Rink Permafrost Removal - Forums?

[Query]

An local ice rink has a permafrost layer under the concrete slab.

I seek a rink operator's forum or equivalent, that I can join without paying money, on which to ask a question about an idea I have for removing the permafrost.

Background:

The (government-run) rink was built about 40 years ago as an refrigerated outdoor facility that stayed open for half the year. Later they enclosed the rink, and keep it open 10 months/year. This is near DC and two months should be enough to defrost the ground underneath the concrete slab, that acts as a foundation and contains the cooling pipes, to prevent frost heaves. But they stay open during the hottest part of the summer, to run a popular summer camp.

An engineering study found that there is a permafrost layer extending deep beneath the concrete slab. It would take a long time to defrost by simply turning off the rink, much longer than two months. Although the slab is said to be in very good condition for a 40 year old facility, and has no cracks, the study found it is likely to crack in 5-6 years, and that the best option was to replace the rink by a new facility on another site.

The study was performed by a company that builds rinks. In addition, the rangers at the park containing the current facility would like to use the rather nice building as their office, so it would not be surprising if they hinted that it was not essential to find the cheapest solution. (In government agencies and the government service industry, managers benefit from controlling as many employees and as large a budget as possible.) But I doubt there is fraud - I expect that the conclusions are correct, by prudent engineering standards, if the rink continues to operate in the current manner.

I have an idea. The cooling pipes must comprise an efficient heat exchanger, to freeze the ice above. So if the glycol is heated instead of cooled before being pumped into the pipes in the slab, during the two months the rink is closed, it should defrost the permafrost much more quickly than if they let it defrost passively. They would have to tap into the pipes before and after the compressor, and add a heater and a few valves.

Questions:

1. Does "glycol" means ethylene glycol, like in car radiators, and can it take fairly high temperatures? A manager said the glycol runs at 9 degrees F in normal operation.
2. How hot glycol can the the system safely take?
3. Does permafrost mean that ice has displaced the ground - in which case melting the ice would leave the slab unsupported, and it might collapse and crack? If so, is it practical and economical to pump in mud to support the slab? Or does permafrost just mean the ground water is frozen?
4. Is there anything else that could go wrong?
5. Has anyone tried this before? What were the results?

[FigureSpins]

I think a rink manager forum could give you specific answers to those questions better than I can.

I do know that our rink had to deal with a heave resulting from permafrost that extended well into the ground.  In our case, the rink was intended to be an indoor rink, but the original "warming floor" had failed.  (I think several pipes were blocked/collapsed.) 

It took a month to do the melt, fix the mechanical systems, repair the slab (cracks) and defrost the ground.  They used the summer heat and warm air with fans to accelerate the defrosting, but it probably could have used more time, so two months sounds like a good start.  The permafrost went deeper than they realized and the concrete was 3x thicker than expected.  Melting the permafrost could cause the slab to crack at a later date.  In our rink's case, they waited until the floor "went down to level" as the ground beneath the rink defrosted.  Then, they laid the new ice, but it's got thin spots and doesn't always dry evenly.  (Although our new dropped/insulated ceiling has resolved with the latter problem.)

The way permafrost was explained to me is that the ground naturally contains water, plus the water table rises/falls with natural precipation.  When the warming floor failed, the cold from the rink froze the ground underneath, which creates permafrost and in turn, causes heaves and slab cracks.  Anytime water melts, it finds its own level and runs off. 

Article: http://reporting1blog.wordpress.com/2009/12/11/2714/

[Query]

>I think a rink manager forum could give you specific answers to those questions better than I can.

Do you know of any such rink manager forums? I found rink operator associations on-line, but I'd have to pay to join.

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In the case of our rink, two months is not long enough to melt what has accumulated over the years. One unverified management guess is that it might take 9 month, by natural thermal diffusion alone. I just want to speed that up by heating it up through the cooling pipes.

I suppose a real answer for our specific rink should come from the company that did the engineering study, and I may suggest that to the appropriate government manager. But I'm sure they would charge real money to consider it. It would say a lot to know if someone else has tried this, and what the results were. E.g., did the concrete settle so unevenly that it cracked?

A published study said an Alaskan rink deliberately maintained a permafrost year-round instead of melting it, but DC is much warmer than Alaska...

[nicklaszlo]

My understanding is that the goal is to remove the ice rink but reuse the building.  If the building was constructed after the ice surface, I think it is unlikely the slab under the ice also supports the building, unless conversion to an indoor rink was part of the original plan.  Perhaps the concrete slab and circulation system should be removed?  If the ground beneath the ice sheet contains much ice at all, I would guess that if the ice melts the ice sheet would experience severe subsidence and require very expensive repairs.

If you really want to warm up the slab in a hurry, once the glycol is above the freezing temperature of water, use hot water to heat instead.  Water has twice the heat capacity and it is likely the building has a hot water heater or boiler that could be hooked up.  I don't know if you could use the same pumps.

My rink is the same age, but has always been indoors.  The government is currently planning its demolition, but it has problems in the non-ice areas as well.

[Kim to the Max]

Query,

I maybe wrong, but before the Pettit Center in Milwaukee was built, there was a rink at the State Fair grounds in the trade building. I seem to remember that all of the equipment and piping and everything is STILL there years later. Contact someone at the Pettit and they may be able to help you.