Officials at the Metropolitan Washington Airports Authority said Monday that they will have to redesign portions of the second phase of the Silver Line rail project to accommodate new state and federal regulations regarding stormwater management — a change that could add to the project’s $5.6 billion price tag.

However, officials could not say whether the new design would delay the project’s projected 2018 opening.

“We’re reviewing the impact of the design changes on costs and schedule,” said spokeswoman Marcia McAllister.

The design changes would impact the entire 11.4-mile line, which stretches from Wiehle Avenue in Reston to Route 772 in Loudoun County and has six new stations, including one at Dulles International Airport. The Silver Line’s first phase opened July 26.

A new executive director recently came on board to manage the rail project’s second phase. Charles Stark is a longtime transportation veteran who most recently served as vice president and project executive with AECOM.

The authority has dipped into contingency funds to deal with stormwater management issues tied to the construction of Phase 2. Only a few months after preliminary construction began, managers tapped the $551.5 million contingency fund for $700,000 to cover a change in storm-water treatment required by the state. But two sources close to the project said the additional changes are likely to cost even more.