26.04.01.13

.13 Sampling Analysis: Gross Alpha Particle Activity, Radium-226, Radium-228, Uranium.

A. This regulation applies to a community water system (CWS).

B. Sampling Location. The supplier of water to a community water system shall:

(1) Sample at every entry point to the distribution system that is representative of all sources being used (after this called a sampling point) under normal operating conditions; and

(2) Take each sample at the same sampling point unless:

(a) Conditions make another sampling point more representative of each source; or

(b) The Approving Authority has designated a distribution system location.

C. Initial Monitoring.

(1) The supplier of water to an existing CWS shall conduct initial monitoring by December 31, 2007 in order to determine compliance with Regulation .09A of this chapter. The Approving Authority may require more frequent monitoring in the event of possible contamination or if changes in the distribution system or treatment processes occur that may increase the concentration of radioactivity in finished water.

(2) The supplier of water to a new CWS or a CWS that uses a new source of water shall begin to conduct initial monitoring for the new source within the first quarter after initiating use of the source.

(3) For systems without acceptable historical data, as defined in §C(4) of this regulation, the supplier of water shall collect four consecutive quarterly samples at all sampling points before December 31, 2007.

(4) The Approving Authority may allow historical monitoring data collected at a sampling point, if designated as appropriate by the Approving Authority, to satisfy the initial monitoring requirements for that sampling point, for the following situations:

(a) A CWS having only one entry point to the distribution system may use the monitoring data from the last compliance monitoring period beginning June 1, 2000 through December 8, 2003;

(b) A CWS with multiple entry points and having appropriate historical monitoring data for each entry point to the distribution system may use the monitoring data from the last compliance monitoring period beginning June 1, 2000 through December 8, 2003; or

(c) A CWS with historical monitoring data for a representative point in the distribution system may use the monitoring data from the last compliance monitoring period beginning June 1, 2000 through December 8, 2003, if:

(i) The Approving Authority finds that the historical data satisfactorily demonstrate that each entry point to the distribution system is expected to be in compliance based upon the historical data and reasonable assumptions about the variability of contaminant levels between entry points; and

(ii) The Approving Authority makes a written finding indicating how the data conforms to these requirements.

(5) For gross alpha particle activity, uranium, radium-226, and radium-228 monitoring, the Approving Authority may waive the final 2 quarters of initial monitoring for a sampling point if the results of the samples from the previous 2 quarters are below the detection limit.

(6) If the average of the initial monitoring results for a sampling point is above the maximum contaminant level (MCL), the supplier of water shall collect and analyze quarterly samples at that sampling point until the system has results from 4 consecutive quarters that are at or below the MCL, unless the supplier enters into another schedule as part of a formal compliance agreement with the Approving Authority.

D. Reduced Monitoring.

(1) The supplier of water may reduce the future frequency of monitoring for a contaminant from once every 3 years to once every 9 years at each sampling point, if the average of the initial monitoring results for each such contaminant is below the detection limit specified in 40 CFR §141.25, Table B.

(2) The supplier of water may reduce the future frequency of monitoring for a contaminant from once every 3 years to once every 6 years at each sampling point, if:

(a) For gross alpha particle activity or uranium, the average of the initial monitoring results are at or above the detection limit but at or below 1/2 the MCL; or

(b) For combined radium-226 and radium-228, the average of the initial monitoring results is at or above the detection limit but at or below 1/2 the MCL.

(3) The supplier of water shall collect and analyze at least one sample for a contaminant at each sampling point every 3 years if:

(a) For gross alpha particle activity or uranium, the average of the initial monitoring results is above 1/2 the MCL but at or below the MCL; or

(b) For combined radium-226 and radium-228, the average of the initial monitoring results is above 1/2 the MCL but at or below the MCL.

(4) The supplier of water shall use the samples collected during the most recent reduced monitoring period to determine the monitoring frequency for subsequent monitoring periods. For example, if a system's sampling point is on a 9-year monitoring period, and the sample result is above 1/2 MCL, the next monitoring period for that sampling point is 3 years.

(5) If a CWS has a monitoring result that exceeds the MCL while on reduced monitoring, the supplier of water shall collect and analyze quarterly samples at that sampling point until the system has results from 4 consecutive quarters that are below the MCL, unless the supplier of water enters into another schedule as part of a formal compliance agreement with the Approving Authority.

E. Compositing.

(1) To fulfill quarterly monitoring requirements for gross alpha particle activity, radium-226, radium-228, or uranium, a supplier of water may composite up to four consecutive quarterly samples from a single entry point if analysis is done within a year of the first sample.

(2) The composited result shall be used as the average analytical result to determine compliance with the MCLs and the future monitoring frequency.

(3) If the analytical result from the composited sample is greater than 1/2 MCL, the Approving Authority may direct the water supplier to take additional quarterly samples before allowing the system to sample under a reduced monitoring schedule.

F. Substitutions.

(1) If the measured gross alpha particle activity does not exceed 5 picocuries per liter (pCi/l), a gross alpha particle activity measurement may be substituted for the required radium-226 measurement.

(2) If the measured gross alpha particle activity does not exceed 15 picocuries per liter (pCi/l), a gross alpha particle activity measurement may be substituted for the required uranium measurement.

(3) If a supplier of water uses a gross alpha particle activity measurement instead of a radium-226 measurement, uranium measurement, or both, the gross alpha particle activity analytical result shall be used to determine the future monitoring frequency for radium-226, uranium, or both.

(4) If the gross alpha particle activity result is less than detection, 1/2 the detection limit shall be used to determine compliance and the future monitoring frequency.

G. Analyses conducted to determine compliance with this regulation shall be made in accordance with those methods specified in 40 CFR §141.25 (1989), which is incorporated by reference.

H. Detection Limit.

(1) For the purpose of monitoring radioactivity concentrations in drinking water, the required sensitivity of the radioanalysis is defined in terms of a detection limit. The detection limit shall be that concentration which can be measured with an accuracy of plus or minus 100 percent at the 95 percent confidence level (1.96 sigma where sigma is the standard deviation of the net counting rate of the sample).

(2) To determine compliance with Regulation .09A(1) of this chapter, the detection limit may not exceed 1 pCi/liter. To determine compliance with Regulation .09A(2) of this chapter, the detection limit may not exceed 3 pCi/liter.

(3) To determine compliance with Regulation .09B, the detection limit may not exceed the concentrations listed in Table A of this regulation.

(4) To judge compliance of a public water system with the maximum contaminant levels listed in Regulation .09A and B of this chapter, averages of data shall be used and rounded to the same number of significant figures as the maximum contaminant level for the substance in question.

Table A
Detection Limits for Man-Made Beta Particle Photon Emitters
Radionuclide Detection Limit (pCi/l)
Tritium 1,000
Strontium-89 10
Strontium-90 2
Iodine-131 1
Cesium-134 10
Gross beta 4
Other radionuclides 1/10 of the applicable limit