Dear Denise,
Unless you have a way to detect off-gassing on this property and confirm
that there is no atmospheric contamination, or have a way to test ground
level (just above the asphault) out gassing or leakage, I would go with
'earthbox' or 'earthtainer' types of growing conditions which completely
separates the growing medium from the contaminated dirt. The information on
how to make these or contact the people who are knowledgeable about this
kind of planter are available by doing a search on-line by keyword Earthbox
or Earthtainer.
These have been used successfully in locations in as far away as Africa and
in this country for mass plantings. Earthbox has a whole farm in Florida
using this type of growing container. To make the Earthtainer type (which
works on the same principles as Earthbox) requires the use of large plastic
storage containers (the best ones are rubbermaid from my recall) which can
be purchased almost anywhere such as Target, Walmart, etc. in the big box
stores. One 32 gal. container can grow 2 tomato plants and grow 50 lbs. of
tomatoes in a season. Anything can be grown in this type of container, very
versitile.
They need to be filled with good growing soil which can be purchased by the
bag (pricey), or through a landscaping supply company in bulk (cheaper) and
delivered to the garden area. I recommend this approach as they are easy to
line up in rows, are tall enough to make approach by people in wheelchairs,
people with bad backs, the elderly easier, and anyone really. If good
composting techniques are applied (over heavy plastic, or in bins),
fertility can be achieved long term.
In container gardening, one needs to restore the fertility of the soil every
season by mixing in more organics, manure, etc. because the plants
themselves eat up the nutrients, and even the soil level will drop from
using the soil as building material. And as the growing season progresses,
it's a good idea to fertilize the plants regularly (I prefer organic liquid
material such as compost, worm compost, or manure teas, or fish emulsion or
kelp type liquid concentrates and add them to the watering about every 2 or
3 weeks in weak solution).
If this is too pricey a solution for the neighborhood you are working in,
Perhaps heavy duty plastic sheeting (at least 4 mil) over a wood frame in a
raised bed would suffice. These would be cheaper to produce but one must be
careful not to tear the plastic while planting, mixing soil, harvesting etc.
Drape the plastic from the rims of the wooden frames (at least 6" high) and
staple around the rim, with the plastic held close to the wood down into the
well created by the box. Then fill with soil and plant. One must only be
careful not to overwater as this creates a 'wet feet' type of situation
since there is no drainage. Or one could put a few drainage holes in the
base of the box through the plastic so the water doesn't rot the roots.
Good luck and let me know how it goes.
Best, Diann Dirks
"The Garden Lady" of Georgia
Certified Permaculture Designer
Director, Auburn Community Garden Project
----- Original Message -----
From: "Denise Rowcroft" <[email protected]>
To: <[email protected]>
Sent: Thursday, July 16, 2009 7:00 PM
Subject: [Community_garden] Techniques to prevent leachiing fromcontaminated
soil.
I am helping to start a learning garden on a vacant city owned lot that is
adjacent to a site that was once contaminated from an old dry cleaners.
That site went through DEQ testing and monitoring and has now been capped
by
asphalt and serves as a parking lot. A soil test for 30 VOCs on our lot
came up "non detect" but we want to go above and beyond to make sure that
there is no way that any food we grow from our raised beds can be
contaminated by possible old soil underneath. I have seen a lot of info
on
the list serve regarding lead, but I am looking for some sure ways to just
prevent any possible toxic contamination as we will be working with
children from local schools. What are some techniques that others have
used
in this situation? Thanks.
denise rowcroft | sustainability educator
the environmental center
16 nw kansas ave. | bend, or 97701 | tel 541.385.6908x14 |
www.envirocenter.org <http://www.envirocenter.org/>
Embedding sustainability into daily life in central Oregon.
SAVE THE DATE: Join us for Evening for the Environment on Saturday,
September 26th.
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