^0 



(Figures 3-12 and 3-13). The results of the 10-day Ampelisca bioassay showed no 

 significant differences between the sediments collected over the NHAV 93 mound relative 

 to the reference sediments of the historic Southern Reference Site (Mueller 1994). 



The mean survivability percentage in the project sediments was consistently above 

 80 (CTR 81 %, 400S 84%). In comparison, the mean reference sediment survival rate of 

 90% indicates no statistically significant differences in the samples (Appendix A, Table 9). 

 As a result of the survival rate acceptability within the reference and project sediments, no 

 toxicity was observed in the sediments of either NHAV 93 station. The three areas of 

 concern will continue to be monitored on an annual basis to verify improvement in benthic 

 conditions. 



3.1.5 Sediment Chemistry and Grain Size 



A total of eleven sediment chemistry grabs were collected over the NHAV 93 

 mound and analyzed relative to the CLIS reference areas. In addition, the July 1994 

 results were compared to data sets collected as part of the pre-dredging chemical testing of 

 the outer New Haven Harbor sediments. Detailed tables displaying the raw sediment 

 chemistry results for the NHAV 93 mound can be found in Appendix C. Chemistry data 

 normalized to TOC and fine-grained material content are located in Appendices D and E; 

 further details pertaining to the process of normalization can be found in Section 4.0 of this 

 report. 



Results of the grain size analysis for the NHAV 93 mound indicate that the capping 

 sediments are composed mainly of fine-grained material, averaging 70.5% fines (Appendix 

 C, Tables 1 and 8). Individual station values for fine-grained materials ranged from a low 

 of 65.3 % at Station NH-3 to a high of 74.4% at Station NH-1 1 . In general, these fine- 

 grained materials were comprised of nearly equal percentages of silts and clays, which 

 averaged 38.9% and 31.5%, respectively. Sand was the second major constituent of the 

 cap material, averaging 29.2%. There was relatively little variability between the sand 

 fractions of individual stations, ranging from 25.6% (Station NH-U) to 34.4% (Station 

 NH-10). The average percent gravel on the NHAV 93 mound was 0.3%. 



The NHAV 93 mound was found to have an average TOC concentration of 

 23360 ppm (Appendix C, Table 1). Among individual stations, TOC ranged from 

 12000 ppm (1.2%) at NH-8 to 28000 ppm (2.8%) at NH-4 (Figure 3-15). The distribution 

 of station values was generally uni-modal (approximately 26000 ppm), with the exception 

 of Stations NH-8 and NH-10, which were found to have concentrations of 12000 ppm and 

 15000 ppm, respectively. There was little variation between the remaining nine NHAV 93 

 chemistry stations, with TOC concentrations ranging from 24000 ppm to 28000 ppm. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1994 



