316 (a) Evaluations

February 22, 2012

Section 316 (a) of the Clean Water Act provides that thermal dischargers can be granted less stringent alternate thermal limits if they can demonstrate the current effluent limitations, based on water quality standards, are more stringent than necessary to protect the aquatic organisms in the receiving water body. Usually submitted in the form of a variance request, the 316(a) demonstration must document completely and comprehensively that alternate thermal effluent limitations will not adversely influence the balance of the indigenous aquatic community in the receiving water body, or on any other designated water use.  These demonstrations commonly take one of three forms:

  1. Demonstrating a lack of prior appreciable harm from the facility on aquatic resources based on field studies assessing impact of thermal discharge on indigenous aquatic communities.  (Normally requires an extensive pre-operational monitoring program).
    2. Protection of representative important species (RIS) which are designated by the reviewing agencies and, if protected, should assure the protection and propagation of the aquatic resources (predictive study based on modeling, literature review, field sampling).
    3. Biological, engineering, and other data (combination of type 1 and type 2).

EnviroScience has over 10 years of experienced in the design and implementation of thermal impact studies.  Many of these studies make use of the following 316 (a)-related services we offer:

  • evaluation of decision making criteria and subsequent development of a comprehensive study plan design to meet those criteria;
  • development of an appropriate Representative and Important Species (RIS) list using available data sources and infield data;
  • use of multi-metric biotic indices such as the Index of Biotic Integrity to assess community structure and function, as well as community responses to elevated temperatures;
  • use of thermal tolerance data, field sampling, and modeling results to determine protective thermal criteria


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