Coal resources have been known to exist in the northeastern Coahuila region (Fig. 1) since the last century when there was small-scale mining across the border in Texas at Eagle Pass (Maverick County), St. Thomas District (Webb County), and San Carlos (Presidio County), among others (Evans, 1974). With the aim of diversifying energy sources for power generation, the CFE (Comisión Federal de Electricidad) under Manuel Moreno Torres launched the coal development program in 1960; since then, six geological exploration programs have been carried out over what is now known as the Fuentes-Rio Escondido Basin (Fig. 2) as follows: I. 1960 to 1961; II. 1963 to 1964; III. 1967 to 1968; IV. 1973 to 1976; V. 1977 to 1979; VI. 1980.
By 1961,12 million tons of thermal coal had been evaluated for the Venustiano Carranza Thermoelectric Project in Nava capacity of 37.5 MW, consuming 140,000 tons/year of coal from the Rio Escondido Mine developed by the CFE. By 1976, 192 million tons of evaluated probable reserves justified the Jose- Lopez Portillo Thermoelectric Power Station Project, with 1,200 MW of installed capacity in four 300-MW units fed by a total 12,000 tons of coal per day for 30 years. The thermoelectric station is located 25 km south of the town of Piedras Negras in Coahuila (Fig. 2). To date an evaluated 600 million tons of thermal coal represents 45 percent of the tonnage required to satisfy demand to the year 2,000, based on the installed capacity of 18,683 MW for the NOINE