than CLIS, the successful development of capped disposal mounds within the boundaries of 

 MBDS, CADS, PDS, and RDS appears feasible (Morris 1996). In fact, capping operations 

 were conducted at PDS in 1992 and at the historic Boston Foul Ground (BFG) in 1983 

 (Wiley 1996). However, the limited data collected from these projects did not provide 

 sufficient assessment to implement subaqueous capping as a deep-water disposal technique. 



In the past, disposal and capping operations at deep water disposal sites ( > 40 m) 

 were complicated due to difficulties in disposal barge positioning, yielding a wider 

 dispersal pattern than anticipated, and the lack of a discrete UDM deposit (Wiley 1995). 

 In addition, concerns over the dissipation of fine-grained sediments in the water column 

 and shortage of evidence confirming the formation of two distinct disposal mound layers 

 (CDM over UDM) were obstacles to continued use of this management strategy (Dolin and 

 Pederson 1991). Refinement of dredged material management techniques and the 

 implementation of the differential Global Positioning System (DGPS) during disposal and 

 capping operations improved discrete mound development in deeper water. But only a 

 tightly controlled, closely monitored deep water capping project will provide insight to the 

 behavior of material on the seafloor. 



1.4 Deep- Water Capping at the Portland Disposal Site 



The Portland Disposal Site Capping Demonstration Project was initiated due to 

 renewed interest in subaqueous capping at the deep water PDS. As the northernmost ice- 

 free port on the eastern coast of North America, Portland Harbor is essential for the 

 survival and prosperity of northern Maine and the Canadian provinces of New Brunswick 

 and Quebec during the winter months. Over the years, this port has grown to support the 

 expanding industry and international trade, which now financially sustains the majority of 

 the Portland metropolitan area. As the largest port in the state of Maine, a total of 14 major 

 marine terminals have been established on the banks of the Fore River (Custom 1995; 

 Figure 1-3). 



Initial projections indicated that over 765,000 m^ of material will be excavated from 

 the bottom of Portland Harbor during the next federal dredging project. Although all but a 

 small portion of the federal material from the harbor has been classified as suitable for 

 unconfined open- water disposal, capping at deep-water sites such as PDS will still 

 potentially benefit fumre projects. The remaining small volume of material will not be 

 dredged. The management study for the project has included evaluation of the feasibility 

 of subaqueous capping of the Portland Harbor sediments at an open-water disposal site as a 

 valid, cost-effective, and envirormientally sound disposal method. 



The Portland Disposal Site lies approximately 13.16 km east of Dyer Point, Cape 

 Elizabeth, Maine (Figure 1-4). This 3.42 km^ DAMOS disposal site, centered at 

 43° 34. 100 'N, 70° 02.000 'W, is characterized by rough, irregular bottom topography 



The Portland Disposal Site Capping Demonstration Project, 1995-1997 



