HEBRON — State environmental and health officials told parents Tuesday that a carbon filtration system will be in place shortly to ensure that Hebron Station School’s well water will pose no threat to students and staff.

Once the filtration system is in place, the Department of Environmental Protection is expected to lift a “do not use” order that has been in place since a 1,900-gallon oil spill was discovered at the school in late December. The filtration system is a precaution. No contamination has been found in the well water.

“This is a significant spill for us,” DEP Oil and Hazardous Materials Responder Sheryl Bernard told several dozen parents, school staff, SAD 17 directors and Hebron selectmen at a nearly two-hour meeting at the school.

The heating oil leaked out of the school basement tank Dec. 24 as it was being filled by a driver from the C.N. Brown oil company of South Paris. The accident forced about 135 elementary students to relocate to Oxford Hills Comprehensive High School in South Paris following winter break. On Monday, they were allowed to return to the school after alternative plans for a water supply were put in place.

Bernard, who was one of five speakers from state agencies, said it is probable that much of the oil will never be recovered because it is trapped under a cement slab in the oil tank room. But, she stressed, monitoring systems are in place and will continue to be in place in the months, if not years, ahead. It is to ensure that what remains does not harm the air quality or well water.

The staff and students are using water from the school’s 8,000-gallon water tank, which provides water for fire suppression and is adequate for consumption.

Once the filtration system is installed, the state will give the OK to use the school’s well again. The system is in the school but has not yet been set up. It is expected to be operating as soon as the end of the week.

Brad Haln, a DEP geologist, said things can change in the long term, and the well could become contaminated as oil continues to seep underground, but the filtration system will take care of any contaminants before the water reaches consumers.

“You never know what’s going to happen,” Haln said. “Right now, the well is not contaminated but we have a backup (with the carbon filtration system) if anything happens.”

Additionally, the well will be monitored with pump tests and any oil recovered at a later date could be treated through a system that would pump for oil “24/7.”

Michael Abbott, a hydrologist and water resource team leader for the Maine Drinking Water Program, said there was nothing found in the well that was cause to be “overly concerned.”

“Even if it gets impacted, (no contaminants) will get into the school’s water system,” he said.

The school also has access to bottled water supplied by Poland Spring Water Co. and Walmart, Superintendent Rick Colpitts said.

Andrew Smith, a state toxicologist for the Maine Center for Disease Control and Prevention, said the contamination in the air has decreased by about 75 percent from the first week after the spill. The highest levels of contaminants were found in the gym.

More than 1,700 gallons of oil is believed to have been trapped beneath the school’s basement tank room, which is on a concrete slab, and a small amount leaked into nearby wetlands. Pads are absorbing the oil in the wetlands as well as a small amount of oil coming from the perimeter drains.

Maintenance workers at the school asked C.N. Brown on Dec. 23 to fill the 2,000-gallon tank because the fuel gauge showed it was running low.

An oil truck came the next day and pumped in about 160 gallons before a whistle that indicates there is space in the tank stopped blowing. Usually, Colpitts said, if the whistle stops, it means the tank is full, but in this case, the fuel gauge continued to read empty so the driver decided to continue pumping.

Oil overflowed and sprayed out of several parts of the tank, covering the floor of its self-contained concrete bunker under the school with about a foot of oil.

School officials were assured by C.N. Brown that someone would be back to pump it out immediately, but Colpitts said that never happened. The room emptied of oil within six hours and was found that way by school maintenance workers on Dec. 25.

Colpitts said C.N. Brown is paying for all cleanup costs, but that does not mean the school district will not be liable for some of those costs.

He said the school district does not know the costs of the cleanup.

“C.N. Brown right now has stepped up to the plate and is paying all the bills,” he said

Bernard told parents and officials concerned with the oil being left that the building would have to be taken down to ensure they got all the oil.

“You never get it all,” said Bernard, who has been cleaning up oil spills for the past 24 years. “You get them to the point where they’re not going to harm anyone. We never walk away.”

ldixon@sunjournal.com