EXECUTIVE SUMMARY 



Sediments from the Royal River in Maine, considered suitable for open-ocean 

 disposal, were sequentially dredged and disposed at the Portland Disposal Site (PDS) as a 

 proof-of-concept that dredged material could be placed, and capped, in a deep water open- 

 ocean disposal site. Monitoring protocols developed through the Disposal Area 

 Monitoring (DAMOS) Program were utilized, as well as a newly developed tracer 

 technique to track different lithologies of dredged material on the seafloor. Overall, the 

 Portland Disposal Site Capping Demonstration Project showed that dredged material can be 

 effectively placed, capped, and monitored at a deep water disposal site. Recommendations 

 for improvements to the dredging and disposal operations, as well as to the monitoring 

 methods, are provided for future project considerations. 



Disposal and capping of dredged material is a management technique for the 

 containment of sediments considered unsuitable for open-ocean disposal (unacceptably 

 contaminated dredged material, or UDM) that has proven successful in Long Island Sound, 

 in relatively shallow water (approximately 20 m) and over a flat seafloor. Capping at deep 

 water disposal sites ( > 40 m) was an unproven management method due to a variety of 

 factors, including historical difficulties in disposal barge positioning, and shortage of 

 evidence confirming the formation of distinct UDM and capping layers. Refinement of 

 dredged material management techniques and the implementation of the differential Global 

 Positioning System (DGPS) during disposal and capping operations contributed to our 

 ability to form, and monitor, discrete mounds in deeper water. This tightly controlled, 

 closely monitored deep-water capping project has provided evidence that the technique can 

 be successful in deeper waters. 



In order to avoid any potential adverse environmental impact from such a 

 demonstration, material dredged from the Royal River, Yarmouth, ME, deemed suitable 

 for unconfined open-water disposal, was used as both "pseudo-UDM" as well as capping 

 dredged material (CDM). The capping demonstration was designed to identify reaches 

 (sections) of the Royal River project that were sufficiently distinct to permit identification 

 of source materials after disposal. Finer grained sediment removed from the upper reaches 

 of the river were designated as pseudo-UDM and placed as a discrete mound at PDS. 

 Material from the lower reaches of the river, characterized by coarser grained material, 

 was designated as the project CDM and was placed over the initial pseudo-UDM deposit as 

 a cap. The capped disposal mound was formed within a basin feamre on the PDS seafloor 

 at a depth of 64 m. After the completion of disposal and capping operations, the newly 

 formed mound was surveyed and cored to confirm the existence of two distinct layers. 

 This project design depended upon identifying characteristics of the reaches of the Royal 

 River that could be analyzed in samples collected after disposal. 



Based on die amount of dredged material disposed at the Royal River Project Area 

 (39,500 m3 pseudo-UDM and 22,200 m^ CDM), the DAMOS Capping Model predicted 



