Section 327IAC2-1.5-12. Determination of Tier II aquatic life values

   (a) If all eight (8) minimum data requirements for calculating an FAV using Tier I under section 11 of this rule are not met, a secondary acute value (SAV) for the waters of the Great Lakes system shall be calculated for a chemical as follows:

(1) To calculate a SAV, the lowest GMAV in the database is divided by the secondary acute factor (SAF) (Table 12-1 in this section) corresponding to the number of satisfied minimum data requirements listed in the Tier I methodology (section 11(d)(2)(A) of this rule). (Requirements for definitions, data collection, and data review, contained in section 11(b), 11(c), and 11(e) of this rule, shall be applied to calculation of a SAV.) If all eight (8) minimum data requirements are satisfied, a Tier I criterion calculation may be possible. In order to calculate a SAV, the database must contain, at a minimum, a genus mean acute value (GMAV) for one (1) of the following three (3) genera in the family Daphnidae:

(A) Ceriodaphnia sp.

(B) Daphnia sp.

(C) Simocephalus sp.

(2) If appropriate, the SAV shall be made a function of a water quality characteristic in a manner similar to that described in the Tier I calculation procedure under section 11(f) of this rule.

  (b) If three (3) or more experimentally determined ACRs, meeting the data collection and review requirements of section 11(g) of this rule, are available for the chemical, determine the FACR using the procedure described in section 11(g) of this rule. If fewer than three (3) acceptable experimentally determined ACRs are available, use enough assumed ACRs of eighteen (18) so that the total number of ACRs equals three (3). Calculate the secondary acute-chronic ratio (SACR) as the geometric mean of the three (3) ACRs. Thus, if no experimentally determined ACRs are available, the SACR is eighteen (18).

  (c) Calculate the secondary chronic value (SCV) using one (1) of the following (if appropriate, the SCV will be made a function of a water quality characteristic in a manner similar to that described in the Tier I calculation procedure under section 11 of this rule):

(1) (use FAV from Tier I)

(2)

(3)

  (d) If for a commercially or recreationally important species of the Great Lakes system the geometric mean of the acute values or chronic values from flow-through tests in which the concentrations of the test materials were measured is lower than the calculated SAV or SCV, then that geometric mean must be used as the SAV or SCV instead of the calculated SAV or SCV.

  (e) A Tier II value shall consist of two (2) concentrations; the secondary maximum concentration (SMC) and the secondary continuous concentration (SCC) determined as follows:

(1) The SMC is equal to one-half (½) of the SAV.

(2) The SCC is equal to the lowest of the SCV or the final plant value, if available, unless other data (see section 11(j) of this rule) show that a lower value should be used. If toxicity is related to a water quality characteristic, the SCC is obtained from the secondary chronic equation or FPV, if available, that results in the lowest concentrations in the usual range of the water quality characteristic, unless other data (see section 11(j) of this rule) show that a lower value should be used.

(3) Round both the SMC and the SCC to two (2) significant digits.

(4) The Tier II value is stated as follows:

(A) The procedures described in the Tier II methodology indicate that, except possibly where a locally important species is very sensitive, aquatic organisms should not be affected unacceptably if the four (4) day average concentration of (insert name of material) does not exceed (insert the SCC) μg/L more than once every three (3) years on the average and if the one (1) hour average concentration does not exceed (insert the SMC) μg/L more than once every three (3) years on the average.

(B) As provided under section 11(k)(4)(B) of this rule, the commissioner has the discretion to specify alternative averaging periods or frequencies.

  (f) On the basis of all available pertinent laboratory and field information, determine if the Tier II value is consistent with sound scientific evidence. If it is not, another value, either higher or lower, shall be derived consistent with the procedures in this section.

  (g) The following table shall be used to determine secondary acute factors (SAFs):

Table 12-1
Secondary Acute Factors
Number of Minimum Data
Requirements Satisfied	Adjustment Factor
1	21.9
2	13.0
3	8.0
4	7.0
5	6.1
6	5.2
7	4.3

(Water Pollution Control Division; 327 IAC 2-1.5-12; filed Jan 14, 1997, 12:00 p.m.: 20 IR 1391)