Health issue for the game?

Just got off the phone with a friend of mine who is an Environmental Engineer with U.S. Army Corps of Engineers and we were talking about the game. He brought up the subject of field contamination and said that if the playing field had been subjected to "runoff water" for an extended period of time (3-4 hours) then the very real possibility exists for serious contamination passed on to humans. He mentioned things like typhus, tetanus, wound botulism, etc. Said it would take several weeks of sunlight and temperature to reduce the levels in the soil to a safe level. He said if he was the Ath Director there'd be no way he would put his team on that field. Sounds kinda extreme to me but just thought I'd throw it out there.