The report identifies three alignments for crossing Long Island Sound by bridge, tunnel or a combination of the two. The 177km-long stretch of water lies between New York City and Connecticut to the north and Long Island to the south.

Shortest of the proposed routes across it is a 14.6km western alignment; the longest is about 38km long.

The report, which was prepared for New York State Department of Transportation, was provided to Newsday and published online.

The study rejects some potential alignment options but recommends further study of five:

  • Western alignment – tunnel only
  • Western alignment – bridge/tunnel combination
  • Central alignment to Bridgeport – bridge only
  • Central alignment to Bridgeport – bridge/tunnel combination
  • Central alignment to Devon – bridge/tunnel combination

The bridge-only option for the central alignment is costed at US$13bn to US$16.5bn. The most expensive bridge/tunnel option would be for the western alignment, which is priced at US$43.5bn. Overall, the most expensive option of the recommended ones is for a three-lane tunnel on the western alignment, which is estimated to cost US$55.4bn.

There have been many proposals to span the Long Island Sound over the past decades. The feasibility study process began with the compilation of a long list of possible concepts, including those identified by prior studies dating back to the 1930s. The reasons that many of these concepts did not advance included lack of political support, high cost and community impacts, said WSP. 

The study found that a bridge-only option would be technically viable for both the central and eastern alignments but not for the rejected eastern route. Bridges are less expensive than tunnels, but would result in more environmental impacts, said WSP.