This cross-section of a twin bore tunnel is one possible subterranean design for the tunnel. The bore machines would have to be constructed for this particular project; making the machines along would take up to a year, according to the study.

Patrick Lohmann | plohmann@syracuse.com

Could a tunnel replace Interstate 81 in Syracuse?

On Monday, the results of a $2 million study were released that examine whether a tunnel is a feasible option to replace Interstate 81 in Syracuse. The study, done by WSP/Parsons Brinckerhoff, found that there are four technically feasible options for building a tunnel here. But they are expensive and time consuming: Ranging in price between $3.2 billion and $4.5 billion and taking nine or 10 years to build.

The elevated highway at the center of the city is aging and has been deemed a "classic planning blunder" by Gov. Andrew Cuomo. For several years, state engineers have deliberated and held hearing on what should be done to replace the highway.

The tunnel was one of three possibilities, but the Department of Transportation deemed it too costly and rejected it. After some local leader protested, Cuomo ordered that a tunnel study be conducted.

Former DOT Commissioner Matt Driscoll said the state has not yet decided whether a tunnel will be considered again. Officials are going through the study and will publicly announce their decision, he said.

The study outlines how a tunnel could be built, where it would go and what it would cost.

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Patrick Lohmann | plohmann@syracuse.com

Red, blue, green, orange

These four maps depict the four primary tunnel design possibilities, in addition to five that were rejected. The study authors rejected the possibility of building a "depressed highway" for I-81, saying it would "would further divide neighborhoods and close off more local streets," in addition to presenting "significant" construction challenges.

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Patrick Lohmann | plohmann@syracuse.com

The four most-feasible options

These are the four tunnel options the firm determined to be the most feasible. The three that roughly follow the path of Interstate 81 would cost between $3 billion and $3.6 billion.

The "blue" tunnel option at left would go along West Street and would cost $4.5 billion, according to the study's authors.

The authors ultimately recommended the Department of Transportation consider the "orange" option going forward.

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Patrick Lohmann | plohmann@syracuse.com

The "orange" option

In the "orange" option, a 1.6-mile tunnel would built, costing $3.6 billion.

It would also:

Take nine years to build.

Cost $10 million a year in maintenance costs.

Require the destruction of 12 buildings, including the possibility of the destruction of a historic building at 315 N. Salina St.

Require the replacement of the railroad bridge at Burt Street.

Pass under multi-story parking for Madison Towers and other private land.

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Patrick Lohmann | plohmann@syracuse.com

This a view of the "orange" option, looking southeast near downtown Syracuse.

The tunnel would be built just west of the current I-81 viaduct, starting south of Martin Luther King East and go due north. The tunnels would go under MLK and continue below vacant space at the Syracuse University steam station, Taylor Street, the Pioneer Homes housing project and parking structures for both the Upstate University Medical Center and Madison Towers.

At East Genesee Street, the tunnel would head northwest under private land and low-rise buildings before ending at Erie Boulevard.

When the tunnel surfaces and meets I-690, "extensive reconstruction of I-690 would be required," the authors write, including much of the existing viaduct.

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The study defines the advantages and disadvantages of the "orange" option as the following:

Advantages

Enables connections to I-690.

Relatively short tunnel.

Improvements to I-690's currently non-conforming features would be inclusive for this alternative.

Open view under new I-690 viaduct compared to existing wide viaduct.

Disadvantages

Passes under unused space at Syracuse University steam station and chilled water plant, with risk of encountering obstacles and need to protect sensitive utilities.

Passes under private land.

Passes under multi-story parking structure for Madison Towers.

Tunnel could limit future development requiring piles, such as on Townsend Street between Washington Street and Water Street.

Construction of northern tunnel approaches would be disruptive to I-690 traffic, requiring temporary connections and structures to divert traffic around the tunnel portal area.

Would require modifications to the existing West Street and I-690 interchange.

Other options the study looked at

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Patrick Lohmann | plohmann@syracuse.com

The "red" option

In the "red" option, a 2.2-mile tunnel would be built, costing $3.3 billion. It would also:

Cost $14 million a year to maintain

Require the destruction of 17 buildings, including the option of taking two historic buildings at 315/329 N. Salina St.

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This view is looking south along Interstate-81 toward downtown Syracuse.

Patrick Lohmann | plohmann@syracuse.com

The Red tunnel would be built juts west of the existing I-81 viaduct along South Townsend Street.

It would start south of Martin Luther King E and bend to the northwest, passing to the west of the SU steam plant.

The tunnel would generally follow South Townsend, passing below private residences and homes. Then it would turn northwest to align with STate Street, passing below private properties near Washington Street and Water Street.

The tunnel would pass under I-690 without connecting to it and instead follow North State Street before turning west to rejoin Interstate 81 north of Butternut Street.

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Patrick Lohmann | plohmann@syracuse.com

The study's author described the following advantages and disadvantages of the "red" option:

Advantages

Bypasses Syracuse University steam plant

Avoids risk of tunneling under I-81

Has negligible impact on I-690

Construction costs are relatively lower to other tunnel options and simpler compared to them.

Simpler construction staging compared to Orange.

Disadvantages

Does not provide a direct interconnection with I-690.

Passes under private land.

Passes under buildings, such as on Fayette St, North State St and North Salina Street.

Construction of northern tunnel approaches would be disruptive to I-81 traffic, resulting in a temporary reduction to two lanes for each direction between Butternut Street and Spencer Street.

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Patrick Lohmann | plohmann@syracuse.com

The "green" option

The "green" option, a 1.2-mile tunnel, would cost $3 billion.

It would also:

Take nine years to build

Cost $8 million a year to maintain

Require the destruction of two buildings, none of them historic

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Patrick Lohmann | plohmann@syracuse.com

This is the view looking west toward downtown.

The "green" tunnel would be built east of the I-81 viaduct, starting south of Martin Luther King East before arcing to the east before passing under Pioneer Homes and running adjacent to Upstate University Hospital.

It would run beneath the I-81 northbound off-ramp to Adams Street before surfacing along Almond Street and end at East Fayette Street.

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The study's authors described the following advantages and disadvantages of the "green" option:

Advantages

Enables connections to I-690, while limiting modifications to the existing I-690 roadways and structures.

Relatively short tunnel.

Requires less reconstruction of I-690 than the Orange Alternative.

Generally passes under public land.

Avoids Syracuse University steam plant.

Disadvantages

Confined space throughout.

Requires permanent closure of Water Street, Washington Street and East Fayette Street.

Passes close to foundations of hospital and Crowne Plaza Hotel.

I-690 WB to I-81 SB connection would be permanently removed.

Risk of encountering obstructions from I-81 viaduct and ramps.

Steeper tunnel at the southern entrance compared with other options.

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Patrick Lohmann | plohmann@syracuse.com

The "blue" option

The "blue option, a 2.6-mile tunnel, would cost $4.5 billion.

It would also:

Take 10 years to complete.

Cost $17 million a year to maintain.

Require the destruction of 22 buildings, none of them historic.

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Patrick Lohmann | plohmann@syracuse.com

This is a view of the "blue" tunnel looking north toward the Inner Harbor.

The "blue" tunnel would be built southwest of downtown and connect into West Street close to where it meets with I-690, ultimately continuing on to the Inner Harbor.

The tunnel would start south of MLK and head northwest from there, pass under the railroad and stay west of the SU steam plant.

The tunnel would pass under the southwest corner of Pioneer Homes, Roesler Park and low-rise buildings on South Warren Street.

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Patrick Lohmann | plohmann@syracuse.com

The study's authors described the "blue" plan's advantages and disadvantages as the following:

Advantages

Bypasses Syracuse University steam station & chilled water plant.

Less-confined space for a tunnel entrance site south of the railroad or south of Destiny Mall.

Avoids risk of tunneling under I-81.

Has limited impact on I-690 elevated section..

Uses existing West Street interchange for connecting to I-690

Interchanges with I-81 would be located in areas with available land.

Traffic on the existing I-81 and I-690 at the interchange would not be affected during construction.

Disadvantages

Longest tunnel.

Passes under private land.

Property acquisitions required at West Street.

Utility relocations required at West Street.

West Street interchange could experience heavy traffic.

Unknown depth of rock for much of the construction could result in cost increases.

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These are renderings of what Almond Street would look like without the viaduct.

Patrick Lohmann | plohmann@syracuse.com

All tunnel options take 'community grid' features on streets above

The study's authors also embraced several features of the "community grid" proposal in their description of what could be built above the former I-81 boulevard on the street level.

The street grid above the tunnels that would replace the existing elevated highway could be designed to better connect the city and ease traffic for bicyclists and pedestrians, the authors wrote.

"Removing the I-81 viaduct would free a large amount of land within the existing right-of-way for potential redevelopment and street improvements, including pedestrian and bicycle infrastructure, transit facilities, landscape, and street furniture," the authors wrote.

"As a physical and visual barrier, the viaduct has likely constrained the development potential for properties adjacent to the structure," they said.

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Patrick Lohmann | plohmann@syracuse.com

What's the next step?

The state is now evaluating results of the study to determine whether building a tunnel will be reconsidered as an option. Officials would not estimate when they might make that call.

The study did not make a recommendation on whether the tunnel was the right way to replace I-81. It looked at whether a tunnel could technically be built, the cost, the length of construction and what might be the best way to do it.

DOT officials will seek additional public comment before ultimately determining what the best option is.

After that, construction begins.

More coverage:

Syracuse Mayor Stephanie Miner on new I-81 study: Scrap the tunnel idea

John DeFrancisco: Interstate 81 study proves tunnel is feasible option

I-81 tunnel: Project would take up to $4.5 billion, 10 years, long-awaited study says

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I81 Independent Feasbility Study Report Nov2017 by PatLohmann on Scribd

Here's the full study