PREFACE 



The U. S. Naval Civil Engineering Laboratory is conducHng a research 

 program to determine the effects of the deep-ocean environment on materials. This 

 research will be of great value in establishing the best materials to be used in deep- 

 ocean construction in the Navy's conquest of "inner space." 



A Submersible Test Unit (STU) was designed on which many test specimens 

 can be mounted. The STU can be lowered to the ocean bottom and left for long 

 periods of exposure. This report deals with STU 1-4, in place for 13 months at a 

 depth of 6,800 feet. The test site is about 81 nautical miles southwest of Port 

 Hueneme, California. 



