Section 611.605  Nitrite Monitoring

Each supplier must monitor to determine compliance with the MCL for nitrite in Section 611.301.

a)         This subsection (a) corresponds with 40 CFR 141.23(e)(1), which was applicable only until a date now past.  This statement maintains consistency with USEPA rules.

b)         This subsection corresponds with 40 CFR 141.23(e)(2), a provision by which USEPA refers to state requirements that do not exist in Illinois. This statement maintains structural consistency with USEPA rules.

c)         Monitoring Frequency

1)         Quarterly Monitoring

A)        A supplier that has any one sample in which the concentration is equal to or greater than 50 percent of the MCL must initiate quarterly monitoring during the next quarter.

B)        A supplier required to begin quarterly monitoring under subsection (c)(1)(A) must continue on a quarterly basis for a minimum of one year following any one sample exceeding the 50 percent of the MCL, after which the supplier may discontinue quarterly monitoring under subsection (c)(2).

2)         The Agency must grant a SEP that allows a supplier to reduce its monitoring frequency to annually if it determines that the sampling point is reliably and consistently below the MCL.

A)        A request for a SEP must include the following minimal information:  the results from four quarterly samples.

B)        In issuing the SEP, the Agency must specify the level of the contaminant upon which the "reliably and consistently" determination was based.  All SEPs that allow less frequent monitoring based on an Agency "reliably and consistently" determination must include a condition requiring the supplier to resume quarterly monitoring for nitrite under subsection (c)(1) if it equals or exceeds 50 percent of the MCL specified by Section 611.301 for nitrite.

d)         A supplier that is monitoring annually must take samples during the quarters that previously resulted in the highest analytical result.

BOARD NOTE:  Derived from 40 CFR 141.23(e).

(Source:  Amended at 44 Ill. Reg. 6996, effective April 17, 2020)