is 



3.0 METHODS 



SAIC conducted five monitoring surveys from September 1993 to March 1994: 

 1) baseline, 2) interim disposal, 3) precap, 4) interim cap, and 5) postcap (Figure 1-2) 

 (Table 1-2). In addition to the comprehensive dataset generated by the strategic repetition 

 of SAIC's survey activity, Ocean Surveys Incorporated conducted an interim cap survey in 

 January 1994 to fulfill a contract with the marine terminals involved in the dredging 

 project. Results of this survey are reported in Section 4. 1 .4. 



The SAIC Integrated Navigation and Data Acquisition System (INDAS) provided 

 the precision navigation required for all SAIC field operations. This system uses a 

 Hewlett-Packard 9920® series computer to collect position, depth, and time data for later 

 analysis, as well as provide real-time navigation. A Del Norte Microwave Trisponder® 

 System provided positioning to an accuracy of ±3 m. Shore stations were established in 

 Connecticut at known benchmarks at Stratford Point (41°09.112' N, 73°06.227' W) and 

 Lighthouse Point (41°14.931' N, 72°54.255' W). A detailed description of the navigation 

 system and its operation can be found in SAIC Report No. 290 (Murray and Selvitelli 

 1993). 



3.1 Precision Bathymetric Surveys 



The five precision bathymetric surveys that documented the stages of mound 

 development were all centered at 41°09.125' N, 72°53.450' W, and conducted over a 

 1600 m x 1600 m area. The surveys were oriented east to west using 25 m lane spacing 

 and requiring 65 lanes to fully cover the 2.56 km 2 area. An ODOM DF3200 Echotrac® 

 Survey Fathometer with a narrow-beam 208 kHz transducer measured individual depths to 

 a resolution of 3.0 cm (0.1 feet) as described in SAIC Report No. 290 (Murray and 

 Selvitelli 1993). Depth values transmitted to the computer were adjusted for transducer 

 depth. The acoustic records reliably detect changes in depth on the order of 20 cm due to 

 the accumulation of errors introduced by the positioning system, tidal corrections, the 

 calibration of the fathometer (speed of sound through the water column), the slope of the 

 bottom, and the vertical motion of the vessel. 



During each bathymetric survey, tidal variations at the disposal site were recorded 

 using a Seabird Instruments, Inc. SBE 26-03 Sea Gauge wave and tide recorder. Pressure 

 readings were collected at 6 minute intervals for the duration of the survey. After 

 conversion to water depths, the readings provided a constant record of tidal variations over 

 the survey area. The observed tidal data were later used to correct the bathymetric survey 

 data. 



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



