What's the bottom line? That the choice is yours. While it certainly isn't recommended, if you are comfortable with it go for it. It is your leach field and your garden.

Just keep in mind

(1) that water doesn't go straight down, it diffuses out first and

(2) during periods of heavy rain, run-off, or snow melt water can actually go up, rise in the soil

(3) while N found in the effluent may be beneficial for the plants to a degree, excess N also poses problems for plants and all the bacteria in it may not be quite so "beneficial" :)

(4) and soil over leach fields tends to settle over time and that allows roots access to it causing possible plugging of the field as well as contamination of any foods grown there.

As one of the articles linked below points out, the leach field is the most expensive and the most potentially problematic parts of your entire septic system. So it can be money out of your pocket to mess with a good working one.

We live on one of the largest man-made lakes in the country with miles and miles of uninhabited shoreline yet the lake is still having some problems with septic contamination. I say this only to point out that even with thousands of acres of land involved and massive water dilution, bacterial contamination is still possible so it can't be treated lightly by the average home gardener. I have 8" raised flower beds planted over my leach field and because of the slope I wouldn't consider growing edibles there. If it were level I'd want at least 18" deep raised beds. JMO

Dave

University of Nevada AG Extension - Planting on Septic Leach Fields

Virginia Tech Extension - Planting on Your Septic Drain Field

I manage that area of my landscape for mulch production -- grasses and clovers I can mow as needed for vegetable garden mulch. Best use I've found for that space, and grass seed is kind of fun to play with.

On the other hand,I don't think veggies with shallow roots would tap the septic field because of the depth of the lines. However, disturbing the soil at the surface repeatedly could have some repercussions down below in sandy soil.

septic fields are so expensive why risk it? And if/when you have to have it all dug up...there goes your garden

g'dat tom,

this question pops up from time to time and it has those who oppose it and those that support it, for me as we now have a septic system i would have no issue spreading some mushroom compost or the like over the top of the leach pipes, this so i don't dig at all, and plant annual seasonal above ground vege' type plants ie.,. tomatoes, bock-choi/cabbages etc.,. that sort of thing, no root type crops(that involves digging though our way with our instant potato growing might be ok dunno? no digging involved).

laying something like mushy compost will stop any splash occurring though again your field would already need to be over saturated for that to occur, and would use mulch hay as well.

don't see that annual seasonal crop roots can cause any long term issues as they are seasonal plants and once expended their roots will rot away.

also plan on having our citrus and other fruit trees about 5 meters below the leach field, so any over flow goes to good use, below that we will have a habitat garden of native trees and shrubs. why let the grass enjoy all that nutrient?

so long as common sense prevails, science will only ever support those in control, so no good relying on scientific theory. again good old common sense.

gotta get real in times of drought there is all that water just down there.

so what is grown like from any garden gets washed after harvest and gets cooked. know people who pump out of their tank to gardens smell a bit but they are still very much alive and walking around.

len

Here is a link that might be useful: lens garden page

"science will only ever support those in control, so no good relying on scientific theory"

There's a few thousand years of what's now called "common sense" gleaned from this "science."

There's also plenty of dead gardens out there by people who want to conquer nature rather than letting the mistakes of the past guide them to a conclusion.

Besides, the only conspiracy scientists could cook up for this benefits those that sell/repair septic tank systems.

A lot depends on soil texture, soil moisture content, how much humidity is in the air, how much shade is on the septic lot, and how quickly it clears.

There's some areas where you can get away with planting on your septic field and many areas where you can do that and get a wonderful smell of fermenting bathroom.

The septic system in most areas are designed to take up "just enough" space in the landscape to do it's work and put up with the occasional heavy rain that doesn't dry out quickly...and little else. Some people may have a few acres with a huge septic field that gets full sun and even after the largest rain it's only "soggy" for a few hours while the sun bakes it out.

Generally you don't want a few hundred pounds of soil + constant moisture feeding plants hanging over your septic field. If you can get away without adding additional moisture you're already pushing your field if there's that enough available moisture that close to the surface of the field.

There's also the contamination thing, but that's so minor once you wash your produce. The real issue is growing a $2000 tomato because of what you've done to your septic field if it can't handle the extra weight/moisture and root displacement moving soil in the field.

I am reading this all with great interest as I just had a whole new system put in last year. I asked the man in charge about planting over it and he said I didn't have to worry about it at all.

The raised beds that I have for my veggies now, (and I am planning on adding similar ones over part of the drainage area) are about 18" high, though the soil is only about 12".

I have never seen water collect in this part of the yard, even after days of heavy rain. However I am going to re-think what I plant in those beds.

It all depends on the field.

"A lot depends on soil texture, soil moisture content, how much humidity is in the air, how much shade is on the septic lot, and how quickly it clears."

If you have 2 people using a septic field designed for a family of 5-6 then you have some leeway. If you have 5 people using that same field and it's in partial shade most of the day in an area where you get 30"+ of rain a year...you might want to think about that garden location.

The age and design of the field also plays a part...it's health compared to it's design.

There is no absolute yes/no on the issue, but for the most part it's a "no" for most people out there, a "proceed with caution" for some, and "no problem" for others.

Thank you all for the input. The leach field was installed last year. It's full sun all day. The drainage here has been historically very good. I had to move the field to this side of my house. But it's a perfect site for garden plots.

Sounds that most of you would not do it. I respect your opinions. I may research it a bit more but will likely not plant beds over the field.

I gardened for many years with the edge of my cornfield overlapping the edge of the septic field. I had the soil tested multiple times and spoke with the county health department. I even checked for heavy metals, etc. Never had an issue and the veggies grew well. About 10 years ago, we moved the septic field but continue to grow over the edge of the old field - I know where it was because if I get near it I find the old fill rocks.

I do use raised beds which are at least 18" - 2' raised above the original soil level.

In case you end up doing it, herbaceous plants (as all veggies are) are generally recommended for planting over a septic field. Woody plants are uniformly considered bad. There is virtually no bush or tree that will not try to get into the pipes.

Second, there is a product, copper sulfate I think, that you can flush down the toilet once a year during the growing season, It will kill whatever root is in the pipes on contact. It will affect your veggies nutrient balance some, since

Many veggies go down to 4 feet-6 feet, given a loose enough soil. Beets go to 6 with their tap root, tomatoes go to 4.
There is no time over a season to block a pipe, but hair roots will get in there and you should avoid perennial veggies (such as asparagus), or even perennializing something like, e.g., cardoon. True, most veggie roots will be in the first foot or so, and planting over septic fields has been done for centuries, so you will have to estimate health risks on your own.

Consider also which vegetables are eaten raw and which ones cooked. Most root crops here end up either roasted or in soup, for example. Either way, sterilization is certain. Same for winter squash, shelling peas, shelling beans. Lettuce, I would think twice, since it has hollow stems, OTOH its roots are so puny it is unlikely that it will get down to the pipes. Radicchio is eaten raw and has a tremendous tap root, so beware.

The lowest risk for the field is for plants that are planted near the end of the field, where water is scarce, the highest is for plantings near the top of the field, where water is abundant.

I am considering making enclosed beds and setting those planting containers on top of a leach field it is the sunniest place in my yard. Would that endanger my Drainage Field?

My garden is over my field. For the last 9 years. I don't use raised gardens though. Never a problem for my field.

"I am considering making enclosed beds and setting those planting containers on top of a leach field it is the sunniest place in my yard. Would that endanger my Drainage Field?"

Assuming you mean standard raised beds (sides but no bottom) then I think your question is already answered in all the responses to this question that are posted above. When it is possible to avoid the leach field then that is what is recommended. When you can't avoid the area then you work with what you have and deal with the problems if they arise.

But you said "enclosed" beds, and "containers". That usually means things with a bottom in them. That poses a whole other set of potential problems. Assuming these containers would have drainage holes in the bottom then any effect on the field would all depend on their size and how much additional water the area would be exposed to.

Dave

Yes I did mean enclosed- bottom too. I was thinking of using wire forms and concrete. Honestly I wasn't thinking of using drainage holes. I'm wanting to grow herbs and carrots, potatoes, and to place these containers in between the pipe lines.

By the way.. My soil is mostly sand I live in Florida on a lake.

Well the general rule in container gardening is that the containers must have some form of drainage. Otherwise the water collects in the bottom, you get ponding of the water, bacterial growth, and root rot.

I can't really picture containers made from "wire forms and concrete". That would be quite unusual IME but I would be worried about that weight on the field interfering with drainage in the field.

Given all the drainage problems and shallow drain fields one reads about in many parts of Florida, especially with sandy soil, I'd be very reluctant to alter my septic drain field at all. And there are literally thousands of lightweight containers with drainage holes available for gardeners to use that can be easily moved and adjusted for sun exposure without creating problems for the filed.

Unlike in-ground gardening Container Gardening has its own set of unique needs so I'd suggest some in-depth reading over on the Container Gardening forum here.

Dave

I have 24 inch tall planters with the soil at about 22 inches above ground level and laid down stabilized decomposed granite over the space between the planters, was this a mistake? Is there any way to mitigate the loss of breathable soil? PVC aeration pipes coming up out of the ground?

It is extremely unlikely you will have an issue either way (garden or septic field). I would not hesitate to do it. If the leach bed breaks I am pretty sure you cannot "fix" it - or build a new one there anyway. If you have never had "waste" show up at ground level then it is highly unlikely you will have it make it that high then through raised beds.

Also I would not put any barrier down on existing ground level - trying to "hold in" septic is impossible and roots go deep so leave it as is.

I am a civil engineer and had to design ww treatment plants in college and have lived in 2 homes with septic and sold several others (which had to get inspected etc.) . I am not an expert but I have experience.

I plant annual flowers and decrative pumpkins over a leg of the septic field.

There are peoples on Earth who use their waste to fertilize their food crops. Some of them tend to be smaller in stature and somehow seem to become immune to problems that result from their actions. People build up immunities to problems they've been dealing with all their lives. Those who don't get eliminated early

Myself, I would never grow food near a drain field. I have a maple tree near one and the year that I tapped trees and boiled off sap I skipped that tree. I gave up the syrup project after a case of bacterial pneumonia after sitting outside in February for days feeding logs into the fire. My doctors insist that wasn't the cause, but suppose I hadn't skipped that tree. How would I convince myself.