DAYTON, Ohio (AP) — The city of Dayton has sued the Wright-Patterson Air Force Base and the U.S. Department of Defense for failing to stop water contaminants from entering a source of the city’s drinking water.

The Dayton Daily News reports the city filed suit on Monday. In March, the city gave notice that it intended to sue unless the air base agreed to cooperate on mitigation measures for the chemicals known as PFAS.

The city has said its drinking water is safe but that if contaminants on the air base go untreated or mitigated, they could enter the city’s Mad River Wellfield. A spokesperson for the air force base declined to comment.

The air force base is located on the eastern outskirts of the city. 

Last year, Gov. Mike DeWine penned a letter to the Department of Defense raising concerns that there may be an issue of contamination of Dayton’s water source. 

In the letter DeWine states, "Since at least 1970, WPAFB used PFAS-containing firefighting foams during fires and in firefighting exercises and runoff from these activities has migrated into surrounding soils and drained into nearby ditches and stormwater culverts. Wright Patterson Air Force Base has ceased the use of these older generation PFAS-containing fire fighting foams.”

Following DeWine's letter, the Department of Defense released a statement.

"Across DOD, we only use AFFF (aqueous film forming foam) in emergency situations. We don’t use it anymore in a training environment. We are looking for alternatives that don’t contain PFAS. We are now in Congressional mandates to eliminate most use of AFFF by 2024. We are working to find an alternative to AFFF that meets military specifications," the statement read.