mound consolidation can continue several months after disposal (Figure 4-1) 

 resulting in significant decreases (ca. 1.5 m) in mound height. Active disposal at the 

 "B" mound was occurring through May 1988, less than two months prior to the July 

 1988 survey. Consolidation of the "B" mound was likely still in progress at the time 

 of the 1988 survey. Further consolidation of the mound could have occurred during 

 the two years prior to the 1990 bathymetric survey and would contribute to the 

 observed decrease in the mound height. 



Another factor affecting mound height stems from the limitations of 

 bathymetric analysis on steep slopes and the resulting variability of recorded depths 

 in consecutive bathymetric surveys. Smooth topographies minimize the effect of the 

 ship's position on the recorded depth (Figure 4-2). However, the WLIS mounds have 

 some of the steepest slopes of all mounds studied under the DAMOS monitoring 

 program (see Table 4-1 in SAIC, 1988c). Examination of the bathymetric contour plot 

 (Figure 5-2) revealed a 1.75 m change in depth within a 25 m distance (equivalent to 

 the width of one bathymetric survey lane) along some regions of the WLIS "B" 

 mound. Examination of the raw navigation data records at the peak of the "B" 

 mound determined that the positions of the transducer during the 1990 and 1988 

 surveys were separated by approximately 11m, representing a possible 0.7 m 

 variation in recorded depth. Similar examination of raw navigation data at the "A" 

 and "C" mounds did not reflect the same substantial changes in depth; however, 

 changes of 0.25 m observed at WLIS "A" and "C could be expected given the 

 resolution limitations of the bathymetric instrumentation. 



Only one photograph was obtained from each reference station during the 

 1988 survey (13 total per reference area), whereas triplicate photographs were 

 analyzed during the 1990 survey (36 photos per reference area). This replication 

 demonstrated more clearly the within-station variability which continues to exist at 

 some stations (station W300S in the 2000W reference area, Figure 3-13). Some 

 stations within the WLIS-REF exhibited relic oxidized layers. Located at the eastern 

 edge of the WLIS Disposal Site and in proximity to the Eaton's Neck historic disposal 

 site, WLIS-REF probably received some sediments during disposal operations prior 

 to 1980. Relic oxidized layers at stations within the 2000S reference area reflected 

 more likely the effects of wind-driven currents and storm events. In conjunction 

 with dramatic increases in wind-driven current velocities (SAIC, 1988b), water depth 

 at 2000S is 25 m, implying that erosional and depositional forces could be at work 

 (McCall, 1978). Coarse-grained sediments and layering of sand and mud found 

 within the area supported evidence of winnowing away of the fine silt/ clay 

 components of the sediment. 



4 2 Recolonization Status 



An objective of the REMOTS® survey was to assess the impacts of dredged 

 material disposal on benthic recolonization. Although OSI values and RPD depths 

 differed significantly between the WLIS reference and on-site stations, a well- 



Monitoring Cruise at the Western Long Island Sound Disposal Site 



