Yahoo. Pored the slab for the generator shed yesterday. The slab has the propane tank muffler embedded in it with the exhaust going under the slab and out the side of the hill pointing away from the house. I used 13' of 2" galvanized pipe from the outlet of the propane tank and sloped it down wards so it will drain. The slab is 6.5' square, I would have liked to make it bigger, but there is not any more room beside the house. Now all I've got to do is fill the big 2'X4' hole in the middle of the floor with another yard of concrete to mount the engine.
We mixed our concrete with a 3.5 cu ft mixer and it took about 12 batches to do the slab.