(a) Applicability. All public water systems are subject to the requirements of this section.
  (1) Community and nontransient, noncommunity systems shall comply with the requirements of this section regarding monitoring, reporting, and maximum contaminant levels (MCLs) for all inorganic contaminants (IOCs) listed in this section.
  (2) Transient, noncommunity systems shall comply with the requirements of this section regarding monitoring, reporting, and MCL for nitrate and nitrite.
  (3) For purposes of this section, systems using groundwater under the direct influence of surface water shall meet the inorganic sampling requirements given for surface water systems.
(b) MCLs for IOCs. The MCLs for IOCs listed in the following table apply to community and nontransient, noncommunity water systems. The MCLs for nitrate, nitrite, and total nitrate and nitrite also apply to transient, noncommunity water systems.
Attached Graphic
(c) Monitoring requirements for IOCs. Public water systems shall monitor for IOCs at the locations specified by the executive director. All monitoring conducted under the requirements of this section must be conducted at sites designated in the public water system's monitoring plan. Each public water system shall monitor at the time designated during each compliance period.
  (1) Routine monitoring locations for IOCs except asbestos. Antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nitrate, nitrite, selenium, and thallium shall be monitored at each entry point to the distribution system.
    (A) If a system draws water from more than one source and the sources are combined before distribution, the system must sample at an entry point that is representative of all sources and during periods of normal operating conditions.
    (B) Systems shall take all subsequent samples at the same entry point to the distribution system unless the executive director determines that conditions make another entry point more representative of the source or treatment plant being monitored.
    (C) The executive director may approve the use of composite samples.
      (i) Compositing must be done in the laboratory or in the field by persons designated by the executive director.
      (ii) Compositing shall be allowed only at groundwater entry points to the distribution system.
      (iii) Compositing shall be allowed only within a single system. Samples from different systems shall not be included in a composite sample.
      (iv) No more than five individual samples shall be included in a composite sample.
      (v) The maximum number of individual samples allowed in a composite sample shall not exceed the number obtained by dividing the MCL for the contaminant by the detection limit of the analytical method and rounding the quotient to the next lowest integer. Detection limits for each analytical method are as listed in 40 Code of Federal Regulations (CFR) §141.23(a)(4)(i).
      (vi) If the concentration in the composite sample is greater than or equal to the proportional contribution of the MCL (e.g., 20% of MCL when five points are composited) for any inorganic chemical, then a follow-up sample must be collected from each sampling point included in the composite sample.
        (I) Follow-up samples must be collected within 14 days of receipt of the composite sample results.
        (II) If duplicates of the original sample taken from each entry point to the distribution system used in the composite are available, the system may use these instead of resampling. The duplicates must be analyzed within 14 days of the composite.
        (III) The follow-up or duplicate samples must be analyzed for the contaminant(s) which were excessive in the composite sample.
    (D) Initial monitoring for a new water source must be conducted at a site representative of the water quality of the new source of water. For systems with one well and one entry point, initial monitoring may be conducted at the entry point to the distribution system.
  (2) Monitoring locations for asbestos. Asbestos shall be monitored at locations where asbestos contamination is most likely to occur.
    (A) A system vulnerable to asbestos contamination due solely to source water shall sample at the entry point to the distribution system.
    (B) A system vulnerable to asbestos contamination due solely to corrosion of asbestos-cement pipe shall sample at a tap served by asbestos-cement pipe, under conditions where asbestos contamination is most likely to occur.
    (C) A system vulnerable to asbestos contamination due both to its source water supply and corrosion of asbestos-cement pipe shall sample at a tap served by asbestos-cement pipe, under conditions where asbestos contamination is most likely to occur.
    (D) The executive director may require additional sampling locations based on the size, length, age, and location of asbestos-cement pipe in the distribution system. The system must provide information regarding the size, length, age, and location of asbestos-cement pipe in the distribution system to the executive director upon request.
  (3) Initial monitoring frequency for IOCs except asbestos. Prior to using water as a drinking water source, public water systems shall monitor at the frequency determined by the executive director to ensure that the water distributed to customers will comply with the MCLs for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, nitrate, nitrite, nitrate and nitrite (total), mercury, selenium, and thallium.
  (4) Monitoring frequency for IOCs except asbestos, nitrate, and nitrite. Community and nontransient, noncommunity public water systems shall monitor for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium, and thallium at the following frequency.
    (A) Routine monitoring frequency. A public water system shall routinely monitor for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium, and thallium.
      (i) Each groundwater entry point shall be sampled once every three years.
      (ii) Each surface water entry point shall be sampled annually.
      (iii) Each of the sampling frequencies listed in this paragraph constitutes one round of sampling for groundwater and surface water entry points, respectively.
    (B) Reduced monitoring. The executive director may reduce the monitoring frequency for a system that has completed a minimum of three rounds of sampling by granting a waiver to the routine monitoring frequency for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium, and thallium.
      (i) Systems that use a new water source are not eligible for a waiver until three rounds of sampling from the new source have been completed.
      (ii) To be considered for a waiver, systems shall demonstrate that all previous analytical results at that sample site were less than the MCL.
      (iii) In determining the appropriate reduced monitoring frequency, the executive director shall consider:
        (I) the reported contaminant concentrations from all previous samples;
        (II) the degree of variation in reported concentrations; and
        (III) other factors that may affect contaminant concentrations such as changes in groundwater pumping rates, changes in the system's configuration, changes in the system's operating procedures, or changes in the flow or characteristics of a reservoir or stream used as the water source.
      (iv) If the executive director grants a waiver, it shall be made in writing and shall set forth the basis for the determination. The determination may be initiated by the executive director. The executive director shall review and, where appropriate, revise the waiver of monitoring frequency when other data relevant to the system becomes available.
      (v) The term during which the waiver is effective shall not exceed one compliance cycle (i.e., nine years).
      (vi) A system must take a minimum of one sample during each compliance cycle while the waiver is effective.
    (C) Increased monitoring. The executive director may increase the monitoring frequency for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium, or thallium.
      (i) If the results from a sample site exceed any of the MCLs in subsection (b) of this section, the system shall immediately begin quarterly sampling at that sample site starting in the next quarter after the exceedance occurs.
      (ii) After the initiation of quarterly monitoring, the executive director may return a system to the routine monitoring frequency if monitoring shows that the sampling site is reliably and consistently below the MCL.
Cont'd...