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2.0 METHODS 



Upon completion of the UDM and CDM placement activities during the 1995-1996 

 disposal seasons, the DAMOS Program with funding from the Navy, implemented the long- 

 term monitoring of the capped Seawolf Mound. The environmental monitoring surveys 

 presented in this report were performed in September 1997 and July 1998 order to document 

 cap integrity, disposal mound consolidation, and benthic recolonization over the Seawolf 

 Mound. 



Precision bathymetry and REMOTS® sediment-profile photography have been 

 employed as standard tools for tracking the placement of dredged material, examining long 

 term fate of individual sediment deposits, and assessing biological conditions over a disposal 

 mound relative to nearby reference areas. These methods were developed in the context of a 

 rigorous tiered monitoring approach (Germano et al. 1994). Sediment sampling (grab 

 sampling and vibracoring) also was utilized to examine benthic infaunal species diversity and 

 cap integrity, over the Seawolf Mound in the surveys conducted in September 1997 and July 

 1998 (Table 2-1). 



2.1 Bathymetry and Navigation 



2.1.1 1997 and 1998 Survey Activity 



During both the 1997 and 1998 field efforts, SAIC's Portable Integrated Navigation and 

 Survey System (PINSS) was used for precision navigation and data acquisition. This system 

 utilizes a Toshiba® 3200DX series computer to provide real-time navigation, as well as 

 collect position, depth, and time data for later analysis. In addition, PINSS provides a helm- 

 display and a project database, which stored planned bathymetric survey lines, as well as 

 multiple station locations to facilitate point sampling (i.e., REMOTS®, grabs, and cores). 



Positioning information for the field efforts over the Seawolf Mound was obtained via 

 differentially corrected Global Position System (DGPS) data in the horizontal control of North 

 American Datum of 1983 (NAD 83). In 1997, a Magnavox MX4200D GPS receiver was 

 used to provide real-time positioning while a Trimble 4000 GPS receiver was used during the 

 1998 field effort. In both instances, the GPS receivers were interfaced with a Leica MX41R 

 differential beacon receiver to improve the overall accuracy of the positioning data. Signals 

 broadcast from the U.S. Coast Guard differential beacon at Montauk Point, New York (293 

 kHz) were utilized for satellite corrections due to its geographic position relative to NLDS. 

 When merged with the satellite data, the correctors provide DGPS positions to an accuracy of 

 ±3 m with an update rate of 1 Hz. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



