Section 327IAC8-2-8.8. Monitoring requirements; systems that provide filtration treatment

  8. (a) A public water system that uses a surface water source or a ground water source under the influence of surface water and provides filtration treatment must monitor in accordance with this section beginning June 29, 1993, or when filtration is installed, whichever is later.

  (b) Turbidity measurements as required by section 8.5 of this rule must be performed on representative samples of the system’s filtered water every four (4) hours (or more frequently) that the system serves water to the public. A public water system may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous measurement for accuracy on a regular basis and obtains approval from the commissioner. For any systems using slow sand filtration, filtration treatment other than conventional treatment, direct filtration, or diatomaceous earth filtration, the commissioner may reduce the sampling frequency to once per day if he or she determines that less frequent monitoring is sufficient to indicate effective filtration performance. For systems serving five hundred (500) or fewer persons, the commissioner may reduce the turbidity sampling frequency to once per day, regardless of the type of filtration treatment used, if the commissioner determines that less frequent monitoring is sufficient to indicate effective filtration performance.

  (c) The residual disinfectant concentration of the water entering the distribution system must be monitored continuously, and the lowest value must be recorded each day, except that if there is a failure in the continuous monitoring equipment, grab sampling every four (4) hours may be conducted in lieu of continuous monitoring, but for no more than two (2) working days following the failure of the equipment, and systems serving three thousand three hundred (3,300) or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the frequencies each day prescribed as follows:

System size by population	Samples per day*
<500	1
501─1,000	2
1,001─2,500	3
2,501─3,300	4

*The day’s samples cannot be taken at the same time. The sampling intervals are subject to review and approval by the commissioner.

If at any time the residual disinfectant concentration falls below two-tenths (0.2) milligram per liter in a system using grab sampling in lieu of continuous monitoring, the system must take a grab sample every four (4) hours until the residual disinfectant concentration is equal to or greater than two-tenths (0.2) milligram per liter.

  (d) The residual disinfectant concentration must be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled, as specified in section 8 of this rule, except that the commissioner may allow a public water system which uses both a surface water source or a ground water source under direct influence of surface water, and a ground water source to take disinfectant residual samples at points other than the total coliform sampling points if the commissioner determines that such points are more representative of treated (disinfected) water quality within the distribution system. Heterotrophic bacteria, measured as heterotrophic plate count (HPC), as specified in section 8.7(3) of this rule, may be measured in lieu of residual disinfectant concentration.

  (e) If the commissioner determines, based on site-specific considerations, that a system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified in section 8.7(3) of this rule, and that the system is providing adequate disinfection in the distribution system, the requirements of subsection (d) do not apply to that system. (Water Pollution Control Division; 327 IAC 8-2-8.8; filed Dec 28, 1990, 5:10 p.m.: 14 IR 1026; filed Apr 12, 1993, 11:00 a.m.: 16 IR 2162)