Our water is pumped from a cavern in the ice. This cavern is created by circulating water from a "bell" (see the photo's) through pipework which, during its circulation path passes through a heat exchanger. The bell immersed in the cavern is therefore warm, which creates melt. This started many years ago as just some warm pipes on a depression in the ice, which gradually melted into a cavern. If repairs are required on the flow or return line in that system there is always a risk that pipework will freeze up before you are able to complete the repair and reinstate circulation. Worse still, if the circulation is interrupted for too long the cavern will freeze up.
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| The Melt Bell extracted from the cavern |
The former is exactly what happened. The latter is what we narrowly avoided.
On Monday morning we set out to repair a leaking join in the site services pipework (heavily insulated fusion welded polyethylene pipes). This is no easy task as first of all we have to cut away the steel sheathing that encases the expanding foam insulation. This is also encased in heat shrink. Then, once that is done you chip away at the insulation, taking great care not to let any of the foam drift away on the wind, as we go to great lengths to avoid even minimal pollution. Finally, you expose the pipe itself, establish where the leak is, and then replace the offending section. Here is often where the real drama begins, and Monday was no exception. The cause of the leak was a poorly fitted bend, which not only required replacing, but pipework also required realigning. Long story short, the job took us all day and by the time we had the water back on nature had done it's -20 degree business and frozen parts of our pipework.
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| Team Mawson Plumbing, Charlie and I. |
So as you could imagine, pipework encased in insulation does not make it easy to find the frozen part. Our first concern was that we had "dead headed" the pump by trying to circulate water and stressing the pump, so now we had concerns regarding the integrity of the pump. Also we began to worry that if we couldn't defrost the pipework in a timely fashion the cavern would begin to freeze and thereby freeze the bell and pump. The decision was made to remove the bell the next day, break down as much of the system as we could and begin to thaw things out. In the end we were forced to replace some of the pipework which we'd not been happy with anyway, which will be a good thing in the long run. The bell was transported to the workshop and rebuilt with a new pump and check valve. Finally on Friday after five days of toil melting frozen pipes and keeping them warm, the bell was lowered down into the cavern, pipes were reconnected and tested as we pumped water through in stages, and the water supply was reinstated to near normal function. As we were lowering the bell back into the cavern we could see that an ice crust had formed on the surface of the melt cavern. Another day or two we'd have been in big trouble.
All of this was of course made even harder and more time consuming by the fact that when we were working in the vicinity of the cavern, Charlie and I had to be harnessed up and attached to a belay, attended by two others. This is due to the fact that the cavern is a small hole in the ice that undermines the surface ice, drops seven meters to the water surface, and ten to the bottom. Extracting someone from there would not be easy if you did not already have a rope attached to them. I'd conservatively suggest you'd be dead by the time a rescue plan was implemented. All in all it was a very labour intensive job. There were six of us involved for five days, plus another two for a part of the last day.
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| The melt cavern, it looks a lot scarier when you are standing on a platform above it winching a water filled bell that weighs over 150kgs out of it..... |
In reality the weather saved our bacon. You see normally we have katabatic winds of around 30 knots to deal with every morning until around midday. Katabatic is the term used to describe to winds created by cold air flowing down off a mountain/hill/glacier which continue until the air space they are flowing into heats up and creates pressure of its own which forces the wind to stop, or reverse. Not only do we normally contend with winds, our weather is generally not stable. In fact it is more likely to be bad than good. Some how the weather patterns managed to provide us with five spectacular calm days, where the wind died by 9am each day, and in fact on the Wednesday and Thursday provided cloud cover which created two unseasonal -10 degree days.
Our potable water reserves total approximately 100,000 litres. On average the station consumes 2,000 litres per day. Enough for around seventy five to one hundred days if rationing was forced upon us. We also have another 300,000 litres in reserve for firefighting purposes (seems like overkill to me!!) so had we not been able to reinstate the supply we would have scraped through, but getting it going next summer when things have warmed up would have been a lengthy drawn out process as by then every part of the system would have been frozen solid.
So, all in all we achieved a good result after some creative thinking and problem solving. I guess that is one of the reasons the selection process for these positions are so thorough, enabling them to identify people who can overcome situations such as these when they arise. I have never considered myself as someone who was good at improvising to provide solutions and had concerns that I was going to be out of my depth down here.
Maybe they know me better than I know myself.
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| New Bell winched into place, mission accomplished..... Nearly. |
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| Team Belay, J.B. and Robbie. |
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| Herman Nelson, one of the big diesel fired heaters we used to defrost things. |
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