[alexandria]

I know your feeling on manure pits and it's reasonable, but how could he have avoided being overcome with fumes himself?

First of all, I am speaking of the "open air" lagoon type pit. There is not much danger of fumes with these types of pits unless it is maybe as they are stirring and moving some of it to the trucks to be spread.
I got the impression (growing up here) that the big danger with these pits is that once you fall in you cannot extract yourself and without a rope handy would NOT be able to rescue someone else. Think quicksand thin and slimy.

[Wednesday's Child]

I do know what type of pit you're talking about. It could be described as a lake. The reason I wonder about the fumes is that last year, a farmer in upstate N.Y. went into one of these pits to rescue a calf. He hardly took more than a few steps and was totally overcome by fumes and died, as did the calf. This was not an isolated incident...it happens.......That is why I wondered about the fumes. I'm not disagreeing with your theory, only wondering how it could be accomplished.

[alexandria]

Finally found a photo close to what I was trying to describe. See at : http://www.united-tech.com/wd-images/m5-wd-dcl4x1-1.jpg

Now usually the sides are sloped up quite a bit more like a large dirt-type canal bank. Also note that mud along with water and waste is fed into this pond. Since mud is heavier it sinks towards the bottom and carries things down with it.
Also, this particular photo shows more water on the top than most have. Most look like a solid crust that you could almost walk on.