The model they're operating under is a bell curve of failure rates where the bell is thankfully very wide and centered many decades in the future.
Made up numerical example, if you have a lake where the bacteria can literally eat one barrel of crude per month, and 10 barrels at the bottom of the lake, you're in pretty good shape if one breaks open at a time spread over a century, but fairly well screwed if all 10 rust open at the same time at the six month mark.
Made up numerical example, if you have a lake where the bacteria can literally eat one barrel of crude per month, and 10 barrels at the bottom of the lake, you're in pretty good shape if one breaks open at a time spread over a century, but fairly well screwed if all 10 rust open at the same time at the six month mark.