site were an adequate area for assembly of pipeline, the nearness of off- 

 shore sand deposits to the beach, and enough depth (about 30 feet) close 

 to shore to float the dredge and reduce the length of the submerged pipe- 

 line. 



The hopper dredge, Goethals (bin capacity, 5,623 cubic yards), 

 dredged sand from the ocean bottom and transported it to an anchored 

 barge where sand in the bins was pumped out through a submerged 28-inch 

 pipeline onto the beach. (See Figure 6-24.) About 250,000 cubic yards 

 were deposited on 3,800 linear feet of beach. Operations were interrupted 

 by sea conditions and failure of the pipeline connection system. However, 

 total accomplishment of the project was successful, providing information 

 required for improvement of the equipment, and verifying the feasibility 

 of replensihment of beaches by hopper dredges. Figure 6-25 illustrates, 

 with before-and-after photographs, the beach restoration. 



6.323 Redondo Beach (Malaga Cove), California (Fisher, 1969, and U.S. 

 Army Engineer District, Los Angeles, 1970). An authorized beach restora- 

 tion project at Redondo Beach, California, provided another opportunity 

 to use an offshore sand source. (See Figure 6-26.) The availability of 

 sand below the 30-foot contour immediately seaward of the project was in- 

 vestigated in two stages. The first stage, a geophysical survey with an 

 acoustic profiler, indicated that enough sand was available for the pro- 

 ject. In the second stage, core samples were obtained from the ocean 

 bottom using a vibrating core-extraction device. Analysis of the core 

 san5)les verified an underwater sand source of acceptable quantity and 

 quality. This source covered an area 1.4 miles long by 0.5 miles wide 

 about 1,100 feet offshore (shoreward limit). It would produce 2,500,000 

 cubic yards of sand if it could be worked to a depth 52 feet below MLLW 

 between the 30- to 60-foot isobaths. An additional 2,500,000 cubic yards 

 of sand could be recovered by extending the depth of excavation to 60 feet 

 below MLLW. The median diameter of the beach sand was 0.5 millimeter; the 

 median diameter of the offshore sand ranged from 0.4 to 0.7 millimeter. 

 The offshore sand was considered an excellent source of material for beach 

 replenishment. Several land sources were also investigated, and found 

 suitable in quantity and quality. 



Bids, received in August 1967 for land hauling or ocean-bottom re- 

 covery, ranged from $1.07 per cubic yard to more than $2.00 per cubic yard. 

 A contract was awarded to remove the sand from the ocean source. The con- 

 tractor used a modified 16-inch hydraulic dredge, with a water- jet head on 

 the end of a 90-foot ladder. Although the water- jet technique had been 

 used in excavating channels, filling and emptying coffer dams, and pros- 

 pecting for minerals in rivers, its application to dredging in the ocean 

 appears to be unique. Actual dredging began in early December 1967. On 

 17 December, ocean swells rose to a height of 7 feet. With the dredge 

 heading into the swells, the 90-foot ladder and dredge vessel as a unit 

 could not respond to the short-period waves. Water came into the hold 

 shorting out electrical equipment. Air in the fuel and ballast tanks kept 

 the dredge afloat, and it was towed into Redondo Harbor for extensive modi- 

 fications to make it watertight and seaworthy. Ultimately the dredge 



6-32 



