Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 196

TABLE 5.2
Example Impact Signiicance Criteria Used in the U.S. Coast Guard DCR EIS

Area of Impact No Impact Insigniicant Impact Signiicant Impact

Sediment chemistry Chemical composition of DCR

below threshold effect levels or
reference area levels

Chemical composition of DCR
above threshold effect levels but
less than probable effect levels

Chemical composition of DCR above probable
effect levels

Sediment physical
structure

Grain size distribution of
sediment samples from DCR
discharge area similar to
reference areas

Grain size distribution of sediment
samples from DCR discharge area
different from reference areas but
benthic communities similar

Grain size distribution of sediment samples
from DCR discharge area different from
reference areas and benthic communities

DCR deposition rate DCR rate within the range of

natural deposition rate

Combined natural and DCR rate no
more than 10% greater than
maximum natural deposition rate

Combined natural and DCR rate greater than
10% maximum natural deposition rate

Water chemistry No predicted concentrations

greater than Great Lakes
Initiative (GLI) chronic values

Mixing zone (MZ) predicted
concentrations greater than GLI
chronic values but less than acute
values

MZ predicted concentrations greater than GLI
acute values or GLI chronic values exceeded
outside MZ

Nutrient enrichment No stimulation of algal growth

with exposure to 100% DCR
slurry

No stimulation of algal growth with
exposure to predicted DCR
concentrations

Greater than 10% stimulation with exposure to
predicted DCR concentrations