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Scale of the proposed mine at Cochrane Hill Data gathered by Karen McKendry, Ecology Action Centre and Dale Archibald.

Information below is taken from the full project description, but numbers and calculations are calculated.

Scale of the proposed mine at Cochrane Hill (updated November 2019)

The Cochrane Hill gold mine project is currently proposed to operate from 2023 to 2029 (six years), and may employ up to 190 – 200 people (was to start in 2022, employ 220 people).

Size of the pit:

  • 950m long x 450m wide x 170m deep (at current mining scenario).
    Volume = 19,026,270 meters3 if calculated as a half ellipsoid/oval.

  • An Olympic-size swimming pool = 2,500m3.

  • Proposed open pit = 19,026,270 m3 / 2,500 m3 = 7,610 Olympic-sized swimming pools.

Amount of rock and ore removed:

  • At least 43.1 million tonnes of rock will be excavated from the pit, of which 1.1 Mt will be ore at 1.10 g/t of gold (pit could be expanded)

  • 22,086 tonnes per day of rock, 5,479 tpd ore

  • How much gold will be produced relative to tons of rock excavated?
    11.2 million tonnes x 1.1 g/tonne = 12,320kg of gold.
    1 gold bar = 12.4 kg, so 12,320kg = 994 gold bars for 43.1 million tonnes of rock.
    Currently, 1 gold bar = approx. $63,030 CAD, so 994 gold bars = $62,651,820.

Amount of tailings and other created at Cochrane Hill:

  • The tailings management facility (TMF) will hold at least 10.9 Mt of tailings solids, behind an embankment wall. The embankment will reach an ultimate elevation of approximately 150m.

  • A waste rock storage facility (WRSF) with the capacity to hold 11.6 million tons will also be built.

  • The waste rock pile will be between 10m and 40m above the existing ground surface.

  • There will also be a low-grade ore pile during the life of the project, up to 25m in height and 2.1 million tons in capacity.

Amount of blasting:

  • Blasting will occur 2 – 3 times per week.

  • Noise and vibration from blasting and equipment to be modelled.

Number of trucks:

  • 175 tons per day of gold concentrate to be transported away from the mine.

  • Trucks will make 6 return trips (12 trips) per day (1 truck every 2 hours) (estimate).

  • Trucks will travel 97km along Highway 7, through Sherbrooke and Sheet Harbour, then an additional 28km on public highways and roads (12.7km private road).

  • A 2.9km section of highway 7 is proposed to be moved. This move would bring the highway within 1 km of the St. Mary’s River’s edge.

Amount of water needed:

  • Start up will require 300,000m3 to 500,000 m3.

  • Daily raw water withdrawal is expected to be in the range of 50m3/day (= 50,000L/day).

  • A water withdrawal approval is needed for water withdrawals greater than 23,000L/day.

  • Water to be taken from Archibald Lake or the St. Mary’s River.

Power needed:

  • Upgrade needed to 4km of existing power line, plus 9km of additional line needed.

Acid rock drainage:

  • Acid rock drainage/ acid mine drainage occurs when sulphite minerals (e.g. pyrite) are brought to the surface and interact with water and oxygen. This reaction leads to sulfuric acid and metal oxides, which can then decrease pH (= more acidic) and release heavy metals (e.g. arsenic) in water bodies that receive runoff.


x 7610 pools

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