Is it safe to grow edibles over a septic drain field?

The safety issues I am wondering about have to do with the health of anyone eating foods grown over the leach field and should I avoid trees in that area (like a fruit tree food forest)?  What I read from the governmental sources said that nothing edible should ever be grown over the leach field and that tree roots will most probably damage the field. 

Living in a high desert area, I hate to waste all that moisture already in the ground.  I know there is a plentiful amount of moisture there because the weeds (kotia, especially) is growing 5+ feet high there. My land also gently slopes that way so the run off is also easy to harvest there.  What do some of you permies have to say about the health issues? 

I have a 4' high banked drainfield, the banks aren't really part of the drainfield but banked to make it easier to access the 4' high raised drainfield..most of the actual drainfield is covered with lawn, in a circle, but around the circle on the banks, I have dwarf fruit trees as the understory layer (under some large maples and ash and apple and catalpa off the field)..of a forest garden..there are herbs and perennial flowers and shrubs and vines growing on the rest of the field and grapes growing on the far end of the drainfield over an arbor..I have no problem with any of it..but I do try to keep the center of the drainfield to the lawn, as it is almost too dry for the lawn to live there..water tends to flow away from the draifield and mine is very dry on top

IF your septic system is functioning approrpriately[i][/i] emphasis on if, the leachage should be clean enough to drink.  but would you?  same for the plants that would grow from it. the folks at the health dept say that it shouldn't be done because of the chance of contamination.  and that ol' e coli and other bacteria perking in there could kill you. So, while it's understandable that you hate to wast the moisture, the risk probably isn't worth it, simply because you may not know you're system's not working right till it's too late.  tree roots will definitely damage your field as will animals grazing on it.  do you have a curtain drain around it?  try trees on the other side of that.

It would be safe to grow and eat fruiting plants, but not leaf or root crops, because of the possibility of leachate getting on them.  As mentioned, of course a properly functioning drainfield will never have exposed leachate, but I have rarely seen a functioning drainfield - our present one seems to be  the rare exception in my experience, all the rest at various homes have been utter failures, often with stinky water sitting on the surface. 

Recently I swaled around our leach field, and now I'm wondering what is safe to eat for humans, chickens & for no one. I'm not growing on top, but 10 feet away, somewhat downhill.

Can I easily DIY test for e.coli & other gick?

Can I be assured that it is safe at a certain distance?

Can I feed the closer swale fare to the chickens?

My swales:

I have the same dilemma, what to do with all that space out the back. I was thinking raised garden beds with a plastic barrier underneath so no roots will penetrate the possibly contaminated soil. has anyone done this?

I put in a septic tank and drainfield, had it inspected, then promptly disconnected the drainfield, sealed that end of the tank and started a cistern -- imho septic systems are accidents waiting to happen -- composting or feeding our waste to poop beast trees or what have you is far superior. I personally believe and follow the humanure handbook, in which he goes through all the pathogens of human manure and what temps are necessary to eliminate them
that being said

since you have a system in use,


the issue is not one of plant roots ingesting whole organisms and transporting e coli ,say, from roots to fruit--the issue is one of the "contaminated" ground touching the surface of the fruit or vegetable, so tomatoes would be pretty safe, while carrots might be questionable

realistically, the surface of your soil should be clean of pathogens unless you have some sort of serious malfunction, soil tests would tell you for sure

I personally would be more concerned with the chemicals many people flush into their systems along with heavy metal accumulations than with pathogens--depending on the age of the system and the habits of the occupants.

the answer to biologically decontaminating that soil would be to make a good aerobic compost tea and spray it around,, or just make lots of good aerobic compost and scatter it around--or top dress any plants you put in--the good aerobic bacteria are the best weapon for decontaminating the anaerobic bad guys-

I could suggest two rules of thumb, that other writers already are mentioning. First, only plant crops in which the harvested portion is not at ground level or touching the ground. That means no lettuce or carrots. The second rule of thumb is don't plant anything that's eaten raw; only what typically gets cooked. Eggplant, or tomatoes for sauce would be fine in this aspect. Most of the human pathogens found in solid waste, like E. coli, Salmonella, and viruses, are relatively heat sensitive, and get killed at temperatures above 70C.

And the problem with trees and shrubs on the drain field is that their roots will destroy it in few to several years ... I spent some time researching it but couldn't come up with anything really except for pasture/chickens or bamboo.

i would like to suggest a couple less than super cautious possibilities

my father grew his garden on top of our septic field most of my young life

septic fields are constructed so there is no or little contamination of the surface soil, and in a properly functioning system the leachate should be heading downward until it hits a hard strata when it goes sideways

even in the unlikely event of severe backup or surfacing of sewage--which would be noticeable, the normal aerobic soil organisms would neutralize any pathogens within a year or two depending on conditions


http://agroinnovations.com/podcast/2014/01/13/episode-132-the-soil-food-web/

Elaine Ingham is on the cutting edge of what's going on with pathogens and soil microbiology, this is the first of two podcasts

This idea that every piece of food taken off a septic field has to be boiled--even fruits that never touch the soil is a bit extreme to my way of thinking

Unless the people using this system had some rare extremely serious disease i've never heard of, i wouldn't be afraid to eat lettuce right out of the garden, no washing or anything

but that's just me i guess, everybody else on this thread seems to think septic fields are toxic waste zones

Finally got around today to that phone call to the septic company and yeah...had to look up this thread. He's sending the map of the drainage pipes.

He said the older ones are 2-3 ft deep and the newer pipes are 1 foot deep.

The idea, especially in our clay soil, is that the moisture will evaporate upward. Take that for what it's worth.

Also, he said, pipes can't be installed any less than 4 feet apart. We inferred that might be the distance from which you might want to be away from any pipe if you're growing edibles. But that was an educated guess.

If you're wondering about your septic system, call the guy who cleans it, they keep maps.

http://homeguides.sfgate.com/plant-garden-relation-septic-system-drain-field-48282.html

Measure 10 feet from the outer perimeter of the leach field. Mark the garden's borders with stakes. According to the University of California Small Farm Program, fruits and vegetables should be planted at least 10 feet from a septic system or leach field to avoid bacterial contamination.

That should help clear things up for myself and others.