Tainted Soil

[Christopher Hamel]

I initially built my raised vegetable garden with treated lumber. I know, I know... please save your darts; I am already wounded and require no additional flogging. I read multiple sources that said it was okay, but in retrospect the only ones I recall that okayed it were the government and the companies that produce treated lumber. Everyone else says it's not worth the risk (or much harsher things).

So, that said, my garden has been around about two years. I'm going to replace the wood borders this weekend (if anyone has a cost-effective alternative, I'm all ears -- I like the pastic lumber but can't find anyone that sells it in the Dallas-Fort Worth area), but my next question is regarding the soil. Is it tainted, or can it be salvaged? It's good stuff, too.

A local expert here says its possible to 'detox' the soil with something called NORIT (also mentions something called zeolite), but I don't know:

1. What that is
2. Where to get it
3. Will that really work, or should I toss the soil along the border and start anew?

Also, depending on the cost, it may actually be more cost effective to remove the [potentially] tainted soil and start anew.

I'm really bummed. I've been eating these vegetables for two years...

Thanks, Chris

[Henriette Kress]

Tar is nontoxic; paint untreated, preferably unplaned wood with that.

Or use stone borders.

Brick won't work if you have frost; it'll crumble after the third or so winter.

If you're in more southern climates you could always get a nice low box (Buxus) border; they're pretty and they keep things in. Up here they're impossible; up here, even Taxus plants are difficult to keep alive, let alone have them look good as a cut-to-size low border.

Another thing to contemplate would be willow; but willow, if planted, _will_ take over, and if woven into barriers is a lot of work (and an unbelievable amount of basket willow branches) that needs redoing every three years, as the old ones crumble.

Henriette

[Katra]

I used Cinderblock. Cheap, and permanent. ;-)

K.

[harold steig]

[tmtresh]

A quick search on google yeilded these results:

Norit is activated carbon. I have no idea if you can use it to detoxify soil.

is an odor eliminator? I understand it, treated wood toxins leach into the soil with rain and watering. When I was reading about treated lumber some time back, I was amazed to learn that there are certain kinds of plants you can get that will detox the soil. When the plants are grown, you pull them up and send them back to the company that dispenses them so they can dispose of them properly because the plants then have the bad chemicals in them. (Unfortunately I can't remember what the company's name is or the name of the plant.) If you can't detox the soil, I would suggest replacing it, or only growing ornamentals in that spot. You wouldn't want to continue eating the poisons.

[Pat Kiewicz]

IMO, two years, no harm done. (You rinse any dirt off your veggies -- especially the root veggies or low-slung green, right?)

Your risk has more been from handling/kneeling on the wood -- but I doubt you are in the habit of licking your knees or sticking your hands in your mouth. The same can't be said of small children, whose risk from being around pressure-treated lumber is still very small, but large enough to trigger EPA concern. (Decking and play structures were major consumers of PT lumber, and kids crawl all over them.)

Certainly the exposure you had handling and cutting the PT lumber when installing it dwarfs anything that two years of sitting on the ground will have done.

I don't use anything to hold up my (slightly) raised beds. You probably would be safe replacing your borders over the next year or so with concrete blocks.

Your soil is fine. Keep adding compost, and wash your veggies before eating. You are in far greater danger of cancer from working out in the sun in your garden than from that treated lumber. Low levels of arsenic are present in the soil just about everywhere. (I remember reading somewhere -- possibly in Science News -- that in areas where soil levels or arsenic are *extremely* low, people are more prone to heart disease. Some animal studies have been done which seem to support the theory that arsenic in tiny amounts might be essential. Remember, selenium is a toxic metal and a pollutant in some areas but also an essential nutrient, in very small amounts.)

you do, do not cut or burn the PT lumber you remove.

[Christopher Hamel]

Thanks to all for the great feedback. It sounds like cinder blocks may be the way to go... cheap and permanent. I imagine if it's done right, it can also retain some of the asthetic appeal I am hoping for, but I'm more interested in the cheap and permanent aspects.

We have clay soil (Fort Worth, TX) that's about as hard as cinder blocks, so my garden soil is raised a good 8 inches off the ground... doesn't really lend itself to a borderless bed. Not only that, but the lawn is Bermudagrass, and without a barrier it will consume the entire garden in a month's time.

I do have four little ones (my oldest is six; yes, my wife is a saint), and they are becoming increasingly interested in the garden so this may be a good time to make the switch from the treated lumber to something else.

Thanks again for the advice. Chris

[simy1]

A little advice. Your plan is very good, but if you put down cinder blocks directly on top of the hardpan you seem to have, you will lose a lot of water trickling under the blocks, specially when you are watering heavily (trust me, because I have the same setup on sandy soil). My advice is to bury the first two inches of the blocks, rototill and mix in the middle. That way you preserve water in the summer, but the roots have still six inches of breathing room during heavy rains. It does not apply if you plan to have drip irrigation, which has time to be soaked in the bed.

To train a kid to eat carrots or tomatoes out of the garden, is the easiest thing in the world. My one even prefers our own greens to unfamiliar but not green veggies. She and her friends once stripped a carrot patch clean while I was not looking (the carrots were still small, so they had to load up).

[Ray Drouillard]

Did you have the soil tested? Before worrying about detoxifying it, test it -- not just for the presence of heavy metals (which may have already been there, anyhow), but for the concentration of heavy metals.

Pressure-treated lumber is designed to stand up to being buried for twenty years or more. It isn't going to work in the long term if the stuff leaches out of it.

The biggest issue I have with the stuff is sawdust. Burning it might make the heavy metal bioavailable -- not good. Based on this, when I use the stuff, I cut it as little as possible, and send the sawdust to a dump (where it can linger for years with old appliances that contain gallium, arsenic, lead [in solder], and all kinds of other nasties).

Ray

[Bpyboy]

hey chris, don't be bummed about eating veggies from the treated lumber beds. Think of the crap you DIDN'T eat, by not buying 6 month old produce from the store!

[tmtresh]

I just found the site I was looking for:

which sells plants that take arsenic from the soil. They are also experimenting with plants to remove such contaminants as lead and uranium. I think it's pretty cool what they are doing.

Initially I found reference to it at

downside to this is the minimum order is 30 plants at $4.95 each bringing the minimum order price to a whopping $148.50 plus shipping/handling!

(Sorry about cross posting this to rec.gardens, because this is where it really belongs.)

[Christopher Hamel]

The downside to this is the minimum order is 30 plants at $4.95 each

Incidentally, the gent who recommended Zeolite is Howard Garrett, aka "The Dirt Doctor," who hosts a radio show here and is a big advocate of organic gardening. I saw the recommendation on his web site and did the same google you did, revealing Zeolite as an odor control mechanism. This sparked my initial confusion, prompting me to post the message.

I was reading a book he wrote this weekend, and he actually talked about Zeolite and cleared up some of the confusion. In a nutshell, he said that it will absorb the harmful stuff and then slowly re-release it. Along the lines of what Pat was saying (in this tread), there are toxic chemicals everywhere, only in trace amounts. If you can keep them in trace amounts and in balance with nature, then they don't really pose a risk.

Something like that, anyway.

I already had a bunch of fresh compost, so I took out the wood this weekend, replaced it with cinder blocks ($0.95 each at Home Depot for

4 x 8 x 16" - fixed the problem for under $50, but my Kia barely made it up the hill with that load) and mixed the soil and compost around really good. Hopefully nature will do the rest.

Lots of fireants in my garden... Man, I hate those things.

Thanks for the advice on the plants. That is a bit expensive, but it's something to keep in mind.

Chris

[The Watcher]

On Wed, 18 Feb 2004 11:46:05 -0600, Katra wrote: (snip)

I tried cinderblocks, but didn't like a few things about them. They tend to wick water from the beds and they are very uncomfortable to work around. I don't have any "border" around my beds right now, but they're not really raised either. I planned on raised beds, but once I got most of these Ozark rocks out of the beds I had sunken beds. Adding organic matter and not compacting the soil has left me with beds that are pretty much level with the surrounding soil.

[The Watcher]

Before you get too set on cinderblocks you might want to put a few around your beds and try working around them. I set up some around my beds, but took them out pretty quickly. I hated the hard rough blocks. They take off skin too easy and make working near the edges of the bed a hassle. Some people do like them, but I didn't.