Cyanide at the proposed Idaho Maryland Mine

Basic Facts about Cyanide use at IMM

Cyanide is a highly toxic, environmentally dangerous chemical used to process ores at mines.(1)   Emgold, wants to use cyanide at its proposed IM mine, near Wolf Creek - despite the fact that alternatives to cyanide are being used at similar mines.

Emgold plans to dispose of waste cyanide in processed mine rock and underground in the mine as fill.(2) This plan places drinking water and streams and rivers such as Wolf Creek at risk. A cyanide spill in 2000 in one of Europe's foremost fishing rivers led to concern around the world; cyanide bans in mining have been passed in Montana, the Czech Republic, and parts of Wisconsin. (1)

Extremely small amounts of cyanide are deadly to fish. The federal standard for aquatic life is 5 parts per billion. A mine waste spill into Wolf Creek or via leaching into the SF Bay Delta could be catastrophic to fish and other wildlife.

Shipping cyanide to the proposed IM mine or other mines could lead to accidents. IMM proposes to ship 2.67 tons of cyanide to the mine each month. (2) Research has found at least 23 transportation-related spills of cyanide in the U.S. in the ten years ending in 1997. (1)

Cyanide spills and pollution from modern mines is not uncommon. At mines in Nevada and Arizona, over a four-year time span through the end of 2000, cyanide spilled twice and caused a major mine waste spill in 1997 that covered three quarters of a mile of Pinto Creek in Arizona and cost more than $30 million to clean up. (1) Problems with cyanide in mining are not only during the ore processing, which separates the metal from the ore, but also with the transportation of cyanide before the processing, and the storage of cyanide wastes after the processing.

Detailed Facts about Cyanide usage in mining

  • Vat leach procedures for using cyanide to recover gold can lead to long-term environmental impacts, including:
    • Unforeseen spills of concentrated cyanide and other reagents
    • Seepage from the tailings
    • Toxicity to birds and other creatures when they come into contact with water that accumulates on the tailings
  • Higher concentrations of cyanide solutions are often used in vat-leach facilities, than heap leach facilities.
  • Regardless of what the mining industry says, or the label “zero discharge facility,” all liners of cyanide-treated tailings leak to some extent. This can be even more significant if liners are not installed correctly because the large machines that install them pass over the liners in this process and create even the smallest holes in the material.
  • Even when installed correctly, small amounts of leakage can produce significant impacts over long periods of time. Even once the mine closes, water management will be required in perpetuity
(“De-coding Cyanide: An Assessment of Gaps in Cyanide Regulation at Mines A Submission to the European Union and the United Nations Environmental Programme.” Dr. Robert E. Moran 22 February 2002. Sponsored by Hellenic Mining Watch, Ecotopia, CEE Bankwatch, FOE Europe, FOE Hungary (MTVSz) , FOE Czech Republic (Hnuti DUHA), Food First Information and Action Network (FIAN), MineWatch UK, and Mineral Policy Center. Retrieved at,12/2/08.)

  • “While much of the cyanide present in mining-related waters breaks down into largely harmless compounds, significant concentrations of other potentially toxic cyanide breakdown compounds may persist. These compounds present the most risk to sensitive freshwater fish species. Such compounds include many metal-cyanide complexes, cyanates, thiocyanates, cyanogens, cyanoges chloride, chloramines, together with ammonia, and nitrate. No regulatory standards exist for most of these potentially toxic constituents, with the exception of ammonia and nitrate.”
  • “Most state and federal agencies require mining-related water samples to be analyzed using either the free or WAD cyanide methods only. Neither method detects the majority of the cyanide-related compounds. A tailings or heap leach pad water sample can easily have a WAD cyanide concentration of less than 0.05 mg/L and still contain concentrations of cyanate, thiocyanate, or metal-cyanide complexes, for example, that are potentially toxic to fish.”
“Cyanide in Mining: Some Observations on the Chemical Toxicity and Analysis of Mining-Related Waters.” Robert E. Moran, Ph.D. Hydrogeology/Geochemistry, Golden, Colorado, U.S.A.  Moran paper on Cyanide


Description of Cyanide use at IMM direct from IMM documents

The following is taken from the IMM Initial Study, Sept 2007 p. 3-29. The combined tailings (from flotation and cyanide leaching) are then thickened to remove water. A portion of the tailings would be sent underground for use as backfill. The remaining portion of the tailings would be dewatered and sent to the ceramics plant to make tile products. The ultimate mining rate proposed is 2,400 STPD (standard tons per day), of which 800 to 1,200 STPD would be development rock. The gold processing plant would handle 2,400 STPD through the crushing and processing circuits. The ceramics plant would be capable of handling 1,200 STPD of feed, allowing for up to 1,200 STPD of material to be returned underground as backfill; however, some material could be sold as aggregate and trucked off-site.

Op cit p. 3-33. Sodium cyanide would be transported to the Idaho-Maryland site approximately once every three weeks in granular or powder form in one- to two-ton "super sacks" that are lined, unbreakable nylon sacks designed to be handled by forklifts.(Over a 20 year span that results in over 340 trips) As an alternative, a 24 percent to 32 percent sodium cyanide in water mixture may be used instead. This solution would be transported in a double-walled 4,000 gallon container trucks. Acids would be stored in a separate lined and bunded (sic) area to prevent formation of hydrogen cyanide (HCN) gas. Spillage from the respective storage areas would be directed to separate area sumps isolated and at a distance from each other and evacuated on a regular basis. Potential releases of hazardous materials stored at the site would be characterized to determine appropriate disposal requirements in accordance with California Health and Safety Code Chapter 6.95; in accordance with these regulations, the project applicant would prepare and implement a Hazardous Materials Business Plan.

(1) Background on Mining Bills - Senate Bill 160 Ban on Cyanide In All Wisconsin Mines
(2) IMM Initial Study, Sept 2007 p. 3-29

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