Ross Guenther: A better option for tailings
The Idaho-Maryland Mine could become a tremendous economic and environmentally safe asset for the people of Nevada County.
The August 2020 permit application by Rise Gold was done reasonably well for this potentially very profitable mine. However, as I mentioned to the Nevada County senior planner in August 2020, I am concerned about potential environmental impacts regarding the stability of the engineered fill placed on a slope above the town of Grass Valley.
This planned engineered fill is about half mill tailings (very fine mineral grains that flow easily when wet) and half development dump rock fragments (up to eight inches in diameter) that may not compact well with the tailings.
Also, the entire project could be accomplished more economically using only the Brunswick site without the 56-acre Centennial industrial site.
In recent years there have been many failures of tailings facilities in Canada, USA, Brazil and many other countries with engineered fill that have caused disasters costing hundreds of lives, buried towns, and caused billions of dollars in damage. Expert engineers had signed off on these failures.
A major concern of the existing engineered fill plan is the possibility of the tailings sliding down the slope to Wolf Creek and potentially burying downtown Grass Valley. Alternative tailings disposal will allow an environmentally safe option while only using the Brunswick industrial site without transferring any materials to the Centennial site.
One alternative would be a very high-cost venture of moving the tailings and development rock to another disposal site.
A better alternative would be to manufacture profitable high-quality, low-cost tile and many other green fireproof ceramic building products from the tailings.
The development rock could be profitably sold as aggregate. If the profitable alternative of manufacturing ceramics is taken, the entire project could be done on the Brunswick industrial site without hauling tailings and development rock to the Centennial site.
I have studied many aspects of the Idaho-Maryland tailings over the past 50 years, reviewing all the historical mine records, as well as interviewing several geologists and engineers who worked in the mine when it was producing.
I produced physical and computerized mine models showing the great economic potential the mine has. My teams had obtained a positive EIR and all related permits to safely dewater the Idaho-Maryland Mine, assuring clean water for residents, and to initiate underground development at the Brunswick site.
The permit work included our studies of hundreds of wells in the area, as well as groundwater and surface water runoff. I also worked extensively with the Idaho-Maryland historical mine tailings, as well as newer tailings samples made from our more recent drill cuttings.
I invented and patented equipment to process Idaho-Maryland tailings into ceramics. Later, with the help of other geologists and engineers, I patented compositions and methods for materials, including the Idaho-Maryland tailings, and produced ceramics in pilot plants on the Idaho-Maryland property, producing several tons of high-quality ceramics.
In testing the tailings material to produce ceramics (prior to firing), with optimal moisture content and very high compression, the compressed material was still quite fragile. Adding larger rock fragments of development rock made the material even more fragile.
When water is added to the raw dried compacted ceramic material, prior to heating, the material quickly rehydrates, causing liquefaction and becomes a fluid mixture that easily flows. The resulting mix of wet partially compressed tailings and development dump rock about 100 feet above Wolf Creek may result in a more unstable engineered fill than that suggested by Rise Gold at the Idaho-Maryland-Mine.
The 40-foot-high engineered fill”is planned to be built by Rise Gold at the Centennial site on a downward slope toward Wolf Creek to 100 feet below the top of the fill.
One should consider the gravity of the situation. After the tailings become saturated with rain and groundwater, the wet fluid tailings with liquefaction could act as a lubricant to the larger development rock and move millions of tons of waste material down to Wolf Creek and Highway 49, potentially covering much of the town of Grass Valley.
However, as stated, there are environmentally safe alternatives for the tailings disposal. That alternative would allow for the production of high-quality ceramics while removing only high-quality ceramics, along with valuable aggregate and gold, from the Brunswick site while not disturbing the Centennial site and reducing traffic.
Ross Guenther is the general manager of Ceramext LLC and lives in Penn Valley
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