the waste constituents. Each land treatment site is generally used only once. Optimizing Land Treatment Operations: Addition of water, nutrients, and other amendments (e.g., manure, straw) can increase the biological activity/aeration of the soil and prevent the development of conditions that might promote leaching and mobilization of inorganic contaminants. During periods of extended dry conditions, moisture control may also be needed to minimize dust. Periodic tillage of the mixture (to increase aeration) and nutrient additions to the waste soil mixture can enhance aerobic biodegradation of hydrocarbons, although in practice not all land treatment projects include repeated tilling. After applying the wastes, hydrocarbon concentrations may be monitored to measure progress and determine the need for enhancing the biodegradation processes. Implementation Considerations: Because land spreading sites receive only a single application of waste, the potential for accumulation of waste components in the soil is reduced (as compared with land farming, where waste is applied repeatedly). Although liners and monitoring of leachate are typically not required at land treatment sites, site topography, hydrology, and the physical and chemical composition of the waste and resultant waste-soil mixture should be assessed, with waste application rates controlled to minimize the possibility of runoff. Experiments conducted in France showed that after spreading oil-based mud cuttings on farmland, followed by plowing, tilling, and fertilizing, approximately 10% of the initial quantity of the oil remained in the soil. Phytotoxic effects on seed germination and sprouting were not observed, but corn and wheat crop yields decreased by 10%. Yields of other crops were not affected. The percentage of hydrocarbon reduction and crop yield performance will vary from site to site depending on many factors (e.g., length of time after application, type of hydrocarbon, soil chemistry, temperature). Land spreading costs are typically $2.50 to $3.00 per barrel of water-based drilling fluids not contaminated with oil, and they could be higher for oily wastes containing salts (Bansal and Sugiarto 1999). Costs also depend on sampling and analytical requirements. Advantages of land spreading are the low treatment cost and the possibility that the approach could improve soil characteristics. Land spreading is most effectively used for drilling wastes that have low levels of hydrocarbons and salts. Potential concerns include the need for large land areas; the relatively slow degradation process (the rate of biodegradation is controlled by the inherent biodegradation properties of the waste constituents, soil temperature, soil-water content, and contact between the microorganisms