About 11 percent of county residents rely on wells for water. The wells tend to be clustered in the upper, less dense half of the county.
It was not clear how many wells might be endangered, or in what areas, said Kyle Schmeck, division director for water-quality management. He said an unpleasant odor and lack of clarity were clues that the water was not safe.
"Take a look, take a sniff," Schmeck said. "If floodwaters topped over the wellhead or casing, the potential for contamination is there."
Septic systems can be compromised by floodwaters, allowing sewage to seep into waterways. Or too much storm runoff can pressure sewage-treatment plants to release raw material into waterways, Schmeck said.
Hurricane Irene was unusual in that it caused the small tributaries of local creeks and waterways to flood, potentially spreading contamination to wells never before affected, he said.
There were no reports of illness due to unclean well water, Schmeck said.
"We don't anticipate any, but sometimes it happens," he said. A symptom of illness would be gastrointestinal distress.
Schmeck said owners could disinfect their wells by pouring in a solution containing at least 5.25 percent chlorine.
"Turn on the spigots and pull it through all the piping. Do it in the evening, and in the morning it should be disinfected. Turn on the spigots until the chlorine smell is gone. You should be good to go."
Anyone who wants a free test kit for well water can call the county Health Department at 610-278-5117.
Contact staff writer Bonnie L. Cook at 610-313-8232 or bcook@phillynews.com. Read her blog, "MontCo Memo," at www.philly.com/montcomemo
