Pilings to Resist Marine Borers

Untreated wood is vulnerable to attack when submerged in ocean water. But CCA-treated wood is still allowed for use as salt-water pilings. November 28, 2006

Question
I have a dock that is made of ipe and a type of iron bark (not sure which one, but it was expensive and supposed to have been resistant to marine borers). It has suffered severe damage from marine borers and we are thinking of replacing it and are discussing options. I'm leaning toward some sort of fiberglass or plastic material, but cost may prove prohibitive. The dock is two pontoons, 3 feet by 16 feet, with a submerged section that is 10 feet by 16 feet that is ramped to shore to accommodate the tide changes. Flotation is from 16 30 gallon barrels built into the pontoon sections. After reading the Knowledge Base articles on the subject, it seems that if we go with some sort of wood product, the best way to treat it is with copper arsenate and then creosote. Where is this type of treated wood available and are there any other options?

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
Almost every saltwater marine dock and pier repair facility will have the material you need. It is our only option when using wood in this high risk environment. Note that CCA is approved for this use still.

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From contributor B:
CCA is still available for docks in the USA. A lumber company, power company or fence company will probably be able to direct you to a local treating facility. Here, when currents aren't too strong, large diameter PVC pipe, jetted into the bottom and filled with concrete, is often used for projects like you describe.

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From the original questioner:
Thanks for the info. After reading ever deeper into the Knowledge Base on the different type of treatments, CCA type 3 seems to be the best option, followed by a liberal coat of anti-fouling paint. The dock in question is in Hawaii and we don't have any local treatment facilities, as all our lumber is treated specially for our environment to strict standards before it is shipped over. I will have to do some research as to the type of treatments they do. Off-the-shelf lumber here may do the trick. I do like the PVC idea, but our dock has to float. I could build the whole frame out of PVC pipe and get extra buoyancy just from the frame itself?

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From contributor G:
Our small city of Belfast, Maine replaced a large number of pilings in late 1999 or 2000, and used untreated white oak for the new ones. At the time, shipworms had not been seen in this part of the coast.

After 18 months, all of the new pilings had been substantially damaged by the shipworms, and all of them had to be replaced. The University of Maine offered up some solutions of fiber reinforced plastics, but I think in the end the city went with imported greenheart pilings, and there has been no damage since.