50 



5.0 CONCLUSIONS 



In 1991 the Central Long Island Disposal Site (CLIS) survey revealed that active 

 disposal in 1990-1991 created a stable mound with predicted characteristics. Inactive disposal 

 mounds were also stable and require no special monitoring with the exception of MQR which 

 should be monitored in 1992. The sediment chemistry at the three reference sites and 

 dissolved oxygen levels are consistent with conditions in central Long Island Sound. 



The June 1991 monitoring cruise at CLIS was designed to delineate the areal extent of 

 the dredged material and to assess possible environmental impact of past and recent disposal by 

 monitoring the recolonization status of the resident infaunal community. The dredged material 

 did form the distinct mound predicted at the CLIS-90 buoy location. The radius of the mound 

 detected acoustically was not as large as predicted. At CS-90-1, the additional cap material 

 added to the existing mound, and two areas of 20 cm thick material were detected acoustically. 

 The detection of dredged material by REMOTS® photographs increased the observed areal 

 extent of "fresh" dredged material beyond that measured acoustically. However, the dredged 

 material footprint associated with the CLIS-90 mound was difficult to distinguish from older 

 dredged material. Material from disposal activity over the last five years overlaps and makes 

 it difficult to distinguish "fresh" dredged material. 



Both the bathymetry and REMOTS® map of fresh dredged material supported the 

 prediction that the CLIS-90 buoy mound would be within a radius of 200 to 250 m. Stage I 

 seres dominated the CLIS-90 buoy mound and the CS-90-1 mound as predicted. Stage III 

 seres dominated the inactive FVP, NHAV-74, CLIS-88, and CLIS-89 mounds as predicted for 

 normal colonization. These data indicate that no further special chemical or physical 

 monitoring is required at these mounds at this time. The MQR inactive mound had four 

 stations with Stage I taxa, and shallow RPD depths were measured around the mound center. 

 Stations E5 and D7, south and west of CLIS-89, were azoic or had low OSI values with 

 evidence of trawling. These areas, MQR, E5, and D7, should be reevaluated in 1992. 



Dissolved oxygen levels in the bottom water, and metals and PAH baseline levels in the 

 sediments, were measured at CLIS and the three reference areas to assess environmental 

 quality. The DO levels at CLIS were spatially homogenous between reference areas and the 

 disposal site, showing no hypoxia and varying between 6.3 and 6.77 mg-1" 1 . Results of the 

 metal analyses indicate relatively low levels of Cd, Pb, and Zn, consistent with previous 

 measurements. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, June 1991 



