Radioactive?
Those are tailings from the Glory Hole Gold Mine. They mined for Gold, Silver, Lead and whatever minerals were found in the Central City area. Nothing was brought in from anywhere else.
The only radioactivity would be trace amounts from the Granite that was crushed to extract the ore. No more than any where else in the Mineral Belt Area.
The depot was covered and there is a photo of half covered in the book
Mining Gold to Mining Wallets Central City, Colorado 1859-1999 by Alan Granruth, page. 71. The photo is ca. 1930. By 1935 there is a literal mountain of tailings there.
The tailings were "remediated" not because of radioactivity but because of the possibility of silicosis caused by the fine tailings particles that became airborne every time the wind blew.
Yes, I still have a can of the tailings as well... but I can't read by it.
Rick