2012-02-28_REVISION - M1980244 (85)

Home Browse Search

A geomembrane liner, keyed to the VLF liner system, underlies the entire ADR Plant area, including the cyanide Offload and Storage Facility located adjacent to the ADR Plant building. The liner serves as tertiary containment for the concrete secondary containment facilities provided inside the plant and at the offload. The Offload and Storage Facility consists of a curbed, concrete loading apron for staging the delivery trucks /trailers carrying the ISO tanks. The concrete apron drains to the adjacent concrete containment area occupying the Cyanide Mix Tank and the Cyanide Storage Tank. The two tanks are set on solid concrete pads. Concrete floors, curbs, and containment walls provide secondary containment for all process tanks located inside the ADR Plant building. The containments have concrete floor sumps with dedicated, automated pumps to collect and remove cyanide solution and slurry spillage for return to the process circuits. The ADR Plant also has an overflow sump that reports to the VLF lined containment area. This sump drain always remains open. The concrete sump at the Offload and Storage Facility is pumped out manually using a submersible pump and a hose. CC &V has implemented a written procedure for pumping out the offload sump. The process tanks inside the ADR Plant are set on solid, concrete pads or are supported above the floor by steel structures. Process tanks located outside the ADR Plant building and offload containment, include the two barren solution tanks and the Pregnant Solution Distribution tank. The barren solution tanks are located outside, on the north side of the ADR Plant building, within the lined area. The tank foundations are solid, concrete pads. The Pregnant Solution Distribution Tank is located on the first lift of the Phase I VLF heap. During the June 2007 certification audit, containment design and as -built drawings were reviewed to confirm that secondary containment volumes are adequate to hold 110 percent of the largest tank volume within an individual containment area, plus solution in the associated service pipelines. Since CC &V did not add any process tanks inside the concrete containment areas (i.e., the offload or ADR Plant) subsequent to the 2007 certification audit, the adequacies of these individual containment volumes were not reconfirmed during this recertification audit. Even so, the overflow sump in the ADR Plant building links the concrete containment to the VLF containment, which provides an added factor of safety. The 8,000 - gallon Acid Mix Tank is located inside the ADR Plant and it shares a common containment with two other process tanks, the Acid Wash Tank and the Acid Neutralization Tank. During this onsite recertification audit, CC &V field- measured the containment and calculated its available volume while accounting for the volume occupied by the other tanks /foundations in the containment. Based on the measurements, it was determined that the containment has adequate capacity to contain the entire volume of the Acid Mix Tank, thereby maintaining segregation from other process areas within the plant. However, some concern exists that in a worst -case failure, residual cyanide in the Acid Wash Tank could react with the acid to create a potential HCN issue. CC &V Cresson Project Name of Mine September 22, 2010 Signature of Lead Auditor Date Page 18 of 36