On 7 Jan, 23:24, Matty F wrote:
On Jan 8, 10:34 am, wrote:
On 7 Jan, 15:19, "Janice" wrote:
I am going to make some raised beds in my garden to grow vegetables as the
present soil is heavy clay. I already had a small raised bed made from 2ft
by 6in edging slabs and the difference in yeild was startling. I imagine
lengths 8in by 2in timber would be ok so what would be the best and
prefeably cheap timber to use? And what should it be treated with?
Jan
Use CCA [Copper Chrome Arsenic] (sorry its not called that any more)
Tanalth but make sure you get the timbers the size you want either by
special request or using standard sizes for your bed
Don not cut it! do not nail it but bind it in other ways or use copper
nails on stainless strapping
Matty is not correct in that the 'A' is no longer allowed and the
heavy metal ions are chemically fixed to the hydroxyl groups and
cannot leach out - that is the idea!
That is why it is OK for kiddies playgrounds
The only removal is by fungi translocating and you are not likel to
get that in you carrots!
Some people disagree that CCA is OK for gardens and playgrounds. In
fact many countries ban CCA timber in playgrounds. If there is a non-
CCA alternative I'd use that instead.
http://www.garden-nz.co.nz/forum/30153.html
"Tanalised, pressure treated or CCA timber are all terms for a wood
preservative system based on copper, chrome and arsenic. For years we
at HDRA have advised our members not to use tanalised timber to edge
vegetable beds and make compost boxes, simply because we felt that the
chrome, a toxic heavy metal, and arsenic, a poison used in the
preservative had no place in an organic garden
These worries were confirmed in spring 1997 by alarming reports from
the USA. Researchers found that decks made from tanalised timber can
leach high amounts of arsenic into nearby soil. Samples taken from
beneath treated decking contained up to 80 times more arsenic than
surrounding soil and as much as 35 times the legal limit for arsenic
in the soil. The study found that arsenic leaches quickly from treated
wood..."
Dear Matty
Since 2004 in the EU 'CCA' is not based on that as you suggest as the
A has been removed!
Of what possible relevance is this to my recommendation? I stated that
the A (arsenic of cca) was no longer used.
see
http://www.uow.edu.au/arts/sts/sbede...ns/Europe.html
"Since June 2004, the use of CCA-treated timber has been severely
curtailed with an amendment of the European Union Commission Directive
76/769/EEC. This amendment now states that arsenic compounds may not
be used ‘in the preservation of wood. Furthermore, wood so treated may
not be placed on the market’. The only exceptions are wood to be used
in industrial installation that ‘the structural integrity of the wood
is required for human or livestock safety and skin contact by the
general public during is service life is unlikely’. The following uses
are specifically not allowed (Commission Directive 2003/2/EC, 6
January 2003):
* in residential or domestic constructions, whatever the purpose,
* in any application where there is a risk of repeated skin
contact
* in marine waters,
* for agricultural purposes other than for livestock fence posts
and structural uses…
* in any application where treated wood may come into contact with
intermediate or finished products intended for human and/or animal
consumption.
The EU amendment therefore restricts the marketing and use of both the
CCA chemical as well as timber treated with CCA, and will also apply
to imported treated wood and waste wood in re-use. In addition, it is
anticipated that from 2007, CCA preservatives will require
authorisation according to The Biocidal Products Directive (BPD)19
(Enviros Consulting et al, 2004). The EU regulations, however, do not
apply to CCA-treated wood already in service. CCA-treated timber has
not been as extensively used in Europe as it has in Australia
however."
The evidence from Au and NZ does not take into account the differences
in their treatment specifications compared with the UK (8 kgs p m3
versus 4 for a kick off) and I could not agree more with the
delightlfully apposite comment of Huge!
CCA has stopped being used not because of its record but because "The
CSTEE could not establish the arsenic-related risks of landfill
disposal of CCA-treated timber, which is classified as a hazardous
waste by the Commission in 2000, and thus concluded that it was
appropriate to apply the precautionary principle and, in the absence
of proof of harm, reduce the production of CCA-treated timber as much
as possible because it is likely to cause serious harm (CSTEE, 2003)."
See
http://www.hse.gov.uk/foi/internalop...us/5_04_08.pdf
Sections 1,3,4 and 6 to see why in Children's play grounds CCA (with
the Arsenic) has not all been taken down
I woould be delighted to see references to any journal that has
produced evidence the PROPERLY FIXED CCA IN SOFTWOOD SAWN (NOT POLES)
treated to EU or UK standards leeches as it was my understanding that
if it was properly allowed to fix in the plant that the metals ions
were chemically fixed to the hydroxyl groups of the cellulose. Please
will some of you budding ecolocial chemists show me that I am wrong in
my understanding? Please, however, no anecdotal blogs,
Chris