43_ 



the contaminants from the underlying material. A few measured non-normalized values fell 

 within the "moderate" or "high" values for Maine as defined by the NERBC (NERBC 1980) 

 at Stations F7 and H5. Plotting normalized values of three metals (Figures 3-11 through 3- 

 13) showed that the highest values are concentrated in the southeastern portion of the 

 surveyed area. Although the effect of normalization using a small value for the fine-grained 

 fraction at Station F7 contributes to the elevation of normalized metal concentrations there, 

 the elevation at that station and Station H5 warrants closer inspection. The variability of the 

 metals data could be a function of variability within the cap material itself, or of variability 

 within historical dredged material placed prior to the capping project at the 1984 buoy 

 location. Either of these hypotheses are possible; metal levels at F7 and H5 are within the 

 range of samples collected in the cap material except for As, Cr, and Ni. Because F7 and 

 H5 are not located near the center of disposal, however, it is possible that no project material 

 was placed at these stations and that the metals concentrations are a result of historical 

 disposal. It is unlikely that the samples were collected in uncapped Coast Guard material, 

 because in samples collected from Coast Guard material prior to dredging, the entire suite of 

 metals had much higher concentrations than measured in F7 and H5. As a reasonable 

 management precaution, however, additional sediment from future projects should be 

 directed to the 1984 buoy location where a small quantity (625 m 3 ) of contaminated material 

 may have been disposed. 



Monitoring Cruise at the Portland Disposal Site, July 1992 



