Section 611.1003  Source Water Monitoring Requirements:  Sampling Locations

a)         A supplier required to conduct source water monitoring under Section 611.1001 must collect samples for each plant that treats a surface water or groundwater under the direct influence of surface water source.  Where multiple plants draw water from the same influent, such as the same pipe or intake, the Agency may, by a SEP issued under Section 611.110, approve one set of monitoring results to be used to satisfy the requirements of Section 611.1001 for all of the plants.

b)         Source Water Sampling

1)         A supplier must collect source water samples prior to chemical treatment, such as coagulants, oxidants, and disinfectants, unless the supplier meets the condition of subsection (b)(2).

2)         The Agency may, by a SEP, approve a supplier to collect a source water sample after chemical treatment.  To grant this approval, the Agency must determine that collecting a sample prior to chemical treatment is not feasible for the supplier and that the chemical treatment is unlikely to have a significant adverse effect on the analysis of the sample.

c)         A supplier that recycles filter backwash water must collect source water samples prior to the point of filter backwash water addition.

d)         Bank Filtration

1)         A supplier that receives Cryptosporidium treatment credit for bank filtration under Section 611.743(b) or Section 611.955(c)(1), as applicable, must collect source water samples in the surface water prior to bank filtration.

2)         A supplier that uses bank filtration as pretreatment to a filtration plant must collect source water samples from the well (i.e., after bank filtration).  The use of bank filtration during monitoring must be consistent with routine operational practice.  A supplier collecting samples after a bank filtration process may not receive treatment credit for the bank filtration under Section 611.1017(c).

e)         Multiple Sources.  A supplier with plants that use multiple water sources, including multiple surface water sources and blended surface water and groundwater sources, must collect samples as specified in subsection (e)(1) or (e)(2).  The use of multiple sources during monitoring must be consistent with routine operational practice.

1)         If a sampling tap is available where the sources are combined prior to treatment, the supplier must collect samples from the tap.

2)         If a sampling tap where the sources are combined prior to treatment is not available, the supplier must collect samples at each source near the intake on the same day, and it must follow either of the following procedures for sample analysis:

A)        The supplier may composite samples from each source into one sample prior to analysis.  The volume of sample from each source must be weighted according to the proportion of the source in the total plant flow at the time the sample is collected; or

B)        The supplier may analyze samples from each source separately and calculate a weighted average of the analysis results for each sampling date.  The weighted average must be calculated by multiplying the analysis result for each source by the fraction the source contributed to total plant flow at the time the sample was collected and then summing these values.

f)         Additional Requirements.  A supplier must submit a description of its sampling locations to the Agency at the same time as the sampling schedule required under Section 611.1002.  This description must address the position of the sampling location in relation to the supplier's water sources and treatment processes, including pretreatment, points of chemical treatment, and filter backwash recycle.  If the Agency does not respond to a supplier regarding sampling locations, the supplier must sample at the reported locations.

BOARD NOTE:  Derived from 40 CFR 141.703.

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