deployment tape, an interval of 3.75 min (eight tide measurements/hour) was 



selected. 



Mounting 



11. The instrument housing is a 6-in.-diam. by 30-in.-long aluminum 

 pressure case containing the transducer, electronics, data logger, and battery 

 pack. The case was attached with stainless steel bolts to a vertical mount 

 that was welded to a 600-lb railroad wheel. Gages inside the harbor had a 

 subsurface retrieval buoy attached to the mount and an acoustic beacon for 

 relocation by divers. Because of the depth outside the harbor, a subsurface 

 buoy was attached to the wheel with a length of retrieval line coiled in a 

 canister. The canister, in turn, was attached to the wheel with a trans- 

 ponder/acoustic release. The release served the dual purposes of a beacon, 

 for locating the instrument package, and as a means of releasing the buoy and 

 recovery line at the end of the deployment. Figure 3 shows a typical assembly 

 in the deployed configuration. 



Deployment /recovery 



12. A temporary field office was leased on Terminal Island with adja- 

 cent dock space. This provided office and testing space, secure outdoor stor- 

 age of heavy equipment and vessels, and a staging/loading area for operations. 



13. All tide gages and in situ current meters were deployed from the 

 University of Southern California research vessel "Sea Watch" through the co- 

 operation of the USC Marine Science Laboratory on Terminal Island. An experi- 

 enced crew, aided by the stern-mounted A-frame and ample work deck, installed 

 the primary gages on 10 June and the backup gages on 3 August by lowering the 

 mounts using the lift bail (Figure 4) . 



14. Positions were established with LORAN, radar bearings, and visual 

 bearings to prominent targets on shore. 



15. The planned recovery technique was to trigger the acoustic release, 

 allowing the buoy to surface and enable retrieval from the surface without 

 diver assistance. In the event of transponder failure, the gage positions 

 could be relocated within -100 ft, at which point a sweep would be made from 

 the surface by dragging a chain between two vessels. Divers would then 

 recover the gage by descending the sweep chain. 



10 



