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presence of a distinct nepheloid layer, or total absence of an RPD, are indications of 

 possible sediment resuspension or erosion. 



The depositional nature of the central Long Island Sound region provides adequate 

 containment of the dredged material deposited within the confines of CLIS. The low 

 current regime and restricted fetch associated with the central basin of Long Island Sound 

 minimize the risk of storm waves and tidal flow transporting dredged material outside the 

 disposal site boundaries. No sediment-profile photographs collected over the CLIS 

 disposal mounds have detected conditions indicative of dredged material loss or movement 

 within the past 11 years. 



In the fall of 1985, evidence of moderate disposal mound erosion was documented 

 at CLIS after the passage of Hurricane Gloria. REMOTS® images collected from six CLIS 

 disposal mounds (CS-1, CS-2, FVP, MQR, STNH-N, and STNH-S) found small to 

 moderate changes in replicate-averaged boundary roughness, RPD, and OSI values relative 

 to the pre-storm, annual monitoring survey (Parker and Revelas 1989). However, the 

 physical effects of the storm-induced currents and waves were restricted to the top 5 cm of 

 sediment, and directly related to sediment shear strength, a function of composition and 

 age of the deposit. As expected, mound centers displayed the most evidence of material 

 movement, but it was concluded that all capping layers remained intact. 



The NHAV 93 and CLIS 94 disposal mounds have been exposed to several strong 

 storm events during the past several years. These storms typically generate current 

 velocities and waves that surpass monthly averages, but tend to fall below the intensities 

 caused by passage of a hurricane. Although fluctuations in RPD depth and OSI values 

 related to SOD and hypoxia have been observed, neither disposal mound has displayed 

 signs of erosion in the surficial sediment layers. Low boundary roughness values and the 

 presence of silt and clay at the sediment-water interface reinforce the conclusion that the 

 apparent loss in mound height over these mounds is directly attributable to consolidation of 

 the dredged material deposit. 



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



