PURPOSE: This rule establishes maximum contaminant levels, and sampling and monitoring requirements for radionuclides.

Editor’s Note: The secretary of state has determined that the publication of this rule in its entirety would be unduly cumbersome or expensive. The entire text of the material referenced has been filed with the secretary of state. This material may be found at the Office of the Secretary of State or at the headquarters of the agency and is available to any interested person at a cost established by state law.

1. (1) For radium-226, radium-228 and gross alpha particle radioactivity, the maximum contaminant level (MCL) shall be—

   1. (A) Combining radium-226 and radium- 228, five picocurie (5 pCi) per liter. A gross alpha particle activity measurement may be substituted for the required radium-226 and radium-228 analysis, but only if the measured gross alpha particle activity does not exceed five (5) pCi per liter at a confidence level of ninety-five percent (95%) (1.65 r where r is the standard deviation of the net counting rate of the sample). In localities where radium- 228 may be present in drinking water, radium-226 or radium-228 analyses, or both, will be required when the gross alpha particle activity exceeds two (2) pCi per liter;
   2. (B) Measuring gross alpha particle activity, including radium-226 but excluding radon and uranium, fifteen (15) pCi per liter. When the gross alpha particle activity exceeds five

2. (5) pCi per liter, the same or an equivalent sample must be analyzed for radium-226. If the concentration of radium-226 exceeds three (3) pCi per liter, the same or an equivalent sample shall be analyzed for radium- 228;

   1. (C) Taking samples from representative entry point(s) to the distribution system. In addition, when so ordered by the department, a community water system using two (2) or more sources must monitor each source of water; and
   2. (D) Basing each MCL on either an analysis of a composite of samples taken in four
3. (4) consecutive quarters, or the average of the analyses of four (4) samples obtained at quarterly intervals.

4. (2) Community water systems must conduct analyses at least once every four (4) years.

   1. (A) When the initial analysis taken in conformance with this section has established that the average annual concentration is less than half the MCL established by this section, analysis of a single sample may be substituted for the quarterly sampling procedure.
   2. (B) More frequent monitoring than once every four (4) years must be conducted when ordered by the department in the event of possible contamination or when changes in the source, distribution system or treatment processing occur which may increase the concentration of alpha particle radioactivity in the finished water.
   3. (C) A water system must conduct an analysis pursuant to this section within one (1) year of the introduction of a new water source.
   4. (D) If the average annual concentration of radium-228 has been assayed at least once using the quarterly sampling procedure, repeat monitoring after the initial analysis need not include radium-228, except when otherwise ordered by the department. When so ordered by the department, suppliers of water must conduct annual monitoring of any community water system in which the radium-226 concentration exceeds three (3) pCi per liter. 10 CSR 60-4
   5. (E) Where a supplier of water utilizing groundwater completes an initial analysis for alpha particle activity and the results show compliance with the MCLs and wells used as a supply source conform to the minimum sanitary features of construction prescribed by the department, the supplier of water may conduct analysis at a frequency determined by the department.
   6. (F) If the MCL for gross alpha particle activity or total radium is exceeded, a supplier of water to a community water system must give notice to the department and must notify the public as required by 10 CSR 60- 8.010. Monitoring at quarterly intervals must be continued until the annual average concentration no longer exceeds the MCL or until a monitoring schedule as a condition to a variance, exemption or enforcement action has become effective.

5. (3) For beta particle and photon radioactivity from man-made radionuclides—

   1. (A) The MCL must be the average annual concentration of beta particle and photon radioactivity from man-made radionuclides which produces an annual dose equivalent to the total body or any internal organ greater than four millirem (4 mrem) per year;

      1. 1. The concentration of tritium causing

a four (4) mrem per year dose equivalent in the total body must be calculated on the basis of twenty thousand (20,000) pCi per liter. The concentration of strontium-90 causing a four (4) mrem per year dose equivalent in the bone marrow must be calculated on the basis of eight (8) pCi per liter.

1. 2. The concentration of all other man-

made radionuclides causing a four (4) mrem per year total body or organ dose equivalent must be calculated on the basis of a two (2) liter per day drinking water intake using the one hundred sixty-eight (168)-hour data listed in Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupational Exposure, NBS Handbook 69, August 1963, United States Department of Commerce. If two (2) or more radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ must not exceed four (4) mrem per year;

1. (B) If the gross beta particle activity exceeds fifty (50) pCi per liter, an analysis of the sample must be performed to identify the major radioactive constituents present and the appropriate organ and total body doses must be calculated to determine compliance with this rule;
2. (C) These sampling and analysis requirements must apply to all community water systems designated by the department;
3. (D) Each analysis must be based on either an analysis of a composite of four (4) consecutive quarterly samples or analysis of four

1. (4) quarterly samples. All samples must be taken from a representative entry point(s) to the distribution system of the community water system, as approved by the department;

   1. (E) Community water systems serving one hundred thousand (100,000) or more individuals must conduct repeat analyses at least once every four (4) years starting June 24, 1981. Compliance with this rule may be assumed without repeat analysis if the average annual concentration of gross beta particle activity is less than fifty (50) pCi per liter and if the average annual concentrations of tritium and strontium-90 are less than those prescribed in section (2) of this rule, provided that if both tritium and strontium-90 are present, the sum of their annual dose equivalents to bone marrow does not exceed four (4) mrem per year;

   2. (F) A community water system designated by the department as utilizing water that is contaminated or has the potential to be contaminated by radioactivity may be required to initiate monitoring for gross beta particle and iodine-131 radioactivity, strontium-90 and tritium.

      1. 1. As a minimum quarterly monitoring

for gross beta particle activity must be based on the analysis of monthly samples or, with the express written permission of the department, a composite of three (3) monthly samples. If the gross beta particle activity in a sample exceeds fifteen (15) pCi per liter, the same or an equivalent sample must be analyzed for strontium-89 and cesium-134. If the gross beta particle activity exceeds fifty (50) Ci per liter, an analysis of the sample must be performed to identify the major radioactive constituents present and the appropriate organ and total body doses must be calculated to determine compliance.

1. 2. Monitoring for iodine-131 must be

conducted by analysis of a composite of samples taken on five (5) consecutive days, which shall be analyzed at least once each quarter. As ordered by the department, more frequent monitoring must be conducted when iodine- 131 is identified in the finished water.

1. 3. At least annual monitoring for stron-

tium-90 and for tritium must be conducted by analysis of four (4) samples obtained at quarterly intervals, or with the express written permission of the department, a composite of samples collected in four (4) consecutive quarters; and

1. (G) If the results of an analysis indicate that the level of any contaminant exceeds the MCL, a supplier of water to a community water system must report to the department and give notice as required by 10 CSR 60- 8.010. Monitoring at monthly intervals must be continued until the concentration does not exceed the MCL or until a monitoring schedule as a condition to a variance, exemption or enforcement action shall become effective.

1. (4) Noncommunity systems must monitor for radionuclides as directed by the department.

AUTHORITY: section 640.100, RSMo Supp. 1993.* Original rule filed May 4, 1979, effective Sept. 14, 1979. Amended: Filed April 14, 1981, effective Oct. 11, 1981. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993.