1985-01-24_REVISION - M1983052 (5)

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• pH is reduced to 7 . 0 prior to releasing the samples from the laboratory into the lab disposal site. Marathon ' s pilot plant is an experimental gravity concentration facility used to process bulk samples of crude ore to obtain a heavy mineral , gold bearing concentrate. No hazardous chemicals or additives are used in the plant . Bulk samples are taken in the field , screened and concentrated in the pilot plant, and sent to the laboratory for treatment to obtain analytical data . Twice a month or so, 750 pounds of concentrates produced in the pilot plant are cyanided in the laboratory to obtain assay verification of the gold content. This treatment results in the actual production of small amounts of gold . The techniques used to handle and treat these large samples are essentially the same as described above for the smaller samples. The only significant difference is that cyanide solutions are not disposed of but rather are stored in the laboratory as either pregnant or barren solution for gold recovery or reuse in additional concentrate analysis and testing. When necessary to bleed small amounts of barren solution, the solution is pumped to the alkaline chlorination system for treatment and neutralizing prior to release into the lab disposal site. • No toxic material is disposed of in any manner. Cyanided ore pulps, when through with the alkaline chlorination, pH adjustment procedure, have a pH of 7 . 0 and contain only minor amounts of carbon and nitrogen as decomposition products of CN- destruction. After treatment and neutralization, the ore pulps and solutions are placed in the laboratory disposal site. One 100 pound sealed steel drum of sodium cyanide is stored in the laboratory for testing purposes . The drum is inspected prior to each withdrawal of reagent . The drum is stored in a ventilated, well lit, well drained area of the laboratory under the visual security of the assigned laboratory technician . When received , cyanide is closely inspected for indications of problems in manufacturer quality control or damage in transport. If for any reason the cyanide appears to be unac- ceptable, delivery is refused and the cyanide is returned to the vendor for disposal. Empty cyanide drums are triple rinsed and the rinse solutions used in the laboratory. The drums are then crushed and disposed of in a county approved landfill . Normal personnel safety practices are followed with regard to respirator and safety goggle usage , housekeeping , and basic chemical usage training. Spills in the laboratory are cleaned up using standard, acceptable, industry procedures • to minimize exposure to personnel and assure no threat to the environment. 4