and 3 years (100,000 m 3 , 200,000 m\ and 300,000 m 3 , respectively), including different 

 placement options (onshore versus nearshore). 



According to Great Lakes Dredge & Dock (1996), mob/demob costs for a hopper dredge 

 operating at Shinnecock Inlet with an approximate 4.8 km (3-mile) sail distance to Tiana Beach 

 would be between $500,000 and $750,000. Estimated unit costs for dredging and placing 

 material vary between $6.2 1/m 3 ($4.75/yd 3 ) for beach placement using a pump-out buoy and 

 $3.92/m 3 ($3.00/yd 3 ) for nearshore placement. Including contingencies of 10 percent increases 

 the cost to $6.83/m 3 and $4.3 1/m 3 ($5.23/yd 3 and $3.30/yd 3 ), respectively. Additional increases 

 for engineering and design (E&D at 15 percent) and supervision and administration (S&A at 10 

 percent) give final unit costs of $8.54/m 3 and $5.39/m 3 ($6.54/yd 3 and $4.13/yd 3 ), respectively. 

 Estimated costs are summarized in Table 14. 



Table 14 



Cost Summary for Alternative 1 : Floating Plant 



Cycle/ 

 Placement 



Quantity 

 m 3 (yd 3 ) 



Mob/Demob 1 

 ($) 



Dredge/Place 



S/m 3 (S/yd 3 ) 



Annual Cost 2 

 ($) 



Annual Unit Cost 3 

 S/m 3 ($/yd 3 ) 



1 Year 



Nearshore 



100,000 

 (131,000) 



500 K 



5.39 



(4.13) 



1 .039 M 



10.39 

 (7.93) 



Onshore 



100,000 

 (131,000) 



500 K 



8.54 



(6.54) 



1.354 M 



13.54 

 (10.34) 



2 Years 



Nearshore 



200,000 

 (262,000) 



750 K 



5.39 

 (4-13) 



866 K 



8.66 



(6.61) 



Onshore 



200,000 

 (262,000) 



750 K 



5.39 

 (6.54) 



1.165 M 



11.65 

 (8.89) 



3 Years 



Nearshore 



300,000 

 (393,000) 



750 K 



5.39 



(4.13) 



712 K 



7.12 

 (5.44) 



Onshore 



300,000 

 (393,000) 



750 K 



8.54 

 (6.54) 



996 K 



9.96 

 (7.60) 



' Mob/Demob and unit costs provided by Great Lakes Dredge and Dock, Chicago, IL. Mob/Demob costs 

 less for 1-year cycle based on assumption of on-site storage of some equipment to lower mobilization. 



2 Annual costs are calculated using the project cost amortized over the project cycle using 7-3/8 percent 

 interest rate (as recommended by NAN) (see Appendix E). 



3 Annual cost divided by 100,000 m 3 (for 131,000 yd 3 ). 



Alternative 2: Semifixed Plant 



The Indian River Inlet Bypass Plant is used as a reference for the second alternative. At 

 Indian River Inlet, a crawler crane positions a jet pump on the updrift fillet near mlw. The jet 



56 



Chapter 5 Other Bypassing Studies 



