Colossal $1.5B Elizabeth River Tunnels on Track for Year Early Completion
A design-build team has completed one of the country's first immersed tube concrete deep-water tunnels, between Portsmouth and Norfolk, Virginia, six months ahead of schedule and is on track to complete the entire four-part project a year early.
"It was hard work, good planning, cooperation and flawless execution," says Wade Watson, Project Director of the design-build team of SKW Constructors, a joint venture among Skanska USA Civil Southeast of Virginia Beach, Virginia; Kiewit Infrastructure Co of Woodcliff Lake, New Jersey; and Weeks Marine of Cranford, New Jersey.
"Looking at delivering the entire $1.5 billion construction project one year ahead of schedule is a huge accomplishment," says Dan Norman, Construction Director for the concessionaire Elizabeth River Crossings (ERC), a joint venture of Skanska Infrastructure Development in Alexandria, Virginia, and Macquarie Infrastructure and Real Assets of Australia, responsible for designing, building, operating, maintaining and financing the project.
"It's a testament to the team to deliver a project this complex not only on time but ahead of schedule," says Bradley Weidenhammer, Megaprojects Engineer for the Virginia Department of Transportation (VDOT).
P3 Moves Job Forward
VDOT awarded the ERC team the $2.1 billion contract, with a financial close in April 2012. The original completion date was August 2018. The job is expected to complete one-year early. Traffic has increased 600 percent since the first Midtown Tunnel opened in the 1960s. Daily morning and afternoon backups were occurring.
"The new Midtown Tunnel is needed for congestion relief and adding capacity," Weidenhammer reports. "The other piece is safety."
The original tunnel had two lanes of traffic, one in each direction, and many of the vehicles were trucks. Now east- and westbound traffic flows in different tunnels.
VDOT decided on a public-private partnership to move the project forward and assign some of the risk to the concessionaire, Weidenhammer says.
"The P3 allowed us to undertake the project at a fixed cost and accelerate the schedule," Weidenhammer adds.
The concessionaire will collect the tolls during the 58-year concession period. The Elizabeth River Tunnels project was Skanska's first public-private partnership in the United States. The connectivity the project brings to the Hampton Roads region attracted ERC to the project, Norman says.
In addition to constructing the 3,800-foot-long, two-lane tunnel, adjacent to the existing Midtown Tunnel, the $1.5 billion design-build scope of work has included extending the MLK Expressway in Portsmouth about 2 miles from London Boulevard to Interstate 264; and upgrading the two Downtown Tunnels and the existing Midtown Tunnel.
SKW Constructors had four different delivery dates for the various components of the Elizabeth River Tunnels project. Traffic began flowing through the new Midtown Tunnel in this summer. The MLK Expressway portion is scheduled for completion in December of this year.
The new Midtown Tunnel was the first underwater tunnel to open under the new Federal Highway Administration National Tunnel Inspection Standards. All of the improvements to the existing tunnels will meet those standards.
SKW Constructors precast gigantic concrete boxes that create the tunnel in the Baltimore area. The precast concrete tunnel "allowed us to reduce the overall height of the tunnel elements, so it required less dredging and made it more economical, and you can be more flexible with a concrete design," says Norman.
Prior to immersing the concrete boxes, SKW Constructors dredged a trench with a gigantic crane and a clamshell bucket up to 95-feet under water and prepared a minimum 3-foot gravel bed in the bottom of the trench on which to place the tunnel elements.
"We had to level that bed off to an elevation of plus or minus 1 inch, 95-feet underwater from a floating vessel," Watson says. "A technical challenge, but we exceeded that."
The tunnel is made up of 11 rectangular segments, 342feet long, 28.5 feet tall and 54 feet wide, with each element cast in a graving dock near Baltimore and floated to the construction site in Portsmouth. Each element weighed 16,000 tons.
"We floated the tunnel elements to the site, 200 miles down the Chesapeake Bay and placed them into a large catamaran-style lay barge, which controls the descent of the tube, to the bottom of the Elizabeth River, using ballast," Watson says.
All work took place from barges, with divers checking the placement. One end of the boxes has a steel ring and the other an "O ring or Gina rubber gasket" around the adjacent tunnel.
"That's the first of three seals used to make the tunnel elements watertight," Watson explains. "We evacuate the water between the bulkheads, and it creates negative pressure, which squeezes the gasket."
The weight of the tunnel restrains the tunnel in place. Crews picked up the new tunnel segment until it was engaged with the segment already in place and the rubber compressed. Then they put another rubber seal, an Omega gasket, on the inside. Once that is in, it is good for twice the load the tunnel is expected to see, Watson says. Then, once the Gina and Omega gaskets were in place and secure, the element junctions were encased in concrete to provide a structural cover.
With the tunnel in position, SKW Constructors poured concrete in the bottom of the tunnel to create the curve of the road and then paved the road atop that. At both ends, crews added retaining walls for an open approach and constructed a cut-and-cover section, with the immersed tunnel on one end and the approach section on the other. A building above it supports the mechanical and electrical gear.
Rather than the tunnels meeting in the middle with a closure piece, SKW Constructors decided to move the closure to the end.
"It did not impact the [navigational] channel and let us tie in on a dry environment," Watson says.
SKW Constructors created emergency exits within the tunnel by constructing a pedestrian corridor adjacent to the roadway. Every 300 feet in the new Midtown Tunnel, a door is in place that leads vehicle drivers and passengers from the roadway to the egress corridor and out of the tunnel. Emergency responders enter the tunnel from another way.
On the existing tunnels, "we found ways to decrease the construction time on the rehab of existing tunnels, and part of that was starting when the new tunnel was under construction," Norman says. That work took place on evenings and weekends.
The upgrading of the three existing tunnels included structural repairs, fireproofing, mechanical and electrical work, and repaving and striping.
"It's good for the general public, VDOT, the developer and the contractor," Watson says. "It's a win-win-win."
Helping the Community
VDOT included in the contract an on-the-job training component to the project. The department required that 70 individuals complete the program. SKW Constructors has put 86 people through the program and supported charities in the Hampton Roads area.
"It helps VDOT in the future to have a well-trained workforce for future projects," Weidenhammer says. "I'm proud of the project team for exceeding the goal."
U.S. Senators Tim Kaine and Mark Warner gave the graduates letters of commendation. Seventy-three percent of the students reside in Hampton Roads, and 60.5 percent of students are minorities.
"It was an aggressive goal, but we exceeded it," Weidenhammer says. "The goal of these projects is not just to invest in infrastructure but in the local workforce as well."
The team also has reached out to school children, scouts, professional organizations and citizens. When the new tunnel opened to both lanes of westbound traffic in August, ERC held a 5k run through the tunnel to give people a new perspective of the tunnel. Proceeds went to local food banks.
VDOT anticipates the project will generate between $170 and $254 million in gross regional productivity in the Hampton Roads area. Additionally it should save the round-trip driver about 30 minutes daily.
Photos courtesy of Elizabeth River Crossings