Consolidated Edison Company of New York Inc. awarded Kiewit Constructors, Inc., a subsidiary of Kiewit Corporation, the $85.2 million Harlem River Tunnel. The project includes two 165-foot-deep circular shafts connected by a 675-foot-long horseshoe tunnel. Bedrock in this part of Manhattan is white marble and found at a depth of about 70 feet below grade. Overburden at the shafts is a mix of sandy and silty soils with support of excavation in the overburden being secant pile walls.
Once in rock, conventional drill-and-blast techniques will be used. Initial rock support consists of 9-foot-long Swellex friction bolts and Shotcrete in most areas, with 15-foot-long Swellex bolts being used in the soil/rock interface and turn under areas.
Following excavation, a continuous PVC lining will be installed. Subsequently, the entire tunnel and shafts will be lined with a final cast-in-place concrete lining. Surface structures such as pulling chambers, a head house and ventilation building will be installed for continued servicing of the utility tunnel.