The Staten Island Tunnel is an abandoned, incomplete railway and subway tunnel in Staten Island, New York City. It was intended to connect railways on Staten Island (precursors to the modern-day Staten Island Railway) to the BMT Fourth Avenue Line of the New York City Subway, in Brooklyn, via a new crossing under the Narrows. Planned to extend , the tunnel would have been among the world's longest at the time of its planning, in the late 19th and early 20th centuries.

Construction began in 1923, and the tunnel was excavated into the Narrows before New York City Mayor John Hylan, a former Brooklyn–Manhattan Transit Corporation (BMT) employee and initial proponent of the tunnel, canceled the project in 1925. The tunnel lies dormant under Owl's Head Park in Bay Ridge, Brooklyn. Later proposals to complete the tunnel, including the 1939 plans for the Independent Subway System's ambitious Second System, were never funded.

Modern proposals for completion of the tunnel have come from New York City Councilman Lewis Fidler, who in 2007 proposed a 0.33% tax for the tri-state region to pay for the construction. The tunnel was listed as one of many projects that could receive federal funds that were to have been allocated to the Access to the Region's Core tunnel, which was canceled in October 2010. State Senator Diane Savino was among the supporters of the tunnel; Savino stated that if built, the tunnel would cost $3 billion and would improve quality of life for Staten Islanders, reduce traffic, and increase the attractiveness of the borough for investment.

Other names Officially called the Brooklyn-Richmond Freight and Passenger Tunnel, the Staten Island Tunnel was also to be referred to by four other names: The Narrows Tunnel, after the Narrows, the body of water it was supposed to run under; The Saint George Tunnel, after one of its terminals in St. George, Staten Island (not to be confused with the tunnel between the terminal and the Tompkinsville station); The Hylan Tunnel, after former New York City Mayor John Hylan, who oversaw the project. It has also been referred to as Hylan's Holes in both derogatory and endearing contexts.

Original plans In 1888, subsequent to building the Arthur Kill swing bridge between New Jersey and northwestern Staten Island, the Baltimore & Ohio Railroad (the owners of the Staten Island Railway until 1971) proposed a tunnel between Staten Island and Brooklyn. In 1890, Staten Island developer Erastus Wiman, who controlled the railway, sponsored a plan by the Baltimore and Ohio Railroad to construct a tunnel under the Narrows to connect Staten Island with Brooklyn for both passenger and freight service. The proposal never made it through the approval process when financial challenges stopped the plan at the drawing board. The tunnel would have gone near the foot of Vanderbilt Avenue on Staten Island to Bay Ridge in Brooklyn, traveling at a depth of below the narrows. There would have been two lines of tunneling, parallel and close together. Wiman believed that the tunneling would cost $5 million and that with the connecting road, the total cost was estimated at $6 million.

A rapid transit route to connect Staten Island to the remainder of New York City was proposed in 1912, in conjunction with the Dual Contracts of the New York City Subway. At the time, there were no vehicular or rail connections between Staten Island and the other four boroughs; the only connection was by ferry. Although not funded by the city, the tunnel was expected to help expand the then-sparsely populated borough in a similar manner to the population and development explosions seen in Brooklyn and the Bronx.

Under the Dual Contracts, three routes were proposed—two to Brooklyn and one to Manhattan—which would connect the Staten Island Railway's rapid transit service (SIRT) to existing subway lines.

Manhattan route The Manhattan proposal, often called the "direct route," would have connected with the Interborough Rapid Transit Company (IRT)'s lines under Battery Park, near the current Brooklyn–Battery Tunnel. "Direct Route A" would have utilized a five-section tunnel under the New York Harbor, while "Direct Route B" would have used a partially-elevated route running along the eastern coastline of New Jersey (near Greenville and Bayonne). Both Manhattan plans would have required connections to various points, including Ellis Island or Governors Island, and would have traveled around without any stops. Because of this, the high costs of the potential tunnel, and the relatively small population of Staten Island, the Manhattan route was considered impractical. Another 5-mile tunnel to Battery Park was proposed by the city in the 1950s, but the plan was scrapped due to a lack of funding.

Brooklyn routes Both of the shorter, Brooklyn proposals would have connected to the Brooklyn–Manhattan Transit Corporation (BMT)'s Fourth Avenue subway, constructed in 1914 during the Dual Contracts.

The first route would have originated in Bay Ridge, Brooklyn at a point between 65th and 67th Streets (just south of 59th Street Station), running to Arrietta Street in Tompkinsville, Staten Island near the Tompkinsville Station and one stop away from the Saint George Terminal. This plan, referred to as "Route No. 51" under the Dual Contracts, would have had connections going north towards St. George and along the North Shore Branch towards Arlington, and south towards Tottenville on the Main Line and Wentworth Avenue along the South Beach Branch. This proposal was estimated to cost $12 million in the year 1912, with half of it to be paid by railroads, such as the Pennsylvania Railroad (which operated the Long Island Rail Road) and the Baltimore and Ohio Railroad (which operated the SIRT). A major part of the 1912 proposal was the inclusion of two 40-inch water mains, which were to be side by side and were to be installed by the Department of Water Supply, Gas and Electricity alongside the tubes. These mains were intended to carry water from the main New York City supply to Staten Island.

The second route would have originated in Fort Hamilton at the south end of the line. Similar to the 1890 proposal, it would have followed the routing of the current Verrazzano–Narrows Bridge (constructed from 1959 to 1964). The Fort Hamilton proposal was the shortest route of the two, though it would require tunneling through deeper waters. As part of the proposal, it was suggested that the Fourth Avenue Line be extended past its original terminal at 86th Street in Bay Ridge to a temporary ferry terminal at 95th Street (now the 95th Street Station).

In anticipation of the northern tunnel route, trackways were constructed diverging from both Fourth Avenue local tracks towards the tunnel site south of the 59th Street Station. An additional portal was built in the SIRT tunnel between St. George Terminal and Tompkinsville to facilitate the northern wye from the tunnel to the North Shore Branch. As a provision for the southern route, the Fourth Avenue line south of 59th Street (built with only two tracks) was placed on the west side of Fourth Avenue, which would allow two additional tracks to be added on the east side of the street to facilitate a future express service from Staten Island.

Groundbreaking and stoppage of construction

Selection of Bay Ridge-based plan The Bay Ridge-based plan was ultimately selected, running between 65th Street/Shore Road in Brooklyn and the St. George Ferry Terminal in Staten Island. The two tubes would have been long, longer than any tunnel in the United States at that time. Portions of the Bay Ridge tunnel would be constructed using a tunnelling shield, while the remainder would be placed in a trench at the bottom of the Narrows. In the final plans, each tunnel was designed to be wide to accommodate freight cars in addition to passenger service, with freight trains coming from the Long Island Rail Road (LIRR)'s Bay Ridge Branch (terminating just north of the tunnel site) and the Staten Island Railway's connection with rail lines from New Jersey.

Alternate plans included constructing two sets of two tubes, one for commuter and freight service from the LIRR and the other for rapid transit, or two tunnels each with individual tubes for freight and subway service. The freight service would have occurred during off-peak hours only, but simultaneous with subway service, with passenger trains running in 30-minute or one-hour headways during these times. A 1912 proposal had freight running at night between 1 a.m. and 5 a.m., while the 1925 plans called for joint freight and passenger service during early mornings (5 a.m. to 6 a.m.), middays (10 a.m. to 4 p.m.), and overnights (8 p.m. to 5 a.m.).

At the time of the tunnel's groundbreaking, Jamaica Bay and the Paerdegat Basin were slated to become industrial complexes, which would have been facilitated by freight service from the tunnel. The tunnel plan was amended in 1919. In April 1921, a bill was passed in the state senate requiring the city to begin construction of the tunnel within two years.

1922 plan In May 1922, John Hylan launched a new plan for the freight and passenger tunnel, and the Board of Estimate recommended that $4.08 million be initially appropriated for the project. The Transit Commission and the Port Authority refused to accept the plan, as they each had their own plans. This plan was much less extensive than the original plan. The original plan would have had the tunnel from Owl's Head Park under the Narrows to Staten Island, and then continuing to a freight yard to be built in the center of Staten Island, from which a trunk line would run across the Arthur Kill to New Jersey as far as Paterson, before merging with the West Shore Railroad. The new revised plan would only cover the Narrows Tunnel, and a three-mile spur to Arlington Yard.

Under the new plan, freight would still only operate at night through the tunnel. Spurs connecting the tunnel in Brooklyn to the Long Island freight belt line, to the B&O freight sidings on Staten Island, and to the new city piers on Staten Island would have all been built. The project was projected to cost $60 million and if the job was done quickly, it could have been done by 1929. The route would help develop the waterfront areas in Staten Island and Jamaica Bay. Provisions would be made for connections with the subway system's Fourth Avenue Line, even though the Transit Commission refused to be involved with the plans.

Since the plan would benefit the Baltimore and Ohio Railroad, the Pennsylvania Railroad opposed it, and the railroad, cooperating with the Port Authority, proposed a tunnel from Brooklyn to Greenville, New Jersey, with a spur to Staten Island. The situation become complicated, as the Port Authority plan was approved by the State Legislatures in both New Jersey and New York. In addition, the Transit Commission proposed its own subway tunnel branching from the Fourth Avenue Line to be operated as part of the city's subway system.

Groundbreaking and preparations A groundbreaking ceremony was held by New York City Mayor John Hylan on April 14, 1923 in Bay Ridge and in Staten Island on July 19. Headings were dug and tunneling shafts were sunk at 68th Street and Shore Road in Brooklyn (the Shore Road Shaft), and underneath the Saint George Terminal in Staten Island (the South Street Shaft), costing a total of $1 million. On March 4, 1924, one of the caissons for the tunnel was sunk. In addition, in preparation for the tunnel, the SIRT purchased one hundred ME-1 subway cars built to BMT specifications and electrified its three passenger branches. The impending completion of the tunnel also sparked real estate interests in Staten Island.

Construction halted