Rust-colored piles of mine waste and sun-bleached wooden derricks loom above the historic Colorado mountain town of Leadville — a legacy of gold and silver mines polluting the Arkansas River basin more than a century after the city’s boom days. Enter a fledgling company called CJK Milling that wants to “remine” some of the waste piles to squeeze more gold from ore discarded decades ago when it was less valuable. … The proposal comes amid surging global interest in re-processing waste containing discarded minerals that have grown more valuable over time and can now be more readily removed. … Backers say the Leadville proposal would speed cleanup work that’s taken decades under federal oversight with no foreseeable end. … Yet for some residents and officials, reviving the city’s depressed mining industry and stirring up waste piles harkens to a polluted past, when the Arkansas was harmful to fish and at times ran red with waste from Leadville’s mines.