Sediment at REMOTS® grid stations off the dredged 

 material mound and at all reference stations consisted of very fine 

 sand-silt-clay (i.e., mud) (Figures 3-4, 3-5 and 3-10). This 

 sediment, having a grain size major mode in the range >4 to 3 phi, 

 presumably characterizes the ambient bottom unaffected by disposal. 

 It is possible that at some stations a fraction of this fine- 

 grained sediment represents material eroded from the disposal mound 

 which became deposited in areas of lower topography surrounding the 

 mound. Deposition and accretion of these fines would be enhanced 

 by the presence of extensive ampeliscid amphipod assemblages in the 

 area (Figure 3-11) ; dense amphipod tubes act like a series of 

 baffles projecting up from the bottom and serve as very effective 

 sediment traps. Cobble material located at stations East-1 and G-9 

 to the east of the center of the disposal site (Figures 3-4 and 3- 

 5) may be either naturally-occurring or the result of historic 

 disposal activity taking place away from the main dredged material 

 mound . 



The majority of small-scale surface boundary roughness 

 values at both grid stations and reference stations at the Brenton 

 Reef site fell within the range 0.08 to 1.8 cm (Figure 3-12). The 

 wider range in values at the grid stations (0.08 to 5.4 cm) was due 

 to the much larger sample size compared to the reference stations, 

 where values only ranged between 0.48 and 1.28 cm. There was no 

 statistically significant difference in the boundary roughness at 

 the grid stations (mean = 1.5 cm) versus that at the reference 

 stations (mean = 0.85 cm). Most of the small-scale surface 

 roughness was biogenic in origin, reflecting both extensive 

 sediment excavation by burrowing organisms and sediment accretion 

 around dense mats of amphipod tubes at many stations (Figure 3-11) . 

 It is possible that the foraging activities of fish feeding on the 

 amphipods also contributed to increased small-scale surface 

 boundary roughness at some stations. 



3.1.4 Benthic Community Structure 



A general characterization of biological conditions and 

 benthic community structure at the Brenton Reef site was possible 

 based on the results of the REMOTS® survey. For example, the 

 frequency distributions of mean apparent Redox Potential 

 Discontinuity (RPD) depths for the grid and reference stations were 

 both centered at the 5 cm class interval (Figure 3-13) . The values 

 of mean apparent RPD depth for the grid stations did not differ 

 significantly from those at the reference locations. Extensive 

 past DAMOS sampling in Long Island Sound has shown that RPD depths 

 greater than 3.5 cm are characteristic of relatively "healthy" 

 areas which have not experienced recent disturbance or stress 

 factors. Overall, RPD values at both the grid and reference 

 stations were well in excess of 3.5 cm, with values below this 

 threshold occurring only at a few random stations (Figure 3-14) . 



