ENFORCE37671 - Laserfiche WebLink

Home Browse Search

SOUTH DAKOTA I spoke with Tom Durkin of the South Dakota Dept. of Environment end Natural Resources, Exploration and Mining. The Homestake Mine in Lead 5.~. is a vat leach operation with tailing slimes deposited in a tailings pond $nd the sand portion of the tailing used for back-filling of underground worki~gs. WAD cyanide in the tailings slurry that exits the mill ranges from 50 to 200ppm. This slurry is piped to large tanks where the slimes are separate¢I form the sands. it is at this point that the cyanide concentrations are g~eatly reduced, simply due to the amount of time that the material spend in these tanks and the agitation of the material. As a result, cyanide concentrations (WAD) in the tailings pond range from 5 to 30ppm. While South Dakota has not set a standard for cyanide concentrati ne in a tailings pond, in a new permit application submitted in 1990 they required the operator to commit to less than SOppm (WAD) in the lined tailings pond. This permit application has been withdrawn since that time, but SOppm eems to be the standard policy in South Dakota at this time, and that number is based on wildlife exposure to the water in a tailings pond. Any discharge from the mine property (for example, poet-reclamation) would have to meet the drinking water standard for cyanide of .2ppm (WAD). OREGON I spoke with Gary Lynch of the Oregon Department of Geology, Mine Land Reclamation Division. Oregon ie in the process of developing leg elation that will address tailings pond cyanide levels, and Gary is going to s nd me copies of the two proposals (one backed by industry, one backed by envir nmentalieta) that are currently on the table. Oregon also recently completed rule making session that dealt with chemical process mining and will send me ~ copy of the new regulations. CONCLUSIONS At this time none of the states that I spoke with have any specific regulations dealing with tailings pond cyanide levels, although Oregon seems jto be close to coming up with some, and the documentation they are sending ehoul be interesting. The agencies in South Carolina and South Dakota are mainly concerned with the effect of cyanide in ponds on wildlife when t tailings pond is a zero discharge system, and the SOppm concentration lev 1 has been adopted as a matter of policy. in both S.D. and S.C. the drinki water standard ie required for any discharge.