(1) General.

(a) When an MCL or MRDL violation or SAL exceedance occurs, the purveyor shall take follow-up action as described in this section.

(b) When a primary standard violation occurs the purveyor shall:

(i) Notify the department under WAC 246-290-480;

(ii) Notify the consumers served by the system and the owner or operator of any consecutive system served in accordance with 40 C.F.R. 141.201 through 208, and Part 7, Subpart A of this chapter;

(iii) Investigate the cause of the contamination, within the purveyor's control; and

(iv) Take action as directed by the department.

(c) When a secondary standard violation occurs, the purveyor shall notify the department and take action as directed by the department.

(d) When a SAL exceedance under WAC 246-290-315 occurs, the purveyor shall:

(i) Notify the department in accordance with WAC 246-290-480;

(ii) Notify water system users and the owner or operator of any consecutive system served water in exceedance of the SAL in accordance with WAC 246-290-71006;

(iii) Continue monitoring in accordance with subsection (8) or (9) of this section, as applicable;

(iv) Investigate the cause of the contamination within the purveyor's control; and

(v) Take action as directed by the department.

(e) The department may require additional sampling for confirmation of results.

(2) Bacteriological. Coliform treatment technique triggers and assessment requirements for protection against potential fecal contamination.

(a) Treatment technique triggers. Systems shall conduct assessments in accordance with (b) of this subsection after exceeding treatment technique triggers as follows:

(i) Level 1 treatment technique triggers.

(A) For systems taking forty or more routine samples per month, the system exceeds 5.0 percent total coliform-positive samples for the month.

(B) For systems taking fewer than forty routine samples per month, the system has two or more total coliform-positive samples in the same month.

(ii) Level 2 treatment technique triggers.

(A) An E. coli MCL violation, as specified in WAC 246-290-310 (2)(b).

(B) A second level 1 treatment technique trigger as defined in (a)(i) of this subsection within a rolling twelve-month period, unless the department has determined a likely reason that the samples that caused the first level 1 treatment technique trigger were total coliform-positive and has established that the system has corrected the problem.

(b) Requirements for assessments.

(i) Systems shall conduct level 1 and 2 assessments to identify the possible presence of sanitary defects and defects in distribution system coliform monitoring practices. Level 1 assessments must be conducted by the system operator or purveyor. Level 2 assessments must be conducted by the department or a party approved by the department which may include the system operator.

(ii) When conducting assessments, systems shall direct the assessor to evaluate minimum elements that include:

(A) Review and identification of atypical events that could affect distributed water quality or indicate that distributed water quality was impaired;

(B) Changes in distribution operation and maintenance that could affect distributed water quality, including water storage;

(C) Source and treatment considerations that bear on distributed water quality, where appropriate. For example, whether or not a groundwater system is disinfected;

(D) Existing water quality monitoring data;

(E) Inadequacies in sample sites, sampling protocol, and sample processing; and

(F) The system shall conduct the assessment consistent with any department directives that tailor specific assessment elements with respect to the size and type of the system and the size, type, and characteristics of the distribution system.

(iii) Level 1 assessments. A system shall conduct a level 1 assessment consistent with the requirements in subsection (2)(b) of this section if the system exceeds one of the treatment technique triggers in (a)(i) of this subsection.

(A) The system shall complete a level 1 assessment as soon as practical after any treatment technique trigger is met in (a)(i) of this subsection. The completed assessment must describe sanitary defects detected, corrective actions completed, and a proposed timetable for any corrective actions not already completed. The assessment may also note that no sanitary defects were identified. The system shall submit the completed level 1 assessment to the department within thirty days after the system learns that it has exceeded a treatment technique trigger.

(B) Upon completion and submission of the level 1 assessment by the system, the department shall determine if the system has identified a likely cause for the level 1 treatment technique trigger and has corrected the problem. If the system has not corrected the problem, the department shall determine if the proposed timetable for corrective action is sufficient.

(C) If after reviewing the completed level 1 assessment, the department determines the assessment is not sufficient, including any proposed timetable for any corrective actions not already completed, the department may require the system to submit a revised assessment to the department within thirty days from the date of department notification.

(iv) Level 2 assessments. A system shall conduct a level 2 assessment consistent with requirements in subsection (2)(b) of this section if the system exceeds one of the treatment technique triggers in (a)(ii) of this subsection. The system shall comply with any expedited actions or additional actions required by the department in the case of an E. coli MCL violation.

(A) A level 2 assessment must be conducted as soon as practical after any treatment technique trigger in (a)(ii) of this subsection and shall be conducted by either a water distribution manager 2, 3, or 4 certified in accordance with chapter 246-292 WAC, a licensed professional engineer that meets the requirements of WAC 246-290-040(1), a local health jurisdiction, or the department. The system shall submit a completed level 2 assessment to the department within thirty days after the system learns that it has exceeded a treatment technique trigger. The completed assessment must describe sanitary defects detected, corrective actions completed, and a proposed timetable for any corrective actions not already completed in accordance with (d) of this subsection. The assessment may also note that no sanitary defects were identified.

(B) Upon completion and submission of the level 2 assessment by the system, the department shall determine if the system has identified a likely cause for the level 2 treatment technique trigger and has corrected the problem. If the system has not corrected the problem, the department shall determine if the proposed timetable for corrective action is sufficient.

(C) If after reviewing the submitted level 2 assessment, the department determines the assessment is not sufficient, including any proposed timetable for any corrective actions not already completed in accordance with (d) of this subsection, the department may require the system to submit a revised assessment within thirty days from the date of department notification.

(c) To achieve compliance with the MCL for E. coli under WAC 246-290-310 (2)(b), the following are identified as the best technology, treatment techniques, or other means available:

(i) Protection of wells from fecal contamination by appropriate placement and construction;

(ii) Maintenance of a disinfectant residual throughout the distribution system;

(iii) Proper maintenance of the distribution system including appropriate pipe replacement and repair procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, cross-connection control, and continual maintenance of positive water pressure in all parts of the distribution system;

(iv) Filtration, disinfection, or both, of surface water, using the proper strength of oxidants such as chlorine, chlorine dioxide, or ozone; and

(v) For systems using groundwater, compliance with a wellhead protection program developed and implemented under WAC 246-290-135(3).

(d) Corrective action. Systems shall correct sanitary defects found through either a level 1 or level 2 assessment conducted under (b) of this subsection. For corrections not completed by the time of submission of the assessment to the department, the system shall complete the corrective actions in compliance with a timetable approved by the department in consultation with the system under (e) of this subsection. The system shall notify the department when each scheduled corrective action is completed.

(e) Consultation. At any time during the assessment or corrective action phase, the water system may request a consultation with the department to determine the appropriate actions to be taken. The system may consult with the department on all relevant information that may impact the system's ability to comply with the requirements of subsection (2) of this section, including the method of accomplishment, an appropriate time frame, and other relevant information.

(f) A treatment technique violation occurs when a system exceeds a treatment technique trigger specified in subsection (2)(a) of this section and then fails to conduct the required assessment or complete corrective actions within the time frame specified in subsection (2)(b) and (d) of this section.

(3) Inorganic chemical and physical follow-up monitoring shall be conducted in accordance with the following:

(a) For nonnitrate/nitrite primary inorganic chemicals, 40 C.F.R. 141.23 (a)(4), 141.23 (b)(8), 141.23 (c)(7), 141.23 (c)(9), 141.23 (f)(1), 141.23(g), 141.23(m) and 141.23(n);

(b) For nitrate, 40 C.F.R. 141.23 (a)(4), 141.23 (d)(2), 141.23 (d)(3), 141.23 (f)(2), 141.23(g), 141.23(m), 141.23(n), and 141.23(o);

(d) The purveyor of any public water system providing service that has secondary inorganic MCL exceedances shall take follow-up action as required by the department. Follow-up action shall be commensurate with the degree of consumer acceptance of the water quality and their willingness to bear the costs of meeting the secondary standard. For new community water systems and new nontransient noncommunity water systems without active consumers, treatment for secondary contaminant MCL exceedances will be required.

(4) Lead and copper follow-up monitoring shall be conducted in accordance with 40 C.F.R. 141.85(c), 141.86 (d)(2), 141.86 (d)(3), 141.87(c), 141.87(d) and 141.88(b) through 141.88(d).

(5) Turbidity.

Purveyors monitoring turbidity in accordance with Part 6 of this chapter shall provide follow-up under WAC 246-290-634.

(6) Organic chemicals. Follow-up monitoring shall be conducted in accordance with the following:

(a) For VOCs, 40 C.F.R. 141.24 (f)(11) through 141.24 (f)(15), and 141.24 (f)(22); or

(b) For SOCs, 40 C.F.R. 141.24 (h)(7) through 141.24 (h)(11), and 141.24 (h)(20).

(7) Radionuclide follow-up monitoring shall be conducted under 40 C.F.R. 141.26 (a)(2)(iv), 141.26 (a)(3)(ii) through (v), 141.26 (a)(4), 141.26 (b)(6), and 141.26 (c)(5).

(8) Organic contaminants with a SAL.

(a) All increased monitoring for organic contaminants will be for the test panel on which the contaminant is listed in WAC 246-390-075.

(b) The purveyor shall monitor quarterly as shown in Table 10 of this section. The number of samples required in the three quarters after the first detection will be determined based on the highest detection in the year of monitoring. For public water systems required to sample for PFAS under the federal Unregulated Contaminant Monitoring Rule 5 (UCMR5), if a detection is reported below the minimum detection limit per UCMR5 and is greater than twenty percent of a SAL, then one additional quarter of follow-up monitoring is required. The samples must be taken:

(i) Beginning in the calendar quarter following the first confirmed detection per WAC 246-290-315 (4)(b); and

(ii) At each sampling point from which the result was equal to or greater than the SDRL under chapter 246-390 WAC.

TABLE 10

MONITORING REQUIREMENTS FOLLOWING THE FIRST DETECTION OF AN ORGANIC CONTAMINANT WITH A SAL

If the highest detection in the first year is:	Total number of additional consecutive quarters.
≤ 20% of the SAL.	1
˃ 20% but < 80% of the SAL.	2
≥ 80% of the SAL.	3

(c) Ongoing monitoring is specified in Table 11 of this section, or as directed by the department. Ongoing monitoring is based upon the results of samples collected in the most recent year of monitoring, or the most recent result for samples collected less frequently than annually.

TABLE 11

ONGOING MONITORING REQUIREMENTS FOR SOURCES WITH ORGANIC CONTAMINANTS WITH A SAL

If highest detection being considered is:	Monitoring frequency:
≤ 20% of the SAL.	Every 3 years
˃ 20% but < 80% of the SAL.	Annually
≥ 80% of the SAL.	1. Quarterly, if contaminant is Tier 1, or Tier 2 and bioaccumulative per Table 17 in WAC 246-290-71006.
	2. Annually if the contaminant is Tier 2 and not bioaccumulative per Table 17 in WAC 246-290-71006.

(d) When the monitoring frequency is less often than quarterly, the purveyor shall collect samples during the quarter assigned by the department.

(e) The department may reduce the annual monitoring frequency to one sample every three years after three consecutive years of results that demonstrate the levels are less than eighty percent of the SAL.

(f) The department may increase the monitoring frequency from once every year or once every three years to once every quarter if results of reduced monitoring are equal to or greater than eighty percent of the SAL.

(9) Inorganic contaminants with a SAL.

(a) The purveyor shall collect quarterly samples at each sampling point beginning in the quarter following a detection greater than the SAL under Table 9 of this section. Increased monitoring for inorganic contaminants will be for a specific contaminant which is detected above the SAL.

(b) The department may reduce the quarterly monitoring frequency when results are reliably and consistently below the SAL. When the monitoring frequency is less often than quarterly, the purveyor shall collect samples during the quarter assigned by the department.

(10) If a contaminant has no MCL, MRDL, TT, or SAL, the department may use an EPA health advisory level to determine subsequent monitoring per this section.

(11) The department shall determine the purveyor's follow-up action when a contaminant not included in this chapter is detected.

PDFWAC 246-290-320

Follow-up action.