Transit - Award of Merit

Blue Line Extension to Largo Metrorail
Prince George's County, Md.

For the first time in its 25-year history, the Washington Metropolitan Area Transit Authority used a design-build process to extend its Metrorail system 3.1 mi. into Prince George's County, Md., and it shaved two to four years off a typical design-bid-build schedule.

"This is a signature project for transportation in the Washington, D.C., area," said one of the judges. "It was well managed, and the team utilized some interesting subcontracting techniques to get the job done."

The design-build team, a joint venture named LGS, included the Lane Construction Co. of Meriden, Conn.; Granite Construction Inc. of Watsonville, Calif.; Slattery Skanska of Whitestone, N.Y.; and lead design firm Jacobs Engineering of Pasadena, Calif.

Washington Metropolitan Area Transit Authority began planning the Blue Line extension to Largo during the mid-1990s and awarded LGS a $218 million contract in 2002. It included civil work, track work, traction power, mechanical, electrical, communications and train controls and testing.

WMATA expected to open the line in December and is anticipating daily ridership of about 30,000.

Clark-Kiewit Largo, a joint venture of Clark Construction of Bethesda, Md., and Peter Kiewit Sons' Inc. of Omaha, Neb., received the $92 million contract for two transit stations and support structures. LGS and Clark-Kiewit closely coordinated work on the project.

The line work consisted of 11,200 ft. of cut-and-cover double-box tunnel construction - with a concrete wall separating inbound and outbound track - and 3,150 ft. of aerial structure.

Rather than using 3-in.-thick timber lagging and soldier pile, WMATA's traditional shoring process, LGS placed 8-ft.-wide by 20- to 30-ft.-deep, .75-in.-thick sheets of metal-plate lagging through clay and sand-based soils for use as temporary retaining walls.

Bulk earthmoving progressed without interruption to install timber lagging. Crews used timber lagging in those places where the metal-plate lagging failed to go in all the way or was impossible because of utility crossings.

In another innovative aspect of the project, LGS convinced WMATA to allow it to reduce the level of bracing in the cut excavation to one bracing level for up to 30 ft. of depth. The line passes through a wooded residential area with no structures, streets or utilities in its path, so ground movement and settlement did not present as great a concern as it normally would.

LGS used a top-down direct fixation track construction to speed construction. It also incorporated drainage into the track slab, instead of below, which is WMATA's normal placement.

Crews placed tunnel-box rebar ahead of the tunnel traveler form. A concrete maturity measuring device allowed stripping of forms as quickly as possible.

The line uses jet fans instead of conventional tunnel ventilation fans. The original design did not meet National Fire Protection Association 130 standards, necessitating a redesign that affected all areas of construction.

TSC/WSC Joint Venture, made up of Truland Systems Corp. of Arlington, Va., and Walker-Seal Companies Inc. of Fairfax, Va., was responsible for all of the electrical, traction power and communications systems. LGS maintained control of the power through the train-testing phase of the project.

Owner: Washington Metropolitan Area Transit Authority
Design/Builder: "LGS Lane Construction Corp., Granite Construction Inc., Slattery Skanska"
Design Services: Jacobs Civil Inc.
Design/Automatic Train Control: "L.K. Comstock & Company, Inc."
Fabricated Metals: Continental Construction
F&I Bridge Steel: Genesis Steel Service
Mechanical Systems: "Joshua Construction, Inc."
Trackwork: "Balfour Beatty Rail Systems, Inc."
F & I Rebar: "Midasco, Inc."
Concrete Piling: MIDLANTIC Piling Inc.
Waterproofing: Prospect Waterproofing
Low Voltage/Traction Power: Communication: Truland Systems/ Walker Seal JV

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