99-721: The North–South Rail Link (NSRL) is a proposed rail tunnel , or pair of tunnels, that would connect North Station and South Station in downtown Boston , Massachusetts, linking rail networks that serve the city's northern suburbs, New Hampshire, and Maine with the rest of the country. The project would build new underground stations near the existing stations, connect them with about 1.5 miles (2.4 km) of tunnels, and add other tunnels to link up with existing surface tracks. The NSRL would connect Amtrak and MBTA Commuter Rail lines that terminate either at North or South Station. For MBTA, it would link northern lines to South Station, Back Bay Station , and lines beyond Back Bay, including
198-695: A canal . The central portions of a rapid transit network are usually in the tunnel. Some tunnels are used as sewers or aqueducts to supply water for consumption or for hydroelectric stations. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment. Secret tunnels are built for military purposes, or by civilians for smuggling of weapons , contraband , or people . Special tunnels, such as wildlife crossings , are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks . A tunnel
297-485: A possible Central Station and at North Station. Carrying a total of up to four tracks, the tunnels would have steep inclines. Trains entering or exiting the tunnels would climb or descend 3% grades , each nearly 1 mile (1.6 km) long. Because the tunnels would continue well south of downtown, three portals would accommodate separate connections to Back Bay Station to the west, the Old Colony Lines to
396-638: A $ 2 million feasibility study on March 1, 2017. This study had been pushed for by the North-South Rail Link Working Group. The working group, NSRL supporters, includes Senator Ed Markey , Representatives Niki Tsongas and Katherine Clark , with Representative Seth Moulton leading the effort. It also includes more than half of Massachusetts mayors. The 2018 MassDOT feasibility study analyzed four options. The costs, presented in 2028 dollars, include purchasing additional rolling stock, other required infrastructure improvements, and
495-511: A 3.5% annual inflation. Presenters noted that a planned expansion of South Station would cost an estimated $ 4.7 billion, not including the purchase of rolling stock, electrifying the system, and renovating Tower 1. Two options would run under the Central Artery (I-93), one option with two tracks and the other, more expensive, with four. The other two options, each with two tracks, would tunnel under downtown Boston several blocks west of
594-457: A five-person board of directors which approves major decisions. The Department directly administers some operations, while others remain semi-autonomous. Formerly an independent state entity, which until 1992 even had its own uniformed police force for vehicular traffic law enforcement, the Registry of Motor Vehicles Division is now directly administered by MassDOT. It is the equivalent of
693-449: A large factor in the decision making process. Civil engineers usually use project management techniques for developing a major structure. Understanding the amount of time the project requires, and the amount of labor and materials needed is a crucial part of project planning. The project duration must be identified using a work breakdown structure and critical path method . Also, the land needed for excavation and construction staging, and
792-562: A large number of at-grade crossings. Several of the crossings (e.g. Massachusetts Avenue, several streets around Kendall Square, Cambridge Street, and Gore Street) require trains to come to a near-complete stop before proceeding at their maximum allowed track speed of 10 miles per hour (16 km/h). The line would potentially be served by a new West Station which is proposed as part of the Beacon Park Yard redevelopment. The Grand Junction corridor has also been proposed as part of
891-580: A new Central Station near Aquarium Station . Central Station would have an 800-foot (240 m) platform; North Station and South Station would have 1,050-foot (320 m) platforms. Pilings for a South Station Tower at South Station complicate a proposal to put the tunnels directly beneath the present South Station. Instead, the Dorchester Avenue Alignment proposal would move the tracks just east of South Station, and would build an underground facility about 100 feet (30 m) below
990-467: A pipe jack, with the span of some box jacks in excess of 20 metres (66 ft). A cutting head is normally used at the front of the box being jacked, and spoil removal is normally by excavator from within the box. Recent developments of the Jacked Arch and Jacked deck have enabled longer and larger structures to be installed to close accuracy. There are also several approaches to underwater tunnels,
1089-599: A single 51 foot (16 m) TBM bored tunnel, 115–130 feet (35–40 m) deep. Underground South Station would be north-west of surface station. Estimated cost: $ 13.181 billion. North Station would be entirely underground and moved several blocks south, to between State and Haymarket Streets; no Central station. Tracks would be in two 29 foot (8.8 m) TBM bored tunnels, 135–195 feet (41–59 m) deep. Underground South Station would be north of surface station. Estimated cost: $ 14.388 billion. The tunnels would not be able to handle diesel locomotives and therefore would require
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#17327726426821188-421: A specialized method called clay-kicking for digging tunnels in clay-based soils. The clay-kicker lies on a plank at a 45-degree angle away from the working face and rather than a mattock with his hands, inserts with his feet a tool with a cup-like rounded end, then turns the tool with his hands to extract a section of soil, which is then placed on the waste extract. Clay-kicking is a specialized method developed in
1287-571: A study of the right-of-way requirements should be conducted for preservation of that right-of-way so as to not preclude this project's going forward in the future." In December 2007, the Federal Railroad Administration was interested in funding this project if the Massachusetts Executive Office of Transportation was interested in sponsoring it. In August 2009, the project was brought back into
1386-434: A tube can be sunk into a body of water, which is called an immersed tunnel. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support system strong enough to carry the load of what is to be built above the tunnel. There are two basic forms of cut-and-cover tunnelling: Shallow tunnels are often of the cut-and-cover type (if under water, of
1485-747: A tunnel than a sufficiently strong bridge). Some water crossings are a mixture of bridges and tunnels, such as the Denmark to Sweden link and the Chesapeake Bay Bridge-Tunnel in Virginia . There are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001. One of the worst railway disasters ever,
1584-432: A tunnel. Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong , this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront. The 1934 Queensway Tunnel under
1683-453: Is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel. MassDOT The Massachusetts Department of Transportation ( MassDOT ) oversees roads, public transit, aeronautics, and transportation licensing and registration in
1782-502: Is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ventilation openings at various points along the length. A pipeline differs significantly from a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for foot or vehicular road traffic , for rail traffic, or for
1881-485: Is higher than the current Red Line train frequency, and exceeds what has been achieved to date on other systems that use the new positive train control systems required for heavy rail. To maintain the 17 trains/hour frequency, trains would have to arrive to enter the tunnel precisely as scheduled. However, new systems like Thameslink in London, UK, have shown that up to 24 trains per hour are possible on heavy rail. With
1980-630: Is included in the 2018 proposals. Part of the Fairmount Line would be electrified to allow Amtrak and MBTA Northeast Corridor trains currently routed through Back Bay to reach South Station during construction of the Back Bay portal. The electrified service region would also incorporate the proposed South Coast Rail project's Phase II, which includes electrification to Fall River and New Bedford . The 2018 feasibility study modeled ridership in 2040 based on various scenarios. In regular service,
2079-505: Is intended to carry both the Istanbul metro and a two-level highway, over a length of 6.5 km (4.0 miles). The French A86 Duplex Tunnel [ fr ] in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of 10 km (6.2 miles). Although each level offers a physical height of 2.54 m (8.3 ft), only traffic up to 2 m (6.6 ft) tall
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#17327726426822178-732: Is privately operated. MassDOT is a member of the Northeast Corridor Commission . The Aeronautics Division, formerly the Massachusetts Aeronautics Commission, administers state financing of its airports; inspects and licenses airports and landing pads; registers aircraft based in Massachusetts as well as aircraft dealers, regulates airport security, safety, and navigation; and is responsible for statewide aviation planning. The Department of Transportation does not own any airports;
2277-494: Is relatively long and narrow; the length is often much greater than twice the diameter , although similar shorter excavations can be constructed, such as cross passages between tunnels. The definition of what constitutes a tunnel can vary widely from source to source. For example, in the United Kingdom, a road tunnel is defined as "a subsurface highway structure enclosed for a length of 150 metres (490 ft) or more." In
2376-401: Is sometimes necessary during the excavation of a tunnel. They are usually circular and go straight down until they reach the level at which the tunnel is going to be built. A shaft normally has concrete walls and is usually built to be permanent. Once the access shafts are complete, TBMs are lowered to the bottom and excavation can start. Shafts are the main entrance in and out of the tunnel until
2475-515: Is that the open building pit is muted after tunnel construction; no roof is placed. Some tunnels are double-deck, for example, the two major segments of the San Francisco–Oakland Bay Bridge (completed in 1936) are linked by a 160-metre (540 ft) double-deck tunnel section through Yerba Buena Island , the largest-diameter bored tunnel in the world. At construction this was a combination bidirectional rail and truck pathway on
2574-698: Is the Siloam Tunnel , built in Jerusalem by the kings of Judah around the 8th century BC. Another tunnel excavated from both ends, maybe the second known, is the Tunnel of Eupalinos , which is a tunnel aqueduct 1,036 m (3,400 ft) long running through Mount Kastro in Samos , Greece. It was built in the 6th century BC to serve as an aqueduct . In Ethiopia , the Siqurto foot tunnel , hand-hewn in
2673-543: Is the deepest in the MBTA system. There have been several prior proposals to link South Station and North Station by rail. In 1987, Congress included funding for the link in a highway and transit bull, but it was dropped after Ronald Reagan vetoed the bill. A North-South Rail Link was included in the original Big Dig design, but was dropped by the Dukakis Administration. An earlier leading proposal, called
2772-811: Is the staff of the Boston MPO and with which the MBTA contracts for planning assistance. The Highway Division accepts submissions for projects from its district offices and municipalities. The Accelerated Bridge Program is a bond bill signed into law by Governor Deval Patrick in August 2008, a year after the I-35W Mississippi River bridge collapse put the state's bridges in the spotlight. The $ 3 billion, 8-year accelerated bridge program will replace and rehabilitate around 270 bridges statewide. 300–500 additional bridges will be preserved to prevent further deterioration. As of September 1, 2015,
2871-600: Is thus a net recipient of general state funds. Massachusetts has 10 regional metropolitan planning organizations : and three non-metropolitan planning organizations covering the remainder of the state: By law, all federal transportation grants must be allocated by the responsible MPO. Statewide planning and coordination of MPOs is handled by the Department of Transportation. CTPS is the Central Transportation Planning Staff, which
2970-569: The Balvano train disaster , was caused by a train stalling in the Armi tunnel in Italy in 1944, killing 426 passengers. Designers try to reduce these risks by installing emergency ventilation systems or isolated emergency escape tunnels parallel to the main passage. Government funds are often required for the creation of tunnels. When a tunnel is being planned or constructed, economics and politics play
3069-781: The Department of Motor Vehicles in most states, and processes driver's licenses and motor vehicle registrations. All public transportation agencies are administered independently. However, the DOT board of directors is also the board of directors for the Massachusetts Bay Transportation Authority , the major provider of public transportation in the Greater Boston area. The remaining 15 public transit authorities are called Regional Transit Agencies (RTAs), and they provide public bus services in
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3168-619: The Framingham/Worcester Line and the Northeast Corridor ; one option under consideration would also link to commuter lines to the south. The project would also link Amtrak's various trains into and out of the city; for example, the Downeaster line from Maine currently has no direct connection with Northeast Corridor trains to New York City and beyond. In 2017, a Harvard Kennedy School study estimated
3267-714: The Framingham/Worcester Line near Boston University and the Mass Turnpike Allston / Brighton exit ramps, and the track then crosses the Charles River into Cambridge . From there, it runs through the East Cambridge neighborhood and into Somerville , where it connects to the commuter rail lines running from North Station, just below the McGrath-O'Brien Highway . The line is currently single-tracked east of Massachusetts Avenue and slow, with
3366-471: The Port Authority of New York and New Jersey was not aware of this bill and had not asked for a grant for such a project. Increased taxes to finance a large project may cause opposition. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the groundwater conditions, the length and diameter of
3465-848: The Queens-Midtown Tunnel between Manhattan and the borough of Queens on Long Island ; the Detroit-Windsor Tunnel between Michigan and Ontario ; and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia ; the 1934 River Mersey road Queensway Tunnel ; the Western Scheldt Tunnel , Zeeland, Netherlands; and the North Shore Connector tunnel in Pittsburgh, Pennsylvania . The Sydney Harbour Tunnel
3564-707: The Red Line at Porter station. Passengers on the Newburyport/Rockport Line can also take the Silver Line from Chelsea (Bellingham Square) . The weekday-only MBTA bus #4 connects the two stations. The North–South Rail Link is proposed to fill all these awkward gaps in service, with direct connections requiring no transfers. In June 2018, MassDOT released a North South Rail Link Feasibility Reassessment presentation that described several tunnel alternatives. The state began soliciting bids for
3663-472: The River Mersey at Liverpool was chosen over a massively high bridge partly for defense reasons; it was feared that aircraft could destroy a bridge in times of war, not merely impairing road traffic but blocking the river to navigation. Maintenance costs of a massive bridge to allow the world's largest ships to navigate under were considered higher than for a tunnel. Similar conclusions were reached for
3762-679: The United Kingdom of digging tunnels in strong clay-based soil structures. This method of cut and cover construction required relatively little disturbance of property during the renewal of the United Kingdom's then ancient sewerage systems. It was also used during the First World War by Royal Engineer tunnelling companies placing mines beneath German lines, because it was almost silent and so not susceptible to listening methods of detection. Tunnel boring machines (TBMs) and associated back-up systems are used to highly automate
3861-536: The Urban Ring light rail or bus rapid transit project, or a possible pedestrian trail. However, only Worcester Line trains would be directly served, while all other trains from South Station lines would have to detour and reverse all the way to the west of Back Bay and Lansdowne stations to reach the Grand Junction connection. Tunnel A tunnel is an underground or undersea passageway. It
3960-610: The canton of Glarus . The borehole has a diameter of 8.03 metres (26.3 ft). The four TBMs used for excavating the 57-kilometre (35 mi) Gotthard Base Tunnel , in Switzerland , had a diameter of about 9 metres (30 ft). A larger TBM was built to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands, with a diameter of 14.87 metres (48.8 ft). This in turn
4059-489: The water table . This pressurizes the ground ahead of the TBM cutter head to balance the water pressure. The operators work in normal air pressure behind the pressurized compartment, but may occasionally have to enter that compartment to renew or repair the cutters. This requires special precautions, such as local ground treatment or halting the TBM at a position free from water. Despite these difficulties, TBMs are now preferred over
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4158-449: The "Dorchester Avenue Alignment", is similar to the four-track Central Artery alignment in the 2018 study. It would dig two 41-foot-diameter (12 m) deep-bore tunnels beneath Boston, extending beyond the present rail yards north and south of the city. The tunnels would pass about 20 feet (6.1 m) beneath the I-90 extension, and would reach their maximum depth of 130 feet (40 m) at
4257-689: The 16th century as a metaphor for a narrow, confined space like the inside of a cask. Some of the earliest tunnels used by humans were paleoburrows excavated by prehistoric mammals. Much of the early technology of tunneling evolved from mining and military engineering . The etymology of the terms "mining" (for mineral extraction or for siege attacks ), " military engineering ", and " civil engineering " reveals these deep historic connections. Predecessors of modern tunnels were adits that transported water for irrigation , drinking, or sewerage . The first qanats are known from before 2000 BC. The earliest tunnel known to have been excavated from both ends
4356-638: The 1960s. The main idea of this method is to use the geological stress of the surrounding rock mass to stabilize the tunnel, by allowing a measured relaxation and stress reassignment into the surrounding rock to prevent full loads becoming imposed on the supports. Based on geotechnical measurements, an optimal cross section is computed. The excavation is protected by a layer of sprayed concrete, commonly referred to as shotcrete . Other support measures can include steel arches, rock bolts, and mesh. Technological developments in sprayed concrete technology have resulted in steel and polypropylene fibers being added to
4455-716: The 1971 Kingsway Tunnel under the Mersey. In Hampton Roads, Virginia , tunnels were chosen over bridges for strategic considerations; in the event of damage, bridges might prevent US Navy vessels from leaving Naval Station Norfolk . Water-crossing tunnels built instead of bridges include the Seikan Tunnel in Japan; the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City ;
4554-636: The Artery. All the proposals connect the northern commuter rail lines with South Station and then to Back Bay and lines to the west. Only the four-track option would connect North Station with the Fairmount Line south of South Station. Under all the proposals, the Old Colony Lines would continue to terminate at the South Station surface platforms. The existing North Station and its surface platforms could be eliminated under all four options, making
4653-596: The Department of Transportation, but the Secretary of Transportation serves on the Massport board of directors. Massport owns and operates the maritime Port of Boston , Boston's Logan International Airport , Hanscom Field and Worcester Regional Airport , which was transferred from the City of Worcester in 2010. The Woods Hole, Martha's Vineyard and Nantucket Steamship Authority regulates all ferry services to and from
4752-539: The Grand Junction Line into North Station. Also some or all Amtrak, Providence, Stoughton, and Franklin Line service would be rerouted via the Fairmount Line into South Station. The proposal makes aggressive assumptions about improved passenger loading and unloading times and on how many trains can operate per hour in the tunnels. The proposed train frequency, 17 per hour per direction in the two-track options,
4851-571: The MBTA. Local cities and towns also receive vehicle excise tax revenues, and levy property taxes. Both state and municipal agencies can levy fines for parking and traffic violations. Article 78 (LXXVIII) of the Massachusetts Constitution says all motor vehicle fees and taxes (except registration excise tax in lieu of property tax), including fuel taxes, must be spent on transportation, including roads, mass transit, traffic law enforcement, and administration. Transportation
4950-619: The Massachusetts taxpayers approximately $ 1 million per year. It is not clear if MassDOT has paid taxes on the benefit or reported it to the Internal Revenue Service , or who would be responsible if a payment to the IRS is required. As an executive department, the Governor of Massachusetts appoints the state Secretary of Transportation, who is also the "chief executive officer" of the Department. The governor also appoints
5049-709: The Middle Ages, crosses a mountain ridge. In the Gaza Strip , the network of tunnels was used by Jewish strategists as rock-cut shelters, in first links to Judean resistance against Roman rule in the Bar Kokhba revolt during the 2nd century AD. A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which will reduce
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#17327726426825148-531: The NSRL, the MBTA commuter rail system would be highly dependent on the tunnel routes. Any disruption to those routes would affect the entire system.While the NSRL design as proposed exceeds National Fire Protection Association NFPA 130 life safety requirements, evacuation of the deep tunnels and stations in case of fire could still be difficult. The deep stations would also cost passengers additional time entering and leaving. Currently Porter Square station , at 105 ft,
5247-550: The North-South Rail Link Working Group, in March 2017. The study did not identify a funding source for constructing the NSRL. On September 6, 2018, MassDOT released their draft feasibility reassessment report and asked for public comment by October 19. As of 2018, the MBTA and Amtrak use the Grand Junction Line for non-revenue vehicle moves between the two sides of their networks. This alternative connection splits from
5346-548: The Red Line via their shared Downtown Crossing station . The underground Winter Street Concourse connects the upper levels of Park Street and Downtown Crossing stations. Amtrak recommends that passengers with young children or much luggage take a taxi between the stations. It is possible to traverse the gap directly via the Orange Line from Back Bay Station to North Station, but it requires seven stops and not all of
5445-546: The US state of Massachusetts . It was created on November 1, 2009, by the 186th Session of the Massachusetts General Court upon enactment of the 2009 Transportation Reform Act. In 2009, Governor Deval Patrick proposed merging all Massachusetts transportation agencies into a single Department of Transportation. Legislation consolidating all of Massachusetts' transportation agencies into one organization
5544-599: The United States, the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m (75 ft) and a diameter greater than 1,800 millimetres (5.9 ft)." The word "tunnel" comes from the Middle English tonnelle , meaning "a net", derived from Old French tonnel , a diminutive of tonne ("cask"). The modern meaning, referring to an underground passageway, evolved in
5643-577: The area available for redevelopment. The most ambitious option is the only one that includes a new Central station (or Union Station) near its midpoint, and the only one with a rail tunnel connection to the Fairmount Line . North Station would be underground near the present station. The line would be constructed using two 41 foot (12 m) TBM tunnels, 125 feet (38 m) deep, along with cut-and-cover in Fort Point Channel. Underground South Station would be built in Fort Point Channel, east of
5742-400: The blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground. This may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel (or "drift tunnel") may be driven ahead of the main excavation. This smaller tunnel is less likely to collapse catastrophically should unexpected conditions be met, and it can be incorporated into
5841-451: The concrete mix to improve lining strength. This creates a natural load-bearing ring, which minimizes the rock's deformation . By special monitoring the NATM method is flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel strengthening . In pipe jacking , hydraulic jacks are used to push specially made pipes through
5940-453: The cost of the NSRL at $ 4 to $ 6 billion (in 2025 dollars), based on Federal Transit Administration data and an analysis of comparable tunnel projects around the world. A 2018 MassDOT study looked at four options with estimated costs ranging from $ 12 billion to $ 22 billion (in 2028 dollars). As of 2024, the North-South Rail Link has not been pursued and is not in active development, though advocates call for updated studies. From 1872 to 1969,
6039-410: The current Massachusetts administration "to get serious about building a rail link" rather than expand South Station. In January 2014, Dukakis said he would prefer to have the North–South Rail Link named after him, rather than South Station , as the Massachusetts House of Representatives had voted unanimously to do. In August 2015, former Governors Dukakis and William F. Weld co-wrote an op-ed calling
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#17327726426826138-402: The distribution of destinations for commuters coming from the north in the morning. The 2018 feasibility study identified several potential problems and risks with the NSRL project. During construction of the Back Bay tunnel portal, required under all options, the MBTA Worcester Line and Amtrak Lake Shore Limited service would have to terminate west of Back Bay station or possibly be rerouted via
6237-409: The entire tunnelling process, reducing tunnelling costs. In certain predominantly urban applications, tunnel boring is viewed as a quick and cost-effective alternative to laying surface rails and roads. Expensive compulsory purchase of buildings and land, with potentially lengthy planning inquiries, is eliminated. Disadvantages of TBMs arise from their usually large size – the difficulty of transporting
6336-441: The final tunnel or used as a backup or emergency escape passage. Alternatively, horizontal boreholes may sometimes be drilled ahead of the advancing tunnel face. Other key geotechnical factors: For water crossings, a tunnel is generally more costly to construct than a bridge. However, both navigational and traffic considerations may limit the use of high bridges or drawbridges intersecting with shipping channels, necessitating
6435-475: The freight-only Union Freight Railroad provided a direct, street running connection between most of the south-side and north-side railroads, and served local customers and wharves in between. From 1901 to 1938, the Atlantic Avenue Elevated provided direct passenger service past North and South Stations. The elevated trackage was not connected to any of the conventional railroad tracks. The Grand Junction Railroad , specifically its western segment, remains as
6534-405: The ground behind a TBM or shield. This method is commonly used to create tunnels under existing structures, such as roads or railways. Tunnels constructed by pipe jacking are normally small diameter bores with a maximum size of around 3.2 metres (10 ft). Box jacking is similar to pipe jacking, but instead of jacking tubes, a box-shaped tunnel is used. Jacked boxes can be a much larger span than
6633-587: The immersed-tube type), while deep tunnels are excavated, often using a tunnelling shield . For intermediate levels, both methods are possible. Large cut-and-cover boxes are often used for underground metro stations, such as Canary Wharf tube station in London. This construction form generally has two levels, which allows economical arrangements for ticket hall, station platforms, passenger access and emergency egress, ventilation and smoke control, staff rooms, and equipment rooms. The interior of Canary Wharf station has been likened to an underground cathedral, owing to
6732-435: The inevitable smoke and steam. A major disadvantage of cut-and-cover is the widespread disruption generated at the surface level during construction. This, and the availability of electric traction, brought about London Underground's switch to bored tunnels at a deeper level towards the end of the 19th century. Prior to the replacement of manual excavation by the use of boring machines, Victorian tunnel excavators developed
6831-445: The islands of Martha's Vineyard and Nantucket , and also operates its own passenger, vehicle, and freight ferries. The Authority has an effective monopoly on car ferry service, but private companies operate various passenger routes. Transportation funding available to the state and its agencies include: The statewide budget included $ 919 million for transportation in FY2009, not including $ 797M in sales tax revenue dedicated to
6930-468: The large TBM to the site of tunnel construction, or (alternatively) the high cost of assembling the TBM on-site, often within the confines of the tunnel being constructed. There are a variety of TBM designs that can operate in a variety of conditions, from hard rock to soft water-bearing ground. Some TBMs, the bentonite slurry and earth-pressure balance types, have pressurized compartments at the front end, allowing them to be used in difficult conditions below
7029-409: The link "One of the most important and cost-effective investments we can make". Based on their advocacy, MassDOT agreed to fund a $ 2 million study in February 2016. In June 2018, MassDOT released a North South Rail Link Feasibility Reassessment presentation that proposed several tunnel alternatives, described above. The state began soliciting bids for the $ 2 million feasibility study, advocated for by
7128-629: The lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck. In Turkey, the Eurasia Tunnel under the Bosphorus , opened in 2016, has at its core a 5.4 km (3.4 miles) two-deck road tunnel with two lanes on each deck. Additionally, in 2015 the Turkish government announced that it will build three -level tunnel, also under the Bosporus. The tunnel
7227-483: The older method of tunnelling in compressed air, with an airlock/decompression chamber some way back from the TBM, which required operators to work in high pressure and go through decompression procedures at the end of their shifts, much like deep-sea divers . In February 2010, Aker Wirth delivered a TBM to Switzerland, for the expansion of the Linth–Limmern Power Stations located south of Linthal in
7326-588: The only rail connection between the north and south railroads in the Boston area. Public transit connects North Station to South Station only indirectly, through two of the MBTA Subway system's quartet of hub stations. A trip between the two commuter rail stations requires taking two subway lines, either the Green Line and the Red Line through their shared Park Street station , or the Orange Line and
7425-540: The operation of empty and loaded trains at the same time. The temporary way is replaced by the permanent way at completion, thus explaining the term " Perway ". The vehicles or traffic using a tunnel can outgrow it, requiring replacement or enlargement: An open building pit consists of a horizontal and a vertical boundary that keeps groundwater and soil out of the pit. There are several potential alternatives and combinations for (horizontal and vertical) building pit boundaries. The most important difference with cut-and-cover
7524-565: The other. Many services would still terminate at North and South Stations, on existing tracks that do not lead into the tunnels. This could also allow trains to pass parked train cars. A 2003 DEIR/MIS assumes that about one-third of Amtrak trains to and from points south would be routed through the tunnel, stopping only at South Station, but with a new stop north of Boston at Anderson Regional Transportation Center in Woburn, Massachusetts . The Downeaster service from Maine and New Hampshire
7623-514: The program has reduced the number of structurally deficient bridges to 408, from 543 in 2008. The program is paid for using bonds in anticipation of future federal transportation grants to be issued to the state. The MassDOT has called the Accelerated Bridge Program the "Laboratory of Innovation". Engineers on each project are invited to investigate other options to replace the bridges faster and more efficiently to reopen
7722-608: The project due to its high capital cost (projected at several billion dollars, with wide variations depending on which option is chosen). Without matching local funds, the project was ineligible for federal funding, and was no longer listed as an approved project in state and Boston MPO capital plans. The April 2007 document Journey to 2030: Transportation Plan of the Boston Region Metropolitan Planning Organization said "the MPO feels that
7821-522: The project is completed. If a tunnel is going to be long, multiple shafts at various locations may be bored so that entrance to the tunnel is closer to the unexcavated area. Once construction is complete, construction access shafts are often used as ventilation shafts , and may also be used as emergency exits. The New Austrian Tunnelling method (NATM)—also referred to as the Sequential Excavation Method (SEM) —was developed in
7920-490: The proper machinery must be selected. Large infrastructure projects require millions or even billions of dollars, involving long-term financing, usually through issuance of bonds . The costs and benefits for an infrastructure such as a tunnel must be identified. Political disputes can occur, as in 2005 when the US House of Representatives approved a $ 100 million federal grant to build a tunnel under New York Harbor. However,
8019-410: The rapid transit system for many commuter rail passengers with destinations in the central part of the business district. This would relieve transit congestion in the downtown core. Like Philadelphia 's SEPTA system after the similar Center City Commuter Connection tunnel was built and connected two commuter rail systems, some of Boston's trains would be through-routed from one side of the system to
8118-552: The remainder of the state. The regional transit authorities are: The regional transit authorities shown in italics above are within MBTA's commuter rail service area, and provide connections to MBTA trains. DOT retains oversight and statewide planning authority, and also has a Rail section within the Mass Transit Division. Intercity passenger trains are operated by the federally owned Amtrak , and freight rail
8217-482: The risk of encountering unforeseen ground conditions. In planning the route, the horizontal and vertical alignments can be selected to make use of the best ground and water conditions. It is common practice to locate a tunnel deeper than otherwise would be required, in order to excavate through solid rock or other material that is easier to support during construction. Conventional desk and preliminary site studies may yield insufficient information to assess such factors as
8316-542: The sheer size of the excavation. This contrasts with many traditional stations on London Underground , where bored tunnels were used for stations and passenger access. Nevertheless, the original parts of the London Underground network, the Metropolitan and District Railways, were constructed using cut-and-cover. These lines pre-dated electric traction and the proximity to the surface was useful to ventilate
8415-492: The south, and the Fairmount Line running southwest. To the north, the tunnels would cross the Charles River about 70 feet (21 m) below its surface (bypassing an existing drawbridge), and connect via portals to the Fitchburg Line and the other northbound rail lines. The plan would require two or three new underground stations; stations are proposed roughly beneath the current North and South Stations, and possibly
8514-533: The southern lines pass through Back Bay; the Old Colony Lines , and Fairmount Line on the Commuter Rail do not. The Orange Line also provides a connection for Amtrak passengers who want to transfer between the Northeast Corridor and the Downeaster . However, North Station passengers add to Orange Line congestion. Similarly, it is possible to connect between South Station and the Fitchburg Line via
8613-557: The spotlight as a component of the New England transportation plan, a coordinated effort by the six New England states to improve rail transportation infrastructure by competing for the $ 8 billion allocated for high-speed rail in the American Recovery and Reinvestment Act of 2009 . In December 2011, former Governor Michael S. Dukakis reiterated his long-term support for rail service, saying he had been trying to convince
8712-799: The state-owned airports are controlled by the independent Massachusetts Port Authority (which shares its headquarters with the Aeronautics Division). Government regulation of aviation in the United States is dominated by the Federal Aviation Administration . Airline passenger and baggage screening is provided by the federal Transportation Security Administration , but airport security is provided locally. The 2009 reform law also created within MassDOT: The Massachusetts Port Authority (Massport) remains independent from
8811-683: The surface of the Fort Point Channel at the Summer Street crossing. Tracks at the underground South Station would have a 0.61% incline. The new Central Station would connect with the Blue Line at its Aquarium station via an underground concourse, as the Blue Line is the only rapid transit line in Boston that does not already connect with either North or South Station. The new station also would eliminate or reduce transfers to
8910-754: The surface station. Central station would connect to the Blue Line at Aquarium station . The Blue Line is currently the only MBTA rapid transit line with no direct connection to the commuter rail network. Estimated cost: $ 21.491 billion. Same route as Central Artery four-track but has no Central station. Constructed using one 41 foot (12 m) TBM tunnel, 125 feet (38 m) deep, with cut-and-cover used in Fort Point Channel. Underground South Station would be built in Fort Point Channel, east of surface station. Estimated cost: $ 12.317 billion. North Station would be entirely underground and moved several blocks south, to between State and Haymarket Streets; no Central station. Stacked tracks and platforms are incorporated within
9009-400: The tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and the shape of the tunnel and appropriate risk management. There are three basic types of tunnel construction in common use. Cut-and-cover tunnels are constructed in a shallow trench and then covered over. Bored tunnels are constructed in situ, without removing the ground above. Finally,
9108-637: The tunnels. The map below depicts one of the most extensive proposals made to date. The 2018 feasibility study options do not include a link to the Old Colony and Greenbush lines. Only the four-track option includes a link to the Fairmont Line and a Central station. The surface North Station would be eliminated in two of the options and might not be kept in the other two. In May 2006, the Commonwealth of Massachusetts withdrew its sponsorship of
9207-428: The two most common being bored tunnels or immersed tubes , examples are Bjørvika Tunnel and Marmaray . Submerged floating tunnels are a novel approach under consideration; however, no such tunnels have been constructed to date. During construction of a tunnel it is often convenient to install a temporary railway, particularly to remove excavated spoil , often narrow gauge so that it can be double track to allow
9306-425: The two-track options would increase all day boardings to 195,000 compared with 150,000 in the no-build scenario. Assuming an upgrade to all-day peak service, the two-track options would increase all day boardings to 225,000 compared with 195,000 with the South Station expansion. Overall, NSRL would increase commuter rail capacity, in terms of seats to downtown, by 25%. The feasibility study presentation also projected
9405-399: The use of dual-mode locomotives or the electrification of several MBTA commuter rail lines. Full electrification of additional rail lines, proposed in earlier studies, could help Massachusetts and the MBTA reach their greenhouse-gas reduction goals, make service more reliable, allow trains to accelerate more quickly, and reduce travel times, but it is expensive and only limited electrification
9504-512: Was assumed to stop at North Station only, with a direct connection to more southerly service at Anderson RTC rather than Boston. Thus, some operations would continue above ground at North Station and South Station, and all track and facilities would remain in place. The tunnels would not be equipped to handle diesel locomotives , which may not be suited to the planned steep grades and closely spaced stops; several Commuter Rail lines would necessitate electrification to safely and efficiently operate in
9603-575: Was constructed to provide a second harbour crossing and to alleviate traffic congestion on the Sydney Harbour Bridge , without spoiling the iconic view. Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather, and shipping during construction (as in the 51.5-kilometre or 32.0-mile Channel Tunnel ), aesthetic reasons (preserving the above-ground view, landscape, and scenery), and also for weight capacity reasons (it may be more feasible to build
9702-540: Was signed into law on June 26, 2009. The newly established Massachusetts Department of Transportation (MASSDOT) assumed operations from the existing conglomeration of state transportation agencies on November 1, 2009. This change included: In June 2018, The Boston Globe reported 467 current and former Massachusetts Department of Transportation employees were using the E-ZPass transponders for free. This employee benefit , that has been going on since at least 2009, costs
9801-732: Was superseded by the Madrid M30 ringroad , Spain, and the Chong Ming tunnels in Shanghai , China. All of these machines were built at least partly by Herrenknecht . As of August 2013 , the world's largest TBM was " Big Bertha ", a 17.5-metre (57.5 ft) diameter machine built by Hitachi Zosen Corporation , which dug the Alaskan Way Viaduct replacement tunnel in Seattle, Washington (US). A temporary access shaft
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