Florida Administrative Code › 62 - DEPARTMENT OF ENVIRONMENTAL PROTECTION › 62 - Departmental › Chapter 62-302 - SURFACE WATER QUALITY STANDARDS › Section 62-302.200 - Definitions

Current through Reg. 50, No. 138; July 16, 2024
As used in this chapter:
(1) "Acute toxicity" shall mean a
				concentration greater than one-third (1/3) of the amount lethal to 50% of the
				test organisms in 96 hours (96 hr LC50) for a species
				protective of the indigenous aquatic community for a substance not identified
				in paragraph  62-302.500(1)(c),
				F.A.C., or for mixtures of substances, including effluents.
(2) "Annual average flow" is the long-term
				harmonic mean flow of the receiving water, or an equivalent flow based on
				generally accepted scientific procedures in waters for which such a mean cannot
				be calculated. For waters for which flow records have been kept for at least
				the last three years, "long-term" shall mean the period of record. For all
				other waters, "long-term" shall mean three years (unless the Department finds
				the data from that period not representative of present flow conditions, based
				on evidence of land use or other changes affecting the flow) or the period of
				records sufficient to show a variation of flow of at least three orders of
				magnitude, whichever period is less. For nontidal portions of rivers and
				streams, the harmonic mean (Qhm) shall be calculated as
Qhm = n
				  ____________________________
1 + 1 + 1 + 1 + . . . + 1
Q1 Q2
				  Q3 Q4
				  Qn
in which each Q is an individual flow record and n is the
				  total number of records. In lakes and reservoirs, the annual average flow shall
				  be based on the hydraulic residence time, which shall be calculated according
				  to generally accepted scientific procedures, using the harmonic mean flows for
				  the inflow sources. In tidal estuaries and coastal systems or tidal portions of
				  rivers and streams, the annual average flow shall be determined using methods
				  described in EPA publication no. 600/6-85/002b pages 142-227, incorporated by
				  reference in paragraph
				   62-4.246(9)(k),
				  F.A.C., or by other generally accepted scientific procedures, using the
				  harmonic mean flow for any freshwater inflow. If there are insufficient data to
				  determine the harmonic mean then the harmonic mean shall be estimated by
				  methods as set forth in the EPA publication
Technical Support Document
				  for Water Quality-Based Toxics Control
(March 1991), incorporated by
				  reference in paragraph
				   62-4.246(9)(d),
				  F.A.C., or other generally accepted scientific procedures. In situations with
				  seasonably variable effluent discharge rates, hold-and-release treatment
				  systems, and effluent-dominated sites, annual average flow shall mean modeling
				  techniques that calculate long-term average daily concentrations from long-term
				  individual daily flows and concentrations in accordance with generally accepted
				  scientific procedures.
(3)
				"Background" shall mean the condition of waters in the absence of the activity
				or discharge under consideration, based on the best scientific information
				available to the Department.
(4)
				"Biological Health Assessment" shall mean one of the following aquatic
				community-based biological evaluations: Stream Condition Index (SCI), Lake
				Vegetation Index (LVI), or Shannon-Weaver Diversity Index.
(5) "Chronic Toxicity."
(a) For a substance without an aquatic
				life-based criterion in Rule
				 62-302.530, F.A.C., and where
				chronic toxicity studies evaluating the toxicity of the substance are
				available, or for mixtures of substances, including effluents, chronic toxicity
				shall mean the concentration that equals or exceeds the
				IC25 on species protective of the indigenous aquatic
				community, or
(b) For a substance
				without an aquatic life-based criterion in Rule
				 62-302.530, F.A.C., and where
				chronic toxicity studies evaluating the toxicity of the substance on species
				protective of the indigenous aquatic community are not available, the chronic
				toxicity of a substance shall be established as a concentration greater than
				one-twentieth (1/20) of the amount lethal to 50% of the test organisms in 96
				hours (96 hr LC 50) for a species protective of the
				indigenous aquatic community.