CHICAGO (CBS) — Five hours,  75 firefighters and a quarter of a million gallons of water.

That’s what it took to put out a massive chemical fire at a vacant Park Ridge gas station that left two firefighters injured.

CBS 2’s Megan Hickey asked why the building was filled with a potentially hazardous chemical, and why the fire department didn’t know about it.

There were 90,000 pounds of calcium peroxide in the vacant building and the owner will be cited for failing to report it to the city. The fire department said dozens of firefighters were put in danger. And the property owner can also expect a bill from the city.

Park Ridge’s fire chief said they knew something was fueling the massive blaze at a vacant gas station near Oakton and Northwest Highway Wednesday night.

But it wasn’t clear until they saw this: hundreds of thousands of gallons of murky, white water rippling out of the smoky building.

“Nobody suspected that there was such a quantity of product being stored there,” said Jeffrey Sorensen, Chief of the Park Ridge Fire Department.

The building was filled with calcium peroxide and firefighters should have known about it, according to a local ordinance. Instead they went in blind, including neighbors such as Daniel Mariner.

“I smelled, actually it started as burning plastic smell, ” said Mariner, who watched from his window in shock. And he didn’t hear about the chemical commonly used for treating soil until after the Illinois EPA arrived on the scene.

“They’re putting other people at risk. And I heard a couple of firefighters got injured,” Mariner said. “It could have been much worse. People could have died.”

The Illinois EPA said citations haven’t been determined, but the state doesn’t regulate this particular chemical. It’s trying to contain the runoff with vacuums but some of it did enter the sewer system. A team is monitoring the water for contamination.

As for the firefighters, two were treated and released for chemical burns.

But the biggest price will be cleaning and possibly replacing all of the turn out gear, hoses and vehicles, which are now covered with an alarming film. And they don’t know if it’s safe.

Chief Sorensen said that once they have an estimate, they’ll be sending the bill.

“I would say certainly tens of thousands of dollars is very reasonable,” Sorensen said.

CBS 2 has learned the property was recently purchased by a Chicago-based limited liability company and the site was being cleaned up for business use in the future. CBS 2 reached out for comment.

So far no response.

Megan Hickey