What Is C2 Wood?

Uses

• C2 wood is used to build a number of structures meant for exposure to marine situations. One use is in boat building. Another is bulkhead sheathing used to divide boat interiors into compartments or to construct seawalls and coastal barriers. Aquaculture -- fresh-water fish farming -- uses wood for raceways and tanks for fish culture. Mariculture -- growing seawater species of fish and shellfish -- uses wooden stakes and racks to suspend oysters in seawater. Cultured mussels are attached to stakes or wooden floating rafts. Salmon are raised in mesh raceways attached to a floating wooden frame. Highways built in salt water also use C2 wood.

Salt Water and Wood

• Exposure to salt water is hazardous to wood in various ways. Constant moisture promotes electro-chemical degradation, which occurs when an anode-to-cathode situation is created and an electrical current passes through wood. Natural anode-to-cathode situations occur between salt water–soaked wood and metals used to fasten wood, causing an alkaline reaction near the cathode material that breaks down the cellulose in wood. Organisms that attack wood in seawater include fungi and marine borers. Marine borers can destroy untreated wood in just a few years. There are two main types of borers, shipworms and gribbles. Shipworms are kinds of molluscs in the families Teredinidae and Pholadidae. They look like worms but are a clam relative. They use the paired shells at the front of their bodies to bore tunnels into wood, riddling it with burrows. Gribbles, the genus Limnoria, are tiny isopod crustaceans related to sowbugs that devour wood from the outside. They secrete an enzyme that digests the cellulose in wood.

Treatment

• For wood used in marine applications, the AWPA's preservative guides fall under Commodity Section G, special requirements 6.1-6.4. For shipworm and Limnoria control, chromated copper arsenate or CCA is used. The AWPA lists CCA Type C for use, which is composed of 47.5 percent chromium trioxide, 34 percent arsenic pentoxide and 18.5 percent copper oxide. The copper acts as a fungicide and general biocide, and the arsenic is toxic to marine wood-feeding organisms.

Current AWPA standards

• In 2003, the AWPA revised its standards. Woods are now categorized by a use category system. The former C2 standard for marine and brackish water applications is now Use Category UC5, Marine Use. This is divided into three units. UC5A, Northern Waters, covers areas north of New Jersey in the east and north of San Francisco in the west. UC5B, Central Waters, applies to areas between New Jersey and Georgia in the east and south of San Francisco in the west. UC5C, Southern Waters, covers waters south of Georgia, along Gulf of Mexico coastlines, and in Hawaii and Puerto Rico. Commodity specifications -- or requirements for specific types of wood products -- for marine or salt water applications are included in Section G of the standards.