EXECUTIVE SUMMARY (continued) 



Comparisons between the baseline, interim disposal, and precap monitoring surveys 

 revealed a UDM deposit 510 m in diameter and 2.5 m in height, containing a volume of 

 312,000 m 3 of new material. A significant amount of consolidation was detected over the 

 apex of the disposal mound before capping operations commenced. The NHAV 93 mound 

 was then capped to a thickness of 0.5 to 1.0 m with CDM from the outer harbor, resulting in 

 a total mound diameter of 600-800 m and height of 2.5 m at the apex. Volume difference 

 calculations based on the baseline, precap, interim cap, and postcap surveys detected 

 402,000 m 3 of cap material overlying the initial UDM deposit and a total mound volume of 

 714,000 m 3 . 



Although 402,000 m 3 of CDM was placed over the initial UDM mound, there was no 

 increase in net mound height at the apex. It has been determined through precision 

 bathymetric surveying and geotechnical coring that consolidation of the UDM deposit and 

 compaction of the basement sediments had occurred during the middle stages of CAD mound 

 construction. As a result, no apparent changes in mound height were detected after the 

 completion of capping operations over the NHAV 93 mound. 



Monitoring of the NHAV 93 mound has continued through 1995, including additional 

 precision bathymetric surveys, subbottom profiling, REMOTS® sediment-profile 

 photography, sediment surface grab samples for chemical analysis, and geotechnical coring. 

 The long-term focus of these operations has pertained to mound stability and 

 compaction/consolidation of the NHAV 93 mound; REMOTS® sediment-profile surveys 

 have determined the recolonization rate of the mound; and additional sediment cores and 

 grab samples investigated the potential for migration of contaminants into the overlying cap 

 material. The results of these datasets have been submitted to NED under separate DAMOS 

 report titles. 



