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tl/dr: I have a large sandy pit where I have to put the entrance for a yard/french drain. I can't remove the sand. I'll be building a deck on top of the sand pit, so I can't just "replace" it with grass to avoid erosion. So, how do I keep the sand from clogging my drain?

I'm dealing with some water that got into my (theoretically) water-proofed basement. After some experimentation, it looks like the bulk of the issue is that the previous owner flattened part of the yard for a pool, making it easy for water to reach the house before it runs off the (sloped) property.

He mentioned at closing that it took a ton and a half of sand to get the area flat enough for a pool. Sigh. Keeping water away doesn't require anything crazy - I created a small trench with a small berm near the house, and even in some heavy rains, the ground around the house has stayed dry.

So, now it is time to make this more permanent. My plan is to dig a deeper trench (although still not crazy deep - hopefully just 6-12 inches), and put a pretty standard french/yard drain to pull the water away downhill. The issue is that the main place the water collects, and therefore the "start" of the drain, is in a large sand pit. I'm worried it will be very easy for the sand to get in the drain and clog it regularly.

Also important:

  1. It's a lot of sand. I don't want to try to remove it all. Way too much effort/cost
  2. I'm going to build a deck on top, so lawn/plant stabilization won't be a possibility.

I'm thinking I'll just end up putting some sort of tarp/landscape fabric down to cover the entire sand pit, build the drain on top, and then put the deck over everything. Is that reasonable?

The sand pit. For reference, the ground slopes down behind me in this picture. The neighbors yard in the background of the picture, as well as my own yard off to the left, flow towards the sand pit. This is the source of runoff that is causing me trouble.

enter image description here

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  • That looks like the perfect ground design to flood a house, plus nice chickens. Should have that slope fixed so all water flows away from the house before doing anything else. Will want the ground to slope away from the house and drain, probably away to the bottom of picture, make sure to bake neighbours cookies.
    – crip659
    Aug 28, 2022 at 21:09
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    Yeah, my goal is to get the ground around the house down an inch, and then slope that down another 2-4 inches into the center of the sand pit. Believe it or not, this is a relatively localized problem. Only part of the neighbor's yard drains to here, and most of my back yard drains away from the house. It should be fixable without a huge earth moving project. There's a stream about 50 yards behind me (and it's a good 5-6 feet lower) that runs into a lake, so the water really doesn't want to bother my house. The last owner just chose the wrong spot for the pool.
    – conman
    Aug 28, 2022 at 21:56
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    Fortunately for me, the owner paid for their mistake. They ended up paying like ~$5000 for a complete basement waterpoofing. There's a french drain around the entire basement floor that goes to a sump pump, so with the pool gone and a more permanent run-off control system, I don't expect to have any problems long-term. We had a storm the other day that dropped 2-4 inches in an hour and the little bit of runoff control I already put in place was enough to keep my basement dry. Only a couple gallons of water reached the sump pump - I measured it because the pump died :)
    – conman
    Aug 28, 2022 at 22:03
  • Once you fix the slope, you can sit back and enjoy your eggs.
    – crip659
    Aug 28, 2022 at 22:06
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    I'd loose the sand. A ton and a half of sand is less than 2 cu yards (about 1/5 of a dump truck load. You could rent a dump trailer and either get some inexpensive workers to dig it out or rent a mini-excavator to dig it out. You could possibly find somebody to take it for free or maybe even have them come and dig it out for free as long as the got the sand. Make sure the ground underneath is now sloping away from the house, put down landscape fabric and fill with crushed rock. Then a french drain on the left, daylighting to a low spot on your property. Aug 28, 2022 at 22:26

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Filter fabric (not tarp, not landscape fabric) should work fine to keep the sand out of the pipe.

This does not seem like it should be a huge deal, you can even buy drain pipe with filter fabric preinstalled (costs more than it's worth last I looked, though), or "pipe socks" to apply to your pipe.

Wrapping a roll of flat fabric around the pipe, or around stone fill around the pipe is also quite easy. And unlike clay, sand is easy to stop.

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    I haven't had good luck with Pipe Socks. They tend to clog right where the openings to the drain pipe are. What I have had good luck with is lining the the entire ditch, top to bottom on both sides with one continuous piece of fabric, all the way down one side, across the bottom and up the other side, then put in the perf'd pipe in and cover with drain rock most of the way, leaving enough for some top soil. Drape the fabric over the top of the drain rock before putting in the top soil. That way you have a TON of surface area in the fabric. Aug 29, 2022 at 1:49
  • @GeorgeAnderson In clay, I'd agree. In sand, should be fine either way. The sand itself, (if not allowed to flow into the pipe) serves as a filter layer and flows water through it easily.
    – Ecnerwal
    Aug 29, 2022 at 12:34

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