EXECUTIVE SUMMARY (continued) 



The cap thickness over the NHAV 93 mound was found to meet the minimum cap 

 thickness requirements of the project, 0.5 m. A full spectrum subbottom profile survey 

 (X-Star), in conjunction with precision bathymetric and geotechnical core data, detected an 

 average of 0.75 m of cap material along the margins of the UDM deposit to 1.25 m at its 

 center. The subbottom profiler allowed for the quantification of the cap material deposited 

 northwest of the NHAV buoy that previously could not be discerned through conventional 

 bathymetric data processing. Surface layer grain sizes were assessed with the use of 

 SAIC's Sediment Acoustic Characterization System (SACS) as well as REMOTS® 

 sediment-profile photography and bottom grab samples. The surface layers of cap material 

 over the NHAV 93 mound were comprised mainly of silt and clay. The MQR mound 

 exhibited a heterogeneous mixmre of grain sizes ranging from silt and clay at the margins 

 of the mound to pebble and cobble size grains at the center of the supplemental CDM 

 deposit. 



Benthic recolonization of the project mounds was also determined from the 

 REMOTS® photographs. Data collected at the MQR and NHAV 93 mounds were 

 compared to three reference areas surrounding CLIS. The MQR and the majority of 

 NHAV 93 project mounds met or exceeded the predicted recolonization rates from the 

 DAMOS tiered monitoring and management protocol. Stage I assemblages were 

 predominant, and occasional Stage II or Stage III organisms were present at peripheral 

 stations. However, three stations on the NHAV 93 mound were found to be areas of 

 concern. Patchy Stage I communities and shallow redox potential discontinuity (RPD) 

 depths were apparent in REMOTS® photographs collected at Stations 200N, CTR, and 

 400S. 



In September 1994 additional sediment samples were collected to conduct Ampelisca 

 bioassay testing and determine whether further action by NED was required (i.e., cap 

 supplementation). The results of bioassay testing indicated no significant difference in 

 comparison to reference area sediments. Therefore no immediate action was required, but 

 as part of the DAMOS tiered monitoring protocol, RPD depths and successional stage 

 stams at Stations 200N, CTR, 400S continued to be closely monitored for changes in the 

 benthic community. 



REMOTS® photographs collected over reference area 2500W indicated a recent 

 benthic disturbance consistent with the effects of trawling activity. Surface layer 

 dismrbances and shallow RPD depths made comparisons between 2500W and the project 

 mounds difficult. However, the multiple reference area approach used by the DAMOS 

 Program required the collection of REMOTS® data at two additional reference areas, 

 CLIS-REF and 4500E. The data collected at CLIS-REF and 4500E displayed the 



