Need some help on a drainage project

Discussion in 'Hardscaping' started by MJK, Nov 23, 2011.

  1. MJK

    MJK LawnSite Senior Member
    Messages: 356

    I have a house that has some real severe drainage issues. Its a 30'x30' area in this persons back yard. The area is filled with extreme clay soils. The neighbor to the one side is about 4'' higher in grade then the property owner I'm working for. The rest are about level. Water always pools at this guys house and sits there for weeks on end.

    We came in and removed about 7 yards of clay soils while we dug in a french drain. The french drain was dug and made a double, (2 pipes). We then brought in 12 yards of topsoil and graded it out. We didn't't lay sod yet. Last night we got some real heavy rain and water is again standing in the same spots. I'm a little confused on what to do. Maybe more french drains? The current one is 30' in length and 1.25' in width. Any ideas?
  2. LindblomRJ

    LindblomRJ LawnSite Silver Member
    Messages: 2,570

    Where does the french drain empty the water it collects?
  3. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,567

    French drain is a broad term. Here are my thoughts:

    1) When we do french drains, a.k.a drywells, we install PITS.We do not usually do trenches with pipes. So we may install a pit that measures 6 x 6 x 5 and fill it with clean 3/4".

    2) If there is a lotta rain - the pit will overflow because water will not percolate in the clay soil. so your pit needs to be sized accordingly to prevent this. Othewise, you'll get an embarassing call from the client.

    3) Water flows downhill. You can't place more soil along the make of the house and TAPER down into the yard?

  4. LindblomRJ

    LindblomRJ LawnSite Silver Member
    Messages: 2,570

    Dry wells are well and good. With that amount of clay you want to have it drained out somewhere.

    1 1/4" pipe, is it perforated? That seems rather small for collecting and moving water. If there is a lot of clay soil it might be possible to get below the clay to make a dry well effective.
  5. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,868

    Dry wells are a complete and total waste of time - at least in Oregon. I've installed plenty and they've always become totally full within less than 1 day of rain. And with our clay soils here it takes forever for the water to percolate out. Then, once they are full, your drain pipes can't drain anymore and you're back to square one.

    I quit installing dry-wells and flow-wells. We attempted to install 2 massive flow-well systems about 2 years ago. One of was 6' deep, had 4 flow-wells along the bottom and 3 flow-wells along the top. It could handle HUNDREDS of gallons of water. The thing was totally full of water to the top of this giant pit we created before we could even finish the job. The second one was a really deep one. I had my buddy come in with his track hoe and dig us a hole about 12' deep. And we just stacked a series of like 5 or more flow-wells on top of each other surrounded by tons of river rock. It was a huge hole. A few days later, big rain storm, got totally full and backed up within less than a day.

    We do a lot of drainage - unfortunately. I hate drainage work. It's mucky, muddy, messy, and even despite your best efforts sometimes you still don't totally fix all of the drainage issues that may exist. It's often a multi-phase approach. But we do a LOT of drainage - simply because it's a great source of revenue and we've gotten pretty good at it over the years. We easily install a good 100+ drainage systems each year. Just finished one yesterday. Got another going in Friday and one on Tuesday again....

    I could help you but I'd really need to see some photos of the property. Without knowing that the elevations are like, I couldn't even begin to come up with a plan.
  6. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,567

    I wouldnt make a blanket statement saying drywells are a waste of time.

    We do alotta drainage work with a 100% success rate, and I can't tell you how many drywalls I have done. I love it! Easy work, and pays better than patios and walls!

    Everything needs to be sized accordingly. Rainfall and surface calculations must be done. We had one customer that needed roofing downspouts routed underground. He's an engineer, he ran the numbers based on his square footage of roof, and had us installing 6" pipe. Works like a dream!

    I will say we do jobs where I as an owner have to be there for every minute of the job. And when it's all compete I often think "there is no possible way a larger company with delegated workers could have successfully completed this".

    I agree clay can make problems. If the soil won't percolate for a septic system, it's probably not a good ideal to put in a dry well. As they both work pretty much the same.

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  7. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,868

    I didn't. Let's go back and read what I wrote....

    Dry wells are a complete and total waste of time - at least in Oregon.

  8. bigslick7878

    bigslick7878 LawnSite Senior Member
    Messages: 809

    Pics would help....a lot.
  9. vtscaper

    vtscaper LawnSite Member
    Messages: 159

    There is a method which we have used a few times that works very well, it is however really expensive to do.

    It will work for both ground water and surface water issues.

    -figure out where you want your finish grades. note for best results set grades so the stone layer has an exit at the down hill end of the area. e
    -the depth you excavate to will vary depending on whats happening for finish ie grass or planting. for grass go 18" minimum below finish grade. slope your sub grade to the exit noted above.
    -install filter fabric
    -install 12" of clean stone.
    -install second layer of fabric
    -install your light top soil. What we have done for very large areas is screened on site mixing sand with the less clay material- basically making our own topsoil. it has to be a big enough area to warrant this but can save big$$ and time.

    so basically you are building a drain under the entire area. there are variations to this but this is the jist.

    for ground water you are creating a capilary break with the layer of stone.

    for surface water you are allowing the water to perc through your light soil and penetrate into your underdrain.
  10. MJK

    MJK LawnSite Senior Member
    Messages: 356

    I will have to get pics on friday. One of the main problems is the house is in an old neighborhood. So the lots are very small, fenced in with limited access.

    As for the french drain we installed, we made 4 of them, starting at the fence line and working accross the property, seperating them by 1'. They are dug 15'' below grade, fabric layed on the bottom, 2'' pea gravel, corrigated socked drainpipe, 4-5'' of peastone fill, then another fold the fabric over to close it up. At each end of the drains we put in small circle drywells, 2' across and 30'' deep.

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