5.0 CONCLUSIONS 



Dredged material deposited at CCDS occurred within a 300 m range of the 

 "CCD" buoy. A broad region of shoaling 100 m north of the buoy represented an 

 approximate dredged material thickness of 0.7 m. The maximum thickness of newly 

 deposited material, 1.0 m, was located 150 m southwest of the buoy. Based on 

 results of the pre- and postdisposal bathymetric analyses, an estimated 21,823 m 3 of 

 dredged material have accumulated at this site. 



Postdisposal bathymetry at the Springhill Beach Site revealed several mounds 

 where depths decreased as much as 2.3 m due to the disposal operations. Most of 

 these areas were located between four lanes (100 m) of the bathymetric survey grid. 

 Shoaling around the mounds showed a redistribution of sediments, which, given 

 sufficient time and exposure to the natural elements of waves and longshore 

 currents, could replenish the beach. This indicated that the Springhill Beach Site 

 indeed may serve as a feeder berm for the beach. Subsequent bathymetric surveys 

 could confirm this dispersal of the sediments from the existing mounds to the beach 



Volume calculations showed an estimated 82,972 m 3 of dredged material 

 accumulated at the Springhill Beach Site. Unlike the monitoring results from other 

 DAMOS sites, at both locations the barge log records were in agreement with the 

 volume difference calculations, falling within the calculated 95% confidence limits. 



A REMOTS® sediment-profile photographic survey was performed at the 

 historic CCDS mound to delineate the areal extent of the deposit and to assess the 

 benthic community recovery at this former disposal point. Records indicated that 

 228,735 and 4590 m s were deposited at this site in 1980 and 1986, respectively. A 

 clearly-defined dredged material layer was no longer distinguishable as much of this 

 sediment had been incorporated into the ambient sediments; however, the 

 distribution of dredged material could be mapped based on changes in grain size 

 along the transect. Ambient sediment conditions were apparent at the western end 

 of the transect, whereas the continued, although diminished, influence of dredged 

 material was apparent at the center and eastern portions of the transect. Definitive 

 OSI values could not be calculated for several stations (100W to 100E) due to shallow 

 REMOTS® camera penetrations. 



The minimum depth of the historical mound was 19.3 m. Studies from more 

 protected sites in Long Island Sound have shown that a dynamic equilibrium of 

 erosional and depositional forces can exist at 20 m water depths, above which the 

 effects of wind and waves can transport fine silts and sands (McCall, 1978). To 

 minimize potential scouring at CCDS, future disposal should be directed to the 

 flanks of the existing mound below 20 m water depth, or efforts should be made to 

 reduce the height-to-width ratio of future disposal mounds. Management decisions 

 at CCDS must consider whether such scouring and erosion are acceptable. If the 



Monitoring Cruise at the Cape Cod Canal Disposal Site and Springhill Beach Site 



