Section 611.609   Determining Compliance

Compliance with the MCLs of Section 611.300 or 611.301 (as appropriate) must be determined based on the analytical results obtained at each sampling point.

a)         For suppliers that monitor at a frequency greater than annual, compliance with the MCLs for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, or thallium is determined by a running annual average at each sampling point.

1)         If the average at any sampling point is greater than the MCL, then the supplier is out of compliance.

2)         If any one sample would cause the annual average to be exceeded, then the supplier is out of compliance immediately.

3)         Any sample below the method detection limit must be calculated at zero for the purpose of determining the annual average.

            BOARD NOTE:  The "method detection limit" is different from the "detection limit," as set forth in Section 611.600.  The "method detection limit" is the level of contaminant that can be determined by a particular method with a 95 percent degree of confidence, as determined by the method outlined in appendix B to 40 CFR 136, incorporated by reference at Section 611.102.

4)         If a system fails to collect the required number of samples, compliance (average concentration) will be based on the total number of samples collected.

b)         For suppliers that monitor annually or less frequently, compliance with the MCLs for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, or thallium is determined by the level of the contaminant at any sampling point. If confirmation samples are required by the Agency, the determination of compliance will be based on the average of the annual average of the initial MCL exceedance and any Agency-required confirmation samples.  If a supplier fails to collect the required number of samples, compliance (average concentration) will be based on the total number of samples collected.

c)         Compliance with the MCLs for nitrate and nitrite is determined based on one sample if the levels of these contaminants are below the MCLs.  If the levels of nitrate or nitrite in the initial sample exceed the MCLs, Section 611.606 requires confirmation sampling, and compliance is determined based on the average of the initial and confirmation samples.

d)         Arsenic sampling results must be reported to the nearest 0.001 mg/ℓ.

BOARD NOTE:  Derived from 40 CFR 141.23(i) (2014).

(Source:  Amended at 39 Ill. Reg. 15352, effective November 13, 2015)