3.4.1 Need for Sediment Chemistry

Proper identification of COC is essential to accurate assessment of potential

impacts and the need for management actions. If an important constituent is not

included, the assessment could overlook potential effects. If an increasing number

of unimportant constituents are included, evaluations tend to lose focus, become

inefficient, and perhaps incorrectly identify potential effects where none actually

exist. While it is usually better to err on the side of inclusion, each potential COC

should be carefully considered, and constituents should not be included without

objective justification for doing so.

3.4.1 Need for Sediment Chemistry

If the available evidence indicates COC may be present, final selection of

COC may require supplementing available information with chemical analyses of

the sediment. Also, the Tier II evaluations for each pathway, if they are necessary,

rely on bulk sediment data for the proposed dredged material. If adequate bulk

sediment data are not available, samples should be collected and the bulk

sediment chemistry should be determined. It is possible to skip Tier II and go

directly to tests in higher tiers. However, this may not be an efficient use of

resources in most cases, since subsequent testing may be unnecessary. In addition,

proper interpretation of some pathway tests requires sediment chemistry data.

In some instances, it may be sufficient to perform confirmatory analyses for

specific COC. In other cases where the initial evaluation indicates that a variety

of COC may be present, chemical analysis of the dredged material could provide a

useful inventory, and bulk sediment chemistry analysis may be appropriate.

Should it be necessary to collect and analyze sediment samples at this point, it

should be assumed that Tier II and Tier III testing may be needed for all pathways.

Hence, consideration should be given to collecting sufficient material from the

dredging, reference, and control sites to conduct these tests. Careful attention

should be given to storage conditions and storage times for sediments prior to

performing evaluations. If this is not done, it may be necessary to repeat the

sampling.

3.4.2 Characteristics of Contaminants of Concern

Contaminants for which there are applicable standards should be identified as

a COC. COC include potentially toxic or bioaccumulative constituents and those

that may promote undesirable organisms or growth. Salt is always a potential

COC whenever dredged material from a saline waterway is placed in a CDF

where nonsaline or lower-salinity environments may be affected. Other potential

COC include those that might reasonably be expected to require management

actions if the dredged material in question were to be placed in the CDF. The

potential COC for each proposed action should be identified on the basis of the

following, keeping in mind appropriate analytical considerations:

Presence in the dredged material

Concentration in the dredged material relative to the concentration in the

reference material

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Chapter 3

Initial Evaluations