Basically soil farms take in oil field luquified wastes which include things like drilling mud that can not be reclaimed, salt water as a result of production, or solids that have come off of tank bottoms, and other similar types of fluids and light solids. These are then mixed with dirt in an order to dilute them into a substance that is considered non-hazardous.

The only reason I know this is because I recently helped implement a process that uses a centrifuge to seperate the liquids from the solids. The liquids are either reclaimed or re-injected into a deep zone. The solids are then capable of either recycling or disposal in another form but are no longer as hazardous as they once were to shallow potable water or adjoining farming operations.

I can also tell you that spills have the capability of running several miles. You do "not" want these type of operations close to environmentally sensitive areas. Different deal in the west Texas waste land where a spill is not an issue.