E2PM has provided civil, geotechnical, structural, and environmental engineering services for the construction of the True Wheel Building project located within Hoboken Railroad Yards, Hoboken, New Jersey.
The project involved dewatering of deep foundations situated in complex subsurface conditions in close proximity to the Long Slip Channel. The geotechnical and structural complexities required special consideration in preparing the dewatering calculations and design drawings. Soil and groundwater contamination was identified within the construction area. The soil conditions at the site were characterized as follows: granular fill over a thin layer of organic silt, followed by several layers of sand mixed with organic silts, glacial sands, till, and ultimately decomposed rock. Groundwater typically ranged between 2.1 to 2.7 feet below ground surface. Groundwater fluctuated due to tidal influence in the area.
The True Wheel Building required the construction of a deep foundation, with its bottom elevation over 18 feet below grade. The high water table and the location adjacent to the Long Slip Channel required extensive braced sheet piling and extensive dewatering to render the bottom of the excavation safe from blow-outs due to the hydrostatic pressure. E2PM analyzed and designed the dewatering system, which included a series of groundwater extraction wells both on the inside of the excavation and outside. The extracted groundwater required treatment before disposal. E2PM also identified the requirements from the treatment of groundwater. A NJDEP temporary dewatering permit was prepared and obtained. E2PM also sampled the groundwater during the dewatering phase. The groundwater extraction was calculated at 90 gpm. Four submerged pumps were designed to dewater the excavation and to keep the groundwater below the bottom of excavation. Observation piezometers were installed to monitor the groundwater elevations during construction.
In addition to the dewatering design of deep foundations, E2PM designed the groundwater treatment system. The system included activated carbon for VOC removal and sediment filters for suspended solids removal. An oil/water separator was available on site to remove any LNAPL. A groundwater sampling program was incorporated to insure compliance with the dewatering permit.