(Host) Untreated sewage continues to pour into public waters around the state - especially into the Lake Champlain basin.

The reason is that treatment systems are sometimes weakened by age or overwhelmed by heavy rains.

VPR's John Dillon reports:

(Dillon) If you want to find out which sewage treatment plants aren't working properly, you have to search the Vermont Department of Environmental Conservation web site.

The state has posted the information publicly for two years now. From the end of May through last week, 11 overflows were reported. All but one dumped into rivers or streams that flow into Lake Champlain.

Christine Thompson directs the wastewater management division for the state. She said sewage plants overflowed 52 times last year, and 20 so far this year.

(Thompson) ``It really is dependent, a lot of these overflows, on the precipitation and the weather, because a lot of the overflows are caused by high inflow or infiltration of precipitation into the collection system such that the pipes can't handle the amount of water.''

(Dillon) Towns around the state treat their sewage. But most don't separate the stormwater system from the sanitary sewage system.

So heavy rain - like the deluge from last weekend - can simply overwhelm the treatment plants. The sewage flows downstream, and contributes to the phosphorus pollution that has damaged Lake Champlain.

(Rapacz) ``I think we should stop blaming rainfall for a contaminated lake.''

(Dillon) Mike Rapacz is a staff scientist for the Vermont office of the Conservation Law Foundation.

He says the overflows contain a mixture of pollutants, including sewage, bacteria and the dirty stuff from city streets.

(Rapacz) ``The fact that rainfall has such a strong influence on water quality on treatment plants has nothing to do with rainfall, it has to do with poor infrastructure.''

(Dillon) Rapacz would like to see towns invest in separating storm water and sewage systems.

In many cases, that would require increases in water rates, or bond votes to pay for the projects.

While the state keeps track of the spills, officials often don't know how much raw sewage is released.

Thompson of the wastewater management division says the amount of pollution often can't be measured.

(Thompson) "The overflows are occurring due to precipitation events, and they're occurring at manholes, and there's just no way of getting even a fairly accurate volume amount of what's being overflowed.''

(Dillon) How much pollution comes from sewage treatment plants has been a hot issue lately. The Environmental Protection Agency has told the Douglas administration it may need to do more to control phosphorus pollution from sewage plants in the Champlain basin.

But the administration says just 10 percent of the phosphorus comes from point sources like sewage treatment plants. The state instead has focused its effort on non-point pollution, such as runoff from farms.

But Rapacz of the Conservation Law Foundation, says the 10 percent figure doesn't include the overflows - including the ones this month in Lake Champlain tributaries.

(Rapacz) ``If you look at the information that's posted online, you'll find in most cases that they have absolutely no idea what the volume was.''

(Dillon) The state recently ordered one chronic polluter to clean up its act.

The town of Proctor is under orders to fix its system by September of this year.

For VPR News, I'm John Dillon in Montpelier.