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5.0 CONCLUSIONS 



As the most active disposal site in New England, CLIS has been closely monitored 

 since 1979. The July 1996 survey over CLIS was performed to delineate the areal extent 

 and initial colonization of the disposal mound formed during the 1995-96 disposal season. 

 In addition, monitoring of the CLIS 94, NHAV 93, and MQR mounds was conducted to 

 document disposal mound consolidation and continued benthic habitat recovery. 



The CLIS 95 mound is the newest bottom feamre at the disposal site and is an 

 example of a small, capped dredged material disposal mound. An estimated barge volume 

 of 16,300 m3 of UDM followed by 50,100 m' of CDM yielded a small, but distinct, 

 bottom feature on the CLIS seafloor 3.75 m high and approximately 200 m in diameter, 

 with a CDM to UDM ratio of 3 . 1 : 1 .0. No bathymetric data documenting the interim 

 stages of development were available. However, the compact nature of the deposit, the 

 reported barge release positions, the CDM to UDM ratio, and the results of the benthic 

 recolonization survey over CLIS 95 suggest the UDM deposit has been completely capped. 

 Continued monitoring of the CLIS 95 mound is not a necessity, but the collection of 

 bathymetric data over the next one to two years will add to our understanding of long-term 

 consolidation patterns within capped dredged material disposal mounds. 



The benthic conditions, as characterized by REMOTS® sediment-profile 

 photography, indicate rapid benthic community recovery over the surface of the CLIS 95 

 mound. The OSI values calculated for the CLIS 95 mound met or exceeded that of the 

 reference areas, facilitated by a higher organic content within the newly deposited 

 sediments. Periodic monitoring of the infaunal community occupying the surface 

 sediments of the CLIS 95 mound is recommended for the next several years to ensure that 

 a decline in benthic conditions does not occur. 



The continuing REMOTS® benthic community assessment for the centers of CLIS 

 94 and NHAV 93 indicates significant improvement over the majority of historic disposal 

 mounds. However, some reduction in the quality of the benthic environment was detected 

 at several stations, relative to the September 1995 survey. Stations lOON and lOOS over 

 CLIS 94 and Station 200N over NHAV 93 displayed lower OSI values in comparison to 

 1995 results, as well as indications of a low DO environment despite higher dissolved 

 oxygen concentrations in the central Long Island Sound region. The decline in habitat 

 quality at these stations may be attributed to high SOD rather than a hypoxic event in the 

 overlying water. Barring a dramatic dismrbance, complete benthic recovery should be 

 achieved within the next few years as continued chemical oxidation and increased 

 biological activity dissipate the organic load within the sediment deposits. Monitoring of 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1996 



