66 



benthic population at FVP appears to be more susceptible to environmental stress than the 

 benthic infaunal populations of the capped mounds. As a result, hypoxic events or other 

 disturbances tend to have a more pronounced and longer lasting effect on the invertebrates 

 inhabiting the uncapped sediments of FVP. 



The Field Verification Program was concluded in 1988 with a report which 

 determined that, in comparison to upland containment and wetland creation, subaqueous 

 mound development within a designated disposal site is the most environmentally sound 

 method of disposing of large volumes of UDM (Peddicord 1988). The FVP mound was 

 targeted for capping during the 1993 disposal season using excess CDM generated by the 

 New Haven Harbor maintenance dredging project A lack of an adequate volume of CDM 

 during the NHAV 93 mound development caused the deletion of the FVP capping 

 operations phase of the project (Morris et al. 1996). 



However, in order to improve the conditions of the benthic environment over the 

 FVP mound, an effort should be made in future disposal seasons to cap the experimental 

 mound with a 0.5 m thick layer of CDM. In addition, the adoption of the FPEIS disposal 

 site center of CLIS shifts the entire disposal site 362 m west-southwest, leaving the 

 majority of the FVP mound outside of the disposal site boundaries. In order to officially 

 conclude the EPA/WES joint experiment, the area surrounding the FVP mound, ideally, 

 should be restored to near ambient conditions with the placement of a silt cap over the 

 exposed UDM deposit. 



The cap over the NHAV 93 mound continues to support a stable benthic community 

 with marked improvement at stations CTR, 200N. and 400S relative to the July 1994 

 survey (Morris and Tufts 1997). Despite a decrease in dissolved oxygen, the mound was 

 supporting Stage I and Stage III individuals in the surface and subsurface sediments. There 

 was a noticeable lack of Stage II individuals over all three project mounds as well as the 

 three reference areas, suggesting an intolerance to lower water column induced DO 

 concentrations. The Stage I surface dwellers may have been able to tolerate the hypoxia or 

 may be the pioneering species recolonizing the sediments as DO concentrations began to 

 increase. 



The overall integrity of the NHAV 93 mound remains uncompromised eighteen 

 months after the completion of the New Haven Capping Project. There were no noticeable 

 changes in size or shape over the NHAV 93 mound, indicating the large bottom feature is 

 stable. The moderate consolidation detected since the completion of capping operations is 

 well within the forecast norm. The mound is expected to continue to consolidate as pore 

 water extrusion and basement material compression yield to the shear weight of the capped 

 sediment deposit over the coming years (Poindexter-Rollings 1990). 



Monitoring Cruise at the Central Long Island Sound Disposal Site, September 1995 



