Meeting New York Metropolitan area mobility needs is critical to keep pace with growing demand, to achieve the forecasted economic growth, and to maintain midtown Manhattan as a centre of regional, national and global importance. The possibility of insufficient access to midtown Manhattan was recognized as a significant problem, leading to this project major goal of doubling trans-Hudson rail capacity. With a budget of over six billions dollars (2005) and a completion plan by 2016, the Trans Hudson Express (THE) Tunnel project will fulfil these needs. The project faces many technical, environmental, and regulatory challenges including tunnelling under the Hudson River in soft silts and with limited cover; tunnelling through mixed ground in the New Jersey shore; crossing under existing historic bulkhead; tunnelling under high rise buildings in one of the most congested region; constructing a six-track cavern station under 34th Street, one of Manhattan's busiest cross-town thoroughfare; underpinning and supporting existing facilities; maintaining NJ Transit, Amtrak, Long Island Rail Road and New York City Transit operations during construction; and developing the design concepts to meet environmental requirements and regulatory constraints. This paper presents the planning process of the project, the environmental and engineering challenges, and measures taken to address them.
