Oct. 4—WATERTOWN — City Manager Kenneth A. Mix will resign from his post Dec. 31.

He notified the City Council on Monday in a one-paragraph letter.

"I am unwilling to continue as city manager beyond the expiration of my current contract," he wrote.

Mayor Jeffrey M. Smith announced Mr. Mix's resignation following an executive session during Monday night's City Council meeting. The session lasted about 2 hours, though other city business was also discussed during that time.

Mr. Mix said he has no regrets returning to work for the city and thanked city staff for their work.

Mr. Mix was appointed interim manager in January 2020 after Richard M. Finn resigned amid mostly unfounded claims that he created a hostile work environment. Mr. Mix had no intentions of continuing in the role on a permanent basis. Then the COVID-19 pandemic began and he led the city through the financial crunch.

The City Council unanimously approved permanently hiring Mr. Mix in November 2020 after a monthslong search process involving 29 applicants.

His two-year contract is up Jan. 1.

"It was a strange time to work because of COVID," and having so many projects in the works with federal pandemic relief, he said Monday night. He wants to "complete as much as possible" over the next three months and is confident progress on American Rescue Plan-funded projects will continue after that.

Mayor Smith and city attorney Robert J. Slye both said Councilman Cliff G. Olney's behavior prompted Mr. Mix's resignation. Mr. Slye said the councilman has been "micromanaging" Mr. Mix. Mr. Olney was elected to council last November.

Mr. Slye said he thinks Mr. Olney believes in his approach, but is instead a disruptive force. He added that there has been "no one more disruptive" than Mr. Olney in his 30 years as city attorney.

He added that Mr. Olney has caused morale problems among city staff by making disparaging remarks, including to people in the codes office, engineering department, the district attorney and city court judge.

Mr. Olney said Mr. Mix has not been in his "crosshairs."

"That was not the case," Mr. Olney said. He left council chambers before he could be reached for further comment.

Mayor Smith said he has been talking with Mr. Mix — last week nearly every day — trying to convince him to stay. He thanked Mr. Mix for stepping into the role in 2020 and for caring so much about the community.

Mr. Slye said Mr. Mix is in "the top in the class" of all the city managers he's worked with.

Councilwoman Lisa A. Ruggiero during open session implored him to stay, but Mr. Mix said his mind was "pretty much set." He declined to comment about Mr. Olney and didn't go into detail about why he is leaving.

"What's done is done," he said.

Editor's note: Due to a reporter's error, an earlier version of this story contained an inaccurate word in a quote from City Attorney Robert J. Slye regarding Councilman Cliff G. Olney. The correct word was "disruptive."