Section 302.565  Determining the Lake Michigan Basin Chronic Aquatic Life Toxicity Criterion (LMCATC) or the Lake Michigan Basin Chronic Aquatic Life Toxicity Value (LMCATV)

a)         Determining Tier I LMCATC

1)         When chronic toxicity data are available for at least eight resident or indigenous species from eight different North American genera of freshwater organisms as specified in Section 302.553, a Tier I LMCATC is derived in the same manner as the FAV in Section 302.555 or 302.560 by substituting LMCATC for FAV or FAI, chronic for acute, SMCV (Species Mean Chronic Value) for SMAV, and GMCV (Genus Mean Chronic Value) for GMAV.

2)         If data are not available to meet the requirements of subsection (a), a Tier I LMCATC is calculated by dividing the FAV by the geometric mean of the acute-chronic ratios (ACRs) obtained from at least one species of aquatic animal from at least three different families provided that of the three species:

A)        At least one is a fish;

B)        At least one is an invertebrate; and

C)        At least one species is an acutely sensitive freshwater species if the other two are saltwater species.

3)         The acute-chronic ratio (ACR) for a species equals the acute toxicity concentration from data considered under Section 302.555 or 302.560, divided by the chronic toxicity concentration.

4)         If a resident or indigenous species whose presence is necessary to sustain commercial or recreational activities will not be protected by the calculated LMCATC, then the SMCV for that species is used as the CATC.

b)         Determining the Tier II LMCATV

1)         If all eight minimum data requirements for calculating an FCV using Tier I procedures are not met, or if there are not enough data for all three ACRs, a Tier II Lake Michigan Chronic Aquatic Life Toxicity Value must be calculated using a secondary acute chronic ratio (SACR) determined as follows:

A)        If fewer than three valid experimentally determined ACRs are available:

i)          Use sufficient ACRs of 18 so that the total number of ACRs equals three; and

ii)         Calculate the Secondary Acute-Chronic Ratio as the geometric mean of the three ACRs; or

B)        If no experimentally determined ACRs are available, the SACR is 18.

2)         Calculate the Tier II LMCATV using one of the following equations:

A)        Tier II LMCATV = FAV / SACR

B)        Tier II LMCATV = SAV / FACR

C)        Tier II LMCATV = SAV / SACR

Where:

the SAV equals 2 times the value of the Tier II LMAATV calculated in Section 302.563.

3)         If, for a commercially or recreationally important species, the SMCV is lower than the calculated Tier II LMCATV, then the SMCV must be used as the Tier II LMCATV.

(Source:  Amended at 47 Ill. Reg. 4437, effective March 23, 2023)