Commenting open: September 14, 2026 01:39PM MT - October 26, 2026 05:00PM MT.
DP-1840, New Mexico Copper Corporation; Copper Flat Mine, Stephen Crosby, Senior Vice President of Development, proposes to renew and modify the Discharge Permit for the discharge of up to 1,613,000 gallons per day of entrained process water in 38,000 tons of dry tailings to a lined dry stack tailing pile. The modification includes changing the tailing management process through construction of a lined dry stack tailing pile and associated infrastructure. Potential contaminants from this type of discharge include sulfate, nitrate, total dissolved solids, and metals. The facility is located at 85 Copper Rock Rd approximately 5 miles Northeast of Hillsboro, in Sections 30 and 31, Township 15 South, Range 6 West, Sections 25, 26, 35 and 36, Township 15 South, Range 7 West, and Section 6, Township 16 South, Range 6 West, Sierra County. Groundwater beneath the site is at a depth of approximately 7 to 156 feet and has a total dissolved solids concentration of approximately 317-868 milligrams per liter.
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