On this 110 years ago the first subway tunneling under the East River connecting #Manhattan with #Brooklyn opened! The East River Tunnel connecting Bowling Green to #BoroughHall, Brooklyn on today’s 4,5 subway line opened to the public on January 9, 1908. The second #subway contract from 1902 extended the original IRT subway line to Brooklyn via the Battery-Joralemon Tunnel, then up Fulton Street to Flatbush to the Long Island #Railroad Terminal on Atlantic. The tunnel was comprised of two cast-iron tubes, 16 feet in diameter. When the tunnel first opened telephones were placed every 300 feet, monitored by an IRT employee in an office at #BowlingGreen who could watch the location of the trains in the tunnel via colored lights on a transparency. The construction process is described in detail by the American Society of Civil #Engineers, "both heading-and-bench rock tunneling and pressurized shield soft-soil tunneling techniques were used. Loss of control of the tunneling shield in partially saturated sands caused variations in alignment that made portions of the tunnel nonfunctional. Approximately 3,000 ft of the tunnel had to be reconstructed to enable subway cars to use the tunnel safely. Additionally, due to concerns regarding the stability of the tunnel in the soft soils, piles were installed under the tunnel to bedrock. The project was a crucible for subway contractors and engineers of the Rapid Transit Commission, especially Clifford M. Holland. His experience on the #Joralemon Street Tunnel enabled him to efficiently and safely complete four other East River #subway tunnels after the Dual System Agreement of March 1913." (at Brooklyn Borough Hall) https://www.instagram.com/p/BsbhST-lPcQ/?utm_source=ig_tumblr_share&igshid=84hc0uzt27nq
