EXECUTIVE SUMMARY 



Between October 1991 and June 1992, a capping project was conducted at the 

 Portland Disposal Site (PDS) as part of the Disposal Area Monitoring System (DAMOS) 

 Program. Fine-grained dredged material from the US Coast Guard project in South Portland 

 (13,270 m 3 ) was capped with cleaner fine-grained sediment from the same project 

 (19,451 m 3 ), as well as with sandy material from the Northeast Petroleum project 

 (18,310 m 3 ). 



Science Applications International Corporation (SAIC) conducted a monitoring cruise 

 at PDS in July 1992. The survey was designed to map the areal extent of dredged material 

 at the site, to determine the effectiveness of the capping operation, and to obtain sediment 

 chemistry data on the cap and at the reference areas. The field work included a REMOTS® 

 sediment-profile survey, a bathymetric survey, an acoustic sediment density study, and 

 sediment sampling for chemistry and grain size. 



Based on the REMOTS® survey, the areal extent of dredged material at PDS ranged 

 from 200 m west of the disposal buoy to 700 m southwest of the buoy location. The 

 bathymetric survey, when compared to the previous bathymetric survey in January 1989, 

 showed accumulations up to 0.75 m thick within 200 m of the buoy. The comparison of the 

 1989 and 1992 bathymetric surveys also indicated an area of accumulation 500 m south of 

 the buoy. This corresponded to the southernmost detection of dredged material from the 

 REMOTS® survey in an area that received dredged material after 1989. 



The acoustic sediment density survey showed that, in general, the coarser grained 

 sediment was concentrated in water depths shallower than 54 m, and the finer grained 

 sediment was concentrated in the deeper areas. The acoustic data were patchy and, after 

 smoothing, precluded identification of the project cap material. The patchiness was 

 attributed to both the heterogeneity of dredged material and the rapidly changing slopes in the 

 survey area. 



Sediment chemistry data from the surface of the cap showed that contaminant 

 concentrations were within the ranges measured at PDS reference areas, indicating that the 

 cap was effectively isolating contaminants. Two stations, F7 and H5, showed elevated levels 

 of several metals, although metal levels were overall within the range measured in samples 

 collected in the cap material prior to dredging. A comparison of the metal and polycyclic 

 aromatic hydrocarbon (PAH) baseline chemistry data from PDS reference areas and data 

 collected by the National Oceanographic and Atmospheric Administration (NOAA) National 

 Status and Trends (NS&T) Program for the Gulf of Maine showed that the PDS reference 

 areas were well within the ambient values for metals and PAHs in the area (NOAA 1991). 



