The potential for a tunnel link between Ketchikan and its airport on Gravina island increased on March 2 when The Boring Co. announced that a proposal from the Ketchikan Gateway Borough was among the 16 finalists in the firm’s Tunnel Vision Challenge.

The Boring Co. — founded by Elon Musk — is expected to announce the winner of the challenge on March 23.

With early encouragement and sponsorship by Assembly Members Rodney Dial and Sharli Arntzen, the borough moved quickly in recent weeks to develop its proposal for the Tunnel Vision Challenger, the winner of which qualifies for the construction, free of charge, of a tunnel up to 1 mile in length with an inner diameter of 12 feet, according to information from the company.

The borough’s 45-page proposal, which was approved by the assembly and includes a wide variety of letters of support, was submitted along with a Feb. 20 cover letter by Borough Manager Ruben Duran.

The company selected Ketchikan as one of 16 finalists from among 487 entries. The other finalists include five proposals from Texas, three from Tennessee, and one each from Arkansas, Colorado, Kansas, Louisiana, Maryland, New York and Panama.

The interest in a hard link such as a bridge or tunnel across Tongass Narrows goes back decades, heightened by the construction of the state-owned and borough-operated Ketchikan International Airport on Gravina Island in 1973.

Though borough-operated shuttle ferries serve the airport, the community and state and federal governments worked toward a project for a bridge or tunnel connection — an effort that culminated in the 2004 selection of a bridge option that would cross Tongass Narrows. Alaska’s congressional delegation was successful in securing substantial federal funding for the estimated $398 million project.

The cost of the project sparked national controversy, however, and eventually, then-Gov. Sarah Palin in 2007 canceled the bridge project, directed $25 million of the federal money for a road on Gravina Island and moved much of the funding elsewhere in the state.

A common thread in the letters of support for the borough’s Tunnel Vision Challenge application is that the interest in and need for a hard link to the island continues.

The Boring Co.’s specs for proposals are straightforward — up to one mile in length with an inner diameter of 12 feet.

“The tunnel can be a loop tunnel, a freight tunnel, a pedestrian tunnel, a utility tunnel, a water tunnel or any other case where a tunnel would be useful,” according to the company. The tunnel must be “physically reasonable to build and be able to be permitted in a reasonable amount of time.”

The borough’s proposal describes a single-lane vehicular tunnel with alternating directional traffic.