throughout the borrow area but the sediments probably become progressively 

 finer seaward from core 15. Core 14 at the seaward boundary of the area 

 contains 2 meters of sand but it is just within the authorized dredged- 

 material disposal area and it is probably a unique occurrence, since most 

 of the dredged material dumped there is fine grained in nature. The 

 estimated volume of sandy sediment in area C is 20.6 million cubic meters 

 (27 million cubic yards) using a thickness of 1 meter in the high priority 

 area and 0.5 meter (1.6 feet) in the offshore region (Table 2). 



Several cores on the Galveston shelf between area C and San Luis Pass 

 contain sandy material worthy of textural analysis (App. A), but the sand 

 layers are generally thin and the seismic data suggest that lateral con- 

 tinuity of the sand is lacking. 



c. San Luis Pass . Borrow area D is a high potential area (Fig. 18); 

 it contains the best quality sand as well as the largest estimated avail- 

 able volume for the entire study area. The area comprises the modern ebb 

 tidal shoal (Fig. 19) of San Luis Pass and adjacent parts of the lower 

 shoreface. Cores 26 and 27 contain fine to medium sand with small amounts 

 of finer sediments. There is a possibility that the deposit in core 25 is 

 correlative with that in core 23, 5 kilometers (3 miles) to the east. If 

 this is correct, borrow area D would be considerably larger than shown. 

 Additional cores are necessary to fully evaluate this possibility. An 

 analysis of 16 borings taken at locations across San Luis Inlet as shown 

 in Figure 20, as well as the offshore seismic profiles, shows that the 

 stratigraphy in the region consists of generally sandy Holocene sediments 

 overlying the Pleistocene unconformity at about -10 meters (-33 feet) 

 which is considered the depth limit for dredging. Figure 20 also shows 

 sandy sediments about 9 meters thick (borings 4 to 8) on the shoal east 



of the inlet channel and inshore of area D. The estimated volume of sand 

 in area D using a 2-meter thickness, is 23.2 million cubic meters (30.3 

 million cubic yards) (Table 2) . It could be considerably larger if more 

 shoal area were included for the entire lO-meter thickness. As shown in 

 Figure 18, the recommended area extends from water depths of only 1.5 

 to 9.1 meters (5 to 30 feet). This is an exception to the usual recom- 

 mendation that no sand be dredged in water shallower than 5.5 meters. 

 Walton and Dean (1976) suggest that inlet shoals, such as the one at San 

 Luis Pass, may be excellent sources of fill sand, and that removal of the 

 sand may not be detrimental to adjacent coastal areas. They show that 

 such shoals refract incident waves, making adjacent shores more vulnerable 

 to erosion than if the inlet and offshore shoals were not present. Walton 

 and Dean suggest that removal of fill sand from the shoals may indirectly 

 reduce erosion on adjacent coasts by making the wave refraction patterns 

 more uniform along the coast. In 1975, sand in water depths of 2 meters, 

 dredged from the ebb tidal shoal at Fripp Inlet, was successfully used 

 for beach fill at Hunting Island, South Carolina. No negative effects on 

 the adjacent coast have been reported (Hobson, in preparation, 1979). 



d. San Luis Pass to Freeport Inlet . Of the seven cores taken in this 

 area, only core 34 (Fig. 21) contains enough sand to warrant designating 

 the site (off Surfside Beach) a possible borrow area (area E) . The sand 



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