This article first appeared on GuruFocus.

BHP Group (NYSE:BHP), the world's biggest miner of copper, has received its first major environmental approval for the expansion of its Escondida copper mine in Chile, a move that could allow early-stage work tied to a broader investment program worth as much as $14.7 billion to begin. The approval from Chile's Antofagasta Environmental Assessment Commission covers sulfide leaching and electricity upgrades, according to a BHP spokesperson on Tuesday, with this initial phase expected to cost around $1.3 billion.

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This development may be important for investors because Escondida is the world's biggest copper mine and remains a key part of BHP's plan to roughly double annual copper output to more than 2 million tons globally by the mid-2030s. BHP owns 57.5% of Escondida, while Rio Tinto Group, a major global mining company with a 30% stake in the project, holds the next-largest position, and a consortium of Japanese companies owns the remainder.

The approval comes as BHP's Chilean copper operations are dealing with declining ore grades, which appears to be pushing the company to invest heavily to maintain current output levels. BHP estimates it will spend between $10.7 billion and $14.7 billion in Chile in the coming years, including a March application for a new concentrator plant at Escondida costing around $5.9 billion and a separate application last week to restart and expand the Cerro Colorado mine in northern Chile at a cost of $1.5 billion.