Pond Boss
Posted By: platon20 Best way to block outflow pipe from pond? - 02/25/20 10:29 PM
3 acre pond has a 5 foot diameter outflow pipe to control overflow.

I'd like to partially block the pipe to make the pond level stay higher.

What's the best way to do this? Sandbags? Moving dirt with wheelbarrows and dumping it in the bottom of the pipe?


I was leaning towards sandbags because I assuem soil or dirt would just wash away with erosion during rainstorms.
What kind of material is your pipe made of?
Try an inner tube. Inflate until tight. It might just work or use it as a dam while you figure out something more permanent. Just a minute of my thoughts!
It's round corrugated metal pipe like the one below:

A really large inner tube! Seriously, I'd be very hesitant to partially block that drain. It would strain the surrounding soils holding it in place.
Maybe you can pour concrete in the bottom half. That should bring up your water line and also reinforce the sidewall.
With no input as to whether or not it would be a good idea, you could stack Quikrete bags instead of sandbags or pouring concrete. They will conform to the curves (like sandbags) but will harden in place and (if you use enough depth) lock together fairly well to resist water pushing them.

Warning: Handling enough 60 pound Quikrete bags may lead to your introduction to the Double Hernia Robotic Surgeon. For me, 5 pallets of Quikrete were enough.
Posted By: RAH Re: Best way to block outflow pipe from pond? - 02/26/20 12:34 PM
Consider installing a stoplog structure (flashboard riser) on the inlet side of the culvert, perhaps with steel channel and removable boards. Commercially available ones in that size might break the bank, so you may want to build your own. The trick will be sealing things up, but expanding wood is pretty good at that. This kind of set up lets you control the water level by adding or removing boards.

http://wisconsinflowgate.com/

http://www.glasssteelinc.com/stoplogs.html

https://bid.houseauctioncompany.com/lot-...;current_page=0

https://www.briggsconcrete.com/
You can make it so the pipe is wherever you want your water line to be.

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I am not an expert but, if the pipe is that big, maybe it needs to be so water will not go over the road in a large rain event. With that in mind, you should keep what ever you are going to block the water with to have an opening with the same square footage as the pipe. So if you have a 5 foot pipe you should probably have a 5 foot box type riser. It should be sized by what your 100 year rain event is for your water shed is.
Originally Posted By: ShortCut
...Seriously, I'd be very hesitant to partially block that drain. It would strain the surrounding soils holding it in place.


That was my thought as well. Moving water is consistent, relentless, and predictable. The two erosion areas near the 5' pipe inlet would concern me, and I'd look at their impact on a partially blocked pipe that raises the water level immediately around it. Looks like eddy's may form there and create another potential problem.

Keep us in the loop, interesting scenario.
Posted By: esshup Re: Best way to block outflow pipe from pond? - 03/06/20 06:35 PM
I second the suggestion of a flashboard riser system. Using that you will still have full flow through the culvert pipe in case of a large rain event, but you can adjust the level of the pond as you wish.

Submerged version to use where beavers are present:
https://www.researchgate.net/figure...forested-welands-or-other_fig3_235985094

For where beavers aren't a problem, these are precast:
https://www.briggsconcrete.com/collections/concrete-flashboard-risers

Using the precast images, you probably can drain the pond down a bit, form one up on-site and pour in place. Use tongue and grooved boards for the "boards" but to span the 5' width, they might want to bow inward. If it was mine, I'd do a "pour on site" style, utilizing a brace in the center of reinforced concrete, so you have two boards side by side, each covering a 2 1/2' wide opening. You could use some thin foam on the bottom of the groove to help seal it and also along the back (downstream) side of the boards. Put a double eye hook (upstream and downstream) at the top center of each board that will give you a handle to put a hook in to pull them up to let water out if needed.
What about something along this line. Could be aiming up and buried also. I dont know how geometry works so not sure if the volume would be the same or not. Just brain storming here.

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Posted By: esshup Re: Best way to block outflow pipe from pond? - 03/06/20 07:16 PM
Originally Posted by RStringer
What about something along this line. Could be aiming up and buried also. I dont know how geometry works so not sure if the volume would be the same or not. Just brain storming here.


That is harder to regulate the water level vs. using a flashboard riser system where you add/remove boards to regulate the water height in the pond. A flashboard riser system typically uses 2" by (insert your board width here) and they can be slid in or out to regulate the height/depth of the water in the pond. Want the water higher? Slide in another board. Want to drop the level? Remove as many boards as you wish.
Maybe made into a cool feature of your pond. Just like to play around with ideas some stick some dont.

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