way of predicting synergistic effects. 

 An underlying assumption is that 

 acute bioassays using "sensitive" 

 organisms (e.g., amphipods) will serve 

 as the marine equivalent of a canary in 

 a mine and detect these unanalyzed 

 "deleterious" unknown chemicals or 

 synergistic effects. 



Sources of Uncertainty: Not 

 surprisingly, there are several sources 

 for potential errors: 



a) Chronic effects by known, 

 measured contaminants, 

 unanalyzed contaminants, or 

 synergistic combinations are not 

 being assessed. Unfortunately, this 

 determination is beyond the 

 current state of our technology. 

 However, research is currently 

 underway to develop chronic 

 testing and evaluation methods to 

 fulfill the need for such a 

 determination. 



b) Bioaccumulation results are 

 acquired only for those 

 compounds/elements specified by 

 NED "in cooperation with other 

 Federal resource agencies" out of 

 the list provided in Table III of the 

 EPA/NED (1989) guidance 

 document (Appendix B); there is a 

 possibility that contaminants either 

 not on the list or selected (i.e. the 

 unknown contaminants) are 

 present in the organism. 



c) There is no way to equate 

 statistically significant 

 bioaccumulation (levels in test 

 organisms compared with 

 references) with real biological 

 harm; we do not know what the 



"normal" range of elements or 

 compounds tested are in natural 

 organisms, and levels can change 

 within the species with ontogeny 

 (lipid content, reproductive state, 

 etc). Unfortunately, there is no way 

 of judging the acceptability of any 

 baseline levels at this point 

 (Peddicord, 1984). 



d) Both bioassay and bioaccumulation 

 tests deal with a few selected 

 organisms under controlled 

 conditions; how these findings 

 relate to biological responses under 

 field conditions is not clearly 

 known. These test results are not 

 to be used to address unequivocally 

 any in situ effects, but rather to 

 answer the question of whether or 

 not the contaminants are 

 bioavailable. 



e) There is a potential for bioassay 

 results to have confounding 

 variables unrelated to contaminant 

 concentration affecting the final 

 results (e.g., different grain size or 

 organic carbon content between 

 dredging site and reference 

 sediment). 



f) Other than limited guidance in the 

 Green Book, there is no clear, 

 written information available for 

 interpreting bioassay or 

 bioaccumulation results. Because 

 there are replicate tests for at least 

 three species, it is quite likely as in 

 the bulk chemistry evaluations to 

 get "hits" in some categories and 

 not in others. It is once again up to 

 the best professional judgment of 

 the individual reviewers whether 

 they want to allow unconfined, 



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



