ideal for equipment maintenance and repairs). Therefore, any channel maintenance conducted 

 after implementing a fixed bypass option should be considered as providing an extra source of 

 sand and be used accordingly in areas of greater need or as a supplement to the bypass system. 



For the current study, to compare the bypassing alternatives discussed previously, an 

 alternative selection decision matrix was developed. This matrix (Table 23) evaluates each of 

 the five alternatives based on several criteria. Each alternative is assigned a numerical grade 1 to 

 5(1= most positive and 5 = least positive) for each of the criteria. These factors are then 

 summed and normalized by multiplying by the unit cost of the alternative to give the final rating. 

 Some assumptions inherent in this decision matrix are (a) all criteria are considered of equal 

 weight, and (b) the grades (1-5) given to each criteria are subjective. 



Criteria descriptions are as follows: 



a. Alternative experience—amount of experience in the United States with this particular 

 technology. Techniques like the Crawldog and Punaise are given higher grades because 

 of their experimental nature and lack of experience. Floating plant is graded lower (more 

 positive) because of the extensive experience with dredging in the United States. 



b. Navigation impact— relative impact to ongoing navigation activities. Floating plants may 

 have a higher grade, but because of the recommendation to use hopper 



dredges, which have a greater mobility, navigation impact is reduced. Semifixed, 

 Crawldog, and mechanical fillet mining have minimal impacts to navigation because no 

 equipment is in the channel. Punaise may have a slightly greater impact to navigation 

 during repositioning, but because it resides on the bottom, impacts should be minor. 



c. Environmental impact— relative impact to beach and underwater habitat for both sand 

 removal and discharge/placement. Floating plant is graded lower because of the lack of 

 permanent facilities on the beach, booster pump stations, and pipeline installations. 



d. Aesthetics— the interference (or lack thereof) of visibility on/to the surrounding beach and 

 ocean. Floating plant and Punaise are graded lower because of their transitory nature and 

 lack of permanent facilities. 



e. Sand source flexibility— flexibility of the alternative to remove sand from more than one 

 location to minimize impacts of overuse. Floating plant and Punaise graded lower 

 because of their mobility and potential to use the ebb shoal, flood shoal and/or updrift 

 fillet. The Punaise may, however, be further limited by the thickness of the sand layer, as 

 previously discussed. Semi-fixed, Crawldog, and mechanical fillet mining are all tied to 

 the updrift fillet and thus graded higher. 



82 Chapter 7 Conclusions 



