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III IIIIIIIIIIIIIIII B99 STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Deparlmenl of Natural ReSOUrCeS 1 } I l Sherman St., Roam 215 Denver, Colorado HO203 f hone (30i1 Nbb-3567 FAn 11(1 it tli~ tl106 May 2l, 1998 ~'.. ~~~ DEPARTMENT OF NATURAL RESOURCES Ror Romrr To: H. Bruce Humphries cover^nr /tl lames 5. Lnchhead ~/ 4 Erecwi~r Duerlor From: James Dillie /~, Michael B. Loop Divivon Direanr Re: Reported Out-of-Containment Cyanide Spills, San Luis Project, M-88-112 Per your request, following is a brief description of all the reported out-of-containment cyanide spills a[ the San Luis Project: 1. October 1, 1993 - a leak (treated and recycled process water) occurred at a join~.ed pipe between the process water storage tank and the tailings impoundment in an unlined V ditch. It vas estimated that 3,000 gallons leaked out. The water flowed down the ditch to the tailings facility. Lab results showed .16 ppm total and WAD cyanide in the process water. The Board did not find a violation. However, BMRI was required to submit a permit revision (TR-17) to address the problem. The revision satisfied the Division's concerns regarding past, and possible future, spills in and around the process water pipeline. Also, as an additional precaution, BMRI submitted TR-20 to address possible: spills at the process water tank. This involved constructing a concrete containment structure around the tank. TR-20 was approved. 2. April 8, 1996 - a high pressure leak in a tailings disposal pipeline valve. The high pressure leak cut through the drainage layer, the 60-mil geomembrane and the 12 inch clay liner. The approximate water loss was 650 gallons and the estimated amount of cyanide leakage was 0.03 pounds. The operator was required to repair the valve and pipe; excavate all the contaminated soil and place it in the tailings facility; bring in fresh material (install in 4-6 inch lifts and compact); and replace the geomembrane (extrusion weld and vacuum test). The operator completed the corrective actions on 4-12-96. No violation was found. 3. November 25, 1996 -corroded holes in two slurry tanks leaked cyanide laced water into the sediments below the tanks. After cleaning the slurry tanks, the operator found several sizeable holes in [he bottom of two (out of eight) slurry tanks. The operator notified [he Division the day after discovering the holes. After inspecting the tanks, the Division decided to have the operator remove: the tank bottoms so the soils could be excavated and tested. Several soil samples were collected and tested at various depths. Cyanide was detected in the soil down to a depth of 6 feet. The Division instnlcted the operator to remove all the contaminated soil and place it in the tailings facility since this would be one of the corrective actions required by the Board. The operator excavated soils down to IS feet under each tank. Cyanide was not detected at the ]5 foot level. All [he contaminated soil was placed in the tailings facility and the pits underneath the tanks were backfilled with inert Santa Fe material. The Board did find a violation but, since the problem was already resolved, the Board only assessed a $100.00 civil penalty.