Four residents of a tiny Alabama town are fighting back against a giant landfill operator after the Georgia-based company, Green Group, filed a $30 million defamation suit against them. The American Civil Liberties Union asked a federal court to dismiss the suit on Thursday.

Green Group operates a toxic coal ash dump in Uniontown, Ala., a small, mostly black community where half the residents live below the poverty line. The Arrowhead landfill draws coal ash — the sludge left by burning coal — from across the country. Opposition to the landfill gained strength after waste from the largest coal ash spill in U.S. history was dumped in Uniontown. In total, Arrowhead takes up to 15,000 tons of toxic waste from 33 other states every day.

Three years ago, members of a group called Black Belt Citizens Fighting for Health and Justice and other residents filed a civil rights complaint with the EPA against the Alabama Department of Environmental Protection (ADEM), the state agency that oversees the landfill. The complaint against ADEM says that dust from the dump gets into homes and on cars and causes serious health problems. Three years later, the agency is still investigating.