Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 174

that data collection be focused on a narrow set of questions. Thus concise
questions were posed:
r How far offshore does the nutrient and organic loading from the
North Shore system enrich the nearshore environment?
r What level of increased loading, if any, can the nearshore environ-
ment accommodate without exceeding the assimilative capacity?
r How far offshore must a discharge be to prevent the nutrients and
organic matter associated with the discharge from being entrained
with the incoming tide and entering the North River and nearshore
systems?
Even with these concise questions, an efficient investigation design was
necessary to meet the schedule and resource limitations for the investiga-
tion. The question of entrainment with the incoming tide could be relatively
easily addressed by a series of current measurements over a full monthly
tidal cycle. When the measured tidal currents were input to a standard estu-
arine mathematical hydraulic model, the output adequately determined the
offshore “break point” where introduction of nutrients and organic matter
into the North River system was minimal.
The questions associated with the enrichment issues of the offshore affected
environment were not so easily addressed. For a classic research investigation,
the nutrient concentrations, plankton dynamics, and chemical reaction rates
would have been measured over at least a full calendar year in both the North
River and offshore areas. These measurements might even have been sup-
plemented with laboratory or in situ algal growth experiments to determine
the nutrient concentration's limiting growth. All of this information would
then form the input to a complex ecological model to determine the existing
relationship of nutrient concentrations, organic load, algal growth, dissolved
oxygen levels, deposition of carbon in the sediments, etc. Such an investiga-
tion would make a great master's thesis, but available resources and schedule
for the Scituate wastewater environmental impact analysis prevented such
a comprehensive investigation, and creativity was necessary to conduct an
affected environment investigation design to address the questions.
Two creative approaches were identified to design an affected environment
investigation to adequately address the critical enrichment questions and
complete the investigation within the resources and schedule available. The
first approach was to shorten the investigation to a “snapshot” rather than an
investigation of the dynamic seasonal characteristics of the system. Review
of the available literature (see Mandatory First Step, Section 5.2.2) and exten-
sive work on estuarine wastewater discharges and similar projects by mem-
bers of the environmental evaluation team with marine science expertise
revealed that nutrient and organic loading frequently left a “footprint” in
the sediment as the dense plankton growth resulting from enrichment died
and settled to the bottom. Thus delineation of the footprint in the sediment