People in Cement Beams

I heard this in history class once and it has always bothered me and i was wondering if anyone else has heard this and if it is true.

when they were building large bridges for the first time in major cities in the US, they would have this massive vats of cement to make those huge columns. my hisory teacher told us that if a worker fell into it they would not even try to help him out cause it would be likely that more would fall in. also they would not dump it out to get his body, because it would be too expensive to redo that much cement and he would be dead anyway. as a result, big bridges built years ago have a lot of dead bodies...

hope anyone can disprove this?