a fairly large lobe of sediment in the northeast corner. In general, the top 

 of the spoil mound was not as flat as it appeared in past surveys, and the 

 entire pile seemed more conical than before. The minimum depth had increased 

 to 15.5 to 16 meters over most of the pile. 



As a result of this survey another change in the position of the disposal 

 point was initiated that moved the site southward. Disposal at this new posi- 

 tion continued until completion of the dredgiing operation in June, 1978. A post 

 disposal survey was then made on August 1, 1978 (Fig. F-6(a-k)) that showed the 

 final mound had a general elliptical shape with a major axis from northwest to 

 southeast. The minimum depth of 16 meters found in the October, 1977 survey has 

 remained stable throughout this period. 



The BOAS system provides excellent precision in surveying and analysis of 

 bathymetric data. This is shown in Figure F-7 where a series of transects are 

 superimposed to evaluate changes in bottom topography. From these data, it Is 

 apparent that no major changes in topography are occurring at the New London 

 site and even minor topographic features can be reproduced over a period of 

 several months. 



Although no major changes in topography have occurred at New London, there 

 is evidence for change in the character of spoils following disposal. A cross- 

 section across the spoil pile that was taken from east to west during the October 

 1977 survey is shown in Figure F-8. This profile was obtained using a Raytheon 

 Dual Frequency Fathometer System that is used in conjunction with the EDO 4034-A. 

 The lower frequency (7 kHz) allows penetration of the sediment for sub-bottom 

 profiling while the higher frequency (200 kHz) provides an accurate measure of 

 the sediment-water interface. 



