A South Carolina legal service has joined the fight against an atomic weapons components factory at the Savannah River Site, raising the possibility that environmental groups will sue the federal government to stop the effort.

The South Carolina Environmental Law Project, a non-profit service with an extensive court record, outlined concerns about the factory in a letter this week to the U.S. Department of Energy. The letter called the proposed factory risky and in need of further study.

At issue is a proposal to build a nuclear weapons pit plant that would use plutonium, a deadly long-lived radioactive material, at the Savannah River Site.

The pit factory would produce potentially thousands of jobs, but is drawing opposition from environmental groups in South Carolina, New Mexico and California.

Savannah River Site Watch, Nuclear Watch New Mexico and Tri-Valley CARES recently retained the Environmental Law Project. They say pit factories are expensive, unnecessary, needlessly threaten the environment, and could leave unused plutonium stranded in South Carolina and New Mexico.

President Joe Biden’s administration needs to be “aware of the serious environmental and human health risks associated with a significant expansion in pit production,’’ according to a letter written Wednesday by law project attorney Leslie Lenhardt to the energy department.

Nearly a dozen key members of Congress were copied on the letter, including Republican senators Lindsey Graham and Tim Scott of South Carolina and Sen. Ben Ray Lujan, D-New Mexico.

Plans call for producing 50 pits a year at SRS on the site of a failed mixed oxide fuel plant near Aiken not far from the Georgia border. Another 30 pits would be produced each year at the U.S. Department of Energy’s Los Alamos, N.M., site.

The government says the factories would provide fresh pits to replace the aging ones now used in nuclear weapons, while also providing the stockpile to produce a new type of atomic weapon. Boosters say pit factories are vital to the nation’s defense, although not everyone agrees.

Opponents are asking the government to conduct an extensive study, called a programmatic environmental impact statement, before moving ahead with the effort. Such a study would be more comprehensive than past studies, likely delaying the pit production effort. They are concerned that more than 7 tons of plutonium could be brought to SRS after the state negotiated a deal to rid the site of stranded plutonium.

No decision has been made on whether to file suit because opponents of the pit factories hope the Biden administration will reverse course and scrap the long-discussed proposal. Plans to build the SRS pit factory, on the table since the 1990s, resurfaced while President Donald Trump was in office.

“We would like to avoid a lawsuit, so now the door is open to negotiation with DOE,’’ said Tom Clements, who heads Savannah River Site Watch. “I hope they will step through that door and talk to us.”

If not, filing a lawsuit “remains on the table,’’ Clements said.

Lenhardt’s letter said the groups are “hopeful that you will seek to review the former administration’s failure’ to conduct’’ the comprehensive environmental impact statement.

The S.C. Environmental Law Project has taken on some of the highest profile environmental cases in the state since Pawleys Island attorney Jimmy Chandler founded the service in 1987.

Through the years, the law project has handled a variety of cases, including numerous lawsuits to protect coastal wetlands and beaches from over development. But it also has been involved in suits against Barnwell County’s nuclear waste dump, a disposal site at the Savannah River Site, garbage landfills across South Carolina and a hazardous waste incinerator in York County.

One of its most high profile cases was a successful effort to close a hazardous waste landfill on Lake Marion.

Until the Southern Environmental Law Center opened an office in Charleston, the Environmental Law Project was the only non-profit legal service of its kind in South Carolina.