Mooring Requirements to Encircle a Ship and to Contain 

 an Oil Spill in the Middle of a Harbor 



The mooring requirements to encircle a ship will depend upon the type 

 of pier at which the ship is berthed. If the pier is open, i.e., water 

 can go under the pier to the other side, then the mooring requirements 

 will be more extensive. 



During these tests, the ship available for tests was tied to a 

 "closed" pier (defined as one which has a vertical barrier in the water 

 along the length of the pier) . In this situation, all that was necessary 

 was to tie one end of the boom to a specific piling at or close to the 

 vertical wall to ensure that oil would not escape at this end, then 

 proceed to deploy the boom such that it surrounded the oil and the ship 

 completely. Figure 28. Two mooring systems were deployed at about the 

 same time using the FTB so that the boom could be secured at desired 

 locations . The other end of the boom was connected to a suitably selected 

 piling at the other end of the ship. The boom was therefore secured at 

 four points: two pilings and two mooring systems. 



To encircle a ship completely and to contain a spill in an open area 

 away from all structures, a minimum of four mooring systems are felt to 

 be necessary. Two additional small mooring systems available for tests 

 were, therefore, used for this test. The boom, moored by the four mooring 

 systems, assumed a nearly circular shape, as shown in Figure 29. Several 

 observations made during these tests and recommendations developed are 

 given later in this chapter. 



Holding Capacity of Anchors 



Due to limited access to a soft clay seafloor, the anchors were 

 tested only in sand. Capacities of the anchors in other types of seafloors 

 may be inferred from the results of the tests in sand. 



The holding capacities of the 16-lb, 40-lb, and 60-lb anchors in 

 sand were calculated from their holding capacities determined by 

 dragging each anchor slowly on the sandy beach at Port Hueneme by a 

 Caterpillar bulldozer. Figure 30. This is recognized to be a better 

 procedure for obtaining reliable, reproducible data on the anchors than 

 conducting these measurements in the harbor. The standard procedure 

 used in these tests is described in detail in reference 11. 



During the test, once the anchor behan to move through the beach 

 sand, the maximum pull exerted by it upon the line was measured by a 

 dynamometer. Each anchor was pulled over a distance of approximately 

 50 ft. The 16-lb and the 40-lb anchors indicated maximum holding 

 capacities of 2,850 + 50 lb and 7,550 +50 lb, respectively. The 60-lb 

 anchor broke off at 10,000 j^ 50 lb. The fluke was found broken from 

 the crown . 



For a particular type of soil , the holding power of a Danf orth 

 anchor in a harbor is about 34 percent lower than its holding power on 



28 



