The fate of the planned 16-mile Purple Line light-rail project across Washington, DC’s Maryland suburbs has been clouded by a federal court’s call for an updated environmental study—adding another delay to a project already on the brink of losing nearly $1 billion in federal funds.

U.S. District Judge Richard J. Leon ruled on May 22 that Maryland and federal transit officials “failed to take the requisite ‘hard look’” at how Purple Line ridership might be affected by the recent spate of infrastructure and safety issues on the region’s separately operated Metrorail system.

Previous studies projected that approximately 27% of Purple Line riders would transfer to or from Metro at five planned co-located stations.

The judge also discounted a December 2016 Federal Transit Administration conclusion that no additional environmental studies were necessary, citing the report’s heavy reliance on pre-existing data.

According to the Washington Metropolitan Area Transportation Authority, Metro ridership fell by 12% during the second half of 2016, continuing a trend that has seen the system’s number of daily trips drop by 100,000 over the past six years.

Leon ordered the “expeditious” completion of a supplemental environmental impact study to more accurately weigh the merits of a lawsuit brought by opponents on environmental grounds.

The plaintiffs also challenged methods used to justify the $5.6-billion project, which is to be designed, built and operated as a public-private partnership.

Questions about the validity of those figures in light of Metro’s ongoing reliability and ridership issues led Leon to revoke the Purple Line’s environmental approvals in August 2016, putting $900 million in federal New Starts funding on hold as well.

Maryland officials have claimed that the delay has added as much as $13 million a month to the Purple Line’s cost, and that existing funds for planning and design work would likely be exhausted as of June 1.

Cancellation of the project could cost the state more than $800 million, according to recent court filings.

Maryland government officials did not respond to requests for comment by ENR presstime.