An art installation that would see nearly ten kilometres’ of silvery fabric suspended over the Arkansas River is on hold.

The project is the brainchild of artist Christo and his late wife, Jeanne-Claude. Over the River received approval by US authorities, but it’s being appealed by an environmental group named Rags Over the Arkansas River. It claims the project poses environmental, safety, traffic and economic risks and will require more than two years of industrial-scale construction work. Christo’s team has said it plans dozens of measures to mitigate impacts.

While they await the outcome of the appeal, they’re working on other aspects of the project.

During the work on Over the River, he also is actively working on The Mastaba, a giant sculpture of 410,000 barrels planned for Abu Dhabi that he conceived in 1977. Because he is 77, Christo said he is trying to complete both projects simultaneously rather than focusing on one at a time.

The earliest Over the River could happen would be the summer of 2016.