The Coast Guard has been responding to a leaky shipwreck on the bottom of western Lake Erie.
The shipwreck is believed to be the Argo. It’s a tank barge that sank in 1937 and it’s considered the biggest pollution threat from a shipwreck in the Great Lakes.
That’s because it was reported to be carrying about 200,000 gallons of petroleum products when it sank.
Late last week, the response team plugged a pinhole leak in the barge. At that time, air monitors detected hazardous levels of benzene in the air above the wreck.
Lieutenant Greg Schweitzer is with the National Oceanic and Atmospheric Administration. He’s part of the response team and he’s providing scientific support to the Coast Guard. He says the barge no longer appears to be leaking.
Identifying what's on board
Schweitzer says the salvage company contracted by the Coast Guard recently took a sample of the material that was leaking.
“The salvage company designed a special wooden plug with a copper tube in a valve in order to take a sample from the leaking rivet hole,” he says. “Once the sample was complete, the rivet hole was re-secured with a wooden plug in fresh epoxy.”
He says preliminary reports identified benzene and toluene in the sample from that tank.
“And what we've determined from the material that came from that tank is that it's consistent with the historical barge loading records that indicate benzoil is at least a portion of the cargo,” he says.
Original reports from the time the barge sank indicate it was carrying about 100,000 gallons of a crude oil product and close to 100,000 gallons of a product called benzoil.
Schweitzer says to find out how much of this material is still in the barge's eight tanks, the team will need to take samples from each tank.
Eventually, the goal is to take all of the petroleum product off the barge.
"Ultimately to remove the product that's onboard, the salvage company will have to tap and lighter each tank,” he says. “And initially, upon tapping, the first step will be to take a sample before they continue the offload of product."
He says they'll likely use a through-hull technique.
"So what they'll do is they will attach a flange," he says. "Through that flange, they will drill a hole — there's a valve that secures that so that no product leaks during that process. They'll also have to tap an additional hole through the tank to replace the product that they remove, so that there's not a void space and you have a tank collapse. The product that they remove will be replaced with water."
Schweitzer says his team’s main concern is the health and safety of responders on the scene of the wreck.
“NOAA has run a number of air and water trajectories, all of which indicate the primary threat is to on-scene responders,” he says. "I think benzene is a particular concern, because it's a known carcinogen."
To reduce risk of exposure, workers wear protective gear like respirators and protective outer garments.
"We have air monitoring in place that would alert them to the presence of volatile organic compounds, especially benzene,” Schweitzer says.
Schweitzer says there is no immediate risk to anyone beyond the wreck site.
"Current modeling suggests that the hazard is there at the immediate scene,” he says. “If there's good news here, it's that the closest point of land is nine miles away. That's a pretty substantial distance from the actual wreck, and our modeling suggests that if we were to have a large release of benzene, it would evaporate in approximately 30-40 minutes."