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Shallow Trench to drain surface runoff  RSS feed

 
Karen Grider
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I have a drainage issue that appears to be surface but the area also remains damp beneath the surface. My issue is that the slope of my yard only drops 7 inches across a distance of 55 feet with the biggest drop in the first 15. That means the last 40 slope is so low that I cant' dig a trench any deeper than 6 inches. I know that is not enough for a french drain. I dug the trench anyway. For your visualization the issue originates beside my house before the gate to the back yard. Its rather steep and runoff from my neighbor goes down there and prevents grass from growing. I have littered the area with logs and rocks and that has helped grass and weeds to grow. I am dealing with this later.

At the bottom of the hill starts my back yard with a gate entrance. The previous owner put a gravel bed and stepping stones there I found out by accident when weeding. It was totally buried in dirt. I built a "wall" from landscape stones at the gate to block any further erosion into that area. I excavated that area removing the gravel and washing it and recovering the stones. This created a huge pit that when I put the rocks and dirt back in was lower than it originally was. I also realized why the plants grow so well over there.. water! The soil remains wet for a long time after a rain. I decided to put in a diy makeshift drain. This is where my question comes in. This drain is not standard or as recommended by sites that discuss french drains. I am dealing with surface runoff too so I did it like this. The pit at my gate was there after I dug out the rocks. I wish I had left it alone. This first 15' is where the path was and the steepest part and elevation drops 4" from top to bottom . Since it was full of water after a rain and after my efforts to wash the rocks (don't ask me why except hey are very decorative) I had to drain it so I dug out into the yard down to my flower bed in the back. It drained. This trench I dug was 35'. This slope only drops 3" over the 35' so the trench is shallow. 4-6" mainly because the flowerbed at the bottom is higher. Any deeper and I go underground into the flower bed.

Ok with this information I dug the 35' with a 6" wide and 3-5" deep trench down the yard to the flowerbed. I lined it with landscape fabric. Put in large gravel and a 2" perforated pvc pipe. The pipe runs from the gate through the "pit" lol and down the trench to the flowerbed (and is slightly below the grade). My question and concern. Since the 35' trench so shallow and the gravel so big the pipe does not sit low in the trench. In some places I only had room for 1" dirt on which to place sod. Would it be better to just remove the pipe and put in more large gravel? It would be an underground creekbed. The first 15' right now is not underground. I barely have the pipe covered with gravel and am not sure if to leave the pipe or not. and am unsure if I should cover it with fabric and bury that (rocks or soil?) Here is a list of my questions:
1. will the long trench work well without the pipe if the rocks are large in it and its enclosed in landscape fabric? My soil is clay so it still would be path of least resistance
2. The first 15' same question and would there be an issue if I put the fabric on top and buried that too with soil?

3. I know its important to consider the source of the runoff which I am thinking about right now. I put large rocks at the point where the water enters from my neighbors property. This won't stop it but will slow the water down so I can get the grass to grow and root the soil. I am doing this job myself and for a woman I am realizing I am over my head with labor but I am committed to finish. I can't take on this part yet though so I am hoping the logs rocks and dams I have put there will keep the soil movement and slow the runoff.

I knwo this is long. I would appreciate any help or advise. keep in mind I need to work with what I have already one. I have lots of work invested in this already. My solution isnt perfect but I am not going to change it in large ways right now. What will make my current solution work better? I will consider major improvements with the next project. I wish I had planned better from the start but I didnt plan on doing this to begin with. It grew as I worked and now I have a problem to fix. Thank you!!
 
Jay C. White Cloud
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I tried following along with your description but I for one will need you to boil this down and provide photos before my advice would have any merit. I would further add that you last statement sounded like you done the work and don't plan to change it?

Break this down with photos, and ask a direct question, and I am sure I and others here can give you some advice, but you may have to change some things to achieve a good drainage plan.

Regards,

jay
 
Karen Grider
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Thanks for the input jay. Here are my clear questions about how to proceed

Here are the pics I shared from my facebook page.
Share of Yard Album Pics on facebook

Attached is a drawing too.

55' trench. (I seperate them into parts because their grade is different Maybe this isnt important for my question)
----Part A. first 15' wider steeper and lined with landscape fabric, rocks, and 2" perforated pvc pipe. slope is 4" over 15'. unfinished. See pics
----Part B. balance of length of trench 35-40' is already buried. landscape fabric, rocks, 2" perforated pvc, landscape fabric folded over the top, soil, and sod See pics. Slope is 3" over approx 35-40 feet

Questions:

1. Trench Part A...would it be better for me to remove the pipe? Does it really add value?
2. Trench Part A Would it be an issue for me to cover the top with fabric, and bury it in soil and sod it or should I leave it as a gravel path? Reason I ask it is soil on top would give me the option to put a concrete sidewalk, pathway or steps there later.
3. Trench Part B...Would it be better for me to remove the pipe from my trench and just use rocks since it is so shallow?
yard-diagram.jpg
[Thumbnail for yard-diagram.jpg]
 
Jay C. White Cloud
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Hi Karen,

That helps a great deal more.

1. Trench Part A...would it be better for me to remove the pipe? Does it really add value?
As for value if you see that the landscape is less soggy, then it is doing something. I would have gone to a more standard functional design as such 3" to 4" pipe that is a minimum of 12" down, backfilled with gravel, and warped and covered with filter cloth. If you are going to take the energy to do something, down to capacity and correctly.

2. Trench Part A Would it be an issue for me to cover the top with fabric, and bury it in soil and sod it or should I leave it as a gravel path?
I would leave as gravel.

Reason I ask it is soil on top would give me the option to put a concrete sidewalk, pathway or steps there later.
No actually soil on top would not give you that option because you do not want to bed concrete or stone in soil but on the gravel. Only undisturbed mineral soils that naturally drain well, that are below a given forest line are ever suitable for setting stone or concrete.

3. Trench Part B...Would it be better for me to remove the pipe from my trench and just use rocks since it is so shallow?
Yes, probably

Hope that was of some help...

Regards,

jay
 
Karen Grider
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This is great to know! I appreciate all this info. I used 2" pipe rather than 4" on both A and B because Trench B does not have the slope to use 4". I used the largest size that would fit both. You're right I do want to do it correctly but also make the best of a limited slope.

Would it work if I make both without pipes and just have an open gravel bed that feeds a buried one? (wrapped in landscape fabric) Would it be a good enough solution for now? Next year I plan to revamp the whole thing. I just don't have the money right now and I have two trenches to deal with, wet soil, and rainy season approaching. Is my logic poor that this is an improvement for now . If there is any slope then water should prefer a graveled path correct? If this trench path will never be "ideal" then I will put in "ideal"next year and do "good enough" this year. I appreciate your help making this good enough and not a fiasco.

There is another trench path I should have taken that is a slope all the way to the street in the backyard (my house sits on a street in the front and back) but its very long and not feasible to do this year. i never planned to make a trench at all or I would have planned for this or hired it out.. next year Trying to make the best of what i have.

its not too late to just fill the whole darn thing in and pitch in the towel. Surely there is some benefit to what i have done so far.

Thanks again.
 
Jay C. White Cloud
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This is great to know! I appreciate all this info. I used 2" pipe rather than 4" on both A and B because Trench B does not have the slope to use 4". I used the largest size that would fit both. You're right I do want to do it correctly but also make the best of a limited slope.
3" or 4" pipe is standard and would have still been best in your case. As for slope you would have created that in the bottom of your trench. 1/4 for ~ every 10' horizontal travel would have been sufficient. 2" has tendency to "silt in" even with cloth.

Would it work if I make both without pipes and just have an open gravel bed that feeds a buried one?
If you are going to redo it this will be fine for now.

(wrapped in landscape fabric) Would it be a good enough solution for now
?Yes

Next year I plan to revamp the whole thing.
Good

If there is any slope then water should prefer a graveled path correct?
Depends...water goes to gravity and path of least resistance.

Regards,

jay
 
Hey, sticks and stones baby. And maybe a wee mention of my stuff:
Jacqueline Freeman - Honeybee Techniques - streaming video
https://permies.com/wiki/65175/videos/digital-market/Jacqueline-Freeman-Honeybee-Techniques-streaming
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