It turns into sludge on the bottom and doesn't dilute there are several fishermen per year contaminated when the sludge sticks to fishing gear.
The royal engineers teaching on getting rid of it involves loads of pallets a drilling charge loads of diesel and 20meters of det cord.
You make you set the case on a couple of pallets with charge attached then run det cord out to a safety fuse. Put a ring of det cord 5m out around it and attach to first bit of det cord to the drilling charge. Cover centre bit with loads of broken pallet. Put a circle of wood over the circle of det cord. Soak every thing in diesel.
20 min safety fuse light and wobble off in your noddysuit.
Gives a mini nuke mushroom and the center gives the required 800 deg for 2 mins that they reckon is enough to do most things. All the fumes are lifted high by the mushroom.
Again this is 25year plus memories.