Gunite and groundwater issue. Any advice is appreciated!

[Dcpols]

Thank you to all of the contributors to this forum.

We are building an in ground pool and gunite was shot approximately 5 weeks ago. I am paying all subs directly and have an experienced project manager who builds dozens of pools managing the project.

We excavated, hit rock, and got the bigger hammer in here to break up rock. There was gravel put down, followed by steel and plumbing. Gunite was shot and then electric was installed followed by the tracks for the auto cover.

I have noticed water seeping in from the sides and one corner especially and called the gunite company out. I paid extra for 4,000psi concrete. There were a couple of small cracks on the pool floor as well which they believed at first to be stress cracks.

The gunite company came out yesterday and jackhammered into approximately 6 areas they identified and their resolution is to fill these areas with I believe it’s called leak stop. Their warranty for the gunite is for one year.

When jackhammering into one of the cracks a lot of water starting spewing out. The crack was near the bend of the pool as it goes deeper. They left a well point at the lowest part of the pool when they originally gunite and the spa also had a lot of water in it from the hydrostatic valve.

It seems as though there was a lot of ground water that was sort of stuck in the area of the middle of the pool. It has now all flowed out and I’ve pumped it out of the pool.

Questions I have include: What do I do about the groundwater now and in the future? I plan on installing a French drain towards the back of the pool where there is a slight hill upwards. I also plan on installing surface drains around the other areas of the pool.

But do I need to get an engineer involved to test the concrete? Any other ideas on if I should be asking the gunite company to do anymore or any other ideas on groundwater management now that the pool has been shot. I understand some folks have put in a pump at the bottom to help with groundwater issues but we did not. Should we do this now?

I appreciate any and all advice! I am putting up as many pictures as possible for your all’s review. Thanks again!

 

[zea3]

Hi, welcome to TFP! Did you have any issues with ground water when they were digging? Was there heavy rain shortly after the gunite was shot? A well point is a good way to manage ground water issues. Some of them are just a covered hole you can drop a pump in when needed, and I've seen some that have a pump with a float switch installed that come on and pump out ground water automatically. I'll ask for some more opinions for you. @jimmythegreek , @JamesW , @bdavis466

 

[Rich D]

Holy geysers batman.... Ledge can be a tricky and unpredictable. How far down did they have to hammer? I am a little confused why you would have that much pressure that high and it was not coming in the hydrostatic valve in the deep end. There must be a lot of pressure on that valve.

That crack where water is bubbling in is concerning. That would be right where I would expect a crack if the lower part of the pool was on ledge and the upper part settled a bit because it was placed on soil that was not properly prepared or not compacted correctly.

I personally would definitely get a engineer involved. Now is the time to take all the precautions you can, before you put many more thousands of dollars of finish work around in and around the pool.

It looks alot lower out by the street. Is there any chance you could put a gravity drain out that way so you would not have to pump the ground water?

Could you post any pics you have of the excavation?

Thanks, Rich..

 

[duraleigh]

The first thing I see in the pics is surface water (rain) draining into the pool. That same surface water is penetrating the sidewalls and streaking them. I would call that an absolute no-no and take steps immediately to correct it permanently.

Secondly, it is pretty unusual for rocky subsoil to have pooled groundwater. The rocks act as an avenue fdor the water to find loweer ground. Regardless, there has obviously been some concern about groundwater because of the well point being installed. Do you have a submersible pump down in that well point extracting water?

Last, I don't think (but don't know for sure) that psi of the concrete has much to do with it being waterproof.

 

[jimmythegreek]

4k psi concrete isnt waterproof the plaster waterproof the shell. Was water hit when digging? I agree the crack is in a spot that could be a settling crack. At the minimum the hydrostatic plugs should be opened amd pumps put it for now. All that water is rain water amd has to go somewhere. It would be easy enough to put vertical sump pits on either side and cover with lids on the deck. What does the project manager think of all this? He has experience?

 

[Jimrahbe]

D,

I had the same basic problem.. Drill a hole in the gunite and you had to hire the little Dutch guy with the big thumb... My pool builder tried all kinds of stuff, because the plaster people would not plaster until it was dry.

They basically had to remove the deck from two sides of the pool, dig down about 6 feet, lay in a 20' long x 6' deep, by 2' wide French drain on two sides of the pool.. Where the two French drains meet at one corner of the pool there is a 8 or 10' deep pit with a sump pump.. That pump has been running (cycling) 24/7 for the past 5 or 6 years.. It does not even shut off in the middle of the summer.

I guess what I'm trying to say is that the problem is not the gunite or any tiny crack.. Ground water under pressure will find a way into an empty pool.. You can't stop it.. You need to redirect it.

Thanks,

Jim R.

 

[Rich D]

I had the same basic problem.

Well that's unfortunate... Did you have a ledge issue or just that good Ole Texas hardpan?
Where do you pump all this water to ?

 

[Jimrahbe]

Rich,

Actually, I have easy to dig sandy loam.

Unknown to everyone, I think the pool blocks a small underground spring.

Well, it should be plumbed to the street to flow into the storm drain system. But I did not want water running down the street on a continual basis, so it could have accidentally been connected to the sewer..



Thanks,

Jim R.

 

[Rich D]

Unknown to everyone, I think the pool blocks a small underground spring.

Just a few hundred years ago that would have been a very desirable thing to have on your property..

Well, it should be plumbed to the street to flow into the storm drain system. But I did not want water running down the street on a continual basis, so it could have accidentally been connected to the sewer

yea.. They are getting very strict up here in the land of the oppressed, about keeping all the water from your property on your property. In a lot of towns We are now required to install very expensive infiltration systems to handle storm water. The do not want it going into the storm drainage system..

 

[jimmythegreek]

Same here. These underground drywall amd storage tanks fill fast in a big rain. Best to accidentally put the water somewhere else. Weekends are best for this work.

 

[Dcpols]

We figured out what the issue was. The gunite company screwed down the covers to the drains with the plugs in it and the well point was concreted on the bottom so all the pressure was building. The one in the spa was not bolted down so all the water was coming into the spa and the outside. It has been rectified and the gunite company is going to make repairs and warranty it for an additional several years. We also are installing a French drain in the back to divert groundwater and surface water out towards the street and I’m trying to avoid a sump pump but We may install a 3 foot pit that will slowly drain out on the other side of the trees.
Any advice on doing this versus day lighting the drain?

thank you for all the help.

 

[Rich D]

The gunite company screwed down the covers to the drains with the plugs in it and the well point was concreted on the bottom so all the pressure was building

Wow.. The absolute first things they should have checked..

So, it certainly sounds like the structural cracks were caused by floating. I thought most gunite pools came with a lifetime no leak guarantee? You might still want to get a outside engineers opinion of there repair methods. I am starting to loose confidence in any Professional that looked at that pool and did not think to check the main drain hydrostatic valve. In addition to having that much water coming into the pool and little to no water (assumed) coming out of a point well in a bed of stone under the pool.

I am not a engineer but common sense would tell me that before the cracks are repaired I would want the pool filled with water to "hopefully" ensure all parts are settled back into place.

If you do own past those trees to a elevation that is below the bottom of the pool I would strongly suggest a gravity drain be installed from the bottom of pool to a leach pit that has a grated cover. The cover should be at a elevation that is equel to or lower than bottom of the pool. This will allow any slow ground water to leach into the lower areas soil and if you do get a surge of surface water it will allow it to come out of the grate. This will hopefully avoid a constant running stream down to the street. Along with this drain run a additional pipe that can pick up any surface water drains you put in. It is always better to daylight a drain instead of relying on any type of pump. Powered outages usually come with heavy rain events when your drainage is needed most.

 

[duraleigh]

I would say "drain to daylight" in almost every case, including this one. Is there a reason why you cannot?