18 AAC 80.305. MCL compliance

(a) The department will determine MCL compliance based on analytical results and other information compiled by the department.

(b) The department will base compliance with the MCLs for inorganic chemicals listed in 18 AAC 80.300(b) (1) on the analytical result obtained at each sampling point specified in this chapter as follows:

(1) for a public water system monitoring two or more times each year, compliance with the MCLs for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium, and thallium is determined by a running annual average of all samples taken at each sampling point; if the average at any sampling point exceeds an MCL, the system is in violation of that MCL; if any one sample causes the annual average to be exceeded, the system is in violation of the MCL immediately; a sample below the method detection limit is calculated at zero for the purpose of determining the annual average; if a system fails to collect the required number of samples, compliance will be based on the average concentration in the total number of samples collected;

(2) for a public water system monitoring once each year or less often,

(A) the system is in violation of the MCL for a contaminant listed in (1) of this subsection if the level of a contaminant at any sampling point exceeds the MCL;

(B) if the department requires a confirmation sample for any contaminant listed in (1) of this subsection, the department will base compliance upon the average of the two samples; the confirmation sample must be collected at the same sampling point as soon as possible after the initial sample is taken and no more than 14 days after the initial sample is taken; and

(C) if a system fails to collect the required number of samples, the department will base compliance on the average concentration in the total number of samples collected;

(3) the department will base compliance with the MCLs for nitrate and nitrite on one sample if the levels of these contaminants are below the MCLs; if the levels of nitrate or nitrite exceed the MCLs in the initial sample, a confirmation sample is required, and compliance will be based on the average of the initial and confirmation samples; and

(4) on or after January 23, 2006, the public water system must report arsenic sampling results to the nearest 0.001 mg/l.

(c) The department will base compliance with the MCLs for the organic chemicals listed in 18 AAC 80.300(b) (2)(A), (B), and (D) upon the analytical results obtained at each sampling point as follows:

(1) for a public water system monitoring two or more times each year, compliance is determined by a running annual average of all samples taken at each sampling point; if the annual average for any sampling point exceeds the MCL, the system is in violation of the MCL; if the initial sample or a subsequent sample causes the annual average to be exceeded, the system is in violation of the MCL; a sample below the detection limit is calculated as zero in determining the annual average; and

(2) for a public water system monitoring once each year or less often, the system is in violation of the MCL if the level of a contaminant at any sampling point exceeds the MCL; if the department requires a confirmation sample, the department will base compliance upon on the average of two samples.

(d) The department will base compliance with the MCL for total trihalomethanes set out at 18 AAC 80.300(b) (2)(C)(i) upon a running annual average of quarterly samples collected by the owner or operator as required by 40 C.F.R. 141.30, adopted by reference in 18 AAC 80.010. The department will base compliance with the MCL for the disinfection byproducts set out at 18 AAC 80.300(b) (2)(C)(ii) upon a running annual arithmetic average, computed quarterly, of quarterly arithmetic averages of all samples collected by the owner or operator as required by 40 C.F.R. 141.133(b), adopted by reference in 18 AAC 80.010.

(e) The department will base compliance with the MCLs for turbidity set out in 18 AAC 80.300(b) (3) upon analytical results.

(f) Compliance with the MCL for radioactive contaminants set out in 18 AAC 80.300(b) (4) is achieved if the average of the analytical results of the four most recent consecutive quarterly samples, or the analytical result of a composite sample made up of the four most recent quarterly samples, does not exceed the MCL.

(g) Compliance with the MCLs for total coliform bacteria set out in 18 AAC 80.300(b) (5) will be determined as follows:

(1) the department will determine compliance with the MCL for coliforms for each month in which the owner or operator is required to monitor for coliforms, based on the results of all routine and repeat samples that the department does not invalidate under 18 AAC 80.425; and

(2) the department will count repeat samples toward the month in which the owner or operator collected the routine sample that required the repeat sampling, regardless of the month in which the owner or operator actually collected the repeat samples.

History: Eff. 10/1/99, Register 151; am 9/28/2001, Register 159; am 1/11/2004, Register 169; am 1/11/2006, Register 177

Authority: AS 46.03.020

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