sediment movement was very slow and possibly no significant movement 

 occurred. However, the paucity of data does not provide any real basis 

 for determining whether sand does or does not move around Point Concep- 

 tion. Knowledge to that effect, and the manner in which it occurs, if 

 it does indeed occur, must wait for subsequent programs. Intangible 

 success accrued through additional knowledge of operating characteristics 

 of the equipment in the oceanographic and coastal environment? as well as 

 basic information which can be incorporated in future field tests. 



Not enough data points are available to more precisely define dis- 

 persal patterns. Any of four factors may have caused or contributed to 



this difficulty: 



1. rapid dispersion and dilution of the radioactive sand beyond 

 the limits of detection (l microcurie over 1 square foot); 



2. failure to disperse or very slow rate of tagged - sand dispersion; 



3. burial of the tagged sand; or 



k. too widely spaced tracking, in terms of the rate of movement 

 and volume of sand, especially if the sand remained in a 

 small area . 



Field procedures are designed so that monitoring begins nearly 

 simultaneously with injection to guard against "losing" the sand as a 

 result of rapid dispersion. Experience at Cape Kennedy and at Surf 

 indicates the procedure is sound. Scuba divers, in the water at the 

 time of each injection, observed a bottom surge associated with wave 

 passage. By means of dye releases on the bottom, a unidirectional cur- 

 rent of approximately 15 cm/sec (0.5 ft/sec) was measured at each location 

 of dye placement; too rapid dispersion of the labeled sand is therefore 

 unlikely. Although it appears unlikely, there is a possibility that 

 labeled sand was gradually removed from the point source and was_ con- 

 sequently diluted beyond the level of detectability. Computations of 

 the supposed rate of sediment motion are imprecise and subject to wide 

 latitude of values. Therefore, while data in Table III indicate the 

 sand should move, it is conceivable that actual conditions on the sea 

 floor precluded movement or that movement was relatively slow. Burial 

 by unlabeled sand could mask the presence of labeled sand. The limiting 

 depth of burial for detecting xenonated sand is approximately 6 centi- 

 meters. Divers reported ripple marks on the bottom in the three study 

 sites; amplitudes in excess of 1.0 centimeter were only infrequently 

 noted. The wave lengths of the ripples were such that all labeled sand . 

 would not be buried. Oceanic conditions indicated that a blanket burial 

 was not probable. If the rate of dispersal was low, it is quite possible 

 that the search tracks were too widely spaced. On-board plotting of the 

 vessel track was done to preclude such a possibility, but proved to be a 

 relatively imprecise technique. It is judged that the paucity of sig- 

 nificant (twice background) radiation data is due to a combination of 

 relatively slow movement of tagged sand and the wide track spacing. 



66 



