Synopsis

 

Freshgate Tunnel

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How much might a tunnel like this cost?

Difficult question: Since initial cost estimates of the Big Dig proved to be off by a factor of four, who would trust anyone's estimate of this? Still, if the tunnel costs $1 million per foot, then the whole thing might cost over $17 billion. If the tunnel costs $1 million per yard the cost would be over $5 billion. (One Big Dig final cost est. is $14.7 billion / 7.8 miles = $357,000/ ft., or about $1 million per yard.)

All tunnels are expensive, but computers & robotics are said to have made the cost of deep-bore tunnels plummet in the last decade - when bored in soft ground substrates like Boston-blue-clay.

  • Since it is only for autos & light vehicles, the 6-mile long A86 West Tunnel has a small (low-cost) diameter.
  • Its 45 mph speed limit further reduced its cost, since road & tunnel safety are cheaper to build-in for low speeds.
  • Since existing traffic doesn't need to rerouted while a deep-bore-tunnel is under construction, it is far less expensive to build: Only after a new tunnel is completely done is traffic disrupted while the entrance ramps from existing roadways to the new tunnel are built.
  • One estimate from the Big Dig has the cost set aside to keep existing interstates, streets, and sidewalks open during construction at nearly $5 billion, or one-third of the Big Dig’s total costs.

How much might the tunnel that Harvard is proposing for Soldier's Field Road cost?

Another difficult question. Harvard currently has only preliminary proposals, and certainly no cost estimates. It is too soon for Harvard University to know what it may finally propose - but their most recent planning report, issued June 2005 (prepared by the design firm Cooper Robertson Inc. http://www.allston.harvard.edu/vision/CRP_Interim_Report_June_2005.pdf) suggests a few tunnel possibilities, and may hint at others.
The only drawing in this report that shows depression of Soldier's Field Road is a sketch of an option for new undergraduate housing in Allston, near the Weeks Footbridge. Soldier's Field road is shown depressed from the Anderson Bridge to the Western Avenue Bridge (figure 8 on page 18). The one sketch shows about 2300 feet of Soldier's Field Road in a tunnel, between North Harvard Street and Western Avenue. (This estimate of the tunnel's length excludes the 200 ft entrance ramps shown at both ends of the depressed section.) If the unit price for such a tunnel were $357,000 per linear foot, the total cost would be $821,000,000 without the entry ramps, and might be $964,000,000 inclusive of the new ramped sections at both ends. However, the report's text includes references to more than one location for road depression. An excerpt from the text follows:

"Better access to the river would be a wonderful benefit to Allston and Cambridge residents and to the Harvard community. Soldiers Field Road blocks access to the river, and as noted earlier there are few crossings – the ones at Telford and Everett serve the Allston community, and Everett allows vehicular access to the amphitheater. Additional traffic lights could be installed between Everett and the Eliot Bridge. A more major and costly intervention might be to depress some parts of Soldiers Field Road. The obvious locations are at Newell Boat House, if undergraduate houses are built near Dillon Field House; or at the Weeks Bridge, especially if that becomes the chosen route for a new river crossing. Thesepossibilities require further exploration." (page 27)

If Harvard were to depress the entire 5300 feet of Soldier's Field Road between the Eliot and Western Avenue Bridges, at a unit cost of $357,000 per linear foot, the total cost would be about $1.9 billion. (This estimate again excludes entry ramp lengths from the calculation.)

Further, it may be fair to infer from the above excerpt that Harvard could eventually propose depressing Soldier's Field Road from Everett Street to Western Avenue, particularly since it seems unlikely Harvard would expect to receive public permission to depress only those parts of Storrow Drive that would wonderfully benefit the Harvard community but not as directly benefit Allston or Cambridge residents. If Harvard were to eventually suggest depressing the 8200 feet of Soldier's Field Road between Everett Street and Western Ave, again assuming a $357,000 per linear foot unit price, the total cost would be $2.9 billion.

Since the June 2005 Cooper Robertson report only deals with a 20-year planning horizon (page vii in Appendix B) it does not include discussion of Harvard's property to the south of Cambridge Street (the Mass Turnpike land and Conrail freight yards) which will be developed at a later time. The report hints at nothing about a possible full scope of Soldier’s Field Road/Storrow Drive depression that Harvard might envision in the future. If Harvard were eventually to suggest depressing Soldier's Field Road even further east than the Western Avenue Bridge, the total cost might be as follows: If Harvard suggests depressing the 12,350 feet of Soldier's Field Road between Everett Street in Allston and Buick Street in Brighton (the first side street west of the Boston University Bridge), again assuming a $357,000 per linear foot unit price, the total cost would be $4.4 billion.

The above calculations suggest that tunnels of the kind proposed in this website for elimination of river traffic along the Charles may be more cost effective than those currently under consideration for the Allston Initiative. Click on map below to view larger size

A Utopian Vision for Urban Expansion along the Charles River Basin