57 



5.0 CONCLUSIONS 



• Three primary lithologies were recovered in MQR cores. The top 1-1.5 

 meters of every core contained black silty clay with uniform metals 

 concentrations. Thickness estimates of dredged material units indicated that 

 this unit was New Haven Harbor material. Sandier material containing plant 

 fragments and clasts was recovered in every core below the upper New Haven 

 unit. Trace metal ratios indicated that these samples were remnants of either 

 Mill or Quinnipiac River sediments, rather than from Black Rock Harbor. 

 Basement material representing Central Long Island Sound background 

 sediment was recovered in at least one core (MQR6), indicating that this core 

 was recovered from the mound flanks. 



• Comparison with prior core data from capped mounds recovered at CLIS 

 indicated that New Haven material from the MQR cap contained higher 

 concentrations of PAHs relative to the New Haven material caps of other CLIS 

 mounds. Since there has been no prior evidence of mobilization of PAHs from 

 capped sediments into the overlying caps, the capping sediments at MQR most 

 likely were originally higher in these compounds. 



• Trace metal ratios indicated that New Haven sediments were intermediate in 

 chemical character to Mill and Quinnipiac River sediments. From these data 

 and the disposal sequence, it is clear that the cap material was derived from 

 inner New Haven Harbor, and contained some of the contaminants associated 

 with the inflowing Mill and Quinnipiac rivers. 



• According to tiered monitoring protocols, the coring results indicate that MQR 

 should be recapped as soon as material is available. 



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



