The driller came out last week and drilled 3 200' holes for the loop system. The first went through solid rock all the way down. The other two hit water @ 140' which is about the static level for our well system. No problems with our drinking water, thank God. They are going to schedule the trenching to the house in the next week or so and once everything is inside, the main contractor will come in and install the heat pump. The driller mixed Bentonite in his fill but there is still water in the two holes. Should I be concerned about this or not? Will update as the project progresses. Thanks again to all for the help and guidance in selecting the proper system and what to look for.
The driller mixed bentonite in with his fill???? What did state in your contract? Was it supposed to grouted in place or not? He should not have mixed bentonite in with his fill, that will only plug the borehole up and not allow the fill to drop to the bottom and fill correctly. The correct way to grout a borehole is to shove the trekkie pie to the bottom of the bore (200') and grout from the bottom up with a bentonite mixture (slurry). If I am reading your post correctly he back filled with boreholes and just added some bentonite in with the backfill?
Once the hole was drilled, they sent down the loop pipe to the bottom, filling the pipe with water to add to the weight to get it all the way down. Once @ the bottom they started pushing the "slurry" back into the hole. I cannot recall if it was about half way up or exactly where but they started mixing the bentonite (50 lb bags) with the slop on the surface then sending it down the hole. Where they hit water the used a little more but the average was about 200 lbs. per hole except the last one where I believe they used about 400 lbs because the hole kept "burping" if that makes any sense. They did not seem too happy when they hit the water. Something I should worry about here?
Not my preferred method, but it may work if he filled the holle all the way back up. The grout is only there to have full contact to the earth for transferring heat. If you fill the bore completely is should have the same effect. We drill the bore and insert a grout pipe down hole with the loop and grout from the bottom up, flushing the bore of all the water and drilling fluids as grout is being set into place. You Could ask the driller if your suspecting something is wrong.
Calladrilling, I was out there for the entire drill process. They did not have anything other than the loop pipe down the hole but it did go all the way to the bottom. Once inserted they started sending the slurry or whatever the material that was drilled out back down the hole but mixed bentonite in the last 100 feet or so. With the other 2 holes there was no way they could have removed all the water as they hit water about 140' down and I don't think they ever fully got out of it. I have some pics and will go over them with the heating/cooling contractor when I see him. They cannot do the trenching to the house at the moment as we're expecting about 4 days of on/off rains and they don't want to tear up any more of the yard then necessary. Thanks for the input.
Grout, loops and boreholes, It is not rocket science. Depending on the state and county in which you reside the requirements for grouting a borehole vary wildly. The IGSHPA rules say something to the effect that the boreholes should be filled from bottom to top to ensure a thermal link between the earth and the loop. This is most effeciently accomplished with bentonite grout. Many drillers are not efficient and if the state you live in says "back fill with cuttings" then everything is fine. If the state you live in says something different than you may have concern for the legality of the borehole, but prolly not the performance. The best loops in terms of performance are surrounded by moving groundwater. The worst are dangling dry in a rock bore with air around them. There is a lot of room here for in betweens and other things that are all dependant on the state regs were you live and your driller works. Hope this helps Eric
Waterpirate is 100% correct. Loops in contact with ground water from an aquifer are the best performers. Grouting boreholes does vary from state to state, and it may not cause a problem at all in your situaution that's why I am suggesting you talk to your driller and ask hm what his opinion is. I do not know the formations he drilled through or set the loop into. I am not saying what he did was wrong, just saying how we do our borehole backfilling ( code in NJ).
Eric & Calladriller, Thanks to both of you for making things a little more understandable. Considering the first hole was a dry hole (no water) and how they filled that one from the bottom up and then the other 2 holes striking water, I think I'm OK. It took a while for the guys to get the dry hole filled with the slurry. The wet ones took a while longer, especially the third one which kept "burping". I never thought they would get that one filled but eventually it did fill up. All holes settled somewhat and had to be filled a little more but the fill is now about 1 foot below the surface with water above that to ground level. Eventually they have to bring in a backhoe and trench the lines up to the house. The trench will be about 3 1/2 feet below the surface so I would guess everything will be fine. I'll be posting more once things dry out here and they get back to getting the lines in the ground. Thanks again.
