Help me fix my water level mistake

[Rashad]

I thought this was a big enough FU that it deserved its own thread and discussion to help others avoid it in the future. Here's my showcase in case seeing how it was built over time helps with any ideas. https://www.gardenpondforum.com/threads/new-mexico-wildlife-pond-in-progress.28703/

TLDR: I didn't account for water level rising when its flow is restricted or how thick liner and underlayment are, and built my spillway too high/bog walls too low. Help me decide the best way to fix it. Pictures at the bottom.

Long version:

I have a retaining wall elevated bog with a spillway back into the pond. The wall the spillway is in is stacked 2x6s held in place by garden bed blocks and reinforced with rebar driven into the ground. I cut about 2.5 inches down into the middle of the top wood piece to create the spillway, which is about 2.5-3 inches below the top of the liner at the lowest point of the bog. I test ran the system for a bit before adding too many rocks or filling it all the way up with gravel, and everything seemed fine, but since the entire pond wasn't full I could only run it in short bursts, add water to where the pump is, run it again etc. Upon nearing completion and testing everything out, if I run the pump at full speed it starts fine but since water flow over the spillway is restricted it raises the water level pretty significantly to the point that it begins to just barely drip out over the top of the bog at the lowest point in the back. It's well below the top of the retaining wall caps, but over the top of the liner that is folded under the caps.

Possible solutions I'm exploring:

1. Using some sort of sealant where the wall caps meet the liner. This would probably be the easiest solution, I'm just concerned it wouldn't last. Although it would be relatively easy to re-do as I know exactly where the low point is. Just not sure what product is best. Silicone? Spray flex-seal? Liquid rubber?

2. Living with lower flow to the bog. I do have a ball valve installed and if I slow down the flow to the bog everything works fine with the current setup and there are no leaks. The waterfall is a bit meh, but it adds to the dwell time. I would then add a tee and have a second outlet from the pump directly to the pond so I get a higher circulation rate and enough flow to make sure debris gets pulled into the intake bay.

3. The dreaded cutting of the liner. I could make a big horizontal cut in the liner and underlayment, fold it back, cut the spillway deeper/wider and then use some cover tape and some extra liner to go over the cut. Since the cut would be well above the water line of the pond and just under the waterfall I'm sure I could make this leak-free with a bit of work.

4. Redoing the top of the bog wall. This would involve knocking off the glued on wall caps from the retaining wall, repositioning the liner vertically instead of folded over the wall caps, and then either adding another layer of wall caps or just camouflaging the edge of the liner somehow. There's a bout 3 inches of liner folded over under the wall caps so there's plenty to work with.

Pics:

1. How the bog wall is constructed, overall picture of the bog

2. Water level in bog with pump off

3. Water level with pump on, ball valve partially closed, then ball valve fully open and it starts leaking a bit.

4. The not deep enough spillway which is basically a notch cut in the wood that's under the liner

 

[addy1]

. Redoing the top of the bog wall. This would involve knocking off the glued on wall caps from the retaining wall, repositioning the liner vertically instead of folded over the wall caps, and then either adding another layer of wall caps or just camouflaging the edge of the liner somehow. There's a bout 3 inches of liner folded over under the wall caps so there's plenty to work with.

My choice!

 

[combatwombat]

I would start w/ #4 (redo the wall and add freeboard to the bog) and see if that does the trick. You may need to aggressively manage the root system of your plants as well since I believe once they grow in that can also increase water level via back pressure.

If that wasn't enough, I'd move onto #2, adding a return jet somewhere in the main pond.

If you could do it over again, ideally, you would over-excavate your waterfall weir. If it ended up being too low, you could build it up over the liner w/ more rock and direct flow w/ waterfall foam.

 

[poconojoe]

I'm guessing it's all one liner and it would be too much work to remove the gravel to widen the spillway.
I wouldn't cut any part of the liner. That's trouble just waiting to happen.

So, I'll agree and choose raising the bog walls, that is if there's enough liner to do so.

Second choice would be add a wye to the pump outlet with a ball valve on each branch. One goes to the bog the other to another feature or just directly back to the pond. Now you'll be able to fine tune each valve.
I like the two valve method rather than just one valve which might put unnecessary restriction on the pump.

 

[Jhn]

Agree with everyone raise the bog wall, it is the simplest way to go. Adding another layer of wall caps to hide the liner would be the way I would do it. Usually you want the edges of the bog walls at least 6” higher if not more than the low point, I usually go around 12” higher with my bog, just because experience tells me the plants are going to restrict flow eventually when they take off. I would also put a y I’m so you can control how much water goes to the bog and to another return, as needed.

 

[Rashad]

Agree with everyone raise the bog wall, it is the simplest way to go. Adding another layer of wall caps to hide the liner would be the way I would do it. Usually you want the edges of the bog walls at least 6” higher if not more than the low point, I usually go around 12” higher with my bog, just because experience tells me the plants are going to restrict flow eventually when they take off. I would also put a y I’m so you can control how much water goes to the bog and to another return, as needed.

Thanks everyone! @addy1 maybe add a note about the height of bog walls in the bog building thread/guide? Maybe it’s in there and I just missed it?

 

[mrsclem]

Wish I had known this several years ago! My bog started overflowing so I chipped away at the chimney flue liner outflow. That worked for awhile. Ended up removing cap boards and adding a 2nd layer to raise the edges.

 

[addy1]

Thanks everyone! @addy1 maybe add a note about the height of bog walls in the bog building thread/guide? Maybe it’s in there and I just missed it?

I will take a look, have not looked at that thread in a while. I can add it to the beginning. I had to raise my walls about 2 years into having the bog.

 

[Lisak1]

When I was doing the finished edge on our bog I wasn't really happy with how it looked - walls were too high, too many rocks, just didn't feel "right". Well, I soon figured out that it was just fine and now you'd be lucky to even be able to see the edges. Sometimes we forget that things tend to settle, especially if you've disturbed the ground to a major extent.

 

[addy1]

Ok added this to the bog thread:

When building your bog walls, make the walls around 6 inches over the pea gravel level. As the plants grow, the roots grow, the water level will raise. You need the extra wall space to handle the rise in the water level. Two years into having my bog I had to raise the walls about 4 inches.

 

[poconojoe]

When I built mine, I made the walls quite high.
At first I thought it was too high, but now glad I did it that way.

 

[combatwombat]

@Rashad: If you can widen your waterfall weir coming out of the bog, that will also lower the height of standing water in the bog. Might be easiest to try that first?

 

[poconojoe]

@Rashad: If you can widen your waterfall weir coming out of the bog, that will also lower the height of standing water in the bog. Might be easiest to try that first?

Unless I'm mistaken, the problem with that idea is that it's all one liner. The bog and pond are filled, so they can't get to the spillway area to widen it without taking it all apart.

 

[combatwombat]

Unless I'm mistaken, the problem with that idea is that it's all one liner. The bog and pond are filled, so they can't get to the spillway area to widen it without taking it all apart.

Yeah, @Rashad said it's all one liner, but I can't tell how the relationship between the framing boulders and the liner lay at the spillway. If the framing boulders can be moved out and the width of the weir increased, that could do the trick. Not sure if it's feasible or not.

 

[poconojoe]

Yeah, @Rashad said it's all one liner, but I can't tell how the relationship between the framing boulders and the liner lay at the spillway. If the framing boulders can be moved out and the width of the weir increased, that could do the trick. Not sure if it's feasible or not.

Yep, that's the first thing I thought. Simply widen the spillway. But I don't think it's possible at this point.
If there's enough liner, raising the walls of the bog would be the next choice.