Toxicological and Bioaccumulation Testing of Dredged Material in Confined Disposal Facilities Using Plants and Worms

ERDC TN-DOER-C22

September 2001 (Replaced July 2002)

Toxicological and Bioaccumulation Testing

of Dredged Material in Confined Disposal

Facilities Using Plants and Worms

PURPOSE: Contaminants in dredged material of confined disposal facilities (CDFs) can move

from substrates into food webs because of their contact with CDF-colonizing or -inhabiting plants

and animals, and as such cause unacceptable risks outside the CDF. The primary goal of this

technical note is to provide guidance on how to determine exposure-based effects on index and other

species, and how to relate these effects to the fates of contaminants in food chains. The toxicity of

dredged material from CDFs and the bioaccumulation of contaminants from this material were

determined in test species. The plants Cyperus esculentus (yellow nutsedge) and Cynodon dactylon

(common bermudagrass) and the invertebrates Eisenia fetidan (earthworm) and Enchytraeus

crypticus (enchytraeid worm) were used as test organisms. At a later stage, exposure-based effects

evaluation and interpretive guidance will be provided for effective management of contaminants to

minimize unacceptable risks in CDFs and for beneficial use of dredged material projects.

BACKGROUND: Placement of dredged material in CDFs and its removal from CDFs for

beneficial use require assessment of environmental risk. To this end the Decision-Making Frame-

work and the U.S. Army Corps of Engineers (USACE)/U.S. Environmental Protection Agency

(USEPA) Technical Framework may require exposure and effects assessments of relevant contami-

nant pathways prior to dredging to evaluate impacts on plants and animals in cases where terrestrial

placement is selected as a disposal alternative, and there is a reason to believe that the dredged

material is unacceptably contaminated. Currently no specific guidelines for contaminant residues

in plants and animals exist. Moreover, risk assessment based on assessments performed on index

species may not necessarily give an accurate indication of the fate and effects of the contaminants

because the index species may have little relevance to those species inhabiting CDFs or species

found where the dredged material can be put to a beneficial use.

INTRODUCTION: USACE annually manages about 300 million cu m of dredged material. The

traditional placement of 5 to 10 percent of material, contaminated enough to require special

handling, into CDFs is rapidly becoming problematic because most CDFs are at or approaching

their design capacity. USACE Districts are working together with Federal and State Agencies to

develop tools that help integrate topical quantitative information to yield quantifiable estimates of

risk posed by dredged materials including uncertainty (Moore, Bridges and Cura 1998). The use of

effects-based testing and risk assessment is intended to supplement the analytical options currently

available to dredged material managers by building on the existing technical framework

(USEPA/USACE 1992) and the existing tiered approaches (USEPA/USACE 1991, 1998). How-

ever, even after these tools have become available and linked to databases regarding various aspects

of ecotoxicology of dredged material, the data pertinent to upland CDFs remain extremely limited

because of the unique characteristics of these materials. Standardized and dependable assessments

pertaining to relevant biota are needed for credible risk management.