I am pretty sure it is not raw sewage. There were 2 people in it yesterday up to their hips and they were wearing just pants and a T-shirts. If it was raw sewage then they would have had protective clothing on or chest high waders at the very least on.
Tito Lacle said that this pond was nothing but rain water. It does not have a runoff, it just dries up.
Actually, the part of that post I found interesting was the part about "salinas," or the salt content. Since salt is a preservative, it may bode well for the investigation. Just conjecture.