Chemonite is a waterborne preservative made of metallic oxides of copper, zinc and arsenic in an aqueous ammonia solution, developed by University of California researchers in the 1920s specifically for difficult-to-treat western softwoods. Chemonite must be applied by an approved, licensed pressure-treating plant, such as Conrad Forest Products. We are required to test each shipment for compliance with American Wood-Preservers Association Standards to meet applicable building-codes for quality-penetration and retention. An ALSC accredited Third-party inspection agency continually monitors our plant’s output and testing procedures.
Other waterborne preservatives cannot consistently meet accepted standards of penetration and retention in Douglas Fir, green or dry, or in green hemlock. So when you choose Chemonite treated wood from Conrad Forest Products you minimize risk and maximize return in the form of longer service life, better appearance and easy handling.
Today’s Chemonite® contains a 2:1:1 ratio of copper oxide, zinc oxide and arsenic pentoxide, respectively. The arsenic component remains in the wood preservative solution because of its proven insecticidal and fungicidal properties. This reduction to one-half the amount of arsenic found in the original formulation provides the lowest level of any arsenical-type preservative system approved for wood treatment by the American Wood-Preservers’ Association.
The individual components are blended to produce the Chemonite®ACZA preservative which is designed to do several things:
The addition of zinc not only reduced the arsenic level by one half, but it also provided a second metal cation, which is important to establish the stability of the chemical inside the wood. This mechanism is referred to as FIXATION. It involves the attachment of the preservative components once soluble in water, to the cells of the wood or each other, thus making them insoluble to water after fixation occurs. This fixation of the chemical allows the waterborne preservative systems to be used successfully even in aquatic environments without extreme amounts of chemical being washed out during exposure.
Scientific information is available to support the claims of chemical fixation preventing the leaching or loss of the preservative. The Oregon State University did a recent study in a wetland area using Douglas fir decking and timbers treated with Chemonite®ACZA.
The material installed for this test indicated an insignificant loss of chemical showing little change from the natural background levels established for these sites.
The material for this test was produced using Best Management Practices (BMPs) which are guidelines established by the Western Wood Preservers Institute to reduce the effects of treated wood when used in environmentally sensitive or aquatic environments. These BMPs are used at the treating plant to produce material having little or no surface residue, chemical levels specific to exposure condition, and accelerated fixation of chemical in the wood to minimize leaching.
Exposure studies of ACZA treated wood in soil by Texas A&M Laboratory concluded ACZA is not harmful for garden use finding only natural levels of arsenic in the soil beds contained by treated timbers for 9 years. In addition the US Forest Products Laboratory has over forty years of research showing no evidence of sufficient chemical depletion that would pose a risk to human health or the environment.
Scientific evidence is available to prove the preservative chemical becomes stable in the wood, providing a product that is safe for human health and having no detrimental effects to the environment, but questions continue to be raised about its safety. If you have concerns about a specific application of Chemonite® ACZA material for your project, or would like to have additional information, please contact Conrad Forest Products. We will be happy to assist in getting the information you need to make an informed decision.
|AWPA Standards||Preservative Retention|
|U 1||C||(Lbs. per cubic foot)|
|AGRICULTURE, FARM USE||Round poles and posts as structural members||4B||C4, C16||.60|
|Sawn poles and posts as structural members||4B||C2, C16||C2, C16|
|Round, half & quarter round||4A||C5, C16||.40|
|Sawn four sides||4A||C2, C16||.40|
|BUILDING CONSTRUCTION, MARINE AND FRESH WATER||Floor plate||2||C2, C15,||.25|
|Framing, interior||1, 2||C2, C15||.25|
|Lumber & Timbers:|
|Interior, above ground||1, 2||C2, C15||.25|
|Exterior, above ground||3B||C2, C15||.25|
|Ground contact and fresh water use||4A||C2||.40|
|Salt water splash||4B||C2, C14, C18||.60|
|Subject to tides, waves or in salt water||5B||C2, C14, C18||2.50|
|Permanent Wood Foundation:|
|Lumber & Plywood||4B||C22||.60|
|Sub-floor, damp above ground||2||C9, C15||.25|
|Exterior, above ground||3B||C9, C15||.25|
|Ground contact and fresh water use||4A||C9||.40|
|Salt water splash||4B||C9, C14, C18||.60|
|Subject to tides, waves or in salt water||5B||C9, C14, C18||2.50|
|Round piling – severe exposure||5B||C3, C14, C18||2.50|
|Round piling – northern waters||5A||C3, C14, C18||1.50|
|Round piling – land & fresh water||4C||C3, C14||1.00|
|Round – structural||4B||C4, C23 C23||.60|
|Sawn – structural||4B||C2, C15, C24||.80|
|DECKS||Above ground: Decking, joists, rails, steps||3B||C2, C15||.25|
|Ground contact: Posts||4A||C2, C15||.40|
|HIGHWAY MATERIAL||Lumber and timbers for bridges, structural|
|members, decking, cribbing, & culverts||4B||C2, C14||.60|
|Structural lumber and timbers:|
|Posts: Round, half-round, quarter round||4A||C5, C14||.40|
|Posts: Sawn||4A||C2, C14||.40|
Construction: Borers, termites and decay can attack treated wood when the heavily treated outer layer is removed. It is recommended that all structures be prefabricated before treatment. Minimize problems by specifying framing and boring before treatment whenever possible. Bracing with round timber piles rather than sawn timbers is recommended below high tide. All untreated wood exposed by cutting or drilling should be adequately field treated.
Fasteners: Around water, avoid corrosion by specifying all timber products are properly air seasoned or kiln dried prior to installation. Always use hot-dipped galvanized or stainless steel hardware.
Worker Safety: Chemonite treated wood can be stored, handled and worked like untreated wood. As with any wood, wear gloves to avoid splinters, wear eye protection and a dust mask when sawing, drilling and sanding. Wash hands before eating or smoking. Dispose of cut ends in a sanitary landfill. Treated wood should not be burned in open fires or in stoves, fireplaces or residential boilers. Treated wood from commercial or industrial use may be burned only in commercial or industrial incinerators or boilers in accordance with state and federal regulations.
Protection of the quality of the water and diversity of the various life forms found in the lakes, streams, estuaries, bays and wetlands of North America is a goal and responsibility shared by every citizen. An endless list of human activities can impact the aquatic environment: storm waters that run off our streets, exhaust from our boats and cars, municipal and industry discharges, and construction of docks and piers, to name but a few. Maintaining the quality of our treasured aquatic resources requires that everyone do their part.
Pressure treated wood is a major material used to construct the piers, docks, buildings, walks and decks used in and above aquatic environments. The pressure treated wood products industry is committed to assuring its products are manufactured and installed in a manner which minimizes any potential for adverse impacts to these important environments. To achieve this objective the industry has developed and encourages the use of BEST MANAGEMENT PRACTICES or BMPs.
There are four steps to assure products utilized in aquatic environments incorporate BMP produced materials.
Ammoniacal Copper Zinc Arsenate (ACZA) is an improved preservative that replaces half of the arsenic in ACA with zinc. This preservative is suitable for treating difficult woods such as Douglas fir. The naturally occurring arsenic, copper and zinc metals used in ACZA are fixed to the wood fibers following evaporation of an ammonia carrier. However, small amounts of metal do leach from preserved wood during the early stages of immersion. The ACZA risk assessment clearly shows that copper is the metal of concern in aquatic environments. While copper is not a human toxicant (the water pipes in our homes are made of copper), it can be toxic at levels as low as six parts per billion to the embryos of sensitive bivalves and echinoderms. An exhaustive review of the published literature indicates that the EPA’s fresh and marine water quality criteria for copper are adequate to protect all aquatic life.
Unlike the sediment concerns with PAHs found in creosote, dissolved copper presents the highest risk to aquatic organisms. Literature reviews and the predictions made by the ACZARISK computer model suggest that if water column levels of copper are maintained below EPA water quality copper criteria, then sediment levels of copper, zinc and arsenic will be well below thresholds associated with stress or disease.
Slightly more copper is lost from ACZA treated wood during the first week to 10 days than is lost from CCA treated piling. However, metal losses decline more quickly in ACZA treated wood, and reach very low values in less than two weeks. The ACZA model predicts that minimum current speeds (measured three hours before or after slack tide on an exchange to mean low water) of 1.0 cm/sec are sufficient to insure that copper losses from a single ACZA treated piling do not elevate marine water copper concentrations by an amount equal to the EPA marine water quality criteria (2.9 ppb).
In constantly running water, such as rivers, a minimum current speed of 0.5 cm/sec is required to meet EPA fresh water quality criteria (assuming background copper levels are at 1.5 ppb. Very few rivers and streams have current speeds this slow. Even backwater estuaries typically have current speeds greater than three or four centimeters per second. The 1.5 ppb background copper level is typical of western rivers such as the Columbia River.
Bulkheads treated with ACZA pose a different problem and the models predict that EPA water quality standards can be exceeded during the first few days following installation when steady state current speeds are less than 18.5 cm/sec in fresh water and when maximum tidal currents are less than 13 cm/sec in marine environments. These are typical current speeds in open rivers and marine environments. However, currents slower than these can be encountered in quiet riverine backwaters and protected marine embayments. We recommend a site specific risk assessment whenever an ACZA bulkhead is proposed for use in the water.
Leaching data indicates that metal losses from ACZA treated wood are time dependent, and that losses are very small after one or two weeks. When large surface area ACZA projects are proposed at poorly circulated sites, the project should be constructed during that time of year when sensitive aquatic species, including migrating salmon, are not present (usually in winter). In addition, these are generally seasons of increased water circulation due to wind and wave action.
It is the view of the Western Wood Preservers institute and the Canadian institute of Treated Wood that, based on the best available scientific information, the combination of the AWPA treating standards and BMPs for Creosote, CCA, ACZA, ACA, ACQ, Copper Naphthenate and Pentachlorophenol will produce products that provide excellent environmental performance in most open aquatic environments. Projects calling for large volumes of treated wood immersed in (i.e., below the splash zone) poorly circulating bodies of water should be evaluated on an individual basis utilizing risk assessment procedures. The Institutes will assist treated wood users in determining when a risk assessment is needed and in providing documentation to assist in the completion of a risk assessment, when required.
Dr. Kenneth M. Brooks from Aquatic Environmental Sciences has produced a study entitled ‘Environmental response to ACZA treated wood structures in a Pacific Northwest marine environment’ for J.H. Baxter and Company, the Licensor for ACZA.
Dr. Brooks has concluded, “Overall, this study did not find any adverse effects associated with the use of ACZA preserved wood on the Pacific Northwest marine environments studied”. The following link will open the entire 31 page study: EnvResptoACZAPacific.pdf. Additional information regarding The Use of Treated Wood in Aquatic Environments is available from the Western Wood Preservers Institute at www.wwpinstitute.org.
There is no current wood treatment available that can effectively protect Douglas-Fir heartwood against the Formosan subterranean termite. Several tests were conducted to determine whether ACZA could protect Douglas-Fir heartwood against the Formosan subterranean termite.
NOTE FLAME SPREAD CLASSIFICATIONS:
CLASS I 0 – 25 FLAME SPREAD
CLASS II 26 – 75 FLAME SPREAD
CLASS III 76 -200 FLAME SPREAD
DOUGLAS FIR TREATED TO A RETENTION OF .40 LBS. PER CUBIC FOOT TESTED AT THE UNDERWRITERS LABORATORIES PASSED CLASS II FLAME SPREAD REQUIREMENTS THE PRELIMINARY TESTS INDICATE ABOUT 1/2 THE NORMAL FLAME SPREAD OF UNTREATED DOUGLAS FIR WHICH IS 70 TO 100. DOUGLAS FIR WHEN TREATED WITH ACZA TO A RETENTION OF 2.0 PER CUBIC FOOT WILL PASS CLASS I REQUIREMENTS.
REDWOOD TREATED TO .60 LBS. PER CUBIC FOOT AND TESTED AT THE UNDERWRITERS LABORATORIES PASSED CLASS II FLAME SPREAD REQUIREMENTS. THE PRELIMINARY TESTS INDICATE 1/3 THE NORMAL SPREAD OF UNTREATED REDWOOD. THE PRELIMINARY TESTS ALSO INDICATE THAT REDWOOD TREATED WITH ACZA TO A RETENTION OF 2.0 LBS. PER CUBIC FOOT WILL PASS CLASS I.
THESE PRELIMINARY TESTS AT THE UNDERWRITERS LABORATORIES CONFIRM AND DOCUMENT THAT ACZA PRESSURE TREATMENT OF DOUGLAS FIR OR REDWOOD ENHANCES THE FIRE RESISTANT QUALITIES OF THE STRUCTURE WHEN SPECIFIED AND USED.