Over the course of 18 days, longtime Planning Board and Conservation Commission member Sherman Briggs has lost his seat on both panels following his admission to a state ethics violation.

On Tuesday, Briggs resigned from the Conservation Commission in a letter sent to the Board of Selectmen.

Chair Jody Dickerson received the letter on the same day the board had scheduled a public hearing to discuss the ethics violation. Briggs was not present at the hearing.

The State Ethics Commission found Briggs violated a conflict of interest law when Tabor Academy hired him for excavation work after he voted to authorize construction at the school.

Briggs approved the work as a Conservation Commission member, a position he held by appointment.

Tabor paid Briggs $8,030 after he installed two saltwater tanks with his company, Briggs Excavating.

The conflict of interest law prohibits municipal employees from participating in activities where they have a financial interest. According to the ethics commission, the violation occurred two years ago.

Last month, Briggs stayed in the race for Planning Board after news of the violation went public; however, voters chose to not re-elect Briggs to a seat he had held for many years.

Dickerson asked Marion Town Administrator Paul Dawson to draft a letter expressing the board’s gratitude for Briggs’ service.

“Sherman Briggs served this town well over the years. I want to thank him personally for his service and dedication to the town,” Dickerson said.

A previous public hearing had been set for May 20, but was re-scheduled to Tuesday, June 4, at Briggs’ request.

At a previous meeting, Dawson noted that removing Briggs from the commission was a possibility. Calls made to Briggs seeking comment have not been returned. The ethics commission released news of the violation on May 2.