HEBRON — About 1,800 gallons of heating oil were still unaccounted for Thursday at the Hebron Station School as state Department of Environmental Protection officials tried to find the spilled fuel.

A total of 1,900 gallons of oil leaked out of the basement tank Dec. 24 as it was being filled by a driver from C.N. Brown oil company in South Paris.

SAD 17 Superintendent Rick Colpitts said no oil was found in the four test holes drilled Thursday on the perimeter of the property, but a minimal amount discharged through “weeping holes” of a perimeter pipe.

Some oil was found in nearby wetlands and has been mopped up with no discernible damage, he said.

DEP officials will return to the school Friday with a smaller drill for a confined area in the basement.

“The goal is to find out where the oil went,” Colpitts said. “They will then develop a plan to eradicate it.”

Results from water and air quaility tests conducted in the school Thursday were expected Friday.

Students and staff will not be allowed into the school on Station Road until at least Monday. If they cannot return then, school officials will announce an alternative plan.

Colpitts said 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.

The next day, an oil truck pumped in about 160 gallons before a whistle that indicates available space in the tank stopped blowing. Although the whistle stop usually means the tank is full, the fuel gauge continued to read empty, and the driver decided to continue pumping, Colpitts said.

As a result, oil leaked from an emergency relief valve, which is designed to prevent damage to the tank if it is overfilled. The self-contained concrete bunker under the school filled with about a foot of oil. School employees were told C.N. Brown would be back immediately to pump out the oil, Colpitts said.

But two days later, on Dec. 27, a DEP team was called to the school after school officials found the room empty but suspected the oil had not been pumped out, but rather leaked out of the containment room.

Although C.N. Brown President Jinger Duryea acknowledged the incident and apologized for the “inconvenience,” in a brief news release issued earlier this week, efforts to reach the company for further comment Thursday were unsuccessful.

Colpitts said the company has “accepted responsibility” for the incident.

Colpitts said the self-contained bunker where the oil leaked is made of concrete, a porous material. The Department of Environmental Protection has said it was probably not a containment room because they are usually lined with fiberglass.

“The school was led to believe it was a containment room. Within six hours, the oil in the room leaked out into the ground,” he said.

The confinement room is under the gymnasium wing. The only room with a strong oil odor was the gymnasium, Colpitts said. That odor had dissipated greatly by Tuesday, when he was last there, he said. There are no classrooms near the area where the oil leaked.

Although the ground is partially frozen, Colpitts said that would not have stopped the oil from getting underground because the heat from the building mass itself and the large amount of sand under the building would probably prevent extensive ground freezing.

This is not the first time the Oxford Hills School District has dealt with an oil spill at one of its schools.

In November of 2011, a thief stripped copper piping from an oil and propane tank at the Otisfield Community School on Powhatan Road, causing more than 100 gallons of heating oil to spill on the ground over Thanksgiving Day weekend. The tanks fed two portable classroom units on the east side of the main building.

The bill for the cleanup and restoration amounted to $44,911. The Maine Department of Environmental Protection paid for the small amount the school insurance did not pick up.

In this case, the costs will not be known until it is determined how bad the damage is and who is responsible. The fact that the containment room may not have been a real containment room is being looked at as part of the overall review, Colpitts said.

“We’re looking at all options,” he said.

ldixon@sunjournal.com