View source for Big Dig

{{Short description|1991–2007 megaproject in Boston, Massachusetts}}
{{Other uses}}
{{Use mdy dates|date=April 2020}}
{{Use American English|date=April 2020}}
{{Infobox tunnel
|name = Central Artery/Tunnel Project
|image = [[File:Mhs logo.png|frameless|125px]]<br />[[File:Boston Highway System Pre Post Big Dig.gif|frameless|300px]]<br />[[File:Big_Dig_Before_After.png|frameless|300px]]
|caption = Boston's highway system before and after the Central Artery/Tunnel Project
|official_name = 
|other_name = The Big Dig<br />CA/T Project
|location = [[Boston]], Massachusetts, United States
|coordinates = {{Coord|42.36197|N|71.05562|W|type:landmark_region:US|display=title,inline}}
|os_grid_ref = 
|status = 
|route = {{Jct|state=MA|I|90|I|93|US|1|SR|3}}
|start = 
|end = 
|startwork = 1982
|opened = {{start date and age|2003|}}
|close = 
|rebuilt = 
|reopen = 
|owner = 
|operator = 
|traffic = Automotive
|character = 
|toll = 
|vpd = 
|engineer = 
|construction = 1991–2007<ref name="enddate" />
|length = 
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The '''Big Dig''' was a [[megaproject]] in [[Boston]] that rerouted the elevated [[Central Artery]] of [[Interstate 93]] into the [[O'Neill Tunnel]] and built the [[Ted Williams Tunnel]] to extend [[Massachusetts Turnpike|Interstate 90]] to [[Logan International Airport]]. Those two projects were the origin of the official name, the '''Central Artery/Tunnel Project''' ('''CA/T Project'''). The megaproject constructed the [[Leonard P. Zakim Bunker Hill Memorial Bridge|Zakim Bunker Hill Bridge]] over the [[Charles River]], created the [[Rose Fitzgerald Kennedy Greenway|Rose Kennedy Greenway]] in the space vacated by the previous elevated roadway and funded more than a dozen projects to improve [[Massachusetts Bay Transportation Authority|the region's public transportation system]]. Planning began in 1982 and construction was carried out between 1991 and 2006. The project concluded in December 2007.<ref name="enddate">{{Cite news |first=Steve |last= LeBlanc |title= On December 31, It's Official: Boston's Big Dig Will Be Done |newspaper= The Washington Post |date=December 26, 2007 |access-date= December 26, 2007 |url= https://www.washingtonpost.com/wp-dyn/content/article/2007/12/25/AR2007122500600.html}}</ref> 

The project's general contractor was [[Bechtel]], with [[Parsons Brinckerhoff]] as the engineers, who worked as a consortium, both overseen by the [[Massachusetts Highway Department]]. The Big Dig was the most expensive highway project in the United States, and was plagued by [[cost overruns]], delays, leaks, design flaws, accusations of poor execution and use of substandard materials, criminal charges and arrests, and the [[Big Dig ceiling collapse|death of one motorist.]]<ref name="The Associated Press">{{Cite news |url=http://edition.cnn.com/2006/US/07/12/bigdigdeath.ap/index.html |title=Review Begins after Big Dig Tunnel Collapse |work= CNN |date= July 12, 2006 |agency= Associated Press |access-date= July 25, 2006 |archive-url = https://web.archive.org/web/20060715075257/http://edition.cnn.com/2006/US/07/12/bigdigdeath.ap/index.html |archive-date= July 15, 2006}}</ref> 

The project was originally scheduled to be completed in 1998<ref>{{cite book |author1= National Academy of Engineering |author2= National Research Council |author3= Transportation Research Board |chapter= Cost and Schedule Procedures |chapter-url= https://www.nap.edu/read/10629/chapter/4 |title= Completing the "Big Dig": Managing the Final Stages of Boston's Central Artery/Tunnel Project |publisher= The National Academies Press |location= Washington, DC |date= 2003 |doi= 10.17226/10629 |isbn= 978-0-309-08887-9 |access-date= March 27, 2019 }}</ref> at an estimated cost of $2.8 billion, US$7.4 billion adjusted for inflation {{As of|2020|lc=on}}.<ref name="inflation">{{cite web |url= http://www.westegg.com/inflation/ |title= The Inflation calculator |url-status= dead |archive-url= https://web.archive.org/web/20070808205626/http://www.westegg.com/inflation/ |archive-date= August 8, 2007 }}</ref> The project was completed in December 2007 at a $14.6 billion, a cost overrun of about 97% when adjusted for inflation.<ref name="inflation" /><ref>{{Cite news |first=Glen |last=Johnson |url= https://www.boston.com/news/local/massachusetts/articles/2006/07/13/governor_seeks_to_take_control_of_big_dig_inspections |title= Governor seeks to take control of Big Dig inspections |work= [[The Boston Globe]] |date= July 13, 2006 |access-date= July 13, 2006 |archive-url = https://web.archive.org/web/20070311201155/http://www.boston.com/news/local/massachusetts/articles/2006/07/13/governor_seeks_to_take_control_of_big_dig_inspections |archive-date = March 11, 2007}}</ref><ref>[https://www.boston.com/news/traffic/bigdig/articles/2008/07/17/big_digs_red_ink_engulfs_state/ Big Dig's red ink engulfs state] {{webarchive|url=https://web.archive.org/web/20080829212218/http://www.boston.com/news/traffic/bigdig/articles/2008/07/17/big_digs_red_ink_engulfs_state |date=August 29, 2008 }}, Boston Globe, July 17, 2008</ref> As a result of a death, leaks, and other design flaws, the Parsons Brinckerhoff and Bechtel consortium agreed to pay $407 million in restitution, and several smaller companies agreed to pay a combined sum of approximately $51 million.<ref>"[https://www.thestar.com/Business/article/296783 Contractors to settle Boston Big Dig suit for $450M] {{webarchive|url=https://web.archive.org/web/20121024100446/http://www.thestar.com/Business/article/296783 |date=2012-10-24 }}". ''[[Toronto Star]]''. January 23, 2008.</ref>

== Origin ==
[[File:OnBostonsElevatedCentralArtery.agr.jpg|thumb|Traffic on the old, elevated Central Artery at midday, 2003]]
This project was developed in response to the persistent and growing problem of traffic congestion on Boston's historically tangled and narrow streets, many of which were laid out centuries before the invention of the automobile. The layout, originally designed for horse-drawn carriages and pedestrian traffic, was never intended to accommodate modern vehicles, leading to chronic bottlenecks and delays that frustrated commuters and residents alike. As early as 1930, the city's Planning Board recognized the urgent need to address these traffic issues and recommended the construction of a raised express highway running north–south through the downtown district. The goal was to create a faster, more direct route that would allow through-traffic to bypass the congested city streets, reducing travel times and improving the flow of vehicles throughout the area.

Building on these early recommendations, Commissioner of Public Works William Callahan actively promoted detailed plans for what would become the Central Artery, an elevated expressway designed to run between the downtown district and the waterfront. The project was envisioned as a major infrastructure improvement that could transform urban mobility in Boston by separating local traffic from longer-distance through-traffic. Ultimately, the elevated expressway was constructed according to these plans, dramatically altering the cityscape while addressing some of the long-standing traffic challenges. Its development marked a pivotal moment in Boston's urban planning history, reflecting both the ambitions of city planners to modernize the transportation system and the broader nationwide trend during the mid-20th century toward building elevated highways through urban centers.

In the 1950s, Governor [[John Volpe]] interceded to change the design of the last section of the Central Artery, putting it underground through the [[Dewey Square Tunnel]]. While traffic moved somewhat better, the other problems remained. There was chronic congestion on the Central Artery (I-93), the elevated six-lane highway through the center of downtown Boston, which was, in the words of Pete Sigmund, "like a funnel full of slowly-moving, or stopped, cars (and swearing motorists)."<ref name="CEG">{{cite news |last=Sigmund |first=Pete |date=June 6, 2007 |title=Triumph, Tragedy Mark Boston's Big Dig Project |url=http://cegltd.com/story.asp?story=8751&headline=Triumph,%20Tragedy%20Mark%20Boston%E2%80%99s%20Big%20Dig%20Project |url-status=dead |archive-url=https://web.archive.org/web/20141006135142/http://cegltd.com/story.asp?story=8751&headline=Triumph,%20Tragedy%20Mark%20Boston%E2%80%99s%20Big%20Dig%20Project |archive-date=October 6, 2014 |access-date=December 10, 2007 |publisher=Construction Equipment Guide}}</ref>

In 1959, the {{convert|1.5|mi|km|adj=mid|-long|abbr=off|sp=us}} road section carried approximately 75,000 vehicles a day. By the 1990s, this had grown to 190,000 vehicles a day. Traffic jams of 16 hours were predicted for 2010.<ref>{{Cite web |url=https://www.mass.gov/info-details/the-big-dig-project-background |title=The Big Dig: project background |author=Massachusetts Department of Transportation (MassDOT) Highway Division |access-date=March 30, 2019 }}</ref>

The expressway had tight turns, an excessive number of entrances and exits, entrance ramps without merge lanes, and as the decades passed and other planned expressways were cancelled, continually escalating vehicular traffic that was well beyond its design capacity. Local businesses again wanted relief, city leaders sought a reuniting of the waterfront with the city, and nearby residents desired removal of the matte green-painted elevated road, which mayor [[Thomas Menino]] called Boston's "other [[Green Monster]]", as an unfavorable comparison to [[Fenway Park]]'s famed left-field wall.<ref>{{Cite news| agency=Associated Press | url=https://www.nbcnews.com/id/wbna3769829 | title=Boston's 'Big Dig' opens to public | work=NBC News | date=December 20, 2003 | access-date=March 30, 2019}}</ref> [[Massachusetts Institute of Technology|MIT]] engineers Bill Reynolds, and eventual state Secretary of Transportation [[Frederick P. Salvucci]] envisioned moving the whole expressway underground.<ref>{{Cite web|title=After 20 Years, the End Is Near for Boston's Big Dig|url=http://www.kitsapsun.com/opinion/after-20-years-the-end-is-near-for-bostons-big-dig-ep-423883076-359516211.html|access-date=2021-01-11|website=www.kitsapsun.com|language=en}}{{dead link|date=September 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{Cite news|last=McNichol|first=Dan|date=2004-07-25|title=Hub Guide / Getting Around; Big Dig Nearing Light of Costly Tunnel's End (Published 2004)|language=en-US|work=The New York Times|url=https://www.nytimes.com/2004/07/25/news/hub-guide-getting-around-big-dig-nearing-light-of-costly-tunnel-s-end.html|access-date=2021-01-11|issn=0362-4331}}</ref>

=== Cancellation of the Inner Belt project ===
[[File:Boston CAT Project-construction view from air.jpeg|thumb|The [[Leonard P. Zakim Bunker Hill Memorial Bridge|Zakim Bunker Hill Bridge]] over the Charles River under construction, looking north. The old elevated Central Artery crossing is to the right.]]
Another important motivation for the final form of the Big Dig was the abandonment of the Massachusetts Department of Public Works' intended expressway system through and around Boston. The Central Artery, as part of Mass. DPW's Master Plan of 1948, was originally planned to be the downtown Boston stretch of [[Interstate 95 in Massachusetts|Interstate 95]], and was signed as such. A bypass road called the Inner Belt, was subsequently renamed [[Interstate 695 (Massachusetts)|Interstate 695]]. The [[Federal-Aid Highway Act of 1956|law establishing the Interstate highway system was enacted in 1956.]]<ref name="Boston's Cancelled Highways">{{cite web |title=Boston's Cancelled Highways |url=http://www.bostonstreetcars.com/bostons-cancelled-highways.html |website=Boston Streetcars |access-date=January 28, 2019}}</ref>

The [[Inner Belt District]] was to pass to the west of the downtown core, through the neighborhood of [[Roxbury, Boston|Roxbury]] and the cities of [[Brookline, Massachusetts|Brookline]], [[Cambridge, Massachusetts|Cambridge]], and [[Somerville, Massachusetts|Somerville]]. Earlier controversies over impact of the Boston extension of the [[Massachusetts Turnpike]], particularly on the heavily populated neighborhood of [[Brighton, Boston|Brighton]], and the additional large amount of housing that would have had to be destroyed, led to [[freeway and expressway revolts|massive community opposition]] to both the Inner Belt and the Boston section of I-95.<ref name="Boston's Cancelled Highways"/>

By 1970, building demolition and land clearances had been completed along the I-95 right of way through the neighborhoods of Roxbury, [[Jamaica Plain]], the South End and [[Roslindale]]. This led to secession threats by [[Hyde Park, Boston|Hyde Park]], Boston's youngest and southernmost neighborhood, which I-95 was also slated to go through. By 1972, with relatively little work done on the [[Southwest Corridor (Boston)|Southwest Corridor]] portion of I-95 and none on the potentially massively disruptive Inner Belt, Governor [[Francis Sargent]] put a moratorium on highway construction within the [[Massachusetts Route 128|Route&nbsp;128]] corridor, except for the final short stretch of Interstate 93. In 1974, the remainder of the Master Plan was canceled.

With ever-increasing traffic volumes funneled onto I-93 alone, the Central Artery became chronically gridlocked. The Sargent moratorium led to the rerouting of I-95 away from Boston around the Route&nbsp;128 beltway, and the conversion of the cleared land in the southern part of the city into the [[Southwest Corridor Park|Southwest Corridor linear park]], and a new right-of-way for the [[Orange Line (MBTA)|Orange Line]] subway and [[Amtrak]].<ref>{{cite web |title="Decisions Touching the Lives of All of Us": The Plan That Changed Boston Forever |url=http://transitcenter.org/2016/06/22/massachusetts-governor-decides-transit-good-highways-bad/ |website=TransitCenter |access-date=January 28, 2019|date=June 23, 2016 }}</ref> Parts of the planned I-695 right-of-way remain unused and under consideration for future mass-transit projects.

The original 1948 Master Plan included a Third Harbor Tunnel plan that was hugely controversial in its own right, because it would have disrupted the [[Maverick Square]] area of [[East Boston]]. It was never built.<ref>{{cite book |author1=Federal Highway Administration |author2=Massachusetts Department of Public Works |title=Third harbor tunnel, interstate 90/central artery, interstate 93: full environmental impact statement and final section 4(f) evaluation |date=August 1985 |url=https://archive.org/stream/thirdharbortunne01mass/thirdharbortunne01mass_djvu.txt}}</ref>

=== Mixing of traffic ===
A major reason for the all-day congestion was that the Central Artery carried north–south traffic and east–west traffic. Boston's Logan Airport lies across [[Boston Harbor]] in East Boston. Before the Big Dig, the only access to the airport from downtown was through the paired [[Callahan Tunnel|Callahan]] and [[Sumner Tunnel|Sumner]] tunnels. Traffic on the major highways from west of Boston—the Massachusetts Turnpike and [[Storrow Drive]]—mostly traveled on portions of the Central Artery to reach these tunnels. Getting between the Central Artery and the tunnels involved short diversions onto city streets, increasing local congestion.

=== Mass transit ===
A number of [[public transportation]] projects were included as part of an [[environmental mitigation]] for the Big Dig. The most expensive was the building of the Phase II [[Silver Line (MBTA)|Silver Line]] tunnel under [[Fort Point Channel]], done in coordination with Big Dig construction. Silver Line buses now use this tunnel and the Ted Williams Tunnel to link [[South Station]] and Logan Airport.

Construction of the [[Massachusetts Bay Transportation Authority|MBTA]] Green Line [[Green Line Extension|extension beyond Lechmere]] to [[Medford/Tufts station]] opened in December 2022.<ref>{{cite web |title=Green Line Extension Project |url=https://www.mbta.com/projects/green-line-extension-glx |url-status=dead |archive-url=https://web.archive.org/web/20230306145552/https://www.mbta.com/projects/green-line-extension-glx |archive-date=March 6, 2023 |access-date=March 25, 2023 |website=MBTA Main Site |publisher=Greenlineextension.org}}</ref> {{As of|2023}}, promised projects to connect the [[Red Line (MBTA)|Red]] and [[Blue Line (MBTA)|Blue]] subway lines, and to restore the Green Line streetcar service to the [[Forest Hills (MBTA station)|Arborway]] in [[Jamaica Plain]] have not been completed. The Red and Blue subway line connection underwent initial design,<ref>[http://www.eot.state.ma.us/redblue/ Red Line / Blue Line Connector] {{webarchive |url=https://web.archive.org/web/20140105024145/http://www.eot.state.ma.us/redblue/ |date=January 5, 2014 }}</ref> but no funding has been designated for the project. The [[Green Line E branch|Arborway Line restoration]] has been abandoned, following a final court decision in 2011.<ref>{{cite news |url=http://jamaicaplaingazette.com/2011/08/26/trolley-comeback-killed-by-court/ |title=Trolley comeback killed by court |newspaper=Jamaica Plain Gazette |author=Ruch, John |date=August 26, 2011 |access-date=February 19, 2013 |url-status=live |archive-url=https://web.archive.org/web/20131229004250/http://jamaicaplaingazette.com/2011/08/26/trolley-comeback-killed-by-court/ |archive-date=December 29, 2013 }}</ref>

The original Big Dig plan included the [[North-South Rail Link]], which would have connected North and South Stations, the major passenger train stations in Boston. This aspect of the project was dropped by the state transportation administration early in the [[Michael Dukakis|Dukakis]] administration. Negotiations with the federal government had led to an agreement to widen some of the lanes in the new harbor tunnel, and accommodating these would require the tunnel to be deeper and mechanically vented. This left no room for the rail lines. Diesel trains, then in use, passing through the tunnel would have substantially increased the cost of the ventilation system.<ref name="Haglund2003">{{cite book|last1=Haglund|first1=Charles|title=Inventing the Charles River|date=2003|publisher=MIT Press|isbn=0-262-08307-8|page=[https://archive.org/details/inventingcharles00hagl/page/316 316]|url-access=registration|url=https://archive.org/details/inventingcharles00hagl/page/316}}</ref>

== Early planning ==
The project was conceived in the 1970s by the [[Boston Transportation Planning Review]] to replace the rusting elevated six-lane Central Artery. The expressway separated downtown from the waterfront, and was increasingly choked with bumper-to-bumper traffic. Business leaders were more concerned about access to [[Logan Airport]], and pushed instead for a third harbor tunnel.

In 1982, planning for the Big Dig as a project officially began. In 1983, environmental impact studies started. In 1987, after years of extensive lobbying for federal dollars, a public works bill appropriating funding for the Big Dig was passed by the [[Congress of the United States|US Congress]], but it was vetoed by President [[Ronald Reagan]] for being too expensive. When Congress [[Veto override|overrode]] the veto, the project had its green light. In 1991, ground was first broken.<ref>{{cite book|first=Dan|last=McNichol|title=The Big Dig|publisher=Silver Lining Books|year=2002|isbn=978-0-7607-3786-6}} Photography by Andy Ryan.</ref>

In 1997, the state legislature created the Metropolitan Highway System and transferred responsibility for the Central Artery and Tunnel "CA/T" Project from the Massachusetts Highway Department and the Massachusetts Governor's Office to the Massachusetts Turnpike Authority (MTA).<ref>{{cite news|title=Cerasoli charges Big Dig coverup|first=Thomas C.|last=Palmer Jr.|url=https://www.boston.com/globe/metro/packages/bechtel/archives/032101.htm|newspaper=Boston Globe|date=March 21, 2001|access-date=September 3, 2011|quote=Big Dig managers in the William F. Weld and Paul Cellucci administrations knew in 1994 that the megaproject's price tag was heading for $14 billion and schemed to hide billions in costs from the public and bond investors, according to a report issued yesterday by state Inspector General Robert Cerasoli.|url-status=live|archive-url=https://web.archive.org/web/20121104000302/http://www.boston.com/globe/metro/packages/bechtel/archives/032101.htm|archive-date=November 4, 2012}}</ref><ref>{{cite news|title=Federal Task Force on the Boston Central Artery/Tunnel Project: Introduction – Background|url=https://www.fhwa.dot.gov/reports/tunnel.htm#intro|agency=Federal Highway Administration, US Department of Transportation|publisher=Federal Task Force on the Boston Central Artery/Tunnel Project|page=7|access-date=September 3, 2011|quote=Although the Massachusetts Highway Department (MHD) is the nominal recipient of Federal-aid highway funds, State legislation in 1997 creating the Metropolitan Highway System transferred responsibility for the CA/T Project from the MHD to the Massachusetts Turnpike Authority (MTA).|url-status=live|archive-url=https://web.archive.org/web/20111015013148/http://www.fhwa.dot.gov/reports/tunnel.htm#intro|archive-date=October 15, 2011}}</ref>
The MTA, which had little experience in managing an undertaking of the scope and magnitude of the CA/T Project, hired a joint venture to provide preliminary designs, manage design consultants and construction contractors, track the project's cost and schedule, advise MTA on project decisions, and, in some instances, act as the MTA's representative. Eventually, MTA combined some of its employees with joint venture employees in an integrated project organization. This was intended to make management more efficient, but it hindered MTA's ability to independently oversee project activities because MTA and the joint venture had effectively become partners in the project.<ref>OIG Testimony CC-2005-027, "Impact of Water Leaks on the Central Artery/Tunnel Project and Remaining Risks"</ref>

== Obstacles ==
In addition to political and financial difficulties, the project received resistance from residents of Boston's historic North End, who in the 1950s had seen 20% of the neighborhood's businesses displaced by development of the Central Artery. In 1993, the North End Waterfront Central Artery Committee (NEWCAC) created, co-founded by Nancy Caruso, representing residents, businesses, and institutions in the North End and Waterfront neighborhoods of Boston. The NEWCAC Committee's goal included lessening the impact of the Central Artery/Tunnel Project on the community, representing the neighborhoods to government agencies, keeping the community informed, developing a list of priorities of immediate neighborhood concerns, and promoting responsible and appropriate development of the post-construction artery corridor in the North End and Waterfront neighborhoods.

The political, financial and residential obstacles were magnified when several environmental and engineering obstacles occurred. The downtown area through which the tunnels were to be dug was largely [[Land reclamation|land fill]], and included existing [[Red Line (MBTA)|Red Line]] and [[Blue Line (MBTA)|Blue Line]] [[rapid transit|subway]] tunnels as well as innumerable pipes and utility lines that would have to be replaced or moved. Tunnel workers encountered many unexpected geological and archaeological barriers, ranging from glacial debris to foundations of buried houses and a number of sunken ships lying within the reclaimed land.

The project received approval from state environmental agencies in 1991, after satisfying concerns including release of toxins by the excavation and the possibility of disrupting the homes of millions of [[rat]]s, causing them to roam the streets of Boston in search of new housing. By the time the federal environmental clearances were delivered in 1994,<ref name="Palmer">{{Cite news|first=Thomas |last=Palmer |url=http://libraries.mit.edu/rotch/artery/boston_globe.htm#wins |title=State Wins Federal OK to Start River-Crossing Part of Artery Project |work=[[The Boston Globe]] |date=June 21, 1994 |access-date=December 10, 2007 |archive-url=https://web.archive.org/web/20071105064639/http://libraries.mit.edu/rotch/artery/boston_globe.htm#wins |archive-date=November 5, 2007 |url-status=dead }}</ref> the process had taken some seven years, during which time inflation greatly increased the project's original cost estimates.<ref>{{Cite journal|last=Haynes|first=Wendy|date=June 2008|title=Boston's Big Dig Project: A Cautionary Tale|url=http://paperity.org/p/81488266/bridgewater-review-vol-27-no-1-june-2008|journal=Bridgewater Review |volume=27|issue=1|pages=3–7|url-status=live|archive-url=https://web.archive.org/web/20180317035739/http://paperity.org/p/81488266/bridgewater-review-vol-27-no-1-june-2008|archive-date=March 17, 2018}}</ref>

Reworking such a busy corridor without seriously restricting traffic flow required a number of state-of-the-art construction techniques. Because the old elevated highway, which remained in operation throughout the construction process, rested on pylons located throughout the designated dig area, engineers first utilized [[slurry wall]] techniques to create {{convert|120|ft|m|adj=mid|-deep}} concrete walls upon which the highway could rest. These concrete walls also stabilized the sides of the site, preventing cave-ins during the continued excavation process.

The multi-lane Interstate highway also had to pass under [[South Station (MBTA)|South Station]]'s seven railroad tracks, which carried over 40,000 commuters and 400 trains per day. To avoid multiple relocations of train lines while the tunneling advanced, as had been initially planned, a specially designed [[jack (device)|jack]] was constructed to support the ground and tracks to allow the excavation to take place below. Construction crews also used [[ground freezing]] (an artificial induction of [[permafrost]]) to help stabilize surrounding ground as they excavated the tunnel. This was the largest tunneling project undertaken beneath railroad lines anywhere in the world. The ground freezing enabled safer, more efficient [[Earthworks (engineering)|excavation]], and also assisted in environmental issues, as less contaminated fill needed to be exported than if a traditional [[Cut-and-cover tunnel|cut-and-cover method]] had been applied.<ref>{{cite web|url=http://tunnels.mottmac.com/projects/?mode=region&amp;id=3418 |title=Boston Central Artery Jacked Tunnels – Mott MacDonald Project Page |publisher=Tunnels.mottmac.com |access-date=April 8, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140408221143/https://tunnels.mottmac.com/projects/?mode=region&amp;id=3418 |archive-date=April 8, 2014 }}</ref>

Other challenges included existing subway tunnels crossing the path of the underground highway. To build slurry walls past these tunnels, it was necessary to dig beneath the tunnels and to build an underground concrete bridge to support the tunnels' weight, without interrupting rail service.

== Construction phase ==
[[File:Boston-big-dig-area.png|thumb|Construction sites of the "Big Dig"]]

The project was managed by the Massachusetts Turnpike Authority, with the Big Dig and the Turnpike's Boston Extension from the 1960s being financially and legally joined by the legislature as the [[Metropolitan Highway System]].<ref>{{cite web |url=http://www.mass.gov/legis/laws/mgl/81a-3.htm |title=MGL Chapter 81A, Section 3 |publisher=Mass.gov |access-date=April 8, 2014 |url-status=live |archive-url=https://web.archive.org/web/20100726222848/http://www.mass.gov//legis/laws/mgl/81a-3.htm |archive-date=July 26, 2010 }}</ref> Design and construction was supervised by a joint venture of [[Bechtel Corporation]] and [[Parsons Brinckerhoff]]. Because of the enormous size of the project—too large for any company to undertake alone—the design and construction of the Big Dig was broken up into dozens of smaller subprojects with well-defined interfaces between contractors. Major heavy-construction contractors on the project included [[Jay Cashman]], [[Modern Continental]], [[Obayashi Corporation]], [[Perini Building Company|Perini Corporation]], [[Peter Kiewit Sons' Incorporated]], [[J. F. White Contracting Co.|J. F. White]], and the Slattery division of [[Skanska]] USA. Of those, Modern Continental was awarded the greatest gross value of contracts, joint ventures included.

[[File:Boston_Central_Artery_(Big_Dig)_Construction_Contract_Progress_Map_-_Janaury_2004.jpg|right|thumb|275x275px|Construction Status by contract number as of January 1, 2004]]
The nature of the [[Charles River]] crossing had been a source of major controversy throughout the design phase of the project. Many environmental advocates preferred a river crossing entirely in tunnels, but this, along with 27 other plans, was rejected as too costly. With a deadline looming to begin construction on a separate project that would connect the [[Tobin Bridge]] to the Charles River crossing, Salvucci overrode the objections and chose a variant of the plan known as "Scheme Z". This plan was considered to be reasonably cost-effective, but had the drawback of requiring highway ramps stacked up as high as {{convert|100|ft|m}} immediately adjacent to the Charles River.<ref name="bg-scheme z">{{Cite news|title=Caution: High bridge ahead; Artery plan includes an awful scheme for a great wall across the Charles |last=Campbell |first=Robert |date=June 24, 1990 |work= [[The Boston Globe]] |id= Accessed August 4, 2009 |quote= The grotesque monstrosity that will be the new Central Artery requires a certain power of imagination to be grasped. Maybe that's why people are only now beginning to get upset about it.}}</ref>

The city of [[Cambridge, Massachusetts|Cambridge]] objected to the visual impact of the chosen Charles River crossing design. The city sued to revoke the project's environmental certificate and forced the project planners to redesign the river crossing again.<ref name="bg-cambridge">{{Cite news |title= Cambridge sues to halt bridge plan |last=Palmer Jr |first=Thomas C. |date= March 12, 1995 |work= [[The Boston Globe]] |id= Accessed August 4, 2009}}</ref>

[[File:ZakimBridge20040307.jpg|right|thumb|300px|The [[Leonard P. Zakim Bunker Hill Memorial Bridge|Leonard P. Zakim Bridge]]]]
Swiss engineer [[Christian Menn]] took over the design of the bridge. He suggested a cradle [[cable-stayed bridge]] that would carry ten lanes of traffic. The plan was accepted and construction began on the [[Leonard P. Zakim Bunker Hill Memorial Bridge]]. The bridge employed an asymmetrical design and a hybrid of steel and concrete was used to construct it. The distinctive bridge, designed by Boston-based architect [[Miguel Rosales]],<ref>{{Cite web|url=https://beaconhilltimes.com/2012/04/11/miguel-rosales-building-a-better-bridge/|title=Miguel Rosales: Building a better bridge – Beacon Hill Times|website=beaconhilltimes.com|access-date=2020-02-06}}</ref><ref>{{Cite web|url=https://culturenow.org/entry%26permalink%3D05598%26seo%3DLeonard-Zakim-Bunker-Hill-Bridge_Miguel-Rosales-HNTB-Christian--Menn-Theodore-Zoli-Richard-Hsu-and-Parsons-Brinckerhoff|title=CultureNOW - Leonard Zakim Bunker Hill Bridge: Miguel Rosales, HNTB, Christian Menn, Theodore Zoli, Richard Hsu and Parsons Brinckerhoff|website=culturenow.org|access-date=2020-02-06|archive-date=January 17, 2023|archive-url=https://web.archive.org/web/20230117064931/https://culturenow.org/entry%26permalink%3D05598%26seo%3DLeonard-Zakim-Bunker-Hill-Bridge_Miguel-Rosales-HNTB-Christian--Menn-Theodore-Zoli-Richard-Hsu-and-Parsons-Brinckerhoff|url-status=dead}}</ref><ref>{{Cite web|url=https://www.bostonglobe.com/metro/2013/05/30/for-lawrence-students-zakim-bridge-project-leads-acclaim-personal-tour-span-architect/eJJ6lEqmEt77yAvI0RU6RN/story.html|title=For Lawrence students, Zakim Bridge project leads to acclaim, personal tour by span's architect - The Boston Globe|last=Sullivan|first=James|website=BostonGlobe.com|access-date=2020-02-06}}</ref> is supported by two forked towers connected to the span by cables and girders. It was the first bridge in the country to employ this method and it was, at the time, the widest cable-stayed bridge in the world,<ref name="CEG" /> having since been surpassed by the [[Eastern span replacement of the San Francisco–Oakland Bay Bridge]].

Meanwhile, construction continued on the Tobin Bridge approach. By the time all parties agreed on the I-93 design, construction of the Tobin connector, today known as the "City Square Tunnel" for a [[Charlestown, Boston, Massachusetts|Charlestown]] area it bypasses, was far along, significantly adding to the cost of constructing the [[U.S. Route 1 in Massachusetts|US Route 1]] interchange and retrofitting the tunnel. <!--Shift to active voice shortened this sentence a little, but it's still unclear whether the Rt1 work and tunnel retrofit were built, or were abandoned because of the increased cost.-->

Boston blue [[clay]] and other soils extracted from the path of the tunnel were used to cap many local [[landfill]]s, fill in the [[Quincy Quarries Reservation|Granite Rail Quarry]] in [[Quincy, Massachusetts|Quincy]], and restore the surface of [[Spectacle Island (Massachusetts)|Spectacle Island]] in the [[Boston Harbor Islands National Recreation Area]].

The [[Storrow Drive Connector]], a companion bridge to the Zakim, began carrying traffic from I-93 to [[Storrow Drive]] in 1999. The project had been under consideration for years, but was opposed by the wealthy residents of the [[Beacon Hill, Boston|Beacon Hill]] neighborhood. It was finally accepted because it would funnel traffic bound for Storrow Drive and downtown Boston away from the mainline roadway.<ref>{{cite web| url=http://www.bostonroads.com/crossings/zakim/ | title=Leonard P. Zakim-Bunker Hill Memorial Bridge | access-date=July 18, 2006 | publisher=BostonRoads.com| archive-url= https://web.archive.org/web/20060626115922/http://www.bostonroads.com/crossings/zakim/| archive-date= June 26, 2006 | url-status= live}}</ref> The Connector ultimately used a pair of ramps that had been constructed for [[Interstate 695 (Massachusetts)|Interstate 695]], enabling the mainline I-93 to carry more traffic that would have used I-695 under the original Master Plan.

When construction began, the project cost, including the Charles River crossing, was estimated at $5.8 billion. Eventual [[cost overruns]] were so high that the chairman of the Massachusetts Turnpike Authority, [[James Kerasiotes]], was fired in 2000. His replacement had to commit to an $8.55 billion cap on federal contributions. The total expenses eventually passed $15 billion. Interest brought this cost to $21.93 billion.

=== Engineering methods and details ===
[[File:BigDigSupportsCentralArtery.agr.jpg|thumb|Temporary supports hold up the elevated Central Artery during construction.]]
Several unusual engineering challenges arose during the project, requiring unusual solutions and methods to address them. At the beginning of the project, engineers had to figure out the safest way to build the tunnel without endangering the existing elevated highway above. Eventually, they created horizontal braces as wide as the tunnel, then cut away the elevated highway's struts, and lowered it onto the new braces.<ref name="AP 122507">{{Cite news |url=https://news.yahoo.com/s/ap/20071225/ap_on_re_us/big_dig_the_end |archive-url=https://web.archive.org/web/20071228035119/http://news.yahoo.com/s/ap/20071225/ap_on_re_us/big_dig_the_end |archive-date=December 28, 2007 |title=Boston's $14.8B Big Dig finally complete |first=Steve |last=LeBlanc |agency=[[Associated Press]] |date=December 25, 2007}}</ref>

Three alternative construction methods were studied with their corresponding structural design to address existing conditions, safety measures, and constructability. In addition to codified loads, construction loads were computed to support final design and field execution.<ref>{{citation |author=Chalhoub Michel Soto |title=Construction Method and Supporting Structural Design for the Boston Area Central Artery Project |date=Aug 1999 |publisher=report#005081999 Integrated Services-CEM Eng Lib}}</ref>

== Final phases ==
[[File:Tunnel-large.jpg|thumb|The Interstate 93 tunnel]]
[[File:Greenway Aerial Shot.jpg|thumb|The [[Rose Kennedy Greenway]]]]

On January 18, 2003, the opening ceremony was held for the I-90 Connector Tunnel, extending the Massachusetts Turnpike (Interstate 90) east into the [[Ted Williams Tunnel]], and onwards to Boston [[Logan International Airport]]. The Ted Williams tunnel had been completed and was in limited use for commercial traffic and [[high-occupancy vehicle]]s since late 1995. The westbound lanes opened on the afternoon of January 18 and the eastbound lanes on January 19.<ref>{{cite news |url=https://www.newspapers.com/article/the-boston-globe/172257790/ |title=I-90 extension to open this weekend |newspaper=The Boston Globe |date=January 17, 2003 |pages=A1, [https://www.newspapers.com/article/the-boston-globe/172257673/ B4] |via=Newspapers.com}}</ref>

The northbound lanes of the I-93 tunnel opened on March 29, 2003.<ref>{{cite news |url=https://www.newspapers.com/article/the-boston-globe/172329154/ |title=Another piece of the puzzle |newspaper=The Boston Globe |date=March 27, 2003 |page=B4 |via=Newspapers.com}}</ref><ref>{{cite news |url=https://www.newspapers.com/article/the-boston-globe/172329194/ |first=Mac |last=Daniel |title=Motorists urged to steer clear of Central Artery |newspaper=The Boston Globe |date=March 27, 2003 |page=A1, [https://www.newspapers.com/article/the-boston-globe/172329262/ B5] |via=Newspapers.com}}</ref> A temporary ramp from I-90 westbound to I-93 southbound opened on December 6, 2003, as did Cross Street on the surface.<ref>{{cite news |url=https://www.newspapers.com/article/the-boston-globe/172331225/ |first=Anthony |last=Flint |title=Big Dig I-93 south ramp set to open |newspaper=The Boston Globe |date=December 5, 2003 |page=B4 |via=Newspapers.com}}</ref> The southbound lanes of the I-93 tunnel opened on December 20, 2003.<ref>{{cite news |url=https://www.newspapers.com/article/the-boston-globe/172331415/ |first=Anthony |last=Flint |title=Street Revival |newspaper=The Boston Globe |date=December 17, 2003 |pages=B1, [https://www.newspapers.com/article/the-boston-globe/172331443/ B4] |via=Newspapers.com}}</ref> A tunnel underneath [[Leverett Circle]] connecting eastbound Storrow Drive to I-93 North and the Tobin Bridge opened December 19, 2004, easing congestion at the circle. All southbound lanes of I-93 opened to traffic on March 5, 2005, including the left lane of the Zakim Bridge, and all of the refurbished [[Dewey Square Tunnel]].

By the end of December 2004, 95% of the Big Dig was completed. Major construction remained on the surface, including construction of final ramp configurations in the [[North End, Boston, Massachusetts|North End]] and in the [[South Bay, Boston, Massachusetts|South Bay]] interchange, and reconstruction of the surface streets.

The final ramp downtown — exit 16A (formerly 20B) from [[Interstate 93|I-93]] south to Albany Street — opened January 13, 2006.<ref>{{cite news | first=Casey | last=Ross | url=https://pqasb.pqarchiver.com/bostonherald/access/969503741.html?dids=969503741:969503741&FMT=ABS&FMTS=ABS:FT&date=Jan+14%2C+2006&author=CASEY+ROSS&pub=Boston+Herald&edition=&startpage=009&desc=Hallelujah+Hub+drivers!+Last+Big+Dig+ramp+done | title=Hallelujah Hub drivers! Last Big Dig ramp done | newspaper=Boston Herald | date=January 14, 2006 | access-date=July 18, 2006 | url-status=dead | archive-url=https://web.archive.org/web/20121104142842/http://pqasb.pqarchiver.com/bostonherald/access/969503741.html?dids=969503741:969503741&FMT=ABS&FMTS=ABS:FT&date=Jan+14,+2006&author=CASEY+ROSS&pub=Boston+Herald&edition=&startpage=009&desc=Hallelujah+Hub+drivers!+Last+Big+Dig+ramp+done | archive-date=November 4, 2012 }}</ref>

In 2006, the two Interstate 93 tunnels were dedicated as the [[Thomas P. O'Neill Jr. Tunnel]], after the former [[Democratic Party (United States)|Democratic]] speaker of the [[United States House of Representatives|House of Representatives]] from Massachusetts who pushed to have the Big Dig funded by the federal government.

== Coordinated projects ==
The Commonwealth of Massachusetts was required under the Federal Clean Air Act to mitigate air pollution generated by the highway improvements. Secretary of Transportation Fred Salvucci signed an agreement with the [[Conservation Law Foundation]] in 1990 enumerating 14 specific projects the state agreed to build. This list was affirmed in a 1992 lawsuit settlement.<ref name="step">{{cite web|url=http://www.somervillestep.org/2005/04/commonwealth_ma.html|title=STEP: Commonwealth Magazine article against Green Line|url-status=live|archive-url=https://web.archive.org/web/20160222044336/http://www.somervillestep.org/2005/04/commonwealth_ma.html|archive-date=February 22, 2016}}</ref>

Projects which have been completed include:<ref name="step" /><ref>{{cite web|url=http://www.eot.state.ma.us/downloads/sip/07sipAnnualRpt.pdf |title=07 sip Annual Report |url-status=dead |archive-url=https://web.archive.org/web/20120213194530/http://www.eot.state.ma.us/downloads/sip/07sipAnnualRpt.pdf |archive-date=February 13, 2012 }}</ref>
* Restoration of three Old Colony commuter rail lines ([[Middleborough/Lakeville Line]], [[Plymouth/Kingston Line]], and [[Greenbush Line]])
* Expansion of [[Framingham/Worcester Line|Framingham Line]] to serve Worcester full-time
* Restoration of the [[Newburyport/Rockport Line]]
* Six-car trains on the [[MBTA Blue Line]], requiring platform lengthening, station modernization, and all new train cars
* [[MBTA Silver Line]], a bus rapid transit route to the South Boston waterfront and East Boston, including the airport
* 1,000 new commuter parking spaces<ref>{{cite web |url= https://www.bostonglobe.com/metro/regionals/north/2012/06/23/wonderland-garage-open-july-garages-slated-for-beverly-salem/XtoNhdmcdTVHMCSjWRbBxJ/story.html |title= Wonderland garage to open July 1; T garages slated for Beverly, Salem – The Boston Globe |work= BostonGlobe.com |url-status= live |archive-url= https://web.archive.org/web/20160222125958/https://www.bostonglobe.com/metro/regionals/north/2012/06/23/wonderland-garage-open-july-garages-slated-for-beverly-salem/XtoNhdmcdTVHMCSjWRbBxJ/story.html |archive-date= February 22, 2016 }}</ref>
* [[Fairmount Line]] improvements
* [[Green Line Extension]]

However, some projects were removed:
* Design of the [[Red-Blue Connector]]<ref>{{Cite web |title=Federal Register :: Approval and Promulgation of Air Quality Implementation Plans; Massachusetts; Transit System Improvements |url=https://www.federalregister.gov/documents/2015/12/08/2015-30819/approval-and-promulgation-of-air-quality-implementation-plans-massachusetts-transit-system |access-date=2023-06-01 |website=federalregister.gov |date=December 8, 2015 |publisher=Environmental Protection Agency}}</ref>
* Restoration of [[Green Line E branch]] service to {{bts|Arborway}}

=== Surface treatments ===
Some surface treatments that were part of the original project plan were dropped due to the massive cost overruns on the highway portion of the project.<ref>{{cite web |url=https://www.nbcnews.com/id/wbna22394932 |title=$14.8 billion later, Big Dig finally complete |work=NBC News| date=December 25, 2007 |access-date=April 19, 2023}}</ref>

$99.1 million was allocated for [[Environmental mitigation|mitigating improvements]]<ref name="DCR2017">[https://www.mass.gov/files/documents/2017/02/zp/New%2520Charles%2520River%2520Basin%2520Master%2520Plan%2520update%2520%25202017_01_17.pdf New Charles River Basin Citizens Advisory Committee, January 17, 2017] (presentation)</ref> to the [[Charles River Basin]], including the construction of [[North Point Park (Massachusetts)|North Point Park]] in Cambridge and [[Paul Revere Park]] in Charlestown.<ref name="DCR2017" /> The North Bank Bridge, providing pedestrian and bicycle connectivity between the parks, was not funded until the [[American Recovery and Reinvestment Act of 2009]]. Nashua Street Park on the Boston side was completed in 2003, by McCourt Construction with $7.9 million in funding from MassDOT.<ref>{{cite web |url=http://www.mccourtconstruction.com/project-title-5/ |title=Nashua Street Park |publisher=McCourt Construction |year=2005}}</ref>

As of 2017, $30.5 million had been transferred to the [[Massachusetts Department of Conservation and Recreation]] to complete five projects. Another incomplete but required project is the South Bank Bridge over the MBTA Commuter Rail tracks at North Station (connecting Nashua Street Park to the proposed South Bank Park, which is currently a parking lot under the Zakim Bridge at the Charles River locks).<ref>[https://www.boston.gov/sites/default/files/imce-uploads/2018-02/2018-02-05_noi_compiled.pdf Notice of Intent – SOUTH BANK BRIDGE PROJECT – Contract No. P13-2843-C1A] (submitted by DCR to Boston Conservation Commission, with maps)</ref>

Improvements in the lower Charles River Basin include the new walkway at [[Lovejoy Wharf]] (constructed by the developer of 160 North Washington Street, the new headquarters of [[Converse (shoe company)|Converse]]), the Lynch Family Skate Park (constructed in 2015 by the Charles River Conservancy), rehabilitation of historic operations buildings for the [[Charles River Dam]] and lock, a maintenance facility, and a planned pedestrian walkway across the Charles River next to the [[MBTA Commuter Rail]] drawbridge at North Station (connecting Nashua Street Park and North Point Park).<ref name="DCR2017" /> MassDOT is funding the South Bank Park,<ref name="DCR2017" /> and replacement of the North Washington Street Bridge (construction Aug 2018–23).<ref>[https://www.mass.gov/north-washington-street-bridge-replacement North Washington Street Bridge Replacement]</ref>

[[EF Education]] is funding public greenspace improvements as part of its three-phase expansion at North Point.<ref>[https://www.cambridgema.gov/~/media/Files/CDD/ZoningDevel/SpecialPermits/sp328/SP328_app_Vol3_A.pdf EF Education III]</ref> Remaining funding may be used to construct the North Point Inlet pedestrian bridge, and a pedestrian walkway over [[Leverett Circle]]. Before being replaced with surface access during the reconstruction of the [[Science Park station (MBTA)|Science Park]] MBTA Green Line station, Leverett Circle had pedestrian bridges with stairs that provided elevated access between the station, the Charles River Parks, and the sidewalk to the [[Boston Museum of Science]]. The replacement ramps would comply with [[Americans with Disabilities Act]] requirements and allow easy travel by wheelchair or bicycle over the busy intersection.<ref name="DCR2017" />

=== Public art ===
{{unreferenced section|date=November 2019}}
While not a legally mandated requirement, [[public art]] was part of the urban design planning process, and later design development work, through the Artery Arts Program. The intent of the program was to integrate public art into highway infrastructure (retaining walls, fences, and lighting) and the essential elements of the pedestrian environment (walkways, park landscape elements, and bridges). As overall project costs increased, the Artery Arts Program was seen as a potential liability, even though there was support and interest from the public and professional arts organizations in the area.

At the beginning of the highway design process, a temporary arts program was initiated, and over 50 proposals were selected. Development began on only a few projects before funding for the program was cut. Permanent public art that was funded includes: super graphic text and facades of former [[West End, Boston|West End]] houses cast into the concrete elevated highway abutment support walls near [[North Station]] by artist [[Sheila Levrant de Bretteville]]; Harbor Fog, a sensor-activated mist, light and sound sculptural environment by artist [[Ross Miller (artist)|Ross Miller]] in parcel 17; a historical sculpture celebrating the 18th and 19th century shipbuilding industry and a bust of shipbuilder [[Donald McKay]] in [[East Boston]]; blue interior lighting of the Zakim Bridge; and the [[Millers River (Middlesex)|Miller's River]] Littoral Way walkway and lighting under the loop ramps north of the [[Charles River]].

Extensive landscape planting, as well as a maintenance program to support the plantings, was requested by many community members during public meetings. <!-- need more details on landscape program here -->

== Impact on traffic ==
[[File:ONeilltoZakimBridge.agr.jpg|thumb|Traffic exiting the Thomas P. O'Neill Jr. Tunnel onto the Zakim Bridge]]
The Big Dig separated the co-mingled traffic from the Massachusetts Turnpike and the Sumner and Callahan tunnels. While only one net lane in each direction was added to the north–south I-93, several new east–west lanes became available. East–west traffic on the Massachusetts Turnpike/I-90 now proceeds directly through the Ted Williams Tunnel to Logan Airport and Route 1A beyond. Traffic between Storrow Drive and the Callahan and Sumner Tunnels still uses a short portion of I-93, but additional lanes and direct connections are provided for this traffic.

The result was a 62% reduction in vehicle hours of travel on I-93, the airport tunnels, and the connection from Storrow Drive, from an average 38,200 hours per day before construction (1994–1995) to 14,800 hours per day in 2004–2005, after the project was largely complete.<ref name=impactreport>{{cite web |url= http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |title= Archived copy |access-date=November 4, 2009 |url-status=dead |archive-url= https://web.archive.org/web/20110108043647/http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |archive-date= January 8, 2011 }} Transportation Impacts of MTA and CAT project, February 2006, Table 3-6: {{cite web |url= http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |title= Archived copy |access-date=November 4, 2009 |url-status=dead |archive-url= https://web.archive.org/web/20110108043647/http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |archive-date= January 8, 2011 }}</ref> The savings for travelers was estimated at $166 million annually in the same 2004–2005 time frame.<ref>[http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf Transportation Impacts of MTA and CAT project, February 2006, p. 24] {{webarchive |url=https://web.archive.org/web/20110108043647/http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |date=January 8, 2011 }}</ref> Travel times on the Central Artery northbound during the afternoon peak hour were reduced 85.6%.<ref>[http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf Transportation Impacts of MTA and CAT project, February 2006, Table 3-1] {{webarchive |url=https://web.archive.org/web/20110108043647/http://www.massdot.state.ma.us/Highway/downloads/financial/MTA-Economic-V1.pdf |date=January 8, 2011 }}</ref>

A 2008 ''Boston Globe'' report asserted that waiting time for the majority of trips actually increased as a result of [[induced demand|demand induced]] by the increased road capacity. Because more drivers were opting to use the new roads, traffic bottlenecks were only pushed outward from the city, not reduced or eliminated (although some trips are now faster). The report states, "Ultimately, many motorists going to and from the suburbs at peak rush hours are spending more time stuck in traffic, not less." The ''Globe'' also asserted that their analysis provides a fuller picture of the traffic situation than a state-commissioned study done two years earlier, in which the Big Dig was credited with helping to save at least $167 million a year by increasing economic productivity and decreasing motor vehicle operating costs. That study did not look at highways outside the Big Dig construction area and did not take into account new congestion elsewhere.<ref>{{Cite news| last=Murphy | first=Sean | date=November 16, 2008 | title=Big Dig pushes bottlenecks outward | work=[[The Boston Globe]] | url=https://www.boston.com/news/local/articles/2008/11/16/big_dig_pushes_bottlenecks_outward/ | access-date=April 1, 2009| archive-url= https://web.archive.org/web/20090401210807/http://www.boston.com/news/local/articles/2008/11/16/big_dig_pushes_bottlenecks_outward/| archive-date= April 1, 2009 | url-status= live}}</ref>

== Impact on property values ==
Towards the end of the Big Dig in 2003, it was estimated that the demolition of the Central Artery highway would cause a $732 million increase in property value in Boston's financial district, with the replacement parks providing an additional $252 million in value.<ref>{{cite journal |last1=Tajima |first1=Kayo |title=New Estimates of the Demand for Urban Green Space: Implications for Valuing the Environmental Benefits of Boston's Big Dig Project |journal=Journal of Urban Affairs |date=December 2003 |volume=25 |issue=5 |pages=641–655 |doi=10.1111/j.1467-9906.2003.00006.x|s2cid=154220276 }}</ref> As a result of the Big Dig, a large amount of waterfront space was opened up, which is now a high-rent residential and commercial area called the [[Seaport District]]. The development of Seaport alone was estimated to create $7 billion in private investment and 43,000 jobs.<ref>{{cite book |last1=Greiman |first1=Virginia |title=Megaprojects : lessons on risk and project management from the Big Dig |date=2013 |location=Hoboken, New Jersey |isbn=978-1-118-11547-3 |page=52}}</ref>

== Operations Control Center (OCC) ==
{{anchor|Operations Control Center (OCC)}}
{{expand section|date=April 2013}}

As part of the project, an elaborate Operations Control Center (OCC) [[control room]] was constructed in [[South Boston]]. Staffed on a "[[24/7/365]]" basis, this center monitors and reports on [[traffic congestion]], and responds to emergencies. Continuous [[video surveillance]] is provided by hundreds of cameras, and thousands of sensors monitor traffic speed and density, [[air quality]], water levels, temperatures, equipment status, and other conditions inside the tunnel. The OCC can activate [[Ventilation (firefighting)|emergency ventilation]] fans, change [[Variable-message sign|electronic display signs]], and dispatch service crews when necessary.<ref>{{cite journal|last=Johnson|first=Christine M.|author2=Edward L. Thomas|title=A Case Study Boston Central Artery/Tunnel Integrated Project Control System, Responding to incidents Rapidly and Effectively|journal=Metropolitan Transportation Management Center|date=October 1999|page=12|url=http://ntl.bts.gov/lib/jpodocs/repts_te/11063.pdf|access-date=April 4, 2014|url-status=live|archive-url=https://web.archive.org/web/20130309164537/http://ntl.bts.gov/lib/jpodocs/repts_te/11063.pdf|archive-date=March 9, 2013}}</ref><ref name=Rosenwald>{{cite web|last=Rosenwald|first=Mike|title=Fixing Boston's Horrible Jams|url=http://www.popsci.com/scitech/article/2003-09/fixing-bostons-horrible-jams|work=Popsci|date=September 4, 2003 |publisher=Popular Science|access-date=April 3, 2013|url-status=live|archive-url=https://web.archive.org/web/20130605101508/http://www.popsci.com/scitech/article/2003-09/fixing-bostons-horrible-jams|archive-date=June 5, 2013}}</ref><ref name=Lewis>{{cite news|last=Lewis|first=Raphael|title=The smart highway|url=http://cache.boston.com/traffic/bigdig/stories/032402_smart_highway.htm|access-date=April 3, 2013|newspaper=Boston Globe|date=March 24, 2002|url-status=live|archive-url=http://archive.wikiwix.com/cache/20130403123608/http://cache.boston.com/traffic/bigdig/stories/032402_smart_highway.htm|archive-date=April 3, 2013}}</ref>

== Problems ==
{{anchor|Problems}}

=== Leaks ===
As far back as 2001, Turnpike Authority officials and contractors knew of thousands of leaks in ceiling and wall fissures, extensive water damage to steel supports and fireproofing systems, and overloaded drainage systems.<ref>[http://www.thebostonchannel.com/bigdig/3924866/detail.html Report: Even More Big Dig Leaks Found – Big Dig News Story – WCVB Boston<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20060523164349/http://www.thebostonchannel.com/bigdig/3924866/detail.html |date=May 23, 2006 }}</ref> Many of the leaks were a result of [[Modern Continental]] and other subcontractors failing to remove gravel and other debris before pouring concrete. This information was not made public until engineers at MIT (volunteer students and professors) performed several experiments and found serious problems with the tunnel.<ref name="evenmorebigleaks">{{Cite news|title=Report: Even More Big Dig Leaks Found |url=http://www.thebostonchannel.com/bigdig/3924866/detail.html |publisher=WCVB-TV |date=November 17, 2004 |access-date=July 18, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060523164349/http://www.thebostonchannel.com/bigdig/3924866/detail.html |archive-date=May 23, 2006 }}</ref>

On September 15, 2004, a major leak in the [[Interstate 93]] north tunnel forced the closure of the tunnel while repairs were conducted. This also forced the Turnpike Authority to release information regarding its non-disclosure of prior leaks. A follow-up reported on "extensive" leaks that were more severe than state authorities had previously acknowledged. The report went on to state that the tunnel system had more than 400 leaks. A ''[[Boston Globe]]'' report countered that by stating there were nearly 700 leaks in a single {{convert|1000|ft|m|adj=on}} section of tunnel beneath [[South Station]]. Turnpike officials also stated that the number of leaks being investigated was down from 1,000 to 500.<ref name="evenmorebigleaks" />

The problem of leaks is further aggravated by the fact that many of them involve corrosive [[Seawater|salt water]]. This is caused by the proximity of [[Boston Harbor]] and the [[Atlantic Ocean]], causing a mix of salt and fresh water leaks in the tunnel. The situation is made worse by [[road salt]] spread in the tunnel to melt ice during freezing weather, or brought in by vehicles passing through.<ref name="54m-fix" /> Salt water and [[salt spray]] are well-known issues that must be dealt with in any [[marine environment]]. It has been reported that "hundreds of thousands of gallons of salt water are pumped out monthly" in the Big Dig, and a map has been prepared showing "hot spots" where water leakage is especially serious.<ref name="CorrosionGraphic" /> Salt-accelerated corrosion has caused ceiling light fixtures to fail (see below), but can also cause rapid deterioration of embedded [[rebar]] and other [[structural steel]] reinforcements holding the tunnel walls and ceiling in place.<ref name="54m-fix" />

=== Substandard materials ===
[[Massachusetts State Police]] searched the offices of [[Aggregate Industries]], the largest concrete supplier for the underground portions of the project, in June 2005. They seized evidence that Aggregate delivered concrete that did not meet contract specifications. In March 2006 [[Massachusetts Attorney General]] [[Thomas Reilly (Massachusetts politician)|Tom Reilly]] announced plans to sue project contractors and others because of poor work on the project. Over 200 complaints were filed by the state of Massachusetts as a result of leaks, cost overruns, quality concerns, and safety violations. In total, the state has sought approximately $100 million from the contractors ($1 for every $141 spent).<ref name="Reuters-StateWeighs">{{Cite news|url=http://www.iht.com/articles/2006/03/19/news/notes.php |title=State weighs suing 'Big Dig' contractors |work=International Herald Tribune |date=March 20, 2006 |access-date=July 17, 2006| archive-url= https://web.archive.org/web/20060718094219/http://www.iht.com/articles/2006/03/19/news/notes.php| archive-date= July 18, 2006 | url-status= live}}</ref>

In May 2006, six employees of the company were arrested and charged with conspiracy to defraud the United States. The employees were accused of reusing old concrete and double-billing loads.<ref>{{cite news |title= Arrests For Big Dig Concrete Fraud |url=https://www.cbsnews.com/news/arrests-for-big-dig-concrete-fraud/ |work=www.cbsnews.com|date = May 4, 2006|agency = Associated Press}}</ref> In July 2007, Aggregate Industries settled the case with an agreement to pay $50 million. $42 million of the settlement went to civil cases and $8 million was paid in criminal fines. The company will provide $75 million in insurance for maintenance as well as pay $500,000 toward routine checks on areas suspected to contain substandard concrete.<ref>{{cite web |url=http://www.insurancejournal.com/news/east/2007/07/30/82122.htm |title= Concrete Supplier to Pay $50 Million to Settle Big Dig Case |publisher=Insurancejournal.com |date=July 30, 2007 |access-date=April 8, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140408212726/http://www.insurancejournal.com/news/east/2007/07/30/82122.htm |archive-date=April 8, 2014 }}</ref>

In July 2009, two of the accused, Gerard McNally and Keith Thomas, both managers, pled guilty to charges of conspiracy, mail fraud, and filing false reports.<ref>{{cite news |last1=LAVOIE |first1=DENISE |title=2 to plead guilty in Big Dig concrete case |url=https://www.courant.com/sdut-2-to-plead-guilty-in-big-dig-concrete-case-2009jul08-story.html |work=courant.com |access-date=October 22, 2020 |archive-date=May 18, 2021 |archive-url=https://web.archive.org/web/20210518024414/https://www.courant.com/sdut-2-to-plead-guilty-in-big-dig-concrete-case-2009jul08-story.html |url-status=dead }}</ref> The following month, the remaining four, Robert Prosperi, Mark Blais, Gregory Stevenson, and John Farrar, were found guilty on conspiracy and fraud charges.<ref>{{cite news |title=4 Ex-Contractors Found Guilty In Big Dig Fraud |url=https://www.wbur.org/news/2009/08/04/big-dig-fraud |work=www.wbur.org |language=en|date = August 4, 2009|agency = Associated Press}}</ref> The four were sentenced to probation and home confinement and Blais and Farrar were additionally sentenced to community service.<ref>{{cite news |title=4 get probation for Boston Big Dig concrete fraud |url=https://www.sandiegouniontribune.com/sdut-4-get-probation-for-boston-big-dig-concrete-fraud-2010may27-story.html |work=San Diego Union-Tribune |date=27 May 2010}}</ref>

=== Fatal ceiling collapse ===
{{Main|Big Dig ceiling collapse}}

[[File:Ted Williams Tunnel Boston (0208).jpg|thumb|300px|Boston traffic crawls over a closed [[Ted Williams Tunnel]] entrance in Boston during [[rush hour]] on July 11, 2006, the day after the collapse.]]
A fatal accident raised safety questions and closed part of the project for most of the summer of 2006. On July 10, 2006, concrete ceiling panels and debris weighing {{convert|26|ST|t|abbr=off}} and measuring {{convert|20|by|40|ft|m|abbr=on}} fell on a car traveling on the two-lane ramp connecting northbound I-93 to eastbound [[Massachusetts Turnpike|I-90]] in [[South Boston]], killing Milena Del Valle, who was a passenger, and injuring her husband, Angel Del Valle, who was driving.<ref name=autogenerated2>{{cite news| title=Triumph, Tragedy Mark Boston's Big Dig Project| url=http://www.cegltd.com/story.asp?story=8751&headline=Triumph,%20Tragedy%20Mark%20Boston%E2%80%99s%20Big%20Dig%20Project| publisher=Construction Equipment Guide| date=June 6, 2007| access-date=December 10, 2007| archive-date=October 6, 2014| archive-url=https://web.archive.org/web/20141006135142/http://cegltd.com/story.asp?story=8751&headline=Triumph,%20Tragedy%20Mark%20Boston%E2%80%99s%20Big%20Dig%20Project| url-status=dead}}</ref>

Immediately following the fatal ceiling collapse, Governor [[Mitt Romney]] ordered a "stem-to-stern" safety audit conducted by the engineering firm of [[Wiss, Janney, Elstner Associates, Inc.]] to look for additional areas of risk. Said Romney: "We simply cannot live in a setting where a project of this scale has the potential of threatening human life, as has already been seen".<ref>{{Cite news | url=https://www.boston.com/news/local/massachusetts/articles/2006/08/17/governor_names_ill_firm_to_lead_big_dig_audit/ | title=Governor names Ill. firm to lead Big Dig audit | work=[[The Boston Globe]] | last=Mishra | first=Raja | date=August 17, 2006 | access-date=April 1, 2009 | url-status=live | archive-url=https://web.archive.org/web/20080516005249/http://www.boston.com/news/local/massachusetts/articles/2006/08/17/governor_names_ill_firm_to_lead_big_dig_audit/ | archive-date=May 16, 2008 }}</ref>

The collapse and closure of the tunnel greatly snarled traffic in the city. The resulting traffic jams are cited as contributing to the death of another person, a heart attack victim who died en route to Boston Medical Center when his ambulance was caught in one such traffic jam two weeks after the collapse.<ref name="BostonHerald">{{cite news|url=http://www.redorbit.com/news/business/591773/tunnel_horror__the_emergency/index.html |title=Man dies in tunnel backup |newspaper=Boston Herald |date=July 27, 2006 |access-date=August 8, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20090114065351/http://www.redorbit.com/news/business/591773/tunnel_horror__the_emergency/index.html |archive-date=January 14, 2009 }}</ref> On September 1, 2006, one eastbound lane of the connector tunnel was re-opened to traffic.<ref name="MassTurnpike=TurnpikeNews">{{Cite news| url=http://www.massturnpike.com/user-cgi/news.cgi?dbkey=241&type=Press%20Release&src=news | title=Turnpike News | publisher=Massachusetts Turnpike Authority | date=September 1, 2006 | access-date=December 3, 2006 |archive-url = https://web.archive.org/web/20071016234818/http://massturnpike.com/user-cgi/news.cgi?dbkey=241&type=Press+Release&src=news|archive-date=October 16, 2007 }}</ref><ref>{{Cite news | first=Elizabeth | last=Taurasi | title=Boston's Big Dig – One of Engineering's Biggest Mistakes? | url=http://www.designnews.com/article/CA6357443.html | publisher=Design News | date=July 28, 2006 | access-date=August 11, 2006 | archive-url=https://web.archive.org/web/20060813162611/http://www.designnews.com/article/CA6357443.html | archive-date=August 13, 2006 | url-status=dead }} See WikiNews article [[n:Portion of ceiling collapses in Boston tunnel|here]].</ref>

Following extensive inspections and repairs, Interstate 90 east- and westbound lanes reopened in early January 2007.<ref name="SeattlePi">{{Cite news| work=Seattle Post-Intelligencer | url=http://www.seattlepi.com/national/1110AP_Big_Dig.html | title=Mass. tunnel ceiling inspections ordered| publisher=SeattlePi.com | date=January 17, 2007 | access-date=January 7, 2006 }}{{dead link|date=May 2016|bot=medic}}{{cbignore|bot=medic}}</ref> The final piece of the road network, a high occupancy vehicle lane connecting Interstate 93 north to the [[Ted Williams Tunnel]], reopened on June 1, 2007.

On July 10, 2007, after a lengthy investigation, the [[National Transportation Safety Board]] found that [[epoxy]] glue used to hold the roof in place during construction was not appropriate for long-term bonding.<ref>{{Cite news|url=https://www.ntsb.gov/Pressrel/2007/070710b.htm |title=Safety Board Determines Cause of Boston's Big Dig Tunnel Ceiling Collapse Last Year |publisher=ntsb.gov |date=October 5, 2007 |access-date=July 12, 2006 |url-status=live |archive-url=https://web.archive.org/web/20071016221352/http://ntsb.gov/Pressrel/2007/070710b.htm |archive-date=October 16, 2007 }}</ref> This was determined to be the cause of the roof collapse. The Power-Fast Epoxy Adhesive used in the installation was designed for short-term loading, such as wind or earthquake loads, not long-term loading, such as the weight of a panel.<ref>{{Cite news |first= Rodrique |last= Ngowi |url= https://www.cbsnews.com/news/big-dig-victims-family-settles-for-6m/ |title= Big Dig Victim's Family Settles For $6M |agency= Associated Press |work= CBS News |date= December 25, 2007 |access-date= December 25, 2007 }}</ref><ref>{{Cite news| first=Casey | last=Ross | url= https://www.bostonherald.com/2007/08/08/epoxy-company-hit-with-big-dig-indictment | title=Epoxy company hit with Big Dig indictment | work= Boston Herald |date=August 8, 2007 | access-date= December 25, 2007}}</ref><ref name=Power-Fast>{{Cite news| url= http://www.powers.com/product_08402.html| title= Power-Fast+ Epoxy Adhesive System| publisher= powers.com| access-date= July 12, 2007| archive-url= https://web.archive.org/web/20070618031918/http://www.powers.com/product_08402.html| archive-date= June 18, 2007| url-status= dead}}</ref>

[[W.W. Grainger|Powers Fasteners]], the makers of the adhesive, revised their product specifications on May 15, 2007, to increase the [[safety factor]] from 4 to 10 for all of their epoxy products intended for use in overhead applications. The safety factor on Power-Fast Epoxy was increased from 4 to 16.<ref name="Power-Fast" /> On December 24, 2007, the Del Valle family announced they had reached a settlement with Powers Fasteners that would pay the family $6 million.<ref name="globe settlement">{{Cite news|url=https://www.boston.com/news/traffic/bigdig/articles/2007/12/24/settlement_reached_in_big_dig_death/?p1=Well_MostPop_Emailed1|title=Settlement reached in Big Dig death|work=[[The Boston Globe]]|date=December 24, 2007|access-date=December 25, 2007|first=Megan|last=Woolhouse|url-status=live|archive-url=https://web.archive.org/web/20110523100452/http://www.boston.com/news/traffic/bigdig/articles/2007/12/24/settlement_reached_in_big_dig_death/?p1=Well_MostPop_Emailed1|archive-date=May 23, 2011}}</ref> In December 2008, Powers Fasteners agreed to pay $16 million to the state to settle manslaughter charges.<ref>{{Cite news
 | first = Sean
 | last = Murphy
 | title = Manslaughter charges dismissed in Big Dig collapse
 | url = https://www.boston.com/news/local/breaking_news/2008/12/manslaughter_ch_1.html
 | access-date = December 17, 2008
| work=The Boston Globe
| date=December 17, 2008| archive-url= https://web.archive.org/web/20081218164307/http://www.boston.com/news/local/breaking_news/2008/12/manslaughter_ch_1.html| archive-date= December 18, 2008 | url-status= live}}</ref>

=== "Ginsu guardrails" ===
Public safety workers have called the walkway safety handrails in the Big Dig tunnels "[[ginsu]] guardrails", because the squared-off edges of the support posts have caused mutilations and deaths of passengers ejected from crashed vehicles. After an eighth reported death involving the safety handrails, [[MassDOT]] officials announced plans to cover or remove the allegedly dangerous fixtures, but only near curves or exit ramps.<ref name=Carroll-Rails>{{cite web|last=Carroll |first=Matt |title=State plans to remove many rails in tunnels |url=https://www.boston.com/news/local/massachusetts/articles/2011/04/15/state_plans_to_remove_or_cover_big_dig_tunnel_railings_after_deaths/ |work=boston.com |publisher=The Boston Globe |access-date=April 9, 2012 |date=April 15, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120210024625/http://www.boston.com/news/local/massachusetts/articles/2011/04/15/state_plans_to_remove_or_cover_big_dig_tunnel_railings_after_deaths/ |archive-date=February 10, 2012 }}</ref> This partial removal of hazards has been criticized by a safety specialist, who suggests that the handrails are just as dangerous in straight sections of the tunnel.<ref name="Carroll-Rails" />

=== Lighting fixtures ===
In March 2011, it became known that senior MassDOT officials had failed to disclose an issue with the lighting fixtures in the O'Neill tunnel. In early February 2011, a maintenance crew found a fixture lying in the middle travel lane in the northbound tunnel.<ref name="Moskowitz-lights">{{cite news|first=Eric |last=Moskowitz |title=State says some light fixtures in Big Dig tunnels are flawed |url=http://articles.boston.com/2011-03-16/news/29350222_1_tunnels-fixtures-fluorescent-lights |work=[[The Boston Globe]] |date=March 16, 2011 |access-date=July 11, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110426004212/http://articles.boston.com/2011-03-16/news/29350222_1_tunnels-fixtures-fluorescent-lights |archive-date=April 26, 2011 }}</ref> Assuming it to be simple [[road debris]], the maintenance team picked it up and brought it back to its home facility. The next day, a supervisor passing through the yard realized that the {{convert|120|lb|kg|abbr=on}} fixture was not road debris but was in fact one of the fixtures used to light the tunnel itself. Further investigation revealed that the fixture's mounting apparatus had failed, due to [[galvanic corrosion]] of incompatible metals, caused by having [[aluminum]] in direct contact with [[stainless steel]], in the presence of salt water.<ref name=CorrosionGraphic>{{cite web |title=The Mysterious Corroding Big Dig Light Fixtures |url=https://www.boston.com/news/local/massachusetts/20110710_tunnels_light_fixtures/ |work=boston.com |publisher=The Boston Globe |access-date=April 9, 2012 |url-status=live |archive-url=https://web.archive.org/web/20120407223210/http://www.boston.com/news/local/massachusetts/20110710_tunnels_light_fixtures/ |archive-date=April 7, 2012 }}</ref><ref name=ENR-Salt>{{cite journal|last=Knapschaefer|first=Johanna|title=MassDOT Study Blames Salt For Big Dig's Fallen Light Fixture|journal=Engineering News-Record|date=April 27, 2011|url=http://enr.com|url-status=live|archive-url=https://web.archive.org/web/20151221233320/http://www.enr.com/|archive-date=December 21, 2015}}</ref> The [[electrochemical]] [[potential difference]] between stainless steel and aluminum is in the range of 0.5 to 1.0V, depending on the exact alloys involved, and can cause considerable corrosion within months under unfavorable conditions.

After the discovery of the reason why the fixture had failed, a comprehensive inspection of the other fixtures in the tunnel revealed that numerous other fixtures were also in the same state of deterioration.<ref name=Mullan-Light>{{cite web|last=Mullan|first=Jeff|title=Tunnel Safety Ceiling Light Fixture Update|url=http://www.massdot.state.ma.us/portals/8/docs/TunnelSafety/TnnlSafetyBoardRpt040611.pdf|work=Report to the MassDOT Board of Directors|publisher=MassDOT|date=April 6, 2011|access-date=April 9, 2012|url-status=live|archive-url=https://web.archive.org/web/20130701232403/http://www.massdot.state.ma.us/portals/8/docs/TunnelSafety/TnnlSafetyBoardRpt040611.pdf|archive-date=July 1, 2013}}</ref> Some of the worst fixtures were temporarily shored up with plastic ties.<ref name="54m-fix" /> Moving forward with temporary repairs, members of the MassDOT administration team decided not to let the news of the systemic failure and repair of the fixtures be released to the public or to Governor [[Deval Patrick]]'s administration.<ref name="Murphy-lights">{{cite news |first1=Sean P. |last1=Murphy |first2=Scott |last2=Allen |title=Worries about lights were kept in the dark |url=http://articles.boston.com/2011-07-10/news/29758587_1_light-fixture-tunnels-state-engineers |work=[[The Boston Globe]] |date=July 12, 2011 |access-date=July 11, 2011 |archive-url=https://web.archive.org/web/20110720145746/http://articles.boston.com/2011-07-10/news/29758587_1_light-fixture-tunnels-state-engineers |archive-date=July 20, 2011 |url-status=dead }}</ref>

{{As of|2012|April}}, it appeared that all of the 25,000 light fixtures would have to be replaced, at an estimated cost of $54 million.<ref name=54m-fix>{{cite news|last=Murphy|first=Sean P.|date=April 5, 2012|title=Big Dig needs $54m light fix|url=http://articles.boston.com/2012-04-05/news/31295327_1_new-fixtures-entire-fixture-light-replacement-project|work=boston.com|publisher=The Boston Globe|access-date=April 9, 2012|url-status=dead|archive-url=https://web.archive.org/web/20120406184648/http://articles.boston.com/2012-04-05/news/31295327_1_new-fixtures-entire-fixture-light-replacement-project|archive-date=April 6, 2012}}</ref> The replacement work was mostly done at night, and required lane closures or occasional closing of the entire tunnel for safety, and was estimated to take up to two years to complete.<ref name="54m-fix" />

== See also ==
* [[Massachusetts Bay Transportation Authority]]
* [[Vincent Zarrilli]] – critic of the Big Dig who proposed the Boston Bypass
* [[Alaskan Way Viaduct replacement tunnel]] – similar project in [[Seattle]], Washington

'''International:'''
* [[Carmel Tunnels]] – similar project in [[Haifa, Israel]]
* [[Central–Wan Chai Bypass]] – similar project in the areas of Central, Wan Chai and Causeway Bay, within [[Victoria, Hong Kong|Victoria City]], Hong Kong
* [[WestConnex]] – project of similar scope and scale in [[Sydney]], [[New South Wales]], [[Australia]]
* [[Dublin Port Tunnel]] – similar project on a smaller scale in [[Dublin, Ireland]]
* [[Gardiner Expressway]] – an elevated freeway in [[Toronto]] with similar future plans
* [[Autopista de Circunvalación M-30]], {{ill|Túneles de la M-30|es}} and {{ill|Parque Madrid Río|es}} – similar project along the banks of [[Manzanares River]], [[Madrid, Spain]]
* [[Blanka tunnel complex]] – similar project in [[Prague]], [[Czech Republic]] and the longest city tunnel in Europe (6.4&nbsp;km / 4.0&nbsp;mi)
* [[Yamate Tunnel]] – similar project on a larger scale in [[Tokyo]], [[Japan]]

== References ==
{{Reflist}}

==Further reading==
* {{cite book |editor-last=Lewsi |editor-first=Ann-Eliza H. |date=2001 |title=Highway to the Past: The Archaeology of Boston's Big Dig |url=https://www.sec.state.ma.us/mhc/mhcpdf/Big_Dig_book.pdf |publisher=Massachusetts Historical Commission |archive-url=https://web.archive.org/web/20180317202839/https://www.sec.state.ma.us/mhc/mhcpdf/Big_Dig_book.pdf |archive-date=March 17, 2018 |url-status=dead}}

== External links ==
{{Commons category|Big Dig}}
* [https://www.mass.gov/the-big-dig Official site]
* {{webarchive |url=https://web.archive.org/web/20041208093611/https://www.bigdig.com/ |date=December 8, 2004 |title=Official site (2000–2004)}}
* {{webarchive |url=https://web.archive.org/web/20070705065926/http://www.masspike.com/bigdig/index.html |date=July 5, 2007 |title=Official site (2005–2007)}}
* [https://www.wgbh.org/podcasts/the-big-dig ''The Big Dig: The Story of America's Most Expensive Road'']—[[WGBH-TV|GBH News]] (podcast)
** [https://www.youtube.com/playlist?list=PLMQKK3_a14M3A-SQdVVWhOfOw8xRUuueJ ''The Big Dig: The Story of America's Most Expensive Road'']—via YouTube
* {{webarchive |url=https://web.archive.org/web/20050403144345/http://libraries.mit.edu/rotch/artery/ |date=April 3, 2005 |title=Boston CA/T Project History at MIT Rotch Library}}

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[[Category:2007 establishments in Massachusetts]]
[[Category:2007 in Boston]]
[[Category:Engineering projects]]
[[Category:Interstate 93]]
[[Category:Megaprojects]]
[[Category:North End, Boston]]
[[Category:Road tunnels in Massachusetts]]
[[Category:Transport infrastructure completed in 2007]]
[[Category:Tunnels completed in 2007]]
[[Category:Tunnels in Boston]]
[[Category:U.S. Route 1]]
[[Category:Underground construction]]