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I am planning some landscaping which would see the addition of a small garden in my yard. On two sides it would be surrounded by a crushed rock barrier strip 1' wide. I was hoping to use this 1' wide strip as a psuedo-drywell for the french drains I plan to install.

I don't have major problems with drainage, so the french drains are more for the efficiency of moving water from hardscaped areas to cultivated areas. As such, I don't need, nor do I want, a proper plastic tub buried anywhere.

My plan would be to dig a trench for that barrier strip. It would be 1' wide, of course, and 3' deep. I'd line the sides with landscaping fabric, or some permeable liner material, so water can pass through but soil remains confined outside the trench. Then, I'd simply fill with large crushed rocks to create a porous space for water to accumulate.

Because I haven't done this before, I would like to know if this plan seems reasonable, and what I could do to improve it.

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First, you do not want excess water to go to you cultivated areas. Excess fertilizer collects and whatever that you don't want willy nilly to be in your cultivated plants, esp. food crops.

A dry well does NOT mean a plastic tub. In fact that negates the purpose of a dry well. A dry well is a big hole, lined with landscape fabric, filled with DRAIN ROCK, round river cobbles, not crushed rock that compacts. On top of the drain rock is another layer of landscape fabric which of course keeps the soil out of the well while allowing a place for water to collect and slowly percolate into the water table (filtering water through the soil collecting chemicals). It is an easy way to 'fix' drainage issues the developer and contractor ignored.

French drains are far smaller and conduct water TO dry wells or daylighted outlets (not in suburban areas) and not to your foundation drains or city sewers. You NEVER WANT any water to drain towards your foundation ever unless meeting a large swale to be carried around the foundation. And not to your neighbor's yards, grins. They are made of perforated pipe covered by landscape fabric with a slope to collect and carry water from the surface to a proper area. They are also done with drain rock, not crushed gravel unless beneath the pipe. There are expensive french drain pipes with 4 or 5 smaller pipes one atop the others with inherent fabric, plastic sponge to keep the holes from filling with soil. Only need a 6" wide trough on top of crushed gravel with drain rock around the pipe.

These are usually designed in a herringbone pattern to collect and drive into a main pipe towards a dry well.

I hope this is helpful. Let me know if you need clarification. Don't forget slope for these pipes; at least 2 to 4 %. Use Rise/Run = Slope to figure.

  • Fertilizer shouldn't be an issue. As for the plastic tub, I am referring to specific products that act to contain rock (my bad in specifying crushed rock). In any case, it seems that, aside from a few changes to the plan regarding trench size and which rocks to use, my plan is acceptable? – Hari Ganti Apr 1 '17 at 21:50
  • Yes, I'd need to see a sketch but it sounds like you know better than most what you are doing. Dry wells are such a great great bandaid for bad grading and drainage. We have flat land so boring but dry wells are saving us from rot and mildew. Hope this helped! – stormy Apr 2 '17 at 0:40

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