Installing Geothermal piping on frozen ground.

[mikeofBelAir]

I know I can't be the first person to ask....
I do geo-technical inspections, and generally we do not permit installation of pipe on frozen ground.
I have a project that has a large field of geo-thermal wells. The contractor has to connect them all. He excavated the trench for one of the pipe runs last Saturday, and today the ground is frozen--( 10 degree temps over night, and most of the day--high was 15).
Unlike most pipe work I have seen where the Contractor can excavate and install a length of pipe and backfill all in a day to avoid frost issue, this geo-thermal pipe must be completely installed, and filled with water, and pressure tested before backfilling. I understand that geo-thermal is installed all over the country, so surely someone has run into this before. What are the industry Standards for installing the horizontal runs in below-freezing temperature?

 

[EnergyProfessional]

you can backfill and compact with fresh (warm, non-frozen ) material and pressure-test with glycol. You also can build a heated tent. Generally backfill compaction is the problem, it is not so much a problem for the pipes.

We currently have the same situation and have the contractor pressure-test with air (since water freezes) and later in spring they pressure test entire system again with water and if any leak it is their responsibility. the interim pressure test you do now is more for the contractor sot hey are sure before they backfill. so at the contractor's choice, they may use air for now.

We have -15 to -20°f right now, so all the ground work ceased, there is no way of heating it and using warm backfill will freeze immediately. If you run into 10-15°F (and soon 20-25°F) you may have more options.

 

[Drazen]

it's forbidden.

anyhow on such temperatures most of plastic pipes become too rigid, fragile and prone to cracks, so ordinary laying can cause irreparable damage.

if you are supervising that, all you need to do is to get detailed installation instructions from plastic pipe manufacturer.

 

[mikeofBelAir]

Thanks for the replies.
I have done a pretty thorough internet search looking for Pipe manufacturer's specs on geothermal pipe installation. I could find NOTHING that permitted installation on frozen ground. The Contractor has not been able to provide any documentation that permits the practice, either. Based on your responses, and my search, I advised them that we could not approve the installation.
Than ks for the swift replies.

Michael

 

[chicopee]

mikeofBelAir, for curiosity sake are you installing plastic pipes?

 

[macmet]

I also frequently search online first for answers to questions like this, but in this case, if your websearch turns up nothing, I suggest calling the manufacturer. Most companies will have someone who could answer this question for you.

 

[Drazen]

macmet is right, you will not always find full documentation on internet, but you can always contact manufacturer's technical support.

 

[mikeofBelAir]

chicopee,
Yes, Plastic Pipe. Flying W Earthsource geothermal pipe to be precise.
No need for further investigation, the Engineer of Record accepted my concerns, and no pipe is being installed on frozen ground. All that is already in the ground, or rather, ON the bottom of the trench will be removed.
The Contractor maintained, as they always do, that "we do this all over the country, and no one has ever questioned it before". My reply,as always was, " I am sure that is true. However, on THIS site I am charged with enforcing these specs. If you can provide me with any written statement from the Engineer of Record that permits you to proceed, please do, and we can all get back to work." I have found that it never helps to let the emotions take over. I respond as evenly, and quietly as I can. It is true, if the EOR changes his specs, we can proceed; it makes no difference to me.

 

[EnergyProfessional]

I assume you work for the onwer... you should have the final say to even overrule the EOR. Some EOR may allow this and what then? I you feel you want to be more conservative than the EOR, be it.

Most EOR I work with will ler everything slide that would not pose an immediate failure that could be traced back to them.