Chesapeake Bay Bridge-Tunnel
Chesapeake Bay Bridge Tunnel, officially, Lucius J. Kellam Jr. Bridge-Tunnel is a 28.4 km structure is situated on the East Coast of the United States. Until 2018, the Chesapeake Bay Bridge-Tunnel was the longest of its kind in the world but the title was taken over Hong Kong-Zhuhai-Macau Bridge which is approximately 41.7 km. The Chesapeake Bay Bridge-Tunnel or CBBT connects the Virginia mainland at the city of Virginia Beach directly with the Delmarva Peninsula in the state of Virginia in U.S.
The CBBT was completed in 1964 and comprises bridges, tunnels and land roads. The American Society of Civil Engineers recognized this iconic Bridge-Tunnel as one of the “Seven Engineering Wonders of the Modern World,” while being simultaneously one of the only 14 bridge–tunnel systems in the world. The Chesapeake Bay Bridge is nothing short of a Modern day Engineering Marvel with it dipping over and under open waters with a complex chain of artificial islands, tunnels and bridges.
-
Lucius J. Kellam Jr. Bridge–Tunnel
-
Chesapeake Bay
-
Fixed link: low-level trestle, 2 single-tube tunnels connected by artificial islands, truss bridges, high-level trestle
-
17.6 miles (28.3 km)
-
April 1964
-
$200 Million
-
over 140 million – As of January 2021
Initiation
Following the World War II, the population started gaining momentum, resulting in this region of Virginia to experience increasing ferry traffic across the mouth of the Chesapeake Bay, already a busy commercial shipping channel back in the days. By the mid-1950s, there were ferries carrying 50,000 people a month between the peninsula and the mainland, with significant delays and traffic snarls.
In 1956, the Virginia General Assembly recognized that the situation was only going to become a bigger problem, authorized the Chesapeake Bay Ferry Commission to explore the feasibility of a fixed crossing, a means of transportation across the bottom of the bay that did not require passage by ferry. The result was a series of recommendation for bridges and tunnels to cross the mouth of the bay.
Design
Among the key features of the Chesapeake Bay Bridge–Tunnel are two 1.6 km tunnels beneath the Thimble Shoals and Chesapeake navigation channels and two pairs of side-by-side high-level bridges over two other navigation channels: North Channel Bridge with 75 ft clearance and Fisherman Inlet Bridge with 40 ft clearance. The remaining portion comprises 19 km of low-level trestle, 3.2 km of causeway and four man-made islands.
The CBBT is 28.3 km long from shore to shore, crossing what is basically an ocean strait. Including land-approach highways, the overall structure is 37 km long with 32 km from one toll plaza to another toll plaza. It is remarkable that despite its length, there is a height difference of only six inches from the south to north end of the bridge–tunnel.
Man-made islands, each approximately 5.25 acres in size, are located at each end of the two tunnels. Between North Channel and Fisherman Inlet, the facility crosses at grade over Fisherman Island, a barrier island that is part of the Eastern Shore of Virginia National Wildlife Refuge administered by the U.S. Fish and Wildlife Service.
The columns that support the CBBT ’s trestles—called piles—would stretch for about 160 km if placed end-to-end, roughly the distance between New York City and Philadelphia.
Construction
In mid-1960, the Chesapeake Bay Ferry Commission sold $200 million in toll revenue bonds (equivalent to $1.37 billion in 2020 dollars) to private investors and the proceeds were used to finance the construction of the bridge–tunnel.
Funds collected by future tolls were pledged to pay the principal and interest on the bonds. No local, state or federal tax funds were used in the construction of the project.
Construction contracts were awarded to a consortium of Tidewater Construction Corporation and Merritt-Chapman & Scott Corporation.
The steel superstructure for the high-level bridges near the north end of the crossing were fabricated by the American Bridge Division of United States Steel Corporation. Construction of the bridge–tunnel began in October 1960 after a six-month process of assembling necessary equipment from worldwide sources.
The tunnels were constructed using the technique refined by Ole Singstad with the Baltimore Harbor Tunnel, whereby a large ditch was first dug for each tunnel, into which was lowered pre-fabricated tunnel sections cable-suspended from overhead barges. Interior chambers were filled with water to lower the sections, the sections then aligned, bolted together by divers, the water pumped out and the tunnels finally covered with earth.
The construction was accomplished under the severe conditions imposed by nor’easters, hurricanes and the unpredictable Atlantic Ocean. During the Ash Wednesday Storm of 1962, much of the partially completed work and a major piece of custom-built equipment, a pile driver barge called “The Big D”, were destroyed. In April 1964, 42 months after construction began, the Chesapeake Bay Bridge–Tunnel opened to traffic and the ferry service discontinued.
The Ferry Commission and transportation district it oversees, created in 1954, were later renamed for the revised mission of building and operating the Chesapeake Bay Bridge–Tunnel.
Expansion
The Bridge-Tunnel became insufficient for growing demand as the area was more widely developed. By 1989, officials decided a parallel structure composed of bridges and trestles would be required to accommodate both road and waterway traffic. The first expansion was completed in 1999 (ahead of the original 2000 deadline) and doubled the capacity of the bridge portion of the structure. A parallel tunnel was approved as part of a second expansion in 2013.
The project received three bids, all of which would use a tunnel boring machine. The winning company was Germanbased Herrenknecht, whose machine was 325 ft long. The machine was capable of moving forward through soil at 2.4 in per minute, or about 50 ft per day. At that rate, it was estimated that the tunnel would be dug within about one year. Construction work began in 2017 to prepare the location of the tunnels. After boring, the Construction was scheduled to finish in 2023.
By August 2022, the second tunnel at Thimble Shoal had been delayed to 2027.
Chesapeake Channel Tunnel Dualization (projected 2035–2040)
At the northern end, a parallel Chesapeake Channel Tunnel will be added to finish the entire length to become a four-lane highway from shore to shore. This project is marked to begin in 2035, which would possibly be open for traffic in 2040, assuming there are no setbacks or delays.
References
https://www.geoengineer.org/news/chesapeake-bay-bridge-tunnel-an-engineering-wonder-of-the-modern-world
https://www.cbbt.com/
https://www.britannica.com/topic/Chesapeake-Bay-Bridge-Tunne
