Entrainment can be accelerated by either of two separate events or a combina- 

 tion of external inputs. One event is the increase of water current velocity. 

 This event has a tendency to push the skirt off the vertical and to decrease 

 the amount of entrained oil (Figure 3). The second event is high winds, which 

 can cause a similar loss of vertical integrity, if sufficient freeboard is 

 present, by pushing the top of the boom toward the water surface. Sometimes, 

 the boom may actually lie flat on the water with a subsequent loss of previously 

 contained oil (Figure 4). 



<r 



WIND 



Figure 3. Entrainment increased due to fast current. 



WIND 



-> 



Figure 4. Entrainment increased due to high wind with normal current. 



The problems associated with entrainment can be partially countered by decreasing 

 the angle of the boom to the bank. Problems associated with the effect of 

 wind on boom integrity are completely situational and require individual analysis 

 and deployment of "trade-offs" to maximize containment of the spilled product. 



72 



