1.0 INTRODUCTION 



1.1 Background 



Portland Harbor is being considered for maintenance dredging to remove the natural 

 accumulation of sediments from its channels and berths. The use of capping to isolate 

 dredged sediments may be needed in order to accomplish this or other projects, thus the 

 efficacy of capping at the Portland Disposal Site (PDS) needed to be demonstrated by the 

 New England Division (NED) of the U.S. Army Corps of Engineers. Capping has been 

 successfully used as a remediation technique at PDS (Wiley 1996) and at dredged material 

 disposal sites throughout Long Island Sound for nearly 20 years (SAIC 1995a). However, 

 approval for routine use of this technique at the greater depths of PDS would be facilitated 

 if a successful demonstration could be conducted. 



As a component of the Disposal Area Monitoring System (DAMOS) ,NED 

 managed two investigations at PDS during the Fall and Winter of 1995-1996 to 

 demonstrate that disposed dredged material could effectively be capped and isolated from 

 the environment by a layer of clean sediment. The two investigations, both conducted by 

 Science Applications International Corporation (SAIC), were the Capping Demonstration 

 Study (SAIC 1995b) and the Oceanographic Measurement Program. The objective of the 

 Capping Demonstration Study was to use uncontaminated sediments dredged from the 

 Royal River to create both a disposal mound and a cap, each composed of different 

 sediment types. If the cap material was placed over the mound successfully, without 

 mixing of the two sediment types, cap construction techniques would thus be demonstrated 

 in the relatively deep waters of PDS. In addition, the ability of the cap material to resist 

 resuspension and horizontal transport after placement also needed to be demonstrated at the 

 disposal site. To test this hypothesis, an Oceanographic Measurement Program was 

 designed and implemented by SAIC to acquire site-specific data on near-bottom currents 

 and resuspension of natural sediments at PDS to demonstrate cap stability through 

 winter/ spring storms. This report presents a summary of the results obtained from this 

 measurement program. 



1.2 Site Characteristics 



PDS is located approximately 13 km east of Cape Elizabeth in the western Gulf of 

 Maine (Figure 1-1). Originally used for dredged material disposal by the War Department 

 from 1943 to 1946, and by NED in 1979, PDS was designated by Region I EPA on 

 October 16, 1987, as an Ocean Disposal Site for harbor dredging projects throughout the 



Oceanographic Measurements at the Portland Disposal Site during Spring of 1996 



