Demucking 104 acres in Orlando, FL

Sounds like you may be looking at a future of subsidence problems on this site. At a minimum, the homes should be built on pads that can "float" out the bearing strength needed for the homes. Otherwise, there will be major structural integrity problems down the road.

Best recommendation? Get some higher end ground for your low end residential if the economics can be worked out on land value. Otherwise, consider whether the market can handle a little more expensive housing on a more geotechnically reliable site.

I don't know exactly what you mean by "muck", but I wonder if over excavating the footers and backfilling with gravel or better soil would be an option. If you are building in a building pad I assume you are elevating the pad so your original ground will need to handle to bearing loads. What did the borings say exactly and what are the charactericts of this muck. What kind of soil is it. Do you have any bearing capacity info? blow counts from spt testing perhaps.

As stated by others, you don't say what you mean by "muck", but if it is peat (organic content of 30%, or greater), watch out. Most organic soils are highly compressible, and exhibit secondary compression settlement behavior which can go on for over 20 years. Peaty soils are compressible even under relatively light loads. Placing permanent fill will make things even worse. These soils can be surcharged with a temporary fill embankment (with surcharge pressure equal to at least 1.5 times the permanent fill and structure footprint pressure)in 2 or 3 months, and then a monolithic slab/footing system used to allow for some long-term differential settlement. If excavation and replacement is not an option, consider short piles such as treated timber or helical piers--these will probably cost about $20/foot. The owner/developer should be made aware that these soils are highly compressible, difficult to predict settlement behavior, and could result in lawsuits down the road if the site is not prepared properly.