Double Time

Construction crew takes the express route to double-tracking Baltimore's light rail system

By Jim Parsons

From residential backyards to the middle of nowhere, construction teams are carefully navigating a path toward completion of the $150 million 9.5-mi. light rail project in Baltimore.

The $150 million project includes new 4-ft., 8.5-in.-gauge tracks on more than 20,000 8-ft., 3-in. concrete ties, and 435 20- to 40-ft.-long steel catenary poles on poured concrete foundations for the overhead high-voltage lines.

A deliberate, extended shutdown normally is not a good thing for a public transit system serving more than 30,000 passengers daily, but for the Maryland Transit Agency, idling large portions of the Baltimore Light Rail system put a 9.5-mi. double-tracking project on the fast track to completion.

Twin tracks were part of the overall vision for the 29-mi. electrified system, which runs north-south from Hunt Valley to Cromwell Station/Glen Burnie. Due to funding shortfalls, approximately 40 percent of the system remained single track when operations began in 1992. These segments, ranging in length from just over 1,000 ft. to nearly 2 mi., were spread across the system, limiting MTA's ability to expand service and coordinate maintenance.

"For the most part, we had room for double tracks in the right-of-way, and most of our 33 stations were built with platforms on both sides," said Steve Silva, MTA's director of engineering and construction. "What we lacked were the rails themselves."

Cleared for completion

Funds from TEA-21 and the state provided the $150 million MTA needed to begin filling its rail gaps in 2003. The project includes new 4-ft., 8.5-in.-gauge tracks on more than 20,000 8-ft., 3-in. concrete ties, and 435 20- to 40-ft.-long steel catenary poles on poured concrete foundations for the overhead high-voltage lines. Eight track segments are included in the project.

Only spurs to downtown Penn Station and Baltimore-Washington International Airport, plus the extreme north end of the system, will remain single track due to unfeasible geometrics and right-of-way constraints.

Each of the eight segments presented a unique set of challenges. While much of the right-of-way averages 66 ft. wide, the close proximity of buildings, roads and terrain in some locations left little room to work and stage equipment. Some segments required relocating existing tracks, catenary poles and other equipment from the middle of the right-of-way to make room for a parallel rail line.

Dozens of underground utilities also had to be identified and relocated. And, two major bridges would be needed to carry the new tracks through the south end of Baltimore's Inner Harbor.

"That meant preparing for a full range of work settings, from residential backyards to what seemed like the middle of nowhere," said project manager Ken Merrill of construction manager PRW, a Baltimore-based joint venture of Parsons Brinckerhoff; Rummel, Klepper & Kahl; and Wallace, Montgomery & Associates. "That's on top of the safety considerations of working within an active rail line."

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Switching service

MTA was also concerned about how repeated service interruptions would affect its customers, even with an aggressive public outreach program of community meetings, fliers and dedicated Web site.

"As we started to do more of the physical work, it became apparent that the best way for the project to proceed was to shut down one half of the system at a time," Silva said. "This would allow the contractors to work more efficiently and safely, limit repeated inconveniences to our customers and eliminate the need for nighttime construction in the neighborhood areas."

With MTA shuttle buses providing a temporarily substitute for rail service, the shutdown began on the system's South Line from Camden Yards to Cromwell in February 2004. Construction workers made the most of the train-free environment, constructing new tracks in four segments with seven grade crossings, two new traction power substations and new signals and switches. New 500-ft., cast-in-place platforms were built at three stations, each with raised sections to accommodate disabled passengers.

One of the toughest locations was the system's junction with a single-track spur to BWI.

"We had to install six switches, each with a complicated conduit system, and two rail crossovers in a relatively small area," Merrill said. "With very tight tolerances and little room to make adjustments, we needed a lot of coordination to make everything fit."

A new direction

Approximately 40 percent of the 29-mi. electrified system was single track when operations began in 1992, but contractors on the recent double-tracking project had enough room build in most of the existing right-of-way.

The benefits of MTA's shutdown strategy proved better than expected. With the South Line's double-tracking completed more than four months ahead of schedule, full service resumed in December.

Attention has now turned to the somewhat more complicated North Line, which was shut down in January. Here, MTA shares a portion of its right-of-way with an active freight line, requiring double-tracking construction to be coordinated with periodic deliveries of rail cars.

"Fortunately, it's only a few cars once a week, but we still have to coordinate with the railroad to make sure the tracks and switches are operational," Merrill said.

The North Line's upland terrain and close proximity to other features such as Interstate 83 and parkland has presented some additional civil engineering issues.

"During construction, the existing conduits were found to be much closer to the steep western slopes than indicated on the as-built plans," said MTA project manager Matt Fenton. "That required additional excavation into the slip plane of the slopes."

Four slope areas ranging from 90 to 250 ft. long required further stabilization to minimize risk to the light rail line. Two were stabilized with additional grading and landscaping. Another area required a soldier-pile wall with concrete lagging, while the fourth was fitted with a shotcrete wall anchored with 10-ft. soil nails.

A good track record

A row of more than 30 concrete piers stood parallel to the MTA Light Rail System's .75-mi. crossing of Middle Branch in downtown Baltimore for nearly 15 years. Built as part of the original system, the piers were intended to provide ready-made infrastructure for the day when funds for double-tracking became available.

The double-tracking project has offered some glimpses into the past.

"The North Line is one of the oldest railroad rights-of-way in America with many historic structures," Fenton said. "We've been careful when working near certain abutments and a privately owned 19th Century station."

Workers also uncovered several marble rail ties from a long-ago rail line. "We were not permitted to disturb them, so we noted the location and reburied them in place," Merrill said.

Silva said he is confident that the shutdown will duplicate the South Line success with an early restart of service.

"Our schedule says 2006, but we're working toward a partial reopening this summer and completion in December," he said, adding that MTA's passengers have generally accepted the short-term inconveniences in exchange for long-term benefits.

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