This document was prepared in support of the Combined Hydrocarbon Lease Conversion Environmental Impact Statement. The EIS is being prepared by the Bureau of Land Management to determine environmental impacts from proposed development within nine Special Tar Sand Areas. Facilities have been proposed by Amoco Production Company, Chevron USA Inc., Enercor, Mono Power Company, Sabine Production Company, Rocky Mountain Exploration Company, Kirkwood Corporation, Mobile Oil, and Santa Fe Company. Under the combined Hydrocarbon Leasing Act of 1981, the proponents have requested conversion of existing oil and gas leases to combined hydrocarbon leases which would accommodate development of the tar sand resources as well.