3.4 Identification of Contaminants of Concern (COC)

Published scientific literature

Factors that may influence the movement of COC from sources to the dredged

material are important considerations, including:

Bathymetry

Water current patterns

Tributary flows

Watershed hydrology and land uses

Sediment and soil types

Sediment deposition rates

3.4 Identification of Contaminants of Concern

(COC)

This step in the Tier I evaluation identifies potential contaminants of concern

(COC) and determines whether they may present a potential environmental

problem. The evaluation in all tiers rests heavily upon proper identification of

COC. The process begins in Tier I with the identification of potential COC.

Tier I also begins the process, continued in Tier II, of narrowing the potential

COC to a more focused set of COC that warrants detailed evaluation and

documents the reasons others do not warrant further consideration. This will

result in a focused list of COC necessary and sufficient for a thorough assessment

of potential environmental problems associated with the proposed project.

Simple presence of a contaminant in the dredged material being evaluated is

not sufficient to include that contaminant as a potential COC. However, a

persistent and toxic chemical would be included. Some COC may occur in a

dredged material below their toxic levels, yet may be sufficiently bioavailable and

bioaccumulative that they present a potential problem to higher trophic levels.

Some dredged materials may contain no COC.

There may be some COC common to many dredged materials, but the set of

COC developed for one project will not necessarily be appropriate for another

project. The COC may be similar for some pathways and may be very different

for others. For example, the COC may be relatively similar for effluent and

runoff, but potentially volatile contaminants that might be COC for air may not be

COC for direct uptake. Salt can have major effects on water quality and terrestrial

and freshwater organisms. Therefore, if the dredged material is from a saline

waterway and may reach fresher surface or groundwater, salt should be considered

a potential COC for all pathways except air and plant or animal uptake, even

though salt is not, strictly speaking, a contaminant. COC should be developed for

each pathway and each project.

3-8

Chapter 3

Initial Evaluations