Wood preservation is one of the oldest construction technologies, and chromated copper arsenate, or CCA, remains its workhorse for severe exposures. A Louisiana sawmill recently proved how far the process has come when its new treating plant started production in Bunkie, treating 8,500 board feet per cycle and up to 170 MBF per day with a single operator. Water chemistry shows up elsewhere on the job site too, because treating acidic well water protects plumbing just as preservatives protect lumber.
CCA left residential decking and play structures in the early 2000s under a voluntary agreement with the EPA, but it never left construction. Utility poles, marine piles, agricultural posts, and highway structures still rely on it, and the new plant is equipped to run several water-borne preservatives, so the same line can switch chemistries as demand shifts.
What CCA Treated Wood Is and Where It Is Used
CCA is a blend of three metals: copper acts as a fungicide, arsenic as an insecticide, and chromium binds the other two to the wood so they do not wash out. The chemicals are dissolved in water and forced deep into the lumber under pressure, which is why the process is called pressure treating. Performance is measured by retention, the pounds of preservative per cubic foot of wood, and by penetration, how deep the treatment reaches.
Residential vs. Commercial and Industrial Use
The residential line in the sand dates to December 2003, when manufacturers agreed to stop selling CCA-treated wood for most consumer uses such as decks, playgrounds, and picnic tables. The products that replaced it in stores are copper-based systems like ACQ and copper azole. CCA kept its place in commercial and industrial applications where the exposure is severe and the service life is measured in decades.
Current CCA applications include:
- Utility poles and crossarms.
- Marine bulkheads, piers, and saltwater piles.
- Agricultural posts and vineyard stakes.
- Highway guardrail posts and bridge components.
- Heavy foundation timbers in industrial buildings.
Retention Levels and Standards
The American Wood Protection Association publishes retention standards that specifiers should read before buying. A post intended for ground contact needs higher retention than a board used above grade, and marine exposure demands the highest loadings of all. Homeowners fighting moisture in crawl spaces apply the same logic, which is why conditioned crawlspace construction keeps framing dry and rot-free.
| Application | Typical CCA retention (pcf) | Expected service life |
|---|---|---|
| Above-ground members | 0.25 to 0.40 | 20 to 30 years |
| Ground contact (posts, sills) | 0.40 to 0.60 | 30 to 40 years |
| Utility poles | 0.60 to 0.80 | 40 to 60 years |
| Marine saltwater piles | 2.50 | 40 years and up |
How a Modern Treating Plant Operates
The Bunkie, Louisiana, installation is described by its equipment supplier as the first turnkey CCA plant in the United States with fully automatic, one-man-operated material handling. The numbers show what automation buys: 8,500 board feet per cycle, up to 170 MBF per day, and roughly 4,760 MBF per month, all with one operator on the line. At 28 production days per month, the daily figure multiplies out to the monthly total, and every cycle is logged for the quality record.
The Treatment Cycle Step by Step
- Lumber is stacked on charge cars with stickers between layers.
- The charge rolls into a horizontal treatment cylinder.
- A vacuum pulls air out of the cylinder and the wood cells.
- Preservative solution floods the cylinder.
- Pressure in the 140 to 175 psi range forces solution into the cells.
- The cylinder drains and a final vacuum recovers excess solution.
- The charge rolls out for storage while the treatment fixes in the wood.
Automation and One-Operator Lines
Automatic handling replaces the crew that used to load and unload cylinders by hand, and it improves safety by keeping workers out of the path of moving charges. One operator monitors the cycle from a control room, and the same system logs pressure, temperature, and solution strength for every batch. Rural economies across the region, including the secluded towns in northeast Louisiana, depend on mills like this one for jobs and local spending.
Modern plants also recover solution from every cycle, and the closed-loop design keeps preservative out of storm drains. Spent solution is filtered and reused, and treated lumber carries handling guidance: sawdust from cutting should not be burned, and offcuts belong in approved disposal streams. For scale, 170 MBF per day is enough treated lumber to frame more than a dozen typical houses, and the one-operator line produces that volume without the manual handling crews that older plants needed.
Water-Borne Preservatives Compared
CCA competes with newer copper-based preservatives in the treating market, and the choice changes fastener requirements and cost. ACQ, alkaline copper quaternary, and copper azole dominate residential treating, while CCA remains cost-effective for industrial volumes.
Reading a Preservative Label
- Active ingredient: the chemical system and its concentration.
- Retention: pounds per cubic foot, matched to the use class.
- Use category: UC1 through UC5 defines the exposure the wood is rated for.
- Standard: the AWPA or building code reference the treatment follows.
Moisture and the Structures Around Treated Wood
Preservative choice is only half of moisture management. Moisture does not stop at lumber; masonry suffers too, and contractors spend years understanding and treating damp masonry in older buildings before they learn to read the warning signs quickly.
| Preservative | Active ingredients | Typical uses | Fastener guidance |
|---|---|---|---|
| CCA | Copper, chromium, arsenic | Poles, marine, agricultural | Standard galvanized works |
| ACQ | Copper, quaternary ammonium | Decks, ground contact | Stainless or hot-dip galvanized |
| Copper azole (CA/MCA) | Copper, azole | Decks, framing | Hot-dip galvanized or stainless |
| Borates | Boron compounds | Interior, above ground | Non-corrosive |
Cost per cubic foot is a real differentiator. CCA is typically the least expensive water-borne option at industrial volumes, while micronized copper systems command a premium that residential buyers accept for handling and appearance. The gap narrows once fastener upgrades and corrosion allowances are priced in, which is why a full installed-cost comparison beats a chemical price sheet.
Ground Contact, Moisture, and Service Life
The harshest ordinary service for treated wood is ground contact, where soil moisture, fungi, and insects attack at once. The AWPA use classification system divides exposures into categories that specifiers should match to the product, because a board rated for dry interior use will fail quickly in wet soil. Field studies of utility poles show average service lives of 40 years or more in most climates, and treated marine piles routinely pass the half-century mark in brackish water.
Use Classifications That Drive Specification
- UC1: interior, dry, protected from weather.
- UC2: interior, damp, some moisture exposure.
- UC3: exterior, above ground, protected from water trapping.
- UC4A: ground contact, general use.
- UC4B: ground contact, high decay hazard.
- UC4C: ground contact, extreme hazard such as heavy agricultural use.
- UC5: marine, saltwater and freshwater exposure.
Fastener Compatibility
CCA’s chromium fixation keeps the treated wood relatively gentle on fasteners, one reason it survives in industrial service. Copper-based replacements are harder on metal, so decks and ground-contact structures need hot-dip galvanized or stainless fasteners and connectors. Sealing the building envelope matters as much as treating the wood; the same reasoning behind crawlspace conversion, turning a vented crawl space into a conditioned space, keeps moisture away from floor systems.
Fire Retardant Treatment and Other Chemical Processes
Pressure treatment is not limited to preservatives. Fire retardant chemicals can be driven into wood the same way, and the two processes answer different threats: preservatives fight decay and insects, while fire retardants slow ignition and flame spread. Roofing is the classic example: cedar shakes and shingles can be upgraded with fire retardant treatment to satisfy wildfire codes, and the same pressure cylinder that applies preservatives can run the flame-retardant chemistry.
Preservative vs. Fire Retardant: Know the Difference
- Preservatives extend service life against biological attack.
- Fire retardants reduce flame spread and heat release.
- Some treatments combine both, but each is tested against its own standard.
- Field-cut ends and drilled holes need brush-on preservative to restore protection.
Inspection and Maintenance of Treated Wood
- Check for splits and cracks that expose untreated interior wood.
- Re-treat field cuts with a brush-on preservative approved for the chemistry.
- Keep treated members out of standing water where possible.
- Log treatment tags and retention certificates for warranty and inspection records.
Louisiana contractors see the full range of material care on their sites, from treated posts to asphalt. The flexible equipment that expands pavement preservation capabilities on one project is the same mindset a mill applies when it automates a treating line: do more work with fewer hands and fewer callbacks.