Use of Treated Wood Products in the Construction of Floating Dock Systems

Timber Floating Docks

The perception that treated wood products are less environmentally sensitive than other available products for the construction of floating dock systems is not based on empirical data but rather opinion.

There are many hazards that threaten our natural resources and careful management of human activities is essential.  However, sustainable management carries with it a responsibility to segregate real from perceived threats and to focus our energy on the real hazards.  – Dr. Kenneth M Brooks

Wood is an ideal marine construction material for floating dock structures.  Its resilience to wind and wave exposure makes it a perfect building material for this application. Wood can’t rust, won’t corrode and is surprisingly fire resistant. Most importantly, it can bend or “deflect” an infinite number of times when loaded without weakening or yielding its strength.   In addition to wood’s inherent natural properties, its environmental benefits over other common construction materials have been documented in numerous studies and papers.  According to the USDA, “wood has a vital role to play in meeting the growing demand for green building materials.”[1]

However, for wood to meet its true potential as a sustainable building material in the marina industry, it is critical that it be properly fabricated and treated for use in aquatic environments. Without proper protection wood is vulnerable to rot, decay and destruction from marine organisms.   Use of wood preservatives is important for the longevity of structures within our marinas and the sustainability of our forests.  Long lasting treated wood products mean that docks and other over water structures will not need to be replaced or repaired as often; thus avoiding unnecessary disturbance that occurs to the environment during construction and requiring use of fewer trees.

Over the years, chemicals used to treat wood products in aquatic environments have evolved from creosote to CCA and now in the United States to ACQ and ACZA among others.  Because of the chemical properties inherent in wood preservatives there is a perception that treated wood must be bad for the environment.  But according to Dr. Kenneth Brooks, renowned researcher in the field of environmental response to pressure treated wood, empirical evidence shows that those perceptions are not the reality.

In looking specifically at the most commonly used preservatives in today’s timber dock structures in the United States, the concern with ACQ, ACZA, and other copper-based preservatives is the potential migration of copper into the water column and sediment.  At high concentration levels copper is toxic, so the concern is valid.  The question is how much copper is leached from docks built from treated timber and are they a threat to the health of our waters.

Results from studies performed by Brooks and others clearly show that in reasonably well-flushing areas the contribution of dissolved copper from timber dock structures to the aquatic environment is so small it is undetectable in the real world and has no negative effects on the ecosystem surrounding the structure[2].  However, the wood preservative industry does caution that at project sites where water and/or sediment copper concentrations exceed acceptable levels the decision to use pressure treated wood products containing high levels of copper in the construction of large scale marina projects should be made with a thorough understanding of the contributing factors at the site.

Treated timber is an important building material within the marina industry and a critical component in the construction of high performance, long lasting floating dock systems.  Its use as a truly sustainable product is just beginning to gain the attention it deserves and should be safeguarded by the industry.  The perception that treated wood products are less environmentally sensitive than other available products for the construction of marinas is not based on empirical data but rather opinion and clever marketing.  Reality rather than perception should drive our decision making processes – otherwise we deny ourselves the use of products needed for achieving true sustainability.

The facts are:

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[1] Science Supporting the Economic and Environmental Benefits of Using Wood and Wood Products in Green Building Construction; Michael A. Ritter, Kenneth Skog and Richard Bergman; 12-2011.

[2] The affects of dissolved copper on salmon and the environmental affects associate with the use of wood preservatives in aquatic environments; Dr. Kenneth M. Brooks; Dec. 2004 (WWPI website).

[3] Timber as a sustainable building material; Forest and Wood Products Research and Development Corporation; Australian Government.