Moretrench’s experience and expertise covers a wide range of geotechnical services. This allows the company to offer multi-system solutions under a single contract, providing cost and scheduling advantages to the owner and general contractor. Construction of a state-of-the-art wheel truing facility by VRH Construction Corporation for the Port Authority of New York and New Jersey (PANYNJ) required just such an approach, involving a micropile foundation system, construction dewatering, and design and installation of an earth support system to allow for the excavation of the below-grade wheel truing pit that would house high-precision machinery.
The new structure was to be built at the Harrison Maintenance Facility, immediately adjacent to the existing PATH train maintenance building. The tight, 40 foot by 300 foot site presented significant logistical challenges that Moretrench had to overcome to perform its work.
The owner’s engineer, Parsons Brinckerhoff, had specified 9.685-inch OD micropiles with 40- and 60-ton design capacities to provide the foundation support for the new structure and the truing wheel machinery. Moretrench successfully conducted axial compression load testing in accordance with the plans and stringent specifications of the PANYNJ. Strain gauges were installed in the bond zone of the test micropiles to estimate load distribution and assess the movements of the pile tip. One hundred and thirty production micropiles were installed to depths of 55 to 86 feet below ground surface in interbedded alluvial sands and silts. Due to the narrow width of the site and the large drilling rig required to achieve high production rates, sequencing of the pile installation was critical to completing the project on schedule.
The excavation support, designed as well as installed by Moretrench, was a soldier pile and timber lagging system with both internal ring-wale support and temporary tiebacks to support cuts up to 15 feet deep in the weak surficial soils. The irregular hexagonal shape of the truing pit footprint, coupled with its position immediately adjacent to an operational train car maintenance structure, mandated an extraordinarily high level of workmanship. As construction of the excavation support system progressed, Moretrench installed a temporary wellpoint dewatering system to lower the static groundwater table approximately 8 feet. Careful control of the operational system ensured that there would be no excessive pumping rates that would require special permits, and that settlement of the active PATH rail tracks, only 50 feet away, would not be induced.