42 



The concentrations of LMW PAHs within the surface sediments of the NHAV 93 

 mound averaged 1.02 ppm, slightly higher in comparison to the CLIS reference areas 

 (Appendix C, Tables 2 and 8). Low Molecular Weight PAH concentrations ranged from 

 0.828 ppm to 1.119 ppm over the surface of the NHAV 93 mound (Figure 3-15). The 

 average value for HMW PAH concentration within the NHAV 93 sediments was 3.852 

 ppm. A greater variance between station values was noticed relative to the CLIS reference 

 areas, ranging from 2.601 ppm to 9.660 ppm. Overall, the total PAH concentrations over 

 the NHAV 93 mound were higher than the reference areas, with an average value of 4.872 

 ppm and a relatively high standard deviation (Appendix C. Tables 2 and 8). 



Average trace metal concentrations from the NHAV 93 mound sediments were 

 similar to the metals concentrations of the CLIS reference areas, and can be classified as 

 "low" in accordance to the guidelines set forth by the NERBC (NERBC 1980). Complete 

 metals results pertaining to the NHAV 93 mound and the CLIS reference areas can be 

 found in Appendix C, Tables 3 and 9, and Appendix A, Table 10. No anomalous metals 

 data were detected for this survey. 



3.1.6 Geotechnical Coring 



Geotechnical cores were taken at seven locations over the NHAV 93 project mound 

 to acquire data concerning the basement, dredged, and cap material layers. The cores 

 provided a deep, cross-sectional view of the multiple sediment layers that make up the 

 NHAV 93 mound (Figure 3-16). A total of seven cores were taken on southwest-northeast 

 and southeast-northwest transects of the mound, with depths of penetration varying 

 between 143 cm at Station Zl and 260 cm at Station W. All cores were split, visually 

 described, and analyzed for the various properties listed in section 2.6 of this document. A 

 comprehensive report documenting the laboratory results of all the geotechnical 

 characterization testing has been submitted by Armand J. Silva of the Marine 

 Geomechanics Laboratory, University of Rhode Island (Silva et al. 1994). 



Core V, obtained on the southwestern edge of the sampling grid (41°08.994' N, 

 72°53.627' W), penetrated 210 cm into the CLIS sediments. The visual description of 

 Core V shows alternating layers of black and olive-grey clayey silt, representative of 

 NHAV 93 cap material, to a depth of 160 cm from the top (Figure 3-17). A thin band of 

 dark sand and shell fragments was present at 160 cm, marking the CDM/UDM interface. 

 A 40 cm thick layer of iimer New Haven Harbor UDM and historic dredged material 

 (CLIS 88 and Norwalk) was detected as olive-green to gray silts and clays with varying 

 amounts of sand, gravel, and shell fragments. A layer of firm, olive-grey, clayey silt 

 indicative of ambient central Long Island Sound sediments was sampled at 200 cm of 

 penetration. 



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



