MADISON, Wis. -- Madison's Water Utility has come under fire again as officials confirmed that a city well pumped out untreated water for more than a month.

Water and city health officials said the health risks from the latest water quality problem appear to be "very minimal."

But one alderman said that the problem raises safety and management concerns and shows a need for more scrutiny on how the Water Utility is run.

The issue involved Well 29, which was shutdown due to high manganese levels and then put on standby for only limited use. The problem arose from a lack of any chemical treatment to the well during its limited use, WISC-TV reported.

For more than a month, starting Aug. 29, thousands of far East Side households were served twice a week by the Thompson Drive area well that did not receive the normal treatments of fluoride and chlorine.

The city voluntarily adds those chemicals to prevent tooth decay and to kill bacteria and viruses.

That didn't happen because a faulty meter failed to trigger the chemical treatment -- and no one at the utility noticed until late last week.

"It wasn't a serious issue because we were running this well on standby, which means that we were running it only for a very brief period of time only twice a week," said David Denig-Chakroff, manager at the Madison Water Utility.

But now the mayor wants to know why the problem went undetected for so long by three levels of staff.

"And we're going over those records to find out how it was missed that no chlorine was going into the system during this period," Denig-Chakroff said.

Denig-Chakroff said the city health director agreed that there was a risk from the lack of chemicals.

"Certainly we want them in there, but if there not in there for a brief time it's not a huge concern," Denig-Chakroff said.

Denig-Chakroff said the well was only running twice a week at night and that tests at the time showed no bacteria and normal chlorine levels.

But those tests were taken during the day, when other wells were feeding the system. And since no one checks for unregulated human viruses, found by scientists in the past in two city wells, that risk can't be completely ruled out, WISC-TV reported.

Alderman Zach Brandon called the situation serious.

"It might have been a very few people, but people were drinking water that didn't have treatment and that's a real problem," Brandon said. "The question we have to ask ourselves is how many more times are we going to be told, 'Well it happened but nobody got sick?'"

In an internal staff e-mail sent by principal engineer Al Larson, the Water Utility's second in command, Larson said the incident "is totally unacceptable."

"It should have been caught by (staff) on duty, not to mention by myself from the daily report," Larson said, according to a copy of the e-mail obtained by WISC-TV.

The treatment problem comes about three months after Denig-Chakroff's contract at the Water Utility was renewed for $113,000.