One week after ordering new ridership projections for Maryland’s Purple Line, a federal judge has dismissed most of the original lawsuit that sought to block construction of the $5.6 billion project on environmental grounds.

U.S. District Judge Richard J. Leon ruled on May 30 that the Maryland Transit Administration (MTA) had complied with federal protections on endangered species and migratory birds in the area in its environmental review for the proposed 16-mile light line across Washington, D.C.’s northern suburbs.

The ruling allows Maryland or the Federal Transit Administration to appeal the lawsuit’s remaining issue—how the Purple Line ridership will be affected by ridership declines on the separately operated Metrorail system.

On May 22, Leon ruled that Maryland and federal transit officials “failed to take the requisite ‘hard look’” at recent downward trends in Metro’s ridership, which previous studies estimate will account for approximately 27% of Purple Line riders via system transfers at five planned co-located stations.

Purple Line Transit Partners, a development consortium includes Fluor as equity member and leader of the design-build joint venture, was days away from starting construction on the public-private partnership in August 2016 when Leon revoked the Purple Line’s environmental approvals.

The ruling also froze $900 million in federal New Starts funding, which MTA will rely on for the project’s estimated $2 billion construction cost. Those funds remain part of the Federal Transit Administrations proposed FY 2018 budget, although the time necessary to comply with new court-ordered ridership studies has not been determined.

Maryland officials have claimed that delaying construction start-up 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. It is uncertain whether Maryland will continue funding the project if the ridership reassessment is appealed. According to court filings, cancelling the project could cost the state more than $800 million.

Purple Line Transit Partners has not commented on its status with the Purple Line since the May 22 ruling. In early May, the firm’s CEO reaffirmed the consortium’s near-term commitment to the project.