c. It is imperative that all steel or concrete deck framing be located 

 above normal spray level. 



d. Untreated timber piles should never be used in waterfront structures 

 unless located below the permanent wet line and protected from marine 

 borer attack. 



e. The most effective injected preserscative appears to be creosote oil 

 having a hirh phenolic content. For piles subject to marine borer 

 attack a ma:cimum penetration of creosote-coaltar solution is recom- 

 mended, 



f . Salt-treated timber gives satisfactory service when protected from 

 the './eather. 



g. Spring and cutting of piles after treatment should be avoided. All 

 surfaces so cut require special treatment. 



h. Single timber caps have a longer lix'e than pairs of cap timbers dapped 

 into the piles. 



i. Untreated timber iles i/hen encased in a gunite armor and properly 

 sealed at the top v\rill give economical service. 



j. Concrete to last in the tide zone must have a high cement content; 

 a minimum of 6-1/2 bags per cubic yard is recommended. 



k. The lower the water-cement ratj.o, the more durable concrete will be 

 in salt water. 



1. Care must be exercised in the selection of coarse and fine aggregates 

 both for density of grading and to avoid unfavorable chemical reaction 

 with the cement. 



m. iiiaintenance of specified clear cover over all reinforcing steel is 

 of the greatest importance. 



n. Smooth formv:ork and rounded corners improve the resistance of con- 

 crete structures, 



o. All steelavork in and above the tide range requires the initial pro- 

 tection of a coating or concrete envelope. 



Conclusions 



The battle against deterioration may never be completely won. However, 

 the life of marine structures can be significantly extended by applying 

 the lessons learned from experience to their design. 



Further progress awaits the discovery of more effective protective materials 

 and the development of new methods for marine borer control. 



The sad fact that little progress has been made in the last 7^ years 

 should be a challenge to us all, , 



G -17 



