Chesapeake Bay Bridge-Tunnel (CBBT) has announced that the Parallel Thimble Shoal Tunnel Project in the US state of Virginia has hit a major milestone.

The 13.1m diameter tunnel boring machine (TBM) ‘Chessie’ successfully broke through the receiving pit on Two Island at Thimble Shoal Channel, reaching her end destination.

CBBT said the 325ft-long TBM will complete the final phase of mining once the temporary bracing struts and steel beam are removed from the receiving wall.

The $756m tunnel project involves constructing a 5,700ft bored tunnel connecting two southbound trestles of the existing Chesapeake Bay Bridge-Tunnel. The structure links the Norfolk/Virginia Beach area to Virginia’s eastern shore.

CBBT Commission chairman Fred Stant said: “The parallel tunnel is a key component of enhancing the safety and efficiency of this vital transportation link and demonstrates the CBBT Commission’s commitment to advancing infrastructure and ensuring the long-term sustainability of the Chesapeake Bay Bridge-Tunnel.”

The tunnel boring machine for this project was designed and built by Germany-based Herrenknecht.

With a 43ft cutter head and a length of 308 ft, Chessie excavated around 500,000 cubic yards of soil and installed nearly 10,000 concrete segments, each weighing 10 tons.

The design-build contractor for this project is Chesapeake Tunnel Joint Venture (CTJV), a partnership between Dragados USA and Schiavone Construction Company.

Both firms are part of Spain-based ACS Dragados, a global underground construction company. ACS Dragados has been awarded over 550 underground projects and completed more than 940 miles of tunnelling through various geological conditions.

Mining for the two-lane, 1.6km long tunnel started in February 2023. In May 2023, Chessie encountered a large ship’s anchor, dating back to the early 1900s and manufactured in England.

The obstruction caused an eight-month delay for safe removal. Tunnelling resumed in May last year, with progress averaging 15.2m daily.

CBBT executive director Jeff Holland said: “This breakthrough represents the culmination of extensive planning, engineering precision and complex construction work during the planned and unplanned phases of the tunnel mining. 

“We especially commend the work crews who operated in a high-risk environment to remove the anchor obstruction without injury or loss of life.”

CTJV will begin constructing the tunnel roadway, installing electrical and mechanical systems, and building support structures.

Upon completion, the new tunnel will carry southbound traffic, while the existing tunnel will handle northbound traffic.

The project is currently forecasted for completion in early 2028.