1.0 INTRODUCTION 



The Mill-Quinnipiac River Disposal Mound (MQR), which began receiving dredged 

 material ten years ago, continues to be the most enigmatic capped mound monitored by the 

 Disposal Area Monitoring System (DAMOS) Program. It is located in the southwest 

 quadrant of the Central Long Island Sound Disposal Site (CLIS; Figure 1-1). The capped 

 mound is actually a complex interlayered mound consisting of material from the Mill River, 

 the Quinnipiac River, Black Rock Harbor, and New Haven Harbor. 



Monitoring results from MQR have indicated slower biological recolonization rates 

 after disposal relative to other CLIS mounds. These monitoring data have included 

 REMOTS® photographs (as recently as the 1991 CLIS survey), sediment sampling and 

 chemical analyses, and bioassay results. The complicated disposal history at MQR, in 

 tandem with the unusual monitoring results gathered since disposal completion, prompted a 

 more intensive investigation of the MQR mound following the tiered monitoring protocols 

 initiated by the US Army Corps of Engineers, New England Division (NED) to manage 

 dredged material disposal mounds (Germano et al. 1994). According to the protocols, 

 unacceptable benthic community response as documented by REMOTS® should be followed 

 up by a bioassay test. If there is a toxic response, the source of contamination should be 

 analyzed through vertical profiling, or sediment coring (Germano et al. 1994). 



Sediment cores were recovered from the MQR mound in the summer of 1991, 

 described, and sampled at discrete depths representing visually distinct intervals. The 

 objective of the coring operation was to identify sedimentary horizons within the MQR 

 mound which represented the remnant disposed dredged material, and to use this stratigraphic 

 reconstruction to explain the unusual postdepositional response at MQR. In order to 

 accomplish this, core samples from the mound were visually and chemically compared with 

 historical DAMOS data from MQR dredged material sources. 



1.1 Disposal Operations at the MQR Mound, 1982-1983 



During the spring of 1982, the NED initiated a capping project for sediments to be 

 removed as part of federal maintenance dredging of areas in the Mill and Quinnipiac Rivers 

 adjoining the northern limits of New Haven Harbor (Figure 1-2). Mill River material was 

 characterized by high concentrations of fibrous residue or wood pulp, which limited sediment 

 cohesion. This unique sediment texture combined with the relatively high water content 

 percentages measured in the Mill River sediments increased the potential for sediment 

 dispersion following disposal. In addition, chemical analysis of the Mill River sediments 

 indicated high concentrations for most of the heavy metals tested. Cadmium (Cd), for 

 example, was measured in concentrations up to 260 ppm (Table 1-1). 



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



