5 Bypassing Alternatives 



Various alternatives exist for bypassing sand around Shinnecock Inlet. Of the general 

 descriptions discussed previously, three will be expanded, and a new and old technology will also 

 be discussed. 



Alternative 1: Floating Plant 



The first alternative is the floating plant (dredge), which is the most traditional method of 

 bypassing because of its use in maintenance dredging and availability on contract (as opposed to 

 capital outlay needed to purchase fixed equipment). This alternative analysis only considers a 

 trailing suction hopper dredge, though other floating plants may be feasible. The hopper dredge 

 is more maneuverable than other dredges and can more easily operate in an open ocean 

 environment. A trailing suction hopper dredge can also efficiently remove thin layers of sand 

 over large areas, which is a desired characteristic for using the updrift fillet, ebb shoal, and flood 

 shoal as sources of sand. By using all three areas, the impact of bypassing 100,000 mVyear 

 (131,000 ydVyear) (or 200,000 (262,000 yd 3 ) or 300,000 m 3 (393,000 yd 3 ) on a 2- to 3-year 

 cycle) on any one source location will be minimized. For example, the dredge could remove a 

 portion of the required volume from each of the areas (offshore areas of the fillet, seaward slope 

 of the ebb shoal, and remote locations of the flood shoal) such that sediment removal will be less 

 likely to adversely affect local transport rates and inlet hydraulics. Figure 22 is a plan-view of 

 potential dredging (flood shoal borrow area not shown due to lack of data to characterize flood 

 shoal) and placement locations. 



As was mentioned previously, performing bypassing during longer dredging cycles (2 to 

 3 years as opposed to every year) may help to keep total costs down by spreading the mob/demob 

 costs over several years. However, with proper planning and contracting, an annual dredging 

 cycle may be able to reduce remob/demob costs by storing equipment and pipes in the vicinity 

 (Great Lakes Dredge & Dock 1996). 1 Cost estimates are presented for dredging cycles of 1, 2, 



Personal communication with Mr. Bill Murchison of Great Lakes Dredge & Dock, Chicago, IL. 

 Chapters Bypassing Alternatives 55 



