I assume you are worried about bacteria. Assuming the septic tank is functoning properly there should be no bacteria. My opinion is that bacteria is not a problem. I have gown potatoes on a tile bed and they were few in number, but of superb quality. I suggest growing above ground crops, lettuce, swiss chard, Brussel sprouts, cabbage, caulflower, broccoli, beans, and peas. In China human feces is used as the normal fertilizer. There are few large domestic animals so animal waste is not an option. And I presume the waste used is not as treated as that which goes through a septic tank. My unscientific opinion only. Durgan.
Hi Tita, From this extension service site: http://www.ext.vt.edu/pubs/envirohort/426-617/426-617.html#L7 Newt
Interesting quote, Newt; when I took a Watersheds Master course through our local extension office, we spent quite a lot of our time discussing septic systems and leach fields. We were told that you could grow veggies on the leach field, perhaps avoiding root crops, and that up to 18" of soil could be put on top of the leach field without effecting its operation- raised bed gardens were fine as long as they were not deeper than 18". Paving was to be avoided. One of my own veggie gardens is on my leach field, in 12" raised beds, does very well and is very productive- no root crops in the leach field itself. We also have extensive rock/alpine gardens on other parts of the field and they are quite successful. The leach field itself is 25 years old and working well. (Pump your tank regularly!). With the advent of pressurised fields, rather than gravity fed, the recommendation may have radically changed.
Terry, your garden is gorgeous!! What would you do if you had to dig up your septic tank? It would break my heart to dig all that out. I looked more closely at the article and it is from a publication dated December 2000. Since the course you took was through a local extension service, maybe they were referring to local soils that aren't sandy? When did you take your course and do you know the date of the sources they quoted? That would be helpful. I wouldn't want to give people outdated info! I do notice that your land is sloped and the raised beds for the veggies are at the higher end. Have you ever had the soil tested? Newt
The garden part is only over the raised leach field. The tank itself is under a gravelled area for access. For most our area, when a leach field fails, a new field is constructed elsewhere on the property; that would be a problem as the other suitalble areas are all either in landscaping or orchard! The course I took was about 10 years ago; referred to constructed, gravity fed raised leach fields. At the time, pumped or pressurised fields were not common, tho I understand that now they are more the norm in our area than gravity fields.
Terry, I did note the gravel area and figured that was the tank site. I did wonder what you might do if you needed to replace it. Newt
Actually, Newt, the tank is not in the picture. It sits almost adjacent to the house off the deck, and we can access by pushing the gravel over it to one side. The raised boxes are at the north end of the leach field, and the rock garden at the south end, with the pine hedge off the south edge. Because the drainfield is raised, we terraced the edges and planted them; yes if we ever had to dig up the leach field, plants would be sacrificed.
