The city of Dartmouth intends to take legal action against the state Department of Environmental Protection, select board member Shawn McDonald announced Jan. 18.

The litigation comes in response to the department’s proposed changes to septic system regulations, something McDonald said several Dartmouth officials believe was done “illegally.”

“We are going to file a violation of the open assembly law with MassDEP with the [Massachusetts] Republic Attorney General’s Office,” he said.

The announcement came during MassDEP’s Jan. 18 briefing at UMass Dartmouth, a gathering where dozens of South Shore residents and officials voiced their opposition to the state’s proposed changes to their septic systems.

In an effort to decrease the amount of nitrogen entering the region’s waterways, the state is proposing that cities apply for “watershed permits” or that septic system owners upgrade their tanks to one that uses “the best technology available nitrogen.

Along with the litigation statement, McDonald asked DEP officials why South Coast communities were left out of the decision-making process, one of many frustrations officials and residents have expressed.

“We should have been there,” McDonald said. “That’s part of good open government.”

In response, Millie Garcia-Serrano, regional director for MassDEP’s Southeast Office, said the department has held 50 meetings with communities on the Cape, South Shore and South Coast since announcing the proposed regulations last summer.

Dartmouth Public Health Agent Chris Michaud also had several questions for the panel of state officials present. Questions included why they haven’t responded to any of their requests for records and why MassDEP has allegedly posted a job announcement regarding the regulations, which have yet to be passed.

“This is a done deal,” he said.

Micahud’s questions were not immediately answered by any of the MassDEP officials, resulting in members of the public yelling at state officials for answers.

Garcia-Serrano ultimately responded by saying that “MassDEP continues to work with all affected parties here.”

“I hope that tonight is the start of a very important conversation,” he said.

MassDEP will hold additional public hearings on January 24 and 25. Meetings will be held virtually. For more information visit www.mass.gov/regulations/310-CMR-15000-septic-systems-title-5.

The state also accepts written comments until 5:00 pm on January 30. Comments can be sent by email to [email protected] and must include “Title 5 and Watershed Permit” in the subject line.

All comments submitted must include the resident’s name and contact information.

This story will be updated.