(a) Whenever the supplier of water determines or is advised by the State that one or more of the MCLs set forth in this Subpart are or may be exceeded; or that effectiveness of treatment processes diminishes to the extent that a violation of the treatment techniques or MCLs set forth in this Subpart may occur; or that any deleterious changes in raw water quality have occurred; or that a change in the character of the watershed or aquifer has been observed which may affect water quality; or that any combination of the preceding exists, the supplier of water shall notify the State and do the following:

1. (1) undertake a study to determine the cause or causes of such conditions, independent of known or anticipated treatment technology;
2. (2) modify existing or install treatment to comply, to the extent practicable, with sections 5-1.30, 5-1.50, 5-1.51 and 5-1.60 of this Subpart;
3. (3) initiate water sampling as needed to delineate the extent and nature of the cause of concern;
4. (4) investigate all or part of the watershed or aquifer to verify any existing or potential changes in the character of the sources of water supply; and
5. (5) submit a written report to the State within 30 days of the onset of the foregoing conditions summarizing the findings outlined in paragraphs (1) through (4) of this subdivision.