Water Drainage issue in the Low country, am I crazy? 1

[JWM81274]

I have recently purchased a house in Charleston, SC. and the low country name says it all. My yard is basically flat with a few low areas but the problem lies in the entire yard. 5 Days after a descent rain the yard is still soft.(i.e. sinking when you walk on it) I being an engineer, have come up with the following solution. I am planing on installing a french drain system but with a few twists. First because the yard is relatively flat I am planning on removing the entire yard and installing a drainage level(gravel/corse sand and two layers of geotextile sheeting, 1 above and 1 below) across the entire yard with perforated pipes crossing throughtout(with the appropriate slopping 3" per 50'). The yard is only a 70' by 35' plot including the house making the area to be removed a 35' by 40' section and two smaller sections. The reasoning being that to cover the area with trenchs would cover almost the entire yard anyway and living in a neighborhood doesn't allow for me to just slope the yard to allow drainage. The first twist is how to get rid of the water once it is in the drainage system(allowing for the right slope I will be 1' below the road gutter). A pump and a reservoir will be used to collect and remove the water to a gutter in the street. With this is mind I came up with twist number 2. Why not store rain water for use in a sprinkler system when it doesn't rain from June through Sept? Knowing that a tank to hold that much water would be impossible I am limiting the tank size to around 200 gl. The sprinkler system will have a city water option as well. The issue with this is, were to put a 100 gl tank? Solution: under ground in a concrete watertight(hopefully not a pond;oP) pit to allow for maintenance on pump, tank and sprinkler system. Am I waaaayyyyy overshooting here? I am what you would call a "jake of all trades". I have done a lot of differnt things in my life encluding running heavy equipment so I will be using a track skidsteer to remove the soil. The thing is I am very picky when it comes to things I own. I want people to be, not trying to sound snobish, envy of what, not just of what I have, but of what I can accomplish once I put my mind towards a goal. My coleges are taking bets on how far I will go before I stop and give up which will not happen even if I have to sell my truck to pay for the project, well maybe not that far. Any suggestions? Your comments are appreciated.

 

[Focht3]

(As I contemplate your planned course of action, the phrase, "He has more money than sense" is coming to mind...)



Where did you live before moving to Charleston? Why are you so picky about a spongy yard?

Do your neighbors have the same problem? If so, is it due to a pine straw thatch buildup? Are you dealing with St. Augustine grass, or some drought-resistant turf?

If your neighbors don't have the same problem, are their lawns "higher" than yours - probably because they have added topsoil to their yards over time?

Your solution (to the spongy yard) sounds kinda drastic to me.

On the water storage front: your "cistern" system will be more trouble than it's worth. Go to your local hardware store and look at sprinkler head flow rates; I think you'll find that 100 - or even 200 - gallons of rainwater won't give you more than a one time good 10 to 20 minute lawn watering.

If it were my money to spend (which it isn't), I'd go for something really useful in my front yard, like a family of plastic pink flamingos, concrete elves, or plastic deer. Hey, how about a frog pond?

 

[JWM81274]

Before Charleston I lived it Atl. Ga with no yard and before that I live in Ohio in an old farm house were the nearest neighbor was 3/4 mile away. In Ohio the ground was slopped enough so there was no standing water.
I wouldn't say I was picky, it is just after 5 days of sunshine I still can't mow the yard. The thing is I just don't want to ignore the problem like everyone else. And it is the first house I purchased.
This is a common problem in the area. The grass is more weeds than grass so a re-sod is needed anyway. Talking to the previous owners they resodded last year in the back and now it is just a mud hole. I think the cause for the spongy yard in the front is the water has nowhere to go. The yard slopes toward the road way but the concrete curb doesn't allow the water to get there. I was going to gather the water then pump it through the curb (cutting a hole in the curb). The back is just low. If I build up my yard it will just run water to the neighbors yards. Which isn't very nice. Although one neighbors does have a very annoying dog.
The water storage system was for just getting the water somwhere I could pump it. The cistern was an idea to allow for changing filters on the pump and to monitor the tank.
I didn't know that a 200 gal tank would only do a single watering. Thanks, on that.
As for the yard obstacles, that isn't really my style. But I do have an awesome little gas power RC truck that loves the yard as it is.

 

[jheidt2543]

I have to say, I think you are a little overboard too.
My guess is that the problem might be a heavy clay subsoil not allowing the rain water to perculate through the soil, thus it stays wet and muddy for days.

I would offer two thoughts:

1. If you are going to re-sod anyway, then why not regrade the subgrade and truck in some new topsoil to help with the new grading. You might be able, with grading swales and berms, to get the rain water to drain to a pocket area. Put a large french drain in the low spot of the pocket and let the water perculate away. This will depend on the thickness of the clay layer, but you could bore a 24"-30" diameter hole down to a gravel layer, fill it up with washed stone and top it off with a concrete pipe section set vertically and a grate on top.

2. Talk to a landscaper in the area for some suggestions. If this is a common problem in the area, then you are not the first to face it. Perhaps a local landscaper has some solutions to offer. Having seen the site often brings solutions to light that can't be suggested over the web.

Good luck!

 

[Focht3]

jheidt2543 is right - check with local landscapers for other ideas. A good suggestion.

I hope you weren't too annoyed by my previous post; but you really tickled my funny bone!

Pumping will work; even a "zero slope" drain from back to front and through the curb will help (which is what my parents did in Houston, which is also quite flat and receives lots of rain.) I don't like "french drains" in clay soils; the gravel plugs as the clay migrates through with the water. Generally speaking, an area drain in a "depressed" area should be sufficient unless the first few feet of soil is very silty or very sandy. If you really want a french drain, use concrete sand (or play sand from the hardware store) instead of gravel. But if you choose not to raise site grade, put a small berm around your yard; after all, you don't want to provide drainage for the whole neighborhood! (And without the berm, your yard might never dry out in spite of your efforts...)

 

[GeoPaveTraffic]

One potential problem with your idea is the "(cutting a hole in the curb)". This could effect the street and the local public works department might not like it. In addition to checking with a landscaper (which is a very good idea) you could also check with the local public works department or soil conservation office.

Good Luck.

 

[gibfrog]

Welcome to the "Poorly Drained Coastal Lowlands". Your best answer is probably one of two options, although other options are possible, you really have not given us enough data to properly evaluate your situation. Just remember, WATER FLOWS DOWNHILL.

1) If you finished floor and garage elevation is high enough, then strip off the old lawn, regrade with sand and sod. A 8" drop from your finished floor (6" is also possible, but I would not reccomend 4" or less) to finished grade around your foundation. Then grade your lawn to the back of curb at a minimum of 2% slope but no more than 8%. (Of course you can grade your lawn at 0.1%, but this will retard more water i.e. the sheet flow will build higher before it rolls down hill, it will flow slowly and be very sensative to minor leaf/debris accumulations. You could always steeper than 8%, but this can becomes more of a bank slope, not a lawn for general use, especially at 25% or greater). The prime advantages of this solution are it is the "natural solution" and probably exempt from regulation. (This was probably the platted drainage solution, you must check your subdivision plat, However, in older subdivisions, no such luck.

1-B) Minimize you problem by guttering your roof directly to the underground street piping if possible. Minimize it even more by installing some yard drains (check out Advanced Drainage Systems, for example) and connecting them directly to the underground street piping if possible. You will probably need a permit.

2) Grade your lawn to a low spot and use a 1/4-1/2 hp automatic sump pump in a prefab tank. Pump to or through the curb. YOU MUST OBTAIN A ROW PERMIT. Your pumping rate will be limited to a rate that does not cause a spread of flow that creates unsafe driving conditions or limited to a rate determined by your local land development regulations. The low area should naturally overflow to the roadway, so when a hurricane hits and you lose power, you will not flood yourself or your neighbors. Your local pump distributer may be helpful also seek input from the roadway drainage engineer. You will need to calculate the size of your tank, your pumping volume, your design rainfall, your spread of flow in the street gutter, etc.. You will need permits and this will cost money to continually operate and maintain.

3) Subsurface disposal - If you can easily breach your shallow clay to deeper sands or gravel THAT ARE NOT PART OF OR CONNECTED TO THE DRINKING WATER AQUIFER, then by all means, drain your lawn to a gravel filled pipe than flow down to the layer. You need to verify the permeabilities and consult with a local soils guy of your local USDA NRCS office. You can also pump to this subsurface layer, a shallow injection well system. This will require many various calculations and some geotechnical test data.

4) Lighten up, and just learn to enjoy the feel of mud squishing through your toes when it rains and for the week there after.

5) A lawn is truly a waste of space. I hate my lawn, it needs to be mowed year around in Florida. However, concrete nevers needs to be moved, sheds water very rapidly and is never spongy when properly installed. If you do not want to concrete your whole lawn, plant wetland plants, like Canna Lillies, spearmint, etc.. in some low spots. Alternate B - Xeroscape your yard with river rock and herbicide. Just keep adding rock until you yard stiffenns sufficiently.

Best of Luck....

Clifford H Laubstein
FL Certified PE #58662

 

[johnhan76]

ONe of the problems with the infiltration trench/french drain in the low country is that it will quickly fill with groundwater. Often times the groundwater is less than 1' from natural ground.

 

[JWM81274]

Let me update my present situation. At present I have removed about 24" of soil from my front yard. The soil was very sandy. There was dry/more solid ground at around the 2' mark. I was going to just reslope but while removing some of the top soil I got the tracked skidsteer stuck. I then decided that in order to not make a big mess I would remove dirt untill I found something to build on. Which lead me to 2'. The hole was mostly completed late Monday afternoon. I was in the process of checking elivation for the french drain when a torrential downpour made me retreat to higher ground. I have in seeing the pond form before me that a later month when the chance of rain is slim to none would have been a better idea. The rain has stopped only briefly. Letting me get my pump out and drain half of the pond before returning. I have sence though of how a concrete yard would look as someone mentioned, even thought about pink flamingos. Tomorrow jundgment day will begin. Rain or shine the perforated pipe will be placed and soil will begin to be put back in the front yard. The back yard will have to wait on a dryer month. Thanks for the help.

 

[jheidt2543]

JWM81274,

I don't believe pink flamingos can swim, I would suggest either Canada geese or Pellicans depending on which part of the country you are in. In fact, if you were to plant wild rice, you might be able to rent out blinds during the hunting season. <G>

Good luck!

 

[Focht3]

I vote for wild rice - you get something useful even if you don't get any game birds (as opposed to the &quot;birds&quot; from your neighbors!)


A two foot deep hole shouldn't be a problem for pink flamingos. According to Brittanica Online, they're 3 to 5 feet tall and have webbed feet. The live ones, that is. The plastic ones can be spliced ad nauseum...

I do have sympathy for you. Eight years ago my wife and eldest son decided that our two youngest children (then 3 and 1) needed a gravel play area next to the house. They laid it out and began framing it with landscape timbers while I was out of town. The area is sloped and about 17 feet by 26 feet; it took 40 tons of 3/8 inch gravel to fill it up! I spent a whole damn week of vacation using a bobcat to haul the gravel - 1/4 yard at a time - and fill it up. Back yard has veneer of clay over limestone; and it rained almost every day. My driveway (which tilts and slopes) was coated with wet clay and slippery as hell. Took me six 12 hour days to complete it. Some vacation.

 

[mark777]

Another thought on storing the water for later use. It might get very nasty before you use it since it isn't being treated (such as chlorination).

If the area is very flat, it might be difficult to accomplish very much since the neighbors' yards will drain right into your nice new drainage system. You'd possibly have to build some sort of sub-surface barrier around the entire perimeter.