Although seismic data and sediment samples were not collected from 

 each of the borrow areas identified in Figure 40, all are presumed to be 

 suitable for sand borrow, based on the characteristics of those surveyed. 

 The estimated volumes of sand in each shoal are as shown in Table 9. 

 Calculations of volume. were made as follows: 



V 4 h(A +4A l +A 2 ] 



where 



V = volume (in cubic yards) 



h = height, thickness of the deposit (in yards) 



A Q = surface area of the top (in square yards) 



A 1 = surface area of the midsection, taken at 1/2 h (in square 

 yards) 



A 2 = surface area of the base of the deposit (in square yards) 



Area measurements were made with an engineering planimeter from a 

 1:80,000 scale chart. The top of the deposit was taken as the shoalest 

 closed contour and is given in Table 9. The base of the deposit was 

 taken as the deepest enclosing contour; in cases where the deepest con- 

 tour paralleled the shoal only part way, it was extrapolated the remainder 

 of the way. Shoreface shoals were measured by truncating contours at the 

 base of the shoal where it merges with the shoreface. 



It is estimated that approximately 2.2 billion cubic yards of sand 

 suitable for use in beach restoration is present in 39 separate shoal 

 borrow sites on the inner shelf off northern Delmarva (Table 9) . This 

 figure represents a minimum value since no effort was made to assess the 

 volumes of sand in nonshoaled sea floor areas. 



Not all of the shoals designated as potential borrow sites were 

 sampled, as indicated in Table 9. Size characteristics of samples from 

 shoal areas are given in Figures 41 and 42 and in Appendix B. If sand 

 volumes are tabulated only for those shoals that were sampled, there is 

 more than 765 million cubic meters (1 billion cubic yards) of suitable 

 material. This is over an order of magnitude greater than the amount 

 required for construction and 50 years of maintenance for the entire 

 Maryland seashore. 



c. Vertical Textural Patterns of Shoals . The mean grain size of 

 core samples, determined by sieve analysis and settling-tube analysis 

 (and corrected to sieve equivalents) were grouped by individual linear 

 shoals (Fig. 41) and by shoreface and shoreface shoals (Fig. 42) to 

 observe vertical-size trends. Both sets of data generally show an abrupt 

 decrease in size of cored sands from 0.03 meter (-1 foot) up to the core 



98 



