The Madison Water Utility called for a temporary shutdown of
a water source near the University of Wisconsin campus after routine testing
recorded unsatisfactory results Tuesday.

The bacteria discovered in Well No. 15, known as total
coliform, is bacteria commonly used as an indicator of other bacteria in food
and water.

“They are not necessarily harmful but when you find
coliform there is also a chance that you could find harmful bacteria,”
said Joe DeMorett, water supply manager of Madison Water Utility.

When total coliform is found, the Department of Natural
Resources runs additional tests in search for E. coli and fecal coliform.
Health risks develop in Madison’s drinking water only if tests come back
positive for these two bacterias, DeMorett said.

The Water Utility was relieved to find tests for E. coli and
fecal coliform came back negative, DeMorrett also said.

According to Tom Stunkard, public water supply engineer with
the Department of Natural Resources, the absence of these bacteria “tells
us that something is going on with the well or [DNR’s] sampling methods, [but]
there are no health risks from total coliform alone.”

Stunkard said Madison takes bacteria samples every day to
ensure the public water supply is safe.

The tested sample from Well 15 that came out positive for
coliform came out of the deep well, which draws water out of the ground,
DeMorett said.

“This water is untreated, but from there, chlorine and
fluoride are added before it goes into the distribution system,” DeMorett
said.

DeMorett added that when the treated water was tested, no
sign of total coliform was found, indicating the chlorine added daily was
enough to disinfect the contaminated groundwater before it made its way to the
tap.

“There was never any danger of untreated water going
into the distribution system and to the public,” he said.

Efforts will now be focused on locating the source of the
total coliform, said UW adjunct professor of population health, Henry Anderson.

The coliform content could have arisen from heavy rains
submerging the wellhead or a potential leakage in the pipe system, Anderson
said.

According to Anderson, the next step is “to find the
source and make sure the pipes aren’t leaking somewhere when they are
underground with sewage pipes as well so there isn’t any
cross-contamination.”

Most cases of E. coli water contamination occur
underground, DeMorett said, so the city will prioritize pipe checkups.

After indicating where the total coliform is coming from,
the city will treat the area with chlorine and eliminate the bacteria.

The whole process takes 24 hours to get sample results back.

The scientists take their time because they want to make
sure it’s done right the first time, DeMorett said.

“The well should be up and running probably somewhere
between five to seven days,” he added.