Pond Boss Forums GENERAL QUESTIONS Property Projects & Construction Cut my steel standpipe culvert to lower pond?

Total newbie here with a question. I have about one acre pond in front of my house created by a driveway damn with a outflow stand pipe of culvert steel in an "L" shape and about 24 inches in diameter. I had the pond built about 20 years ago.

Unfortunately, when the water level rises every Spring to the top of the outflow pipe, I note that my basement drain backflows water into the basement. I suspect the water level of the pond is about 8 inches above my basement floor (The pond and basement are about 75 feet away from each other). It is discouraging but not too much of a hassle when I am home to keep an eye on the sump pump functioning. I also placed a standpipe in the basement drain which helps somewhat but I still get leaks wetting the basement floor. The problem is my wife and I are considering snow birding out of town for the Winters and the thought of an unmonitored, flooded basement gives me concern.

My first pass plan is to cut the top 10 inches off the culvert, thus lowering the max pond level by 10inches and hopefully favorably changing the water table around my house. I have a few questions:

1) Is there a better method I should consider?

2) If I cut the pipe and discover the basement flooding is not caused by the culver, Is there someway for me to apply a water tight sleeve or other method to return to the previous pond level?

3) Could I consider just making a 10 inch x 10 inch square notch in the pipe top instead of cutting the whole thing off....a notch which could perhaps be re-damned if preferred?

4) How do I cut thick culvert piping?.....blowtorch?, Sawzall with the appropriate blade?, should I file down the sharp edges? ..........Call a professional?

Thanks so much for your thoughts.

Mike

Welcome to Pond Boss!!

That's an interesting situation you've got going on.

Do you have a sense of how much reduction in surface area of the pond will be lost if you take 10" off the stand-pipe? Will it become 3/4 acre for example?

Let's see what others have to offer.

Hi Sunil,

Thanks. The pond has a fairly steep slope so the area loss will not be too great. I would prefer it as large as possible, of course....but I am hoping my proposed course of action balances success with acceptable cost and landscape effect.

I like your idea of potentially cutting a hole or area out of a side of the stand-pipe vs. just taking the whole circumference down by 10".

I would think that would be easier to shore back up if you find the pond level unrelated to water in your basement.

Let's see what others have to say.

I'm not an expert in this matter, but serious doubt that the pond 75' away is flooding basement. My thought , may be worthless , is that water table rises , causing pond to rise , water table rises, causing wetness in basement . If pond water migrated 75' from the pond , the pond couldn't fill , Clay lining would be worthless . my $.02 , just my logic , waiting for an expert . I've dealt with a flooded basement , If you have a home alarm, a water sensor can be placed in your sump , having your Central Station notify on high water . Installed them for 39 years , work well. Welcome to PB , truly hope you get it under control.

Welcome to the forum!

I am leaning towards what Fishingadventure is saying. I think it's a groundwater problem and not pond related. In any case you might need to do two things.

1) Call a professional. in regards to the pond overflow pipe. You could use a battery powered grinder once the water level is lowered 12". Cut a large square out of one side of the overflow pipe. Weld up a framework out of steel angle that has a 3/16" (.187") channel around the inner "U" shape. Have someone form up a curved piece of 10 ga steel (.135" thickness is nominal) that has a curve and will be able slide up and down in that channel. OR, weld up a frame that is straight and use filler pieces to weld that to the curved outside of the overflow pipe. That way the "door" that will slice up and down could be straight.

That way when you want the water level to be to the top of the overflow pipe, all you have to do is re-insert the door in the frame, slide it down so it stops the water from exiting the pond.

2) Dig a french drain around the outside of the house, down to the level of the basement floor. Have that french drain dump into the sump pit and the sump pump will continue to work. Place a battery backup and extra sump pump in the pit, or have the french drain dump into a totally new sump pit.

Do #1 first after the pond is drained. Then when it's dry outside (say July) fill the pond up and see if water comes into the sump pit by mid August. If not, you know it's not the pond that is doing it, it's just the groundwater level around the house.

I have a french drain around the basement and drain tile under the basement floor that dumps into a sump pit. Right now with the wetter spring, the sump pump is running every 4 minutes to empty the pit. When it's drier out, it never runs.

[See edit below in bold.]

I agree with the replies above that the basement flooding is probably tied more to the local groundwater aquifer rather than just the pond. However, if the aquifer is somewhat limited in areal extent, then you can use your pond to draw down the water level in the aquifer and maintain a dry basement.

We do need a bit more clarification. When you say "when the water level rises every Spring to the top of the outflow pipe" does that occur only for a day or two after a significant rain event and then the pond returns to its "normal" elevation level (which should be around the BOTTOM of the outflow culvert)? Or do you mean that during the Spring, there is enough water throughput from your pond that the 24" culvert runs full bore for several weeks?

Does the water ever go over your driveway/dam?

Does the waterway beyond your outlet culvert have enough elevation drop that you could run a siphon? I am asking for two reasons. First, a temporary siphon could help you pull down the pond level while your basement is wet and determine what water level would be your optimal pond level. Second, you might be able to add a permanent siphon with less cost and effort than your (good) culvert modification plans. Further, adding the siphon would give you additional outflow rate for very wet periods at your pond.

Good luck on your nice pond/dry basement challenge!

I have been informed that I mis-read the original post. Most of my comments above refer to a configuration with just a horizontal culvert through the driveway. I missed the part about the STANDPIPE!

As Miss Emily Litella would say, "Never mind."

Hey Everyone,

Thank you very much for your excellent thoughts on this. It is like a very smart "Hive Mind".

As FishingAdventure pointed out, correlation does not mean causation. That is why I am hesitant to cut the culvert. I could be wrong and the pond level has nothing to do with my country home's basement drainpipe backing up with water. Ground water is very confusing.

But to add clarity, a time line might be useful:

1) 1994 bought the house. Had a wettish basement. Had french drain put in at the foundation. Problem much improved.

2) 2000 built the pond. My recollection is hazy, but my wife insists the drain problem began around that time.

3) 2002 I put in a basement sump pump and some time later a standing pipe insert into the basement floor drain. Both helped somewhat...but when the power goes out or the sump pump fails things get ugly. And my standing pipe in the basement does not seal absolutely. I'm usung one of those insert ones with the tightening screws that expand the plug.

Of Note, the basement floor drain pipe appears to head in the direction of the pond. I do not know where it ends when it exits the house. Given the pond is over 70 feet away, I doubt it ends in the pond, though that was a natural low area before the pond was installed and it would make some sense to have discharged it there. I have heard on Youtube that shoving a leaf blower down the drain might reveal the distal opening. I plan to try that when things dry up.

Spring wet season here in Wisconsin tends to last for about 3-4 weeks.

Essup, that blocking gate sounds like a great idea. Is there a way to post pictures on this forum? If so I would very much like to see a photo of what you are describing.

[u][/u]

Bruno616:

In my previous life I was a designer/fabricator for all things R&D. I still do a lot of that when needed. The design is between my ears right now, I can do a quick CAD drawing (carbon activated drawing - i.e. pencil to paper). I'll take a pic of it and post it here. If you are familiar with mechanical drawings, that's how I tend to do stuff - top view, side view, front view.

I'll post pics of my latest temporary "fix". I had issues on a trailer, I will install the modified parts tomorrow and see if my idea works.

O.K. Here we go. I changed the trailer suspension system from a equalizer type spring system to a slipper type spring system. I measured the center to center points like the mgf of the trailer parts kit said. I came up with a shorter dimension than what they said to use. I called them and they said no, use the 30 1/2" dimension instead of the 29 5/8" dimension that I thought would be the correct dimension. So, I used their numbers. I drove the trailer 14 miles, checked it and found that the top leaf popped out of the center pivot bracket because the brackets were too far apart.


So, my choices were 1) order a new center pivot bracket to weld to the trailer and wait until it showed up. or 2) Modify the center pivot and "make that side longer" so the spring wouldn't pop out. Here's what I thought up with the materials that I had on hand. Weld a 1/4" thick piece of steel inside the bracket so the spring will slide on this instead of the original pivot bracket. This will do two things. 1) make that side of the pivot bracket longer and 2) make the spring ride closer to the stop bolt that is supposed to stop the spring from slipping out of the bracket. Once that spring leaf slid out of the bracket, it allowed the bent down primary spring leaf to slide over the top of the bolt - barely. So, here's what I came up with:




The steel block stiffens up the piece of 1/4" steel that I welded to the bracket and it also gives me a bigger surface to weld to because I can bump it against the turned up edge of the bracket and weld it there as well.

Do you have easy access to the top of the standpipe? Or is it obstructed with a grate or anti-vortex baffle?

For a short-term test and possible solution, you could just get 10' of corrugated plastic drain pipe and start a siphon from the pond and into the standpipe. You probably need to use wire or baling twine to tie a "J" into the bottom of the section of pipe that will be hanging in the standpipe so that air doesn't go up backwards against the flow and break your siphon.

(You also need to tie a 2x4 or something similar to your siphon pipe, so that there is zero chance it goes into your outlet pipe and gets stuck as a wadded up plug.)

You could also probably do it with 4" DWV pipe with to 90 degree elbows together at the end that goes into the standpipe to give you a turn-up. Put a screw cap on that end and a check valve on the pond end. Fill it with water, install the cap, and then hold it up high over the rim of the standpipe. Unscrew the cap, and as the siphon starts going, lower the siphon assembly into place and let it rip!

What a great idea....I could test my theory that it is the pond level!

My weekend is planned!