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, all small (serving less than or equal to three thousand three hundred (@3300) persons) and medium-size (serving three thousand three hundred one to fifty thousand (3301–50,000) 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 3301–10,000 3 501–3300 2 101–500 1 @100

1. 2. 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.

1. (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 (@3300) persons) and medium-size (serving three thousand three hundred one to fifty thousand (3301–50,000) 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)1. 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 small or 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) At each entry point to the distribution system, one (1) sample 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. (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

   (930/96) Rebecca McDowell Cook

corrosion control treatment under 10 CSR 60-15.030(6), 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 during each monitoring period specified in 10 CSR 60-15.070(4)(C). Any small (serving less than three thousand three hundred (<3300) persons) or medium-size (serving three thousand three hundred one to fifty thousand (3301–50,000) persons) system shall conduct monitoring during each monitoring period specified in 10 CSR 60- 15.070(4)(C) in which the system exceeds the lead or copper action level. The system may take a confirmation sample for any water quality parameter value no later than three (3) days after the first sample. If a confirmation sample is taken, the result must be averaged with the first sampling result and the average must be used for any compliance determinations under 10 CSR 60-15.030(7). The department has the discretion to delete results of obvious sampling errors from this calculation.

1. (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

2. (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 Water System Size Quality Parameters (# People served) Reduced Number >100,000 10,001–100,000 3301–10,000 501–3300 101–500 @100 (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 annually to every three (3) years.

1. (C) A water system that conducts sampling annually shall collect these samples evenly 10 CSR 60-15

throughout the year so as to reflect seasonal variability.

1. (D) Any water system subject to reduced monitoring frequency that fails to operate within the range of values for the water quality parameters specified by the department under 10 CSR 60-15.030(6) shall resume tap water sampling in accordance with the number and frequency requirements in section (3) 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

1Table is for illustrative purposes; consult the text of this section for precise regulatory requirements. 2Small and 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. Parameters2 pH, alkalinity, orthophosphate or silica3, calcium, conductivity, temperature

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

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

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

Entry point(s) to distribution system

Entry point(s) to the distribution system

Entry point(s) to the distribution system

(930/96) Rebecca McDowell Cook

Frequency Every 6 months system

Biweekly

Biweekly

Biweekly

AUTHORITY: section 640.100, RSMo (1994).* Original rule filed Aug. 4, 1992, effective May 6, 1993. Amended: Filed Feb. 1, 1996, effective Oct. 30, 1996. *Original authority 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995.