17 



4.0 DISCUSSION 



4.1 Summary of Ecological Conditions at MQR, 1992 



All of the REMOTS® parameters indicated that the benthic environment has improved 

 in the year between the 1991 and 1992 surveys. No apparent "fresh" dredged material was 

 observed in 1992. This was a significant difference from the results in 1991. The fresh 

 dredged material appearance was a function of the low RPD (and low DO) conditions at 

 several stations in 1991 combined with boundary roughness values which emulated the 

 appearance of newly disposed dredged material. The combination of increased RPD, less 

 methane, and the lack of low DO in 1992 resulted in overall higher OSIs relative to the 1991 

 survey. 



Although the 1992 REMOTS® results indicate an improvement in benthic habitat over 

 1991, the fact remains that several parameters are still significantly out of the range of CLIS 

 reference values. Comparing REMOTS® results between different years and stations is 

 somewhat risky; however, the overall historical trend of OSIs at the CLIS reference area 

 indicates that the average OSI of the undisturbed area hovers between 8 and 10. The 

 persistence of slow recolonization at MQR and the continuing presence of methane almost 10 

 years after dredged material deposition suggest that there is still an inherent quality of MQR 

 sediments which discourages normal benthic recolonization. 



4.2 Historical Progression of the MQR Benthic Habitat 



The DAMOS Program benefits from the fact that over ten years of data have been 

 collected at MQR. MQR historically has been the slowest among the disposal mounds at 

 CLIS to recover from stress. This characteristic has triggered more intensive monitoring in 

 recent years (Table 1-1). Observations from REMOTS® surveys were summarized in order 

 to approach the problem of MQR benthic habitat recovery from a historical context. In 

 summarizing these data, OSI values from the CLIS reference areas were averaged for each 

 time period the site was sampled. Historical OSIs from MQR and other CLIS dredged 

 material disposal mounds were plotted relative to the CLIS reference area to map the long- 

 term trends of habitat quality (Figure 4-1, Figure 4-2). 



A concise summary of several CLIS mounds is necessary as a reference to the MQR 

 mound. A complete history of the disposal mounds at CLIS was recently compiled (SAIC 

 1994). In the spring of 1983, contaminated material from Black Rock Harbor was disposed 

 at several CLIS mounds including MQR, the Field Verification Program mound (FVP), and 

 Cap Sites 1 and 2 (CS-1 and CS-2; Figure 1-1). Both Cap Site mounds and MQR were 

 capped with material from New Haven Harbor, while FVP remained uncapped. 



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992 



