How to fix a Mudhole?

[htiek126]

I have about 5,000 sqft of woods that was a farmer's field about 40 years ago. The top two feet of soil is topsoil mixed with years of decaying leaves, and underneath is subsoil clay that is supposedly about 25' deep. I have thinned the trees greatly and continue to do so with hopes of erecting a pole garage this Spring. There is a lot of surface runoff, and the land is slopped sufficiently to drain the surface.

The problem is the two feet of soil is saturated with water most of the year. How can I drain this water? I have a backhoe and am thinking of installing two french drains at the top of the subsoil clay. The problem is that I am unable to run the 2' deep pipes to daylight, so I would have to pump the water or perhaps drill through the clay layer to drain into the sand layer. I am also concerned that the topsoil with organics is not porous enough to move the water to the french drain because puddles of water will just sit for weeks that I thought should of moved through the soil to a lower portion of the slope.

Any advice? Is there a practical way to change the composition of the soil to firm it up and make it more porous without dumping gravel into my backyard?

 

[Boondox]

I have a similar (albeit much smaller) problem with drainage in my meadow. After checking out the drainage solutions on TBN for a couple of years I found examples in my neck of the woods. I'm pretty much a "show me" sort of learner. In the end I think borrowing a box blade and sloping the land where I want the water to go is the best answer for my situation. No drains or pipes to silt up, no gravel to contend with, and after the initial work no followup care needed.

Pete

 

[theonlybull]

around here, some good ditchs and grading are about the only way to deal with the water. we have similar soil to what your talking about.

when i bought my house, the water ran in the front door, and that wall was a mess. luckly i live on a fairly steep side hill, so i dug the lawn down below the sill by a 1 1/2', then sloped it around the sides of the house so it would drain. everyone said i was crazy, but i don't have any more water problems.

you say the land slopes away, so it can drain, that's all you need. put a small ditch across the hill, at an angle, above where your barn will be. then you may want to run a ditch straight down the hill, along side your barn site. the first ditch will prevent run-off from soaking in, and the second ditch will alow the top layer to drain.

 

[htiek126]

I think the water is coming out of the ground in this area as well. Especially after a rain, there are up flows of water from the ground. I did dig a couple inch deep ditch last year, and it turned into a stream for a month or so until the looze fill it. So a big ditch may do the trick. It will require some solid fill for the walls. That's why I am leaning towards two french drains. If I can get the ground to solidify, then I can get a nice even slope graded for surface drainage. Currently, my tractors submarine in this area until they hit the subsoil clay two feet below.

 

[grandad]

Sounds like you have too much of a good thing! At our place, the lawn goes straight to red clay at a depth of 1"!

I was just browsing a civil engineering web site that had an article on correcting soggy subsoil conditions. Sorry I no longer have the link, but the drift of the article was that permanent solutions can require both removing the water source and replacing the saturated material with suitable aggregate fill. So, maybe the French drains will guide external drainage away from the area, but you still may have to replace the topsoil where the pole building will go since all that organic topsoil is absorbing water when it rains regardless of slope-related flows from other parts of the yard.

 

[Egon]

It would appear you have an area where water is trapped by the underlying impervious clay soil.

One solution would be open trenches with possibly a pond into which they drain and pump water out but where do you pump to? And will the present soil be suitable for a floor in the pole building? Having a pump is always a hassle as they have a tendency to misbehave every so often.

Another may involve removing topsoil and back filling with clay and gravel to above the level of surrounding soil for the pole building site. This will give you a solid dry floor in the pole building.

Egon

 

[GRUB]

I think Egon is on the mark here. To be more specific I would dig 2 drainage trenches starting at about 3 feet deep on the uphill side of your postbarn and extend them downward and encircling the barn site no closer than 10 feet out from the proposed wall margins. Have the trenches end at five feet deep and meet at a common point where you have a large ecavation five or more feet deep, say 6'X6'x6'. Fill all of the trenches and excavation with coarse aggreggate (3" or so). In the center of the excavation put a 18" x 36" drainage tile (plastic culvert pipe with holes drilled into the walls standing vertically with premade concrete lid with handle). The tile top should come to the ground surface and be packed up to with aggregate on the outside but empty on the inside.

All surface water inside the circle and some outside should move into these trenches and go to and fill the excavation. It is possible that the volume of the trenches will handle the water problem without the need for a pump. So dont get one at first, see how it works. If you need a pump drop it into the empty drainage tile and pump away.

Moist clay is very cohesive and will not erode to fill in the aggregate in the trenches only the upper topsoil might need a verticle partition of geotextile cloth to keep sediment from filling in the aggregate. I would not cover the aggregate at the surface. Leve it open. The trench will not need a pipe because it already has a perfect impervious clay bottom. You might want to reduce the size of aggregate surrounding the outside of the drainage tile to act as a filter to the water the pump has to handle. With only one acre I dont know where you will pump it, I am sure neighbors will be a concern. Are you sure you can't daylight the water to a roadside ditch?

 

[htiek126]

I definitley plan to fill the entire volume below the pole garage to the subsoil clay with bankrun and a plastic barrier near the surface.

I have more than a quarter inch per foot slope, and I suspect that a drainage system may move the water to the bottom of the slope efficiently enough to make the top of the slope useable. There is no daylight at the bottom of the slope (because the water/topsoil layer is two feet deep) so I suspect the drain may just have to overflow onto the surface at that point. There is a neighbor issue, however, the overflow will join the surface runoff path and move onto more of the same boggy land conditions. Mysteriously, after another 100 feet, all the surface runoff and boggy conditions disappear into the soil before reaching the houses on the next street downhill from me.

I think my first approach will be to finish clearing the land for the access to the pole garage site (30'x100' with 15 trees that still need to removed), remove the boggy soil on the back 50' of slope, install one french drain 3 feet deep at the top of slope and 2 feet deep at the bottom of the slope that runs to the back corner of the lot with a submerged leach tank as described in the previous post, put down a layer of 8" of bank run on the bottom 50' of slope, replace the topsoil, and then hopefully when the soil will become firm enough to grade a nice even slope for the entire 100'. Then see what happens, note lessons learned, and possibly repeat for the rest of the boggy area.

The tractor is useable on the wet clay, but it is useless in the boggy topsoil. So I plan to start at the top of the slope with removal of the boggy topsoil as required to keep the tractor on solid groun and place bankrun as required to work my way back to the bottom of the slope. I also have several 4'x8' sheets of high density polyeythlene to drive on.

 

[HammerFour]

I had a swampy area in my corral area when I moved in to our new property. The area was covered with 4 - 6 foot tall weeds and was pretty marshy. I noticed after keeping the weeds cut and seeding some grass this year, the area has firmed up quite a bit and isn't soupy at all. I guess this is due to the sun being able to reach the soil to evaporate moisture, and also the grass using the moisture that is there to grow.

 

[Currmudgeon]

If you can't daylight your french drains or ditches, then you don't have drains. Pumping will eat you alive in terms of perpetual pumping costs and won't handle the volume of stormwater that a moderate rain can produce.

Your best bet is probably to undercut the unsuitable material down to solid clay, put down a layer of geotextile, and backfill with good, soild clay, well compacted, or crushed aggregate material, also well compacted.

Place the backfill in six inch lifts and compact it well. You may want to rent a vibrator plate for that. If you're placing clay, pay particular attention to the moisture content. Some clays compact well at one moisture level, and get mushy if you add a bit more water. Some experimentation may be in order, there.

If you can, grade around the barn site to carry runoff away from and around the site. Having the barn a little high makes it easier to keep dry. I try to maintain 2% grade, minimum, on dirt or grass. That is 1/4 inch fall per foot of run.