(Host) The torrential rains that have soaked Vermont this summer have swollen rivers and washed out roads.
But there’s another effect that’s not so easy to see. Volunteers conducting water quality tests around Vermont are finding high levels of bacteria in several streams.
VPR’s John Dillon reports.
(Dillon) You might want to think twice about jumping into your favorite swimming hole.
Recent water quality tests of popular swimming spots in central and southern Vermont have found high concentrations of E. coli bacteria. The organism is an indicator of potential pathogens that can make people sick.
Ann Smith is program director of Friends of the Winooski, a non profit group that is testing the water quality in several tributaries of the river. She says the bacteria counts were low when river levels were down in June.
(Smith) In contrast, the July run… since we’ve we began to have this seemingly endless series of storms, so obviously much higher levels, and many of the results showed E. coli levels above the state standards. So it was a very striking difference.
(Dillon) The state uses a fairly conservative standard of 77 "colony forming units" of bacteria per milliliter. The Environmental Protection Agency limit is higher, at 235.
Bill Bress is a toxicologist with the state Department of Health. He says the state levels are designed to protect public health.
(Bress) A very large study came out last year out of Germany which looked at a couple of thousand of swimmers, actually monitored them throughout the summer, and actually found that 78 seemed to be the cut-off of no gastrointestinal effects. And once you went over 78, there was a steep increase. So I think we feel pretty comfortable in keeping the number that we have now.
(Dillon) Town health officers are supposed to test public swimming areas for E. coli. If bacteria levels exceed state standards, the area is closed.
But many popular swimming holes are on private land, where there’s very little water quality testing.
(Bress) As far of the rest of the state, areas that people swim, which aren’t monitored, the public’s really on their own.
(Dillon) In southern Vermont, the West River Watershed Alliance takes samples twice a month from swimming holes in the Saxtons, West and Williams rivers.
Rebecca Salem directs the volunteer effort. She says the bacteria levels go up after heavy rains. But several popular areas often exceed the state standard even without the high water.
(Salem) I’d say they run that way almost all the time, but go up over the EPA, or double that, so into the 500 range after a rain.
(Dillon) E. coli is found in human and animal waste. Sometimes the pollution is from overloaded sewage plants. But in rural areas pollution can come from farm fields, dirty streets, or leaky septic systems.
(Salem) The hardest thing about nutrient and bacteria pollution is that they are typically non point sources, which it means it’s coming from stormwater run-off as it travels over everybody’s backyard and everybody’s agricultural places and heads into the river.
(Dillon) The West River Watershed Alliance is working with the town of Londonderry to study where the bacteria may be coming from.
For VPR News, I’m John Dillon in Montpelier.