59^ 



and therefore possibly were alive at the time of collection. Oxidation of the organic matrix 

 of foraminifera or thecamoebian shells will break apart the protein which holds the shell 

 together. In addition, agglutinated shells are not strong and do not maintain their integrity 

 long when subjected to mechanical transport. The state of namrally preserved 

 foraminiferal tests and ostracods (mineralogy) suggested that many individuals were 

 collected near their habitat range. 



4.2 Royal River Project Area August 1995 Baseline Survey 



The baseline survey conducted in August 1995, an 800 m x 800 m bathymetric 

 survey over the Royal River Project Area at PDS, was designed to serve as the basis for 

 comparison with all fumre investigations. The processed data yielded a chart of the 

 complex bottom topography in the southeast corner of the disposal site (Figure 4-3). 

 Depths ranged from 48 m along the northern survey margin to 72 m in the southwest 

 region of this 0.64 km^ survey area. A northwest-southeast trending trough, with an 

 average depth of 62 m, was selected as a suitable site to conduct the capping experiment. 

 The moderate relief at this site would maximize the potential for detecting bathymetric 

 changes and minimize the presence of survey artifacts common in regions with a rough, 

 irregular topography. In addition, a subtle basin feature within the trough was determined 

 to be advantageous for the development of a stable dredged material disposal mound 

 (Figure 4-3). 



The baseline bathymetric data were used to design the monitoring plan for the 

 capping project. The ridges surrounding the basin were predicted to serve as natural 

 containment measures, restricting the lateral spread of the dredged material disposal mound 

 (Figure 4-4). However, a narrow depression in the seafloor to the south of the disposal 

 basin was identified as a potential route for the downslope transport of sediments upon 

 initial deposition. In the event that dredged material was deposited greater than 100 m 

 southeast of the PDA buoy, or the angle of repose for the sediments composing the 

 southern flank of the disposal mound (estimated to be 4°) was exceeded, small volumes of 

 unconsolidated silts and clays were predicted to spread laterally through this passage. To 

 document the possibility of an expanded pseudo-UDM mound apron, the REMOTS® 

 sediment-profile photographic survey grid was designed to track the dredged material by 

 concentrating sampling efforts over likely paths of dredged material transport (Section 

 4.3.2). 



4.3 Expanded Royal River Project Area February 1996 Baseline Survey 



The bathymetry of the Royal River Project Area was re-surveyed because the 

 placement of 2,800 m^ of dredged material from the Harraseeket River at the project area 

 (Section 2.1) potentially would confound future interpretation of sequential bathymetric 

 surveys. In addition to the second baseline bathymetric survey, side-scan sonar and 



The Portland Disposal Site Capping Demonstration Project, 1995-1997 



