45 



substratum, the progression to a Stage 

 III community of deep-dwelling, 

 infaunal deposit-feeders may never 

 occur. If this is the case and one 

 blindly followed the flow chart, one 

 would be trapped in an endless loop 

 among boxes 3.6, 3.7, 3.10, and 3.11. 

 Clearly if the sand substratum persists 

 after the first year and results in an 

 anomalous recolonization pattern, one 

 would still progress to Box 3.12. 



If a sand cap is placed over a 

 contaminated mound in an area that is 

 predominantly a silt/clay bottom, it is 

 more likely that natural deposition of 

 detritus as well as the phenomena of 

 transport and deposition will slowly 

 change the surface layer of the cap 

 from a sand to a progressively 

 muddier substratum as time passes (as 

 observed in cores collected from the 

 STNH-N and Cap Site 2 mounds at the 

 Central Long Disposal Site). When this 

 occurs, the expected successional 

 sequence of change to a mature, 

 deposit-feeding community over time 

 still will be a valid prediction. 



Box 3.12 "Collect Surface Sediments 



and Infaunal Species for 

 Chemical Analyses " 



This is the first notable departure 

 from similarity with the monitoring 

 protocol outlined in the previous 

 section for unconfined open-water 

 disposal and constitutes the "next level 

 of assurance" for monitoring capped 

 disposal mounds. Even though 

 recolonization is proceeding normally 

 (indicating the lack of any apparent 

 toxic compounds in the sediment), this 

 step represents the next attempt to 

 verify that no contaminants are 



leaching through the cap. 



Separate sediment samples as well 

 as representatives of identical species 

 of indigenous fauna are collected from 

 the disposal mound and the reference 

 areas. Instead of assuming a particular 

 target species, the investigators will 

 determine the faunal dominant by 

 collecting sediment and sieving to find 

 out what are the dominant taxa. 

 Typically, either the polychaete 

 Nephtys incisa, any dominant large 

 bivalve, or one of the common 

 gammarid amphipods are collected in 

 sufficient quantity for tissue 

 contaminant analyses. 



Box 3.13 "Are Body Burden Levels 



Higher Than Those From 

 Reference Areas ? " 



Box 3.14 "Are Contaminant Levels 



Higher Than Time Zero 

 Levels?" 



Both Box 3.13 and 3.14 are dealt 

 with simultaneously at this point; the 

 numerical ordering of the boxes does 

 not indicate sequential collection or 

 analyses. Sufficient biomass of the 

 target species are frozen immediately 

 after collection and shipped to the 

 laboratory for analyses. The unstated 

 null hypotheses being tested regarding 

 tissue concentrations is: 



H 1: Infaunal tissue contaminant 

 levels are not higher on the 

 disposal mound than those on 

 the ambient seafloor. 



Surface sediments associated with 

 these organisms are obtained with a 

 grab for analysis. The same 



An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites 



