WESTON — Sewage leak repairs at Weston Middle School unearthed more than just dirty water, and it’ll take nearly $500,000 to fix.

Board of Education Chair Gina Albert said Thursday that the Board of Education plans to request $365,834 from the town to cover costs associated with a February septic tank leak in front of the school.

The overflowed tank, which forced the closure of Weston Middle for several days, should have been deactivated after the nearby Zenon treatment plant was built 15 years ago, according to a report by facilities director Joseph Olenik shared at the Facilities Committee’s March 7 meeting, but it never was. Apparently, waste had been flowing into that tank since 2004.

Matt Bernardini, of Veolia North America — the contractor that manages Zenon — said a “necessary connection” was not made to the plant, which eventually caused the sewage system failure at the middle school.

However, he said it doesn’t appear any of the wastewater was leaching into the ground.

While working on repairs, Veolia also discovered an abandoned septic tank by Revson Field, which will cost another $96,000 to remove.                      

The Zenon plant replaced the need for septic fields near the schools when it was constructed. However, the tank in that area of the middle schools was never removed as required by Connecticut public health codes, the report said.

“We discovered it while doing this other correction and we need to get it out of there,” Superintendent William McKersie said Wednesday, noting proper procedures will be followed.

An additional $9,000 is being requested to repair a septic line at Hurlbutt Elementary, bringing the total request to $470,834.

The education board must ask the boards of selectmen and finance for a special appropriation for the projects, McKersie said, though a meeting has not yet been scheduled.

“Our district administration has been working very closely with town administration on this matter,” Albert said during a Board of Finance meeting on March 26.

Finance board member Melissa Koller noted the amount would likely come out of the town’s general fund.

Veolia is set to remove the abandoned tank over the students’ spring break, beginning April 15.