HEBRON — More than 970 gallons of oil, about 88 percent of the 1,100 gallons that spilled into the wetlands at the Hebron Station School in late December, have now been recovered, a Department of Environmental Protection spokeswoman said Wednesday.

Additionally, a water sample was taken at the perimeter drain outfall pipe, and no petroleum was detected in the effluent from the pipe, DEP communications director Jessamine Logan said.

“We will continue to monitor weekly,” Logan said. “Natural processes, evaporation and biodegradation will continue to break down any remaining oil.”

Environmental officials have been on site since late December, recovering as much as they could of the 1,500 gallons of oil that spilled from the Hebron Station School’s tank room on Dec. 25. About 1,100 gallons of oil seeped through discharged pipes into nearby wetlands off Station Road.

The oil leaked out of the school basement tank as it was being filled by a driver from the C.N. Brown oil company of Paris. A total of 192 gallons was recovered initially from the wetlands next to the school by sorbent pads, but most was captured in ice and snow in an area about the size of a football field.

Although environmental officials have been on site almost daily throughout the winter months, recovery of the oil in the wetlands could not start until the ground began to thaw in April.

Workers from Environmental Projects of Auburn are on site this week, removing the outermost hay-bale check dam, Logan said. She also said that sorbent pads in the wetland area are not accumulating oil and will be removed. The sorbent boom remains in place at the outfall of the drainage pipe, where a thin sheen of oil is visible.

The sorbent boom was placed at the inlet and outlet of the railroad bed pass-through, and pads were placed in front of the sections of the boom to add protection between the oiled wetland and Bog Brook. DEP officials have said the oil does not pose a threat to the nearby brook, which flows downstream into Minot and Mechanic Falls.

School officials closed the school for more than a week after the spill. The gymnasium, which is next to the oil-tank room, was closed for two months while state environmental and school officials monitored the air quality. DEP officials have said the school’s well water was not contaminated.

ldixon@sunjournal.com