Data Package to Support the Re-Affirmation Of AWPA CCA-Type C

122 Pages·2013·3.87 MB·English

by  Mike Freeman

Data Package to Support the Re-Affirmation
Of
AWPA CCA-Type C
[Chromated Copper Arsenate]
In
AWPA Standards P-5 and P-23

Mike H. Freeman
Independent Wood Scientist/Chemist

July 01, 2013
Executive Summary

At the Spring 2013 AWPA Technical Committee meetings in Honolulu, Hawaii it was
mentioned, under Agenda Item 12(Outline work for ensuring year), that the AWPA
Standard for CCA-Type C would be up for Re-Affirmation in 2013. No Task Force was
formed at that time. The attached Data Package details the requirements for AWPA
Preservative Re-Affirmation of CCA-Type C and includes papers published on CCA
since the last Re-Affirmation in 2008 and supporting documents for it’s Re-Affirmation.
With no negative performance issues known to have been observed on this
Preservative in the last 5 years since it’s last Re-Affirmation, it is recommended that
AWPA Preservative listed in Standards P-5 and P-23 be Re-Affirmed as written.

Review Existing Standard

The Standard for CCA-C in the AWPA BoS has historically been listed as Standard P5
section 6. In 2007, Freeman and Jung re-formatted the wood preservatives into the new
Preservative Standard format and issued it for publication to Colin McCown, as AWPA
Executive Vice President, which included a DRAFT watermark until final review and re-
affirmation. This P23 Standard has been reviewed and is in need of no editorial
changes and corrections. Earlier the team of Shields and Fox submitted changes and
those corrections to Colin McCown following the AWPA Spring 2010 Annual meeting.
These corrections have now been made; including the removal of the “ Draft ”
watermark on P-23 and it is now fully listed as AWPA Standard P-23, after following the
removal of the DRAFT watermark. AWPA Standard P-5.6 is also adequate, but needs
to also incorporate changes and it reads satisfactory as well, but it is the understanding
of this author, this Standard would soon be retired and archived under the AWPA
System, much like the Use Category System replaced the Commodity Standards. The
author suggests both standards be re-affirmed until all P-5 Standardized wood
preservatives are archived.

Efficacy Data and Reports

A Complete Efficacy Review is attached to this Data Package and covers over 5
decades of efficacy and evaluation testing of CCA. Additionally, under APPENDIX 1, to
this Data Package, are the following Documents:

Freeman, et al, 2005. This study is report on the 53-year exposure of Boliden Salts
Type B treated wood pole stubs in southern Mississippi (AWPA Hazard Zone 5). This
report and study indicates that wood treated to 0.7 PCF CCA-Type B Salts (as Oxides)
has an estimated service life in AWPA Hazard Zone 5 of 73 years in 6-8 inch diameter
Southern Pine Pole Stubs. It should be noted that this retention is slightly above the
current AWPA recommendation for wood utility poles in this hazard zone, being roughly
only 16% above that of the required assay for Southern Pine in Hazard Zone 5, and
68% of the pole stubs/posts are still performing well.

Woodward, Hatfield, and Lebow, 2011. USDA-FPL-02 (Extracts). In this USDA Study,
CCA-Type C when tested in 2x4 SYP 100% sapwood stakes, in AWPA Hazard Zones 3,
4 and 5, tested an evaluated at retentions ranging from 0.14 pcf CCA to 0.79 pcf CCA,
stakes treated to 0.14 pcf performed well for 29 years (23% of AWPA Retention for CCA
utility poles) and when tested at 0.60 pcf CCA (100% of AWPA CCA Pole Retention), no
failures where observed after 40 years.

Woodward, Kirker and Lebow, 2012. In the AWPA Task Force Report on CCA posts
installed in AWPA Hazard Zone 5, no CCA posts have decayed after 35 years of
exposure, including those posts installed at 0.40 pcf CCA (as Oxides), or 67% of the
AWPA CCA pole retention.

Lebow, 2010. In this paper USDA-Forest Products Technologist Stan Lebow reviews
the efficacy trials of both CCA and ACA. This study indicates that CCA retentions,
based even on early data sets, have most likely been set at the correct long-term
performance retentions in the AWPA Standards.

Product Performance

There have been no widespread failures of CCA-Type C treated wood products in
service, over the last 30 + years, other than those minor occurrences of a few single
bad poles failing to either treater error or drying prior to treatment issues; additionally,
no performance problems have been observed since 2008, since the last CCA Re-
Affirmation.

MSDS’s and US EPA Product Labels

Currently, only three basic manufacturers are registered by the US EPA to sell and
market CCA-Type C into the USA for pressure treating. These three companies, Lonza
(formerly Arch Chemicals), Osmose, and Viance maintain US EPA Restricted Use
Pesticide labels with the US EPA. CCA has just recently undertaken and completed the
extensive seven-year Re-Registration program with the US EPA and Industry and the
RED has been issued. Example US EPA labels and Product MSDS’s are attached
under APPENDIX 2.

Extension of Exposure Conditions

CCA maintains use patterns for utility poles, piling and other specific uses as outlined by
the US EPA RED and a Settlement Agreement from the producers and the US EPA as
mandated and agreed upon in February 2002, and promulgated fully on December 31,
2003. CCA has complete data package and support for use in areas on the USA for
FST conditions, and currently maintains no use limitations, other than residential lumber
uses.

Additional New Data

Conductivity of CCA Treated Wood

There has been periodic discussion within groups of electrical engineers and utility
linemen over the conductivity of CCA treated wood poles over the last decade.
Apparently, having the name ‘copper’ in the treatment designation seems to give rise to
show concern to certain parties. In 1992, Freeman published findings on Southern Pine.

Over the last year, two additional studies have been performed on CCA treated wood,
comparing it to the conductivity of small clears (Ragon et al 2010), pole stubs, (Ragon
at al 2010. These findings were first published at the South East Wood Pole Conference
in Memphis, TN, and at the recent AWPA Annual meeting. One of these AWPA papers
is attached under APPENDIX 3. In summary, they indicate the testing of CCA treated
SYP pole stock was only slightly more conductive than untreated SYP pole stock and
only slightly more conductive than comparative oil-borne treatments. The study also
illustrates the significance of wood MC on the conductivity testing of all types of treated
wood.

Gaff Penetration

Shupe, Wu and Freeman, 2011. Over the years, there have been many rumored
complaints about the ability to climb CCA poles. In this complex, and detailed study of
three gaff types, including the one designed by former Koppers employee, Harry
Demers, especially for CCA poles, it was determined, that CCA poles were no harder to
climb or have gaff penetration than pole stock of either untreated Southern Pine or
Penta treated Southern Pine. This study is attached under APPENDIX
4.

Carey, 2009. In this 20 years update on CCA/Oil system from Koppers/Arch/Lonza, trial
results from actual climbing tests on CCA treated poles indicate the ease of climbability
can still be observed after multiple years exterior field exposure. This study is attached
under APPENDIX 5.

Summary and Closing Remarks

Currently in the USA, three chemical companies supply CCA for pressure treating wood.
Today, there are 158 domestic and 27 Canadian treaters treating with Chromated
Copper Arsenate (CCA-C). These treaters are producing mainly utility poles, piling (land
and fresh water, foundation and marine), structural timbers, fence posts, plywood and a
very small amount of crossties. In the US market, roughly 165 million poles are in
service, with roughly 35 % of them being previously pressure treated with CCA. The
CCA volume domestically in the USA, is approximately 40 million oxide pounds and
over 70 million cubic feet have been produced in N. America on an annual basis for the
last 4-5 years, with a growing percentage of both the pole and the marine piling market.
Based on these facts and the long positive efficacy history of CCA-Type C, this
preservative should be re-affirmed in the AWPA BoS.
CCA EFFICACY:
A Comprehensive and Critical Overview of Existing Data

Mike H. Freeman
INDEPENDENT WOOD SCIENTIST
Memphis, TN
e-mail: [email protected]

Factors Affecting CCA Efficacy
CCA preservatives have served well in many applications throughout the world. For
several years CCA was undisputedly among the most effective wood protecting
chemical against a wide spectrum of wood degrading organisms under challenging
terrestrial and semi-aquatic (wet) environments. However due to the potential
environmental hazards of heavy metals, several regions with long established CCA
markets (North America, Japan, Europe and Australasia, Indonesia, Japan, South
Korea) decidedly restricted the usage of CCA preservative to non-residential
environments and mandated the use of more organic alternatives (Wong and Lai 2007).
Evaluation of CCA alternatives commenced in the early 1990s for health, safety and
environmental grounds. Studies evaluating replacements of CCA always compare it as
the benchmark. In response to concerns on arsenic and chromium, a number of
copper-based inorganic and organic systems have been developed and standardized
as alternatives to CCA. Older arsenic free formulations such as CCB and AZCA co-
existed with CCA. The newer alternatives all rely heavily on copper as their primary
biocide but include inorganic or organic co-biocides. These include alkaline copper
preservatives with copper solubilized as an aqueous amine or ammoniacal complex, in
combination with cobiocides to provide protection against copper tolerant fungi and
termites. They include alkaline copper quaternary (ACQ), acid copper chromate (ACC),
copper HDO and copper azole (Lebow et al. 2004).

CCA is widely regarded as one of the most effective preservatives for ground contact
use. Main factors affecting CCA performance are formulation type, test site and test
specimen size, retention of CCA, formulation type and treatment method. This section
will elaborate on factors that affect CCA efficacy and compare CCA efficacy with that of
the newer alternatives now on the market.

Effect of treatment method and Retention level on CCA Efficacy
Although the full cell (Bethell) process is routinely used for CCA, Lowry and Rueping
(empty cell) or modifications of them are also employed. A number of studies have
considered the effects of CCA preservative application method on the efficacy (Hedley
et al. 1990; Preston and Mckaig 1983, Hedley et al. 1995b); Hedley et al. 1996; Peek
and Willeitner 1988). All these studies show a marked difference between preservative
microdistribution between the Bethell and Lowry processes.

It is assumed that similar copper retentions ought to give equal control of decay
irrespective of treatment process. However this was not the case in a study by Hedley
et al. (1990) in which they examined effects of treatment processes on Pinus radiata
sapwood (40x40x500 mm³) treated with a range of concentrations of the CCA (Tanalith
C) using Rueping, Lowry or Bethell processes. Treating pressure, treatment time and
final vacuum was the same for all treatments. Final vacuum was 15 min for Bethel and
45 mins for Lowry and vacuum. Initial vacuum was -85kPA for Bethel and initial
pressure for the Rueping process was 350 kPa for 5 minutes. Samples were then
reduced to 40x40x7 mm³ test blocks and exposed to Coniophora puteana a copper
tolerant brown rot species by agar block. Replicate blocks were analysed for
preservative components. Results showed significant differences in efficacy of CCA
when applied by the different processes (Table 2). The order of effectiveness was
Bethell > Lowry > Rueping. While weight loss caused by decay to 10% required
0.028% copper for Bethell, it required 0.072% Cu for Lowry treatment and 0.084 % Cu
for Rueping process (Hedley et al.1990). Similarly weight loss against just copper
retention (column 3) showed significant difference between the treatments. This
difference was explained by differences in distribution of preservative elements
following treatment by the three processes especially at low retentions. Preservative
solution fills cell lumen voids at completion of the Bethell process and as the solvent
dries more active ingredients are deposited on the lumen wall than would be the case
for empty cell treatments in which much less preservative is left in the cell lumen after
treatment. Even at low treating solution concentrations this deposit from the Bethell
process is richer in toxic ingredients than that which is left from the empty cell
processes with higher solution concentrations. Lumen deposits are more important
against brown rots like the pure culture fungus used in this study.

Table 2. Efficacy of CCA when applied by different treatment processes
Treatments Analyzed Retentions % weight loss in wood samples
% TAE % Cu % Cr % As
Bethell 0.036 0.013 0.024 0.020 34.82
0.072 0.018 0.037 0.027 27.60
0.109 0.027 0.062 0.042 6.16
0.222 0.062 0.128 0.085 1.81
0.441 0.115 0.232 0.161 1.05

Lowry 0.072 0.018 0.022 0.009 30.68
0.109 0.029 0.033 0.014 32.56
0.222 0.052 0.081 0.034 15.53
0.441 0.083 0.137 0.065 4.73
0.871 0.135 0.282 0.141 1.14

Rueping 0.019 0.024 0.039 0.003 29.19
0.222 0.042 0.060 0.013 30.29
0.441 0.072 0.129 0.042 9.63
0.871 0.103 0.215 0.092 4.80
1.728 0.144 0.375 0.202 0. 80

Relative proportions of preservative elements in the Bethell treated blocks were close to
those expected from relative proportions in the formulations. However in the Lowry and
Rueping treated blocks, disproportionation of elements was evident at lower retentions.

In a second study, Hedley et al. (1995a) compared the three treatment methods (same
parameters as in Hedley et al. 1990) on Pinus radiata sapwood but on fungus cellar
stakelets exposed in unsterile soil beds in the FRI Fungus Cellar. Results after 65
months exposure indicate that performance was related only to preservative retention.
Differences in treatment process had little effect on decay resistance. This is in contrast
to results from pure culture decay tests, reported by Hedley et al. (1990) who indicated
that disproportionation of preservative elements using empty cell processes had
significant effect on durability. Wood treated by full cell would have greater deposits of
CCA on cell wall lumina (2-5 times higher as shown by electron microscope) than
material treated with empty cell process and is important in decay protection (Chou et al
1973). This study shows that while this may be true for basidiomycete attack it does not
necessarily apply to soft rot decay. Lumen deposits of CCA are not necessary to inhibit
penetration of soft rot into the S2 layer and is unlikely to inhibit tunneling bacteria.
Unlike pure culture decay tests, on the basis of fungus cellar tests, preservative efficacy
is related only to preservative retention and dosage response for all three treatments
could be represented by a single curve. Furthermore this results were confirmed in a
third study in which Hedley et al (1995b) evaluated effect of treatment method on CCA
performance using Radiata pine field stakes installed in a a graveyard (loam soils and
annual rainfall of 1509 mm). Stakes were inspected at yearly intervals using AWPA M-
10 standard procedure. After 5 years statistical analysis showed no difference between
treating processes and performance was related solely to retention expressed either as
copper retention or total element (Cu+Cr+As) retention.

To study the influence of application method on preservative efficacy Newman and
Murphy (1992) treated Corsican pine (Pinus nigra) samples with CCA formulation using
Bethel, Steam/Bethel or Lowry processes. After leaching, sets of replicate mini-blocks
were exposed to the brown rot Coniophora puteana FPRL 11E, white rot Coriolus
versicolor FPRL 28A, and soft rot Chaetomium globosum FPRL S70K. Equivalent sets
of leached blocks, were analysed for preservative elements. Steaming predisposed the
wood to fungal decay and reduced efficacy. Significant differences in performance of
CCA against brown, white or soft rot decay fungi were found depending upon the
preservative application method. Differences in preservative microdistribution between
lumen surfaces and the S2 layer account for the effect of treatment method on variation
of CCA efficacy against brown, white and soft rot. When exposed to the brown rot,
wood treated by the three processes performed in the order
Bethell>Steam/Bethell>Lowry and in the order Bethell> Lowry> Steam/Bethell when
exposed to white rot. In the control of brown rot, the balance and overall level of
preservative active elements is of more importance than the preservative distribution at
cellular level. When attempting to control decay by white rot, once a threshold level of
CCA concentration within the wood has been reached, preservative distribution at tissue
levels is of paramount importance.

Newman and Murphy (1993) presents further data testing of CCA treated Corsican pine
by serial exposure in and unsterile soil to Coniophora puteana and Coriolus versicolor.
In serial exposures, blocks are re-exposed to fresh cultures with weight loss
determination leaching and resterilization between exposures. After 3 exposures
Bethell treated material performed consistently better than the Lowry treated when
wood was exposed to Coniophora puteana. After 3 exposures to Coriolus versicolor
treated wood performed in the order Lowry > Bethel > Steam/ Bethell. Lowry treated
material performed consistently better than the Bethell. Brown rot fungi will tend to be
less susceptible to the effect of CCA components distributed within the cell wall than
those deposited on the lumen surfaces (Newman and Murphy 1993). In contrast with
brown rot, white rot decay is localized around the hyphae and all cell wall polymers are
degraded. Therefore an even distribution of preservative across the thickness of cell
wall will have a constant reducing effect on the progress of white rots. Such distribution
is promoted by the Lowry process where a much greater amount of the applied CCA is
in the cell wall whereas in the Bethell, process a significant portion of the CCA remains
in the cell lumen. (Newman and Murphy 1993). CCA applied by Lowry treatments is
also considerably more effective in preventing soft rot than an equivalent retention
applied by the Bethell process. For softrots, which occurs as cavity formation in the S2
layer, a more even preservative distribution across the cellwall i.e a Lowry distribution
would be more effective than a Bethell pattern. The microdistribution data indicate a
strong correletion between S2 layer Cu and white rot and soft rot control. After a Bethell
process large amounts of CCA precipitate in the cell lumen and only a relatively small
proportion is distributed in the fiber S2 layer making the timber susceptible to soft rots
(Newman and Murphy1993, 1996; Daniel and Nilsson 1989).

Pre-treatment steaming caused a general reduction in preservative efficacy through
inherent change in wood substrate as opposed to major changes in CCA micro
distribution or fixation. This reduced performance may arise from increased decay
susceptibility of the wood substrate, chemical and physical changes in the wood which
affect CCA fixation, at treatment of the wood at 60% MC affecting the fixation and or
distribution of CCA. The chemical nature of hemicellulose, cellulose and lignin’s is
affected by steaming (Newman and Murphy 1996). Manipulation of treatment method
offers potential to enhance the spectrum of activity of CCA against parts of the decay
hazard.

Effect of Formulation type on CCA efficacy.
AWPA Type B formulations (e.g., Boliden K33) do not perform as well in NZ as type C
formulations (Tanalith C) (Hedley et al. 2000). However one long term study reported by
Ralph (1984) showed otherwise. In this study, between 1951 and 1963, Aspen poplar
fence posts full cell pressure treated with CCA-A, CCA-B and CCA-C (Tanalith C) were
installed in Ontario Canada in a park site with on sandy loam soil with 700-1100 mm
annual rainfall. Visual examination, microscopic examination, splinter tests , and a
physical test (30-Ib) horizontal force applied at breast height were used to rate the
poles on a scale of 1-6 with 1 being sound and 6 having failed in service when
subjected to the physical test. Table 2 outlines results of groundline examinations. Soft
rot was the principal cause of deterioration in the posts and rate of decay from soft rot
attack was dependent on preservative formulation and retention. Tanalith C poles at
the lower loading of 3.2kg/m3 (0.2 pcf) were in a more advanced state of soft rot decay
than posts treated with Boliden K33 (CCA-B) and Green salt (CCA-A) at near
equivalent retention. At retentions of 6.4kg/m3 (0.4 pcf) the rate of decay was about the
same for all three formulations. The rate of decay for CCA-C was higher (0.3mm/yr)
than that of CCA-B (0.17mm/year at the lower retention of 3.2kg/m3. Canadian
standards for fence posts of poplar require loading levels of 6.5kg/m3 oxides (0.4 pcf).

Table 3. Rate of decay in Aspen poplar posts treated with various CCA formulations in the test
plot at Chalk River Ontario
Preservative Year Exposure Average Average Average rate of
installed period Retention rating decay (soft rot)
(years) kg/m3(pcf) mm/year
CCA-A Green salt 1951 31 6.8 (0.43) 1.6 0.03mm or less
13.4 (0.84) 1.2 0.05mm
17.3 (1.08) 1.0 0.09mm
CCA- B Boliden 1961 22 3.1 (0.19) 1.9 0.17mm
salt 6.2 (0.39) 1.5 0.11mm
CCA-C Tanalith 1963 19 3.2 (0.20) 2.3 0.3mm
6.4 (0.40) 1.2 0.08mm

Effect of Location (environmental factors) on Efficacy
Site or location of installation of CCA treated wood has been shown to have a marked
impact on CCA effectiveness in ground. In general, this could be attributed to the effects
of temperature, water availability, soil type, and to a lesser extent vegetation and litter
type. Rainfall and soil type have an influence on decay hazard type and insect types