FARMINGTON — Mt. Blue Middle School will remain closed Friday while crews continue cleaning up Number 2 fuel that spilled on the grounds Tuesday.

An oil delivery resulted in an overfill because an alarm failed. That caused  fuel to seep out of the tank through a vent in the school’s central courtyard.

Personnel from the Maine Department of Environmental Protection’s Bureau of Remediation and Waste Management remained on the scene Thursday, along with workers from Environmental Projects Inc., the cleanup contractor hired by C.N. Brown.

While the DEP staff has still not been able to determine exactly the amount of oil that discharged from the 10,000-gallon tank, the delivery was for 1,500 gallons, so they know it was less than that, and may actually be under 500 gallons, Samantha DePoy-Warren, DEP spokesperson, said.

A DEP agent estimated 40 gallons was cleaned up from a catch basin Tuesday afternoon but crews continued to work Wednesday and Thursday. 

About 350 students were evacuated around noontime Tuesday and remained at the school for their regular bus run.

The stain on the soil is about 10 feet by 30 feet and so far, workers have dug down three feet and are still finding saturated soil, so it is a significant spill and more than the 100 gallons initially estimated, DePoy-Warren said.

Cleanup is complicated by the fact that the courtyard where the spill occurred is surrounded on all sides by the school building. That makes it inaccessible to the excavation equipment that would typically be brought in to help with cleanup.

The contaminated dirt is being loosened with shovels and sucked up by two vacuum trucks that have hoses running through the hallway into the courtyard.

The plan is to temporarily cover the hole Friday so that school can resume Monday, and then finish the cleanup after school closes for the summer.