The latest is in St. Paul Park, which recently shut down two of its three wells because the pollution in the water doubled.
The levels of pollution have danced above and below safety limits in Oakdale, Woodbury, Lake Elmo and Cottage Grove — making it a harrowing and expensive problem to solve.
The perfluorochemicals, or PFCs, were dumped into landfills in the 1970s and discovered in drinking water in 2004.
When a water well is turned on, for example, it sucks up water and pollution-bearing water flows in to replace it.
“We saw a little pulse of chemicals moving away,” said Yingling.
When pollution is detected, state officials never order that polluted wells be closed.
Two of the city’s four wells were shut down, and the city spent “tens of millions” piping clean water to well-closure areas, according to city administrator Kristina Handt.
The city shut wells down, dug a new one and installed filters on the water system.
St. Paul Park is not sitting on an underground lake of pollution, but is getting whacked by the flailing tail of a pollution plume.
“It is getting a little contamination from Oakdale, and possibly Lake Elmo, flowing intermittently to the Mississippi River,” said Yingling.