5 inches to reduce the potential for today’s larger trucks and buses to strike the bridge overhead. This is an improvement the Railroad is making during all bridge modernizations where necessary.

For generations, the LIRR has played a key role in the growth of eastern Long Island, especially the popularity of the Hamptons and Montauk as a vacation destination on the South Shore and, more recently, the rebirth of the North Fork as a popular vacation and weekend destination highlighted by the growth of the wine industry and other popular family attractions. The Montauk Branch carries 5,490 passengers on an average weekday, with ridership swelling to nearly 8,000 at high points during the summer months.

President Williams said the work on the Hampton Bays bridges will impact service from time to time, including two 72-hour weekday outages in October in which buses will replace trains between Speonk and Montauk. In the coming days, the LIRR will detail the October outages and its plans for alternative service.

“As with all of our maintenance projects, our goal is to perform the work during the hours that will affect the fewest customers,” said Williams.