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A Preliminary Assessment of the Proposal to Reopen Idaho-Maryland Mine

Grass Valley, CA – March 11, 2020

Rise Gold Corp’s application to re-open the Idaho-Maryland Mine is not yet deemed complete by Nevada County Planning Department, but a review of currently available documents provides a glimpse into the nature of the project and how it may impact our community.

The main mine access and processing facilities will be located at the 119 acre New Brunswick site located at the corner of Brunswick and East Bennett Roads. Operations will also utilize the 56 acre Centennial site on Idaho-Maryland Road west of Centennial Drive to dispose of mine waste.[1]

Mining will take place 24 hours a day, 7 days a week. About 1500 tons of waste rock and tailings will be removed from the mine daily. Of this, 500 tons per day will be mixed with cement to form a paste backfill and re-deposited into the mine. The remaining 1000 tons per day will be deposited at the Centennial site and at a 31 acre area along Brunswick Road just south of the processing facility and bounded by neighborhoods on Cedar Ridge Drive, Elk Lane, and Mink Court.

Waste rock and tailings from the mine will be transported by trucks making up to 100 round trips per day, 16 hours per day, 7 days per week. To get to the Centennial site, they will turn left onto Brunswick Road about 0.4 miles south of East Bennett Rd, pass through the intersection of East Bennett and Brunswick and turn left onto Whispering Pines Lane to reach Centennial Drive.

At the Centennial site, an area of 44 acres will be built up with “engineered fill” to depths of up to 70 feet, eventually forming a 37 acre graded surface that may be utilized for future development. Similarly, the mine waste dumped at the Brunswick Road site will eventually cover an area of 31 acres and be built up as much as 90 feet to form a 21 acre graded area for possible future industrial uses.

The trucks will be loaded with rock with a front-end loader. Hauling will take place 6:00 AM – 10:00 PM, 7 days a week. After the rock is dumped, it will be graded and compacted 7:00 AM – 3:30 PM, 7 days a week, using bulldozers, graders, and rolling compactors. [2] This activity will take place continuously for 11 years or until both build-up areas are maximized. After that, mine waste materials will have to be hauled out via Brunswick Road to Glenbrook Basin in order to access Hwy 49 for transport to sites not yet identified.

In terms of energy use, the permit application estimates a PG&E power net load of 6000 Kilowatts (KW). Planned diesel backup power generation capacity is 6000 KW. Electricity utilization is estimated at 42,757,000 Kilowatt-Hours (KWH) per year.[3] This is equivalent to the electric use of about 5000 houses.[4]

Full operations of the mine, including fuel for equipment, electricity, and other operational uses are estimated to produce around 9,000 metric tons of greenhouse gas emissions per year.[5]

Cement, explosives, diesel, and various other chemicals will be regularly transported to the site and stored. Cement will be mixed with tailings and pumped back underground and used to backfill mining voids. By one estimate, the backfill paste will use approximately 25 tons of cement daily. Explosives will include ANFO (Ammonium Nitrate and Fuel Oil), and Ammonium Nitrate Emulsion. Up to 28,000 lbs. of explosives will be stored onsite underground.[6] Diesel fuel storage will consist of a 30,000 gallon aboveground storage tank. A number of other chemicals will be utilized for processing the gold using the sulfide flotation system and other activities.

Industrial buildings covering 122,000 square feet are proposed for the New Brunswick site. Noteworthy among these would be the gold processing plant with dimensions of 425 feet by 70 feet and 65 feet high, and the shaft headframe building with a height of 165 feet. Running between these buildings will be a 365’ long enclosed conveyor system. Tailings will be stockpiled onsite while waiting for transport.

The application to re-operate the Idaho-Maryland mine states that 312 jobs would be created by the mine operations. Of those jobs, 242 jobs are specialized technical positions likely taken by people recruited from outside the area. The remaining jobs, truck transport of mine waste, and mineral processing, could provide 70 jobs for current local residents.

Content provided by Community Environmental Advocates Foundation (CEA Foundation)

[1] Project application documents may be viewed on the Nevada County website here. Unless noted, see Idaho-Maryland Mine Project Description, Nov 2019

[4] Average energy usage per CA residence = 667 KWH / month = ~8000 KWH / year. IMM will use equivalent to 42,757,000 / 8000 = 5344 houses.

[5] Ibid [3]


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