The builders of Metro’s Silver Line, under pressure to finish the project so that passenger service can begin just weeks from now, are behind schedule on many final work items, leaving transit officials worried about a potential delay of the rail line’s hoped-for summer opening, a top Metro manager said Monday.

Rob Troup, Metro’s chief of operations, noted that contractors working for the Metropolitan Washington Airports Authority, which is overseeing construction of the project, agreed in writing to complete 33 “punch list” items in time for riders to start using the Silver Line this summer. That memorandum of understanding was hailed in April as a big step toward finishing the current phase of the much-delayed project.

“However,” Troup told reporters in a conference call Monday, “we do have concern that the airports authority and the contractor are behind schedule on approximately half of the items we have listed” in the memorandum. He said: “This is work that has to be completed before we start [passenger] service. We expected them to be further along at this point.”

The Silver Line contractors, led by construction giant Bechtel, are known collectively as Dulles Transit Partners. The project’s first phase is 11.7 miles of track with four new stations in Tysons Corner and one in Reston. That was originally scheduled to be done by late 2013, and its current estimated cost is $2.9 billion, about $150 million over budget.

To hasten the start of passenger service, Metro agreed to take control of the Silver Line before the contractors had completed their work. The transfer of control, on May 27, allowed Metro to begin 90 days of testing the line, with the understanding that Dulles Transit Partners would finish the project in that period.

Although Troup on Monday declined to estimate when the Silver Line will open, he did not explicitly dash hope that it will be running by summer’s end. In making it clear that Metro is unhappy with the contractors’ progress, however, he seemed to be publicly prodding Bechtel and its partners to pick up their pace.

Referring to the 33 punch list items, he said, “Just a rough estimate, I would have expected maybe 25 or 30 percent of these items to be completed by this time, with a very specific schedule being shown [on] progress toward the other items being done.” But only about four items have been “closed out” so far.

“Does it concern us?” Troup said. “There’s no question it concerns us.”

Bechtel spokeswoman Michelle Michael responded, “We continue to work diligently in collaboration” with the airports authority and Metro.

“Good progress is being made every day,” she said. “Our focus is on safely delivering a world-class rail system to the people of Northern Virginia and the Washington metropolitan area.”

The final items listed in the memorandum of understanding range from such mundane tasks as installing locks on roll-up doors at one of the new stations to significant work such as fixing the automatic train-control system so that trains receive proper speed signals.

Some of the language in the agreement is jargon (“ceiling intersection guard for escalators” and “reclosure of the traction power gap breaker”), while other provisions are straightforward, requiring, for example, inspections of all station elevators “to confirm that there are no additional oil leaks or issues.”

Asked which work items the contractors are behind on, Troup would mention only two examples, having to do with handrails and drainage. “Those are the type of issues we’re looking at it,” he said. “I don’t want to weight or prioritize” all the behind-schedule work for fear of implying that some items are more important than others.

He cited “the painting and grounding of tunnel handrails. . . . We’re concerned about the work effort that was being done on that.” And he mentioned “some ‘ponding’ at the stations, where we have some drainage issues. . . . Obviously, we want to make sure we don’t have our passengers walking through water where it’s not draining properly.”

Starting from Wiehle Avenue in Reston, the Silver Line will meet the Orange Line at the East Falls Church station and share tracks with the Orange and Blue lines from Rosslyn to Largo Town Center. A second phase, involving different contractors, is supposed to be finished in 2018. That will extend the line from Reston to Dulles International Airport and into Loudoun County.

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