59. 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. 



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

 a 10. 7 -m- tall amphibious tripod, and a Zeiss electronic surveying system 

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

 each figure in Appendix A. Survey accuracy was about +3 cm horizontally and 

 vertically. Monthly soundings along both sides of the FRF pier were collected 

 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. 



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

 in Figure 23 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. 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

 Month 



Figure 23. Time-history of bottom elevations at 

 selected locations under the FRF pier 



49 



