19_ 



Sound velocity measurements were obtained before and after the bathymetric survey 

 using a Seabird Instruments, Inc. SEACAT SBE 19-01 Conductivity, Temperature, and 

 Depth probe (CTD). The CTD was lowered over the side and allowed to equilibrate in 

 ambient seawater for one to two minutes before initiating the cast. The CTD provided a 

 profile of temperature, depth, salinity, and sound velocity in the water column. A mean 

 sound velocity was then calculated and applied to the bathymetric data. 



The data collected during each of the five bathymetric surveys were analyzed using 

 SAIC's Hydrographic Data Analysis System v. 1.03 (HDAS). During analysis, raw 

 bathymetric data were corrected for sound velocity and standardized to Mean Tidal Level. 

 The corrected bathymetric data were then used to construct depth models of the surveyed 

 area. Depth difference calculations were performed using the HDAS volume differencing 

 routines. In order to assist NED in achieving its goal, SAIC supplied detailed contour and 

 depth difference plots of the survey area 48 hours after each survey in order to modify the 

 disposal or capping activity to ensure proper containment and coverage. A detailed 

 discussion of the bathymetric analysis technique is given in SAIC Report No. 290 (Murray 

 and Selvitelli 1993). 



3.2 REMOTS® Sediment-Profile Surveys 



Actual REMOTS® station locations (latitude and longitude) occupied during the 

 surveys are provided in Appendix C along with analytical results. REMOTS® sediment- 

 profile surveys were conducted prior to disposal to assess baseline conditions and after 

 UDM disposal (precap survey) (Figure 1-2). Designed to obtain in situ profile images of 

 the top 20 cm of the sediment, the REMOTS® sediment-profile camera has been used to 

 detect and map the distribution of thin (0.1-20 cm) dredged material layers, and document 

 seafloor processes and organism-sediment relationships as they occur naturally on the 

 seafloor and on the disposal site (Rhoads and Germano 1990). Specific measurement/ 

 observational techniques for determining REMOTS® parameters include sediment grain 

 size major mode and range, prism penetration depth, surface boundary roughness, 

 presence/absence and size of mud clasts, apparent redox potential discontinuity (RPD) 

 depth, apparent presence/absence of sedimentary methane, infaunal successional stage, and 

 calculation of the REMOTS® Organism-Sediment Index (OSI). 



3.2.1 Baseline Survey 



During the September 1993 baseline survey, REMOTS® sediment-profile 

 photographs were obtained in triplicate from 30 stations surrounding the NHAV buoy 

 (Figure 3-1; Appendix C Table 1). A series of six-station transects were occupied, over 

 five surrounding sediment mounds (CLIS 87-88 complex, CLIS 89, CLIS 90, NORWALK, 



Monitoring Surveys of the New Haven Capping Project, 1993-1994 



