Knowledgebase

Building Floating Dock on Pond #877683

Asked July 17, 2024, 4:53 PM EDT

Hello I am preparing to build a floating dock on my pond. The pond isn't *techincally* a pond. A year round, spring fed creek flows in to the pond, the over flow is directed down a concrete spillway, into a culvert, and underneath the road, where the creek continues to the Lukiamute River. The pond is approx. 4000 sq. ft in area and has a perimeter approx. 240 ft. The creek flows year around, though is a trickle in September. I plan to swim in the pond and stock it with fish, as it is very deep (>10ft) in the middle areas. I am worried about building the floating dock frame with pressure treated wood. There is already frogs and newts in the pond. The frame would be above the water 100% of the time, not submerged, as the barrels would keep it up and out. The deck would be trex composite. I am a little worrried about rain leaching the chemicals out of the PT wood. Should I be? Would this harm wildlife, either in my pond, or downstream? The frame with Trex would be upwards of 2500, so PT is much more cost effective. Cedar and redwood, though rot resistant, I fear would not last long in the year round elements of the Kings Valley area. Thank you.

Benton County Oregon

Expert Response

Hi there,

Decking/framing of docks composed of pressure-treated wood has been shown to leach heavy metals into the aquatic environment through weathering and rainfall. For this reason, the Oregon Department to Fish and Wildlife recommends not to use pressure treated wood for the construction of residential docks, including framing materials. In these guidelines, “Treated wood" means lumber, pilings, and other wood products preserved with alkaline copper quaternary (ACQ), ammoniacal copper arsenate (ACA), ammoniacal copper zinc arsenate (ACZA), copper naphthenate, chromated copper arsenate (CCA), pentachlorophenol, or creosote. That said, the adverse impact of leaching to aquatic organisms is not expected unless the environmental concentrations of the compounds reach levels of concern for the organisms(s) present, and this is dependent on factors such as time since construction, type of preservative, volume of wood used, amount of precipitation, and volume and flow rate of the receiving water body. Comprehensive reviews of treated wood impacts have indicated that environmental concentrations from most treated-wood structures are unlikely to reach levels of concern, and there are other trade-offs to consider when considering other materials. If you are interested in learning more about these reviews and trade-offs, here are some references to consider:

Logan, J. M., Boeri, A., Carr, J., Evans, T., Feeney, E. M., Frew, K., Schenck, F., & Ford, K. H. 2022. A Review of Habitat Impacts from Residential Docks and Recommended Best Management Practices with an Emphasis on the Northeastern United States. Estuaries and Coasts, 45(5), 1189-1216. https://doi.org/10.1007/s1<personal data hidden>6-0

NOAA Fisheries. 2009. The use of treated wood products in aquatic environments: Guidelines to West Coast NOAA Fisheries staff for Endangered Species Act and essential fish habitat consultations in the Alaska, northwest and southwest regions. Longbeach, CA: National Oceanic and Atmospheric Administration Fisheries, Southwest Region. 58 p.

Other References:

Lebow, Stan T.; Tang, Juliet D.; Kirker, Grant T.; Mankowski, Mark E. 2019. Guidelines for selection and use of pressure-treated wood. General Technical Report FPL-GTR-275. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 39 p.




An Ask Extension Expert Replied July 22, 2024, 2:03 PM EDT

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