The submerged portion of the facility consists of four dual tracking 

 hydrophones, a string of three noise-measurement hydrophones, and a UQC. 

 The tracking and communication hydrophones are supported on 1 5-foot -tall 

 by 12-foot-diameter aluminum conical frames each weighing 385 pounds in 

 water ( Figures 7 and 1 1 , respectively) . The noise-measurement string includes 

 three hydrophones attached to a buoyed cable. All sea cables are connected 

 to an underwater termination chamber in approximately 60 feet of water, 

 1/2 mile offshore. The 6-foot-diameter by 1 2-foot-tall cylinder is supported 

 on a sandy bottom by four legs. Ballast is used to overcome the 1 5,000 pounds 

 of positive buoyancy developed by the chamber. 



Slight reception problems at one of the four hydrophone structures 

 led to the performance of an inspection of the entire range by the General 

 Motors submersible, DOWB (Deep Ocean Work Boat), in late 1968 and early 

 1969 (Engstrom, 1969). As a result of this inspection it was discovered that 

 several structures were lying on their sides. This was determined not to have 

 been the result of soil-related problems. 



The structures were righted during the summer of 1 969 using the 

 DOWB (Figure 12). Output from the tracking hydrophones indicates that 

 the foundations have performed satisfactorily since that time. 



It is interesting to note that for all but one of the structures there 

 was no obvious indication of improper orientation of the structures. The 

 range inspection and subsequent remedial actions resulted in an overall 

 improvement of the range effectiveness. 



Sandia Facility. In 1 965, an acoustic range was installed adjacent to 

 SCARF for the Sandia Corporation by the owner and operators of SCARF 

 (Engstrom, 1 969) . The six hydrophones are located in approximately 2,400 

 feet of water (Figure 9). Other physical and mechanical characteristics of the 

 system are similar to those at SCARF. A common underwater cable-termination 

 chamber is used by the two ranges. No foundation problems have been reported. 



Saint Croix Range. The Applied Physics Laboratory (APL) at the 

 University of Washington designed and installed for the Navy an underwater 

 tracking range off the west coast of Saint Croix in the Virgin Islands (Garrison, 

 1963; Rooney, Eppert, Huddel, 1965; Linger, 1969). Four hydrophone struc- 

 tures were emplaced in 1 964 at a water depth of approximately 3,000 feet. 

 The range was enlarged to 1 1 hydrophone structures in 1 967. 



Sediment investigations were made at the site in 1962 and 1965 by 

 NAVOCEANO and in 1 963 by APL. Typical sediment properties as deter- 

 mined by NAVOCEANO were as follows: 



20 



