Baltimore Harbor Tunnel

The Baltimore Harbor Tunnel is a pair of two-lane road tunnels carrying Interstate 895—the Harbor Tunnel Thruway—under the Patapsco River southeast of downtown Baltimore, Maryland, United States.Route descriptionThe pair of tunnels is 1.45 mi. 7650ft long, stretching from the south shore of the Patapsco River to the north shore near Dundalk. Each tunnel is 22ft wide and 14ft high, and accommodates two lanes in each direction. The maximum speed within the tunnel is 50mi/h.Both portals have ventilation buildings, with a total of 32 fans in place to replace the air within the tunnels, which is drawn in through the tunnel floors and exhausted through the tunnel ceilings. The tubes themselves range from a depth of 50ft below ground to 101ft below ground.The tunnel and Thruway are operated by the Maryland Transportation Authority, which currently charges a toll of $4 for cars in both directions. Tolls may be paid with cash or with E-ZPass.HistoryThe tunnel and approaches were designed by Singstad and Baillie, a New York-based engineering firm specializing in tunnel design, in association with the J.E Greiner Company, a local Baltimore-based firm. The tunnel was formed out of 21 310-foot (94 m) sections individually submerged into the harbor and secured with rocks and backfill; the first of these tunnel segments was sunk on April 11, 1956. The remainder of the tunnel was constructed using the cut-and-cover method, extending from the submerged tubes to the north and south portals.