Grassy Mountain Project

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Mine TypeOpen Pit
StatusInactive / Suspended
  • Coal (hard coking)
Mining Method
  • Truck & Shovel / Loader
Mine Life23 years (as of Jan 1, 2015)
ShapshotGrassy Mountain is on the site of an old mine that closed about five decades ago. The new, open-pit mine that Benga Mining Ltd. proposed for the land forecast production of 93 million tonnes of metallurgical coal over a 23-year life.

A joint federal-provincial regulatory panel rejected Benga’s Grassy Mountain application in 2021, finding that the project would likely result in significant adverse effects on the environment and on some First Nations, which outweighed any economic benefits.

Northback Holdings Corp., formerly Benga Mining Ltd., is a subsidiary of Australian mining giant Hancock Prospecting Pty Ltd. It is again eyeing a potential mine at Grassy Mountain, submitting applications to the Alberta Energy Regulator (AER) for a 105-day exploratory drilling program and a request for a water diversion.


Riversdale Resources Ltd. 100 % Indirect
Riversdale (through its wholly owned subsidiary, Benga Mining) completed the acquisition of the Crowsnest Pass Complex in South West Alberta, Canada on 29 August 2013.

Deposit type

  • Sedimentary


The Montane Subregion occurs on lower slopes and valley bottoms, and its upper boundary is the lower limit of the Subalpine Natural Subregion.  The Project is also located in the Rocky Mountain Foreland Thrust and Fold Belt, within a succession of generally west-dipping thrust faults and associated folds with predominantly west-dipping axial surfaces.  The Project lies between two major thrust faults, in an area of somewhat lesser disturbance.   The coal deposits of the Project area are typical of those for Inner Foothills and Rocky Mountain areas which have been subjected to a relatively high tectonic formation.  Fault offsets are common but fault- bounded plates generally retain normal stratigraphic thicknesses. 

Grassy Mountain coal in the Mist Mountain Formation outcrop occurs in a general north-south direction for a strike length of approximately seven (7) km.  The Mist Mountain Formation consists of 66 to 194 vertical metres of strata and is overlain by prominent, weather-resistant Blairmore conglomerate.  The strata have been strongly folded and faulted, resulting in sediments and coal zones repeated in parallel bands.  Coal deposits of this type are characterized by tight folds, some with steeply inclined or overturned limbs.  Fault offsets are common but fault-bounded plates
generally retain normal stratigraphic thicknesses.

Mining Methods


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Crushers and Mills

Milling equipment has not been reported.


The CHPP will consist of the raw coal, reject coal, and product coal material handling components and two coal processing plant modules.  The ROM raw coal from the open pit mine will be dumped from the mining trucks into the raw coal ROM bin.  The raw coal will then be fed into a feed breaker at the bottom of the ROM bin for initial primary sizing.  From there it is then fed onto a conveyor and into a secondary sizing station to ensure a top-size of 50 mm.  From the secondary sizing station the material is fed to one of two surge bins, each one positioned prior to the respective coal processing plant modules.  Each coal processing plant module will be contained within a housed area complete with bunded concrete floor.  HVAC systems will be included inside the shed to keep temperatures above freezing point.  Each coal processing plant module will have a 3.5 m wide access way for maintenance vehicles inside.  Maintenance will be assisted by an over-head travelling crane along the majority of the coal processing plant module length as well as monorails, which will also be installed above process equipment that require frequent change-outs.  The coal processing plants process water will be supplied from a reservoir from the mine infrastructure areas water raw water system.  A pump station will send water from the reservoir and pipe it to the coal processing plant modules for use in the processing as well as other minor maintenance requirements.  The coal processing plant process water system will be designed to fully recycle the process water, to minimize the amount of additional make-up water required from the reservoir.   Coal quality test work and process simulation modeling has shown the most efficient coal processing plant module design consists of a single stage dense medium cyclone (DMC) for processing coarse material, reflux classifiers for processing fine material, and two-stage flotation in a cleaner-scavenger  cell arrangement for processing  ultrafine material.  Product coal dewatering will be completed via vibrating and scroll centrifuges for coarse and fine material, respectively, and a hyperbaric disc filter for ultrafine material.



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Coal (hard coking) Mt 154
All production numbers are expressed as ROM coal.

Operational metrics

Annual production capacity 4 Mt of clean coal *
Stripping / waste ratio 9.4 *
* According to 2015 study.

Production Costs

Commodity production costs have not been reported.

Operating Costs

Total operating costs ($/t processed) CAD 93 *  CAD
* According to 2015 study.

Project Costs

MetricsUnitsLOM Total
Total CapEx $M CAD  ......  Subscribe

Heavy Mobile Equipment

Fleet data has not been reported.


Mine Management

Source Source
Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Sep 28, 2021
....................... Subscription required ....................... Subscription required Subscription required Sep 28, 2021


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