Large concrete pond Re-Hab

[reefvet]

Hi guys,
Been around the forum reading for a few months and figure it's time to post my pond and situation for suggestions and thoughts.
We moved into a home this January that had a large concrete koi pond already constructed.....(Actually one of the main reasons we loved the property!). Built by a guy who pays attention to structural and design details pretty well, for when he built it, I think around 15 years ago. But ever since the house was under contract I've been dreaming of how to make it "mine". It's not 100% my style, but it's pretty nice, so I'm looking for ways to alter, add or change aspects of it without starting completely over.

I would say I am a pond enthusiast of medium knowledge. I actually constructed around a dozen liner ponds back in the early 2000's and had a large one myself, but as life and location changed the pond possibility never presented itself well until this new house/property. My area of knowledge lies more seriously in reef aquariums as I set up and maintained a 1000g reef aquarium with a separate filter room in a previous home for around 8 years. Now my circumstances see me returning to the great outdoors and inheriting a rather nice koi pond. I know it would have been nice to start from scratch, but life is what it is and this is my current starting point. The previous owner indicated it held around 80,000 gallons by his guesstimate, which I'll use until spring cleanup and official remeasure.

Here are pics of the pond I took this afternoon:

- The first photo is of the "main" pond area and is approximately 35x25 at it's widest. Reportedly it is around 4.5 ft deep in the middle (haven't jumped in yet to verify.... ) with a few gently sloped sides a few more steep sides. The rock "wall" on the opposite side is a large water fall coming out of the top "filter" pond. Tis pond is around 12x8 and filled with three sizes of matala mat which serves as the majority of filtration for the pond. The majority of water spills out the front with around 10% out the right hand side into a smaller 6x5 shallower pond that then cascades down into the pond. You might be able to notice a few smaller pools up against the waterfall wall that catch and hold some water for plants, but no fish.
Attachment 606793
-The second photo shows the "stream" that connects to the circular "island" pond. It's around 10'long and 3' wide or so, pretty shallow at 18-24 inches, home to some of the smaller baby koi.
Attachment 606794
- The third photo is of the island pond, basically a doughnut around a central island. The width of this lazy river is 6-9 feet or so and is 5' deep over by the gazebo. Again, sloped sides, but quite steep- really no place for a heron to land in the water proper. The gazebo houses the mechanicals which is basically the pumps (two- I need to get brand/sizes for you) and effectively a vortex settling chamber in a tub around 10' wide by 8'tall, maybe a touch bigger.
Attachment 606795
Essentially the water flow is through 6 bottom drains, 3 in the waterfall pond and 3 in the island pond. There were 3 more in the island pond but had to be capped with blasting for new construction next door cracked the pipes.......
The bottom drains feed the settling chamber and from there it is pumped to the bottom of the top filter pond, through the masala and over the waterfall.
Residents at the moment are around 30 koi in the 18-28" range and untold hundreds of baby koi.

The pond is concrete/xypex and I can't remember exactly how thick it was (but I can get details from previous owner when relevant). Apparently every few years there are a few spots that get some flexseal, but hasn't been anything major.

Those are the basics, let me know the more details you'd like as we go along this thread and I'll track them down.

Essentially, I have a few thoughts and priorities to address this spring as follows:
1. Evaluate filtration. I'm not convinced there is really enough filtration despite the thousands of dollars of masala mat present in the filter pond and would like to think through the best way to add space efficient filtration.

2. No skimming on the pond. All water returned occurs through bottom drains- as there is quite a bit of leaf fall around I'd love to incorporate some type of effective surface skimming if possible. How do you add an effective skimmer to a concrete pond, or don't you?

3. While I like much of the design of the pond layout, I'm not a fan of the large waterfall. I much prefer a meandering stream with 4 or 5 drops in it and would like to explore the possibility of re-routing flow out of the filter pond through the side pond on down the small hill into the main pond. Was thinking of maybe lining the filter pond and continuing down the hill until it spills into the main pond with the liner, but not sure that's the best scenario.

4. I'd like to consider options to seriously leakproof this thing as there is currently a leak in the main pond that I end up trickling water into 4 days out of the week to refill appropriately. I'm located in the Kansas City area, so freeze thaw is an issue. The previous owner is in town and excited about my taking his "baby" and will be assisting with leak location and repair this spring, but I can't help but wonder if a massive coating of something might be worth it.

5. One of my last dreams, and likely the most impossible, would be to somehow raise the water level in the main pond effectively adding 2-3 feet of depth and allowing for feeding of the fish at maybe waist level where they could swim up to the edge. This seems a pipe dream, but thought I'd put it in here.

6. Really open to any and all other suggestions. Keep in mind that I didn't build this pond, so I won't be offended if you think something was done poorly or incorrectly, but no need to tear the original builder apart- it was a while ago-- I just want to address issues as best I can. The only suggestions I would like to keep out of this thread are the ones saying I shouldn't have bought someone else's leaking concrete pond!! Just not helpful.

So with that I turn this over to your thoughts and comments and plan on providing photos as a I go and photos of anything else you might deem noteworthy or helpful. I know it would be nice if I had had a chance to drain the filter pond,etc to really see the system, but that will come as spring arrives!

[*Ci*]

Wow, what a project. I’m not sure how much advise I have, but a couple questions.
I’m confused by the area circled in the photo ... where is the concrete or liner in this area? This looks like a dirt slope right into the pond.
Also, did the previous owner completely empty and refill the whole pond every few years to apply the flexseal? This sounds like a major issue. If you were going to do the same in order to reseal the entire pond, then many options become available for fixing bottom drains, adding skimmers, returns etc.

[batman]

It's a pleasing layout but causes sharp pains in my back and wallet when viewing.

Good Luck on the project.

[reefvet]

Hi Ci,
I don't see a photo in your post, but the answer would be the same wherever was circled! The entire pond is concrete, no liner anywhere and no dirt slope that reaches the water- Any appearance of a dirt slope is either concrete with rocks embedded in the surface, creeping plants covering the edge or has a concrete edge that extends at least 4" above the highest water level.
Yes, he would drain any areas needing sealing, at least to the leaking point, and then refill. If I were going to do a massive seal project, yes I would do the same. I already have temporary housing for the koi when needed.
So, yes whatever returns/skimmer options could be added would be done at that time. As I'm familiar with liner ponds I would have no problem retrofitting those types, but concrete is a new beast to me and I was of the impression that you really can't get a good bond/seal between new concrete and old concrete that would make any changes challenging. True?

[reefvet]

Thanks Batman,
As for the back... I am getting to the point where that becomes an issue every now and again! Or at least doesn't go away in a few hours like it used to! But I LOVE outdoor projects, so slow and steady wins eventually........ I hope. As for the wallet, I had planned on a koi pond install when we found our new property, so I do have some reserve to put into the improvements desired. After evaluating the current pond as it is, well... it's functioning with healthy fish, so I don't have to tackle all of the projects at once and can prioritize as I go. Not that that makes it LESS expensive, just somewhat planned for and leisurely.

[*Ci*]

Hmmm, I had the photo attached, but anyway, this area totally looked like dirt... but maybe it’s overhanging plants? Could it be that the “leaks” are actually plant matter wicking up water? I’ve had that happen on small, lined lily ponds. Having this gradual slope can also allow soil, leaves and debris to wash into the pond easily.

[reefvet]

ah, yes, I see the photo now. Those are actually a creeping evergreen, there's actually quite a high concrete edge under them and interestingly enough that pond section doesn't leak at all! It's actually just the pond in the the first photo in the OP that leaks. That one holds water like a champ. No flex seal there this spring! But that is the low point of the entire pond chain. Essentially, the "main" pond in the first photo is around 6 inches above the stream that is about 2 inches above the pond area you reference in the photo.

[Grumpy]

Please describe more about the tall waterfall "filter". If the water is pumped from the "bottom" how deep is the water in the "filter". It looks like a very heavy concrete structure that you say is 12x8. Say it is similar to a 10 foot diameter pond 10 feet deep, plus the weight of concrete could be 9 to 10 tons. Settlement over time with that continuous weight compared to the lighter load of the pond may have created a crack along the section where they join. Even with the pond filled with fish some scrubbing with a brush along that wall of the pond may reveal the previous efforts to seal the leak. If you move the fish out of that pond and let it leak down, does the leak stop at some point? Have you tried to shut down the filter and pump it down to see if that tank is the one that is leaking?

Just some thoughts.

[reefvet]

Hi Grumpy,
So the top pond IS a leak culprit, and currently has some "bubbling" under previously sealed areas and will need to be addressed this spring, but it's not the main problem. The issue is with all water flow turned off, the "main" pond in photo 1 drops around an inch a day or so. I am currently letting it go as far as it can to locate the leak....maybe. Depends on how low it gets with all the fish in there currently. I had been trickling water into the pond as left by the previous owner and usually three days fills it and then a few days off drops the level. So currently, I"m not evaluating the "filter" pond as it's not running at the moment, so I think any settling from that would be at the waterfall location itself and not actually "in" the main pond. Hope that makes sense, thanks for your reply!

Sorry, I didn't answer your depth question. I believe it was mentioned it's 6' deep, but I can check on that.

[batman]

Pond has a large surface area. Even in cold months when not iced over the effect of sun, wind and humidy surface evaporation is a factor. 1 inch a day might not be unreasonable.

[reefvet]

Gulp! I hope not, but I understand your thought process there. The reason I suspect leak vs evaporation is that the island pond/doughnut pond has almost no water level drop and surface areas are very similar (maybe larger on island pond, I'd have to do the math).
But thanks for the idea.

Ci, you mentioned options for skimmer and drain additions. How would you accomplish those things on a drained concrete pond? My first obvious thought is some minor demo to break a spot in the side and install skimmers, but wouldn't the repour of concrete NOT seal at the joints with the old concrete? Am I left just using the concrete as a shell and installing a massive liner over the whole thing? I also considered polyurethane spray and reached out to a few places (not local unfortunately, but haven't heard back). Any leads on polyurethane contractors in the Kansas City area would be appreciated to explore pros and cons of that option.

[batman]

Dropping faster than adjacent pond indicates you're correct. When the weather gets nice and if you find a crack there are products where you drill holes in the crack and inject epoxy sealer. On basements it works wonders. More permanent than a surface repair.

[reefvet]

hmm, hadn't thought about using that type of material, interesting idea-- are all the products/compounds used for that application fish safe?

[batman]

Most likely safe after cure period. Best to contact mfg. Epoxy or expanding urethane available. I've seen a zoo using to repair an aquatic exibit.

[Grumpy]

Is there an old retaining wall between the "filter" tank and the upper pond? It would appear there is a wall that may have separated the two, but my concern about differential settlement remains. It would be best to move the fish in the upper pond and let it drain down slowly until it stops, which may be near the floor if settlement has been the issue. In Illinois this time of year it may not be good for epoxy injection, but that probably is your best bet. You are correct, it will be very difficult to chip out a section of the old pond if it is a thin skin shell with minimum reinforcement, and make a leak proof patch. If, however, as you suggested the original builder was "a guy who pays attention to structural and design details pretty well" and the pond liner is structurally reinforced, a patch may be possible using a special mix and proper preparations.
Really you won't know what solutions you have available until you know more about where the water is going.

Are you sure the blasting nearby only effected the piping in the lower pond? That comment is really confusing. Usually only ground movement would be breaking bottom drain piping... I think. If that is so, why are you sure it only effected the bottom pond drains?

[reefvet]

Thanks Grumpy,
Yes the blasting thing is a bit odd, but apparently a subdivision behind our property was being constructed and they ran into a ton of rock and had to do some "blasting". As I wasn't there at the time all I have to go on is what I was told....... Which was that no other problems were noted at the time, but if it "cracked/broke" one of the bottom drain systems, it certainly holds that it could have at least weakened/shifted the ground around the concrete shell and be leading to problems now. That occurrence was over 5 years ago and didn't seem to cause other major problems at the time.
I realize a lot of this is being taken on faith from the seller, but all I can say at this point is he has been very helpful with every question I've had since purchasing. He actually only moved about a half mile away and is over occasionally to offer suggestions and ideas. He seems genuinely interested in helping. I'm also "holding" some of his nicer fish for him until he is able to contract someone to put in a much smaller backyard pond where he moved to (downsized as he's older), so he sort of has a vested interest in keeping things going well.

Currently letting the main pond drain as much as possible, so we can see how low the leak is.

I guess the question then becomes, if we assume worst case scenario, and the whole pond needs to be waterproofed, what is my best option? (And by best, I recognize there is cost vs longevity vs effectiveness)
Are these my only options:
1. Liner over the concrete
2. polyurea spray application
3. liquid rubber coating product

[batman]

All flexible coatings for concrete including polyurea can be iffy if you have seasonal ground water pressure pushing in. Many
failures posted and most either wasn't applied correctly or the effect of outside seasonal water pushing in not considered. Often water gets under and where the sun can hit causes vapor expansion pockets also. Polyureaa much better reputation sticking vs liquid rubber products but $$$$$.

[reefvet]

Hadn't heard of the ground water issue, but it makes sense. I don't believe that I have that problem but then again, not sure how I'd tell on a concrete pond.
I think I may have hit the leak level over the last 24 hours. I should have been marking it, but was eyeballing a marker. I'll let it sit for a few more days to be sure than do the best cold-weather examination possible.

Over the last few days I've been looking at constructing a DIY in-pond skimmer. This would obviously avoid the concrete issue, I'm out of luck putting one in the "main' pond, no place to hide it really, but there are several places in the island pond portion I could tuck it under a bridge or deck. I could probably use more than one, but concealment is a bit of an issue.

Also considering running some water out of the "filter" pond and putting some in ground filter boxes on the slope behind it that would be gravity fed, essentially adding more filtration without adding any electricity.

[Grumpy]

Just a reminder, the leak could be a crack in the liner, or a broken pipe.

Once the pond level has stopped going down, it is possible the leak is at the elevation of the pond water with a crack somewhere in the concrete pond liner. But it also could be at that same elevation at a cracked piece of a bottom drain pipe buried either under the liner or outside of the pond depending upon the slope of the buried bottom drain pipe.

If the cracked liner isn't found, you could plug all the drains in the pond and add water to the pond. If the water level is stable, you can test one drain at a time by removing one plug at at time, waiting to see if the level remains steady, until you start losing water again. Lets all hope it is a broken drain line.

[reefvet]

Thanks for the insight and reminder, Grumpy. I'll be sure to evaluate the pipe as well.