Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 189

Loading/unloading of Great Lakes carriers Inadvertent spillage of DCR

Sweeping of DCR

Discharge of DCR to Great Lakes

Water column

Shading
Decreased
production

Nutrients
Increased
production

Contaminants
Toxicity
WQ criteria

Sediment

Algae
rooted aquatics

Algae
rooted aquatics

Fish
zooplankton

Enrichment
Sediment chemistry
WQ

Physical alteration
Colonization
community structure

Contaminants
Toxicity
bioaccumulation

Benthic production
pelagic animals

Benthic production
invasive species

Benthic invertebrates
food web

FIGURE 5.10
A DCR discharge impact prediction conceptual model for natural resources. Abbreviation:
WQ, water quality.

loading or unloading, residual cargo is spilled on the deck or in the hold of the
ship as indicated by the arrows in the figure, a series of events can be initiated
that could potentially reach an ecological receptor and produce an impact. The
sequence of events potentially resulting in an impact includes sweeping of the
DCR into the waters of the Great Lakes, DCR dispersed in the water column
and sediments, alteration of ecosystem attributes, and ultimately contact of
DCR with receptors (e.g., pelagic animals, invasive species, or the aquatic food
web). If all of the events in the series are completed, an impact will occur but
if any are constrained, the impact will be mitigated or eliminated. An objec-
tive of the EIS was to determine the likelihood of completion of the series of
events and the nature and extent of impact on the ecological receptors that
would result. Thus as discussed in Section 5.3.4, a series of investigations were
conducted to determine which of the steps in the impact prediction conceptual
model were realized, and if so, to what degree.

5.3.2 Impact Prediction Process

The process of predicting impacts or consequences of the proposed action
and alternatives for input to decisions is the stated object of environmental