6 Other Bypassing Studies 



A survey report by the USAE District, New York (1958) discusses improvements (dredging, 

 jetty modifications, etc.) to Moriches and Shinnecock Inlets. This report also includes a 

 preliminary plan for bypassing at both inlets. The proposed plan (specific for Moriches, but 

 general for Shinnecock) is a fixed plant constructed with a pier extending seaward from the end 

 of the east jetty to interrupt sand as it travels westward. The sand would then be pumped via a 

 10-in. discharge line under the inlet to a distance 450 m west of the west jetty. The plant would 

 be capable of pumping 85 percent of the total 229,000 m 3 (300,000 yd 3 ) littoral drift but would 

 only actually need to pump 96,000 m 3 (125,000 yd 3 )— that amount not being bypassed naturally. 



For development of a cost estimate for bypassing, USAE District, New York (1958) planned 

 for 16-hr days 200 days of the year. Estimated first costs were $738,000 and annual costs were 

 $155,700 (1957 dollars). Interestingly, converting these figures to 1997 dollars gives costs very 

 similar to those generated for the semifixed analysis in the present study. 



USAE District, New York (1958) also suggested that bypassing could be accomplished with 

 a shallow-draft hopper dredge. Though no such dredge yet existed, NAN had tentative plans to 

 construct a dredge with hopper capacity of approximately 230 m 3 (300 yd 3 ) and loaded draft of 

 1.8 m that could place material in the nearshore. Because this dredge was not yet built, no cost 

 estimates were available. 



PRC Engineering (1986) conducted a bypassing study at Shinnecock Inlet that evaluated 

 seven alternatives, including three types of fixed dredge pump/jetpump systems, two semi- 

 mobile systems, and two hydraulic dredging techniques. Unfortunately, PRC Engineering did 

 not have the benefit of an updated, detailed coastal processes study for their analysis, so 

 recommendations are based on a range of possible bypassing rates (between 45,900 mVyear 

 (60,000 yd 3 /year) and 191,000 m 3 /year (250,000 yd 3 /year)). PRC Engineering also examined 

 only the channel and updrift fillet as sources of sand and did not consider new technologies 

 (which may not have existed in the 1980s). 



PRC Engineering did recognize the need for placing the bypassed sand sufficiently downdrift 

 to ensure restoration of regional transport. Their discharge location was approximately 1 ,600 m 

 west of the inlet. But without accurate ebb shoal location data as exists for the current study, this 



Chapter 6 Other Bypassing Studies 79 



