I’m planning on building a retaining wall right beside my driveway. I’m concerned that if I dig the suggested 6-8 inches below ground to place a gravel base that all the water from the hill will run behind the wall and under the driveway. So I’ve been told to put a French drain down there, but since the driveway and wall are at the bottom of a hill, there isn’t anywhere to drain the water… the pipe would be below the driveway. Any suggestions?
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Then build the wall as has been been suggested, but we'll modify the drain. Get yourself some 2" PVC pipe and some 1/4" hardware cloth. At a level 6" above the driveway surface, every 6 feet, install a piece of this pipe long enough to extend from the front face of the wall to a point about 6" beyond the back of the wall. Make a screen with the hardware cloth and cover the end of the pipe at the back of the wall, and secure it so it won't come off. Fill the area behind the wall with good gravel to a point 3" below the bottom of the pipes (let's call them "weeps") along the entire length of the wall. From that point to a point about 12" above the weeps, fill that area with clean, washed 3/4" crushed stone, again, along the entire length of the wall. If you can afford it, wrap the crushed stone in whatever filter fabric you can find at the home improvement store. That will help keep the fine particles of the surrounding backfill from contaminating and filling the voids in the crushed stone. Then backfill the rest of the way with the same good gravel you put below the weeps. These weeps will be the drains for any water behind the wall to drain out onto your driveway and on its' way to the street. The crushed stone be the conduit behind the wall to get the major part of the water to the weeps. Any water below that level will be small and likely to infiltrate into the surrounding soils.
[This message has been edited by treebeard (edited April 18, 2003).]
