I have an underground pit where my well tank sits. The top of the pit is
a removable trap door. Because that pit gets some water in it after a
heavy rain, I need to pump it out. I have a sump pump in the pit with an
extension cord that runs into the pit, thru a groove in the trap door.

I checked the pit the other day, and it had some standing water in it.
Then I found the breaker tripped to that pump. I then found why. A mouse
chewed the cord, right where it enters that trap door groove. The mouse
chewed right to the copper on the black (hot) wire. That mouse had to
get electrocuted, but I cant find any remains. The only thing I can
think, is that it was partly sticking out that groove and a cat got it.
Otherwise where the heck did it go?

Temporarily I taped it, but I guess I'm going to have to run wires thru
conduit into that pit to prevent this from happening again. I never
understand why mice chew wires. Wire insulation is not like food???? It
seems pointless why they chew wires....