Review of Field Validation Studies
of Sediment Bioassays for the
Regulatory Evaluation of Dredged Material
PURPOSE: This technical note reviews published field validation studies of sediment bioassays
to recommend the design and conduct of such studies in the future. The primary impetus for this
review is to develop an approach for the validation of emerging chronic sublethal sediment toxicity
tests for the regulatory evaluation of dredged material.
BACKGROUND: The U.S. Army Corps of Engineers (USACE) has statutory authority for
evaluating the potential unacceptable, adverse impacts of dredged material disposal. Regulations
implementing Section 103 of the Marine Protection, Research, and Sanctuaries Act (PL 92-532)
state that "material shall be deemed environmentally acceptable for ocean dumping only when...no
significant undesirable effects will occur due either to chronic toxicity or to bioaccumulation...."
Similarly, regulations implementing Section 404(b) 1 of the Clean Water Act (PL 92-500) state that
"the permitting authority shall determine in writing the potential short-term or long-term effects of
a proposed discharge of dredged or fill material on the physical, chemical, and biological compo-
nents of the aquatic environment...."
Beginning in the late 1970's and early 1980's USACE in cooperation with the U.S. Environmental
Protection Agency (USEPA) developed an effects-based approach for the regulatory evaluation of
dredged material. Ultimately, two guidance manuals were produced, the Ocean Testing Manual
and the Inland Testing Manual (USEPA/USACE 1991 and 1998, respectively). The approach relied
on the use of sediment bioassays to determine the suitability of the material for aquatic disposal.
The bioassays implemented for the regulatory program included solid-phase (SP) bioassays to
predict the potential toxicity of the dredged material on benthic invertebrates at the disposal site and
suspended particulate phase (SPP) bioassays, also known as sediment elutriate tests, to evaluate
potential water column toxicity shortly after disposal outside the mixing zone. Both SP and SPP
bioassays focused on acute effects (e.g., typically 10 days for SP tests and 96 hours for SPP tests)
with survival as the primary end point. In addition to these acute benthic and water column toxicity
tests, tests to assess the bioaccumulation potential of sediment-associated contaminants were also
included in the regulatory program (USEPA/USACE 1991, 1998).
While the regulations governing the statutory authority of the Corps mandated consideration of
"chronic" and "long-term effects," the tools for evaluating those effects in sediment systems were
not adequately developed for regulatory implementation when guidance manuals were published
(USEPA/USACE 1991, 1998). USACE initiated research in the early 1990's under the Long-Term
Effects of Dredging Operations program to meet these technical and statutory requirements. This
research focused on the development of chronic sublethal toxicity tests. Tests developed under this
program included a 28-day test with the estuarine amphipod Leptocheirus plumulosus measuring
effects on survival, growth, and reproduction, and a 28-day test with the marine polychaete Neanthes
arenaceodentata measuring survival and growth (Emery et al. 1997; Gray et al. 1998; Dillon, Moore,