PURPOSE: This rule establishes maximum contaminant levels, action levels and monitoring requirements for inorganic contaminants.

1. (1) Maximum Contaminant Levels (MCL) or Action Levels.

   1. (A) The maximum contaminant or action level listed as follows for inorganic chemicals 1.–17. apply to community water systems. The maximum contaminant or action level listed as follows for inorganic chemicals 1.–
2. 9. and 11.–17. apply to nontransient noncommunity water systems. The maximum contaminant or action level listed as follows for inorganic chemicals 13.–15. apply to transient noncommunity water systems:

Contaminant 1. Antimony 2. Arsenic

1. 3. Asbestos
2. 4. Barium
3. 5. Beryllium
4. 6. Cadmium
5. 7. Chromium
6. 8. Copper
7. 9. Cyanide
8. 10. Fluoride
9. 11. Lead
10. 12. Mercury
11. 13. Nitrate
12. 14. Nitrite
13. 15. Total Nitrate and Nitrite
14. 16. Selenium
15. 17. Thallium Maximum Contaminant Level (MCL) 0.006 mg/l 0.05 mg/l (until Jan. 23, 2006) 0.010 mg/l (effective Jan. 23, 2006) 7 million fibers/liter (longer than 10 μm in length) 2 mg/l 0.004 mg/l 0.005 mg/l 0.1 mg/l * (See 10 CSR 60- 15.010(3)(B).) 0.2 mg/l 4.0 mg/l * (See 10 CSR 60- 15.010(3)(A).) 0.002 mg/l 10 mg/l (as nitrogen) 1 mg/l (as nitrogen)

10 mg/l (as nitrogen) 0.05 mg/l 0.002 mg/l 10 CSR 60-4

*Indicates action levels rather than maximum contaminant levels.

1. (B) Nitrate levels not to exceed twenty (20) mg/l may be allowed in a noncommunity water system if the supplier of water demonstrates to the satisfaction of the department that all of the following factors apply to the situation:

   1. 1. Such water will not be available to

children under six (6) months of age;

1. 2. The noncommunity water system is

meeting the public notification requirements under 10 CSR 60-8.010(9), including continuous posting of the fact that nitrate levels exceed ten (10) mg/l and the potential health effects of exposure;

1. 3. Local and state public health authori-

ties will be notified annually of nitrate levels that exceed ten (10) mg/l; and

1. 4. No adverse health effects shall result.

1. (2) Monitoring Frequency.

   1. (A) Asbestos. The frequency of monitoring to determine compliance with the maximum contaminant level (MCL) for asbestos specified in section (1) of this rule shall be conducted as follows:

      1. 1. Each community and nontransient

noncommunity water system is required to monitor for asbestos during the first three (3)-year compliance period of each nine (9)- year compliance cycle;

1. 2. If monitoring data collected after

January 1, 1990, are generally consistent with the requirements of subsection (2)(A) of this rule, then the state may allow systems to use those data to satisfy the monitoring requirement for the initial three (3)-year compliance period;

1. 3. Waivers.

   1. A. The system may apply to the

department for a use waiver as described in 10 CSR 60-6.060(2). If the department grants the waiver, the system is not required to monitor while the waiver is effective. A waiver remains in effect until the completion of the three (3)-year compliance period and must be renewed for subsequent compliance periods. Systems not receiving a waiver must monitor in accordance with the provisions of paragraph (2)(A)1. of this rule.

1. B. The department may grant a waiv-

er based on the potential asbestos contamination of the water source and the use of asbestos-cement pipe for finished water distribution and the corrosive nature of the water;

1. 4. Increased and decreased monitoring.

   1. A. A system that is out of compliance

with the MCL as determined in section (6) of this rule shall monitor quarterly beginning in the next quarter after the violation occurs.

1. B. The department may decrease the

quarterly monitoring requirement to the frequency specified in paragraph (2)(A)1. of this rule provided the department has determined that the analytical results for the system are reliably and consistently less than the MCL. In no case can the department make this determination unless a groundwater system takes a minimum of two (2) quarterly samples and a surface (or combined surface/ground) water system takes a minimum of four (4) quarterly samples; and

1. 5. Sample collection.

   1. A. A system vulnerable to asbestos

contamination due solely to corrosion of asbestos-cement pipe shall take at least one (1) sample at a tap served by asbestos-cement pipe and under conditions where asbestos contamination is most likely to occur.

1. B. A system vulnerable to asbestos

contamination due solely to source water shall monitor in accordance with the provision of section (4) of this rule.

1. C. A system vulnerable to asbestos

contamination due both to its source water supply and corrosion of asbestos-cement pipe shall take at least one (1) sample at a tap served by asbestos-cement pipe and under conditions where asbestos contamination is most likely to occur.

1. (B) Inorganic Chemicals. Community and nontransient noncommunity water systems shall monitor for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium and thallium as set forth here.

   1. 1. Groundwater systems shall take one

1. (1) sample at each sampling point during each three (3)-year compliance period beginning in the initial compliance period. Surface water systems (or combined surface/ground) shall take one (1) sample annually at each sampling point beginning in the initial compliance period.

   1. 2. Waivers.

      1. A. The system may apply to the

department for a susceptibility waiver as described in 10 CSR 60-6.060(3). If the department grants the waiver, the system is required to take a minimum of one (1) sample while the waiver is effective. The term during which the waiver is effective shall not exceed one (1) nine (9)-year compliance cycle. Systems not receiving a waiver must monitor in accordance with the provisions of paragraph (2)(B)1. of this rule.

1. B. The department may grant a waiv-

er provided surface water systems have monitored annually for at least three (3) years and groundwater systems have conducted a minimum of three (3) rounds of monitoring. At least one (1) sample shall have been taken since January 1, 1990. Both surface and ground water systems shall demonstrate that all previous analytical results were reliably and consistently less than the MCL. Systems that use a new water source are not eligible for a waiver until three (3) rounds of monitoring from the new source have been completed.

1. C. In determining the appropriate

reduced monitoring frequency, the department shall consider the reported concentrations from all previous monitoring, the degree of variation in reported concentrations and other factors which may affect contaminant concentrations (such as changes in groundwater pumping rates, changes in the system’s configuration, changes in the system’s operating procedures, or changes in stream flows or characteristics).

1. D. A decision by the department to

grant a waiver shall be made in writing and shall set forth the basis for the determination. The determination may be initiated by the department or upon an application by the public water system. The public water system shall specify the basis for its request. The department shall review and, where appropriate, revise its determination of the appropriate monitoring frequency when the system submits new monitoring data or when other data relevant to the system’s appropriate monitoring frequency become available.

1. E. The department may grant a waiv-

er for monitoring for cyanide, if the department determines that the system is not vulnerable due to lack of proximity to any industrial source of cyanide.

1. 3. Increased and decreased monitoring.

   1. A. Systems which exceed the MCLs

as calculated in section (6) of this rule shall monitor quarterly beginning in the next quarter after the violation occurs.

1. B. Where the results of sampling for

antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, or thallium indicate an exceedance of the maximum contaminant level, the department may require that one (1) additional sample be collected as soon as possible after the initial sample was taken (but not to exceed two (2) weeks) at the same sampling point.

1. C. The department may decrease the

quarterly monitoring requirement to the frequencies specified in paragraph (2)(B)1. of this rule provided it has determined that the analytical results for the system are reliably and consistently below the MCL. In no case can the department make this determination unless a groundwater system takes a minimum of two (2) quarterly samples and a surface water system (or combined surface/ ground) takes a minimum of four (4) quarterly samples.

1. D. All new systems or systems that

use a new source of water that begin operation after January 22, 2004 must demonstrate compliance with the MCL within a period of time specified by the department. The system must also comply with the initial sampling frequencies specified by the department to ensure a system can demonstrate compliance with the MCL. Routine and increased monitoring frequencies shall be conducted in accordance with the requirements in this section (2).

1. E. For systems which are conducting

monitoring at a frequency greater than annual, compliance with the maximum contaminant levels for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, or thallium is determined by a running annual average at any sampling point. If the average at any sampling point is greater than the MCL, then the system is out of compliance. If any one (1) sample would cause the annual average to be exceeded, then the system is out of compliance immediately. Any sample below the method detection limit shall be calculated at zero (0) for the purpose of determining the annual average. If a system fails to collect the required number of samples, compliance (average concentration) will be based on the total number of samples collected.

1. F. For systems which are monitoring

annually, or less frequently, and whose sample exceeds one-half (1/2) the MCL for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, nickel, selenium, or thallium, the system must begin quarterly monitoring. The system will not be in violation of the MCL until is has completed one (1) year of quarterly monitoring. If any sample result will cause the running annual average to exceed the MCL at any sampling point, the system is out of compliance with the MCL. If a system fails to collect the required number of samples, compliance (average concentration) will be based on the total number of samples collected.

1. G. Arsenic sampling results will be

reported to the nearest 0.001 mg/l.

1. (C) Nitrate. All public water systems (community; nontransient noncommunity; and transient noncommunity) shall monitor to determine compliance with the MCL for nitrate specified in section (1) of this rule. The frequency of monitoring shall be conducted as follows:

   1. 1. Groundwater systems.

      1. A. All public water systems (communi-

ty; nontransient noncommunity; and transient noncommunity) served by groundwater systems shall monitor annually beginning in the initial compliance period.

1. B. The repeat monitoring frequency

for groundwater systems shall be quarterly for at least one (1) year following any one (1) sample in which the concentration is greater than or equal to fifty percent (≥50%) of the MCL.

1. C. The department may allow a

groundwater system to reduce the sampling frequency to an annual basis after four (4) consecutive quarterly samples are reliably and consistently less than fifty percent (<50%) of the MCL.

1. D. After a round of quarterly sam-

pling is completed, a system which is monitoring annually shall take subsequent samples during the quarter(s) which previously resulted in the highest analytical result; and

1. 2. Surface water systems.

   1. A. All public water systems (commu-

nity; nontransient noncommunity; and transient noncommunity) served by a surface water system shall monitor quarterly beginning in the initial compliance period.

1. B. The department may allow a sur-

face water system to reduce the sampling frequency to annually if all analytical results from four (4) consecutive quarters are less than fifty percent (<50%) of the MCL.

1. C. A surface water system shall return

to quarterly monitoring if any one (1) sample is greater than or equal to fifty percent (≥50%) of the MCL.

1. D. After a round of quarterly sam-

pling is completed, a system which is monitoring annually shall take subsequent samples during the quarter(s) which previously resulted in the highest analytical result.

1. (D) Nitrite. All public water systems (community; nontransient noncommunity; and transient noncommunity) shall monitor to determine compliance with the MCL for nitrite specified in section (1) of this rule. The frequency of monitoring shall be conducted as follows:

   1. 1. All public water systems shall take

one (1) sample at each sampling point in the initial three (3)-year compliance period;

1. 2. After the initial sample, systems

where an analytical result for nitrite is less than fifty percent (<50%) of the MCL shall monitor at the frequency specified by the department; and

1. 3. Repeat monitoring.

   1. A. The repeat monitoring frequency

for any water system shall be quarterly for at least one (1) year following any one (1) sample in which the concentration is greater than or equal to fifty percent (≥50%) of the MCL.

1. B. The department may allow a sys-

tem to reduce the sampling frequency to annually after determining the analytical results for the system are reliably and consistently less than the MCL.

1. C. Systems which are monitoring

annually shall take each subsequent sample during the quarter(s) which previously resulted in the highest analytical result.

1. (E) Lead and Copper. All community and nontransient noncommunity water systems are required to monitor for lead and copper (see 10 CSR 60-15.070 for monitoring frequency, requirements and protocol for lead and copper).

1. (3) Monitoring Requirements.

   1. (A) Each public water system shall monitor at the time designated by the department during each three (3)-year compliance period.
   2. (B) Systems may apply to the department to conduct more frequent monitoring than the minimum monitoring frequencies specified in this chapter.
   3. (C) The department may require more frequent monitoring than specified in section (2) of this rule or may require confirmation samples for positive and negative results at its discretion.

2. (4) Monitoring Protocol. For the purpose of determining compliance with MCLs, samples must be collected for analyses as follows:

   1. (A) All public water systems shall take a minimum of one (1) sample at every entry point to the distribution system after any application of treatment which is representative of each source after treatment (called a sampling point) beginning in the initial compliance period;
   2. (B) The system shall take each sample at the same sampling point unless conditions make another sampling point more representative of each source or treatment plant; and
   3. (C) If a system draws water from more than one (1) source and the sources are combined before distribution, the system must sample at an entry point to the distribution system during periods of normal operating conditions (that is, when water is representative of all sources being used).

3. (5) Confirmation Samples.

   1. (A) Where the results of sampling for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium or thallium indicate an exceedance of the MCL, the department may require that one (1) additional sample be collected as soon as possible after the initial sample was taken (but not to exceed two (2) 10 CSR 60-4

weeks) at the same sampling point.

1. (B) Nitrate and Nitrite.

   1. 1. Where nitrate or nitrite sampling

results indicate an exceedance of the MCL, the system shall take a confirmation sample within twenty-four (24) hours of the system’s receipt of notification of the analytical results of the first sample.

1. 2. Systems unable to comply with the

twenty-four (24)-hour sampling requirement must immediately notify persons served by the public water system in accordance with 10 CSR 60-8.010(2). Systems exercising this option must take and analyze a confirmation sample within two (2) weeks of notification of the analytical results of the first sample.

1. (C) If a department-required confirmation sample is taken for any contaminant, then the results of the initial and confirmation sample shall be averaged. The resulting average shall be used to determine the system’s compliance in accordance with section (6) of this rule. The department has the discretion to delete results of obvious sampling errors.

1. (6) Compliance. Compliance with section (1) of this rule shall be determined based on the analytical result(s) obtained at each sampling point.

   1. (A) For systems which are conducting monitoring at a frequency greater than annual, compliance with the MCLs for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium or thallium is determined by a running annual average at each sampling point. If the average at any sampling point is greater than the MCL, then the system is out of compliance. If any one (1) sample would cause the annual average to be exceeded, then the system is out of compliance immediately. Any sample below the method detection limit shall be calculated at zero (0) for the purpose of determining the annual average.
   2. (B) For systems which are monitoring annually, or less frequently, the system is out of compliance with the MCLs for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium or thallium if the level of a contaminant at any sampling point is greater than the
2. MCL. If a confirmation sample is required by the department, the determination of compliance will be based on the average of the two

3. (2) samples.

   1. (C) Compliance with the MCLs for nitrate and nitrite is determined based on one (1) sample if the levels of these contaminants is below the MCLs. If the levels exceed the MCLs in the initial sample, a confirmation sample is required in accordance with subsection (5)(B) of this rule and compliance shall be determined based on the average of the initial and confirmation samples.
   2. (D) All community and nontransient noncommunity water systems are required to monitor for lead and copper (see 10 CSR 60- 15.070 for compliance requirements if lead and copper action levels are exceeded).

4. (7) Public Notice. If the result of analyses indicates that the level of antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium or thallium exceeds the MCL, the supplier of water must report to the department within seven (7) days.

   1. (A) When the system is out of compliance for antimony, asbestos, barium, beryllium, cadmium, chromium, cyanide, fluoride, mercury, selenium or thallium, as determined by section (6) of this rule, the supplier of water must notify the department as required by 10 CSR 60-7.010 and give public notice as required by 10 CSR 60-8.010.
   2. (B) When the system is out of compliance for nitrate, nitrite or total nitrate and nitrite, as determined by section (6) of this rule, the supplier of water must notify the department as required by 10 CSR 60-7.010 and give public notice as required by 10 CSR 60-8.010.
   3. (C) When the system is out of compliance for lead or copper as determined by 10 CSR 60-15.070, 10 CSR 60-15.080 and 10 CSR 60-15.090, the supplier of water must notify the department as required by 10 CSR 60- 7.020 and give public notice as required by 10 CSR 60-8.010.

AUTHORITY: section 640.100, RSMo Supp. 2002.* Original rule filed May 4, 1979, effective Sept. 14, 1979. Amended: Filed April 14, 1981, effective Oct. 11, 1981. Amended: Filed Aug. 4, 1987, effective Jan. 1, 1988. Rescinded and readopted: Filed March 31, 1992, effective Dec. 3, 1992. Amended: Filed Aug. 4, 1992, effective May 6, 1993. Amended: Filed May 4, 1993, effective Jan. 13, 1994. Amended: Filed Feb. 1, 1996, effective Oct. 30, 1996. Amended: Filed March 17, 2003, effective Nov. 30, 2003. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999, 2002.