15-50% of the wood was lost. In addition, the adult shipworms appeared to be able to survive boring 

 through the lower concentrations of CCA, which existed beneath the treated surfaces of the timbers. 

 Woodborers were never observed penetrating the treated outside surfaces of a timber. The total protection 

 of creosote timber from wood-loss in 1983 and 1985, resulted from the effective penetration of this chemical 

 (20 lbs/cm ) throughout the interior wood grain of each timber. Other studies have concluded that the 

 CCA and creosote treated woods are very effective at deterring marine woodborers (Baechler et al. 1970; 

 Johnson 1977; Richards 1977, 1979; Johnson and Gutzmer 1981). Creosote (20 lbs/ft^) and CCA 

 (1.0 lbs/ft ) have been reported to withstand woodborer attacks for eight years, while test panels and piles 

 with very high retentions of CCA (2.5 lbs/ft ) have been reported to repel woodborers for 25 years (letter 

 from W.T. Henry to J.D. Land, Koppers-Hickson Canada, Ltd., 1976). In their studies small test blocks 

 were used and treated after being cut. In the present study, we used products and treatments available to 

 local builders. 



Aruiually, there was a threefold greater loss of wood from Douglas Fir timbers than from Red Oak 

 timbers. Although Douglas Fir is seldom used in marine construction, oak planking and pilings are often 

 used locally. The reduced wood-loss as observed for Red Oak is the reason hardwoods have been used 

 in dock building. Oak pilings are much larger than our timbers and are set with the bark still on the tree, 

 which provides additional protection from wood-borers. However, untreated woods in the local marine 

 environments are readily attacked by borers. 



Wood-loss varied from site to site, and FI had the least wood-loss of any of the sites sampled. 

 However, Red Oak timbers at EF lost over twice as much wood when compared to the Red Oak timbers 

 at ambient water sites. This was in contrast to data collected at EF using exposure panels, where wood-loss 

 of panels at EF never exceeded that observed at ambient water sites. The reason for this discrepency was 

 related to the location of the panels versus that of the timbers. Timbers were deployed directly on the 

 bottom, while the EF panels were suspended off the bottom. Even the lower frame and rack assembly 

 of panels deployed at EF was approximately one meter higher in the water column thcin were the timbers. 

 The fu-st inch of the timbers was usually embedded in the bottom sediments, which was the reason the 

 first section of the timbers was routinely discarded during processing. Therefore, the greater annual 

 wood-loss in timbers was caused by shipworms setting most heavily at the mudline, an occurrence 

 documented by others (Grave 1928; Scheltema and Truitt 1956; Turner 1966; Nair and Saraswathy 1971). 



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