Iowa City police Sgt. Sid Jackson submitted a letter of resignation Monday, almost three weeks after being charged with OWI.

Jackson has been on administrative leave since the Feb. 21 incident while the department conducted an internal-affairs investigation, Iowa City Police Chief Sam Hargadine said.

The investigation had concluded, Hargadine said, and officials were meeting with Jackson when the 26-year veteran of the department resigned.

Officials said no further information was available, citing confidentiality in personnel matters.

According to authorities, an Iowa City police officer discovered Jackson on the morning of Feb. 21 and called UI police when he realized Jackson appeared to be intoxicated.

He was sitting in a vehicle with the door open, UI police said. He smelled strongly of alcohol and had bloodshot eyes, officers said.

Police reports show Jackson admitted he had been drinking but denied driving, though there were tire tracks in the fresh snow.

Authorities said Jackson walked away from the officer and refused to cooperate with testing, later refusing a breath test. Jackson was injured during the incident, police said, though no details about his injuries were available.

Jackson was not on duty at the time and was in his personal vehicle, Hargadine said.

Though the internal investigation is over, that inquiry was separate from the criminal charges.

At least four officers have resigned from the Iowa City police force in the last year for a variety of reasons, Iowa City police Sgt. Troy Kelsay said.

“It’s not unusual for there to be turnover,” he said.

None of the other four officers had unresolved criminal charges against them, Kelsay said.

“This particular set of circumstances is a bit different,” he said.

And while no specific numbers were available, Hargadine said, internal investigations are not uncommon, and the department conducts reviews often. Every weapons discharge, rudeness complaint, and each grievance to the Police Citizens Review Board is followed by an investigation.

The department has an approved staffing level of 75 sworn officers, so they must now seek approval to replace Jackson. With the current economy and budget cuts, this will have to be discussed at the city level, Kelsay said.

Jackson had been with Iowa City police since 1982, and he received his first promotion in 1996. He was a lieutenant in the investigations unit, though he was later demoted to sergeant. Hargadine declined to comment on the reason.

Until his resignation, Jackson was one of two officers assigned to late-night patrol.