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I have a new construction home and the backyard grade needed adjustment late in fall. There is an area that meets in the middle that doesn't really hold static water above, but the ground stays soft and muddy in this area for a few days or more longer than the rest.

It originally had seed laid in the back over the summer and then late in the fall after adjusting the grade.. front was sodded so due to size of yard, and time of year everything was done I only had time to focus on the sod in the front while it took in 90 deg weather with no rain, so backyard went to hell. I am adding sod this spring, will the sod depth raise this area enough, or the fact of grass actually being there to absorb the moisture help? Or do I need to add some more dirt?

Pic below:

Troubled area circled. Well, the whole thing should be circled but the area with possible drainage issue :)

Backyard

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First might I say..wow that's a big back yard.

If it is a new home I'd get the builder to take a look. If it's heavy clay you, or they, may need to add a drainage trench, filled with rocks, out to the lowest point on the property line (Not the neighbors yard), then covered over with soil and turf..

I would not be too tempted to raise that area though. You want to keep the water AWAY from your house. The soil around the house will also settle with time so the higher it is there now, the better.

  • Thanks! It's a corner house, so the front yard and side is almost as big, hence why I couldn't keep up with the back to when taking care of the sod! so the drainage trench is basically a ditch dug down and filled with rock, and the soil just goes over it? Also, the grade seems to pitch to the corner so, I would imagine it would end there, but I do have a neighbor and will have one behind me in the future, how do you prevent water going into their yard, does it just depend on the depth of the lowest point? Thanks! – eaglei22 Mar 7 '17 at 18:23
  • Hard to say from the pic. It looks like that far corner is lower than the hollow though so a trench that ended before the fence there would suffice. It would run off in that corner anyway. You just do not want it to appear to be an obvious "Here..you deal with it!" solution. But the builder can probably fix the grade to there just as easily. – Trevor_G Mar 7 '17 at 18:29
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It sounds like you have what geologists refer to as an aquatard in your back yard. Aquatards are layers of earth that are impermeable to water, such as bedrock or clay, so instead of soaking into the ground the water flows over the aquatard. Swamps in rocky mountain regions are typically a result of aquatards.

It sounds to me like you may have a layer of earth behind your house that the water cannot penetrate. This is typical in new construction zones because the diggers come in and scrape away all of the soft soil when they are levelling out the property, exposing the layers of clay beneath.

My guess is the wet area you're referring to may be the path the water is flowing through from the higher parts of your yard. It stays wet longer because after the water soaks into the ground upslope from that spot, it hits an aquatard, then flows through the soil until it can either get over the aquatard, or it finds a way back to the surface where the sun can soak it up.

What Trevor suggests is correct. You need some drainage ditches for the water to flow through underground. My grandfather built a campground on a swamp by a lake years ago, and dug multiple ditches in the mud and muck that all lead to the lake. The highways department was blasting a rock-cut for a new highway nearby, so he made an arrangement with them to dump the rubble they were trucking away into the ditches he'd dug. The once-was swamp is now a beautiful dry campground full of tall trees. The water that was filling the swamp now drains underground all the way to the lake.

  • I live in the midwest, and yes the clay is very dense not more than two feet down. I know, because I attempted a few holes by hand (near power cables) for the fence post holes. So what you and Trevor are getting at is probably correct. What type of rock is used and how far down usually? Is gravel too small? and how deep of rock is needed. never had to deal with this before. Thank you. – eaglei22 Mar 7 '17 at 21:34
  • The size and type of gravel you use will make a difference. Crushed stone has a tendency to pack and settle and fill in all the gaps. Round stone however never fits tight together, so water can easily flow between all the stones. See this: smithbrotherstreeservice.net/exterior-drainage-systems.htm – ShemSeger Mar 7 '17 at 22:55
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    An "aquatard" is a much more desirable thing compared to a natural spring. It's good to see that you have enough yard for the water to drain away from the house. I imagine the grass seed will help alleviate some of the water build up, but if grass cannot keep up with it, I would suggest french drains across this area to move the water to an another spot where it is more permeable. – Scott Ramboz Mar 8 '17 at 15:21
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    @eaglei22 Something you could consider too is augering through the clay layer and filling it back in with gravel. If you can get through the clay into a permeable layer, then this hole would act as a drain and allow the water to flow through and soak into the ground beneath. – ShemSeger Mar 8 '17 at 15:49
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    If there is an impervious layer of either clay or limestone, could one drill a hole through the impervious layer, fill the hole with gravel and coarse sand, then cover with sandy loam on top. This would provide a drain for the trapped water. – Jim Stewart Mar 8 '17 at 16:08

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