(Host) The zone of groundwater now contaminated at the Vermont Yankee nuclear plant is about the size of a football field.

And the state Health Department has increased the testing of private wells in the area around the plant.

VPR's John Dillon has more.

(Dillon) The Department of Health stepped up its monitoring work in early January after Yankee discovered radioactive tritium in a well about 30 feet from the Connecticut River.

The department now says a half-dozen wells are showing tritium. Some have registered high levels - close to what's found in water that's used in the nuclear reactor.

The Health Department says that a corridor of contaminated water is flowing from the turbine building toward the Connecticut River.

Bill Irwin is the state's radiological health chief.

(Irwin) "Once additional wells and some additional excavation comes in it may be able to possible to narrow it down. But generally, it is an area that is fairly large because of the number of underground pipes that are not only now potentially leaking but could potentially leak over the course of time."

(Dillon) Irwin says Yankee's environmental consultant should have a report later this week with a preliminary estimate of the volume of contaminated ground water.

Irwin says there may be more than one underground pipe system leaking radioactive water.

(Irwin) "There's a good possibility given that many of these systems are of similar age, similar construct that the vulnerabilities that exist for one are true for others."

(Dillon) The Nuclear Regulatory Commission says it's too early to make conclusions about the size of the contaminated area or the number of leaking pipes. Neil Sheehan is a spokesman for the NRC.

(Sheehan) "This is a process that really needs to play itself out. And as they get more data points, as they drill more wells, as the hydro-geologists do more work, we'll have a much clearer picture of the exact dimensions of this. But this could take some time, and to say that we know the exact dimensions at this point would probably be premature."

(Dillon) Yankee says it's focusing on a part of the plant complex called the "advanced off gas" building.

Spokesman Rob Williams says technicians are preparing to excavate an area near the building where the highest tritium concentrations were found.

(Williams) "We're clearly closer than we were to this source given the higher concentration at that monitoring well."

(Dillon) In the Statehouse, the underground leaks made Vermont Yankee's political task more difficult. The Legislature may vote this year on whether to extend the plant's license for another 20 years.

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