1. (a) After the initial sample, a PWS for which the analytical result for nitrite is less than 50% of the MCL shall monitor for nitrite annually.
2. (b) The O/O of a community water system, non-transient non-community water system, or transient non-community water system shall monitor for nitrite quarterly for at least one year following any one sample in which the concentration of nitrite is equal to or greater than 50% of the MCL.
3. (c) After a minimum of one year of quarterly sampling, the O/O may submit a written request to the department that the monitoring frequency be reduced.

4. (d) The written request shall include:

   1. (1) The name of the PWS;
   2. (2) The PWS identifier for the PWS;
   3. (3) A summary of all quarterly sampling results; and
   4. (4) Confirmation that the PWS is not operating any type of treatment to reduce the amount of nitrite.

5. (e) The department shall approve a reduction in monitoring from quarterly to annually if the department determines that:

   1. (1) Based on 4 consecutive quarterly samples, the nitrite levels are reliably and consistently less than the nitrite MCL; and
   2. (2) The PWS is not operating any type of treatment to reduce the amount of nitrite.
6. (f) An O/O who monitors annually shall collect each subsequent sample during the quarter(s) which previously resulted in the highest analytical results.

Source. #9700, eff 5-1-10; amd by #10771, eff 2-1-15; ss by #12668, eff 1-1-19