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the benthic environment over the CLIS 94 and NHAV 93 mounds should continue for the 

 next one to two years. 



The bathymetric data collected over the CLIS 94, NHAV 93, and MQR mounds 

 during the July 1996 field operations adds to the comprehensive time-series data set 

 currently in existence for CLIS. Comparisons to earlier stages of development for the 

 capped mounds find small to moderate pockets of consolidation over the surfaces of the 

 three bottom features, suggesting the long-term behavior patterns are in agreement with the 

 results of previous consolidation studies (Poindexter-Rollings 1990; Silva et al. 1994). All 

 three mounds are expected to consolidate slowly over the next five to ten years as gradual 

 pore water extrusion and compression of the underlying ambient material are driven by the 

 weight of the dredged material deposits. It is recommended that bathymetric data be 

 collected over the NHAV 93 mound on an every other year basis for the next five to ten 

 years as the disposal mound fully consolidates to enhance our understanding of the physical 

 processes and effects of consolidation within large sediment deposits. 



Results from the July 1996 REMOTS® sediment-profile photography survey 

 indicate that all three reference areas exhibited healthy benthic conditions as demonstrated 

 by deep RPDs and mature benthic assemblages, yielding relatively high reference OSI 

 values. However, one replicate photograph collected at ST A 9, within a 300m of the 

 center of CLIS-REF, exhibited an anomalous pocket of low reflectance material within a 

 chaotic sediment fabric. Benthic disturbances that display these characteristics are often 

 related to the deposition of non-ambient sediments, but are usually more widespread. The 

 presence of a large macrofaunal burrow structure and the localized nature of this 

 disturbance may suggest another origin. A detailed investigation of the seafloor 

 surrounding ST A 9 is recommended during the 1997 environmental monitoring effort at 

 CLIS to better characterize these sediments. 



Past DAMOS monitoring activity at the Long Island Sound disposal sites was 

 performed in mid-summer (late July to August) to allow an increase in bottom water 

 temperatures to increase bioturbational activity and promote benthic community recovery 

 after the conclusion of the disposal season. This practice tended to promote the completion 

 of community assessment activities during a period of seasonal hypoxia or near-hypoxia 

 (5.0 mg-r' to 3.0 mg r'), skewing the entire data set. Comparisons between the July 1996 

 benthic community assessment survey and previous data sets suggest that the improvement 

 in benthic health is attributed to conducting community assessment survey operations in 

 mid- July. The timing of 1996 survey activity at CLIS was successful in avoiding the 

 recurring seasonal hypoxia in the central Long Island Sound region. As a result, the data 

 collected during this survey did not exhibit the profoundly negative effects associated with 

 the lower bottom water DO concentrations. The continued practice of conducting benthic 



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



