Transportation

Second Midtown Tunnel Construction Passes Halfway Mark

Midtown Tunnel Segments

©2015 SKW CONSTRUCTORS

Each tunnel segment measures about 106 meters (350 feet) long and was designed by Parsons Brinckerhoff.

A half-century after designing the Midtown Tunnel between Norfolk and Portsmouth, Virginia, Parsons Brinckerhoff designed the Second Midtown Tunnel, which when completed will double traffic capacity across the Elizabeth River.

Since the first Midtown Tunnel was built in 1962, it has operated as a two-lane, bidirectional thruway along US Route 58. When it opened, it accommodated 8,400 vehicles a day. Today that volume has increased to 38,000 vehicles.

“This is the most heavily travelled two-lane road segment east of the Mississippi River,” says Derek Piper, Deputy Design Manager for Parsons Brinckerhoff. “It greatly exceeds capacity, and because there are not many options to re-route traffic, everything shuts down if there is a breakdown or closure.”

Parsons Brinckerhoff played a role in the design of all four Elizabeth River tunnels, including the first Downtown Tunnel, which opened in 1952; and the second Downtown Tunnel, completed in 1982. Parsons Brinckerhoff also designed the Hampton Roads bridge-tunnel crossings, completed in 1957 and 1976.

Time Saver

The new two-lane Second Midtown Tunnel, together with other traffic improvements in the area, will cut travel time by an average of 30 minutes per trip during peak commuting hours, Piper says. The project recently passed the halfway point and is slated for a December 2016 opening.

Parsons Brinckerhoff is lead designer for SKW Constructors, a joint venture of Skanska USA Civil Southeast, Kiewit Construction Company, and Weeks Marine. SKW is the design-build team for the owner, Elizabeth River Crossings, a corporation created to execute the project under a public-private partnership (P3) with the Virginia Department of Transportation.

Second Midtown Tunnel

©2012 PARSONS BRINCKERHOFF

This rendering shows a cross-section of the Second Midtown Tunnel, including the egress and utilities corridor and the jet-fan ventilation system.

The $2.1 billion project also includes rehabilitation of the existing Midtown Tunnel, improvements to the two existing Downtown Tunnels, and a 1.6 kilometer (1 mile) extension of the Martin Luther King Jr. Freeway—an elevated four-lane, north-south expressway with a raised median that will provide an enhanced link between the Midtown and Downtown tunnels in Portsmouth.

Parsons Brinckerhoff is currently providing construction-phase services, which includes plan revisions, responses to requests for information, shop drawing review, preparation of non-conformance reports, foundation inspection, and tunnel monitoring.

First for Hampton Roads

The Elizabeth River Tunnels Project is the largest design-build project in the history of the Hampton Roads region. The Second Midtown Tunnel is the first deep-water concrete immersed tube in North America, and the second all-concrete immersed tunnel in the US.

Parsons Brinckerhoff recommended the all-concrete option for the two-lane tunnel over a more conventional design using a steel tube encased in concrete. “It offered substantial economic savings resulting from changing the immersed-tube sections to a shallower rectangular configuration, thus reducing the scale of the steel fabrication,” says Fred Parkinson, Design Manager for Parsons Brinckerhoff. “The use of reinforced concrete in lieu of fabricated steel also significantly reduced the schedule risk for SKW, since tubes could be constructed without relying on specialized steel fabrication labor.”

The Second Midtown Tunnel measures 1,280 meters (4,198 feet) from portal to portal. The total length of the tunnel is 1,658 meters (5,441 feet) from end to end. It required digging a trench that is up to 29 meters (95 feet) deep below the river bottom.

Chesapeake Journey

The tunnel is being constructed by piecing together 11 hollow concrete tunnel segments, averaging 106 meters (350 feet) long, 8.5 meters (28 feet) high, and 16.5 meters (54 feet) wide.

Midtown Tunnel Construction

©2015 SKW CONSTRUCTORS

The tunnel is being constructed by connecting 16,000-ton concrete segments that were cast 320 kilometers (200 miles) north of the construction site, and transported down the Chesapeake Bay.

SKW transported each 16,000-ton segment from the fabrication site at Sparrows Point, Maryland, 320 kilometers (200 miles) north of Norfolk, to the construction site. Six of the segments are now on-site, four of which have been placed within the dredged trench under the Elizabeth River. The five remaining sections will make the trek from Sparrows Point at intervals of about one a month starting in March.

“The tunnel elements are towed through the Chesapeake Bay with all but about two feet of the segment submerged during transit,” Piper says. The trickiest part of the journey was crossing over one tunnel section of the Chesapeake Bay Bridge-Tunnel, then turning it nearly 360 degrees in the Atlantic Ocean in order to access the Norfolk Channel, then crossing over another tunnel section of the Chesapeake Bay Bridge-Tunnel.

Updated Technology

When completed, the tunnel will feature bright, long-lasting, and efficient LED lighting, and will be the first Virginia tunnel to use an all-electronic toll collection system. The intelligent transportation system will include 60 closed-circuit cameras with automated incident detection capability and dynamic message signs along the project corridors.

Under the P3 agreement, ERC will be responsible for management and operations of the roadway over a 58-year period. After that time, operations will be returned to VDOT.

The MLK Freeway extension will include a new trumpet-style interchange with Interstate 264, a partial diamond interchange with High Street, and bridge crossings through urban Portsmouth incorporating aesthetic and lighting improvements. The elevated roadway also crosses CSX Transportation’s Portsmouth yard.

The extension will provide a limited-access connection between the MLK Freeway and I-264, which will reduce congestion on local Portsmouth streets.

“One benefit of the new freeway extension is that it will provide an alternative route for I-264 traffic when the Downtown Tunnel is congested or closed,” Piper says.

Relocated Water Main

The tunnel project also required relocation and replacement of an existing 76-centimeter (30-inch) raw water transmission main crossing the Elizabeth River owned by the City of Norfolk, as well as robust support of the excavation system to avoid impacts to the Hampton Roads Sanitation District (HRSD) 106-meter (42-inch) sanitary force main crossing the Elizabeth River.

“The City of Norfolk was a very willing partner,” Piper says. “The project essentially paid to replace an aging water line, and since they had a redundant raw water line to use during the replacement, service was not interrupted.” In early 2013, the relocation of 2,200 meters (7,200 feet) of water main line was successfully completed.

There was a bit more reluctance from HRSD about the sewer line, since there was no re-route option, and an accidental puncture of the line could have severe environmental – and financial – consequences.

First Midtown Tunnel

©PARSONS BRINCKERHOFF ARCHIVE PHOTO

Parsons Brinckerhoff designed the first Midtown Tunnel, which opened to traffic in 1962, and both Downtown Tunnels, which were completed in 1952 and 1982.

“We went through extensive effort to ensure we avoided the sewer line,” Piper says. “Dredging was completed without any issues and included a significant monitoring program. The sanitary force main was never out of operation.”

High-Profile Project

With substantial media coverage of the new tunnel, most locals are keenly aware of the project and its progress. Thus far, the reports have been favorable, and the project is currently ahead of schedule.

“It is a high-profile, well-scrutinized project,” Parkinson says. “Now that the tunnel and roadways are starting to take shape, people are really starting to take note of the improvements.”

“It’s such an important part of where we live, work, and play,” Piper adds. “I’m very proud to be a part of this historic project.”

For more about the Second Midtown Tunnel and the use of virtual design and construction on the project, see this month’s video.

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