R 325.10728 Radionuclides; reduced monitoring for gross alpha particle activity, radium-226, radium-228, and uranium.

Rule 728. (1) The department may allow community water supplies to reduce the future frequency of monitoring from once every 3 years to once every 6 or 9 years at each sampling point, based on the criteria in the following table: Table 1 Radionuclides reduced monitoring criteria For gross alpha particle activity, uranium, and combined radium 226 radium-228, if the average of the initial monitoring results for each contaminant at a sampling point is... Then the supply shall collect and analyze for, that contaminant using at least one sample at that sampling point every... (a) Below the detection limit1 9 years (b) At or above the detection limit, but at or below half the MCL2 6 years (c) Above half the MCL, but at or below the MCL2 3 years 1 For combined radium-226 and 228, both contaminants shall be below the detection limit. 2 For combined radium-226 and radium-228, the analytical results for radium-226 and 228 shall be combined. (2) A supply shall use the samples collected during the reduced monitoring period to determine the monitoring frequency for subsequent monitoring periods. For example, if a supply's sampling point is on a 9-year monitoring period, and the sample result is above half the MCL, then the next monitoring period for that sampling point is 3 years. (3) If a supply has a monitoring result that exceeds the MCL while on reduced monitoring, then the supply shall collect and analyze quarterly samples at that sampling point until the supply has results from 4 consecutive quarters that are at or below the MCL, unless the supply enters into another schedule as part of a formal compliance agreement with the department.