A major environmental group on Monday petitioned the federal government to implement an endangered species recovery plan that could have major ramifications for the Purple Line light rail.

The Center for Biological Diversity filed a legal petition asking the U.S. Fish and Wildlife Service to develop a recovery plan for the Hay’s spring amphipod, a tiny shrimp-like critter just 5-10 millimeters in length that is colorless, blind and lives most of its life underground.

The organization joined the Friends of the Capital Crescent Trail and other Chevy Chase residents last month in threatening to sue federal government agencies that the group said didn’t adequately take into account how the Purple Line would harm and possibly destroy amphipod populations in Rock Creek.

Brett Hartl, endangered species policy director for the Center, wrote that the U.S. Fish and Wildlife Service exempted the amphipod from recovery efforts when it was named to the endangered list in 1982 because it was thought to exist in just one spring.

“…the Service exempted the species from recovery planning because it felt that the conservation options for the species were simply too limited for anything proactive to be done to help,” wrote Hartl.

But the amphipod has been found in four more springs in Rock Creek in the District. And according to an American University biology professor hired by the Friends of the Capital Crescent Trail, it’s likely to exist in three springs in a Montgomery County section of Rock Creek that would be threatened by construction of the Purple Line.

The professor, Dr. David Culver, is expected to resume his search for the critters in the fall, when they are more likely to come out from underground.

Hartl urged the U.S. Fish and Wildlife Service to initiate a recovery plan, which would involve maintaining a buffer area around each of the springs and seeps and could mean prohibiting any type of construction or increase in impervious surfaces — including a new trail.

The petition also asks the Service to take its own samples at the three Maryland sites where the Center for Biological Diversity believes the amphipod species lives.

Last week, the Friends of the Capital Crescent Trail and many of the same residents of Chevy Chase filed a similar notice of intent to file suit against the state of Maryland, where an additional amphipod species thought to live in the area is already identified as endangered under state law.

Photo via Brett Hartl/Center for Biological Diversity