Hope Mine was one of the first, and certainly the largest, whole-mine reclamation project using biochar. Hope Mine was formerly a silver mine and it's situated close to Aspen, Colorado.
The USFS took charge of it in 2003, and the grey rock taillings had no vegetation and posed a potential threat to Castle Creek, Aspen's water supply. With this project, there was no evidence of heavy metals leeching, but the the bare rock didn't support vegitation, and could potentially pose a threat to the aquifer.
the results are quoted:
The project proved to be incredibly successful. xx test plots were created to study different levels of biochar,compost, and mycorrhizal fungi mix. The preliminary year-one results showed: