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Posts Tagged ‘Waste Rock’

bruce lake

Read today the news that the Brucejack Mine have been given an environmental assessment certificate by the British Columbia Ministry of the Environment.   The regulators say construction can begin once they are sure that discharges from water treatment plants will not harm the Unuk River.  Some of the tailings will go back underground; some will go to Brucejack Lake which is apparently “fishless.”  Most of the waste rock will go to the lake.

I read the following in the June 2014 Feasibility Study and Technical Report Update for Pretium Resource Inc. by Tetra Tech.

Approximately 3.5 Mt of waste rock and 8.7 Mt of tailings are anticipated to be deposited in Brucejack Lake over the projected 18-year mine life. Stringent discharge criteria (based on the Metal Mining Effluent Regulations (MMER)) state that the total suspended solids (TSS) concentrations in the outflow at Brucejack Creek must be less than 15 mg/L.

The tailings deposition system has been developed to minimize the concentration of fine suspended solids in the outflow to Brucejack Creek by discharging near the bottom of the lake (at 80 m depth) and under the accumulations of tailings solids.

On the other hand, waste rock with a wide range of particle sizes is to be deposited in the lake by surface dumping from causeways raising the possibility that fine granular material will be introduced to the surface layer of the lake and to the outflow.

Hydrodynamic modelling of Brucejack Lake was carried out by Lorax (2013) to examine the likelihood of the migration of tailings solids into lake surface waters. The results indicated that the potential for elevated TSS levels in surface waters was unlikely if the minimum particle diameter was greater than or equal to 5 µm.

However, it will be necessary to control the TSS concentrations at the outlet of Brucejack Lake to meet the MMER regulations. The current design basis for control of suspended solids includes the following:

  •  install one or more lines of turbidity curtains at the outlet of the lake to contain suspended solids
  • install a flow monitoring weir across Brucejack Creek downstream from the lake outlet to facilitate monitoring.

An allowance for site investigation and design of the outflow monitoring weir has been included in the capital cost estimate. As a contingency to the use of turbidity curtains, an outlet control structure was designed to allow storage and release of lake water in a controlled manner.

Review of the storage capacity versus lake level elevation for the outlet control structure indicates that flow from the lake could be stopped for a period ranging from several days (e.g. during freshet) to several tens of days (e.g. during the summer and early fall) depending upon runoff conditions in the lake catchment area.

If you have an idle weekend, you can spend plenty of time reading additional documents at this link.   For me it is off to the MET opera, the Tales of Hoffman, so I will say no more than this seems good news:  a BC mine advancing with a rational tailings and waste rock disposal system.  Good for them.  I hope they succeed.

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Last week I needed to brush up on stability analysis of waste rock dumps or embankments as they are sometimes called.  I went to the obvious sources: EduMine.  I opened the course Design  and Operation of Large Waste Dumps by Tim Eaton and Scott Broughton. In the section on Analysis they present a masterful description of the various failure modes and how to analyse them. They add this on probability of failure: (more…)

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DSCF1593

You remember Jill.  She is the philosophy major who is employed by an innovative mining company, MMC, to oversee risk management of the mining company’s geowaste facilities including the tailings, waste rock, and heap leach facilities. (more…)

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Introduction

Today I went to HR Block and had my taxes calculated.  It is a disaster: I owe lots and the total taxes I paid is more than the average Canadian salary.   I am seriously considering selling up and moving to Las Vegas.  And stopping working.  Why work to merely pay great sums to the government that squanders the money on frivolous pursuits?   I could blog away at no cost to anyone; to no income to me; and to no taxes to a far-distant gobbler and distributor of my earned income. (more…)

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The Wisconsin legislature has just posted a proposed new law on mining in the state.  The full document is available at this link.    At 191 pages it is not a short read; but it is a must-read.  And it is a fascinating read.  It is serious and sometimes frivolous.  Consider these sections that caught my eye on scanning the document: (more…)

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Today I was criticized for failing to clearly set out the project objectives.  Damn me, I know what we are setting out to do.  “But the rest of us do not,” was the reply. And so I wrote out the project objectives in deliberate detail.  And that set me writing the rest of this posting.  It may be entertaining; I hope it is informative; as least it should give you some idea of the issues and events involved in mine waste disposal engineering.  (more…)

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More on slimes dams, tailings impoundments, and processed geological materials residue deposits.  Here is an extract from a recent e-mail setting out the regulations that govern tailings dams in South Africa. (more…)

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