North Stonington — The school district has fenced off areas around the town's elementary school as a precautionary measure due to the long-known presence of polychlorinated biphenyls, or PCBs, Superintendent of Schools Peter Nero said in a letter to parents this week.

The fencing is a temporary measure, requested by the Environmental Protection Agency, to keep the public away from the soil in the area, where low levels of PCBs were detected, Nero said in an phone interview.

"The kids are safe, they're not in danger," said Paul Wojtowicz of Downes Construction Company, which was selected to be the construction manager for the school renovation project, at the School Modernization Committee meeting Monday night.

PCBs were used in the some window caulking, floor materials and paint when North Stonington Elementary School was built in the 1960s. As viscous liquids, PCBs were favored as stable and flame-resistant materials, and were widely used in caulking sealant prior to 1979, the year they were banned by the EPA. The EPA considers PCBs a probable carcinogen.

Nero notes in his letter that roughly 66 percent of schools in Connecticut were built prior to the ban, meaning that most, if not all, of those schools have the same problem. The presence of PCBs alone is not necessarily a cause for immediate alarm, according to a fact sheet from the EPA.

"This is not unique" to North Stonington, Emily Bender, a public affairs specialist at the EPA, wrote Friday in an email.

Testing by school contractor Eagle Environmental LLC prior to the renovations showed that the soil within four feet of the school building in certain areas contained PCBs at levels that were less than 50 parts per million. The EPA and the state Department of Energy and Environmental Protection are in charge of enforcement and set exposure guidelines. Under those guidelines, levels of 500 parts per million prompt the need for evaluation, the agencies say.

The school had three options when dealing with soils containing PCBs, Nero said: it could either begin removing the soils now, and potentially have to remove more when the building project begins; put a special barrier on top of the soils; or fence the areas off. The third option made the most sense because the school building project is so close to commencing, he said.

Fencing was installed in a 10-foot radius of the contaminated soils to keep children away until those areas are cleaned up. The soils eventually will need to be removed to a certain depth, Bender said, which Eagle Environmental estimated in 2015 was between a foot and 16 inches. The EPA has not given the school a timeline to remove the soils.

"This is something that has been on the radar (for) five years now ... we have been in complete compliance" with the environmental requirements, Nero said. He said he expects further testing to be completed soon.

Besides soil testing, Eagle Environmental has done numerous other tests since 2010 to determine the extent of PCBs in the district's buildings. Air samples completed this year by Eagle Environmental show that PCBs are "not a problem" in the air inside the elementary school because they are lower than EPA exposure guideline levels, Nero said.

Abating the hazardous materials was an often-cited problem by supporters of the school renovation plan, which was passed at a referendum in May 2016. The $38.5 million plan includes funding to remove PCB-containing materials from each school.

"None of this was a surprise to the committee," said School Modernization Committee Chairman Mike Urgo in the Monday meeting.

"I'm happy that we have taken the steps over the past year that have prepared us to deal with this in the safest and most affordable way possible for the town," Urgo added.

The Board of Education is planning an informational meeting about the efforts at 7 p.m. Wednesday, Aug. 16, in the North Stonington Elementary School Multipurpose Room.

n.lynch@theday.com