With the coal boom on the wane, mining companies want to escape the cost of rehabilitating their sites. But even if governments effectively restrain them, many of the huge voids in the landscape will never be filled in. The Australian coal industry is dotted with recent examples of major miners selling projects to smaller players at peppercorn prices, unloading both their rehabilitation liabilities and the reputational risks. Rio Tinto, which last year flagged the sale of its Blair Athol mine to the ill-fated Linc Energy, has emerged with a proposed deal to sell it for $1 to a debt-laden junior player called TerraCom, linked to a trio of former state…