134. Vessels used for geophysical surveys require sufficient covered 

 space to accommodate the power supply recorders, signal processors, and navi- 

 gation control equipment that could be damaged by spray or rain. Although 

 geophysical surveys are carried out at relatively low rates of speed, the 

 survey vessel should be capable of a higher rate of speed for moving between 

 the dock and current survey area, thus maximizing time for active operations. 



135. Vessels commonly used for coring, such as barge and tug combina- 

 tions, usually have relatively slow cruising speeds. Since most of the time 

 spent in coring operations is consumed by traveling between core sites, core 

 production is proportional to the speed of the coring vessel; thus, relatively 

 high speeds are desirable. Although not a necessity, a reconnaissance boat 

 equipped with the offshore navigation station can be used to locate and mark 

 selected core sites, which eliminates need for the slower and less maneuver- 

 able coring platform boat to locate the site. 



Cost Estimate 



136. An example of a cost estimate for a borrow source exploration pro- 

 gram from Prins (1980) is contained in Appendix B. In order to draw up such 

 an estimate, the following factors must be determined: 



a. Plant rental costs for equipment and vessels per day. 



b. Personnel costs per day. 



c. Overall costs for travel, expendable supplies, and equipment 

 preparation. 



d. Expected average miles of geophysical survey per day. 



e. Expected average number of cores collected per day. 



f . Expected downtime due to weather or equipment malfunction. 



The example does not program time for collecting additional trackline miles 

 that may be added as a result of the day-to-day data review. Experience in 

 the ICONS program suggests that this figure should be 15 to 20 percent of the 

 preplanned geophysical trackline miles and cores. 



137. Factors a, b, and c in the above list can usually be determined 

 precisely from readily available sources such as pay scales and travel fee 

 schedules. Factor d is usually limited by the practical towing speed of the 

 seismic reflection system source and receiver elements. With surface-towed 

 units this is about 4 knots. Using a 10-hr working day, about 40 nautical 



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