Placement and Recovery System . A special "mooring" system, as shown 

 in Figure 9^ has been used to assure the relocation and recovery of the 

 STU at the end of the test period. Relocation and recovery relies on 

 the use of precision electronic surveying equipment to place the retrieval 

 vessel directly over the emplacement site. Actuation of the acoustic 

 command link, noted in Figure 9> will cause the sinker to be jettisoned 

 and will allow the submerged buoys to float up to the surface for attach- 

 ment of lifting gear. A number of alternative recovery methods have 

 been incorporated in the mooring and retrieval system. 



This installation does not use a surface marker because: (l) sea 

 conditions at the site would probably cause it to be swept away; (2) past 

 experience has indicated that irresponsible mariners would very likely 

 sink or remove it; (3) it would provide a hazard to navigation; and 

 (k) since the site is in international waters^ a surface buoy would 

 provide a marker for hostile investigators . 



A complete description of the installation procediires, the rigging, 

 and the equipment involved in the placement of the first STU will be 

 published in a separate report by NCEL. 



Test Sites » The primary considerations in the selection of test 

 sites for the Initial program of deep-ocean testing were to select a 

 site at which circulation, sedimentation, and bottom conditions were 

 more or less "normalo" Just wha.t constitutes a "normal" environment is 

 open to discussion; however, in order to arrive at acceptable sites 

 for these first exploratory experiments, certain practical limitations 

 were established. First, the sites had to be within reasonable operating 

 range of Port Hueneme and converted LCU with which the Laboratory conducts 

 its work; second, the site should not be located in an area of restricted 

 circulation such as a silled basin; third, the bottom should be reasonably 

 flat; and fourth, the site should be located so that use could be made 

 of the best available precision location techniques for positioning the 

 recovery vessel, preferably those techniques using line-of -sight reference 

 points. 



The 6000-foot-depth Site, The site chosen for 6000 feet of 

 water depth is in a broad submarine valley southwest of San Miguel 

 Island. This site is open to the effects of the prevailing coastal 

 ocean currents and is as nearly "normal" a location as there is to be 

 found within a reasonable distance from Port Hueneme » Environmental 

 conditions at the bottom at a depth of 56^7 feet at a site about 5 

 miles northwest of the actual STU placement site were determined to be 

 as follows : 



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