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6.6 ROCKLAND DISPOSAL SITE 



6.6.1 Summary of RDS 



The Rockland Disposal Site (RDS) is located in the center of West Penobscot Bay 

 approximately 3.3 nmi northeast of the Rockland Harbor breakwater (Figure 6-38). The site 

 is a 0.5 nmi 2 with sides running true north-south and east-west, centered at 44°07.100' N 

 and 69°00.300' W. Water depths at RDS range from 65 to 80 m. The site is characterized 

 by a depression which is well-defined in the northern portion of the site, but widens and 

 shoals toward the south, completely losing its identity over the southern half of the site 

 (Figure 6-39). The ambient sediment consists of silty clays overlying a rocky glacial 

 substratum that outcrops in the southwest corner of the site. The current regime in this area 

 is influenced primarily by the strong, north-south tidal flow (SAIC 1988e). Current 

 velocities averaged 4-16 cm-s' 1 , with peak velocities of approximately 40 cm-s" 1 occurring 

 during the flood tide. The relatively short fetch and deep water at RDS restrict any possible 

 wave-induced erosion associated with major storm events (SAIC 1988a). 



RDS has virtually no commercial finfishing, and the nearest productive fishing 

 grounds are found outside of Penobscot Bay. Lobstering, which increases during the 

 summer months, is confined to water depths shallower (less than 20 m) than those located 

 within the disposal site. Due to the relatively clean nature of the sediments disposed at RDS, 

 finfish or benthic (seafloor) habitat contamination would not be expected from dredged 

 material disposal activities (SAIC 1988a). 



6.6.2 RDS: 1989 Monitoring Results 



Since 1984, SAIC has conducted two monitoring surveys at RDS (SAIC 1988e, 

 1992). These surveys, in May 1985 and June 1989, were designed to map the areal extent of 

 dredged material, assess the possible transport of dredged material during disposal 

 operations, and evaluate the response and subsequent recolonization of the benthic 

 environment. Assessment techniques included precision bathymetry, side-scan sonar, 

 sediment sampling, acoustic plume tracking, and REMOTS® sediment-profile photography 

 (SAIC 1990f). 



Although 374,099 m 3 of dredged material was deposited at RDS from February 1985 

 to June 1989 (Figure 6-40), no distinct, well-defined disposal mounds were detected by 

 bathymetric surveys in 1985 or 1989 (Figure 6-39). A depth difference calculation from the 

 1985 and 1989 bathymetric data revealed an elliptical mound southeast of the disposal buoy, 

 peaking at 1.3 m, and several small mounds less than 1.0 m in height (Figure 6-41). Due to 

 the minimal topographical changes resulting from disposal, side-scan sonar and REMOTS® 

 sediment-profile photography were used to determine the distribution of dredged material. In 

 each survey, dredged material was found up to 500 m from the disposal buoy (Figure 6-42). 



DAM OS Summary Report. 1985-1990 



