N.Y. Comp. Codes R. & Regs. tit. 10, § 5-1.51 – Maximum contaminant levels, maximum residual disinfectant levels and treatment technique requirements.

(a) The maximum contaminant levels, maximum residual disinfectant levels and treatment technique requirements are listed in section 5-1.52 tables 1 through 7 of this Subpart. In the case where an MCL, MRDL or treatment technique requirement is exceeded, notwithstanding anything to the contrary contained in section 5-1.12 of this Subpart, the supplier of water will take the necessary steps to comply with this section, to ensure the protection of the public health, including the undertaking of remedial feasibility studies and the installation of a suitable treatment process. Compliance with the MCLs, MRDLs and treatment technique requirements shall be determined by the procedures contained in section 5-1.52 tables 1 through 7 of this Subpart.
(b) The minimum monitoring requirements for each contaminant are listed in section 5-1.52 tables 8A through 12 and 15A of this Subpart, except for public water systems with fewer than 15 service connections and which serve fewer than 25 persons, where monitoring will be at State discretion. For this section, State discretion shall mean requiring monitoring when the State has reason to believe an MCL, MRDL or treatment technique requirement has been violated, the potential exists for an MCL, MRDL or treatment technique violation or a contaminant may present a risk to public health.
(c) Each system shall develop and implement a monitoring plan that includes all monitoring requirements specified in this Subpart. The system shall maintain the plan and make it available for inspection by the State and the general public. After review, the State may require changes in any plan elements. Failure to monitor in accordance with the monitoring plan is a monitoring violation. Systems may only use data collected in accordance with the monitoring plan to qualify for reduced monitoring. The monitoring plan shall include at least the following elements, as applicable:
1. (1) specific locations and schedules for collecting samples for all applicable parameters listed in section 5-1.42, section 5-1.43, tables 8A-12, 15 and 15A of section 5-1.52, section 5-1.61, and section 5-1.81 of this Subpart;
2. (2) how the system will calculate compliance with MCLs, MRDLs, and treatment techniques;
3. (3) if the system is a consecutive system, or it is providing water to a consecutive system, and has been approved for modified monitoring under the provisions of section 5-1.76 of this Subpart, the sampling plan must reflect the entire distribution system for any analytes approved for modified monitoring;
4. (4) consecutive ground water systems must define and implement a protocol for notifying the system from which they receive water of any total coliform positive samples so the source can be tested for fecal contamination, unless the wholesale ground water system provides four-log virus treatment at peak flow before or at the first customer as confirmed through process compliance monitoring.
5. (5) Disinfection byproduct monitoring.
  1. (i) The following requirements of this subdivision apply to community and nontransient noncommunity water systems that use or deliver water that has been treated with a primary or residual disinfectant other than ultraviolet light, provided they serve 15 or more service connections or serve 25 or more persons:
    1. (a) if a new community or nontransient noncommunity water system begins operation, or an existing community or nontransient noncommunity water system begins using a disinfectant other than ultraviolet light, the system shall consult with the State to identify compliance monitoring locations for disinfection byproducts to include in the system’s monitoring plan, consistent with the requirements in 40 CFR 141.601 and 141.602, and for new systems that need an Initial Distribution System Evaluation (IDSE), consistent with 40 CFR 141.605; and
    2. (b) if a community or nontransient noncommunity water system adds or removes compliance monitoring locations, the system shall identify additional locations by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of compliance monitoring locations have been identified, as specified in section 5-1.52 table 9A. Systems shall also provide the rationale for identifying the locations as having high levels of TTHM or HAA5.
  2. (ii) Systems shall revise monitoring plans to reflect changes in treatment, distribution system operations and layout (including new service areas), other factors that may affect TTHM or HAA5 formation or upon consultation with the State.
    1. (a) If a system changes monitoring locations, it shall replace existing compliance monitoring locations with the lowest LRAA with new locations that reflect the current distribution system locations with expected high TTHM or HAA5 levels.
    2. (b) The State may require modifications in the monitoring plan.
    3. (c) Surface water or GWUDI systems serving more than 3,300 people shall submit a copy of their modified monitoring plan to the State prior to the date they are required to comply with the revised monitoring plan.
  3. (iii) A system is in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating a LRAA if the system fails to monitor.
(d) The notification requirements for each contaminant are listed in section 5-1.52 table 13 of this Subpart.
(e) The CT values for inactivation of Giardia lamblia cysts by free chlorine at various pH and temperature levels are listed in section 5-1.52 tables 14A through 14F of this Subpart. The CT values for inactivation of Giardia lamblia cysts by chlorine dioxide and ozone at various temperature levels are listed in section 5-1.52 table 14G of this Subpart. The CT values for inactivation of Giardia lamblia cysts by chloramines at various temperature levels are listed in section 5-1.52 table 14H of this Subpart. The CT values for inactivation of Cryptosporidium by chlorine dioxide at various temperature levels are listed in section 5-1.52 table 14I of this Subpart. The CT values for inactivation of Cryptosporidium by ozone at various temperature levels are listed in section 5-1.52 table 14J of this Subpart. The UV doses for Cryptosporidium, Giardia lamblia, and virus inactivation credit are listed in section 5-1.52 table 14K of this Subpart.
(f) The alternative disinfection monitoring frequency requirements using grab samples instead of continuous chlorine concentration monitoring is listed in section 5-1.52 table 15 of this Subpart.
(g) Monitoring and reporting frequencies for specific contaminants may be established at State discretion whenever the State believes that a potential exists for an MCL or MRDL violation or a contaminant may present a risk to public health.
(h) Notwithstanding anything to the contrary in subdivision (a) of this section, the commissioner may recommend values lower than the MCL's if sufficient valid information based on commonly accepted scientific standards and principles demonstrates an increased public health concern. Within one year from the date of such recommendation, the State shall hold a public hearing regarding the justification for the lower value, and whether a new MCL is warranted.
(i) Notwithstanding anything to the contrary in section 5-1.52 table 3 of this Subpart, the commissioner may in specific cases except specific organic chemicals from the MCL's for general organic chemicals if the supplier of water can demonstrate that sufficient valid scientific information exists to show that the organic chemical does not pose an unreasonable risk to human health, the organic chemical is present at a level and under circumstances not indicative of contamination, and the cost of compliance is unreasonable in light of the risk to human health.
(j) Notwithstanding anything to the contrary in section 5-1.52 table 3 of this Subpart, the commissioner may, based on receipt and review of a justification submitted by the supplier of water, allow a higher MCL for a period of up to 60 days following application of a paint or lining to a potable water structure, if he determines that an unreasonable risk to human health does not exist.
(k) Notwithstanding anything to the contrary in section 5-1.52 table 3A of this Subpart, systems may increase residual disinfectant levels of chlorine or chloramines (but not chlorine dioxide) in the distribution system to a level and for a time necessary to protect public health, to address specific microbiological contamination problems caused by circumstances such as, but not limited to, distribution line breaks, storm run-off events, source water contamination events, or cross-connection events.
(l) A system that is installing granular activated carbon (GAC) or membrane technology to comply with the trihalomethane and haloacetic acid MCLs listed in section 5-1.52 table 3 of this Subpart may apply to the State for an extension of up to 24 months past the compliance dates for those MCLs. Systems must comply with any interim measures and schedules of compliance set by the State.
(m) Each public water system must certify annually in writing to the State that when Acrylamide and Epichlorohydrin are used in drinking water systems, the combination (or product) of dose and monomer level does not exceed the levels specified as follows:
Acrylamide = 0.05% dosed at 1 ppm (or equivalent)
Epichlorohydrin = 0.01% dosed at 20 ppm (or equivalent)
Certification can rely on manufacturers or third parties, as approved by the State.
(n) For microbiological analysis, a standard sample size of 100 milliliters shall be used.
1. (1) Systems required to conduct quarterly monitoring shall calculate compliance at the end of each quarter or earlier if the LRAA calculated based on fewer than four quarters of data would cause the MCL to be exceeded regardless of the monitoring results of subsequent quarters in accordance with table 3 of section 5-1.52 of this Subpart.
2. (2) Systems required to conduct monitoring at a frequency that is less than quarterly shall monitor in the calendar month identified in the monitoring plan developed under subdivision (c) of this section. Compliance calculations shall be made beginning with the first compliance sample taken after the compliance date.
(o) Disinfection byproduct monitoring.
The requirements of this subdivision apply to community and nontransient noncommunity water systems that use a primary or residual disinfectant other than ultraviolet light, or deliver water that has been treated with a primary or residual disinfectant other than ultraviolet light in accordance with monitoring requirements in table 9A of section 5-1.52 of this Subpart.
(p) A system implementing corrective actions to comply with the MCL for Perfluorooctanesulfonic acid (PFOS), Perfluorooctanoic acid (PFOA), and 1,4-dioxane listed in table 3 of section 5-1.52 of this Subpart may request that the State defer actions for determining MCL violations prescribed in table 3 of section 5-1.52 of this Subpart for up to 24 months past the effective date of the PFOS, PFOA or 1,4-dioxane MCL. The system shall make such requests in writing within 90 days of the effective date of such MCL. Requests shall document that a deferral period is necessary for a system to implement corrective actions to achieve compliance with the MCL for PFOS, PFOA or 1,4-dioxane and include a timeline with specific milestones for State review and approval. A public notice shall be distributed within 30 days of receiving notification from the State that a deferral has been granted. Systems operating with a deferral approved by the State shall comply with any interim monitoring, public notification or other conditions required by the State, including but not limited to a timeline for implementation of a corrective action plan. Deferrals granted under this subdivision may be renewed, upon request, for up to an additional 12 months if the system establishes to the satisfaction of the State that it is taking all practical steps to meet the corrective action plan on which the initial deferral was conditioned. Failure to meet any deferral conditions shall constitute a violation of this section and may result in immediate deferral revocation. Notice of revocation of a deferral shall will be issued in writing by the State.