Metro North Embankment Stabilization at Milepost HU43.8, Cortlandt Manor, N.Y.

Photo by Rob Culver, Kiewit Infrastructure Co.
Photo by Rob Culver, Kiewit Infrastructure Co.

This $6-million project—a major component of Metro North's capital program aimed at improving the track along its Hudson River Line—involved stabilizing a 150-ft section of shot rock-filled railroad embankment.

The work was planned long before Superstorm Sandy flooded 30 miles of the Hudson Line, causing erosion to the track bed and damage to the tracks and signal system. For decades, slope failures have occurred along the line in the region.

The embankment extends nearly five miles along the east side of the Hudson River and supports two rail tracks that sit on a thin rocky ledge that was blasted from the rock more than a century ago.

Work included designing and installing 20 4-ft-dia drilled shafts through the rock fill embankment. The shafts were drilled 45 ft deep just above the high-tide line.

A smaller drill in the center of each shaft was used to anchor an even deeper core beam in the bedrock, and each ring was filled with concrete. The row of rings was linked together with concrete panels.

As the foundation of this permanent seawall system, the drilled shafts were used in conjunction with a tieback and continuous steel waler system that ultimately stabilized the track section.

Worker access and equipment placement challenges arose from the site's proximity to the water and difficult terrain. The team worked from a customized barge that cantilevered a working platform out over the river and enabled the contractor to position equipment closer to the embankment. The effort prompted one judge to call it an "elegant solution."

During construction, the embankment required protection from wave erosion effects, so temporary erosion mats were used to maintain its integrity.

The project was completed within 11 months—two months ahead of its original schedule.

Key Players

Owner Metro North Railroad

General Contractor Kiewit Infrastructure Co.

Lead Designer GeoDesign Corp.

Project Manager/Resident Engineer/Sr. Inspector A. DeCesare Associates