^ 



sediments) is variable in each sample (Lake et al. 1990, O'Connor 1990). Normalization 

 to fme-grained material is performed to account for the variability of TOC concentrations 

 in sediments that have been influenced by anthropogenic activity near urban activities 

 (NOAA 1991). In this report, PAHs and metals were normalized to TOC and the fine- 

 grained fraction of the sediments by dividing the raw chemical concentration (in mg-l"') of 

 the sediment by the percentage of TOC or fine-grained material at each station. Complete 

 results of the normalization process are presented in Appendices D and E, Table 1 (PAHs) 

 and Appendices D and E, Table 2 (metals). The NHAV 93 mound TOC and fine-grained 

 normalized metals and PAH data resulted in values that were within or below the 

 respective composite cap material ranges (Appendix A, Table 13). 



Bioturbation, or biological reworking of the surface sediments, is the primary 

 process which incorporates molecular oxygen into the surface sediments, increasing the 

 RPD depth. Biological demand, chemical redox reactions, and detrital decay reduce 

 oxygen concentrations within the sediment, and as a result reduce the apparent RPD. 

 Higher RPD depths indicate increased bioturbation as a result of a well-established benthic 

 community with low mortality and chemical oxygen demand (COD). 



A lack of a well-established benthic community was the motivating factor behind 

 the cap replenishment operations on the MQR mound. The recolonization rate of the MQR 

 mound had been slow after benthic disturbances, relative to adjacent CLIS disposal mounds 

 and reference area conditions. After a series of REMOTS® surveys from 1983 through 

 1992, it was recommended that MQR be capped with additional clean material to replenish 

 the existing cap and further isolate the Black Rock Harbor contaminants (Murray 1996b). 



To supplement the existing cap during the 1993/94 disposal season, 65,000 m^ of 

 material was deposited over the surface of the MQR mound. Disposal at the CD A buoy 

 commenced in mid-October 1993 with the deposition of UDM dredged from the inner 

 basin of the US Coast Guard facility in New Haven Harbor. This UDM deposit was 

 subsequently capped with CDM excavated from the US Coast Guard access channel in late 

 October 1993. This CDM deposit was followed by an estimated barge volume of 

 44,000 m^ of capping material originating from Housatonic River in December 1993 and 

 May 1994; Guilford Harbor in January 1994; Lex Atlantic Gateway in February 1994; and 

 Pine Orchard Harbor in April 1994. 



As a result, the mound increased in height 1.5 m, shifting the apex of the mound 

 100 m to the northeast. Hard SACS returns, confirmed by REMOTS® photographs and 

 grab samples, indicated that coarse sand, pebble, and cobble size grains were deposited on 

 the surface of the MQR mound along with silts and clays as components of the 

 supplemental capping material. The results of the grain size analysis for the MQR mound 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1994 



