PROVIDENCE — The House Finance Committee is expected to vote June 7 on a bill (H8072) that would fund an addition to the Chariho Regional Middle School. The Wood River Junction school, unfortunately, sits on top of an oil plume, leaked by a faulty underground oil tank.

According to the company cleaning up the oil, GZA GeoEnvironmental Inc., the leak began some time after the school was built in 1989, when a fuel line that connects to a 10,000-gallon storage tank allowed heating oil to essentially pour directly into the soil. The resulting oil plume sits atop groundwater, about 20 feet below ground. The size of the plume is unclear, but GZA said the oil could be gone or that up to 20,000 gallons remain. A bio-venting and vacuum system removes about 3,000 gallons of contaminants annually, and the plume should be cleaned up in no more than seven years, GZA has estimated.

Mimi Karlsson, a retired Environmental Protection Agency (EPA) official, is concerned that toxic oil additives within the plume pose a health risk and that construction shouldn’t go forward for fear of releasing those pollutants. The Hopkinton resident worries that the oil additives and dispersants initially used to contain the spill contain carcinogenic polycyclic aromatic hydrocarbons (PAHs). Karlsson wants a formal review of the project by the EPA.

“Building on this site so close to the underground pool of oil could contaminate the entire Chariho aquifer, contaminating their wells and poisoning the students and staff,” Karlsson wrote in a recent e-mail to ecoRI News.

GZA, however, told the School Committee that construction would take place at the opposite side of the building from the oil leak and would pose little if any risk. The construction would be limited to a slab foundation rather than a subfloor structure, further reducing exposing the oil plume, according to GZA.

The Rhode Island Department of Environmental Management (DEM) has agreed with GZA that construction will not interfere with the clean up of the oil plume. DEM has monitored the leak and heating-oil plume since 1999. The school district discovered the leak after fuel deliveries were about 8,000 gallons above the average.

“With a leaky tank, no one knows precisely how much (oil) was released,” said John Spirito, a principal at GZA, during an April 12 School Committee meeting.

GZA took over the clean-up efforts in 2011. A previous pump-and-treat effort removed about 200 gallons of oil a year at a cost of about $90,000 annually. GZA’s treatment and monitoring costs about $17,000 a year.

The Senate approved its version of the bill (S2805) May 24, which would allow the school district to issue up to $6 million for the project.