The Penobscot Nation and Conservation Law Foundation have filed an appeal in Superior Court to stop the expansion of the Juniper Ridge Landfill in Old Town.
In October the state concluded that the expansion was in the public's interest and set several conditions that Casella Waste Management must meet to move forward with the project.
Alexandra St. Pierre of the Conservation Law Foundation said the expansion runs contrary to the state's waste management goals, which prioritize reduction of waste volume and using landfills.
"Our goal here is to ensure that the decision is consistent with environmental justice and with the solid waste hierarchy as the law requires," St. Pierre said.
The Penobscot Nation and CLF said that in its finding, the state failed to guarantee the safety of residents and the environment.
They argue that harmful exposure to PFAS in the landfill's leachate, air pollution and contamination of the Penobscot River will all increase.
"And we're really hoping we'll get adequate consideration for the issues that we raised and that the people actually themselves are considered and that environmental justice is implemented," St. Pierre said.
The DEP said it is unable to comment on pending litigation.