53_ 



extreme western (RR-7) and eastern (RR-21) reaches of the area, and in predominantly 

 sandy sediments. In fact, concentrations were often so high as to be above the upper 

 screening unit. The presence of Clostridium in all of the areas suggested that there are 

 other historical or modem sources of sewage (e.g., residential), or that the effluent from 

 the sewage treatment plant is well mixed throughout the esmary. These preliminary results 

 indicated that Clostridium would not provide a good tracer for the Portland Disposal Site 

 Capping Demonstration Project, and therefore was not pursued. 



4.1.2.2 Coarse Fraction 



The most common components of the coarse fraction ( > 500 /zm) were wood, plant, 

 and shell fragments, sand and gravel, as well as carbonized wood (wood that has been 

 replaced by carbon in a reducing environment; Table 4-1). A material similar to the 

 carbonized wood has also been described as charcoal, and attributed to the influx of burned 

 material from burning and clearing of woodlands during colonial times (Belknap et al. 

 1989). The presence of a charcoal unit also may be a remnant of industrial activity; 

 fragments of slag also were found in the coarse fraction samples. Preliminary analyses of 

 the coarse fraction provided no distinctive material that was isolated to a specific reach of 

 the river, and the most common components were present in most cores sampled. As a 

 result, the coarse fraction data were not considered useful as a tracer. 



4.1.2.3 Fine Fraction 



Two major components of the fine fraction (63 ju,m to 500 ^^m) were analyzed: the 

 mineralogical content, and the microfossil assemblages. As described in detail below, 

 analysis of the microfossil content indicated differences in the composition of the 

 microorganism populations; the presence and relative abundance of two informal groups of 

 microorganisms, foraminifera and thecamoebia, varied in sediment originating from the 

 different regions of the estuary. In addition, visual descriptions of the mineralogy of the 

 sediments also showed distinctions in the material originating from the upper and outer 

 reaches of the river. For both the mineralogical and microfossil data, the sediments from 

 the middle zone had traits similar to both the outer and upper river zones, suggesting a 

 blending of characteristics. As a result, we used both mineralogy and microfossils as 

 tracers of Royal River dredged material. 



Mineralogy. For the purposes of this report, the mineralogical composition of the 

 fine fraction was defined as the mineralogical and biological components remaining after 

 analysis of the microfossil (foraminifera and thecamoebia only) assemblages (Section 3.9). 

 The fine fraction of all Royal River sediment cores were composed mainly of quartz and 

 common micas (muscovite and biotite). The sediments also contained varying amounts of 

 shell fragments, smooth ostracods, and black porous material. This material appeared to 

 be small pieces of burnt organic matter, representative of coal or burnt wood. The 



The Portland Disposal Site Capping Demonstration Project, 1995-1997 



