Drainage Pipe Behind Retaining Walls

Discussion in 'Landscape Architecture and Design' started by mbella, Jan 13, 2005.

  1. mbella

    mbella LawnSite Bronze Member
    Messages: 1,284

    Another thread made me think of this. However, I didn't want to take that thread off topic, so here I go. Has anybody ever seen water run out of a drain pipe that they installed behind a retaining wall? I'm not talking about a little trickling out, I mean water running out. Enough that you think," Damn, I'm glad that I installed that pipe."

    I went through the NCMA certification last year. The topic was discussed while reviewing the NCMA guidlines for installing drainage pipe. There were probably forty other contractors there and not one had ever seen water running out of a drain pipe installed behind a retaining wall. I'm not suggesting that it isn't necessary, but like everyone else in that class (including the instructors) I wonder. I've gone back to jobs during heavy rains, the days after heavy rains and nothing. I still install it on every job in order to cover my a**.
  2. kris

    kris LawnSite Bronze Member
    from nowhere
    Messages: 1,578

    No.....still put it in.
  3. D Felix

    D Felix LawnSite Bronze Member
    Messages: 1,898

    Probably the closest I've come to seeing that is this last summer.

    We completely re-landscaped five beds for one of our maintenance clients. It was actually the clients where we are building the retaining walls... The original install, like so many things there, was done wrong. All of the plants were put in heavy clay, and they were slowly dying off.

    We came in, dug out the crap clay down to about 18", installed drainage fingers in the clay (sock pipe), re-filled with good sandy loam soil, and re-planted. All five beds had a Celtic wall about 18" high around the front of them, the backs had fence. The drainage was outletted to daylight.

    About 2 weeks later, it poured. I had gone down to look at the existing walls, and noticed the water was coming out of the outlet. Probably around 1-2 gpm, nothing huge, but then again this was a 20'x20' area too.

    Not exactly drainage right behind a wall, but it was coming out. I was definately glad to see it too!:)

  4. cgland

    cgland LawnSite Bronze Member
    Messages: 1,929

    We did a 6' retaining wall a few years ago (see pic) that had a good deal of slope behind it. Well, this year I was at the property to do my 3 year inspection ( I do one every year for our warranty) and it was pouring, which is when I do my inspections, cause there is nothing else to do..lol Anyway, I bet there was 5-6 gpm coming out of the pipe! Now this is the first year I saw any significant drainage from the wall. Maybe it took a couple years for things to solidify and stop soaking into the ground!? I'm not sure, but I'll ALWAYS put drain tile behind a wall over 2 1/2 feet.


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