Section 3k 

 SITKA, ALASKA — U. S. NAVAL AIR STATION 



A34.01 Location of the Test Station and Test Board 



A test board of the panel type, designated by the symbol 

 lBNSA-1, vas operated at the U. S. Naval Air Station at Sitka, Alaska, 

 from November 15, 19^^ lontil August l6, 191+6, when it was discontinued 

 because of the transfer of this Station to the Alaskan Native Service. 

 The test board was installed on the outside corner of the Harbor Island 

 Gravel Bunker Dock, about 6 ft from an airsenious-trioxide-treated pile. 

 This location exposed it to the tidal currents of Sitka Harbor. 



The complete destruction of summer-cut Sitka spruce (with betrk 

 off) by Teredo action was reported to be a matter of record at this 

 Station. In order to combat this destruction of wooden marine struc- 

 t\ires, two types of treatment have been used on piling. The piling of 

 the New Navy Dock was treated with arsenioas trioxide, copper sulphate, 

 and zine sulphate. In April 19^6, it was stated that a recent inspec- 

 tion of this piling showed no Teredo action, and it was reported to 

 be sound. The pier at Old Sitka is a partially completed, cancelled 

 project. The piling used for this structure was treated by an elec- 

 trolytic open- tank process, in which copper sulphate, sulphviric 

 acid, and other chemicals were \ased. A small boat recently broke off 

 a sturdy-looking pile to which it was tied. The ensuing curiosity 

 lead to taking out several samples of electrolytic-treated piling. It 

 was found that all such piling was completely destroyed in less than 

 2 years after installation. The electrolytiq open-tank process is 

 considered valueless against Teredo activity in this area. Figure 7 

 shows considerable action on the exterior of an electrolytic, copper- 

 sulphate -treated pile, and figure 8 shows the interior of the sajne 

 pile completely riddled, with full-grown Teredos in view. 



It is a matter of record that other installations with this 

 treatment have failed within a comparatively brief period. 



A34.02 Hydrographic Data 



The depth of water where the test board was installed was 

 10 ft at mean low water; the range of tide was 11 ft; the current 

 was one -fourth knot. The temperature of the water at the time of 

 installation was ^7° F. The average salinity of the water was ap- 

 proximately 1,^50 grains per gallon. The local pollution was sai'd 

 to be zero. 



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