Work on the Park District’s expansion and renovation of its administrative building has been delayed for a month while crews deal with soil contamination caused by a leaking underground storage tank that no one knew existed.

The discovery was made on the very first day that work began in May. Workers were excavating soil and came across a 1,000 gallon oil storage tank just east of the building, according to Park District officials. The soil around the old tank gave off the distinctive smell of oil and workers stopped digging immediately.

For the past month the project has been delayed while the soil is tested and arrangements made to remove the contaminated earth. The discovery has cost the Park District $11,000 so far, according to Executive Director Larry Piekarz, and additional bills are expected. Invoices for shipping the soil and other related expenses have not yet been received.

The $2.1 million project is expected to be completed in November.

“It’s pushed us back about four weeks,” Piekarz said.

The oil tank dates from the 1930s, which coincides with the completion of the administrative building in 1938. It is presumed to have supplied the facility with fuel for heat. Oil has not been used to heat the building for decades.

Last week, the soil was finally removed and taken to a landfill equipped to handle the pollutants.

“Any contaminated soil is gone,” Piekarz said.

Numerous soil samples have been sent to the Illinois Environmental Protection Agency for testing. The area of contamination spread beyond the original area of the tank. The area excavated measured 17-feet long, 20-feet wide and more than 5-feet deep, according to a report form the Park District’s consultant, G2 Consulting in Wheeling, Ill. The Park District is still waiting for the state EPA office to give permission to resume work in the contaminated area.

“We have permission to start working on stuff that’s not going to affect that area,” Piekarz said. “We’re still waiting on soil tests and then we wait for the Illinois Environmental Protection Agency for a final sign off that we can actually begin working in that area.”

Piekarz said he did not know how quickly the EPA would issue that letter.

Work has resumed on the project in other areas and contractors have started to install the footings for the foundation of the new addition.