2.0 SURVEY METHODS 



2.1 Navigation 



Vessel positioning and data integration were achieved with SAIC's Portable 

 Integrated Navigation Survey System (PINSS) using a Magnavox 4200 GPS receiver. One 

 to 5-m DGPS accuracy was achieved to the GPS signals by applying corrections that were 

 acquired from the U.S. Coast Guard differential beacon located at Portsmouth, NH, using 

 a frequency of 288 kHz. During^ field operations, PINSS provided the navigator and vessel 

 operator with range and bearing to selected targets (i.e., beginning and end of survey 

 lines), signal quality, time of day, and selected data from environmental sensors including 

 the fathometer, subbottom towfish, and side-scan sonar. Core station and survey lane 

 positioning are discussed under the different survey operation descriptions below. 



2.2 Vibracore Survey 



2.2.1 Coring Operations 



Target locations for the cores were selected in order to meet the goals of the 

 monitoring survey. The primary goal was to collect cores in potential areas of concern as 

 suggested by results of several surface sediment samples collected in the area of the cell 

 (Shull and FitzGerald 1997), including the southern end and the edges of the cell. In 

 addition, bathy metric data collected during the various phases of the project were used to 

 identify areas of potentially thinner cap. Therefore, the cores were collected beginning 

 from the southern end of the cell, and moving to the central and northern end of the cell as 

 the day progressed. 



Long cores were collected with the goal of penetrating to the basement of the cell, 

 which consisted of Boston Blue Clay (BBC). With penetration into the BBC, a complete 

 stratigraphy (cap/dredged material/BBC) could be identified. The complete stratigraphy 

 was essential to determine if cap material had displaced dredged material during 

 operations. The final goal of core collection was to collect material to be used for 

 estimates of speed of sound in the layers of sediment detected by the subbottom data. 



The sediment vibracoring survey was conducted on 9 October 1997. Cores were 

 collected using a two-vessel operation. PINSS navigation software and the GPS antenna 

 was configured on a workboat supplied by Boston Line and Service Co., Boston, MA. 

 Cores were obtained using a crane off of a 40 ft barge that was lashed to the workboat, and 

 anchored in a 2-point configuration. Acmal core locations were calculated as a distance 

 and offset between the GPS antenna and the coring wireline. 



An Aqua Surveys Inc. (ASI) electric motor vibracorer was used to acquire sediment 

 core samples. The corer was deployed off of the barge using the crane, and lowered to the 



MONITORING RESULTS FROM THE FIRST BHNIP CONFINED AQUATIC DISPOSAL CELL 



