57. To document the temporal and spatial variability in bathymetry, 

 surveys were conducted approximately monthly of an area extending 600 m north 

 and south of the pier and approximately 950 m offshore. Contour maps result- 

 ing from these surveys along with plots of change in elevation between surveys 

 are given in Appendix A. 



58. All surveys utilized the Coastal Research Amphibious Buggy (CRAB), 

 a 10.7-m-tall amphibious tripod, and a Zeiss Elta-2 electronic surveying sys- 

 tem described by Birkemeier and Mason (1984). The profile locations are shown 

 on each figure in Appendix A. Survey accuracy was about ±3 cm horizontally 

 and vertically. Monthly soundings along both sides of the FRF pier were col- 

 lected by lowering a weighted measuring tape to the bottom and recording the 

 distance below the pier deck. Soundings were taken midway between the pier 

 pilings to minimize errors caused by scour near the pilings. 



59. A history of bottom elevations below Gages 645 and 625 is presented 

 in Figure 37 for their respective pier stations of sta 7+80 (238 m) and 



sta 19+00 (579 m) along with intermediate locations, 323 and 433 m. 



DISTANCE 



(m) 

 238 



Q_ 

 Ld 

 Q 



323 

 433 



579 



i 1 1 r 



S N D 



MONTH 



Figure 37. Time-history of bottom elevations at 

 selected locations under the FRF pier 



68 



