What to do with groundwater that comes up when digging for pond

[Heruga]

So I spent a total of 4 hours digging a 7 ft diameter pond with a 32 in depth. And now I encounter groundwater which keeps rising but slowly. I have underlayment and liners and I’m worried that they will keep sinking after the water goes on top of it. Is there any solution to this or did I literally waste 4 hours of my time and energy?
Attached pic is halfway through the digging.

 

[JamieB]

that’s a problem! I’m inclined to see the silver lining, I’d be testing the water, see how it is, if it’s pond quality, I would be figuring out how to set up pipes to use that to constantly top off the pond. But, you may want to keep the rest of the hole above the water line, you can build up the sides either by building a berm of dirt, or reading the threads on above ground ponds for other ideas. If you do decide to see the silver lining as I did, be sure to set up something to control the water flow so you can turn it off if needed.

 

[Mmathis]

Keep the water level of the pond above ground level. To do this, the pond will have to be elevated. I did mine with a cinderblock collar, and the top edge of the pond was about 12” above ground — just enough to assure that water level was higher than ground level.

We have clay soil and a high water table. During construction, there were times when you could literally watch ground water seeping through the walls.

 

[Heruga]

I’m sorry but what is a silver lining? And what can I do with pipes being put underground?
Also below the rocks where my head shadow is, there is a drain just about level with the current depth of the pond. And I see the water in the drain sitting still.
I was also thinking of making this pond an above ground one but since this pond is specifically for my lotus and they need at least 30 in deep underground water for it not to freeze, wouldn’t the above ground factor allow the pond to be exposed to more cold and letting the water to freeze more easily? Also I kept adding more soil but the water kept rising and because it’s water, the surface never solidifies and whenever I try to step on it my foot sinks. I’m worried the same will happen to the pond liner. Or will the surface eventually be compact after dumping enough soil?

 

[Mmathis]

I believe that the pipes are intended to act like a French drain, redirecting excess ground water away from the pond. Many have had great success with this. My solution was to raise the water level of the pond above ground level. See my post above.

 

[Heruga]

Yes I responded to your previous post. Any advice on that?

 

[Lisak1]

You definitely need a firm foundation for your liner - putting it over wet ground wouldn't be a great idea. However, rather than sink into the hole, your liner will likely be lifted by the water pressure from underneath. This is called a "hippo" and isn't something you want to see in a pond.

A French drain is one idea - install a pipe to move the water away from under the pond underground. Another idea would be to install a sump pump that would pump water out of the hole as it fills up. Both of these require some engineering though so I'm definitely not the one to offer advice on how to achieve either one. @GBBUDD may pop in here with some construction advice.

"Silver lining" just means a benefit that comes from what appears initially to be a problem - "every cloud has a silver lining" is the saying. I'm not so sure about @JamieB idea though. Again an engineering problem that someone may be able to figure out, but I think I'd be looking for a long term solution that would keep the water from getting under the pond in the first place.

 

[GBBUDD]

@Mmathis is describing what we have all heard in the trade . But more of a stagnant setting . And that is head pressure. We have all dove to the bottom of the pool and felt the pressure on our ears. Thats head pressure so in The drawing provided raising the water level up above the ground table . "WATER LEVEL OF THE GROUND" BY RAISING YOUR PONDS WATER LEVEL.you are unballancing the pressures. Making your pond have more weight at the bottom of your pond then does the ground table. This means your ground table has to work extra hard to try and lift a heavier area due to the increased head pressure. We take advantage of this all the time in drilling deep cassons HOWEVER if you only raise the pond 6 " the difference is not great and if you hit a spring it can easily out balance your efforts with head pressure. ALL IS NOT LOST.
making a gravel area below the pond allowing water to move Under the liner is the best method covered with fabric and maybe even a few inches of sand. Place some pvc piping or they also have rigid flexible pipe made into like a 6 inch wide by an inch thick where four of these pipes are joined together. These prevents them from being crushed . The idea is like everything in nature and that is take the path of least resistance. Which is now your stone area bellow where the water will collect and as the head pressure starts to develope it finds the pipes and is pushed upwards and out. The pond having the extra weight and head pressure keeps the liner from lifting. I should add this gravel area is not a must have but if I had a water issue I wouldn't think of building further without it and the pipes.
Can stone on the bottom of the pond solve this problem you may ask. The answer is yes and no. This adds to the weight increases the head pressure but again if your ground table is substantial and or a underground stream then it may not. The empty pipe under the liner should win every time and allow the water up and out from under the liner.
Sorry for the long winded answer but it should answer everything as to why we get hippos.

 

[Heruga]

I’m not sure I want to hire someone to install pipes because it’s right next to a drain that collects water from the trench as you can see in the photo. My shadow is in between the hole and the drain.

I woke up this morning to find out that this is now a major problem. I can’t even think about creating my lotus pond anymore. I tried to go with the idea of a raised pond so I filled the hole back with some soil but the water kept rising and rising as I filled. That’s when I decided the pond is definitely not going to work at this spot so I started the process of completely backfilling the hole. I can’t even tamp the soil to compact it, I tried it with a tamper and my foot but basically Its an irreversible swamp in there now. Now I need to watch for flooding when a storm comes. Since the drain is right next to it, I guess what will happen from now on is whenever water fills up in the drain, it will fill up that hole and the water will runoff right back into the drain and the cycle will keep on going.

 

[GBBUDD]

Your picture shows a storm drain catch basin. This is definately a problem area for a pond. If the catch basin is your personal property . Then its up to you what to do with it moving it etc but just remember if you change your site and the water table in your neighbors changes too then it could become a legal battle. Could you build like a elevated koi pond where the storm drain is untouched and water can still get to it unobstructed? sure. But its going to cost a pretty penny
My advice to anyone who is not extremely handy and construction savvy is to look for another spot .

 

[JamieB]

Sorry, I had to not expand on my line of thought cause I had to go get ready for work. I see the silver lining in what looks like a cloud ( a problem) was n that if the water is pond safe, you now potentially have a way to top off the pond with out raising your water bill, or require chlorine neutralizers. The thought I had involves getting the water tested for the first step. Then, you would partially fill the hole with large round river rock, set up pipes so that the water will come up and out, possibly with a ball valve in there so you can prevent overflow or filling when you don’t want it. This would be a good area to t off the pipe so that the excess water can go to a French drain or away from the pond. After the rock and pipes are set up, you would then fill an appropriate amount with finer stuff like sand, the liner underlayment, the liner, fill the pond, etc. I’m no expert, so you might want to consult with one if that idea would even work, but it’s what I would try if I found that problem on land I own. Here my water table is 20+ ft deep, so as I don’t ever intend to have a pond that deep, it’s not an issue, but you now know you have a source of natural water which is free, and unless contaminated from something like an old land fill, or things like natural poison found with certain metals, radioactive materials, etc, you have lots of options on how to turn that into something nice. I don’t know where you live or how close the pond is to your house, but if it is close, I would recommend you do your research to find out about the water table in the area. If it’s well known to be high, chances are your house was built with that in mind. However, if it’s a natural spring, or high point of a natural aquifer, it could lead to other problems. Artisan wells are very popular out here, lovely cool sweet water with out ever being treated by a city. If you have enough water pressure, you could have one on land you own.

 

[JamieB]

Just saw your post about the storm drain. This may be a seasonal rise in water table or else it should already be well known. Really dims my original idea to just cloudy.
There are threads on building above ground ponds, and YouTube has folks that can show step by step, along its things like how to insulate them. Try to find a part of the yard that may be higher ground. As for filling in the hole, try adding rock and clay, then a layer of sand, then more dirt. Or a water loving plant such as a willow.

 

[Heruga]

I backfilled the the hole in 2 hours but the soil was still wobbly when I stepped on it, I guess it will stay swampy. Anyway I didn't want to give up on my lotus pond so after I finished backfilling I immediately started digging another hole for the pond. The hole is right behind the first hole I attempted. This time I only dug 24 in deep(other one was 32 in deep) and same diameter of 7x7ft. Thankfully no groundwater showed up this time. I hope this will work. It is supposed to rain Wednesday here so I'm gonna try to finish it before then but still so much more to do such as raking out all the rocks, cutting roots, and smoothing out the edges(not sure how necessary this is). With my work schedule this is gonna be a challenge but I'll try! I keep you guys updated.
By the way the pond itself will be 24 inches deep but going to add couple inches above. I didn't want to make a completely above ground pond because my lotuses would most likely freeze in the winter like that.

 

[JamieB]

If you bulk up the dirt you dig out around the outside walls you build, it will help insulate a bit.

 

[GBBUDD]

Heck it sounds like you might have clay in your soils if wobbly as you put it stick a lotus in that wobbly area. They Love wet clay type soils and if you keep it moist I bet you'd have all the success you desire