EXECUTIVE SUMMARY (continued) 



photography results. A survey conducted in July 1994 detected a 1.5 m increase in mound 

 height, a change in the position of the mound apex, and an improved benthic community 

 structure, resulting from the deposition of additional CDM. 



The boundaries of the 2100 m x 2100 m July 1996 bathymetric survey at CLIS 

 incorporated approximately 75% of the historic MQR mound. Depth difference 

 calculations based on the July 1994 bathymetric data discovered small to moderate pockets 

 of consolidation near the apex and southwestern flank of MQR. This consolidation over 

 the surface of the MQR mound is apparently the result of de-watering of the underlying 

 silts and clays, related to the loading that resulted from the recent deposition of CDM. 



The sediment-profile photographs collected over the CLIS project mounds and 

 reference areas provided a wealth of information pertaining to the physical, biological, and 

 chemical status of the surficial sediment layers. Data pertaining to the physical appearance 

 of the material displayed no evidence of particle re-suspension or erosion at the sediment- 

 water interface. The detection of Stage III activity was widespread indicating the presence 

 of a stable benthic community population over the majority of the stations sampled. 

 Although increased sediment oxygen demand may have affected the results obtained from a 

 few stations, the benthic conditions detected during the July 1996 REMOTS® sediment- 

 profile photography survey show distinct improvement relative to September 1995. 

 Comparisons between REMOTS® images collected over the disposal mounds and CLIS 

 reference areas (2500W, 4500E, and CLIS-REF) show significant increases in RPD 

 depths, resulting in higher OSI values. In 1995, a trend of shallower than expected RPD 

 depths and indications of low dissolved oxygen (DO) concentrations was observed due to 

 the development of hypoxic conditions across the region. The 1996 Connecticut 

 Department of Environmental Protection (CTDEP), Bureau of Water Management water 

 quality data set was used to evaluate and compare the onset and severity of seasonal 

 hypoxia in the bottom waters of Long Island Sound relative to 1995. 



Seasonal hypoxia (DO concentrations <3.0 mg 1"') generally occurs within the 

 western and central Long Island Sound regions in mid to late August. However, the onset 

 and severity of seasonal hypoxia are directly dependent on many other environmental 

 factors (i.e., nutrient input, frequency of storms, rainfall, fresh water input, water 

 temperature, etc.). It appears that, by conducting benthic community assessment survey 

 operations in early summer (mid-June to mid-July), before the development of hypoxia and 

 the deterioration of benthic conditions, a more realistic perspective on the condition of the 

 benthic environment can be gained. 



