Ahhh, this looks very familiar! I once had a call at a mobile home park where about 8 units had no power... A month earlier a plumbing company installed a sewer cleanout near one of the affected units.. All the utilities in this place were in the same trench.. Tone traced it & lost signal right next to the cleanout.. Lo & behold I found direct burial #1 Aluminum conductors just like this there... I wonder if the plumber noticed a tingling feeling when he was doing his work?
The circuit breaker controlling this did not trip (Zinsco 90A 240V)..