Crazy idea to keep the creek out of my house:

acerOctober 8, 2011

OK, the title is a little exaggerated. The creek comes down the hill and past the house, but in the heaviest cloudburst it has never left its banks. The problem is with underground seepage that follows roots and rocks to go under the house and keep our crawlspace damp. We will probably install a crawlspace liner/encapsulation system, but we still need to eliminate as much underground water flow as possible. Here's the crazy idea. It's similar to a french drain, but it's for groundwater, not surface runoff:

We want to dig a trench about 2 feet wide and about three feet deep. The trench will run at a diagonal through the yard about 15 feet below where we think most of the seep comes from. The trench will have a gentle downward grade following the natural lay of the land as it slopes toward the creek, so gravity will pull the water out. Here's the tricky part that I haven't seen anywhere else: *** I want to line the downhill side of the trench, and the bottom, with a heavy-duty waterproof barrier (like vinyl).*** We'll backfill the trench with gravel and put in a large perforated pipe as well. A layer of landscape fabric will go over the gravel, and over that will be ordinary soil and grass (remember this isn't for storm runoff, but underground creek seep). The main thing I want opinions about is the waterproof barrier. We really want to stop that seep, and this seems to make sense as long as we provide the drainage pipe. What do you think? And do you have a suggestion for what to use for a liner that won't rot/tear over time? Thanks

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pris

I can't address the validity of your "crazy idea". Sounds like it would work but, I'm not an engineer.

But, to answer your question. I think a good pond liner would be what you need. They're made of a durable material designed for use with water. You might want to ask the supplier how well it will stand up to being buried under a layer of dirt and gravel and how long it would take to possibly rot.

    Bookmark   October 10, 2011 at 6:27PM
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noodlesportland

I am no expert at all but had a bit of the same issue. I just do not think the vinyl is a good idea. If you do just gravel at a slight downslope some of the water is absorbed on its way down. If it was my land I would get expert advice before the next step.

    Bookmark   October 15, 2011 at 2:13AM
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aidan_m

The place to put a waterproof membrane is the exterior side of the foundation, right down to the footing. More important, though, is installing good french drains. And most important of all is:

Divert the rain gutter downspouts into a solid pipe, at least 8' away from the foundation, downhill into the creek or into drywells. (the creek may not be the main problem, it could be mostly from the roof runoff.)

The placement of the perforated drain pipe is key. It must be lower than the bottom of the footing. You want to create a low spot in the water table around the foundation of your home.

Water must flow freely without a physical barrier. Geotextile fabric (NOT LANDSCAPE FABRIC)is specifically designed for this purpose: to allow water to pass while filtering sediment. Landscape fabric traps water, vinly traps water, and trapping of water is the problem you are currently experiencing.

Basically do not use vinly or landscape fabric. It will do the opposite of what you are thinking. Talk to a geotechnical engineer. I have 3 close friends who are geotechs; we have experience designing and installing many subsurface drainage and soil retention systems.

    Bookmark   October 17, 2011 at 2:47PM
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