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diatoms did increase in abundance with depth in the pseudo-UDM cores. It is likely that 

 the pseudo-UDM grab and upper core samples were representative of material dredged 

 during the second phase of UDM that extended into the upper middle reach. Finally, 

 many of the CDM samples had components that were identified as only being in the upper 

 and middle reaches, including insect parts, pellets, and an average of 4% thecamoebians. 

 Again, this material was derived from the upper middle part of the River during the final 

 phases of the project. 



The presence of bryozoan fragments in the pseudo-UDM of two cores provided 

 evidence for intermixing of CDM, as the range of bryozoans was limited to the outer 

 reach. No bryozoan fragments were noted in the pseudo-UDM grab samples, but rare 

 fragments were observed above and below the CDM/pseudo-UDM interface in Core E. 

 The possible mechanisms for this include: mixing during the core retrieval and sampling 

 process; dismrbance of pseudo-UDM during CDM disposal; or possible sampling artifact 

 (pseudo-UDM sample was collected at the interface). Mixing during core retrieval was 

 likely for Core B, only half of which was sampled because the other half was waterlogged 

 and disturbed. Even though the CDM and pseudo-UDM layers were clear in the half 

 sampled, the presence of shelf foraminifera throughout was likely the result of mixing due 

 to core retrieval. 



Other discrepancies of unit classifications were considered to be the result of the 

 presence of historical dredged material. For example, the presence of shelf species in the 

 pseudo-UDM or freshwater thecamoebians in the ambient layer was investigated (Section 

 5.2.3). 



5.2.3 Differentiating Ambient from Historic Dredged Material 



The definition of the ambient sediment at the Royal River Survey Area must be 

 clarified prior to a discussion of the samples recovered from this material. For our 

 purposes, ambient sediment was defined as the native sediments of offshore Maine. There 

 was an additional component of material present at the survey area prior to the initiation of 

 the Royal River project. This included dredged material from the Harraseeket River 

 project, and historical dredged material present prior to the baseline survey. The baseline 

 REMOTS® survey, conducted after the Harraseeket River project but prior to the Royal 

 River project, indicated that dredged material was present in the survey area, most 

 prevalently towards the northwest (Figure 4-7). The presence of dredged material in the 

 project area hampered the interpretation of the ambient and pseudo-UDM interval of the 

 cores to some extent. Ambient sediment and historical dredged material share some 

 biological characteristics as a result of recolonization of benthic species, while both 

 historical and recent dredged material will have a fresh or brackish water species 

 component. 



The Portland Disposal Site Capping Demonstration Project, ] 995-1997 



