R 323.1203 Definitions; A to L.

(Effective July 29, 1997; revised January 13, 2006)

  Rule 1203.  As used in this part:

  (a)  "Acute-chronic ratio (ACR)" means a standard measure of the acute toxicity of a material divided by an appropriate measure of the chronic toxicity of the same material under comparable conditions.

  (b)  "Acute toxicity" means an adverse effect that results from an acute exposure which occurs within any short observation period and which usually does not constitute a substantial portion of the life span of the organism.

  (c)  "Acute toxic unit (TU_a)" means 100/LC₅₀ where the LC₅₀ is determined from a whole effluent toxicity (WET) test which produces a result that is statistically or graphically estimated to be lethal to 50% of the test organisms.

  (d)  "Aquatic life value" means a tier I or tier II value developed under R 323.1057(2).

  (e)  "Bioaccumulation equivalency factor (BEF)" means the bioaccumulation potential for the toxicologically important chlorinated dibenzo-p-dioxins and chlorinated dibenzo-p-furans relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) for use in calculating 2,3,7,8-TCDD toxicity equivalency concentrations in water as the 2,3,7,8-TCDD toxicity equivalency concentrations relate to deriving human health water quality values.

  (f)  "Bioaccumulation factor (BAF)" means the ratio, in liters per kilogram, of a substance's concentration in tissue of an aquatic organism to its concentration in the ambient water where both the organism and its food are exposed and the ratio does not change substantially over time.

  (g)  "Bioaccumulative chemical of concern (BCC)" means a chemical which, upon entering the surface waters, by itself or as its toxic transformation product, accumulates in aquatic organisms by a human health bioaccumulation factor (BAF) of more than 1000 derived after considering metabolism and other physiochemical properties that might enhance or inhibit bioaccumulation.  The human health bioaccumulation factor shall be derived according to

R 323.1057(5).  Chemicals with half-lives of less than 8 weeks in the water column, sediment, and biota are not BCCs.  The minimum BAF information needed to define an organic chemical as a BCC is either a field-measured BAF or a BAF derived using the biota-sediment accumulation factor (BSAF) methodology.  The minimum BAF information needed to define an inorganic chemical as a BCC, including an organometal, is either a field-measured BAF or a laboratory-measured bioconcentration factor (BCF).  The BCCs to which these rules apply are identified in table 5 of R 323.1057.

  (h)  "Bioconcentration factor (BCF)" means the ratio, in liters per kilogram, of a substance's concentration in tissue of an aquatic organism to its concentration in the ambient water in situations where the organism is exposed through the water only and the ratio does not change substantially over time.

  (i)  "Biota-sediment accumulation factor (BSAF)" means the ratio, in kilograms of organic carbon per kilogram of lipid, of a substance's lipid-normalized concentration in tissue of an aquatic organism to its organic carbon-normalized concentration in surface sediment in situations where the ratio does not change substantially over time, both the organism and its food are exposed, and the surface sediment is representative of average surface sediment in the vicinity of the organism.

  (j)  "Carcinogen" means a substance which causes an increased incidence of benign or malignant neoplasms in animals or humans or that substantially decreases the time in which neoplasms develop in animals or humans.

  (k)  "Chemical-specific water quality-based effluent limit" means water quality-based effluent limits that are based on an individual chemical.

  (l)  "Chronic toxicity" means a concurrent and delayed adverse effect that occurs only as a result of a chronic exposure.

  (m)  "Chronic toxic unit (TU_c)" means 100/MATC or 100/IC₂₅, where the maximum acceptable toxicant concentration (MATC) and IC₂₅ are expressed as a percent effluent in the test medium.

  (n)  "Clean water act" means the federal water pollution control act codified at 33 U.S.C. §1251 et seq., as amended.

  (o)  "Daily maximum water quality-based effluent limit" means an effluent specific water quality-based effluent limit in an NPDES permit developed to protect aquatic life from acute chemical specific or whole effluent toxicity.

  (p)  "Department" means the director of the Michigan department of environmental quality, or his or her designee to whom the director delegates a power or duty by written instrument.

  (q)  "Detection level" means the lowest concentration or amount of the target analyte that can be determined to be different from zero by a single measurement at a stated level of probability.

  (r)  "Discharge-induced mixing" means the mixing of a discharge and receiving water that occurs due to discharge momentum and buoyancy up to the point where mixing is controlled by ambient turbulence.

  (s)  "Dissolved metal" means the concentration of a metal that will pass through a 0.45-mm membrane filter.

  (t) "Existing discharge" means any building, structure, facility, or installation from which there is or may be a discharge of toxic substances to the surface waters of the state that is not a new discharge.

  (u)  "Final acute value (FAV)" means the level of a chemical or mixture of chemicals that does not allow the mortality or other specified response of aquatic organisms to exceed 50% when exposed for 96 hours, except where a shorter time period is appropriate for certain species.  The FAV shall be calculated under R 323.1057(2) if appropriate for the chemical.

  (v)  "Human cancer value (HCV)" means the maximum ambient water concentration of a substance at which a lifetime of exposure from either drinking the water, consuming fish from the water, and conducting water-related recreation activities or consuming fish from the water and conducting water-related recreation activities will represent a plausible upper bound risk of contracting cancer of 1 in 100,000 using the exposure assumptions and methodology specified in R 323.1057(4).

  (w)  "Human noncancer value (HNV)" means the maximum ambient water concentration of a substance at which adverse noncancer effects are not likely to occur in the human population from lifetime exposure through either drinking the water, consuming fish from the water, and conducting water-related recreation activities or consuming fish from the water and conducting water-related recreation activities using the exposure assumption and methodology in R 323.1057(4).

  (x)  "Intake toxic substance" means the amount of a toxic substance that is present in surface or groundwaters of the state at the time the toxic substance is withdrawn from the waters by the discharger or present in the water provided to the discharger by another facility.

  (y)  "Intermittent wet-weather point source" means a point source discharge that occurs as a result of a rainfall or snowmelt event.  An intermittent wet-weather point source includes a treated or untreated combined sewer overflow, but does not include a storm water discharge that is mixed with other industrial or commercial wastewater or an increased discharge from a municipal wastewater treatment plant due to a rainfall or snowmelt event.

  (z)  "IC₂₅" means the toxicant concentration that would cause a 25% reduction in a nonquantal biological measurement for the test population.

  (aa)  "LC₅₀" means a statistically or graphically estimated concentration that is expected to be lethal to 50% of a group of organisms under specified conditions.

  (bb)  "Load allocation" means the portion of a receiving water's loading capacity that is attributed to existing or future nonpoint sources, including natural background sources.

  (cc)  "Loading capacity" means the greatest amount of pollutant loading that a water can receive without violating water quality standards.

  (dd)  "Lotic" means surface waters of the state that exhibit flow.