Dive Brief:

• Pasco County, Florida, officials are considering a plan to build a $550 million tunnel underneath a chronically congested intersection about 20 miles north of Tampa, according to the Tampa Bay Times. This "cut and cover" approach would cost more than four times that of one of the alternatives, which would see the construction of a $134 million system of elevated lanes. Not included in the price of either plan is $70 million in land acquisition costs and long-term maintenance.
• A citizen's task force recommended elevated lanes, along with three other options, to ease the flow of traffic at the intersection but did not evaluate the tunnel, which the county's Metropolitan Planning Organization (MPO) suggested in January. Even though the consensus is that the Florida Department of Transportation (FDOT) will not likely agree to such an expensive project, the MPO agreed to study the tunnel option for 30 more days after one member of the Pasco County Board of County Commissioners requested they do so. Critics argued that only 20% of traffic moves straight through the intersection and that 80% make a turn, meaning that a tunnel would still result in significant congestion.
• According to a Pasco County memorandum, if the MPO decides not to move forward with the tunnel option, it will work with the FDOT to determine scopes of work and begin feasibility studies on the four options favored by the task force. There are approximately 100,000 cars that use the intersection every day, and that number is expected to double by 2040. 

Dive Insight:

Aside from the challenge of raising such a huge sum of money for a tunnel project like the one proposed for Pasco County, there is also the issue of building a tunnel in an area where the necessary digging is sure to hit water. In addition, Pasco County has also recently seen more than its fair share of sinkholes, which are reportedly increasing in number all over Florida. Construction that involves drilling, the pressure of heavy structures on the ground or any significant change to the land's surface can cause sinkholes, according to Conserve Energy Future.

Nevertheless, tunneling operations can be challenging and costly no matter where they are carried out.

Progress on Seattle's $2.2 billion Alaskan Way tunnel, which could see vehicular traffic as early as this fall, was delayed more than two years after the tunnel boring machine broke down. In New York, a $2 million feasibility study conducted by WSP Global-Parsons Brinckerhoff revealed that a tunnel through downtown Syracuse would cost between $3 billion and $4.5 billion, leaving the mayor to continue to advocate for a $1.3 billion surface street redevelopment instead.

Completed tunnels can represent notable engineering and construction achievements, but the process can be a risky one.