Selecting Preservatives for Marine Structural Timber in Herring Spawning Areas

AIDC project number: 410037


Robert A. Perkins (UAF)

  • US Department of Transportation (RITA)
  • Alaska Department of Transportation & Public Facilities
  • Washington State University
  • University of Alaska Fairbanks
  • Start Date: Jul 1, 2010
  • End Date: Jun 30, 2012

Project Summary

Alaska marine harbors use wood for many structures that come in contact with saltwater, including piles, floats, and docks, because it is economical to buy and maintain. However, wood immersed in saltwater is prone to attack by marine borers, various types of marine invertebrates that can destroy a wood structure in only a few years. In Alaska marine waters there are only two wood preservatives currently recommended: ACZA (ammoniacal copper zinc arsenate) and creosote. ACZA is a water-based preservative that leaches copper into the marine environment, copper is toxic to marine invertebrates and other species. Creosote is an oil-based preservative made from coal tar, it leaches a class of hydrocarbon chemicals called polycyclic aromatic hydrocarbons into the water. Some research indicates that copper leaching from ACZA is slight after a year or so, while creosote leaches PAH at a declining rate over time, but is still measurable after many years. Field research with both preservative methods is hampered because harbors are frequently contaminated with many chemicals, so determining how the wood preservatives alone impact marine life over time is difficult. This project will test the toxicity of marine structural materials to herring eggs under a variety of conditions common in Alaska marine waters, focusing on Southeast Alaska, it will also compare the durability of creosote-versus ACZA-treated marine timbers under comparable climatic and service conditions. This research aims to provide relevant information to ADOT&PF to improve its selection of wood structural materials in the marine environment, especially the selection of wood-preserving methods.