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(1) The total coliform monitoring frequency for all public water supply systems serving 1,000 or fewer people is one sample/month.

(2) The department adopts and incorporates by reference the table in 40 CFR 141.857(b), which sets forth total coliform monitoring frequency requirements for all public water supply systems serving more than 1,000 people.

(a) The minimum monitoring frequency for total coliforms is based on the average daily population served by the system during the month of peak use.

(3) Upon written request of the water supplier, the department may reduce the required coliform sampling frequency for a non-seasonal transient noncommunity water system that uses only ground water that is not under the direct influence of surface water and serves a maximum daily population of 1,000 persons or fewer to once in each calendar quarter.

(a) Before applying for quarterly monitoring, the system must operate and sample coliform bacteria monthly for a minimum of 24 consecutive months;

(b) The determination to reduce monitoring must be based upon the results of coliform bacteria samples from the past 24 consecutive months of system operation, sanitary surveys, and any other information that indicates quarterly sampling is adequate to protect public health;

(c) A water supplier, who is authorized to sample quarterly may continue to sample quarterly unless triggered to return to monthly monitoring. The following will trigger monthly monitoring, or more frequent monitoring pursuant to (4), the month following the event:

(i) the system triggers a Level 2 assessment or two Level 1 assessments under the provisions of 40 CFR 141.859 in a rolling 12-month period;

(ii) the system has an E. coli MCL violation;

(iii) the system has a coliform treatment technique violation;

(iv) the system has two 40 CFR Part 141, subpart Y, monitoring violations or one subpart Y monitoring violation and one Level 1 assessment under the provisions of 40 CFR 141.859 in a rolling 12-month period for a system on quarterly monitoring;

(v) constructing or modifying a system or system components without prior department approval, in violation of 75-6-112, MCA, and ARM 17.38.101;

(vi) determination that a source or distribution system is vulnerable to contamination based upon the results of a sanitary survey, sample analyses, technical investigations or other scientifically defensible information; or

(vii) not maintaining or operating a system in accordance with the requirements of this chapter when the department determines that the violation may affect the microbiological quality of the water supply system.

(d) When monthly monitoring is triggered, the department shall provide written notice to the system that monthly monitoring is required;

(e) Under extreme circumstances, for the purpose of determining eligibility for remaining on or qualifying for quarterly monitoring, the department may elect to not count monitoring violations under 40 CFR 141.860(c)(1) if the missed sample is collected no later than the end of the monitoring period following the monitoring period in which the sample was missed. The system must collect the make-up sample in a different week than the routine sample for that monitoring period and must collect the sample as soon as possible during the monitoring period. This authority does not affect the provisions of 40 CFR 141.860(c)(1) and 141.861(a)(4);

(f) The system must continue monthly monitoring until the following criteria have been met:

(i) within the last 12 months, the system must have completed a sanitary survey or a site visit by the department or a voluntary Level 2 assessment by a party approved by the department, be free of sanitary defects, and have a protected water source;

(ii) no MCL violations under 40 CFR 141.63, no monitoring violations under 40 CFR 141.21 or subpart Y, and no coliform treatment technique trigger exceedances or treatment technique violations under subpart Y, for a minimum of 12 months;

(iii) valid samples that do not contain coliform bacteria have been taken for at least 12 consecutive months of system operation;

(iv) the department has approved all submitted plans and specifications for system construction and modifications in accordance with 75-6-112, MCA, and ARM 17.38.101;

(v) the identified sources of contamination have been removed;

(vi) appropriate improvements in maintenance and operation have been implemented; and

(vii) the public water system petitions the department and the petition is approved in writing.

(g) Systems collecting samples on a quarterly frequency must conduct additional routine monitoring the month following one or more total coliform-positive samples (with or without a Level 1 treatment technique trigger). Systems must collect at least three routine samples during the next month. Systems may either collect samples at regular time intervals throughout the month or may collect all required routine samples on a single day if samples are taken from different sites. Systems must use the results of additional routine samples in coliform treatment technique trigger calculations under 40 CFR 141.859(a).

(4) The department may increase the required sampling frequency of any public water supply system based upon sampling results or other conditions that indicate a risk to the health of the water users. The department shall provide the supplier with a written explanation of any revised sampling requirements. A supplier shall implement any increase in sampling frequency immediately upon receipt of written notice of the increase from the department.

(5) The department adopts and incorporates by reference the following, which set forth requirements for the revised total coliform rule (RTCR):

(a) 40 CFR 141.851, except that the term "April 1, 2016" is replaced with "February 18, 2017." This rule sets forth general requirements for the RTCR;

(b) 40 CFR 141.852, which sets forth analytical methods and laboratory certification requirements for coliform testing, except that, for the purpose of this subchapter, the phrase "laboratory certified by the EPA or a primacy State" means "approved laboratory" as defined in ARM 17.38.202;

(c) 40 CFR 141.853, except for subsection (a)(5)(ii) and subsection (b). And except that the term "March 31, 2016" is replaced with "February 18, 2017." This rule sets forth general monitoring requirements for all systems;

(d) 40 CFR 141.854(a)(1) through 141.854(a)(3), which set forth general requirements for non-community water systems serving 1,000 or fewer people using only ground water;

(e) 40 CFR 141.854(i)(1), 141.856(a)(4)(i), and 141.857(a)(4)(i), except that the term "April 1, 2016" is replaced with "February 18, 2017." This rule provides start-up procedure requirements for seasonal systems. The department may exempt any seasonal system from some or all of the requirements for seasonal systems if the entire distribution system remains pressurized during the entire period that the system is not operating;

(f) 40 CFR 141.855(a), which sets forth general requirements for community systems serving 1,000 or fewer people using only ground water;

(g) 40 CFR 141.856(a)(1) through 141.856(a)(3) and 141.856(c), which set forth general requirements for subpart H public water systems serving 1,000 or fewer people;

(h) 40 CFR 141.857(a)(1) through 141.857(a)(3) and 141.857(c). This rule sets forth general requirements for public water systems serving more than 1,000 people;

(i) 40 CFR 141.858, which sets forth repeat monitoring and E. coli requirements, except for the following changes:

(i) the first sentence in 141.858(a)(1) is changed to "If a sample taken under ARM 17.38.215(1) through (3), 40 CFR 141.856(c), or 40 CFR 141.857(c), is total coliform-positive, the system must collect a set of repeat samples within 24 hours of being notified of the positive result."; and

(ii) 141.858(a)(5) is changed to "Results of all routine and repeat samples taken under ARM 17.38.215, not invalidated by the State, must be used to determine whether a coliform treatment technique trigger specified in 40 CFR 141.859 has been exceeded.";

(j) 40 CFR 141.859, except for subsection (a)(2)(iii) and subsection (b)(4)(ii). This rule sets forth requirements for coliform treatment technique triggers and assessments for protection against potential fecal contamination;

(k) 40 CFR 141.860, which sets forth requirements for violations; and

(l) 40 CFR 141.861, which sets forth requirements for reporting and recordkeeping.

(6) A special purpose sample, including a sample taken to determine whether adequate disinfection has occurred after pipe placement or repair, may not be taken from a part of the public water supply distribution system that is actively serving the public and must not be used to determine compliance with the RTCR. Repeat samples taken pursuant to 40 CFR 141.858 are not special purpose samples and must be used to determine whether the coliform treatment technique trigger has been exceeded.

(7) The department shall perform a special monitoring evaluation during each sanitary survey of ground water systems serving 1,000 or fewer people to review the status of the system, including the distribution system, to determine whether the system is on an appropriate monitoring schedule. After the department has performed the special monitoring evaluation during each sanitary survey, the department may modify the system's monitoring schedule, as necessary, or it may allow the system to stay on its existing monitoring schedule, consistent with this rule. The department may not allow systems to begin less frequent monitoring under the special monitoring evaluation unless the system has already met the applicable criteria for less frequent monitoring in (3)(b).

(8) A supplier shall collect at least two samples that must be analyzed for coliform bacteria from any new source of water supply to demonstrate compliance with this subchapter before the source is connected to a public water supply system.


History: 75-6-104, MCA; IMP, 75-6-104, MCA; NEW, 1977 MAR p. 1187, Eff. 12/24/77; AMD, 1982 MAR p. 594, Eff. 3/26/82; AMD, 1987 MAR p. 311, Eff. 3/27/87; AMD, 1991 MAR p. 1492, Eff. 8/16/91; AMD, 1994 MAR p. 2131, Eff. 8/12/94; TRANS, from DHES, 1996 MAR p. 1499; AMD, 1998 MAR p. 1167, Eff. 5/1/98; AMD, 1998 MAR p. 1927, Eff. 6/26/98; AMD, 1999 MAR p. 1222, Eff. 6/4/99; AMD, 2000 MAR p. 3400, Eff. 12/8/00; AMD, 2004 MAR p. 3016, Eff. 1/1/05; AMD, 2017 MAR p. 220, Eff. 2/18/17; AMD, 2024 MAR p. 253, Eff. 2/10/24.

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