The most promising deposit crops out in Thimble Shoals Channel and 

 along a reentrant in the south flank of Tail of the Horseshoe. This 

 deposit is a coarse brown to reddish brown sand and gravelly sand 

 (Unit E) . Data suggest that the deposit extends to and through the Tail 

 of the Horseshoe shoal to near the south wall of Chesapeake Channel 

 where it decreases to a thin layer. It does not appear to extend north- 

 ward into the deeper part of Chesapeake Channel. South of the Thimble 

 Shoals outcrop area, the coarse sand body appears to extend under Lynn- 

 haven Roads, but is deeply buried under a silt and silty clay layer. 

 Figure 16 shows the approximate configuration, extent and thickness of 

 Type E sand and gravelly sand in the Thimble Shoals deposit which appears 

 economically recoverable. Within the outlined area, about 3,500,000 

 square yards of Type E material is exposed, and the volume available in 

 this area is calculated to be 11.9 x 106 cubic yards. In addition, about 

 7.5 x 10" cubic yards are estimated to be available in the area bordering 

 the exposure with a removal of no more than 5 feet of overburden. 



In terms of mechanical stability, the Thimble Shoals material is 

 considered good. Most of the sand grains are quartz which is resistant 

 to mechanical and chemical degradation. Some gravel particles are com- 

 posed of granitic rock which is partly decomposed. These fragments con- 

 stitute only a minor fraction of the sediment. 



Layers and lenses of well-sorted, clean sand closely matching the 

 beach sand occur in the Thimble Shoals deposit. However, the split 

 cores showed that these layers are generally bedded with interspaced 

 coarse sand mixed with gravel and occasional thin clay partings. The 

 material finer than the native sand will be removed from the beach soon 

 after placement, and the coarser particles will tend to remain. 



Another possible source of suitable beach fill is the coarse brown 

 surficial sands in the area covered by Cores 10, 15, 21 and 39. Assuming 

 the deposits occur in isolated patches of the approximate extent shown 

 in Figure 9 and average thickness is 3 feet, then about 1.9 x 10^ cubic 

 yards of this material would be available. Since data are limited con- 

 cerning deposits in this area, more detailed study including field data 

 collection would be required to more accurately assess the magnitude of 

 suitable borrow material. 



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