Phase 2 construction on Metro's Silver Line at Dulles International Airport is seen in July 2017. (Katherine Frey/The Washington Post)

Hundreds of concrete rail ties installed at track crossovers along the second phase of the Silver Line are flawed, officials say, a problem that could further delay the multibillion-dollar rail project that is already 13 months behind schedule.

Capital Rail Constructors, the lead contractor on the project, discovered the flaws in September, but the company and project officials have been unable to agree on a fix.

Charles Stark, executive director of the Silver Line rail project, said the issue centers on more than 400 concrete ties that support the rails in areas where multiple sets of tracks come together. The ties are higher in the middle — in some cases as much as a half-inch higher — than on the ends.

This is problematic because the ties may cause the tracks to tilt outward. The result, Stark said, is that a train going over those sections of track could lean slightly toward the outside. He said the issue may lie in how the ties were made.

But the manufacturer of the ties, Rocla Concrete Tie, denied that they are faulty and said they meet project specifications.

This is at least the third time flaws in concrete structures on the project have surfaced since CRC, a joint venture between Bethesda-based Clark Construction Group and Kiewit Infrastructure, won the contract to build the second phase of the rail line in 2013.

Keith Couch, project director for CRC, said the ties passed all quality-control tests, except those tests that can only be done once the ties are installed. It was then that CRC’s inspectors discovered they did not meet project standards.

“Capital Rail Constructors is driving towards the delivery of Phase 2 of the Silver Line project in support of [the Washington Metropolitan Area Transit Authority’s] goal of revenue service in 2020,” the company said in a statement. “As we enter the final phases of the project, our experienced team of engineers and builders will continue to work with [the Metropolitan Washington Airports Authority] and WMATA to proactively resolve any issues that arise during the normal course of construction to achieve our objective of delivering a high-quality facility that will serve the region for generations to come.”

But given this newest round of problems, some have begun to wonder whether CRC can deliver on that pledge.

“We shouldn’t be having problems with the concrete,” said Sharon Bulova, chair of the Fairfax County Board of Supervisors. “That is not okay.”

Couch said CRC has replaced some ties on the west segment of the rail line and said it would install shims on the eastern segment to correct the problem. The shims would be used to “even out” the tracks.

But MWAA, which is overseeing construction of the $5.8 billion rail line, and Metro, which will be responsible for managing and maintaining the rail line once it is completed, have rejected that solution.

“Metro and the Airports Authority have concluded that the contractor’s proposed remedy, which would keep the current ties in place, would result in significant ongoing maintenance issues and is therefore unacceptable,” Metro spokeswoman Sherri Ly said. “This issue must be corrected in order for the project to be accepted by Metro.”

Bulova endorsed that decision.

“I am with MWAA in insisting that a satisfactory resolution be agreed to,” she said.

Stark said the costs associated with fixing the problem will be CRC’s responsibility. As for the impact on the project’s schedule, he said unless he hears otherwise from the contractor, the extension is expected to reach “substantial completion” in August. That’s the point at which the contractor has finished work and the project is ready for Metro to test and take over. Couch said it is too early to know whether the tie issue will prevent them from meeting that August deadline.

In 2015, CRC halted work on the rail project after cracks were found in the girders that support the tracks at Dulles International Airport. Then earlier this year, it announced that there were issues with the concrete panels installed at five of the six stations under construction. Each time, the company pledged stricter quality control, but the news that there are now problems with hundreds of concrete ties raises questions about whether the company is making the necessary changes.

Couch maintained that CRC has a “robust” quality-control and assurance program.

The company is still working to remedy issues with 1,500 concrete panels that were installed at the five stations.

A whistleblower lawsuit unsealed this year alleged that the panels were made from substandard material by a company that falsified test results. The company — different from the one that made the ties — began manufacturing the panels in 2015, but the problem was not discovered by CRC officials until last year. One person has pleaded guilty in connection with the case.

Project officials have maintained that the panels do not pose a safety hazard, but CRC agreed to treat them with a sealant to prevent cracking. However, that work has not been completed.

Stark said the areas affected by the rail ties include places where trains cross over to move to other tracks or move off the main rail line. Couch said there are 12 of these special track sections.

The concrete ties, which are 12 to 14 feet long and weigh more than 1,000 pounds each, were not inspected before they were installed because such issues are unheard of on rail projects, Stark said. Couch, however, said that all concrete ties are inspected upon delivery to ensure they meet product specifications and are not damaged.

Brett Urquhart, a senior vice president with Rocla Concrete Tie, said the ties they provided have been designed and manufactured to the same specifications as others they have manufactured for the first phase of the Silver Line, which was built by a group led by Bechtel, an engineering, construction and project management company. He said the problems in these particular areas of track may stem from an overall design issue, which his company has been aware of and has been working with project officials to resolve.

The much-anticipated second phase of the Silver Line is expected to open for passenger service in 2020. It has six stations, including one at Dulles Airport, and for the first time will extend Metro service into Loudoun County.

The rail line’s first phase opened in 2014 and included five stations — four in Tysons and one in Reston. Although ridership on the line has not met expectations, Virginia officials maintain that it is an important catalyst for development in the Dulles Corridor.

Officials with the Federal Transit Administration said they are aware of the latest problems.

“MWAA has kept FTA informed of challenges such as those found with certain concrete panels and rail ties,” the agency said. “FTA continues to monitor MWAA’s quality control procedures as they work to mitigate these issues.”

The FTA is involved with the project because the U.S. Transportation Department contributed $900 million in funding to its first phase, in addition to nearly $2 billion in federal loans for the second phase.

The FTA receives monthly progress reports on Silver Line construction from its own consultants, and they are supposed to be made available to the public. It is not clear whether this problem was flagged in those reports, since the most recent report available on the website was from February.