Information Needs

Information Needs

The workgroup discussed the types of data necessary to conduct an exposure

assessment, the applicability of current dredged material management site

monitoring programs to fill these data needs, and the types of relevant data sources

available outside the dredged material management program. The workgroup

noted that the information needs for an exposure assessment are site- and project-

specific. It is not necessary to consider all possible exposures but only those that

appear reasonable within the context of protecting a specific organism or resource.

The group also noted that these data needs will vary between dispersive and

nondispersive sites.

With a clear sense of what should be protected, the collection of information

useful to exposure assessment can begin in Tier I of the sediment evaluation

procedures and early in the Site Designation Process for new sites. In moving

through the tiers, it would be helpful if operations personnel had a checklist of the

types of data that might be useful should a conceptual model and risk assessment

become necessary. The group did not attempt to provide guidance as to what

types of information might be needed under various site-specific conditions.

Rather, we attempted to list the larger set of data needs, recognizing that a given

site may require only a subset of these data categories.

There are three general categories of information useful in exposure

assessment: biological characteristics, physical-chemical properties of sediment

and surface water, and hydrodynamic characteristics. Again, consideration of a

basic question, "What are the receptors?" dominated the development of a list of

data needs. The important ecological receptors will be commercially important

species, threatened or endangered species, recreationally important species,

ecologically important species, and sensitive habitats.

Biological information needs. The group defined ecologically important

species as keystone species whose presence in a system maintains a particular

species composition, trophic structure, or physical environment. The sensitive

habitats may include: sediment or water column areas which are important

migratory routes, breeding grounds, or areas supporting sensitive life stages of a

receptor; wetlands; or submerged aquatic vegetation. Recreationally important

species are those which human populations use actively (e.g., a game fish

population) or passively (e.g., bird watching).

The group listed explicit receptor characteristics which should be understood to

develop an exposure assessment. These included: sensitive life stages; residence

time near the dredged material management site; a summary of population

dynamics; seasonal and annual variability in population abundance; a description

of feeding relations; weight and age classes; length of exposure; lipid content;

temporal and spatial scales of association with the dredged material management

site; foraging area; migration patterns; feeding type; areal distribution; habitat

requirements; and a description of the life cycle.

Chapter 2 Exposure Assessment Workgroup Summary