growing over low-pressure-dose septic system

Hello! Long time listener, first time caller.

We're getting a new septic system, as the house we bought in July has a failing one. Forgive my ignorance on aerobic septic systems...the system described to me by the engineer is called low-pressure-dose, and it evidently uses irrigation line 6" deep to transport "waste" water through the soil. The engineer is curt and rather unpleasant, and says that i can "only grow sod" over the irrigation lines. I think this is probably just habit or lack of vision on his part, but I'm wondering if you wise people can tell me if there is some hidden downfall to growing a variety of ornamental and edible plants there? He said "roots will clog the system." Roots don't clog irrigation lines in a freshwater irrigation system, so why would they do it with the lines from a septic system? The system is sized for 475 gallons (house, guest house, and RV pad)--WHY would I waste 475 gallons of water a day? That seems ludicrous. I live in central Texas, where summertime water is incredibly scarce, and I am envisioning a lovely garden over the drain field. Am I naive or otherwise misguided?

Thanks.
AC

Personally I would grow compost crops over the septic field and grow my vegetables elsewhere, if possible. But this would mostly be to avoid disturbing the lines, which are shallow.  I think the only likely source of contamination would be root crops if you choose to grow vegetables over the lines.  

Your engineer, while he may have poor residential manners, is giving you very accurate and sound information. It is best to heed it.

If you have ever watched Gabe Brown talk about bacteria and how it causes amazing root balls to thrive within the soil, that is exactly what your engineer is talking about too. Unlike just plain irrigation water, septic systems, humanure, is laden with bacteria that will cause massive root balls to grow. Yes this will cause the plants to flourish, but also cause those tiny holes in your septic leach field pipes to clog with tiny roots. Sod has shallow roots that prevent that from happening. Around here a new leach field is around $7000 which is one really expensive garden! Best to relocate it.

If you are adamant about using humanure, and people on here are better qualified than me on describing the right way on doing this, might be to pump it out of your septic tank and compost that. Even then you would have to be careful on what you use for cleaners, toilet paper, and even antibacteria hand soap.

But if it seems like I play exactly by the rules, I assure you I do not.

Myself I use humanure, I just pump it out of my septic tank and spread it on some distant fields of mine (so as to keep smell away from peoples homes). Also, against all code enforcement rules where it says never build over a septic leach field...well I did, and its been covered over for 8 years now with no ill effects. I was told the leach field needed water going down through it to get the sewage to drain, but that is not the case at all. Being built on crushed rock, it leaches out just fine. If something ever does go wrong with the leach field however, I got plenty of acres here where I can move it. That is a very important fact and why I am okay with building on top of it. For others in a confined lot, that might not be the case.

Travis Johnson wrote:Sod has shallow roots that prevent that from happening.

Many of our native Texas grasses have very deep roots.  Did the engineer specify what species of grass must be grown over Alexa's lines?  I don't know what species of grass is "sod."

Just did a search on "garden on leach field" and found this thread. Wondering what OP decided and how it's going? My leach field is part of our chicken forage rotational grazing system but is one of the sunniest flat locations on our property so I often think of sneaking some tomato plants in there. Shallow rooted so I'm not worried about the roots and our septic guy said the water coming out of our highly sophisticated septic system is pretty clean so I'm not overly worried about bacteria either (though I'd avoid potatoes). No till so no hitting pipes.
Just curious what others are doing with their leach fields?

To safely grow over a leach field you should have a large quantity of active bacteria in the septic tank and field lines and then lots of fungi hyphae in the soil above and around the field lines to take care of any stray pathogenic bacteria that could make it out into the soil.

Listeria is one of the worst things that will happen to any vegetable crop grown over leach lines that are not well insulated by both bacteria and fungi.
All grass species will grow very deep roots over a leach field, it is normal. (sod is a generic term for soil that has been cut to be used as an instant lawn, the sod will regrow deep roots once it is established).

Redhawk

Bryant RedHawk wrote:To safely grow over a leach field you should have a large quantity of active bacteria in the septic tank and field lines and then lots of fungi hyphae in the soil above and around the field lines to take care of any stray pathogenic bacteria that could make it out into the soil.

Listeria is one of the worst things that will happen to any vegetable crop grown over leach lines that are not well insulated by both bacteria and fungi.

Redhawk

Sounds totally reasonable to me.  What's the best way to make sure that's happening? We add a beneficial bacteria product (all natural, non toxic) to the septic but not sure about fungi hyphae in the soil. Spread woodchips? Add mushroom slurry?

I used several mushroom slurries over our leach lines, so far (4 years later) it is still working very well for us.
Wood chips would be a fair addition but you are looking more for the soil mushrooms first then oysters in a topping of woodchips would be appropriate.

Redhawk

I have a similar issue, my best sun is located directly over my leech lines. My plan was to build 8 to 12 inch raised beds over top to grow my annual vegetables, and start trees and shrubs from seed. I was thinking the raised bed would keep the roots out of the lines and out of the water table (soil surface for about 6 months of the year).  

Should this also keep the interactions of the system and plants to a safe level?  Or is it destined to be a mini obstacle course for the boys?

We use straw bales over some of our leach lines, two lines happen to travel through some of our  orchard trees (pears and figs).
I used a double dose of bacteria for the septic tank and make an addition monthly to keep those numbers up, I used approximately 50 gallons of mushroom slurries over the leach lines once I located them, this saturated the soil and soaked down into the gravel beds over time.
I waited a year and did culture testing of the soil all the way down to the gravel beds and the cultures came out clear. I tested them yearly for the last 4 years with the same results.
I am confident in my system to not contaminate but still check through culturing yearly since I feel that is prudent and it provides me more data to show the effectiveness of my method being tested.

Raised beds would be good but you would need to be sure there was available food for the fungi, which are the cleaning part of this method, the bacteria do the initial work of cleanup then as the leach lines do their job, the fungi take over to finish up.
In the last four years nothing has cropped up to indicate this method leaves openings for contaminates to cause problems.

This year will be when I add a new dosing of fungi because it is a bale replacement year (we get three years out of a set of bales (third year they are almost gone into the soil which means we lay on a new set of bales)).

History of this method: I got the idea when I lived in Newburgh N.Y. and we had a brand new septic system in a brand new house, I wanted to have a vegetable garden and the only area suitable was the leach line field.
I tested the soil after spring came in 1967 and found the soil unsuitable from contaminates.
I discussed the problem with my Biology teacher and did double doses of bacteria to the septic tank for 3 months straight, at the same time I started gathering mushrooms and mashing them in water which was poured directly over the leach lines.
In the fall of 1967 the field line area tested clear of contaminating bacteria and I started the garden with winter crops which did extremely well.
The next spring I planted a full garden including corn, potatoes and carrots, crops I considered easy contamination prospects because of their root systems.
Testing all through the growing season showed no contamination in the crops and I used the research for my term paper and did very nicely with it.

I have continued to work on this method for growing food over leach lines when I have lived in the right conditions ever since.
I used this research as part of my masters thesis, which focused on remediating lands considered unsuitable or even dangerous for crop production.

Redhawk

So, add cultures to the septic, use a mushroom slurry over the lines.

What about doubling the depth of my bed with a 12 inch base layer of wood and maybe a mushroom slurry directly on wood before I finish adding soil. Would this give ample food for the fungi for the life of the bed (I don't expect more than 5 years in my climate since I don't want to use anything treated to build it with). And would it be nessacery to inoculate the lines if I am doing the beds individually.

Also does it matter the type of mushroom or can I just go collecting random stuff from the woods?   If so would that be more beneficial than just a couple varieties of edible mushrooms.

BTW Redhawk, I'm very impressed with your knowledge I see you all over these forums. As we say in my family you know alot of shit about crap(pun intended on this topic). Keep spreading all that knowledge.

Your proposal will work very well. I try to add as much diversity as possible with the slurries, in my original trials I used 20 different species of mushrooms to make the slurries.
On Buzzard's Roost we have 15 different species of mushrooms growing insitu and I use all of them for slurries.

I recommend using slurries over the entire distance of the field lines since localized application, while good, will not prevent any contaminating bacteria from migrating back into those treated spaces.
It's a "better safe than sorry" situation really, but why take a chance you don't have to take?
It would not hurt to lay slurry over the whole of the lines then come back with an additional application over the raised bed sites.

I keep my edibles separated from my "working mycelium", I feel better about eating mushrooms grown specifically for eating that way (had a friend that was not so careful and I am not going to end up like them).

Redhawk

Thank you Bryant, your experiences are so very interesting and helpful! I'm really glad you chimed in!

Bryant RedHawk wrote:I used several mushroom slurries over our leach lines, so far (4 years later) it is still working very well for us.
Wood chips would be a fair addition but you are looking more for the soil mushrooms first then oysters in a topping of woodchips would be appropriate.

Redhawk

Thank you for the information about the mushrooms.

Your welcome, I have a.second septic test site now. This one is deemed a dry system even though the interior is pretty damp most of the time. The bacteria are supplemented. With fungi since there is soil in this system, the hard part with this system is keeping the soil dry enough that it can't turn anaerobic.  

Redhawk