Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 175

(if there was one) would define the area affected by the nutrient enrichment
and the intensity of the footprint would reveal the degree of enrichment. The
advantage of this method was that the sediments represented an integration
of processes that occurred over time as opposed to the one-time snapshot of
very dynamic water column processes and nutrients available from a limited
collection of water samples.
Once the sediments were identified as the focus of a creative investiga-
tion to understand the enriched dynamics of the affected environment, the
second approach to maximize efficiency came into play. A phased approach
was selected to investigate the sediments at various levels of detail at dif-
ferent special scales. The first phase was to tow a video camera on a sled
positioned just above the bottom over a large area (Figure 5.2) to visually
characterize the bottom with respect to deposition of organic matter. The
video camera could be towed at a speed of 1 to 3 knots so a very large area of
the bottom could be surveyed in just a few days. The resolution of the video
imaging was adequate to characterize the bottom type as:
r Definitively not an enriched area with sediment consisting of coarse
sand, gravel, boulders, or exposed bedrock
r Dein itely an en riched area with sediment consist i ng of black, h igh ly
organic, fine particles with bottom contours relatively even and flat
r Indeterminate areas with both enrichment and non-enrichment
characteristics.
The video camera provided a real-time feed to monitors on the research
vessel towing the sled. This allowed modification of the originally planned
coverage to fully define the limits of organically enriched sediment depo-
sition. It also allowed adjustments to the preplanned survey lines to best
define the boundaries between depositional and nondepositional areas.
The first phase video imaging was adequate to grossly define the vari-
ous offshore areas. Some, with coarse sediments were not subject to enrich-
ment effects and thus suitable for a wastewater discharge. Other areas were
already obviously enriched by the nutrients and organic matter discharged
from the North River and locating a wastewater discharge outfall in these
areas could exacerbate the problem. There were also areas where the exact
boundaries and intensity of enrichment were not apparent from the video
imaging alone and a second phase of investigation was necessary.
The second phase of the investigation was to deploy a sediment camera
(Figures 5.2 and 5.3) over a smaller area where the sediment characteris-
tics could not be fully determined by the towed video camera. The sediment
camera was capable of characterizing the sediment more precisely and in much
more detail than that achievable with the towed video camera. Deployment
of the sediment camera preempted the need and avoided the expenditure of
resources and time necessary to actually collect and process samples over the