EXECUTIVE SUMMARY 



The Cape Cod Canal serves as a major thoroughfare for recreational and 

 commercial vessels transiting Massachusetts waters. For this reason, maintenance 

 dredging of the east end of the Cape Cod Canal and improvement dredging of the 

 East Mooring Basin were conducted by the U.S. Army Corps of Engineers during the 

 spring of 1990. The fine grained sediments from these projects were released at the 

 Cape Cod Canal Disposal Site (CCDS) and the sandier material was sent to Springhill 

 Beach. The CCDS has been used periodically for similar dredging operations. The 

 objective of disposal at Springhill Beach was to create a small feeder berm. 



The optimal management of both sites required pre- and postdisposal 

 bathymetric surveys. These surveys were used to map the areal distribution of the 

 dredged material and measure changes in depth before and after disposal. In 

 addition, a REMOTS® sediment-profile photographic survey was conducted at CCDS 

 to map the dredged material below the resolution of the acoustic bathymetric survey 

 and assess the recolonization status of the historical disposal mound at the site. 



The fine grained material released at CCDS formed a mound 1.0 m in height 

 within a 300 m radius of the "CCD" disposal buoy. A comparison of pre- and 

 postdisposal bathymetry generated a volume difference of 21,823 m s (95% confidence 

 limits of 10,739 m 3 and 32,908 m s ). This agreed closely with the barge log volume 

 estimates of 15,296 m s . The REMOTS® survey, consisting of a 15 station east-west 

 transect over a historic disposal mound at CCDS, showed recolonization by Stage II 

 infauna near the mound center. No distinct dredged material layers were present 

 anywhere along the transect. However, the continued effect of dredged material 

 disposal was apparent at the center and eastern end of the survey while ambient 

 conditions existed at the western end. Scouring and winnowing were evident at 

 some stations near the mound center. 



The depth difference analysis at the Springhill site revealed four distinct 

 disposal mounds, ranging from 2.1 to 2.3 m in height. General shoaling and 

 redistribution of sediments around the area of the individual disposal mounds were 

 apparent. Barge disposal logs estimated 87,628 m 3 of material were deposited at the 

 Springhill site. Volume calculations showed an estimated 83,972 m 3 (95% confidence 

 limits of 67,736 and 98,208 m 3 ) of dredged material had accumulated, indicating that 

 barge log records for both the CCDS and Springhill sites were in good agreement 

 with the survey calculations. Additional bathymetric surveys after a period of time 

 (e.g., six months) could provide evidence as to whether or not the Springhill site is 

 serving as a feeder berm for the beach area. 



