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Help... my drainage system washed out!!!! :-(

Discussion in 'Starting a Lawn Care Business' started by doozman, Aug 22, 2007.

  1. doozman

    doozman LawnSite Member
    Posts: 7

    Dear fellow LCs,

    I need some help from a "drainage pro." One of my customers wanted me to fix their drainage issue, which at the time appeared to be a relatively simple project. As you can see from the picture #1 below, they have a a steep slope that runs underneath their back yard deck and levels out near their basement entrance. When I came out to look at it, I saw where the path of the water was, and decided to regrade near the basement (taking the water away from the entrance toward the back yard – this part seemed to work fine) and design a "french drain" system to carry the bulk of the hillside water across the back yard (it all worked so perfectly in my head!).

    Here is what I did: I first decided to basically follow the path of the existing water flow, which had already washed out a lot of dirt (Virginia clay) and created a huge cavity underneath the deck. Then I dug out this cavity a little further (total trench was about 24" deep and 10" wide) and continued a trench all the way across the back yard (about 50’) making sure the base of the trench had a downward slope at all times. I then installed two 4" ADS perforated pipes (w/socks) side by side. One of these pipes tied into all the downspouts for roofwater, and the other one had a 12” ADS basin drain at the top end. They both daylighted at the end of the 50’ trench. I backfilled the trench with pea gravel and about 6-8” of the remaining soil. We then tamped down the ground. My thought was that the basin drain would carry most of the water, and what it did not catch would percolate down into the perforated pipe. Instead, it looks like a lot of the water bypassed the drain and washed out most of the fill dirt and some of the gravel I had installed.

    Admittedly, there was no sod or other erosion control installed, but we have recently been in a serious drought and it didn’t look like anything would grow at the time of installation. So far, I can think of three possible solutions: 1) move the drain to a slightly lower elevation (where it looks like the worst of the erosion took place) and try to create somewhat of a “crater” that directs all water into it, 2) install sod (or a better erosion control?) now that the ground is wet, and 3) maybe install another drain at the bottom of the hill (near the steps) to collect any further water runoff. As a last resort, I could try to re-contour the ground but I think that would involve moving a lot of dirt and I’m not sure they want the entire hillside changed.

    Here are some specific questions:
    1) Did I put enough (or the right kind) of gravel in the ditch?
    2) Is it reasonable to expect the water to seep through the clay into the perforated pipe or should I try to catch all the water with yard drains?
    3) Are there any better yard drains you guys have used then the square plastic basins from ADS?
    4) What is the best thing to install for erosion control on a steep hillside like this one?
    5) Is there anywhere I can go to learn more about drainage and erosion control?
    6) Any further suggestions?

    Thank you so much for your help!






  2. doozman

    doozman LawnSite Member
    Posts: 7

    here are a couple more pictures... thanks!


  3. PaperCutter

    PaperCutter LawnSite Bronze Member
    Posts: 1,943

    Tim- I've had the greatest success moving water by sculpting a clearly defined swale and sodding over top of it, so you're moving water on the surface.

    I had a similar situation to your site conditions last year. We put in some low walls (12" and less) around the perimeter of the deck to push most of the water around that area; created a bowl under the deck with a central drain that daylights away from the house; and cut a good swale to carry the surface flow to the street. In your situation, I'd look at really trying to push water around the screenhouse section of the deck (vs. under it), and maybe even holding that slope with some good-sized river jack.

    I've noticed that at least where I live in VA, the clay soils and our sudden, fast storms don't let a lot of water percolate down. Where are you?
  4. scout279

    scout279 LawnSite Member
    Posts: 82

    Hey Tim...

    Were in VA are you located?
    I have been dealing with a similar problem around a pool retaining wall we put in. I have added some more drains higher up from the pool and it helped. But with the heavy rains we have had there is now some new issues. You might want to either try adding a drain to the right of the existing one in the second pic. or move that one over. Just looks like thats were the wash started, but its hard to tell in a pic.
  5. topsites

    topsites LawnSite Fanatic
    Posts: 21,653

    Well I tell you, there's likely but so much you can do, the slope isn't going away and neither are the torrential rain falls, both of these are, in your case, acts of nature that, unless you want to move the house...

    I would first carefully listen to what other folks have to say, I'm no expert in this area and these are just some ideas based on memories of some folks who had similar problems and how it was dealt with.

    Most every method used will likely require constant care, drainage will always be a problem and so will the resulting erosion, the only semi-permanent solution isn't cheap either, it all costs money either upfront, or over time, and unless you call around and find someone who has dealt with this before, numerous times, and successfully, that would be the ticket, no offense to anyone who has done work there before because this stuff is a mayor pita!

    You can try a bigger french drain, more gravel and so on...
    But these rains we get are no joke, so much water comes down that no drainage system effectively sifts it away and still it runs down in a torrential river that washes away dirt and land, we have a few roads here that get water running around so deep it washes cars away...

    So, you can try and re-dig that ditch and build a type of permanent channel that funnels the water so at least it all runs in one path, and with a french drain underneath, perhaps another drain as well, and to stop the erosion use some of that green plastic mesh... This stuff gets all kinds of messy with any type of core aeration, on top of gravel underneath we're just throwing in one type of material after another, the question remains how much erosion will it stop?

    Build a retaining wall near the bottom, then bring in topsoil and redress it all and level it all out. This method is likely the most expensive initially, but once taken care of should last many years, but not forever. The amount of topsoil will be huge in terms of weight and labor, also there still needs to be some type of drainage but this isn't my specialty, still this method might be the closest we come to a permanent solution. Yes, basically the retaining wall needs to be high enough to match or come close to the top of the slope, starting at the bottom, then the resulting space needs to be filled in with some type of dirt, etc...

    A more redneck solution would be to re-landscape the area some, to where it funnels the water away from the house and the porch. It will still erode, but work out a ditch of sorts from near the top and run it aside the current path and away the house and down, obviously erosion still happens just now 15-20 feet over, but being that I can't even see the end of that slope...

    Perhaps a combination of a retaining wall in a L shape for the porch area, then a drainage ditch aside that.

    That's all I can think of.
  6. Runner

    Runner LawnSite Fanatic
    Posts: 13,494

    I was having some trouble understanding why it may have done this as a I read through this, knowing that it SHOULD have had some sort of turf or erosion control over the top. Then,....I read the word that summed it all up. Clay. If you are putting clay over top of the drainpipe and the gravel, you are defeating your purpose altogether. You have to have a soil that drains - preferably sand. What you have going underneath works for you, it is just your surface situation that is hurting. Your surface looks like it is a sand base, that makes it even more vulnerable - especially with the hardpack underneath. Afterward, you have GOT to get some sort of ground cover on that as soon as possible.
  7. NickN

    NickN LawnSite Bronze Member
    from Alabama
    Posts: 1,010

    It's a simple fix.Install a larger catch basin, like a 36" square basin.You're trying to divert too much water to a basin that can't handle the flow.
  8. PaperCutter

    PaperCutter LawnSite Bronze Member
    Posts: 1,943

    I'd rather push water on the surface than rely on a lot of plumbing that can clog.
  9. doozman

    doozman LawnSite Member
    Posts: 7

    Hey guys... thanks for all the helpful comments. I live in Northern VA, Loudoun County, a little northwest of Purcellville. I'd be interested to know if any of you are nearby.

    To expound on why we didn't put in any erosion control... it was during a drought with 100 degree temps and nothing was going to take at the time of installation. I probably should have tried to time the weather right and gotten some sod installed right before the heavy rains. But that brings up another question... is sod the best erosion control out there for this application? It's pretty much full shade under the deck.

    Anyone have any experience with the green mesh that Topsites was talking about?

    Dave (Papercutter), can you post a picture of the similar job you just did? Your idea about the retaining wall and everything is something I thought of as well, and I think it would work great, but that's a heck of a lot more money and work. I probably should have tried to sell a system like that to the customer initially, but I sensed they were trying not to spend any "big bucks" at the time, and I thought the cheap and simple french drain solution had a good chance of working.

    Which brings up another question, how would you guys handle this from a warranty perspective? I feel bad, because I told the client that this should fix their problem (and I believed it would). I'm sure that what we did has helped their situation, especially since we tied in all the downspouts, but it just isn't a total fix yet. I expect to do adjustments to the work I have already done, but I'm not sure I can offer to put in a retaining wall or a different major renovation for free... (Actually, I would do it if I could, but I don't think I could handle it financially right now.) Any thoughts?
  10. echeandia

    echeandia LawnSite Bronze Member
    Posts: 1,131

    What you need to do is install a french drain between the columns of the deck rather than the 12" catch you have. You build a french drain just like you build the 50' section except don't cover the stone with the soil. Tie it into the pipe you already have installed. Fill the trench to the top with the stone.

    I'm in Loudoun County if you have any other questions.

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