Piles of mine waste that loom above the historic Colorado mountain town of Leadville are a reminder of the city’s boom days. Now a company wants to “remine” some of the waste piles to squeeze more gold out of them. The waste would be trucked to a nearby mill, crushed to powder and bathed in cyanide to extract trace amounts of precious metals. Backers say the Leadville proposal would speed cleanup work that’s languished. Yet for some residents and officials, reviving the city’s depressed mining industry harkens to a polluted past, when the Arkansas River ran red with waste from Leadville’s mines.