Custom French trench drain design for specific soil & flooding
I live in rural CO and have a mix of silty fine dirt and clay in my yard. I get some standing water in this portion of my yard during Spring snow melt and flash rains. I also get some of this water (only 1″ standing in 1/5 of area) minorly in my 50 year old, 4 foot high crawlspace. It travels under the footer which is about 48 inches deep and 10 feet away on the same side of the home where I have room to put the trench, same side the yard water stands.
So I was going to install a 12 inch wide trench drain designed as such. Please tell me if I’m missing anything or need to consider others. Thanks!
For 55′ long trench dig 24″ deep at beginning point and be 32″ at deep at outlet.
Mark all utility lines with bright tape, sleeve them with hard conduit if possible, or bind small pieces of smooth metal protection around them (as safety shields), and extend flags up above the surface, which my dogs will likely pull up promptly, lol.
Place 4.5′ wide (at minimum) permeable landscape cloth down the bottom and lay it across and out of the sides. The extra will be used to fold over each other on the upper layer of gravel.
Place 8″ deep of 1″ to 2″ round washed river gravel down the bottom of trench.
Place a 45 or 90 deg threaded (for top) elbow at the high end for inspection and cleaning. Outlet end should ideally reach daylight but if not possible then a large enough collection hole filled with rocks. If exposed to sunlight pipe should be screened to block pests.
Drill a pair of 1/2″ holes every 6″ down the 4-5″ dia pipe, slightly offset (about 1″ away from the center of the bottom). Or use pre-drilled pipe if available.
Lay the pipe in the ditch on top of the 8″ of gravel. Check it’s slope again.
Do NOT permanently cement PVC joints except for the elbow joints. Wrap with plastic wrap and duct tape. This is so I can pull them up hassle free if needed.
Place another 6″ of gravel over the pipe.
Lay the landscape cloth over from both sides.
Fill the remainder up with gravel to surface.
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Replies
Andy,
Nobody drills holes in solid pipe to make perforated pipe any more. Buy the perforated pipe.
Your specs are fine. I haven't seen 5" pipe -- your choices are probably 4 inch or 6 inch pipe. Buy the 6 inch pipe if you can afford it.
I don't see why you want to bury the pipe that deep -- although you can if you want. Deep pipe is harder to dig up and fix if there is a problem.
Another approach is to put a plastic catch basin in the center of the wet spot -- and then install drain pipe to daylight from the catch basin. The first 10 feet of pipe can be perforated if you want, and the rest solid. That way, your pipe is buried about 8 inches to 14 inches near the catch basin -- with deeper pipe (for slope) at the drain end.
Thanks. I was going to utilize some solid 4" PVC and joints I had on hand...thus the drilling.
I'm wondering if I even need pipe. The water is slow to accumulate over several weeks. We have a few weeks of repeated freeze-snow-thaw-freeze-snow-thaw, etc. The soil is high clay near the top so it gets trapped in a 700 SF (25' x 30' rectangle) low area and then seems to saturates the soil and slowly makes way to my crawlspace about 20' away. I am placing the trench just inside that low area about 15' away from my house.
So I think I may have soil saturation problems that come from the surface clay and also possibly soil water from water table pressure. So I'm planning it 24"-32" deep trying to attract as much water from both sides as I can and dumping it down hill about 25' from house corner.
Ya think just the landscape cloth encapsulating the 1-1/2" to 3" creek gravel would be fine for that and the few/short hard rains I get? I'm not covering the top gravel with anything, but a dual layer of cloth will be 6" under surface.
Is it possible to regrade so the water drains away from your crawlspace? If not, could you use grading and a swale to channel the water? Either option might be simpler and cheaper. I've installed a few French drains, and they can be a PITA to get right. Plus, most drains silt up eventually (which is why you don't want them too deep).
No I have no room on that side for any other options. Has to be some kind of drain tile I'm afraid.
You can sometimes solve a ponding by installing a bog garden--if you are into gardening.
Can't. There's stuff and a trail I have to access right on the other side... And my Propane tank. I'll probably take the trench cut and try to make some elevation change somewhere to steer runoff to trench though. I'm just unsure if I really should waste $ and time leveling a 4" PVC pipe into middle of the gravel, or just make the trench encased in landscape cloth and fill it all with smooth 1.5 to 3" river gravel. The volume is not high, it just builds up and doesn't go away fast enough because of clay and saturation, so I've observed. From my understanding the pipe is important for fast moving and lots of aqua flow.
Andy,
The drain rock alone will probably work just fine. Perforated pipe would be good insurance, but if you don't want to spend the money you can always try doing without it, and if the rock proves insufficient, dig it ups and add the pipe.
Yeah I could use just rock and if needed put a pipe in shallow later like Martin suggested. Just under the surface, covered with maybe 3" gravel for the infrequent hard rains. Using just rock is simpler for a few hours prep and material.