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February 5th, 2014 ~ Vol. 84 No. 5
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Looking Back - John Kinnear
The Lights on Grassy Mountain
Crowsnest Pass Herald Front Page
John Kinnear Photo
Drill rig with pipe and water truck in high mountain site.
It was interesting to study the front page Riversdale drilling setup picture that ran last week in the Herald. It looks like a fairly busy place up there on the top of Grassy with lighting plants, trailers, a drill rig with pipe rack and cyclone, a water tank, a small loader and even a snow cat parked off to the side.

Seeing this high mountain setup brought back a lot of memories of earlier days at Line Creek Mine north of Sparwood where for some years I was involved in similar exploration work. I did notice also that there was a small tarp like enclosure around where the driller stands and that is no surprise. You have to know that drilling on top of Grassy Mountain in December with that dam west wind blowing has to be hell. Been there, done that.

What a lot of people don’t understand is exactly how most types of coal exploration work is carried out and why. Through the thirty years or so I spent at Line Creek I saw a lot of exploration done usually with what is referred to as a reverse circulation rig. These drill rigs generally come with their own separate pipe truck and require a fair bit of space to get set up parallel to each other for drilling. It usually is preferable to set up perpendicular to the trend of the coal seam so that you get a relatively accurate idea of thickness when you finally penetrate it.

Reverse circulation rigs use a pneumatic reciprocating piston-driven hammer with a tungsten steel drill bit to literally pound their way down through the formations and coal seams. The chips generated by this bit are returned to the surface by blowing air down the inside of the drill rods and forcing them up a inner lining which is inside each rod (drill pipe). So essentially, the drill pipes are double walled. The cuttings are diverted at surface through a small cyclone and can be collected as they come out the bottom of the cyclone. The driller usually recognizes when he is coming into a coal seam as the water and cutting returns out of the cyclone turn black.

This type of drilling requires a lot of air pressure especially if the drill is going deep and runs into large volumes of ground water at depth. Sometimes the drill literally “waters out”, that is to say the drill compressor cannot supply enough air to run the hammer bit and push all the water and cuttings out at the same time. Drilling usually comes to a standstill then. If the particular drill hole specs require that the hole must go deeper than they already are when watered out the driller will be asked to pull out all the drill steel out (trip) and change from a hammer bit to what is called a rock bit. These bits are more recognizable to the average person, usually having three cutting cones that turn and cut in their own as the drill pipe is rotated and don’t require the air pressure that drives the hammer bit.

I remember well the driller’s facial expression and the cursing that followed when you as the geologist or technician overseeing the hole had to inform them that they had to put on a rock bit and go deeper. It meant tripping all the pipe out of the hole and back in again which can be a royal pain and hours of hard work. I had occasion to use a small mountain track drill for some programs at Line Creek that allowed me to get into some very tight places without having to build a large pad on severe topography. In this case there was no pipe truck and consequently no mechanical pipe handler, just some poor drill helper who had to lift and stack every section of pipe out of the way by hand. And then reverse this process as the driller “tripped back in”.

In the case of Grassy Mountain it appears that they are using reverse circulation to get them to the coal seams and then coring the coal and sending the core out for analysis. Operations Manager Peter Murray tells me they will be doing fifteen reverse circulation holes and coring at seven of those sites and indications so far at that the coal is of a high standard. Murray says they are getting 98% recovery on their core which is important as a clean overall representative sample is needed to tell you exactly what that coal seam is like at that depth and location.

Analysis of the core is usually done for such elements as the coal’s coking quality, its sulphur and ash content and several other measurable characteristics that define a coking coal’s performance in steel making. The compilation of the past and present drilling programs at Grassy will undoubtedly provide Riversdale with a comprehensive database of quality information that they can use to map and verify the viability of the deposit.

No doubt there will be more drilling goes on up Grassy as they refine their design and quality information. Generally mining companies like to tighten up their drill hole spacing to the point where they are very comfortable with the geological interpretation of the coal seams. When one considers the depth that ultimate pits go to it is dam important that you are sure the coal is where it is and has the quality you will want as you expose it. Future Grassy drilling may also be conducted to core the rock zones in an around the design pit walls to assess the rock’s characteristics.

So if you happen to see lights way up on the top of Grassy Mountain and it is twenty below with a west wind blowing, be glad you are safe and warm at home cause up there, there is no place to hide.
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February 5th ~ Vol. 84 No. 5
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