Deposits of low rank Tertiary brown coal formed in the Sedan area on the western margin of the Murray Basin, ~80 to 100 km north-east of Adelaide, have been investigated as potential sources of fuel for electricity generation. Attention has been focussed on the largest deposit located near Sedan, which contains almost 200 Mt of coal within two seams averaging 6 m thick that lie between 32 and 55 m below the surface. The coal is classified as Lignite B by the Australian Society for Testing of Materials (ASTM), with a low heating value and moderate ash, high moisture, and relatively high sodium, chlorine and sulphur contents. The other, but much smaller Anna coal deposit, located 8 km away to the north-northeast, is of similar quality, but is buried more deeply. The deposit at Sedan was discovered by CSR Ltd early in 1979 whilst it was drilling into gravity anomalies that border the Long Ridge granitoid intrusion (with 36 rotary percussion holes for a total penetration of 2283 m, including 31 m of rotary coring). Follow-up drilling was performed during September-October 1979 (26 holes for 1770 m, including 15 m cored), but at that stage the limited lignite intersections that had been made provided little economic encouragement. CSR next undertook an orientation resistivity survey over the known, SADM-drilled nearby coal occurrence at Anna, which had a measured in situ resource of about 60 Mt. The survey proved successful in delineating the presence of coal seams, and their depth. In consequence, a more extensive resistivity survey was done at Sedan during mid-1980, followed by a close-spaced resource definition drilling and geophysical logging campaign carried out during the ensuing year (151 rotary percussion holes for 15, 907 m, including 301 m of coring in 15 holes). An indicated recoverable coal resource of approximately 150 Mt was outlined, with a likely strip ratio of 8.5 cubic m/t. Further drilling was conducted in November 1981 to gather data for hydrological and geotechnical purposes (13 holes for 1493 m), and early in 1982 large diameter coring took place in 22 holes to obtain bulk coal samples to submit for specialist laboratory-based combustion, coal quality and other critical material tests. In March 1982 CSR submitted a preliminary proposal to ETSA for supplying coal over a long term to fuel a proposed new 750 MW conventional thermal power station that would be required by the 1990s to provide additional base load electricity to support expected industrial and urban growth. Because several other large untapped brown coal deposits exist in South Australia which are controlled by competing interests, CSR was anxious that its Mannum Project's advantages for electricity generation be made known to the potential buyer as early as possible. During mid-1982, another 53 drillholes for 3223 m, including 209 m cored, were completed at Sedan to improve the coal resource estimate. This drilling revealed some local substantial thickening of the coal seams. A detailed mining study and commercial development proposal was finalised by CSR in December 1982 and given to the SA Government and ETSA for review. In it CSR was seeking to establish a 20-year sale and supply contract with ETSA, commencing in 1990, for ETSA to take the full mine production tonnage from its Sedan area brown coal deposits, as a fundamental requirement for CSR proceeding with the risked development to mine and process a total of 110 Mt of coal, out of 182.1 Mt of measured in situ reserves. No further on-ground work took place on EL 998 until early in 1987, while in the meantime a number of specialist office-based technical studies were completed and evaluated by the stakeholders. These were primarily directed at providing satisfactory answers to issues raised by the SA Government's Advisory Committee on Future Electricity Generating Options [FEAC], mostly dealing with aspects of assuring the status of the coal reserves at Sedan; later, during 1985-86, plans were made to upgrade the geological information on coal quality and seam definition, in order to support joint venture negotiations with ETSA that were in part aimed at funding a trial mining phase. To this end, a 90-hole infill drilling programme for 5202 m, including 365 m of coring in 18 holes, was performed to satisfy remaining deficiencies in geological data needed for grid-based computer modelling of measured in situ coal resources and their grade distribution. This work resulted in an ~10% downwards revision of the total reserves, made mostly to the indicated category (previously 107.2 Mt).