PURPOSE: This rule establishes the maximum contaminant levels and monitoring 10 CSR 60-4

requirements for total trihalomethanes and other disinfection by-products.

1. (1) Applicability. This rule applies to community water systems and nontransient noncommunity water systems that add a chemical disinfectant to the water in any part of the drinking water treatment process or provide water that contains a chemical disinfectant and to water treatment plants proposed for construction or major modification as indicated in this section. The rule has different requirements and compliance dates, based on system size and type of source water.

   1. (A) Community water systems serving 10,000 or more people and using surface water or groundwater under the direct influence of surface water (GWUDISW) must continue complying with the maximum contaminant level (MCL) of 0.10 for total trihalomethanes (TTHM) and section (3) of this rule until December 31, 2001. Beginning January 1, 2002, these systems and nontransient noncommunity water systems serving 10,000 or more people and using surface water or GWUDISW must comply with sections (4)–(5) of this rule and the MCLs of 0.080 for TTHM, 0.060 for haloacetic acids five (HAA5), 0.010 for bromate, and 1.0 for chlorite.
   2. (B) Community water systems and nontransient noncommunity water systems serving less than 10,000 people and using surface water or GWUDISW. Beginning January 1, 2004, these systems must comply with sections (4)–(5) of this rule and the MCLs of 0.080 for TTHM, 0.060 for HAA5, 0.010 for bromate, and 1.0 for chlorite.

   3. (C) Community water systems and nontransient noncommunity water systems using groundwater. Beginning January 1, 2004, these systems must comply with sections (4)–(5) of this rule and the MCLs of 0.080 for TTHM, 0.060 for HAA5, 0.010 for bromate, and 1.0 for chlorite. Table 1. Compliance with Disinfection By-Product Requirements

      Community water systems serving 10,000 or more people and using surface water or groundwater under the direct influence of surface water (GWUDISW)

   4. (D) A system that is installing granular activated carbon (GAC) or membrane technology to comply with this rule may apply to the department for an extension of up to twenty-four (24) months past December 16, 2001 but not beyond December 31, 2003. In granting the extension, the department will set a schedule for compliance and may specify any interim measures that the system must take. Failure to meet the schedule or interim treatment requirements constitutes a violation of the drinking water regulations.
   5. (E) Beginning September 1 2000, any water treatment plant proposed for construction or major modification must be designed to meet the disinfection by-product MCLs of 0.080 for TTHM, 0.060 for HAA5, 0.010 for bromate, and 1.0 for chlorite and the requirements of sections (3) and (4) of this rule.

2. (2) Compliance with the TTHM MCL of 0.10.

   1. (A) A supplier of water must collect samples of the product water for analyses as follows:

      1. 1. Community water systems must per-

form sampling at quarterly intervals.

1. A. Analyses for TTHM shall be per-

formed at quarterly intervals on at least four (4) water samples for each treatment plant used by the system.

1. B. The minimum number of samples

required shall be based on the number of treatment plants used by the system except that multiple wells drawing raw water from a single aquifer, with the department’s approval, may be considered one (1) treat- Oct. 11, 1981 to TTHM 0.10 Dec. 31, 2001

ment plant for determining the minimum number of samples.

1. C. Community water systems serving

fewer than ten thousand (10,000) persons, at the discretion of the department, may be required to submit fewer samples; and

1. 2. All samples taken within an estab-

lished frequency shall be collected within a twenty-four (24)-hour period.

1. (B) At least twenty-five percent (25%) of the samples shall be taken at locations within the distribution system reflecting the maximum residence time of the water in the system. The remaining shall be taken at representative locations in the distribution system, taking into account the number of persons served, different sources of water and different treatment methods employed.
2. (C) The results of all analyses per quarter shall be arithmetically averaged and all samples collected shall be used in the computation of the average.

3. (D) Upon a community water system’s written request, the department may reduce the TTHM analysis monitoring frequency to a minimum of one (1) sample per quarter.

   1. 1. The sample shall be taken at a point

in the distribution system that reflects the maximum residence time of the water in the system.

1. 2. The department shall provide, in writ-

ing, a determination that local conditions and data from at least one (1) year of monitoring in accordance with subsection (2)(A) of this rule demonstrate that TTHM concentrations will be consistently below the MCL. Section (2)

1. 3. The supplier of water immediately

shall begin monitoring in accordance with the requirements of subsection (2)(A) of this rule upon finding that—

1. A. At any time during the reduced

monitoring, the results from any analysis for TTHM exceed 0.10 milligrams per liter (mg/l) and the results are confirmed by at least one (1) check sample taken promptly after the results are received; or

1. B. The system makes any significant

change(s) to its source of water or treatment process; and

1. C. This monitoring shall continue at

least one (1) year before the frequency may be reduced again.

1. (E) Upon the written request of a community water system that utilizes only groundwater sources, the department may allow the water system to substitute a minimum of one

1. (1) sample per year for maximum TTHM potential in place of quarterly sampling for TTHM.

   1. 1. This monitoring frequency applies

separately to each treatment plant used in the system.

1. 2. The sample shall be taken at a point

in the distribution system that reflects the maximum residence time of the water in the system.

1. 3. The department shall provide, in writ-

ing, a determination that—

1. A. The system has a maximum

TTHM potential of less than 0.10 mg/l based upon data submitted by the water supplier; and

1. B. Based upon an assessment of local

conditions, the system is not likely to approach or exceed the MCL for TTHM.

1. 4. A water supplier immediately shall

begin monitoring in accordance with the requirements of subsection (2)(A) of this rule upon finding that—

1. A. The results from any analysis

taken by the water supplier for maximum TTHM potential are equal to or greater than 0.10 mg/l; and

1. B. The results are confirmed by at

least one (1) check sample which was taken promptly after the results were received; and

1. C. This monitoring shall continue for

at least one (1) year before the frequency may be reduced again.

1. 5. If the system makes any significant

change(s) in the raw water or treatment program at any time during the period of reduced monitoring frequency, the water supplier immediately shall collect an additional sample to be analyzed for maximum TTHM potential. The sample shall be taken at a point in the distribution system that reflects the maximum residence time of the water in the system. The results of the analysis shall be used to determine whether the system must comply with the monitoring requirements of subsection (2)(A) of this rule.

1. (F) Compliance with the MCL of 0.10 for TTHM shall be determined based on a running annual average of quarterly samples collected by the supplier of water as prescribed in subsection (2)(A). If the average of samples covering any twelve (12)-month period exceeds the MCL, the supplier of water shall report to the department pursuant to 10 CSR 60-7.010 and notify the public pursuant to 10 CSR 60-8.010. Monitoring after public notification shall be at a frequency designated by the department and shall continue until a monitoring schedule as a condition to a variance, exemption or enforcement action shall become effective.
2. (G) Samples for TTHM shall be dechlorinated upon collection to prevent further production of trihalomethanes. Samples for maximum TTHM potential shall not be dechlorinated and must be held for seven (7) days at twenty-five degrees Celsius (25°C) prior to analysis.
3. (H) At the option of the department, monitoring frequencies may be increased above the minimum where this is necessary to detect variations of TTHM levels within the distribution system.

4. (I) Before a community water system makes any significant modifications to its existing treatment process for the purposes of achieving compliance with this rule, the system must obtain departmental approval of its proposed modifications and those safeguards that it will implement to ensure that the microbiological quality of the drinking water served by the system will not be adversely affected by the modifications. At a minimum, the department shall require the system modifying its disinfection practice to—

   1. 1. Evaluate the source water for micro-

biological quality;

1. 2. Evaluate its existing treatment prac-

tices and consider improvements that will minimize disinfectant demand and optimize finished water quality throughout the distribution system; and

1. 3. Conduct additional monitoring and

studies as required by the department to assure continued maintenance of optimal biological quality in finished water.

1. (3) Monitoring Requirements and Plan.

   1. (A) General Requirements.

      1. 1. Systems must take all samples during

normal operating conditions.

1. 2. With department approval, systems

may consider multiple wells drawing water from a single aquifer as one treatment plant for determining the minimum number of TTHM and HAA5 samples required. The department may approve as one treatment plant—

1. A. Multiple wells located in the same

unconsolidated formation; or

1. B. Multiple wells located in the same

consolidated formation.

1. 3. Each system required to monitor

under this section (3) must develop and implement a monitoring plan. This includes systems purchasing water, unless the system is included in the seller’s monitoring plan.

1. A. The monitoring plan must include

at least the following elements:

1. (I) Specific locations and sched-

ules for collecting samples;

1. (II) How the system will calculate

compliance with MCLs, maximum residual disinfection levels (MRDLs), and treatment techniques; and

1. (III) If approved for monitoring as

a consecutive system, or if providing water to a consecutive system, under the provisions of 10 CSR 60-4.010(6), the sampling plan must reflect the entire distribution system.

1. B. The system must maintain the

monitoring plan and make it available for inspection by the department and the general public no later than thirty (30) days following the applicable compliance dates in section (1) of this rule.

1. C. All systems serving more than

three thousand three hundred (>3,300) people and using surface water or groundwater under the direct influence of surface water 10 CSR 60-4

(GWUDISW) must submit a copy of the monitoring plan to the department no later than the date of the first report required under 10 CSR 60-7.010(6). The department may also require the plan to be submitted by any other system at the department’s discretion. After review, the department may require changes in any plan elements.

1. D. Systems that purchase water must

provide a monitoring plan and meet the monitoring requirements of this section unless the purchaser is included in the seller’s monitoring plan.

1. 4. Failure to monitor in accordance with

the monitoring plan is a monitoring violation.

1. 5. Failure to monitor will be treated as

a violation for the entire period covered by the annual average where compliance is based on a running annual average of monthly or quarterly samples or averages and the system’s failure to monitor makes it impossible to determine compliance with MCLs or MRDLs.

1. 6. Systems may use only data collected

under the provisions of this section (3) or EPA’s Information Collection Rule (40 CFR Subpart M) to qualify for reduced monitoring.

1. (B) Monitoring Requirements for Disinfection By-Products.

   1. 1. TTHMs and HAA5.

      1. A. Routine monitoring. Systems must

monitor at the frequency indicated in Table 2. Table 2. Routine Monitoring Frequency for TTHM and HAA5.

Surface water or GWUDISW system serving at least 10,000 people.

Surface water or GWUDISW system serving from 500 to 9,999 people. Surface water or GWUDISW system serving fewer than 500 people.

System using only groundwater not under the direct influence of surface water using chemical disinfectant and serving at least

1If a system elects to sample more frequently than the minimum required, at least 25 percent of all samples collected each quarter (including those taken in excess of the required frequency) must be taken at locations that represent the maximum residence time of the water in the distribution system. The remaining samples must be taken at locations representative of at least average residence time in the distribution system.

2Multiple wells drawing water from a single aquifer may be considered one (1) treatment plant for determining the minimum number of samples required, with department approval.

1. B. Systems may reduce monitoring

except as otherwise provided, in accordance with Table 3. Four (4) water samples per quarter per treatment plant.

One (1) water sample per quarter per treatment plant.

One (1) sample per year per treatment plant during month of warmest water temperature.

One (1) water sample per quarter per treatment plant.2 At least 25 percent of all samples collected each quarter at locations representing maximum residence time. Remaining samples taken at locations representative of at least average residence time in the distribution system and representing the entire distribution system, taking into account number of persons served, different sources of water, and different treatment methods.1 Locations representing maximum residence time.1

Locations representing maximum residence time.1 If the sample (or average of annual samples, if more than one sample is taken) exceeds MCL, system must increase monitoring to one sample per treatment plant per quarter, taken at a point reflecting the maximum residence time in the distribution system, until system meets reduced monitoring criteria in subsection (3)(C) of this rule. Locations representing maximum residence time.1

Surface water or GWUDISW system serving at least 10,000 persons which has a source water annual average total organic carbon (TOC) level, before any

System using only groundwater not under direct influence of surface water using chemical disinfectant and serving at least

1. C. Systems on a reduced monitoring

schedule may remain on that reduced schedule as long as the average of all samples taken in the year (for systems which must monitor quarterly) or the result of the sample (for systems which must monitor no more frequently than annually) is no more than 0.060 mg/L for TTHMs and 0.045 mg/L for HAA5. Systems that do not meet these levels must resume monitoring at the frequency identified in Table 2: Routine Monitoring in the quarter immediately following the quarter in which the system exceeds 0.060 mg/L for TTHMs and 0.045 mg/L for HAA5. For systems using only groundwater under the direct influence of surface water and serving fewer than ten thousand (10,000) persons, if either the TTHM annual average is greater than 0.080 mg/L or the HAA5 annual average is greater than 0.060 mg/L, the system must go to increased monitoring. Systems on increased monitoring may return to routine monitoring TTHM annual average is less than or equal to 0.040 mg/L and HAA5 annual average is less than or equal to 0.030 mg/L. TTHM annual average ≤0.040 mg/L and HAA5 annual average ≤0.030 mg/L

TTHM annual average ≤0.040 mg/L and HAA5 annual average ≤0.030 mg/L.

1. D. The department may return a sys-

tem to routine monitoring at the department’s discretion.

1. 2. Chlorite. Community and nontran-

sient noncommunity water systems using chlorine dioxide, for disinfection or oxidation, must conduct monitoring for chlorite.

1. A. Routine monitoring.

   1. (I) Daily monitoring. Systems must

take daily samples at the entrance to the distribution system. For any daily sample that exceeds the chlorite MCL, the system must take additional samples in the distribution system the following day at the following locations: near the first customer; at a location representative of average residence time; and at a location reflecting maximum residence time in the distribution system, in addition to the sample required at the entrance to the distribution system.

1. (II) Monthly monitoring. Systems

must take a three (3)-sample set each month in the distribution system. The system must take one (1) sample at each of the following locations: near the first customer; at a location representative of average residence time; 10 CSR 60-4

One (1) sample per treatment plant per quarter at distribution system location reflecting maximum residence time.

One (1) sample per treatment plant per year at distribution system location reflecting maximum residence time during month of warmest water temperature.

and at a location reflecting maximum residence time in the distribution system. Any additional routine sampling must be conducted in the same manner (as three (3)-sample sets, at the specified locations). The system may use the results of additional monitoring conducted under subparagraph (3)(B)2.B. to meet the requirement for monthly monitoring.

1. B. Additional monitoring. On each

day following a routine sample monitoring result that exceeds the chlorite MCL at the entrance to the distribution system, the system is required to take three (3) chlorite distribution system samples at the following locations: as close to the first customer as possible, in a location representative of average residence time, and as close to the end of the distribution system as possible (reflecting maximum residence time in the distribution system).

1. C. Reduced monitoring.

   1. (I) Chlorite monitoring at the

entrance to the distribution system required by item (3)(B)2.A.(I) of this rule may not be reduced.

1. (II) Chlorite monitoring in the dis-

tribution system required by item (3)(B)2.A.(II) of this rule may be reduced to one (1) three (3)-sample set per quarter after one (1) year of monitoring where no individual chlorite sample taken in the distribution system under item (3)(B)2.A.(II) of this rule has exceeded the chlorite MCL and the system has not been required to conduct monitoring under subparagraph (3)(B)2.B. of this rule. The system may remain on the reduced monitoring schedule until either any of the three (3) individual chlorite samples taken quarterly in the distribution system under item (3)(B)2.A.(II) of this rule exceeds the chlorite MCL or the system is required to conduct monitoring under subparagraph (3)(B)2.B. of this rule, at which time the system must revert to routine monitoring.

1. 3. Bromate.

   1. A. Routine monitoring. Community

and nontransient noncommunity systems using ozone for disinfection or oxidation must take one (1) sample per month for each treatment plant in the system using ozone. Systems must take samples monthly at the entrance to the distribution system while the ozonation system is operating under normal conditions.

1. B. Reduced monitoring. Systems

required to analyze for bromate may reduce monitoring from monthly to once per quarter, if the system demonstrates that the average source water bromide concentration is less than 0.05 mg/L based upon representative monthly bromide measurements for one (1) year. The system may remain on reduced bromate monitoring until the running annual average source water bromide concentration, computed quarterly, is equal to or greater than 0.05 mg/L based upon representative monthly measurements. If the running annual average source water bromide concentration is greater than or equal to 0.05 mg/L, the system must resume routine monitoring.

1. (C) Monitoring Requirements for Disinfectant Residuals.

   1. 1. Chlorine and chloramines.

      1. A. Routine monitoring. Community

and nontransient noncommunity water systems must measure the residual disinfectant level at the same points in the distribution system and at the same time as total coliforms are sampled, as specified in 10 CSR 60- 4.020. System using surface water or groundwater under the direct influence of surface water may use the results of residual disinfectant concentration sampling conducted under 10 CSR 60-4.080(3) and 10 CSR 60- 4.055(4), in lieu of taking separate samples.

1. B. Reduced monitoring. Monitoring

may not be reduced.

1. 2. Chlorine dioxide.

   1. A. Routine monitoring. Community,

nontransient noncommunity, and transient noncommunity water systems that use chlorine dioxide for disinfection or oxidation must take daily samples at the entrance to the distribution system. For any daily sample that detects chlorine dioxide, the system must take additional samples in the distribution system the following day, in addition to the sample required at the entrance to the distribution system.

1. B. Additional monitoring. On each

day following a routine sample monitoring result that detects chlorine dioxide, the system is required to take three (3) chlorine dioxide distribution system samples as close to the first customer as possible, at intervals of at least six (6) hours. If chloramines are used to maintain a disinfectant residual in the distribution system, or if chlorine is used to maintain a disinfectant residual in the distribution system and there are no disinfection addition points after the entrance to the distribution system (that is, no booster chlorination), the system must take three (3) samples as close to the first customer as possible, at intervals of at least six (6) hours. If chlorine is used to maintain a disinfectant residual in the distribution system and there are one (1) or more disinfection addition points after the entrance to the distribution system (that is, booster chlorination), the system must take one (1) sample at each of the following locations: as close to the first customer as possible; in a location representative of average residence time; and as close to the end of the distribution system as possible (reflecting maximum residence time in the distribution system).

1. C. Reduced monitoring. Chlorine

dioxide monitoring may not be reduced.

1. (D) Monitoring Requirements for Disinfection By-Product Precursors (DBPP).

   1. 1. Routine monitoring. Systems using

surface water or groundwater under the direct influence of surface water and using conventional filtration treatment must monitor each treatment plant for total organic carbon (TOC) no later than the point of combined filter effluent turbidity monitoring and representative of the treated water. These systems must also monitor for TOC in the source water prior to any treatment at the same time as monitoring for TOC in the treated water. These samples (source water and treated water) are referred to as paired samples. At the same time as the source water sample is taken, all systems must monitor for alkalinity in the source water prior to any treatment. Systems must take one (1) paired sample and one (1) source water alkalinity sample per month per plant at a time representative of normal operating conditions and influent water quality.

1. 2. Reduced monitoring. Systems using

surface water or groundwater under the direct influence of surface water with an average treated water TOC of less than 2.0 mg/l for two (2) consecutive years, or less than 1.0 mg/l for one (1) year, may reduce monitoring for both TOC and alkalinity to one (1) paired sample and one (1) source water alkalinity sample per plant per quarter. The system must revert to routine monitoring in the month following the quarter when the annual average treated water TOC greater than or equal to 2.0 mg/l.

1. (E) Bromide. Systems required to analyze for bromate may reduce bromate monitoring from monthly to once per quarter, if the system demonstrates that the average source water bromide concentration is less than 0.05 mg/l based upon representative monthly measurements for one (1) year. The system must continue bromide monitoring to remain on reduced bromate monitoring.

1. (4) Compliance Requirements.

   1. (A) General Requirements.

      1. 1. Where compliance is based on a run-

ning annual average of monthly or quarterly samples or averages and the system fails to monitor for TTHM, HAA5, or bromate, this failure to monitor will be treated as a monitoring violation for the entire period covered by the annual average.

1. 2. Where compliance is based on a run-

ning annual average of monthly or quarterly samples or averages and the system’s failure to monitor makes it impossible to determine compliance with MRDLs for chlorine and chloramines, this failure to monitor will be treated as a monitoring violation for the entire period covered by the annual average.

1. 3. All samples taken and analyzed under

the provisions of this rule must be included in determining compliance, even if that number is greater than the minimum required.

1. 4. If, during the first year of monitoring,

any individual quarter’s average will cause the running annual average of that system to exceed the MCL, the system is out of compliance at the end of that quarter.

1. (B) Disinfection By-Products.

   1. 1. TTHMs and HAA5.

      1. A. For systems monitoring quarterly,

compliance must be based on a running annual arithmetic average, computed quarterly, of quarterly arithmetic averages of all samples collected by the system as prescribed by paragraph (3)(B)1. of this rule.

1. B. For systems monitoring less fre-

quently than quarterly, systems demonstrate compliance if the average of samples taken that year under the provisions of paragraph (3)(B)1. of this rule does not exceed the MCL. If the average of these samples exceeds the MCL, the system must increase monitoring to once per quarter per treatment plant. The system is not in violation until it has completed one (1) year of quarterly monitoring, unless the result of fewer than four (4) quarters of monitoring will cause the running annual average to exceed the MCL, in which case the system is in violation at the end of that quarter. Systems required to increase to quarterly monitoring must calculate compliance by including the sample that triggered the increased monitoring plus the following three (3) quarters of monitoring.

1. C. If the running annual arithmetic

average of quarterly averages covering any consecutive four-quarter period exceeds the MCL, the system is in violation of the MCL and must notify the public pursuant to 10 CSR 60-8.010 addition to reporting to the department pursuant to 10 CSR 60-7.010.

1. D. If a public water system fails to

complete four (4) consecutive quarters of monitoring, compliance with the MCL for the last four-quarter compliance period must be based on an average of the available data.

1. 2. Bromate. Compliance must be based

on a running annual arithmetic average, computed quarterly, of monthly samples (or, for months in which the system takes more than one sample, the average of all samples taken during the month) collected by the system as prescribed by paragraph (3)(B)3. of this rule. If the average of samples covering any consecutive four-quarter period exceeds the MCL, the system is in violation of the MCL and must notify the public pursuant to 10 CSR 60-8.010, in addition to reporting to the department pursuant to 10 CSR 60-7.010. If a PWS fails to complete twelve (12) consecutive months’ monitoring, compliance with the MCL for the last four (4)-quarter compliance period must be based on an average of the available data.

1. 3. Chlorite. Compliance must be based

on an arithmetic average of each three (3) sample set taken in the distribution system as prescribed by item (3)(B)2.A.(II) and subparagraph (3)(B)2.B. of this rule. If the arithmetic average of any three (3) sample set exceeds the MCL, the system is in violation of the MCL and must notify the public pursuant to 10 CSR 60-8.010, in addition to reporting to the department pursuant to 10 CSR 60-7.010.

1. (C) Disinfectant Residuals.

   1. 1. Chlorine and chloramines.

      1. A. Compliance must be based on a

running annual arithmetic average, computed quarterly, of monthly averages of all samples collected by the system under paragraph (3)(C)1. of this rule. If the average covering any consecutive four (4)-quarter period exceeds the MRDL, the system is in violation of the MRDL and must notify the public pursuant to 10 CSR 60-8.010, in addition to reporting to the department pursuant to 10 CSR 60-7.010.

1. B. In cases where systems switch

between the use of chlorine and chloramines for residual disinfection during the year, compliance must be determined by including together all monitoring results of both chlorine and chloramines in calculating compliance. Reports submitted pursuant to 10 CSR 60-7.010(6) must clearly indicate which residual disinfectant was analyzed for each sample.

1. 2. Chlorine dioxide.

   1. A. Acute violations. Compliance must

be based on consecutive daily samples collected by the system under paragraph (3)(C)2. of this rule. If any daily sample taken at the entrance to the distribution system exceeds the MRDL, and on the following day one (1) (or more) of the three (3) samples taken in the distribution system exceed the MRDL, the system is in violation of the MRDL and must take immediate corrective action to lower the level of chlorine dioxide below the MRDL and must notify the public pursuant to the procedures for acute health risks in 10 CSR 60-8.010(1)(A)3., in addition to reporting to the department pursuant to 10 CSR 60-7.010. Failure to take samples in the distribution system the day following an exceedance of the chlorine dioxide MRDL at the entrance to the distribution system will also be considered an MRDL violation and the system must notify the public of the violation in accordance with the provisions for acute violations under 10 CSR 60-8.010(1)(A)3., in addition to reporting to the department pursuant to 10 CSR 60- 7.010.

1. B. Nonacute violations. Compliance

must be based on consecutive daily samples collected by the system in compliance with this rule.

1. (I) If any two (2) consecutive daily

samples taken at the entrance to the distribution system detect chlorine dioxide, the system must take corrective action to lower the chlorine dioxide level.

1. (II) If any two (2) consecutive daily

samples taken at the entrance to the distribution system exceed the MRDL and all distribution system samples taken are below the MRDL, the system is in violation of the MRDL and must take corrective action to lower the level of chlorine dioxide below the MRDL at the point of sampling and notify 10 CSR 60-4

the public pursuant to the procedures for nonacute health risks in 10 CSR 60- 8.010(7)(D), in addition to reporting to the department pursuant to 10 CSR 60-7.010. Failure to monitor at the entrance to the distribution system the day following an exceedance of the chlorine dioxide MRDL at the entrance to the distribution system is also an MRDL violation and the system must notify the public of the violation in accordance with the provisions for nonacute violations in 10 CSR 60-8.010(7)(D), in addition to reporting to the department pursuant to 10 CSR 60- 7.010.

1. (D) Disinfection By-Product Precursors (DBPP).

   1. 1. Systems using surface water or

groundwater under the direct influence of surface water and using conventional filtration treatment must operate with enhanced coagulation or enhanced softening to achieve the TOC percent removal levels specified in this rule unless the system meets at least one (1) of the alternative compliance criteria listed here. These systems must still comply with monitoring requirements in sections (3)–(4) of this rule. The alternative compliance criteria for enhanced coagulation and enhanced softening are:

1. A. The system’s source water TOC

level, measured according to 10 CSR 60- 5.010, is less than 2.0 mg/L, calculated quarterly as a running annual average;

1. B. The system’s treated water TOC

level, measured according to 10 CSR 60- 5.010, is less than 2.0 mg/L, calculated quarterly as a running annual average;

1. C. The system’s source water TOC

level, measured according to 10 CSR 60- 5.010, is less than 4.0 mg/L, calculated quarterly as a running annual average; the source water alkalinity, measured according to 10 CSR 60-5.010, is greater than 60 mg/L (as CaCO3), calculated quarterly as a running annual average; and either the TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively; or prior to the effective date for compliance with this rule, the system has made a clear and irrevocable financial commitment not later than the effective date for compliance with this rule to use of technologies that will limit the levels of TTHMs and HAA5 to no more than 0.040 mg/L and 0.030 mg/L, respectively. Systems must submit evidence of a clear and irrevocable financial commitment, in addition to a schedule containing milestones and periodic progress reports for installation and operation of appropriate technologies, to the department for approval not later than the effective date for compliance with this rule. These technologies must be installed and operating not later than June 30, 2005. Failure to install and operate these technologies by the date in the approved schedule will constitute a violation;

1. D. The TTHM and HAA5 running

annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively, and the system uses only chlorine for primary disinfection and maintenance of a residual in the distribution system;

1. E. The system’s source water SUVA,

prior to any treatment and measured monthly according to 10 CSR 60-5.010, is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average. SUVA refers to Specific Ultraviolet Absorption at two-hundred-fifty-four nanometers (254nm), an indicator of the humic content of water. It is a calculated parameter obtained by dividing a sample’s ultraviolet absorption at a wavelength of 254nm (UV254) (in m=1) by its concentration of dissolved organic carbon (DOC) (in mg/L); and

1. F. The system’s finished water SUVA,

measured monthly according to 10 CSR 60- 5.010, is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.

1. 2. Additional alternative compliance cri-

teria for softening systems. Systems practicing enhanced softening that cannot achieve the Step 1 TOC removals may use the alternative compliance criteria listed here in lieu of complying with paragraph (4)(D)3. of this rule. Systems must still comply with monitoring requirements in sections (3)–(4) of this rule.

1. A. Softening that results in lowering

the treated water alkalinity to less than 60 mg/L (as CaCO3), measured monthly according to 10 CSR 60-5.010 and calculated quarterly as a running annual average.

1. B. Softening that results in removing

at least 10 mg/L of magnesium hardness (as CaCO3), measured monthly and calculated quarterly as an annual running average.

1. 3. Enhanced coagulation and enhanced

softening performance requirements.

1. A. Systems must achieve the percent

reduction of TOC specified in Table 4 between the source water and the combined filter effluent, unless the department approves a system’s request for alternate minimum TOC removal (Step 2) requirements. Systems may begin monitoring to determine whether Step 1 TOC removals can be met twelve (12) months prior to the compliance date for the system. This monitoring is not required and failure to monitor during this period is not a violation. However, any system that does not monitor during this period, and then determines in the first twelve (12) months after the compliance date that it is not able to meet the Step 1 requirements and must therefore apply for alternate minimum TOC removal (Step 2) requirements, is not eligible for retroactive approval of alternate minimum TOC removal (Step 2) requirements and is in violation. Systems may apply for alternate minimum TOC removal (Step 2) requirements any time after the compliance date.

1. B. Required Step 1 TOC reductions,

indicated in the following table, are based upon specified source water parameters measured in accordance with 10 CSR 60-5.010. Systems practicing softening are required to meet the Step 1 TOC reductions in the farright column (Source water alkalinity >120 mg/L) for the specified source water TOC.

Table 4: Required Step 1 TOC Reduction

Step 1 Required Removal of TOC by Enhanced Coagulation and Enhanced Softening for Surface Water and GWUDISW Systems Using Conventional Treatment1,2 Source water alkalinity, mg/L as CaCO3 Source water TOC, mg/l 0–60 >60–120 >1203 >2.0–4.0 35.0% 25.0% 15.0% >4.0–8.0 45.0% 35.0% 25.0% >8.0 50.0% 40.0% 30.0%

1Systems meeting at least one of the conditions in paragraph (4)(D)1. of this rule are not required to operate with enhanced coagulation. 2Softening systems meeting one of the alternative compliance criteria in paragraph (4)(D)1. of this rule are not required to operate with enhanced softening. 3Systems practicing softening must meet the TOC removal requirements in this column.

1. C. Conventional treatment systems

using surface water or groundwater under the direct influence of surface water that cannot achieve the Step 1 TOC removals due to water quality parameters or operational constraints must apply to the department, within three (3) months of failure to achieve the Step 1 TOC removals, for approval of alternative minimum TOC (Step 2) removal requirements submitted by the system. If the department approves the alternative minimum TOC removal (Step 2) requirements, the department may make those requirements retroactive for the purposes of determining compliance. Until the department approves the alternate minimum TOC removal (Step 2) requirements, the system must meet the Step 1 TOC removals.

1. D. Alternate minimum TOC removal

(Step 2) requirements. Applications made to the department by enhanced coagulation systems for approval of alternative minimum TOC removal (Step 2) requirements under subparagraph (4)(D)3.C. of this rule must include, as a minimum, results of benchor pilot-scale testing conducted under this subparagraph (4)(D)3.D. and used to determine the alternate enhanced coagulation level.

1. (I) Alternate enhanced coagulation

level is defined as coagulation at a coagulant dose and pH as determined by the method described here such that an incremental addition of ten (10) mg/L of alum (or equivalent amount of ferric salt) results in a TOC removal of less than or equal to 0.3 mg/L. The percent removal of TOC at this point on the “TOC removal versus coagulant dose” curve is then defined as the minimum TOC removal required for the system. Once approved by the department, this minimum requirement supersedes the minimum TOC removal required by Table 4 of this rule. This requirement will be effective until such time as the department approves a new value based on the results of a new benchand pilot-scale test. Failure to achieve department-set alternative minimum TOC removal levels is a violation.

1. (II) Benchor pilot-scale testing of

enhanced coagulation must be conducted by using representative water samples and adding 10 mg/L increments of alum (or equivalent amounts of ferric salt) until the pH is reduced to a level less than or equal to the enhanced coagulation Step 2 target pH shown in Table 5.

Table 5: Enhanced Coagulation Step 2 Target pH

Target pH

Alkalinity (mg/l as CaCO3)

0–60 5.5 >60–120 6.3 >120–240 7.0 >240 7.5

1. (III) For waters with alkalinities of

less than sixty (60) mg/L for which addition of small amounts of alum or equivalent addition of iron coagulant drives the pH below 5.5 before significant TOC removal occurs, the system must add necessary chemicals to maintain the pH between 5.3 and 5.7 in samples until the TOC removal of 0.3 mg/L per 10 mg/L alum added (or equivalent addition of iron coagulant) is reached.

1. (IV) The system may operate at

any coagulant dose or pH necessary (consistent with other regulatory requirements) to achieve the minimum TOC percent removal approved under subsection (3)(C) of this rule.

1. (V) If the TOC removal is consis-

tently less than 0.3 mg/L of TOC per 10 mg/L of incremental alum dose at all dosages of alum (or equivalent addition of iron coagulant), the water is deemed to contain TOC not amenable to enhanced coagulation. The system may then apply to the department for a waiver of enhanced coagulation requirements.

1. 4. Compliance calculations.

   1. A. Systems using surface water or

groundwater under the direct influence of surface water, other than those identified in paragraphs (4)(D)1. or 2. of this rule, must comply with requirements contained in subparagraph (4)(D)3.B. of this rule. Systems must calculate compliance quarterly, beginning after the system has collected twelve (12) months of data, by determining an annual average using the following method:

1. (I) Determine actual monthly TOC

percent removal, equal to: (1 – (treated water TOC/source water TOC)) × 100;

1. (II) Determine the required month-

ly TOC percent removal;

1. (III) Divide the value in part

(4)(D)4.A.(I) by the value in part (4)(D)4.A(II); and

1. (IV) Add together the results of

part (4)(D)4.A.(III) for the last twelve (12) months and divide by twelve (12). If the value calculated is less than 1.00, the system is not in compliance with the TOC percent removal requirements.

1. B. Systems may use the following

provisions in lieu of the calculations in subparagraph (4)(D)4.A. of this rule to determine compliance with TOC percent removal requirements:

1. (I) In any month that the system’s

treated or source water TOC level, measured according to 10 CSR 60-5.010, is less than 2.0 mg/l, the system may assign a monthly value of 1.0 (in lieu of the value calculated in part (4)(D)4.A.(III) of this rule);

1. (II) In any month that a system

practicing softening removes at least 10 mg/L of magnesium hardness (as CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in part (4)(D)4.A.(III) of this rule);

1. (III) In any month that the system’s

source water SUVA, prior to any treatment and measured according to 10 CSR 60-5.010, is less than or equal to 2.0 L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value calculated in part (4)(D)4.A.(III) of this rule);

1. (IV) In any month that the system’s

finished water SUVA, measured according to 10 CSR 60-5.010, is less than or equal to 2.0 L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value calculated in part (4)(D)4.A.(III) of this rule); and

1. (V) In any month that a system

practicing enhanced softening lowers alkalinity below sixty (60) mg/L (as CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in part (4)(D)4.A.(III) of this rule).

1. C. Systems using conventional treat-

ment and surface water or groundwater under the direct influence of surface water may also comply with the requirements of this rule by meeting the criteria in paragraph (4)(D)1. or 2. of this rule.

AUTHORITY: section 640.100, RSMo Supp. 1999.* Original rule filed April 14, 1981, effective Oct. 11, 1981. Amended: Filed Feb. 1, 1996, effective Oct. 30, 1996. Amended: Filed Dec. 15, 1999, effective Sept. 1, 2000. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999.