(2) Identical to basin test step (2). 



(3) Identical to basin test step (3). 



(4) The test flow condition was initiated and allowed to 

 establish for 2.5 min. 



(5) The trap was placed in the tank after an elapsed time of 

 2.5 min, and sand was collected for 5.0 min. Midflow and 

 bottom flow speeds at Point A (Figure 21) were recorded during 

 the test. The bottom nozzle's streamer bag was "swished" 

 slightly back and forth in the flow during the testing period 

 to eliminate settling of large slugs of sand which tended to 

 settle near the nozzle entrance and reduce the area of the 

 nozzle opening. Clogging of the streamer bags was an artifact 

 of the laboratory flow environment . In the surf zone wave 

 action clears streamer bags during typical field conditions. 



(6) After a test was completed, collected sand was removed from 

 the streamers, weighed in a drip-free state, and recorded. 

 Selected samples were retained for laboratory analysis and 

 comparison with the remaining bed material and the sand 

 collected in the basin. 



75. Steps a(l) through a(6) were then repeated for a 7. 5 -min test for 



the same flow condition, except that the longer testing period enabled both 



midflow and bottom flow speeds to be recorded in step a(5). The quantity of 



material collected during the 2. 5 -min run was subtracted from that collected 



during a 7.5-min run, with the same midflow speed, and divided by the elapsed 



time (5.0 min) and test section width (of the sand-filled area) to obtain an 



"equilibrium flow" basin transport rate for the 5-min run. 



Sand-Trapping Efficiency Tests 



76. One hundred and one nozzle and basin sand-trapping efficiency tests 

 were conducted over a period of 40 lab days. Quantities of material collected 

 in the basins and by each type of nozzle at each elevation in the flow are 

 tabulated in Appendix D. Qualitative observations of nozzle performance 

 during testing were conducted. The DUCK85 bottom nozzle began scouring around 

 its outer edges immediately after testing began, and the scour increased 



52 



