A year of high turnover at City Hall continued with two high-profile announcements Tuesday.

James Horan, New Haven’s chief administrative officer, said he will leave his high-ranking post on Friday for a new job in Hartford. Meanwhile, Julio Gonzalez ’99, a former Ward 1 alderman who is managing Mayor John DeStefano Jr.’s reelection campaign, said last night he will become the mayor’s executive assistant if DeStefano is reelected.

The chief administrative officer oversees the operation of all city services agencies.

City spokesman Jim Foye said Horan’s decision was somewhat unexpected.

“For me, it was a surprise,” Foye said. “Jim’s been with the city five years — It’s going to be tough to replace him. But he’s moving on to something he wants to do.”

DeStefano was unavailable for comment Tuesday.

Horan, who has worked for the city of New Haven since 1997, said he is leaving to become executive director of the Connecticut Association of Human Services, a nonprofit advocacy and education organization that focuses on poverty, hunger and health care issues.

“It’s a good time to move on for a good position that I’m very interested in pursuing,” he said. “It was a great experience. I think we made much progress improving services and the general quality of life in New Haven.”

Horan has a wife and two children, ages 2 and 3 months.

Before he assumed his current post in March 2000, Horan served as legislative assistant to the mayor and then as executive assistant to the mayor.

If DeStefano wins the mayoral election, Gonzalez said he will “in all likelihood” take a position in his administration, specifically the executive assistant post Horan once held.

The mayor’s executive assistant is his chief of staff and acts as his liaison to city agencies.

“That’s something that we’ve discussed, if the mayor is reelected,” Gonzalez said.

Gonzalez entered New Haven politics in 1997 after he won the Ward 1 aldermanic seat, which is traditionally held by a Yale student or recent graduate.

Tuesday’s announcements followed a year of high personnel turnover at City Hall. Posts in several city departments, including the Office of Public Information, remain unfilled.

Former public information director Andrea Comer stepped down earlier this year.

The Board of Aldermen, New Haven’s 30-member legislative body, has also had its own turnover problems of late.

In the past 12 months, Gonzalez left his post to work for DeStefano, and five other aldermen resigned outright in wards 2, 7, 9, 18 and 23.