improved the biological quality of soils of some large-scale land-reclamation projects. When considering land farming as a waste management option, several items should be considered. These include site topography, site hydrology, neighboring land use, and the physical (texture and bulk density) and chemical composition of the waste and the resulting waste-soil mixture. Wastes that contain large amounts of oil and various additives may have diverse effects on parts of the food chain. Constituents of particular concern include pH, nitrogen (total mass), major soluble ions (Ca, Mg, Na, Cl), electrical conductivity, total metals, extractable organic halogens, oil content, and hydrocarbons. Oil-based muds typically utilize an emulsified phase of 20 to 35 percent by weight CaCl2 brine. This salt can be a problem in some areas, such as some parts of Canada, the mid-continent, and the Rocky Mountains. For this reason, alternative mud systems have emerged that use an environmentally preferred beneficial salt, such as calcium nitrate or potassium sulfate, as the emulsified internal water phase. Wastes that contain significant levels of biologically available heavy metals and persistent toxic compounds are not good candidates for land farming, as these substances can accumulate in the soil to a level that renders the land unfit for further use (E&P Forum 1993). (Site monitoring can help ensure such accumulation does not occur.) Land farms may require permits or other approvals from regulatory agencies, and, depending on soil conditions, some land farms may require liners and/or groundwater monitoring wells. Land treatment In land treatment (also known as land spreading), the processes are similar to those in land farming, where natural soil processes are used to biodegrade the organic constituents in the waste. However, in land treatment, a one-time application of the waste is made to a parcel of land. The objective is to dispose of the waste in a manner that preserves the subsoil's chemical, biological, and physical properties by limiting the accumulation of contaminants and protecting the quality of surface and groundwater. The land spreading area is determined on the basis of a calculated loading rate that considers the absolute salt concentration, hydrocarbon concentration, metals concentration, and pH level after mixing with the soil. The drilling waste is spread on the land and incorporated into the upper soil zone (typically upper 6–8 inches of soil) to enhance hydrocarbon volatization and biodegradation. The land is managed so that the soil system can degrade, transport, and assimilate