47 



Core Zl, obtained at 41°09.099' N, 72°53.390' W, approximately 100 m southeast 

 of the NHAV 93 buoy position, sampled the apex of the CAD mound (Figure 3-16). This 

 geotechnical core penetrated 143 cm into the center of the NHAV 93 dredged material 

 deposit. The top 44 cm of Core Zl was made up of a uniform layer of black silty clay with 

 scattered shell fragments (Figure 3-18). At 46 cm of penetration, layers of sandy silt are 

 visible. A line between CDM and UDM in Core Zl becomes visible at 66 cm of 

 penetration with the transition from black and grey sandy silt, to a layer of black sand and 

 shell fragments over black clayey silt with sand, gravel, and wood fragments. The UDM 

 deposit continues from 66 cm to 143 cm of penetration. No historic dredged material or 

 ambient Long Island Sound sediments were detected. 



Core Z, taken at 41°09.180' N, 72°53.513' W, approximately 110 m northwest of 

 NHAV 93 buoy position, penetrated to a depth of 250 cm. The top 120 cm of Core Z was 

 composed of black clayey silt with traces of sand (Figure 3-18). A layer of fme-grained 

 brown to red sand at 120 cm divided the uniform silt layer from the remainder of the core. 

 The border between CDM and UDM was determined by a distinct increase in sediment pore 

 water at 75 cm of penetration. The first layer of UDM is characterized as black clayey silt, 

 similar to the overlying CDM deposit. Alternating layers of sand and silt continued down 

 the core to a penetration depth of 220 cm where a transition from NHAV 93 mound UDM 

 to historic dredged material was discovered. 



3.2 MQR Mound 



3.2.1 Bathymetry 



The MQR mound, centered at 41°08.600' N, 72°53.900' W, received a total of 

 65,000 m^ of new dredged material to supplement the existing cap (Figure 3-2). This 

 material was generated by a de facto capping operation originating from the US Coast Guard 

 facility in New Haven Harbor; additional volumes of CDM were generated by the Guilford 

 Harbor, Housatonic River, Lex Atlantic Gateway, and Pine Orchard Harbor dredging 

 projects. A smaller depth model (850 m x 1000 m) of the area surrounding the MQR 

 mound was constructed in order to determine the placement and quantify the volume of die 

 recently deposited dredged material over the mound (Figure 3-19). The MQR mound now 

 exhibits a diameter of 425 m at its base and a depth of 17.5 m at the apex. The last 

 bathymetric survey conducted at the MQR mound was in December 1991. 



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



