The contractor building Maryland’s Purple Line said it anticipates needing an additional five months and $187.7 million to build a required “crash wall” along the light-rail tracks.

Such a request would increase the project’s potential delays to 506 days, or nearly 17 months, when added to other problems the contractor has cited. It also would bring the potential cost overruns on the $2 billion construction contract to $526 million — more than 25 percent over budget.

The contractor, a consortium of companies called Purple Line Transit Partners (PLTP), said in an April 7 letter to the Maryland Transit Administration that CSX Transportation is requiring that a different kind of crash wall be built along the Purple Line tracks from the one the contract anticipated. The light-rail tracks will run adjacent to CSX tracks between the community of Lyttonsville and the Silver Spring Transit Center.

Crash walls are designed to absorb the forces of a derailed train to protect nearby facilities and structures, such as piers that hold up bridges carrying traffic over the tracks.

PLTP also told the state in a March 11 letter that it might need to file a “force majeure” claim because of the novel coronavirus outbreak. The companies did not provide any details, but such claims typically argue that a contract can’t be followed because of an “act of God.”

Construction on the 16-mile line has continued amid the coronavirus pandemic. However, this month, some workers were asked to self-quarantine for 14 days after a Washington Gas inspector on the project tested positive for the novel coronavirus.

PLTP spokesman John Undeland said the contractor has been working with CSX for more than a year on the crash wall design. He said CSX had only recently issued crash wall design requirements.

“We’ve presented a number of workable solutions,” Undeland wrote in an email, “but none have been approved by CSX.”

MTA spokeswoman Veronica Battisti declined to respond to emailed questions. In a written statement, she said the state “has been actively engaged in discussions” to mitigate impacts on the Purple Line’s schedule and cost. She said she could not comment further until the state and contractor had reached a settlement.

It is unclear how delays might affect the Purple Line’s opening date, because project officials have been able to accelerate some work in the past. The opening of the rail line between Montgomery and Prince George’s counties was initially scheduled for March 2022. The most recent schedule made public has it opening in two phases — in late 2022 between College Park and New Carrollton and by late June 2023 for the rest of the line extending west to Bethesda.

CSX declined to make anyone available for an interview. However, in response to emailed questions, the company’s media office said CSX “has been working closely” with the state on the Purple Line since 2003.

“The requirement for crash walls or other barriers have always been part of the project to ensure the safety of both systems,” the statement said.

The MTA and the contractor have been in negotiations for several years over what delays are necessary and who is responsible for the related costs, such as for additional labor and longer rentals of large equipment.

The first major delays stemmed from an unsuccessful lawsuit against the project, which stalled the start of construction. The state’s trouble in acquiring rights of way also added time and cost, the contractor said. The lawsuit added 266 days and about $200 million, while the right-of-way delays added 79 days and $138.2 million, the contractor has said in financial filings.

The state granted the contractor a 160-day delay for the lawsuit claim but no additional money. It rejected the contractor’s entire claim for any delays related to rights of way.

Delays and cost overruns, as well as disputes over who will pay for them, are not unusual in large construction projects. However, the ongoing Purple Line dispute has drawn attention because the project is being financed and built — and ultimately will be operated — as part of a 36-year, $5.6 billion public-private partnership. The arrangement is one of the broadest of its kind among U.S. transit projects.