46 



5.0 DISCUSSION 



The subaqueous capping of dredged material was introduced as a disposal technique 

 to the DAMOS Program in 1979. The practices behind this disposal technique were 

 improved during the early- 1980s and continue to be employed in the successful completion 

 of capping projects at CLIS, the New London Disposal Site (NLDS), and Portland 

 Disposal Site (PDS; SAIC 1995). Over the years, data have shown that both sand and silt 

 are effective capping materials. The low permeability and chemically adsorptive properties 

 of silt constitute good capping material. Although sand caps provide greater resistance to 

 erosion during storm events, a 0.5 to 1.0 m layer of silt was used as capping material at 

 CLIS due to its similarity to the ambient grain size, relative abundance, and availability to 

 the New Haven Capping Project. 



The NHAV 93 disposal mound received an estimated barge volume of 

 1,159,000 m 3 of material dredged from New Haven Harbor and the surrounding area as 

 part of the New Haven Capping Project. The capping project conducted at CLIS during 

 the 1993-1994 disposal season was atypical in several ways: 1) Dredged material was 

 deposited in a depression formed by a ring of seven historic mounds to restrict the lateral 

 spread of the UDM apron; 2) The resulting disposal mound was successfully capped with 

 quantities of CDM less than the total volume of the UDM deposit; 3) A remarkable 

 sequence of five precision bathymetric, two REMOTS® sediment-profile, and three 

 geotechnical coring surveys were conducted by SAIC at various stages of NHAV 93 

 mound development, creating a comprehensive time-series dataset documenting the 

 construction of the CAD mound. 



The data collected over the NHAV 93 mound indicate that lateral containment of 

 the UDM deposit was critical in the completion of the New Haven Capping Project. 

 Utilization of the basin-like feature, created by the ring of disposal mounds, to receive 

 large volumes of UDM for environmentally sound and cost-effective disposal is the 

 culmination of many years of thoughtful planning and disposal. Since the inception of the 

 DAMOS Program, a ten-year cycle of dredging and disposal operations has been 

 established in the central Long Island Sound region. With the development of the NHAV 

 74, NHAV 83, and NHAV 93 mounds, NED has estimated that large scale dredging 

 operations must be conducted in New Haven Harbor and the Quinnipiac River every ten 

 years to maintain adequate depths for commercial, military, and private vessels (Morris 

 1994). 



The ten-year time frame allows for the completion of many small dredging 

 operations in regional harbors, channels, and docking facilities. The disposal of modest 

 volumes of material aids in the preparation for large scale projects with the magnitude of 



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



