Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 177

entire study area. This camera penetrated the sediment-water interface, thus
allowing a detailed inspection of the sediment surface and also giving a wealth
of information of sediment characteristics at depth. Thus, a distinction could be
made regarding areas with just a thin surface of enriched sediment, which was
most likely transitory and organically rich sediments over depth indicative of
long-term and persistent enrichment.
Another advantage of the investigation method was that it was not neces-
sary to photograph every area that could not be characterized from the video
imagery. Where there were multiple areas with very similar appearance in
the video image but undetermined enrichment characteristics, only selected
areas had to be photographed with the sediment camera. A subset of areas
could be photographed and the interpretation of the results applied to areas
appearing similar in the video image.
The combined results of the video imaging and sediment camera pho-
tographs gave a precise demarcation of the offshore area of enrichment
(Figure 5.4). The results also gave a very good indication of the intensity of
enrichment based on the visual observation of in situ sediment pictures and
the depth of enriched sediments. From this information, the outfall loca-
tion that avoided enriching sediments beyond the assimilative capacity and
producing adverse impacts to the estuarine system could have been deter-
mined. However, since the treatment/discharge decision was nonreversible
and required a significant commitment of engineering, construction, and
operation resources, the stakeholders supported a final phase to confirm the

High energy
sandy sediments

Wastewater
treatment
plant

Rivermoor
Habitat
Park

Herring
River

Depositional
enriched
sediments

FIGURE 5.4
Scituate offshore affected environment.