Retaining Wall in Wet Location... Base???

Discussion in 'Hardscaping' started by NJemerald, Jul 28, 2006.

  1. NJemerald

    NJemerald LawnSite Member
    from NJ
    Messages: 121

    I'm currently bidding on a retaining wall that is on very wet soil/area. The wall is about 50' long with 2- 18" tiers stepping back about 3'.
    All the walls I have built have been in dry locations w/ gravel and pipe for "possible" water build-up BUT NEVER built IN an existing WET Location.

    Would anyone mind sharing their experiences / building tips when building in an existing wet location?
    I've heard anything from going thicker on the base too using...
    6" of 3/4 crushed stone w/ 2" of QP on top to allow water to pass under the wall.

    Thank you for your time,
  2. wurkn with amish

    wurkn with amish LawnSite Senior Member
    Messages: 662

    can you catch the water before it goes behind the walls? Like maybe a couple french drains up the hill some?(I'm assuming its on a hill.)
    Another thing that worked well for me a couple of times, was to excavate wider and deeper put down geofabric that extends 2ft up both sides
    put in 411 limestone in 4-5" lifts to 12" fold the fabric over like a burrito.
    then build your base normally from there, maybe a little thicker than you would normally for a 18" tall wall. start your wall and put in drainage.
  3. nac

    nac LawnSite Member
    Messages: 126

    I did a job where the soil was wet slop. The site engineer made overdig 2' deep by 4' wide and fill it with 2 1/2" stone wrapped with filter fabric and then lay 6" of 3/4" clean stone on top to level the block
  4. NJemerald

    NJemerald LawnSite Member
    from NJ
    Messages: 121

    I can't really catch the water with a french drain... Customer doesn't want to go through all that and it seems like the water is sepping out in this area that the wall is being built/replaced... prior wall was RR ties.
    I have every intent of using filter fabric to wrap the 3/4 crush and 4" drain pipe behind the wall... just never heard of using 3/4 under the wall for water to pass through... thought base was always suppose to be QP / packed for better support!?!?

    so you laid the 1st row of block "right on" the 3/4" stone!?!?
    Was it compacted?
  5. nac

    nac LawnSite Member
    Messages: 126

    Yes layed it right on 3/4" stone and it was compacted all the walls i do lay on 3/4" clean compacted stone and probly have done over 40,000 sf of walls
  6. wurkn with amish

    wurkn with amish LawnSite Senior Member
    Messages: 662

    if the customer doesnt want to go through all that to do it right, then do you really want your name on the job?
    why would you want water to go under your base? that recipe for failure!
  7. Tony Clifton

    Tony Clifton LawnSite Senior Member
    Messages: 865

    I would not touch the job without having an engineer tell me what to do. You could probably hire one to give you some preliminaries for bidding purposes for less than a couple hundred bucks.
    As far as the 3/4" stone goes, 6" is not going to be enough, I would plan on 12" at a minimum, and you will have a 2-3 courses of block under ground.
  8. Tony Clifton

    Tony Clifton LawnSite Senior Member
    Messages: 865

    I just reread your initial post, I didn't realize how small the wall was....6" would probably do it, but I would have a course under ground to be safe.
  9. Mike33

    Mike33 LawnSite Bronze Member
    Messages: 1,649

    I agree with what everyone else said except the 1 who said dont do. With out repeating every post and they are all correct i would lay a layer of stone then geo-grid than layer stone and compact. I like the post where he said make your footer wider that is the key also. You will be fine if you put all of these togeather. I have a least a dozen with this problem ranging up to 4' in height and no problem.
  10. neversatisfiedj

    neversatisfiedj LawnSite Bronze Member
    Messages: 1,028

    Nac - I built my own AB wall on 3/4 clean stone but always use road base (CR6) on all walls now. Easier to leval and compacts better- NCMA rules


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