Section 327 IAC 2-1-8.2 - Determination of acute aquatic criteria (AAC)Authority: IC 13-14-8; IC 13-14-9; IC 13-18-3
Affected: IC 13-18-4
Sec. 8.2.
In order to ensure that the concentration of a substance or combination of substances does not become acutely toxic to aquatic organisms, an acute aquatic criterion (AAC) will be determined by one (1) of the following methods:
(1) The following for Method 1: (A) If no AAC is available in section 6(a)(3), Table 6-1 of this rule, section 6(a)(3), Table 6-2 of this rule, or section 6(a)(5) of this rule, for the substance, an AAC can be calculated using the procedures in this subdivision.(B) An acute criterion can be calculated using modified U.S. EPA procedures when acute toxicity data are available for at least five (5) North American genera of freshwater organisms, including representatives of the following families:(i) The family Salmonidae.(ii) The family Cyprinidae or Centrarchidae.(iii) Another family, not represented in item (i) or (ii), in the Class Osteichthyes.(iv) The family Daphnidae.(v) Another aquatic macroinvertebrate family.(C) Resident species data are preferred for the required data set in clause (B). If one (1) or more of the required families are not a site resident, the requirement may be waived and appropriate substitution will be made. If data are not available for resident species, data for nonresident species may be substituted and will be assumed to be representative of resident species. The AAC is calculated using the following procedures: (i) If the acute toxicity of the chemical has not been adequately shown to be related to a water quality characteristic, such as hardness, pH, or temperature, the AAC is calculated using the following procedures: (AA) For each species for which at least one (1) acute value is available, the species mean acute value (SMAV) is calculated as the geometric mean of the results of all tests in which the concentrations of test material were stable as shown by measured values. For a species for which no such result is available, the SMAV should be calculated as the geometric mean of all available acute values, for example, results of flow-through tests in which the concentrations were not measured and results of static and renewal tests based on initial concentrations of test material.(BB) For each genus for which one (1) or more SMAVs are available, the genus mean acute value (GMAV) is calculated as the geometric mean of the SMAVs available for the genus.(CC) The GMAVs are ordered from high to low.(DD) Ranks (R) are assigned to the GMAVs from "1" for the lowest to "N" for the highest. If two (2) or more GMAVs are identical, successive ranks are arbitrarily assigned.(EE) The cumulative probability, P, is calculated for each GMAV as R/(N + 1).(FF) The (T) GMAVs (T = 2 for N = 5; T = 3 for N = 6 or 7; T = 4 for N = 8 or greater) are selected that have cumulative probabilities closest to five-hundredths (0.05). If there are fewer than fifty-nine (59) GMAVs, these will always be the two (2) (for N = 5), three (3) (for N = 6 or 7), or four (4) (for N = 8 or greater) lowest GMAVs.(GG) Using the selected GMAVs and Ps, the final acute value (FAV) is calculated as: (HH) If, for a commercially, recreationally, or ecologically important species, the geometric mean of the acute values from flow-through tests in which the concentrations of test material were measured is lower than the calculated FAV, then that geometric mean is used as the FAV instead of the calculated FAV.(ii) If data are available to show that acute toxicity to two (2) or more species is similarly related to a water quality characteristic, the AAC is calculated using the procedures as follows:(AA) For each species for which comparable acute toxicity values are available at two (2) or more different values of the water quality characteristic, a least squares regression of the acute toxicity values on the corresponding values of the water quality characteristic is performed to obtain the slope of the curve that describes the relationship. Because the best documented relationship is that between hardness and acute toxicity of metals and a log-log relationship fits these data, geometric means and natural logarithms of both toxicity and water quality are used in the rest of this procedure to illustrate the method. For relationships based on other water quality characteristics, such as pH or temperature, no transformation or a different transformation might fit the data better, and appropriate changes will be made as necessary throughout this method.(BB) Each acute slope is evaluated as to whether or not it is meaningful, taking into account the range and number of tested values of the water quality characteristic and the degree of agreement within and between species. If meaningful slopes are not available for at least one (1) fish and one (1) invertebrate, or if the available slopes are too dissimilar, or if too few data are available to adequately define the relationship between acute toxicity and the water quality characteristic, the AAC is calculated using the procedures in item (i).(CC) Individually, for each species, the geometric mean of the available acute values is calculated and then each of the acute values for a species is divided by the mean for the species. This normalizes the acute values so that the geometric mean of the normalized values for each species individually and for any combination of species is one (1.0).(DD) The values of the water quality characteristic are similarly normalized for each species individually.(EE) All the normalized data are treated as if they were for the same species and a least squares regression of all the normalized acute values on the corresponding normalized values of the water quality characteristic is performed to obtain the pooled acute slope, V.(FF) For each species the geometric mean, W, of the acute toxicity values and the geometric mean, X, of the water quality characteristic are calculated. (These were calculated in subitems (CC) through (DD).)(GG) For each species the logarithmic intercept, Y, is calculated using the equation:(HH) For each species calculate the SMAV at Z using the equation:(II) Obtain the FAV at Z by using the procedures described in subitems (BB) through (HH), replacing "value" with "intercept".(JJ) The final acute equation is written as: | Where: | V | = | pooled acute slope (from subitem (EE)) |
| A | = | FAV at Z (from subitem (II)) |
Since V, A, and Z are known, the FAV can be calculated for any selected value of the water quality characteristic.
(KK) The AAC is equal to the FAV/2.(D) If data are not available for at least five (5) North American freshwater genera meeting the requirements in clause (B), go to subdivision (2).(2) The following for Method 2: (A) If the required data to derive the AAC in subdivision (1)(C) are not present in the acute toxicity data base and at least one (1) LC50 value is available for a daphnid species and either fathead minnow, bluegill, or rainbow trout, an FAV is calculated by dividing the lowest SMAV for the daphnid species, fathead minnow, bluegill, and rainbow trout by five (5) if rainbow trout are represented or ten (10) if rainbow trout are not represented. The AAC equals the FAV divided by two (2). If appropriate, the AAC will be made a function of a water quality characteristic in a manner similar to that described in subdivision (1)(C)(ii).(B) If the data required in clause (A) are not available, no AAC can be calculated and the discharger will be required to develop the minimum data base (ninety-six (96) hour LC50 for rainbow trout, fathead minnow, or bluegill and a forty-eight (48) hour LC50 for a daphnid) needed to calculate the AAC.Water Pollution Control Board; 327 IAC 2-1-8.2; filed Feb 1, 1990, 4:30 p.m.: 13 IR 1033; errata filed Jul 6, 1990, 5:00 p.m.: 13 IR 2004; filed Jan 14, 1997, 12:00 p.m.: 20 IR 1357; errata filed Aug 11, 1997, 4:15 p.m.: 20 IR 3376; filed Feb 14, 2005, 10:05 a.m.: 28 IR 2056; filed Jul 9, 2012, 2:54 p.m.: 20120808-IR-327110320FRA