Section 611.601  Monitoring Frequency

Monitoring must be conducted as follows:

a)         Required Sampling

1)         Each supplier must take a minimum of one sample at each sampling point at the times required by Section 611.610 beginning in the initial compliance period.

2)         Each sampling point must produce samples that are representative of the water from each source after treatment or from each treatment plant, as required by subsection (b).  The total number of sampling points must be representative of the water delivered to users throughout the PWS.

3)         The supplier must take each sample at the same sampling point unless conditions make another sampling point more representative of each source or treatment plant and the Agency has granted a SEP under subsection (b)(5).

b)         Sampling Points

1)         Sampling points for GWSs.  Unless otherwise provided by SEP, a GWS supplier must take at least one sample from each of the following points:  each entry point that is representative of each well after treatment.

2)         Sampling points for an SWS or a mixed system supplier.  Unless otherwise provided by SEP, an SWS or mixed system supplier must take at least one sample from each of the following points:

A)        Each entry point after the application of treatment; or

B)        A point in the distribution system that is representative of each source after treatment.

3)         If a supplier draws water from more than one source, and the sources are combined before distribution, the supplier must sample at an entry point during periods of normal operating conditions when water is representative of all sources being used.

4)         Additional sampling points.  The Agency must, by SEP, designate additional sampling points in the distribution system or at the consumer's tap if it determines that such samples are necessary to more accurately determine consumer exposure.

5)         Alternative sampling points.  The Agency must, by SEP, approve alternate sampling points if the supplier demonstrates that the points are more representative than the generally required point.

c)         This subsection corresponds with 40 CFR 141.23(a)(4), an optional provision relating to compositing of samples that USEPA does not require for state programs.  This statement maintains structural consistency with USEPA rules.

d)         The frequency of monitoring for the following contaminants must be in accordance with the following Sections:

1)         Asbestos:  Section 611.602;

2)         Antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, and thallium:  Section 611.603;

3)         Nitrate:  Section 611.604; and

4)         Nitrite:  Section 611.605.

BOARD NOTE:  Derived from 40 CFR 141.23(a) and (c).

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