An oil barge recently discovered at the bottom of Lake Erie—nearly 80 years after it sank—has brought a renewed focus to the environmental dangers posed by dozens of shipwrecks littering American waters, the Detroit Free Press reports. According to the AP, 87 shipwrecks are included on a federal registry of the greatest pollution threats to US waters. Approximately 75% of those vessels sank more than 70 years ago—a lot of them were torpedoed by German submarines in WWII—meaning it's only a matter of time until they start leaking oil or other substances due to rust and corrosion, if they haven't already. But cleaning up those wrecks is easier said than done.
Only half of the 87 shipwrecks on the list have even been found, the AP reports. And those are just the wrecks we know about. "We could look every year for 100 years and not find all of the shipwrecks on the Great Lakes," a local historian tells the Free Press. And even the shipwrecks that have been found often haven't been examined for leaks, the AP reports. "Some of these are wicked deep and not in an area where you could do survey work," says Lisa Symons of the National Oceanic and Atmospheric Administration, which started looking at potential environmental threats from shipwrecks in 2010. Finally, there simply isn't enough money for a cleanup operation that size. Fortunately, disaster isn't imminent. According to NOAA, any leaking oil is likely to come out in drips rather than catastrophic gushes. (Read more shipwreck stories.)