Madison Mayor Dave Cieslewicz has ordered an investigation into why drinking water untreated for contaminants such as bacteria flowed from a city well for 38 days without being discovered by the Madison Water Utility.

No illnesses have been linked to the water that was pumped from Well No. 29 on the city's Far East Side from Aug. 29 to Oct. 5, according to officials.

Despite utility workers making daily checks on the well during that period, the failure of a system that pumps chlorine and fluoride into the drinking water remained undetected, said David Denig- Chakroff, the utility's general manager.

"It shouldn't have happened," said mayoral spokesman George Twigg. "The mayor is adamant that we get to the bottom of this and that it not happen again."

The incident is the latest in a long string of problems that have plagued the Madison Water Utility for the past two years. A Wisconsin State Journal investigation, published in May, showed the utility had been less than forthcoming about everything from water quality to security.

After the newspaper series, Cieslewicz issued a 10-point plan to improve trust in the utility. The plan included performance standards for Denig- Chakroff, the first such standards put in place for a city manager.

Cieslewicz has appointed a three-person panel to review the breakdown. Conducting the inquiry will be Denig-Chakroff; the utility's newly hired water quality manager, Joseph Grande; and city engineer Larry Nelson. Twigg said Nelson was asked to help with the review because he is not with the utility and will serve as "a pair of outside eyes."

As required by law, the utility conducts daily testing for bacteria at several locations throughout the city.

Tom Stunkard, who oversees regulation of the water utility for the state Department of Natural Resources, said a review of those test results from the period in question revealed no detection of microbial contamination.

And Dr. Thomas Schlenker, director of public health for Madison and Dane County, said he reviewed health records for the past month and found no increase in gastrointestinal illnesses that could be attributed to non-chlorinated water.

Schlenker also said drinking water samples taken in the area during the period showed adequate chlorine levels - probably because of treated water flowing into the area from Well Nos. 15 and 11, which also serve the area.

As a result, Schlenker added, "the health risks associated with this incident would appear to be very minimal.

"Individuals who may have briefly consumed unchlorinated water would not likely have experienced any ill effects," Schlenker concluded.

Denig-Chakroff said the well, which is also one of the city wells plagued by high manganese levels, was only being used intermittently between Aug. 29 and Oct. 5.

Water from the well was being pumped into the system twice a week, in the middle of the night, for about eight hours total per week, he said. He estimated about 340,000 gallons of untreated water from the well were pumped into the system each night the well was in use.

Still, Denig-Chakroff said, the failure of workers to detect the lack of chlorination should not have happened.

"For reasons we're not aware of, this didn't get red-flagged or picked up," Denig-Chakroff said. "We're not sure why this breakdown happened. That worries us. That's the bigger concern here."

Denig-Chakroff said the problem was likely due to a meter that failed. The equipment that adds chlorine and fluoride to the water is dependent on a signal from the meter and with the meter broken, the signal never came.

Stunkard said the utility didn't violate any regulations as a result of the slip-up. No laws require that chlorine or fluoride be added to public drinking water, he said.

Still, Stunkard said, the breakdown in oversight is troubling.

"Their bigger issue is to look at why their people didn't catch this," Stunkard said.