Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 199

not always sufficient to maintain adequate water quality and healthy aquatic
ecosystems. Also the location of the discharge was in many cases as critical
as the level of treatment, and the mandate for secondary treatment did not
address the discharge location issue.
With a program of this financial magnitude, participation by potentially
every municipality in the United States, and potential effects on the nation's
aquatic resources, EPA saw a need for additional science-based criteria in
conjunction with a secondary treatment and water quality standards to
guide the spending of over a quarter of a trillion dollars of public funds.
Specifically the agency identified the need for guidelines, or impact sig-
nificance criteria, to establish the need for treatment beyond secondary and
identifying discharge locations compatible with the goals of fishable swim-
mable waters without unnecessary sewage treatment and effluent outfall
construction costs. Part of EPA's program to establish guidance in impact
significance criteria was to address the multiple related questions:

r How do estuarine systems respond to nutrient loading?
r What nutrient loading rates are beneficial, acceptable, and detrimen-
tal to the estuarine environment?
r How do estuarine systems respond to sewage solids loading?
r What loading rates of sewage solids are acceptable and detrimental
to the estuarine environment?

EPA funded research to address these questions. This was done by
developing impact significant criteria to assist in implementing municipal
wastewater treatment requirements mandated by the Clean Water Act and
maximizing the water quality and other environmental benefits achieved by
the $200 billion 201 Grant program.

One of the research programs EPA funded was at the Marine Ecosystem
Research Laboratory (MERL) at the Graduate School of Oceanography
(GSO), University of Rhode Island. MERL is a research facility envisioned
and funded jointly by GSO, the EPA, and other government agencies located
on the combined National Oceanographic and Atmospheric Administration,
GSO, and EPA Estuarine Laboratory complex on Narragansett Bay. The
charter of MERL was to research the effects of human perturbations with
a goal of providing scientific input to support sound, efficient, and effec-
tive environmental regulations, enforcement, and investments. In terms of
environmental impact analysis terminology, MERL's mission was to develop
environmental impact significance criteria.
MERL is a series of 14 identical large-scale tanks that simulate conditions
in a mid to northern North American Atlantic estuary, using the adjacent
Narragansett Bay as a template (Pilson et al. 1979). Each tank is a mesocosm
with all the components of an estuarine ecosystem (Figure 5.13), the forcing
functions (e.g., mixing, temperature, exchange rate, depth, controlled, and

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