45_ 



not detectable by use of bathymetric methods. The use of different types of methods to 

 calculate dredged material volumes are currently under investigation (Murray 1994). 



4.2 Metal Ratios of MQR Source Materials 



Trace metal data from the four sources of dredged material present at the MQR 

 mound, in addition to historical CLIS reference station data, were compiled. Zinc, Cu, and 

 Cd concentrations were plotted for each source (Figure 4-1). The few samples from the Mill 

 and Quinnipiac Rivers (n=10 and 6, respectively) reduce the statistical significance of the 

 frequency distributions; however, some trends are worth noting. In general, higher Zn and 

 Cu concentrations were present in Mill River sediments, while higher Cd concentrations were 

 measured in Quinnipiac River sediments (Figure 4-1). Black Rock Harbor sediments had, 

 overall, the highest concentrations of all three metals (Figure 4-2). New Haven Harbor 

 sediments were generally low in all three metals relative to the other source areas; however, 

 some of the New Haven samples still had 10 times the trace metal concentrations of CLIS 

 reference station samples (Figure 4-3). 



Sediment samples were taken and analyzed for trace metals at the completion of each 

 phase of formation of the MQR mound (Morton et al. 1984b). Results confirmed that Cd 

 concentrations of Quinnipiac River sediments were higher than those of Mill River (Figure 4- 

 4). Chemistry samples taken at the surface of the MQR mound following deposition of 

 Black Rock/New Haven Harbor sediments have indicated fairly stable and relatively low 

 trace metal concentrations since final cap deposition (Figure 4-4). 



Most of the trace metal concentrations of the MQR core samples fell within upper 

 New Haven/lower Quinnipiac Zn and Cu concentration ranges (Figure 4-5, A, B). The 

 distribution of New Haven Harbor, Mill River, and Quinnipiac River Zn and Cu 

 concentrations overlapped, probably since some of the sediment from the two rivers are 

 transported to, and settle into, the New Haven Harbor. Two theoretical "mixing lines" 

 established the separation of Black Rock Harbor from the other sources, primarily due to the 

 excess of Cu in Black Rock Harbor sediments (Figure 4-5, A). 



The high Cu concentration in Black Rock sediments has been noted since the original 

 Black Rock Harbor results were reported, and were confirmed in the recent coring operations 

 at three other CLIS capped mounds (SAIC 1994). The three mounds cored were Stamford- 

 New Haven North (STNH-N), Stamford-New Haven South (STNH-S), and Cap Site 2 (CS- 

 2). Results from these cores showed that many of the samples taken from the mounds fell 

 into New Haven Harbor concentration ranges and were classified as being capping material 

 (Figure 4-6). STNH-N and STNH-S received contaminated material to be capped from 

 Stamford Harbor, whereas CS-2 received material from Black Rock Harbor at the same time 

 as MQR. Samples from these three capped mounds reflected these two source areas when 

 compared with the original data collected at the time of disposal (Figure 4-6). 



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991 



