THE PROBLEM 



Investigate and report on factors in physical oceanog- 

 raphy which pertain to underwater sound and develop tech- 

 niques to expedite these investigations. Specifically, install 

 on the shallow ocean floor adjacent to the NEL oceanographic 

 research tower a circular array of stanchions capable of 

 supporting transducers at prescribed positions in the water 

 column over a long period of time for the study of internal 

 waves. 



RESULTS 



1. Forty- eight stanchions have been accurately placed by 

 NEL divers on the sea floor off Mission Beach, California, 

 in 62 to 64 feet of water. Spaced 29 feet apart, they form a 

 circle with a circumference of 1395 feet. Each stanchion 

 consists of three telescoping sections of galvanized pipe. 

 The base sections, with three vertical fins welded to them, 

 were injected approximately 4-1/2 feet into the sediments 

 by high-pressure water directed through the pipe and into 

 the bottom. The stanchions are used to support thermistor 

 beads at 30-foot depths. The array is presently in use in 

 conjunction with the internal-wave and underwater- sound 

 studies being conducted by the NEL Marine Environment 

 Division. 



2. Over a 15-month period, the vertical and horizontal 

 positioning of these stanchions has remained virtually un- 

 changed, attesting to the stability of this type of installa- 

 tion. Other successful applications of this technique have 

 been made. The equipment and diving procedures developed 

 for this job are applicable to other underwater engineering 

 problems. 



MBL/WHOI 



0301 OOMOSOT A 



