The tunnel is 4,800 feet long from portal to portal, and it was built by the immersed sunken tube method, comprised of 15 prefabricated segments each 300 feet long and with two 2-lane bores, placed by lay-barges and joined together in a trench dredged in the bottom of the harbor, and backfilled over with earth. Four percent (4%) maximum grades are utilized in the tunnel, and a 60 mph design speed. The traffic lanes in the tunnel are 13 feet wide, with 2.5-foot-wide ledges on either side of the roadway, and with 16.5 feet of vertical clearance from the roadway to the ceiling. The current shipping channel above the deepest part of the tunnel has 800 feet of horizontal width and 45 feet of vertical depth below the average low-tide water level, and the tunnel was designed and built deep enough to allow for a future enlargement of the shipping channel to 1,000 feet of horizontal width and 55 feet of vertical depth below the average low-tide water level.
Monitor-Merrimac Memorial Bridge-Tunnel
관련 Link : Load to the Futere