PURPOSE: This rule sets forth the procedures and requirements for monitoring drinking water to determine how corrosive the water is to the distribution system.

1. (1) General Requirements. All large (serving more than fifty thousand (>50,000) persons) water systems and all small-(serving less than or equal to three thousand three hundred (£3,300) persons) and medium-size (serving three thousand three hundred one to fifty thousand (3,301–50,000) persons) systems that exceed the lead or copper action level shall monitor water quality parameters in addition to lead and copper in accordance with this rule. The requirements of this rule are summarized in the table at the end of this rule.

   1. (A) Sample Collection Methods.

      1. 1. Tap samples shall be representative of

water quality throughout the distribution system taking into account the number of persons served, the different sources of water, the different treatment methods employed by the system and seasonal variability. Tap sampling under this rule is not required to be conducted at taps targeted for lead and copper sampling under 10 CSR 60-15.070(1). (Note: Systems may find it convenient to conduct tap sampling for water quality parameters at sites used for coliform sampling under 10 CSR 60-4.020(1)(A).)

1. 2. Samples collected at the entry

point(s) to the distribution system shall be from locations representative of each source after treatment. 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).

1. (B) Number of Samples.

   1. 1. Systems shall collect two (2) tap sam-

ples for applicable water quality parameters during each monitoring period specified under sections (2)–(5) of this rule from the following number of sites:

Sites for Water

System Size Quality Parameters

(# People Served) (Number) >100,000 25 10,001–100,000 10 3,301–10,000 3 501–3,300 2 101–500 1 £100 1

1. 2. Except as provided in subsection

(3)(C) of this rule, systems shall collect two (2) samples for each applicable water quality parameter at each entry point to the distribution system during each monitoring period specified in section (2) of this rule. During each monitoring period specified in sections (3)–(5) of this rule, systems shall collect one (1) sample for each applicable water quality parameter at each entry point to the distribution system. (2) Initial Sampling. All large (serving more than fifty thousand (>50,000) persons) water systems shall measure the applicable water quality parameters as specified in this rule at taps and at each entry point to the distribution system during each six- (6-) month monitoring period specified in 10 CSR 60- 15.070(4)(A). All small (serving less than or equal to three thousand three hundred (£3,300) persons) and medium-size (serving three thousand three hundred one to fifty thousand (3,301–50,000) persons) systems shall measure the applicable water quality parameters at the locations specified as follows during each six- (6-) month monitoring period specified in 10 CSR 60-15.070(4)(A) during which the system exceeds the lead or copper action level:

1. (A) At taps—

   1. 1. pH;
   2. 2. Alkalinity;
   3. 3. Orthophosphate, when an inhibitor

containing a phosphate compound is used;

1. 4. Silica, when an inhibitor containing a

silicate compound is used;

1. 5. Calcium;
2. 6. Conductivity; and
3. 7. Water temperature; and
4. (B) At each entry point to the distribution system, all of the applicable parameters listed in subsection (2)(A) of this rule.

1. (3) Monitoring After Installation of Corrosion Control. Any large system which installs optimal corrosion control treatment pursuant to 10 CSR 60-15.020(1)(A)4. shall measure the water quality parameters at the locations and frequencies specified in this section during each six- (6-) month monitoring period specified in 10 CSR 60- 15.070(4)(B)1. Any smallor medium-size system which installs optimal corrosion control treatment shall conduct monitoring during each six- (6-) month monitoring period as specified in 10 CSR 60-15.070(4)(B)2. in which the system exceeds the lead or copper action level.

   1. (A) At taps, two (2) samples for—

      1. 1. pH;
      2. 2. Alkalinity;
      3. 3. Orthophosphate, when an inhibitor

containing a phosphate compound is used;

1. 4. Silica, when an inhibitor containing a

silicate compound is used; and

1. 5. Calcium, when calcium carbonate

stabilization is used as part of corrosion control.

1. (B) Except as provided in subsection (3)(C) of this rule, at each entry point to the distribution system, at least one (1) sample no less frequently than every two (2) weeks (bi-weekly)—

   1. 1. For pH;
   2. 2. When alkalinity is adjusted as part of

optimal corrosion control, a reading of the dosage rate of the chemical used to adjust alkalinity and the alkalinity concentration; and

1. 3. When a corrosion inhibitor is used as

part of optimal corrosion control, a reading of the dosage rate of the inhibitor used and the concentration of orthophosphate or silica (whichever is applicable).

1. (C) Any groundwater system can limit entry point sampling described in subsection (3)(B) of this rule to those entry points that are representative of water quality and treatment conditions throughout the system. If water from untreated groundwater sources mixes with water from treated groundwater sources, the system must monitor for water quality parameters both at representative entry points receiving treatment and representative entry points receiving no treatment. Prior to the start of any monitoring under this subsection, the system shall provide to the department written information identifying the selected entry points and documentation, including information on seasonal variability, sufficient to demonstrate that the sites are representative of water quality and treatment conditions throughout the system.

1. (4) Monitoring After Department Specifies Water Quality Parameter Values for Optimal Corrosion Control. After the department specifies the values for applicable water quality control parameters reflecting optimal corrosion control treatment under 10 CSR 60- 15.030(7), all large (serving more than fifty thousand (>50,000) persons) systems shall measure the applicable water quality parameters in accordance with section (3) of this rule and determine compliance with the requirements of 10 CSR 60-15.030(8) every six (6) months with the first six- (6-) month period to begin on either January 1 or July 1, whichever comes first, after the department specifies the optimal values under 10 CSR 60-15.030(7). Any small- (serving less than three thousand three hundred (<3,300) persons) or medium-size (serving three thousand three hundred one to fifty thousand (3,301– 50,000) persons) system shall conduct such monitoring during each six- (6-) month period specified in 10 CSR 60-15.070(4)(C) in which the system exceeds the lead or copper action level. For any such smalland medium-size system that is subject to a reduced monitoring frequency pursuant to 10 CSR 60- 15.070(4)(D) at the time of the action level exceedance, the start of the applicable six- (6- ) month period under this section shall coincide with the start of the applicable monitoring period under 10 CSR 60-15.070(4)(D). Compliance with department-designated optimal water quality parameter values shall be determined as specified under 10 CSR 60- 15.030(8).

2. (5) Reduced Monitoring.

   1. (A) Any water system that maintains the range of values for the water quality parameters reflecting optimal corrosion control treatment during each of two (2) consecutive six- (6-) month monitoring periods under section

3. (4) of this rule shall continue monitoring at the entry point(s) to the distribution system as specified in subsection (3)(B) of this rule. That system may collect two (2) tap samples for applicable water quality parameters from the following reduced number of sites during each six- (6-) month monitoring period.

   Sites for

System Size Water Quality Parameters (# People Served) (Reduced Number) >100,000 10 10,001–100,000 7 3,301–10,000 3 501–3,300 2 101–500 1 £100 1

1. (B) Any water system that maintains the range of values for the water quality parameters reflecting optimal corrosion control treatment specified by the department under 10 CSR 60-15.030(6) during three (3) consecutive years of annual monitoring under this subsection may reduce the frequency with which it collects the number of tap samples for applicable water quality parameters specified in subsection (5)(A) of this rule from every six (6) months to annually. This sampling begins during the calendar year immediately following the end of the monitoring period in which the third consecutive year of six- (6-) month monitoring occurs. Any water system that maintains the range of values for the water quality parameters reflecting optimal corrosion control treatment specified by the department under 10 CSR 60-15.030(6) during three (3) consecutive years of annual monitoring under this rule may reduce the frequency with which it collects the number of tap samples for applicable water quality parameters specified in section (6) of this rule from annually to every three (3) years. This sampling begins no later than the third calendar year following the end of the monitoring period in which the third consecutive year of monitoring occurs. A water system may reduce the frequency with which it collects tap samples for applicable water quality parameters specified in subsection (5)(A) of 10 CSR 60-15

this rule to every three (3) years if it demonstrates during two (2) consecutive monitoring periods that its tap water lead level at the ninetieth percentile is less than or equal to the PQL for lead specified in 10 CSR 60- 5.010(5)(H), that its tap water copper level at the ninetieth percentile is less than or equal to 0.65 mg/L for copper, and that it also has maintained the range of values for the water quality parameters reflecting optimal corrosion control treatment specified by the department under 10 CSR 60-15.030(7). Monitoring conducted every three (3) years shall be done no later than every third calendar year.

1. (C) A water system that conducts sampling annually shall collect these samples evenly throughout the year so as to reflect seasonal variability.
2. (D) Any water system subject to the reduced monitoring frequency that fails to operate at or above the minimum value or within the range of values for the water quality parameters specified by the department in 10 CSR 60-15.030(7) for more than nine (9) days in any six- (6-) month period specified in 10 CSR 60-15.030(8) shall resume distribution system tap water sampling in accordance with the number and frequency requirements in section (4) of this rule. Such a system may resume annual monitoring for water quality parameters at the tap at the reduced number of sites specified in subsection (5)(A) of this rule after it has completed two (2) subsequent consecutive six- (6-) month rounds of monitoring that meet the criteria of that paragraph and/or may resume triennial monitoring for water quality parameters at the tap at the reduced number of sites after it demonstrates through subsequent rounds of monitoring that it meets the criteria of either paragraph (5)(B)1. or (5)(B)2. of this rule.

1. (6) Additional Monitoring by Systems. The results of any monitoring conducted in addition to the minimum requirements of this rule shall be considered by the system and the department in making any determinations (that is, determining concentrations of water quality parameters) under this rule or 10 CSR 60-15.030. Summary of Monitoring Requirements for Water Quality Parameters1

Monitoring Period Initial monitoring

After installation of corrosion control

After department specifies parameter values for optimal corrosion control

1Table is for illustrative purposes; consult the text of this rule for precise regulatory requirements. 2Smalland medium-size systems have to monitor for water quality parameters only during monitoring periods in which the system exceeds the lead or copper action level. 3Orthophosphate must be measured only when an inhibitor containing a phosphate compound is used. Silica must be measured only when an inhibitor containing silicate compound is used. 4Calcium must be measured only when calcium carbonate stabilization is used as part of corrosion control. 5Inhibitor dosage rates and inhibitor residual concentrations (orthophosphate or silica) must be measured only when an inhibitor is used. 6Groundwater systems may limit monitoring to representative locations throughout the system. 7Water systems may reduce frequency of monitoring for water quality parameters at the tap from every six (6) months to annually if they have maintained the range of values for water quality parameters reflecting optimal corrosion control during three (3) consecutive years of monitoring. 8Water systems may further reduce the frequency of monitoring for water quality parameters at the tap from annually to once every three (3) years if they have maintained the range of values from water quality parameters reflecting optimal corrosion control during three (3) consecutive years of annual monitoring. Water systems may accelerate to triennial monitoring for quality parameters at the tap if they have maintained ninetieth percentile lead levels less than or equal to 0.005 mg/L, ninetieth percentile copper levels less than or equal to 0.65 mg/L, and the range of water quality parameters designated by the department under 10 CSR 60-15.030(7) as representing optimal corrosion control during two (2) consecutive six- (6-) month monitoring periods. Parameters2 pH, alkalinity, orthophosphate or silica3, calcium, conductivity, temperature

pH, alkalinity, orthophosphate or silica3, calcium4

pH, alkalinity dosage rate and concentration (if alkalinity adjusted as part of corrosion control), inhibitor dosage rate and inhibitor residual5

pH, alkalinity, orthophosphate or silica3, calcium4

pH, alkalinity dosage rate and concentration (if alkalinity adjusted as part of corrosion control), inhibitor dosage rate and inhibitor residual5 Location Taps and at entry point(s) to the distribution system

Taps

Entry point(s) to distribution system6

Taps

Entry point(s) to the distribution system6 Frequency Every six (6) months

Every six (6) months

No less frequently than every two (2) weeks

Every six (6) months

No less frequently than every two (2) weeks

AUTHORITY: section 640.100, RSMo Supp. 2011.* Original rule filed Aug. 4, 1992, effective May 6, 1993. Amended: Filed Feb. 1, 1996, effective Oct. 30, 1996. Amended: Filed Aug. 14, 2001, effective April 30, 2002. Amended: Filed Oct. 17, 2011, effective May 30, 2012.

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