Table 17 



Capital Replacement/Overhaul Costs for Alternative 2: Semifixed Plant 



Item 



Interval 

 (years) 



Present Cost 1 

 (S) 



Annual Cost 2 

 (S) 



Crawler crane 

 (incl components) 



6 to 10 



27.4K 



2.3K 



Diesel engines for booster pumps 

 (two pumps) 



20 



9.5K 



0.8K 



Booster pumps components 

 (two pumps) 



2-4 



108.0K 



9.0K 



Diesel engine for supply pump 



16 



5.0K 



0.4K 



Supply pump components 



4-10 



6.1 K 



0.5K 



Air compressor & components 



10-15 



1.2K 



0.1K 



Gauges 



5-10 



4.9K 



0.4K 



Flow instrumentation 



10 



8.1 K 



0.7K 



Crane-mounted density meter 



15 



0.7K 



0.06K 



%-ton 4WD Diesel pickup 



6 



29.5K 



2.5K 



Slurry gate valve 



6 



1.8K 



0.2K 



All other gate valves 



10 



2.6K 



0.2K 



Jet pump & components 



2-8 



58.5K 



4.9K 



Pipeline & components 



4-12 



98.5K 



8.2K 



Pump house 



20 



1.4K 



0.1K 



Annual cost of capital replacement 



30.4K 



' Present cost (time value of money) of the periodic replacement/overhaul costs. 

 2 Assumes an interest rate of 7-3/8 percent and 30-year return period. 



Alternative 3: Land-based Mobile Plant (Crawlcat/Crawldog) 



The third alternative considered is a land-based mobile dredge called Crawlcat or Crawldog. 

 The Crawlcat is marketed by IHC Holland and consists of a floating pontoon with 

 four legs on tracked wheels, which allows it to maneuver along the bottom in depths up to 10 m. 

 Similar to a cutterhead dredge, the Crawlcat has a ladder with a dredgehead that pivots from side 

 to side, and dredged material is discharged through a pipeline (Figure 24.) The Crawlcat has a 

 narrow width because it was originally designed for use in canals with little or no wave activity. 

 Though this design scheme has been used in an open coast environment, IHC Holland 

 recommends against using the existing Crawlcat in such a manner. 1 Instead, a specialized 



Personal communication, Mr. Ruud Ouwerkerk, Dredge Technology Corporation, Wayne, NJ, 1996. 

 62 Chapter 5 Other Bypassing Studies 



