TOPSFIELD – About 50 pupils and teachers are expected back in classes Monday at a northern Washington County school where a well accident contaminated drinking water.

The accident occurred about a month ago when a submersible well pump was being replaced. A piece of piping and the pump fell to the bottom of the 500-foot-deep well, and tests later showed contamination by polychlorinated biphenyls – commonly referred to as PCBs – which are suspected carcinogens.

A local well driller was called to the site and by Tuesday the old pump had been fished out of the well. Workers from another company were flushing the well.

After the new pump was installed about a month ago, Chuck Murphy, the school’s teaching principal, ordered bottled water used in the school because of the expected stirring up of sediment.

Murphy and other school officials did not know the pump broke when it fell back into the well, spilling a small amount of nonhazardous mineral oil and about an ounce of PCBs.

Once the extent of the problems with the water system was recognized, the pupils’ spring break was extended from five schooldays to two weeks.

Some questions remain unanswered, including the date the accident occurred, the identity of the company hired to replace the pump, and the cost of the project and resulting cleanup. Superintendent William Dobbins was unavailable for comment Tuesday.

Roger Crouse, assistant director of the state Department of Human Services’ drinking water program, said that although the school district would not be fined, it would receive a violation for PCBs in the water.

“It means that they exceeded the allowable limits” for PCBs, he said. “And they have to notify their customers that they had this level of PCBs in the water and they have to report back to us that they did provide public notification and that resolves the violation.”

Murphy said the lost pump didn’t raise any red flags because school officials were told that because the pump had been in the well for years, it could remain there.

“We were told … there’s going to be sediment, there’s going to be some petroleum products that will work [their] way through. PCBs were never mentioned as a possibility at all,” Murphy said.

Pumps manufactured before 1978 commonly used PCBs as lubricants.

“I can’t swear that no kid took a drink out of a fountain in the bathrooms,” Murphy said Tuesday, “but they all say ‘Don’t drink the water,’ and we met immediately with everybody and reminded them that there was bottled water right in their classrooms,” he said. “Besides, who is going to drink water that smells bad anyway?”

Located 36 miles from Calais, the school serves 45 pupils from Topsfield and Codyville Plantation, along with tuition students from Brookton, Lambert Lake and Waite. It is located on Route 6, just west of the intersection with Route 1.

Murphy said Tuesday that getting the school’s water system back on line has been a monthlong problem.

When he arrived at school on a Friday morning about a month ago, there was no water pressure. School was called off and the following Monday a new pump was installed.

School officials detected a smell to the water soon after the new pump was installed. Some people said it smelled like kerosene, while others said it had a diesel smell. School officials ordered that the water fountains be covered, and pupils were told to continue drinking bottled water.

More bottled water was brought in and the five staff members even filled large containers with water to be used in the kitchen. “Teachers took [the large containers] home and filled them [from] their own wells and brought them back, and we boiled that water to wash dishes,” he said.

The smell persisted and the school called in Norlen’s Water Treatment LLC of Orrington.

Norlen’s tested the well and found a barely detectable amount of gasoline-range organics. Norlen’s called the state to check on whether there had been a spill in the area.

A Department of Environmental Protection staffer and a field staffer for the state drinking water program were at the site April 18. They took water samples, and test results obtained April 21 indicated PCB concentrations of 79 parts per billion.

Murphy, who was away, said he learned of the PCB problem last Sunday night.

At Daggett’s Country Market in Topsfield on Tuesday, people seemed less concerned about the well problem than about the fact that their children were out of school.

Parent Corey Porter, who has a second-grader in the school, said he did not understand why school officials hadn’t moved classes to the nearby Brookton Community Center. “I just didn’t understand why they needed another week off. They have to make it up this summer,” he said.

Porter said he first heard of the school’s water problem at the nearby Brookton Store, where a notice had been posted.

On Sunday, he said, he received a telephone call from the janitor telling him there would be no classes this week. “They just told us they had water problems, that’s all we heard,” he said.

Murphy said letters were sent home initially, but school officials learned about the PCB problem while everyone was on vacation, so no new notices had been sent.

Technicians will continue to flush the system this week, and Murphy said that would delay the reopening of school until Monday. “We will have bottled water again because the water is not going to be drinkable until it runs for a few days.”