Maximum Radionuclide Contaminant Levels and Monitoring Requirements

PURPOSE: This rule establishes maximum contaminant levels and monitoring requirements for radionuclides. PUBLISHER’S NOTE: The secretary of state has determined that the publication of the entire text of the material which is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. This material as incorporated by reference in this rule shall be maintained by the agency at its headquarters and shall be made available to the public for inspection and copying at no more than the actual cost of reproduction. This note applies only to the reference material. The entire text of the rule is printed here. (1) Maximum Contaminant Levels (MCL). (A) MCL for Combined Radium-226 and Radium-228. The maximum contaminant level for combined radium-226 and radium228 is five picocuries per liter (5 pCi/l). The combined radium-226 and radium-228 value is determined by the addition of the results of the analysis for radium-226 and the analysis for radium-228. (B) MCL for Gross Alpha Particle Activity (Excluding Radon and Uranium). The maximum contaminant level for gross alpha particle activity (including radium-226 but excluding radon and uranium) is fifteen picocuries per liter (15 pCi/l). (C) MCL for Beta Particle and Photon Radioactivity. 1. The average annual concentration of beta particle and photon radioactivity from man-made radionuclides in drinking water must not produce an annual dose equivalent to the total body or any internal organ greater than four (4) millirem/year (mrem/year). 2. Except for the radionuclides listed in Table A, the concentration of man-made radionuclides causing four (4) mrem total body or organ dose equivalents must be calculated on the basis of two (2) liter per day drinking water intake using the one hundred sixty-eight (168) hour data list in “Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure,” NBS (National Bureau of Standards) Handbook 69 as amended August 1963, U.S. Department of Commerce, which is incorporated by reference without any later amendments or modifications. If two (2) or more radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ shall not exceed four (4) mrem/year. Table A.—Average Annual Concentrations Assumed to Produce a Total Body or Organ Dose of Mrem/Year Radionuclide Critical Organ pCi per Liter Tritium Total body 20,000 Strontium-90 Bone Marrow 8 (D) MCL for Uranium. The maximum contaminant level for uranium is thirty micrograms per liter (30 μg/l). (E) Compliance Dates. Community water systems (CWSs) must comply with the MCLs listed in subsections (1)(A)–(D) of this rule. Compliance shall be determined in accordance with the requirements of 10 CSR 605.010 and section (2) of this rule. (2) Monitoring Frequency and Compliance Requirements for Radionuclides in Community Water Systems. (A) Monitoring and Compliance Requirements for Gross Alpha Particle Activity, Radium-226, Radium-228, and Uranium. 1. Community water systems must conduct initial monitoring to determine compliance with subsections (1)(A), (B) and (D) of this rule. For the purposes of monitoring for gross alpha particle activity, radium-226, and radium-228, the detection limits are: A. The detection limit for gross alpha particle activity is three (3) pCi/L; B. The detection limit for radium-226 is one (1) pCi/L; and C. The detection limit for radium-228 is one (1) pCi/L. 2. Applicability and sampling location for existing community water systems or sources. All existing CWSs using groundwater, surface water, or systems using both ground and surface water must sample at every entry point to the distribution system that is representative of all sources being used (hereafter called a sampling point) under normal operating conditions. The system must take each sample at the sample sampling point unless conditions make another sampling point more representative of each source. 3. Applicability and sampling location for new community water systems or sources. All new CWSs or CWSs that use a new source of water must begin to conduct initial monitoring for the new source within the first quarter after initiating use of the source. CWSs must conduct more frequent monitoring when ordered by the department in the event of possible contamination or when changes in the distribution system or treatment processes occur which may increase the concentration of radioactivity in finished water. 4. Initial monitoring for gross alpha particle activity, radium-226, radium-228, and uranium. A. For gross alpha particle activity, uranium, radium-226, and radium-228 monitoring, the department will waive the final two (2) quarters of initial monitoring for a sampling point if the results of the samples from the previous two (2) quarters are below the detection limit. B. If the average of the initial monitoring results for a sampling point is above the MCL, the system must collect and analyze quarterly samples at that sampling point until the system has results from four (4) consecutive quarters that are at or below the MCL, unless the system enters into another schedule as part of a formal compliance agreement with the department. 5. Reduced monitoring. Community water systems may reduce the future frequency of monitoring from once every three (3) years to once every six (6) or nine (9) years at each sampling point, based on the following criteria. A. If the average of the initial monitoring results for each contaminant (that is, gross alpha particle activity, uranium, radium-226, or radium-228) is below the detection limit specified in paragraph (2)(A)1. of this rule, the system must collect and analyze for that contaminant using at least one (1) sample at that sampling point every nine (9) years. B. For gross alpha particle activity and uranium, if the average of the initial monitoring results for each contaminant is at or above the detection limit but at or below onehalf (1/2) the MCL, the system must collect and analyze for that contaminant using at least one (1) sample at that sampling point every six (6) years. For combined radium226 and radium-228, the analytical results must be combined. If the average of the combined initial monitoring results for radium226 and radium-228 is at or above the detection limit but at or below one-half (1/2) the MCL, the system must collect and analyze for that contaminant using at least one (1) sample at that sampling point every six (6) years. C. For gross alpha particle activity and uranium, if the average of the initial monitoring results for each contaminant is above one-half (1/2) the MCL but at or below the MCL, the system must collect and analyze at least one (1) sample at that sampling point every three (3) years. For combined radium226 and radium-228, the analytical results must be combined. If the average of the combined initial monitoring results for radium226 and radium-228 is above one-half (1/2) the MCL but at or below the MCL, the system must collect and analyze at least one (1) sample at that sampling point every three (3) years. D. Systems must use the samples collected during the reduced monitoring period to determine the monitoring frequency for subsequent monitoring periods (for example, if a system’s sampling point is on a nine (9)- year monitoring period, and the sample result is above one-half (1/2) the MCL, then the next monitoring period for that sampling point is three (3) years). E. If a system has a monitoring result that exceeds the MCL while on reduced monitoring, the system must collect and analyze quarterly samples at that sampling point until the system has results from four (4) consecutive quarters that are below the MCL, unless the system enters into another schedule as part of a formal compliance agreement with the department. 6. Compositing. To fulfill quarterly monitoring requirements for gross alpha particle activity, radium-226, radium-228, or uranium, a system may composite up to four (4) consecutive quarterly samples from a single entry point if analysis is done within a year of the first sample. The department will treat analytical results from the composited as the average analytical result to determine compliance with the MCLs and the future monitoring frequency. If the analytical result from the composited sample is greater than one-half (1/2) the MCL, the department may direct the system to take additional quarterly samples before allowing the system to sample under a reduced monitoring schedule. 7. Gross alpha particle activity measurement. A. A gross alpha particle activity measurement may be substituted for the required radium-226 measurement provided that the measured gross alpha particle activity does not exceed five (5) pCi/L. A gross alpha particle activity measurement may be substituted for the required uranium measurement provided that the measured gross alpha particle activity does not exceed fifteen (15) pCi/L. B. The gross alpha measurement shall have a confidence interval of ninety-five percent (95%) (1.65s, where s is the standard deviation of the net counting rate of the sample) for radium-226 and uranium. When a system uses a gross alpha particle activity measurement in lieu of a radium-226 and/or uranium measurement, the gross alpha particle activity analytical result will be used to determine the future monitoring frequency for radium-226 and/or uranium. If the gross alpha particle activity result is less than detection, one-half (1/2) the detection limit will be used to determine compliance and the future monitoring frequency. (B) Monitoring and Compliance Requirements for Beta Particle and Photon Radioactivity. To determine compliance with the maximum contaminant levels in subsection (1)(C) of this rule for beta particle and photon radioactivity, a system must monitor at a frequency as follows: 1. Community water systems (both surface and ground water) designated by the department as vulnerable must sample for beta particle and photon radioactivity. Systems must collect quarterly samples for beta emitters and annual samples for tritium and strontium-90 at each entry point to the distribution system (hereafter called a sampling point), beginning within one (1) quarter after being notified by the department. Systems already designated by the department must continue to sample until the department reviews and either reaffirms or removes the designation. A. If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity at a sampling point has a running annual average (computed quarterly) less than or equal to fifty (50) pCi/L (screening level), the department may reduce the frequency of monitoring at that sampling point to once every three (3) years. Systems must collect all samples required in paragraph (2)(B)1. of this rule during the reduced monitoring period. B. For systems in the vicinity of a nuclear facility, the department may allow the CWS to use environmental surveillance data collected by the nuclear facility in lieu of monitoring at the system’s entry point(s), where the department determines such data is applicable to the community water system. In the event that there is a release from a nuclear facility, systems, using surveillance data must begin monitoring at the community water system’s entry point(s) in accordance with paragraph (2)(B)1. of this rule. 2. Community water systems (both surface and ground water) designated by the department as using waters contaminated by effluents from nuclear facilities must sample for beta particle and photon radioactivity. Systems must collect quarterly samples for beta emitters and iodine-131 and annual samples for tritium and strontium-90 at each entry point to the distribution system (hereafter called a sampling point), beginning within one (1) quarter after being notified by the department. Systems already designated by the department as systems using waters contaminated by effluents from nuclear facilities shall continue to sample until the department reviews and either reaffirms or removes the designation. A. Quarterly monitoring for gross particle activity shall be based on the analysis of monthly samples or the analysis of a composite of three (3) monthly samples. The former is recommended. B. For iodine-131, a composite of five (5) consecutive daily samples shall be analyzed once each quarter. As ordered by the department, more frequent monitoring shall be conducted when iodine-131 is identified in the finished water. C. Annual monitoring for strontium90 and tritium shall be conducted by means of analysis of four (4) quarterly samples, or with department approval, a composite of samples collected in four (4) consecutive quarters. D. If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity at a sampling point has a running annual average (computed quarterly) less than or equal to fifteen (15) pCi/l, the department may reduce the frequency of monitoring at that sampling point to every three (3) years. Systems must collect all samples required in paragraph (2)(B)2. of this rule during the reduced monitoring period. E. For systems in the vicinity of a nuclear facility, the department may allow the CWSs to utilize environmental surveillance data collected by the nuclear facility in lieu of monitoring at the system’s entry point(s), where the department determines if such data is applicable to the water system. In the event that there is a release from a nuclear facility, systems using surveillance data must begin monitoring at the community water system’s entry point(s) in accordance with paragraph (2)(B)2. of this rule. 3. Community water systems designated by the department to monitor for beta particle and photon radioactivity shall not apply to the department for a waiver from the monitoring frequencies specified in paragraph (2)(B)1. or (2)(B)2. of this rule. 4. Community water systems may analyze for naturally occurring potassium-40 beta particle activity from the same or equivalent sample used for the gross beta particle activity analysis. Systems are allowed to subtract the potassium-40 beta particle activity value from the total gross beta particle activity value to determine if the screening level is exceeded. The potassium-40 beta particle activity must be calculated by multiplying elemental potassium concentrations (in mg/l) by a factor of 0.82. 5. If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity exceeds the screening level, an analysis of the sample must be performed to identify the major radioactive constituents present in the sample and the appropriate doses must be calculated and summed to determine compliance with paragraph (1)(C)1., using the formula in paragraph (1)(C)2. Doses must also be calculated and combined for measured levels of tritium and strontium to determine compliance. 6. Systems must monitor monthly at the sampling point(s) which exceed the maximum contaminant level in subsection (1)(C) beginning the month after the exceedance occurs. Systems must continue monthly monitoring until the system has established, by a rolling average of three (3) monthly samples, that the MCL is being met. Systems who establish that the MCL is being met must return to quarterly monitoring until they meet the requirements set forth in subparagraph (2)(B)1.B. or subparagraph (2)(B)2.A of this rule. (C) General Monitoring and Compliance Requirements for Radionuclides. 1. The department may require more frequent monitoring than specified in subsections (2)(A) and (2)(B) of this rule, or may require confirmation samples at its discretion. The results of the initial and confirmation samples will be averaged for use in compliance determinations. 2. Each public water system shall monitor at the time designated by the department during each compliance period. 3. Compliance with subsections (1)(A)– (D) of this rule will be determined based on the analytical result(s) obtained at each sampling point. If one (1) sampling point is in violation of an MCL, the system is in violation of the MCL. A. For systems monitoring more than once per year, compliance with the MCL is determined by a running annual average at each sampling point. If the average of any sampling point is greater than the MCL, then the system is out of compliance with the MCL. B. For systems monitoring more than once per year, if any sample result will cause the running average to exceed the MCL at any sample point, the system is out of compliance with the MCL immediately. C. Systems must include all samples taken and analyzed under the provisions of this section in determining compliance, even if that number is greater than the minimum required. D. If a system does not collect all required samples when compliance is based on a running annual average of quarterly samples, compliance will be based on the running average of the samples collected. E. If a sample result is less than the detection limit, zero (0) will be used to calculate the annual average, unless a gross alpha particle activity is being used in lieu of radium-226 and/or uranium. If the gross alpha particle activity result is less than detection, one-half (1/2) the detection limit will be used to calculate the annual average. 4. The department has the discretion to delete results of obvious sampling or analytic errors. 5. If the MCL for radioactivity set forth in subsection (1)(A)–(D) of this rule is exceeded, the operator of a community water system must give notice to the department pursuant to 10 CSR 60-7.010 and to the public as required by 10 CSR 60-8.010. (3) Non-Community Water Systems. Noncommunity water systems must monitor for radionuclides as directed by the department. AUTHORITY: section 640.100, RSMo 2016.* Original rule filed May 4, 1979, effective Sept. 14, 1979. Amended: Filed April 14, 1981, effective Oct. 11, 1981. Rescinded and readopted: Filed Jan. 16, 2002, effective Nov. 30, 2002. Amended: Filed June 13, 2018, effective Feb. 28, 2019. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999, 2002, 2006, 2012, 2014.