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drainage from around a retaining wall

Discussion in 'Landscape Architecture and Design' started by jayman99, Oct 13, 2006.

  1. sunray

    sunray LawnSite Member
    Messages: 218

    Chances are with the wall self destructing at one end and you are saying it's water causing the collapse of the wall, it probably was not built correctly from the start.
    I agree try to keep water away from it or tear it down and do it right.
    To dig down that far in that narrow of an area beside a lake is asking for a disaster.
  2. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Messages: 2,454

    AGLA hit the nail on the head here. What you want to do is utilize the best resources available to you to make your best decision and shift responsibility.
    An engineer who specializes in and works in your area will already have dealt with a handful of these over the years and will have figured out the best combination to create a suitable fix. It would be money well spent.
    As far as rules and regs. go........they differ from area to area. In our area, any wall over 4', by code, must be engineered and inspected as it is being built. Lots of folks ignore this little tid-bit, but when they start to fail ( for whatever reason ) letters start flying from law firms and that is way more expensive than the money you would spend initially on an engineer designing a system for a fix.
    Everyone here may be right with their suggestions, but I guarantee you everyone here is wrong if you do anything without an engineer's stamp on paper......especially if you sell the home to a new "happy home owner" and the wall, for whatever unforseen reason, should crack, move or fail. The new happy homeowner would become your worst nightmare and an attorney's dream......
  3. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    Ya know I think that home has been there for years as well as the wall of course. So I say your soil should be stable as heck. I don't know about "gumbo clay" but most clay soils compact and are very stable. That's why water won't soak in because the soil is compacted and surface water will only soak in a few feet, then when saturated it will just run off to a low place, right to your wall in your case. I think this water did play a part in separating that corner but It looks like an unsupported un reinforced corner that was going to go sooner or later with soil pressure, water pressure whatever.
    First thing like advised above is get rain gutters on your home and attach drainlines to all the downspouts, digging a trench for each drain line and taking ALL the roof water out away from the house, the soil around the house and water away from the wall and into the lake. This would be my #1 priority while you are figuring out what other measures you need to take to fix this problem.
    #2 priority would be to go ahead and dig a trench all along the top of your wall and install a drain, not flex but PVC 4" with holes on top on the sides. Grading the drain down towards the lowest part and into the lake. Wrap it in fabric if it makes you feel better but I think you need quick drainage not weepage into this drain so I would line the trench with fab or very heavy mill plastic but leave the holes in the pipe clear of it. Then fill the sides and top of your drain with 1&1/2 to 2&1/2 inch round rock(leach rock) not gravel. Then I would remove the kids slide in winter that is like having a waterfall in heavy rain.
    These are things you can do NOW while you save your $$ for a new engineered wall. You are going to have to have that wall replaced no matter what.
    Did someone say a railrod tie retaining wall? Bad idea there.
    Also those drains in the base of the wall are probably already attached to a drain.
  4. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    If you want to pull the smaller detaching wall back in then dig the soil away from it as much as possible. The drill 4 holes in the wall. drive 5 to 6' #4 rebar through the holes into the soil behind the wall at a downward angle and then put metal plates with holes in the center over the rebar ends sticking out of the wall, then weld bolts onto each rebar end. ( they may sell this type of wall deadman already complete)
    Brace the wall back up to its former position, tighten the bolts and then pour cement over the rebar behind the wall where it is exposed between where you dug out and where it goes into the soil..not too much just enough to hold your deadmans. Let set and backfill the wall adding drainage.
    This should pull the wall back in.
    Regardless you will have to get an engineered wall installed. Your wall should have been built like a seawall, because if your wall falls into the lake you could be in big trouble. Here, walls that are built on lake shores are required to be engineered no matter what.
    I hope this helps.
  5. mdvaden

    mdvaden LawnSite Bronze Member
    Messages: 1,946

    I think your wall may be falling due to a poor support underneath for that much weight, not neccessarily the water.

    Put a drain line at the top, not deeper than 1' deep? Why go 2' even?

    Just catch the water and take it to the end. Or, just dig down to one weep hole near the middle and send it down to that one.

    Try digging holes by the wall, with small trenches coming back away from it. Then, get a masonary drill bit and drill into the back of the wall at entervals, insert anchoring fasteners, and run a dead-man cable or brace to anchors back from the wall (like concrete poured into holes).
  6. mdvaden

    mdvaden LawnSite Bronze Member
    Messages: 1,946

    This gave me a chance to mess around with my new version of Adobe Photo. The options are sure laid out different than the old version I had. Anyway, this was the closest image I could find to illustrate.

    The gray boxes represent concrete cubes set back away and hidden below the surface. The blue lines represent cables (which could be coated to prevent corrosion.

  7. jayman99

    jayman99 LawnSite Member
    Messages: 13

    Hey guys. thanks for all the additional input. it's raining hard as I type this so if I have to leave in mid sentence it's probably because the house just washed into the lake. :laugh: If I didn't laugh, I would just have to cry. :cry:

    Let me give some basic info that I should have included already.

    The house and dock are about 5 years old. That end of the wall started failing about 2 years ago (at about 3 years old). The failure occurred shortly after my neighbor's house was built next door. The neighbor built his retaining wall adjoining mine which cutoff the path for drainage between our homes. He had a small drain there, but it was inadequate for the volume of water. As a result, the weight of the water and soil broke the wall. The break in the wall allows the water to flow through and has reduced the pressure in that area and so the wall has hung like that for some time now. At this point you're thinking "2 years ago? what the heck has he been doing?" Well, I've had a number of bulkhead builders look at, but they don't seem to be interested since it will be difficult to use machinery to dig and will take so much manual labor. They seem to have plenty of easier jobs available.

    The wall itself is built on a two foot deep footer and is made of cinder blocks with rebar coming up from the footer through the blocks. I'm not sure how much concrete was poured into the blocks, but at least enough to hold the rebar. The front of the blocks are covered with rocks for appearance purposes. There are no deadman tiebacks.

    "Huh" - You are correct that this "black gumbo" soil is fairly unstable, but all I can do is keep the water moving out to the lake as best as I can.

    "DVS" - The distance between the house and the wall is probably about 15 feet, but it's fairly flat and I don't think I can get the surface to flow the water out without a drainage system.

    "Rockset" - I have considered the danger of digging and I see your point that it is risky. What type of precautions are used when digging a hole like this? Do you keep a rope around the guy or put a ladder in the hole?

    "AGLA" - There is no crawl space or basement. The house is built on a slab.

    "Sheshovel" - I thought the holes were supposed to be on the bottom for a french drain?

    "MDVaden" - Yes, I think it definitely would have helped for the wall to be built with deadmen tie-backs to help support the weight and I think it is a good idea to install for the corner that I am going to repair.
  8. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    Repy, you don't want a french drain in this situation, you want the drain to gather water from the surface and move it out of here. Holes on top.
    I suggested deadmans being installed, did not you read my whole posts?
    Rain gutters,slide, drains ect?
    Who installed the wall? Will your homeowners cover?
  9. AztlanLC

    AztlanLC LawnSite Bronze Member
    Messages: 1,051

    You have one of the worse cases scenarios.
    There is no safe way to dig a trench in those conditions.
    What for do you want to tide a rope to a person digging the hole? to pull his buddy out after dying.
    A ladder? for what purpose?
    The soil can colapse at any second and kill a person with the force of impact, or many other causes.

    Tha wall can be failing for many reason and you have to find the real problem before trying to solve it.
    Find an engineer and ask him also to reffer a person that has deal with this type of problem before they should know.
    May peoples assumption the water doesn't precolate on clay is wrong, it might move slow but it does.
    Installing a drain system on the surface might help some but will not solve the problem.
    Sheshovel I don't mean to offend you but, unles he installs the pipe as a channel drain having the holes facing up is wrong.

    Like I said before that wall could be failing due to many reason, even if it has being doing it slowly for the las 2 years that doesn't mean it will not crumble in a single day.
  10. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    Sheshovel I don't mean to offend you but, unles he installs the pipe as a channel drain having the holes facing up is wrong.
    Really no kidding? I said NO french drain but a drain to take the water AWAY from the area and into the lake.
    That IS a channel drain!

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