This weekend the US Coast Guard recovered 10,000 gallons of benzene from the wreck of a tank barge that sank 78 years ago in Lake Erie. The Coast Guard has pumped the first of 8 tanks on the wrecked barge.

In August, Tom Kowalczk, a member of the Cleveland Underwater Explorers (CLUE), discovered the wreck of the 125′ long tank barge Argo in 45 feet of water 8 miles east of Kelley’s Island Shoal. The divers noted a strong chemical odor in the water. According to the National Oceanic and Atmospheric Administration (NOAA), the Argo sank intact carrying more than 100,000 gallons of crude oil and benzol.  Benzol is a coal-tar product consisting mainly of benzene and toluene. The National Museum of the Great Lakes in Toledo says that the 4,700 barrel barge was operating illegally when it sank on Oct. 20, 1937, while under tow by the tug Syosset.

Michigan Live.com reports: The National Oceanic and Atmospheric Administration (NOAA) has described the Argo as the worst pollution threat from a Great Lakes shipwreck.

The Coast Guard shipped in six 21,000-gallon steel tanks specially designed to hold chemicals like benzene, a buoyant, flammable industrial chemical used in making plastic. Toluene, Xylene and trace elements of petroleum were confirmed through sample testing, according to the Coast Guard. The mixture is consistent with the chemical makeup of benzole, a vintage petroleum product.

Historical records are vague on exactly what chemicals are on board and where they are located in the sunken ship. Cargo records are lost for the Argo, which historians say was operating illegally when it sank. The sampling process is ongoing as crews tackle the toxic cargo tank by tank.

Estimates vary on how much cargo is trapped on board. Old newspaper accounts say 4,700 barrels, which equates to about 197,400 gallons.

“Our first priority is to get the benzene out,” McKenzie said. “That’s the biggest threat. We’re still trying to figure out which of the eight tanks carries what.”

The offloading process involves pumping water into the wreck and forcing the chemical into a second hose that carries it topside, where the mix of benzene and lake water is tanked and filtered to remove flammable vapors. Crews on the surface are working in Hazmat gear to avoid exposure.