68 



Metal analyses performed by the NED 

 laboratory (using EPA methods) have been 

 the most common suite of analyses for 

 both the dredged material source areas and 

 surface grab samples from the capped 

 mounds. The replicability of NED 

 analyses can be shown by the summary of 

 reference station data (Figure 3-16). The 

 use of the historical record of sediment 

 chemistry samples collected during the 

 DAMOS Program is a technique which 

 can be employed both to track the 

 development of a capped mound and to 

 trace the sources of the material years 

 after it was deposited (Section 4.0). 



For example, the four sources of the 

 MQR mound (Mill and Quinnipiac Rivers, 

 Black Rock, and New Haven Harbors) 

 were sampled before each phase of 

 disposal, as were the sediments from the 

 disposal area itself (Figures 3-17 and 3- 

 18). These data indicated that Cd 

 concentrations of Quinnipiac River 

 sediments, as measured by the NED 

 laboratory, were higher than those of the 

 Mill River (Figure 3-17). One distinct 

 characteristic of the mound sediments is 

 the relatively high Cu concentrations of 

 Black Rock Harbor sediments. As 

 mentioned in Section 4.0, these 

 characteristics are useful in distinguishing 

 source material in cores taken through 

 several capped mounds. 



Sediment samples taken from the 

 surface of the MQR mound after 

 deposition of Mill and Quinnipiac River 

 dredged material show the record of 

 surface chemistry (Figure 3-19). Again, 

 Cd concentrations of post-Quinnipiac River 



dredging are relatively higher than the Mill 

 River sediments. Surface sediment grab 

 samples taken since deposition of both 

 Black Rock Harbor and New Haven 

 Harbor sediments have indicated stable and 

 relatively low trace metal concentrations 

 since cap deposition (Figure 3-19). 



Chemical data from MQR source areas 

 were normalized to Cu in order to form 

 "fields" of concentrations of sediments 

 from different source areas. Black Rock 

 Harbor samples, due to excessive Cu 

 concentrations, form a relatively discrete 

 field (Figure 3-20A). Although there is 

 some separation of Mill and Quinnipiac 

 River fields due to the relative enrichment 

 of Cd in Quinnipiac sediments, New 

 Haven Harbor sediments bridge the gap 

 between these two fields. The fact that 

 New Haven Harbor data overlap with both 

 the Mill and Quinnipiac River data is not 

 surprising since New Haven Harbor is a 

 depository for sediments from both of 

 these rivers (Figure 2-6). 



Recently, MQR was cored in order to 

 determine the chemical nature of the 

 capping material, and to test the hypothesis 

 that Black Rock Harbor material was 

 concentrated at the top of the capped 

 mound. Results were plotted with these 

 source data and showed that most of the 

 cap material at MQR has metal 

 concentrations within the range found in 

 upper New Haven/lower Quinnipiac River 

 sediments (Figure 3-20B; Murray 1992). 



Coring results from MQR do not 

 support the contention that the slow 

 biological recovery at MQR was due to the 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



