Section 327IAC8-2.5-17. Operational evaluation levels; stage 2 disinfection byproducts requirements

   (a) A PWS has exceeded the operational evaluation level at any monitoring location when one (1) or both of the following occur:

(1) The sum of the two (2) previous quarters' TTHM results plus twice the current quarter's TTHM result, divided by four (4) to determine an average, exceeds eighty-thousandths (0.080) milligrams per liter (mg/L).

(2) The sum of the two (2) previous quarters' HAA5 results plus twice the current quarter's HAA5 result, divided by four (4) to determine an average, exceeds sixty-thousandths (0.060) mg/L.

  (b) The following are the requirements for a PWS if the operational evaluation level is exceeded:

(1) The PWS shall:

(A) conduct an operational evaluation; and

(B) submit a written report of the operational evaluation to the commissioner not later than ninety (90) days after being notified of the analytical result that caused the PWS to exceed the operational evaluation level.

The written report must be made available to the public upon request.

(2) The operational evaluation must include the following:

(A) Treatment and distribution operational practices, including:

(i) storage tank operations;

(ii) excess storage capacity;

(iii) distribution system flushing;

(iv) changes in sources or source water quality; and

(v) treatment changes or problems;

that can contribute to TTHM and HAA5 formation.

(B) Possible steps that could be considered to minimize future exceedances.

(3) A PWS may request and the commissioner may allow a PWS to limit the scope of the operational evaluation required under subdivision (2) if the PWS is able to identify the cause of the operational evaluation level exceedance.

(4) If the commissioner approves a PWS's request under subdivision (3) to limit the scope of the operational evaluation, the following apply:

(A) The commissioner shall approve a request for a limited scope of operational evaluation in writing.

(B) The PWS shall include the commissioner's approval with the completed report on the limited scope operational evaluation.

(C) The commissioner's approval of a limited scope operational evaluation does not extend the schedule under subdivision (1)(B) for submitting the written report.

(Water Pollution Control Division; 327 IAC 8-2.5-17; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA)