27 



Table 4-1 



Summary of Volume Difference Calculations for the 

 New Haven Capping Project, September 1993 to March 1994 



m 3 



m 



Baseline/Interim Disposal 

 Interim Disposal/Precap 



TOTAL DREDGED MATERIAL 



238,000 

 74,000 



312,000 



Precap/Interim Cap 

 Interim Cap/Postcap 

 TOTAL CAP 



124,000 

 278,000 



402,000 



TOTAL VOLUME 



714,000 



4.1.3 Precap Survey (2-3 November 1993) 



This survey measured the NHAV 93 mound following the completion of the federal 

 inner harbor dredging and UDM deposition, as well as the disposal of 76,000 m 3 of cap 

 material at the northwest capping locations. Disposal of UDM from the private dredging 

 operations continued over the southwestern flank of the disposal mound. (Figure 2-2, point 

 I). The analysis of bathymetric data from the precap survey (Figure 4-3) indicated a loss 

 in mound height (0.5 m) from the interim disposal survey (Figure 4-1). An interesting 

 result of the bathymetric comparison is evidence of a large amount of consolidation or 

 slumping of the dredged material. The depth difference contours between the interim 

 disposal and precap survey (Figure 4-4) show the loss at the mound peak due to structural 

 failure of the apex. The profile plot comparing survey lane 35 from the interim and the 

 precap survey (Figure 4-5) is included to show the evidence of slumping of the mound 

 peak and the movement of material towards the northeast. Results of the depth difference 

 between the baseline and precap operations (Figure 4-6) show the size of the mound to be 

 approximately 510 m in diameter and 2.5 m in height. The calculated total volume of the 

 mound based on the baseline and precap bathymetric surveys is 312,000 m 3 . The volume 

 shown by the depth difference model between the interim disposal survey and the precap 

 survey is 74,000 m 3 . 



Monitoring Surveys of the New Haven Capping Project, 1993-1994 



