As a result of Hurricane Irene, a 300-foot-long section of embankment between the Roebling and Bordertown transit stations in NJ failed and partially collapsed onto the NJ TRANSIT River Line tracks and right of way. The failure caused a massive loss of slope and the embankment was left in an unstable condition. Following the initial collapse, the embankment continued deteriorating and moving toward the track. This led to disruptions to transit operations and ultimately shutting down the service until repairs and stabilization could be made.
In order to expedite the recovery, New Jersey Transit awarded an emergency design-build contract to the George Harms Construction/Hardesty & Hanover team. The contract involved fast-track investigation, testing, design and construction – all to be completed within a six-month period. H&H developed the design for stabilizing and retaining the 55-foot-high embankment. The work involved geotechnical exploration, hydrology, slope stability analysis and design of the retaining structures. Due to severe site constraints, the new retaining walls were supported on piles and drilled shafts.
The key design and construction issues included minimizing vibrations during pile installation to prevent further slope failure. In order to address that, steel HP piles were placed in pre-drilled concrete grouted shafts. The design featured a new drainage system, including bio-swales. Other design work included design of construction access and temporary work platforms consisting of mechanically stabilized earth walls.