EXECUTIVE SUMMARY (cont.) 



• monitor the benthic ecosystem 

 response and biological recovery 

 rates; 



• analyze the ability of the caps to 

 isolate chemical contaminants. 



Physical monitoring of the early 

 capped mounds was accomplished 

 primarily with acoustic and visual 

 methods. These data indicate that capped 

 mounds have been stable even after the 

 passage of three hurricanes. There has 

 been little evidence of erosion or physical 

 breaching of capped mounds. Biological 

 monitoring has confirmed that, in general, 

 there has been no adverse effect on biota 

 due to contaminants located within the 

 mound (exception noted below). Whole- 

 sediment chemistry data have been 

 collected to assess contaminant levels at 

 the surface of the capped mounds. These 

 results have shown that contaminant 

 concentrations of surface sediments have 

 remained near background levels since 

 capping. The term "contaminant" is used 

 here to describe those compounds, either 

 natural or anthropogenic, which, in high 

 enough concentrations, may pose a human 

 health threat. 



Monitoring results have, however, also 

 revealed problems during the 

 developmental stage of some of the capped 

 mounds. One capped mound in particular 

 (MQR) showed signs of subnormal rates of 

 biological recolonization. The complex 

 disposal history of MQR did not conform 

 to the idealized model of a capped mound, 

 and, in fact, served to test the developing 

 capping protocols. Complications 

 discovered during monitoring were used to 

 confirm the original recommendations for 

 successfully capped mounds and to 



establish new guidelines for operational 

 and monitoring procedures. 



A coring investigation was initiated to 

 resolve questions concerning the chemical 

 integrity of the interior of the mounds. 

 Many of the recovered cores showed a 

 distinct chemical boundary between the 

 contaminated material and the cleaner 

 material of the cap, up to 11 years after 

 capping. The investigation documented 

 that the texture and distribution of 

 contaminants in the disposed sediments 

 depend to some extent on the dredging and 

 disposal techniques used to form the 

 capped mound. 



Monitoring protocols have been refined 

 since the initiation of DAMOS, and a new 

 approach to monitoring has been developed 

 that focuses on dredged material 

 management. The new approach, known 

 as tiered monitoring, uses a flow chart of 

 monitoring approaches and results to help 

 the dredged material manager make 

 decisions on disposal and capping 

 alternatives. 



Final recommendations from the early 

 DAMOS capping experience include 

 specific tasks to be completed before, 

 during, and after the formation of a capped 

 mound. Pre-operational planning will 

 ensure optimal conditions for a 

 successfully capped mound. Dredge and 

 disposal operations should be organized 

 and well-documented; the use of precision 

 navigation and a taut-wired, moored buoy 

 to ensure precise disposal of dredged 

 material are recommended. Finally, a 

 reasonable and efficient monitoring 

 program should be in place before 

 dredging begins. 



