PURPOSE: This rule establishes deadlines for public water systems to complete corrosion control treatment required in 10 CSR 60- 15.030 and to conduct associated monitoring.

1. (1) A large system (serving more than fifty thousand (50,000) persons) shall complete the corrosion control treatment steps as follows unless it is deemed to have optimized corrosion control under paragraph (1)(B)1. or

2. 2. of this rule.

   1. (A) Treatment Steps and Deadlines for Large Systems.

      1. 1. The system shall conduct initial mon-

itoring (10 CSR 60-15.070(4)(A) and 10 CSR 60-15.080(2)) during two (2) consecutive six- (6-) month monitoring periods by January 1, 1993.

1. 2. The system shall complete corrosion

control studies (10 CSR 60-15.030(3)) by July 1, 1994.

1. 3. The department shall designate opti-

mal corrosion control treatment (10 CSR 60- 15.030(4)) by January 1, 1995.

1. 4. The system shall install optimal cor-

rosion control treatment (10 CSR 60- 15.030(6)) by January 1, 1997.

1. 5. The system shall complete follow-up

sampling (10 CSR 60-15.070(4)(B) and 10 CSR 60-15.080(3)) by January 1, 1998.

1. 6. The department shall review installa-

tion of treatment and designate optimal water quality control parameters (10 CSR 60- 15.030(7)) by July 1, 1998.

1. 7. The system shall operate in compli-

ance with the department-specified optimal water quality control parameters (10 CSR 60- 15.030(8)) and continue to conduct tap sampling (10 CSR 60-15.070(4)(C) and 10 CSR 60-15.080(4)).

1. (B) A large system is deemed to have optimized corrosion control and is not required to complete the applicable corrosion control treatment steps identified in this section if the system satisfies one (1) of the following criteria. Any such large system deemed to have optimized corrosion control, and which has treatment in place, shall continue to operate and maintain optimal corrosion control treatment and meet any requirements that the department determines appropriate to ensure optimal corrosion control treatment is maintained.

   1. 1. The system demonstrates to the satis-

faction of the department that it has conducted activities equivalent to the corrosion control steps applicable to large systems. If the department makes this determination, it shall provide the system with written notice explaining the basis for its decision and shall specify the water quality control parameters representing optimal corrosion control in accordance with 10 CSR 60-15.030(7). Water systems deemed to have optimized corrosion control shall operate in compliance with the department-designated optimal water quality control parameters in accordance with 10 CSR 60-15.030(8) and continue to conduct lead and copper tap and water quality parameter sampling in accordance with 10 CSR 60- 15.070(4)(C) and 10 CSR 60-15.080(4). A system shall provide the department with the following information in order to support this determination:

1. A. The results of all test samples col-

lected for each of the water quality parameters in 10 CSR 60-15.030(3)(C);

1. B. A report explaining the test meth-

ods used by the water system to evaluate the corrosion control treatments listed in 10 CSR 60-15.030(3)(A), the results of all tests conducted, and the basis for the system’s selection of optimal corrosion control treatment;

1. C. A report explaining how corrosion

control has been installed and how it is being maintained to insure minimal lead and copper concentrations at consumers’ taps; and

1. D. The results of tap water samples

collected in accordance with 10 CSR 60- 15.070 at least once every six (6) months for one (1) year after corrosion control has been installed.

1. 2. The water system submits results of

tap water monitoring conducted in accordance with 10 CSR 60-15.070 and source water monitoring conducted in accordance with 10 CSR 60-15.090 that demonstrates for two (2) consecutive six- (6-) month monitoring periods that the difference between the ninetieth percentile tap water lead level, computed under 10 CSR 60-15.010(3)(C), and the highest source water lead concentration is less than the practical quantitation level for lead specified in 10 CSR 60-5.010(8)(B).

1. A. Those systems whose highest

source water lead level is below the method detection limit may also be deemed to have optimized corrosion control under this paragraph if the ninetieth percentile tap water lead level is less than or equal to the practical quantitation level for lead for two (2) consecutive six- (6-) month monitoring periods.

1. B. Any water system deemed to have

optimized corrosion control in accordance with this paragraph (1)(B)2. shall continue monitoring for lead and copper at the tap no less frequently than once every three (3) calendar years using the reduced number of sites specified in 10 CSR 60-15.070(3) and collecting the samples at times and locations specified in 10 CSR 60-15.070(4)(D)4.

1. C. Any water system deemed to have

optimized corrosion control pursuant to this paragraph (1)(B)2. shall notify the department in writing pursuant to 10 CSR 60- 7.020(1)(C) of any upcoming long-term changes in treatment or the addition of a new source as described in that subsection. The department must review and approve the addition of a new source or long-term change in water treatment before it is implemented by the water system.

1. D. A system is not deemed to have

optimized corrosion control pursuant to this paragraph (1)(B)2. and shall implement corrosion control treatment pursuant to subparagraph (1)(B)2.E. of this rule unless it meets the copper action level.

1. E. Any system triggered into corro-

sion control because it is no longer deemed to have optimized corrosion control under paragraph (1)(B)2. shall implement corrosion control treatment in accordance with the deadlines in subsection (2)(A) of this rule. Any such large system shall adhere to the schedule specified in subsection (2)(A) of this rule for medium-size systems, with the time periods for completing each step being triggered by the date the system is no longer deemed to have optimized corrosion control under paragraph (1)(B)2. of this rule.

1. (2) A small system (serving fewer than three thousand three hundred (3,300) persons) and a medium-size system (serving three thousand three hundred one to fifty thousand (3,301–50,000) persons) shall complete the corrosion control treatment steps specified as follows unless it is deemed to have optimized corrosion control under paragraph (2)(B)1., 2., or 3. of this rule:

   1. (A) Treatment Steps and Deadlines for Small and Medium-Size Systems.

      1. 1. The system shall conduct initial tap

sampling (10 CSR 60-15.070(4)(A) and 10 CSR 60-15.080(2)) until the system either exceeds the lead or copper action level or becomes eligible for reduced monitoring under 10 CSR 60-15.070(4)(D). A system exceeding the lead or copper action level shall recommend optimal corrosion control treatment (10 CSR 60-15.030(1)) within six (6) months after the end of the monitoring period during which it exceeds one (1) of the action levels.

1. 2. Within twelve (12) months after the

end of the monitoring period during which a system exceeds the lead or copper action level, the department may require the system to perform corrosion control studies (10 CSR 60-15.030(2)). If the department does not require the system to perform such studies, the department shall specify optimal corrosion control treatment within the following time frames:

1. A. For medium-size systems, within

eighteen (18) months after the end of the monitoring period during which that system exceeds the lead or copper action level; or

1. B. For small systems, within twenty-

four (24) months after the end of the monitoring period that system exceeds the lead or copper action level.

1. 3. If the department requires a system to

perform corrosion control studies under paragraph (2)(A)2. of this rule, the system shall complete the studies (10 CSR 60-15.030(3)) within eighteen (18) months after the department requires that those studies be conducted.

1. 4. If the system has performed corrosion

control studies under paragraph (2)(A)2. of this rule, the department shall designate optimal corrosion control treatment (10 CSR 60- 15.030(4)) within six (6) months after completion of paragraph (2)(A)3. of this rule.

1. 5. The system shall install optimal corro-

sion control treatment (10 CSR 60-15.030(6)) within twenty-four (24) months after the department designates that treatment.

1. 6. The system shall complete follow-up

sampling (10 CSR 60-15.070(4)(B) and 10 CSR 60-15.080(3)) within thirty-six (36) months after the department designates optimal corrosion control treatment.

1. 7. The department shall review the sys-

tem’s installation of treatment and designate optimal water quality control parameters (10 CSR 60-15.030(7)) within six (6) months after completion of paragraph (2)(A)6. of this rule.

1. 8. The system shall operate in compli-

ance with the department-designated optimal water quality control parameters (10 CSR 60- 15.030(8)) and continue to conduct tap sampling as specified in 10 CSR 60-15.070(4)(C) and 10 CSR 60-15.080(4);

1. (B) A smallor medium-size water system is deemed to have optimized corrosion control and is not required to complete the applicable corrosion control treatment steps identified in this section if the system satisfies one

1. (1) of the following criteria. Any such system deemed to have optimized corrosion control, and which has treatment in place, shall continue to operate and maintain optimal corrosion control treatment and meet any requirements that the department determines appropriate to ensure optimal corrosion control treatment is maintained.

   1. 1. The system meets the lead and copper

action levels during each of two (2) consecutive six- (6-) month monitoring periods conducted in accordance with 10 CSR 60- 15.070.

1. 2. The system demonstrates to the satis-

faction of the department that it has conducted activities equivalent to the corrosion control steps applicable to medium-size or small systems under this section. If the department makes this determination, it shall provide the system with written notice explaining the basis for its decision and shall specify the water quality control parameters representing optimal corrosion control in accordance with 10 CSR 60-15.030(7). Water systems deemed to have optimized corrosion control under this paragraph shall operate in compliance with the department-designated optimal water quality control parameters in accordance with 10 CSR 60-15.030(8) and shall continue to conduct lead and copper tap and water quality parameter sampling in accordance with 10 CSR 60-15.070(4)(C) and 10 CSR 60- 15.080(4). The system shall provide the department with the following information in order to support a determination:

1. A. The results of all test samples col-

lected for each of the water quality parameters in 10 CSR 60-15.030(3)(C);

1. B. A report explaining the test meth-

ods used by the water system to evaluate the corrosion control treatments listed in 10 CSR 60-15.030(3)(A), the results of all tests conducted and the basis for the system’s selection of optimal corrosion control treatment;

1. C. A report explaining how corrosion

control has been installed and how it is being maintained to insure minimal lead and copper concentrations at consumers’ taps; and

1. D. The results of tap water samples

collected in accordance with 10 CSR 60- 15.070 at least once every six (6) months for one (1) year after corrosion control has been installed.

1. 3. Any water system is deemed to have

optimized corrosion control if it submits results of tap water monitoring conducted in accordance with 10 CSR 60-15.070 and source water monitoring conducted in accordance with 10 CSR 60-15.090 that demonstrates for two (2) consecutive six- (6-) month monitoring periods that the difference between the ninetieth percentile tap water lead level computed under 10 CSR 60- 15.010(3)(C) and the highest source water lead concentration is less than the practical quantitation level for lead specified in 10 CSR 60-5.010(5)(H).

1. A. Those systems whose highest

source water lead level is below the method detection limit may also be deemed to have optimized corrosion control under this paragraph if the ninetieth percentile tap water lead level is less than or equal to the practical quantitation level for lead for two (2) consecutive six- (6-) month monitoring periods.

1. B. Any water system deemed to have

optimized corrosion control in accordance with this paragraph (2)(B)3. shall continue monitoring for lead and copper at the tap no less frequently than once every three (3) calendar years using the reduced number of sites specified in 10 CSR 60-15.070(3) and collecting the samples at times and locations specified in 10 CSR 60-15.070(4)(D)4.

1. C. Any water system deemed to have

optimized corrosion control pursuant to this paragraph (2)(B)3. shall notify the department in writing pursuant to 10 CSR 60- 7.020(1)(C) of any change in treatment or the addition of a new source. The department may require any such system to conduct additional monitoring or to take other action the department deems appropriate to ensure that such systems maintain minimal levels of corrosion in the distribution system.

1. D. A system is not deemed to have

optimized corrosion control pursuant to this paragraph (2)(B)3., and shall implement corrosion control treatment pursuant to subparagraph (2)(B)3.E. of this rule unless it meets the copper action level.

1. E. Any system triggered into corro- 10 CSR 60-15

sion control because it is no longer deemed to have optimized corrosion control under paragraph (2)(B)3. shall implement corrosion control treatment in accordance with the deadlines in subsection (2)(A) of this rule. Any such large system shall adhere to the schedule specified in subsection (2)(A) of this rule for medium-size systems, with the time periods for completing each step being triggered by the date the system is no longer deemed to have optimized corrosion control under paragraph (2)(B)3. of this rule; and

1. (C) Any smallor medium-size water system that is required to complete the corrosion control steps due to its exceedance of the lead or copper action level may cease completing the treatment steps whenever the system meets both action levels during each of two

1. (2) consecutive monitoring periods conducted pursuant to 10 CSR 60-15.070 and submits the results to the department. If any such water system after that exceeds the lead or copper action level during any monitoring period, the system (or the department, as the case may be) shall recommence completion of the applicable treatment steps, beginning with the first treatment step which was not previously completed in its entirety. The department may require a system to repeat treatment steps previously completed by the system where the department determines that this is necessary to implement properly the treatment requirements of this section. The department shall notify the system in writing of the determination and explain the basis for its decision. The requirement for any smallor medium-size system to implement corrosion control treatment steps (including systems deemed to have optimized corrosion control) is triggered whenever any smallor medium-size system exceeds the lead or copper action level.

AUTHORITY: section 640.100, RSMo 2016.* Original rule filed Aug. 4, 1992, effective May 6, 1993. Amended: Filed Aug. 14, 2001, effective April 30, 2002. Amended: Filed Oct. 17, 2011, effective May 30, 2012. Amended: Filed March 15, 2019, effective Nov. 30, 2019.

*Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999, 2002, 2006, 2012, 2014.