An early concept sketch of U.S. Rep. John Larson's proposal to bury I-91 and I-84 underground in Hartford and East Hartford. The proposed tunnels are shown in yellow and the existing highways in blue. The cloverleaf intersection would be under Colt Park. Courtesy of U.S. Rep. John Larson
A concept sketch of U.S. Rep. John Larson's proposal to bury I-91 and I-84 underground in Hartford and East Hartford. The proposed tunnels are shown in yellow and the existing highways in blue. The cloverleaf intersection would be under Pope Park.
A concept sketch of U.S. Rep. John Larson’s proposal to bury I-91 and I-84 underground in Hartford and East Hartford. The proposed tunnels are shown in yellow and the existing highways in blue. The cloverleaf intersection would be under Colt Park. Courtesy of U.S. Rep. John Larson
A concept sketch of U.S. Rep. John Larson’s proposal to bury I-91 and I-84 underground in Hartford and East Hartford. The proposed tunnels are shown in yellow and the existing highways in blue. The cloverleaf intersection would be under Colt Park. Courtesy of U.S. Rep. John Larson

Not everyone is thrilled with U.S. Rep. John Larson’s proposal to build massive highway tunnels under Hartford, but Daniel Burnham might be, were he still with us. It was Burnham, the great Chicago architect and planner, who said, “Make no little plans. They have no magic to stir men’s blood and probably will not themselves be realized.”

Larson’s is anything but a little plan; it is breathtaking in scope. It has stirred the blood of some public officials and business leaders. But the concept is so vast, complex and potentially expensive – it would be longer than Boston’s “Big Dig” tunnels – that many doubt it could be realized.

Larson calls the proposal a “100-year solution” that would reduce traffic congestion on both I-84 and I-91, recapture large swaths of downtown land for much-needed development, reconnect northern neighborhoods to the rest of the city and even provide fill to repair the aging dikes on the Connecticut River. 

Hartford Mayor Luke Bronin praised it for those reasons, as has State Rep. Tony Guerrera, co-chair of the General Assembly’s transportation committee. CT News Junkie blogger Susan Bigelow called the idea “brilliant and necessary.” 

Others see it, as a Hartford Courant letter writer put it, as “the mother of all pipe dreams.”

University of Connecticut geology professor Robert Thorson, while applauding the conceptual benefits of a tunnel, can’t get his arms around this one. “It is beyond anything I could conceive. I see it as a fantasy,” he said. “It could be achieved, but at what expense?”  

For the Larson plan to be realized:

  • It must be drilled through a challenging subterranean environment of soft and hard rock – shale, sandstone, basalt – with fractures and faults. “It’s complicated down there,” said Thorson, who served as a consultant to the Adriaen’s Landing development along the Connecticut River. The challenge to tunnelers: “You never know what’s ahead of you.” He also observed that tunnels leak. “If you invest in one, you make a permanent commitment to pumping.” 
  • It would have to be paid for. Larson put a figure of $10 billion on the project when he announced it, but that is little more than an educated guess based on conversations with engineers – a “placeholder,” one advisor called it. There won’t be a real number until there’s an engineering study. 
  • The premise must be validated. The idea is that the tunnels will carry through traffic, leaving city portions of the highway to local traffic, thus reducing congestion on them. But there is as yet no traffic study showing there is enough through traffic, especially at rush hours, to make a difference and warrant the investment.

These challenges do not dissuade Larson from pushing ahead, at least to have the idea studied. “If people think it’s crazy, then we’re back where we were. Let’s solve the problem,” he said in a recent interview.


Larson’s announcement last month was met initially with some confusion. Hadn’t the state Department of Transportation just rejected a tunnel plan to replace the I-84 viaduct system, in large part because it would cost $10-$12 billion?

That was a different tunnel. The congressman is proposing two new tunnels, an east-west tunnel that would run under the southern tier of the city rather than under the present I-84 corridor, and a north-south tunnel that would carry I-91 from the north to the south meadows. 

The I-84 viaduct replacement project, which has been in the study and planning stages for a decade, is intended to replace the aging, mostly elevated I-84 highway. Over the course of a lengthy and widely praised public process, the DOT considered several options, including a tunnel, to replace the 51-year-old, mile-long series of viaducts.

Colt Park in Hartford, where Larson proposes an underground cloverleaf intersection for I-91 and I-84.
Colt Park in Hartford, where Larson proposes an underground cloverleaf intersection for I-91 and I-84. Tom Condon / file photo

In June department engineers determined that a highway at or slightly below grade was the best option, rejecting a 4,000-foot tunnel as too expensive and possibly harmful to adjoining properties, such as the Aetna campus. The estimated cost of the surface road is $4.3 billion to $5.3 billion, while the tunnel was estimated to cost between $10 and $12 billion.

DOT officials have forwarded their selection to federal highway officials for their approval, which is necessary to begin the environmental, planning and construction phases of the project. If all goes as hoped, construction will begin in 2022 or thereabouts.

A new highway in the viaduct right of way will modernize the design, improve safety and allow cross streets to reknit the severed city. But as Larson says, just replacing the road won’t relieve most of the congestion on it. About 175,000 cars a day pass through I-84 in Hartford, the highest volume in the state, and another 100,000 or so use I-91.

DOT officials are aware of the problem, and about six months ago began a $1 million study, 80 percent funded by the federal government, of how to relieve congestion at the I-84/I-91 interchange.  The study has begun to examine three long-term options: widening the historic stone-arch Bulkeley Bridge, moving the I-91/I-84 interchange north of downtown and building a new bridge over the Connecticut River, or running a highway across the southern tier of the city to connect with the Charter Oak Bridge.

Larson thinks his proposal compares favorably with all of those, and would like it included in the study.

Big mistake

Running U.S. interstate highways through the middle of many cities was, in the eyes of critics such as Reihan Salam and many others, the great flaw in the monumental postwar public works project. Greater Hartford offers a textbook example.

The interstates undeniably expedited countless millions of trips in and out of the city and reduced congestion on city streets, but at a cost. I-84 split the city in half to the detriment of the largely minority North End, where productive neighborhood fabric became wasteland. The highway took out irreplaceable architecture; cut the Aetna and Hartford Insurance Group campuses off from downtown, damaged the pedestrian environment; and added noise and pollution.

According to a possibly apocryphal story, I-84 went through the center of the city because Beatrice Fox Auerbach, owner of the famed G. Fox & Co. department store, wanted it to come right up to her door, and offered to build a parking garage if it did. True or not, it was the sentiment of a lot of mayors across the country, who thought downtown highways would revive their cities. As a rule, they didn’t. Some cities, including New Haven, are removing in-town highways and making them boulevards.

A study of the I-84 project done in 1970, just after it was completed, was remarkably critical: The highway “frequently dominates and is out of harmony with its physical environment,” was jamming throngs of cars onto city streets and was eroding the tax base by taking land off the grand list.

In addition to the problematic placement, I-84 was poorly designed, many have complained, with substandard shoulder widths, dangerous left-hand entrances and exits, and closely spaced access and exit ramps that create weaving conflicts between vehicles coming onto and getting off the road. Also, I-84 shrinks from three through-lanes to two in both directions around the Bulkeley Bridge, creating rush-hour bottlenecks.

These challenges and the relentless surge of vehicles  — the road was designed for 55,000 cars a day — have made the I-84 section in Hartford one of the state’s leading sites for accidents.

Placing the I-91/I-84 intersection in downtown Hartford was, as Hartford planning consultant Toni Gold observed, “totally crazy,” an assessment with which few disagree. I-91 managed to cut the city off from the river; completely, until a decades-long effort by the nonprofit group Riverfront Recapture managed to restore pedestrian access to the waterfront.

Transportation infrastructure profoundly affects a community for generations, and can induce “what if” speculation. For example, there was supposed to be a ring road around Hartford, but only a small part of it was built. What if it had been completed? Would it have taken through traffic out of downtown? Would it have encouraged more suburban sprawl?

Finally, there might have been less traffic if more attention had been paid to other modes of transportation.

New era

There was no use crying over poured concrete; Hartford lived with the highways. But early in this century came a turning point. The viaduct reached the end of its projected 40-year lifespan in 2005. The DOT was considering repairing the viaduct in place for an estimated $100 million when a citizen’s group formed and urged a different solution, one that would undo some of the damage the highway had done to the city.

Three conceptual routes the Connecticut Department of Transportation is studying to address congestion at the I-91 and I-84 intersection.
Three conceptual routes the Connecticut Department of Transportation is studying to address congestion at the I-91 and I-84 intersection. Courtesy of John Larson

The city and the Capitol Region Council of Governments got behind the effort, and then so did the DOT, where the thinking was changing, moving more toward how transportation could serve cities rather than just move cars. Maintenance repairs were done on the viaducts, and planning moved ahead that produced the surface road plan. 

The elevated viaducts were built in part to preserve the railroad right of way. Under the new plan, the railroad tracks will be slightly realigned, which will allow both modes to coexist at ground level. Planners expect to recoup 15 to 20 acres of developable land and build enough cross streets to reconnect the city.

But it doesn’t solve the congestion problem; indeed, if the highway works better and is less dangerous, more cars and trucks might try to use it.

Enter Larson.

The popular Democratic incumbent, who easily won reelection to a 10th term on Nov. 8, said a number of things pushed him toward the tunnel plan. He championed the successful effort to make the former Coltsville industrial village a national park, and would like to see I-91 lowered to provide better access from Coltsville to the river.

Perhaps most importantly, he has been working for years to get federal funds to repair the flood control system along the Connecticut River. A 2013 inspection by the U.S. Army Corps of Engineers said the elaborate system of dikes, pumping stations and conduits, which dates from the 1940s, was in an “unacceptable” state of repair, potentially a catastrophic problem.

Meeting with some engineers last spring about the dikes, he wondered if the traffic congestion problem couldn’t be solved with tunnels, with the rock from boring the tunnel going to shore up the dikes — two birds with a lot of stone. He said more meetings followed, culminating in the tunnel proposal. 

It would not be the only new tunnel under the capital city. The Metropolitan District Commission just signed a contract to construct a four-mile, $500 million wastewater conveyance and storage tunnel 200 feet under the city as part of its ongoing clean water project. This tunnel will be 18 feet in diameter, a third or less of the diameter of highway tunnels. 

Tunnels are the most expensive kind of infrastructure to build and maintain, according to the Federal Highway Administration, and it is hard to gauge the cost of a tunnel proposal using comparable projects. For one, there aren’t many major road tunnel projects under way in the U.S., though there are tunnels being built for transit, water and wastewater. Costs are driven by such local conditions as geology, labor, site access, surrounding infrastructure  and regulations, said Prof. Michael Mooney, who teaches underground construction and tunneling at the Colorado School of Mines.

For example, the Alaska Viaduct tunnel project in Seattle, where an elevated highway along the harbor is being replaced by a two-mile tunnel, is estimated at $3.1 billion, though delays have pushed it $223 million over budget, according to news reports last year. The recently completed PortMiami tunnel, two parallel 4,200 foot underwater highway tunnels, appears a relative bargain at $668.5 million.

Big plan

Larson’s idea, which he terms a “preliminary concept,” would include an east-west tunnel — possibly one large tunnel with the lanes on top of each other— of 4.5 miles running from Flatbush Avenue in Hartford under the southern tier of the city near Trinity College and Colt Park and then under the river to the Roberts Street area in East Hartford. The north-south tunnel would run 3.75 miles from the North to the South Meadows. The interchange would be a large cloverleaf under Colt Park.  

U.S. Rep. John Larson, D-1st District
U.S. Rep. John Larson, D-1st District file photo

The tunnels would be longer than the Big Dig’s Thomas P. O’Neill (Central Artery) and Ted Williams tunnels, which are 3.5 and 1.5 miles long, respectively, and currently constitute – at least according to some lists – the country’s longest road tunnel system. (The Federal Highway Administration considers the Central Artery a series of tunnels, and lists the Anton Anderson Tunnel in Alaska, which is 2.5 miles long, as the country’s longest single highway tunnel, according to spokeswoman Nancy Singer.) 

Larson acknowledges that the project will be expensive, but said so will the other options being considered. Also, new surface roads either north or south of downtown – two of the options the DOT is considering – could incite neighborhood opposition and cause major delays and disruptions; things that work underground would avoid. He said the tunnel would allow some existing highways and bridges to be refit as boulevards

Should the state embrace the concept, then comes the daunting challenge of paying for it. Looked at today, it appears impossible. Congressional earmarks – carve-outs from appropriations bills for particular projects (such as The Big Dig) – have been done away with; there is unlikely to be another federal transportation bill until at least 2020; and the state, which can barely keep highway rest stops open, is not exactly rolling in the ready green.

Well, said Larson, things change. President-elect Donald Trump spoke, albeit vaguely, of a trillion-dollar infrastructure investment. If something like that comes to pass, Connecticut needs to have projects ready to go. Also, Larson said, earmarks may come back under another name. Finally, he said, with interest rates low, the state could look to borrow money and create a new revenue source, such as tolls, to pay it back. Though Connecticut is the only state on the Atlantic seaboard without highway tolls, adopting them has thus far been a hard sell. Larson said the project could be built incrementally, spreading out the cost.


The DOT is not short of projects on which to spend federal infrastructure dollars –notably replacing the ancient moveable rail bridges on the New Haven railroad line and other measures to relieve the ghastly congestion in lower Fairfield County — but officials say they are open to considering Larson’s idea. DOT Commissioner James Redeker said the interchange congestion study the department just began “has components that are in synch with what the congressman proposes” and said he would include the tunnel proposal in the congestion study.

He said he “does not disagree” that the department should be looking at the long-term future of transportation in the Capitol region, and said the goal of the new interchange study is to produce a comprehensive, multi-modal vision for the next century. But he said replacing the aging viaduct is the immediate priority, and that the tunnel, like other options, must be subjected to rigorous study. 

Drilling tunnels 70 feet below Hartford raises a number of geological and logistical issues, but the threshold question is whether Mr. Larson’s premise is correct — that there is enough through traffic to warrant the construction of a vastly expensive tunnel system.

The idea, remember, is to funnel through traffic into the tunnel, and let local traffic proceed on the roadways into the city. The amount of through traffic depends on where it is measured. A study several years ago indicated that between West Hartford and East Hartford, about 40 percent of the cars and trucks were passing through. But engineers think that number drops considerably at rush hour, the time of highest congestion, when downtown workers and students are heading in or out and some drivers avoid the highway. Two years ago engineers studying the viaduct project decided not to propose a new ring road, both because of the cost and because they didn’t believe it would divert enough of the traffic to justify the expense (and overcome likely opposition).

While even a small percentage of traffic would be a substantial number of cars, it would be essential to know how many might use the tunnels.

Toni Gold praised Larson’s commitment to infrastructure repair and his regional vision, but said, “The traffic engineers have to take a look at this.”

Finally, even if traffic studies indicate the tunnels would work to lessen congestion, there then could be a timing or sequencing issue. If the tunnels were to be built, it would make sense to build them before removing the I-84 viaduct to lessen congestion during the reconstruction. But that would push the I-84 replacement back years, after a decade’s worth of work, and it’s not clear the decaying elevated highway has that kind of time left. In this scenario, Mr. Larson’s tunnel proposal may be too late.

The Aetna viaduct at Flower Street
The I-84 viaduct near Capitol Avenue Tom Condon /

Tom writes about urban and regional issues for CT Mirror, including planning, transportation, land use, development and historic preservation. These were among his areas of interest in a 45-year career as a reporter, columnist and editorial writer for The Hartford Courant. Tom has won dozens of journalism and civic awards, and was elected to the New England Newspaper Hall of Fame in 2016. He is a native of New London, a graduate of The University of Notre Dame and the University of Connecticut School of Law, and is a Vietnam veteran.

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