41_ 



278.000 m 3 . The comparison shows that federal cap material and the privately funded 

 disposal and cap material were deposited on the southern side of the mound. The 

 76,000 m 3 barge volume of additional federal cap material that was disposed to the 

 northwest of the NHAV buoy location prior to the precap survey could not be accounted 

 for in this comparison due to its deposition prior to the completion of the precap 

 bathymetry. 



4.2 REMOTS® Sediment-Profile Surveys 



The REMOTS® baseline survey was conducted over the following inactive disposal 

 mounds: NORWALK, CLIS-87, CLIS-88, CLIS-89, CLIS-90, SP, and the east-southeast 

 valley. The results were used to assess the stability of the disposal mounds, allow accurate 

 placement of dredged material in the basin formed by these mounds, and to document the 

 status of the benthic community. In addition, NED planned to place a sediment cap over 

 the experimental FVP mound in the northeast quadrant of CLIS using any excess CDM 

 generated by the New Haven Capping Project. Therefore, triplicate photographs were also 

 obtained at the historic FVP mound during the precap survey to allow comparisons in the 

 event that excess CDM was available for deposition. 



4.2.1 Grain Size Distribution 



The major modal grain sizes over the majority of the mounds were very fine sand 

 (4-3 phi) and some silt/clay (>4 phi) sediments at the CLIS-87 and CLIS-88 mounds. Fine 

 sands (3-2 phi) were the major mode at a few of the stations located on the CLIS-89 and 

 SP mounds. Several stations had surface layers of coarse sands and gravel. The major 

 modal grain sizes at the FVP mound were very fine sands (4-3 phi); some silt/clay (>4 phi) 

 sediments were present at stations 50E, 50W, 100W, and 100S. The range in grain size 

 included gravel and very coarse sands to silt/clay. 



4.2.2 Prism Penetration Depth 



Dredged material often has different shear strengths and bearing capacities than 

 ambient bottom sediments. The prism penetration depth into the bottom sediments depends 

 on the force exerted by the optical prism and bearing strength of the sediment. The optical 

 prism of the REMOTS® camera penetrates the bottom sediment under a static driving force 

 imparted by the weight of the descending optical prism, camera housing, supporting 

 mechanism, and weight packs. Soft silt/clay sediments will generally produce photographs 

 showing two-thirds to full penetration (15-20 cm), while coarser grained material yields 

 lesser penetration values (sands 8-12 cm; gravel 3-10 cm). 



Monitoring Surveys of the New Haven Capping Project, 1993-1994 



