One of favorite fields DD played in all the stands were concrete and the outfield wall was who knows how far back and 12' or so high.
It was a retaining pond so the houses did not flood.
They could of put up a temperoray fence I suppose but I didn't care and no else seemed to either.
It was actually pretty neat, someone put some thought into it.
Baseball field used as a retention basin you say? This just opened nearby, bummed they put in two baseball fields and no softball field.