School officials believe the diesel tank had been used to fuel heaters in the old agriculture building back when the K-8 school was Bulls Gap High School.
Director of Schools Clayton Armstrong said Sunday he didn't even know the tank was there. It might have been above ground at one time.
As of Sunday morning the tank was buried between a retaining wall and a corner of the school where the newer elementary classroom wing connects to the rest of the school.
Sunday morning someone noticed fuel leaking out of the retaining wall and spreading along a paved parking lot.
The Bulls Gap Volunteer Fire Department and Hawkins County HAZMAT team were contacted, and the spill was contained in the parking lot with sand bags and an absorbent material.
Environmental cleanup contractor HEPACO Inc. was also called to the school, and as of Sunday afternoon was beginning the process of removing the tank. Armstrong said classes at Bulls Gap School were canceled for today due to the odor and noise that the tank removal will create.
"We have it contained," Armstrong said.
"HEPACO has been here and they put down a solvent. It has not gotten into any sewer system, so that much we have to be thankful for," he said.
"I don't know who noticed the leak and called the Bulls Gap fire department, but we're grateful because it could have been a lot worse."
It's not known how much fuel leaked out. A section of the retaining wall was dug out and it was discovered that the leak originated on a tank valve.
About 1,200 gallons were pumped out of the tank. Initial reports were that more than 100 gallons had leaked out. By Sunday afternoon the tank had been partially uncovered, and Armstrong said HEPACO had indicated to him the spill was not as serious as originally thought.
"We won't know the extent of the spill until they get the tank uncovered," Armstrong said. "At the base of the retaining wall, when they dug it out, was a small valve and they did plug that. That's where it was leaking.
"There is a puddle where they dug down and it looks like maybe four or five gallons in a puddle, but then it was also streaming - a small stream across the parking lot in the back."
Armstrong said he has not been able to find anyone who even knew the tank existed.