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seafloor. No single tracer was identified to reliably mark a specific reach of the Royal 

 River, but several parameters had relatively limited ranges so that an approach of using 

 multiple parameters was selected (Section 5.2.1). This approach showed statistical 

 reliability, but there were some discrepancies that may be attributed to dredging and 

 disposal operations (Section 5.2.2), as well as the presence of historical dredged material at 

 the site (Section 5.2.3). 



5.2.1 Evaluation of Estuary Tracers 



Detailed analysis of selected Royal River cores (original and additional cores) 

 indicated that two effective sets of tracers, micro fossils and mineralogical components in 

 the sediment, could be used to identify source material removed from the upper and outer 

 reaches of the river. From the overall set of components, there were several mineralogical 

 and biological components that were present in the upper/middle reaches and absent in the 

 outer reach (insect parts, plant fragments, pellets), and one that was present everywhere 

 except in the upper reach (fibrous minerals; Figure 5-3). Similarly, several biological 

 components (diatoms, ostracods, and bryozoans are included in biological components for 

 this discussion) were unique to a specific reach of the river. Diatoms (upper), smooth 

 ostracods (upper), and bryozoan fragments (outer) had ranges that did not overlap into the 

 middle reach, but the presence of these species were very rare. Thecamoebians were 

 present primarily in the upper and middle reaches, but one specimen also was noted in one 

 outer reach core (RR-12; Figure 5-3). Finally, the rare occurrence of shelf species in the 

 Royal River increased the uncertainty of the use of this tracer for ambient sediments. 



The Royal River data indicated two factors that were important in determining 

 sediment tracers that could be used to distinguish the upper and outer reaches. The first 

 was the coastal ecological zonations (Figure 2-7). Differences in species composition of the 

 microorganism populations corresponded to the contrasts between the freshwater habitat of 

 the upper river zone versus the brackish and saltwater envirormients of the middle and outer 

 zones. The distribution of the biological components was consistent with these zonations, 

 including the distribution of the diatoms, ostracods, and freshwater thecamoebians. The 

 primary exception was the limited (1-2 individuals/core) observation of shelf agglutinated 

 and calcareous foraminifera within the boundary between the upper and middle river 

 reaches (RR-6, RR-26, RR-18). The presence of plant and insect fragments in the upper 

 river reaches were also consistent with the upper river ecological zone. 



The second factor important in distinguishing the upper and outer reaches of the 

 estuary was the apparent relative hydrodynamic energy. The coarser grain size and 

 dominance of the fibrous minerals in the outer reach were indicative that the fme-grained 

 fraction was selectively removed. Because of tidal flushing within the river, identifying 

 localized constiments for tracers was problematic. Environmental tracers are useful only if 

 they are accurate indicators of the local, resident community and tend not to be transported 

 The Portland Disposal Site Capping Demonstration Project, 1995-1997 



