yuck? garden box above septic field?

[denemante]

Hey all - we have a septic tank with fields in our backyard. But the location of the fields would be the perfect place for a garden because it gets all-day sun. I believe the fields are down 30" deep per local code. For those unfamiliar, the fields are like an array of large underground pipes, effectively with holes in them, where decomposed liquids eventually leach out into the soil, which filters it away safely.

Just for peace of mind, I'd ideally like to separate the bottom of my garden box from ground it would sit on unless somebody suggests otherwise.

Of note, this whole area is on a slight grade and there's never standing rainwater on the surface. So highly doubtful that even if my septic fields failed, liquids would rise to the surface.

I may have one giant box, or a bunch of smaller boxes. I plant to grow anything and everything I can - tomatoes, corns, peppers, veggies, peas, squash, zuc, etc. etc. Perhaps even some melons.

Thus, I'd want the box deep enough where I could plant things that might grow deeper roots. So that's really my question. I first thought about lining the bottom with plastic - but then I'd probably have drainage problems. Then I thought perhaps I could put layers of stone or sand at the bottom. But I'm unsure if (and in a worst case scenario) that might still allow something from the ground below to "wick" up into the garden. AND - perhaps that' not even needed. Perhaps if my box is 18 inches deep, nothing I'd ever plant would grow deeper roots than that (thus "reaching down") into the actual ground area. And I'd think gravity would seem to send water down, not up.

Anybody done this or have any thoughts?

[tomc]

I would not grow root crops over a septic field. I would trellis crops that might otherwise lay on soil.

Raised beds built as free standing tables no matter what their size are going to be too heavy to sit on a leach field.

How your board of health (or HOA) feels about all this, might be a whole 'nother story.

[Xandrew245x]

I work in the septic business, and what has been previously stated is true. If you were to build raised beds on top of the absorption area, the weight overtime can cause soil compaction, ruining your drain field. Also roots will find water in miraculous ways, any kind of roots getting into your septic system can cause major problems.

Here in pa water supplies have to be 50' from tanks and 100' from absorption areas, you wouldn't have to go to that extreme for a garden, but I would keep them a good 15-20' off the absorption area.