The question then should be, why was the lid so cheaply constructed that someone could fall through it?
Probably rusted. Those grease trap lids are usually built like manhole covers.
I'll take "lawsuit" for $200, Alex...
And for the pain and heartbreak of losing a toddler...the jury will be on the parents' side. My dad was a Chicago defense attorney, and a very good one.
He would not have wanted to take this one on.
Maybe it was a very old grease trap and the rim ring that supports the lid and keeps it from falling in had corroded in places... so that when she stepped on it, the lid tipped inward with nothing to stop it, and she slid through.
If no one had used that grease trap in years maybe no one ever had a reason to lift the lid and so, the corrosion beneath was never seen.