COMPLEX GEOLOGIC DRILLING CONSIDERATIONS FOR A TUNNEL UNDER THE HUDSON RIVER FROM NEW YORK TO NEW JERSEY

A mega construction geotechnical engineering project, a tunnel under the Hudson River from New Jersey to New York is being planned south of the original 100-year-old North River Rail and Lincoln Tunnel ( 34 Street) in Manhattan, and is known as the Hudson Tunnel Project (Gateway) . The purpose of this presentation is to describe the drilling strategies and risks affecting the complex associated geology.

NYC is near the southern end of the Northern Appalachian Mountains and was effected by the Taconic Orogeny during the Ordovician Period about 444-485 million years ago. NYC's bedrock are metasedimentary schists and gneisses mostly Cambrian and Ordovician .New Jersey is affected by Triassic rifting forming the Newark Basin and associated Palisades sills .The Hudson River formed between 16000 and 22000 years ago.

Detailed mapping of the planned Hudson Tunnel Project (Gateway) is directly applied to the drilling strategy design specifically with respect to the efficient utilization of the Tunnel Boring Machine ( TBM ). Drilling will originate in NJ ( west) of the Hudson River diabase, an igneous fine grained rock, containing metamorphosized hornfels lenses from the Lockatong Formation and xenoliths of sandstones from the Stockton Formation. The blocks are a mixed face drilling execution risk due to a change in material strength ,with respect to potential TBM malfunctions and cutter head replacements .Continuing on the N.J. side the planned drilling will encounter Ordovician Period serpentines and the Waloomsack Formation pyritized schist before entering unconsolidated silt and clay, 20 feet,below the Hudson River channel. The tunneling will enter the NYC side , in Manhattan, penetrating Paleozoic bedrock below the bulkhead