# Dry well design for low spot in yard



## Badfish740 (Oct 29, 2006)

The back corner of my yard has always been a problem. My entire 1/4 acre lot is a gentle slope toward the southwestern corner. This coupled with a layer of heavy clay right underneath the topsoil makes for a swamp that only dries out in the dead of summer. Since I have neighbors behind and on both sides I can't dig a ditch to drain it, so I'm contemplating an underground retention basin or dry well to give the water somewhere to go below the surface and then hopefully, slowly dissipate into the ground. Here is what the spot looks like now.

Looking south:










Looking west-the hole you see is about 2' deep, dug with a hand auger. I wanted to try to get a feel for the soil. After about 8" of topsoil it's nothing but nasty red clay with bits of rock mixed in. I couldn't get any further with the hand digger after 24". As you can also see, my next door neighbor has a 10x10 shed on a slab right in the same area-curiously he has no drainage issue on his side at all. The neighbor directly behind me does, but his property slopes to a drainage ditch along the road in his front yard so at least he has that option.










Looking southeast toward the rest of the yard-you can see the change in the grass which corresponds with the level of wetness in the ground. Basically the wet area is where it's perpetually green:










As you can see its basically a mudpit. Its impossible to mow (I usually go in there with the weedeater) and its pretty much unusable. The dog loves it of course  Anyway, I'd like to reclaim it by eventually putting down a layer of stone and moving the firepit, picnic table, etc...back there, but until the drainage issue is addressed, I can't do anything. Here's the plan:

Basically I'm planning on creating a large volume of space underground so that the water can percolate down through the topsoil and a layer of rock, into six barrels. My hope is that the volume will be large enough so that after a good rain the topsoil will be dry, and the water will have drained down into the barrels below, where it can slowly work it's way into the soil.

I'd first start by renting a small excavator and digging a pit in the back corner of the yard, about 7' long, by 5' wide, by 5' deep. Once the pit is dug, I'll line the bottom and sides with landscaping fabric. This will keep water from washing dirt into the rock and clogging it. After lining the pit with fabric, a 6" layer of 3/4" washed stone would be spread on the bottom. On top of the stone bed, six 55 gallon polyethylene drums would be placed in two rows of three. The drums would be perforated with 1/4" holes on the tops, bottoms, and sides with the goal being to create as many openings as possible without seriously weakening the drum structurally. Once the drums are placed, the hole will be backfilled with 3/4" washed stone so that the drums are surrounded on the top bottom and sides by a 6" layer of stone. Once 6" of stone is placed on top of the drums, the stone would be covered with landscaping fabric, topsoil, and sod. Here's a crude rendering I came up with:










My gut tells me it will work, but I'm putting it out for a sanity check. The one caveat I think of is that I'll have to treat it like a septic tank/field and never drive over it, but I don't usually take the truck back that far in the yard anyway, and as I said, the plan is to make it an outdoor picnic area long term. People around here commonly use poly barrels as drywells for their downspouts, and underground protected from UV rays they should last forever. Thoughts?


----------



## Daniel Holzman (Mar 10, 2009)

Unfortunately it is not quite that simple. If you are truly on clay, you will get virtually no exfiltration from the tanks. They will simply fill with water after the first decent rain, and remain full indefinitely. The next rain will puddle on top as it does right now. If you can set up a pump to pump the water out of the barrels and away from your property, say down the street or into the storm drainage system, that would work very nicely.

I have a similar issue in my backyard, I have a low swampy area. In the Spring and sometimes in the Fall, it fills with water, and remains full of water sometimes for weeks at a time. I could dig a hole in the swamp, but all that would do is fill with water and remain full. I simply live with it, there are a few interesting creatures that like the wet area, and a few plants that tolerate it. If I really wanted to drain it, I would have to pump out to the street.


----------



## cibula11 (Jan 6, 2007)

Why not do something easier/simpler like a rain garden. It won't solve the problem entirely, but it'll make a swampy mess less of an eye sore and more of a focal feature in your back yard.


----------



## Oso954 (Jun 23, 2012)

If I were doing it, I would go with a sump pump basin with a permanently installed sump pump. I would pick a out of the way location for the pump basin.
Run a drain line through the wet area with it sloping to the sump. Then pipe the pump discharge to the street, or connect it to another existing drain.


----------



## Bondo (Dec 8, 2007)

> Anyway, *I'd like to reclaim it by eventually putting down a layer of stone and moving the firepit, picnic table, etc...back there, but until the drainage issue is addressed,* I can't do anything.


Ayuh,.... Build a stone bridge right over what's there,....

Roll out marify paper, 'n spread a layer of 4" crushed rock, compactin' as ya go,...
Then 2" crushed rock,.... then 3/4(-) crushed rock,.... compactin' the whole time of course,...

An 18" thick stone patio would hold up a good long time,....
The fabric will keep the mud from pumpin' up,...

It appears you've got plenty of fall to make it work, 'n a side benny would be divertin' the neighbor's water to the other neighbor, by-passin' yer yard,...

If ya wanta do the drywell too,... 
Skip the barrels,...
Dig the hole, line it with fabric, 'n backfill with 4" rock, no fines,...


----------



## DexterII (Jul 14, 2010)

An unfortunate situation that a lot of homeowners deal with, but I don't think that you are going to be any ahead with the barrels. Not that I have the answer for you, but just hate to see you go to all of that work and be disappointed with the result. Here are a few numbers to crunch; there are 43,560 square feet in an acre, meaning 4,356 square feet or 627,264 square inches in a 1/4 acre, and there are 231 cubic inches in a gallon. Do the math, but, any way you slice it, assuming that your entire yard is sloped to that corner, those barrels are going to fill up with any measurable rainfall. And, by having that water in buried containers, you will be eliminating the element of evaporation, which, although it may not seem like it some days, is significant.


----------



## Oso954 (Jun 23, 2012)

> Here are a few numbers to crunch; there are 43,560 square feet in an acre, meaning 4,356 square feet or 627,264 square inches in a 1/4 acre,


4,356 is 1/10 of an acre, not 1/4. That makes the square inches wrong as well.


----------



## DexterII (Jul 14, 2010)

Oh yeah, you're right! The square feet and inches are for 1/10 acre, so probably close to the equivalent of the back yard alone, less the front and the house. Sheesh! I wish they'd take these darn computers away from us old folks who can't remember where we are from one second to the next. Thanks for catching that!


----------

