Disinfectant Residuals, Disinfection Byproduct Precursors and the Stage 2 Disinfectants/Disinfection Byproducts Rule

PURPOSE: This rule establishes monitoring and other requirements for achieving compliance with maximum contaminant levels based on locational running annual averages for certain disinfection byproducts and for achieving compliance with maximum residual disinfectant levels for chlorine and chloramine for certain consecutive systems. This rule incorporates the requirements of subparts L and V of 40 CFR part 141, Stage 2 Disinfectants/Disinfection Byproducts, published in the January 4, 2006, Federal Register. (1) Stage 2 Disinfectants/Disinfection Byproducts (D/DBP) Rule General Requirements. (A) The requirements of this rule constitute national primary drinking water regulations. This rule establishes monitoring and other requirements for achieving compliance with maximum contaminant levels based on locational running annual averages (LRAA) for total trihalomethanes (TTHM) and haloacetic acids five (HAA5), and for achieving compliance with maximum residual disinfectant residuals for chlorine and chloramine for certain consecutive systems. (B) Applicability. This rule applies to community water systems and nontransient noncommunity water systems that use a primary or residual disinfectant other than ultraviolet light or deliver water that has been treated with a primary or residual disinfectant other than ultraviolet light. (C) Community water systems and nontransient noncommunity water systems must comply with maximum residual disinfectant levels (MRDLs), monitoring and compliance requirements of this rule, and the MCLs of 0.080 mg/L for total triahalomethanes (TTHM), 0.060 mg/L for haloacetic acids (five) (HAA5), 0.010 mg/L for bromate, and 1.0 mg/L for chlorite. (2) Monitoring Requirements. (A) Disinfectant Residuals, Chlorite, and Bromate Monitoring Requirements. 1. Chlorine and chloramines. 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 604.022. Systems using surface water or ground water 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 604.055(4), in lieu of taking separate samples. B. Reduced monitoring. Monitoring may not be reduced. 2. Chlorine dioxide. 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. 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). C. Reduced monitoring. Chlorine dioxide monitoring may not be reduced. 3. Chlorite. A. Routine monitoring. Community and nontransient noncommunity water systems using chlorine dioxide, for disinfection or oxidation, must conduct monitoring for chlorite. (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. (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; 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 the following subparagraph (2)(A)3.B. to meet the requirement for monthly monitoring. 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). C. Reduced monitoring. (I) Chlorite monitoring at the entrance to the distribution system required by part (2)(A)3.A.(I) of this rule may not be reduced. (II) Chlorite monitoring in the distribution system required by part (2)(A)3.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 part (2)(A)3.A.(II) of this rule has exceeded the chlorite MCL and the system has not been required to conduct monitoring under subparagraph (2)(A)3.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 part (2)(A)3.A.(II) of this rule exceeds the chlorite MCL or the system is required to conduct monitoring under subparagraph (2)(A)3.B. of this rule, at which time the system must revert to routine monitoring. 4. Bromate. 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. B. Reduced monitoring. A system required to analyze for bromate may reduce monitoring from monthly to quarterly, if the system’s running annual average bromate concentration is less than or equal to 0.0025 mg/L based on monthly bromate measurements for the most recent four (4) quarters, with samples analyzed using Method 317.0 Revision 2.0, 326.0, or 321.8. If a system has qualified for reduced bromate monitoring, that system may remain on reduced monitoring as long as the running annual average of quarterly bromate samples is ≤0.0025 mg/L based on samples analyzed using Method 317.0 Revision 2.0, 326.0, or 321.8. If the running annual average bromate concentration is >0.0025 mg/L, the system must resume routine monitoring required by subparagraph (2)(A)4.A. of this rule. (B) Disinfection Byproduct Precursors (DBPP) Monitoring Requirements. 1. Total Organic Carbon (TOC). A. Routine Monitoring. Systems using surface water or ground water 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. B. Reduced monitoring. Systems using surface water or ground water 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. 2. 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. (C) Total Trihalomethane and Haloacetic Acid Monitoring Requirements. 1. General Requirements. A. Undisinfected systems that begins using a disinfectant other than ultraviolet (UV) light must consult with the department to identify compliance monitoring locations for this rule. Systems must then develop a monitoring plan that includes those monitoring locations. B. Stage 2 D/DBP Compliance Monitoring Plan. (I) Developing and implementing a monitoring plan. The system must develop and implement a monitoring plan to be kept on file for department and public review. Unless otherwise directed by the department, the monitoring plan must contain the following elements and be complete no later than the date initial monitoring under this rule is conducted: (a) Monitoring locations; (b) Monitoring dates; (c) Compliance calculation procedures; and (d) Monitoring plans for any other systems in the combined distribution system if the department has reduced monitoring requirements. (II) The system must identify which locations to use for Stage 2 D/DBP rule compliance monitoring by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of Stage 2 D/DBP rule compliance monitoring locations have been identified. (III) The system must submit a copy of the monitoring plan to the department prior to the date the system conducts the initial monitoring under this rule. (IV) A system may revise the monitoring plan to reflect changes in treatment, distribution system operations and layout (including new service areas), or other factors that may affect TTHM or HAA5 formation, or for department-approved reasons, after consultation with the department regarding the need for changes and the appropriateness of changes. If the system changes monitoring locations, the system must replace existing compliance monitoring locations with the lowest LRAA with new locations that reflect the current distribution system locations with expected high TTHM or HAA5 levels. The department may also require modifications in the system’s monitoring plan. The system must submit a copy of the modified monitoring plan to the department prior to the date the system is required to comply with the revised monitoring plan. C. Monitoring must begin at the locations and months the system has recommended in the Stage 2 D/DBP Compliance Monitoring Plan unless the department requires other locations or additional locations after its review. D. Analytical methods. The system must use an approved method listed in 10 CSR 60-5.010 for TTHM and HAA5 analyses. Analyses must be conducted by laboratories that have received certification by Environmental Protection Agency (EPA) or the department as specified in 10 CSR 605.020. E. Additional Requirements for Consecutive Systems. If the system is a consecutive system that does not add a disinfectant but delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light, the system must comply with analytical and monitoring requirements for chlorine and chloramines in 10 CSR 605.010 and 10 CSR 60-4.055(4)(E), the compliance requirements in 10 CSR 604.094(3)(B.)1. and report monitoring results under 10 CSR 60-7.010(5)(B). 2. Reduced Monitoring. A. Monitoring requirements for source water TOC. In order to qualify for reduced monitoring for TTHM and HAA5, surface water and ground water under the direct influence of surface water (GWUDISW) systems not monitoring under the TOC reduced monitoring provisions, must take monthly TOC samples every thirty (30) days at a location prior to any treatment. Once qualified for reduced monitoring for TTHM and HAA5, a system may reduce source water TOC monitoring to quarterly TOC samples taken every ninety (90) days at a location prior to any treatment. B. The system may reduce monitoring any time the LRAA is ≤0.040 mg/L for TTHM and ≤0.030 mg/L for HAA5 at all monitoring locations. In addition, the source water annual average TOC level, before any treatment, must be ≤4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water. 6WDJH''%35RXWLQH0RQLWRULQJ       6RXUFHZDWHUW\SH      3RSXODWLRQVL]HFDWHJRU\     0RQLWRULQJ )UHTXHQF\ 'LVWULEXWLRQ V\VWHP PRQLWRULQJ ORFDWLRQWRWDOSHU PRQLWRULQJ SHULRG  6XUIDFHZDWHUV\VWHPRUJURXQGZDWHU XQGHUWKHGLUHFWLQIOXHQFHRIVXUIDFH ZDWHU        *URXQGZDWHU    ± ±  ± ± ± ±    ± ± ±   3HU\HDU 3HUTXDUWHU 3HUTXDUWHU  3HUTXDUWHU 3HUTXDUWHU 3HUTXDUWHU 3HUTXDUWHU 3HUTXDUWHU  3HU\HDU 3HU\HDU 3HUTXDUWHU 3HUTXDUWHU 3HUTXDUWHU                   $OOV\VWHPVPXVWPRQLWRUGXULQJPRQWKRIKLJKHVW'%3FRQFHQWUDWLRQV 6\VWHPVRQTXDUWHUO\PRQLWRULQJPXVWWDNHGXDOVDPSOHVHWVHYHU\GD\VDWHDFKPRQLWRULQJORFDWLRQH[FHSWIRUVXUIDFHZDWHU V\VWHPVRUJURXQGZDWHUXQGHUWKHGLUHFWLQIOXHQFHRIVXUIDFHZDWHUVHUYLQJ±*URXQGZDWHUV\VWHPVVHUYLQJ RQDQQXDOPRQLWRULQJPXVWWDNHGXDOVDPSOHVHWVDWHDFKPRQLWRULQJORFDWLRQ$OORWKHUV\VWHPVRQDQQXDOPRQLWRULQJDQGVXUIDFH ZDWHUV\VWHPVRUJURXQGZDWHUXQGHUWKHGLUHFWLQIOXHQFHRIVXUIDFHZDWHUVHUYLQJ±DUHUHTXLUHGWRWDNHLQGLYLGXDO77+0 DQG+$$VDPSOHVLQVWHDGRIDGXDOVDPSOHVHWDWWKHORFDWLRQZLWKWKHKLJKHVW77+0DQG+$$FRQFHQWUDWLRQVUHVSHFWLYHO\ )RUV\VWHPVVHUYLQJIHZHUWKDQILYHKXQGUHGSHRSOHRQHORFDWLRQZLWKDGXDOVDPSOHVHWSHUPRQLWRULQJSHULRGLVQHHGHG LIWKHKLJKHVW77+0DQG+$$FRQFHQWUDWLRQVRFFXUDWWKHVDPHORFDWLRQ  Source water type Population size category Monitoring Frequency1 Distribution system monitoring location per monitoring period Surface water system or ground water under the direct influence of surface water: Ground water: <500 500–3,300 3,301–9,999 10,000–49,999 50,000–249,999 250,000–999,999 1,000,000–4,999,999 •5,000,000 <500 500-9,999 10,000-99,999 100,000-499,999 •500,000 Per year Per year Per quarter Per quarter Per quarter Per quarter Per quarter Every third year Per year Per year Per quarter Per quarter Monitoring may not be reduced. 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with the highest TTHM single measurement; one at the location and during the quarter with the highest HAA5 single measurement; and 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter. 2 dual sample sets: one at the location and during the quarter with the highest TTHM single measurement; and one at the location and during the quarter with the highest HAA5 single measurement. 2 dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs. 4 dual sample sets—at the locations with the two highest TTHM and two highest HAA5 LRAAs. 6 dual sample sets—at the locations with the three highest TTHM and three highest HAA5 LRAAs. 8 dual sample sets—at the locations with the four highest TTHM and four highest HAA5 LRAAs. 10 dual sample sets—at the locations with the five highest TTHM and five highest HAA5 LRAAs. 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with the highest TTHM single measurement; one at the location and during the quarter with the highest HAA5 single measurement; and 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter. 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with the highest TTHM single measurement; one at the location and during the quarter with the highest HAA5 single measurement; and 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter. 2 dual sample sets: one at the location and during the quarter with the highest TTHM single measurement; and one at the location and during the quarter with the highest HAA5 single measurement. 2 dual sample sets; at the locations with the highest TTHM and highest HAA5 LRAAs. 4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs. Stage 2 D/DBP Reduced Monitoring 1 Systems on quarterly monitoring must take dual sample sets every 90 days. C. The system may remain on reduced monitoring as long as the TTHM LRAA ≤0.040 mg/L and the HAA5 LRAA ≤0.030 mg/L at each monitoring location (for systems with quarterly reduced monitoring) or each TTHM sample ≤0.060 mg/L and each HAA5 sample ≤0.045 mg/L (for systems with annual or less frequent monitoring). In addition, the source water annual average TOC level, before any treatment, must be ≤4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water. D. If the LRAA based on quarterly monitoring at any monitoring location exceeds either 0.040 mg/L for TTHM or 0.030 mg/L for HAA5 or if the annual (or less frequent) sample at any location exceeds either 0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or if the source water annual average TOC level, before any treatment, >4.0 mg/L at any treatment plant treating surface water or ground water under the direct influence of surface water, the system must resume routine monitoring under section 10 CSR 60-4.094(2)(C)2. or begin increased monitoring if paragraph 10 CSR 604.094(2)(C)4. applies. E. The department may return the system to routine monitoring at the department’s discretion. 3. Increased Monitoring. A. If the system is required to monitor at a particular location annually or less frequently than annually under routine or reduced monitoring of this rule, the system must increase monitoring to dual sample sets once per quarter (taken every ninety (90) days) at all locations if a TTHM sample is >0.080 mg/L or an HAA5 sample is >0.060 mg/L at any location. B. The system is in violation of the MCL when the LRAA exceeds the Stage 2 D/DBP rule MCLs in subparagraph 10 CSR 60-4.094(3)(D)3.A., calculated based on four (4) consecutive quarters of monitoring (or the LRAA calculated based on fewer than four (4) quarters of data if the MCL would be exceeded regardless of the monitoring results of subsequent quarters). The system is in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if the system fails to monitor. C. The system may return to routine monitoring once the system has conducted increased monitoring for at least four (4) consecutive quarters and the LRAA for every monitoring location is ≤0.060 mg/L for TTHM and ≤0.045 mg/L for HAA5. (3) Compliance Requirements. (A) General Requirements. 1. Where compliance is based on a locational running annual average (LRAA) or running annual average (RAA) 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. 2. 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 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. 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. 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. 5. Systems required to monitor quarterly. To comply with MCLs in paragraph 10 CSR 60-4.094(2)(C)1.the system must calculate LRAAs for TTHM and HAA5 using monitoring results collected under this rule and determine that each LRAA does not exceed the MCL. If the system fails to complete four (4) consecutive quarters of monitoring, the system must calculate compliance with the MCL based on the average of the available data from the most recent four (4) quarters. If the system takes more than one (1) sample per quarter at a monitoring location, the system must average all samples taken in the quarter at that location to determine a quarterly average to be used in the LRAA calculation. 6. Systems required to monitor yearly or less frequently. To determine compliance with the Stage 2 D/DBP MCLs in subparagraph 10 CSR 60-4.094(3)(D)3.A., the system must determine that each sample taken is less than the MCL. If any sample exceeds the MCL, the system must comply with the requirements of increased monitoring of this rule. If no sample exceeds the MCL, the sample result for each monitoring location is considered the LRAA for that monitoring location. 7. Violation. If a system fails to monitor, the system is in violation of the monitoring requirements for each quarter or monitoring period that a monitoring result would be used in calculating a LRAA for TTHM and HAA5 or RAA for bromate or chlorite. (B) Disinfectant Residuals, Chlorite, and Bromate. 1. Chlorine and chloramines. 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 (2)(A)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. 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(5) must clearly indicate which residual disinfectant was analyzed for each sample. 2. Chlorine dioxide. A. Acute violations. Compliance must be based on consecutive daily samples collected by the system under subparagraph (2)(A)2.A. 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(2), 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(2), in addition to reporting to the department pursuant to 10 CSR 60-7.010. B. Nonacute violations. Compliance must be based on consecutive daily samples collected by the system in compliance with this rule. (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. (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 the public pursuant to the procedures for nonacute health risks in 10 CSR 60-8.010(3), 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 608.010(3), in addition to reporting to the department pursuant to 10 CSR 60-7.010. (C) Disinfection Byproduct Precursors (DBPP). 1. Systems using surface water or ground water 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 and compliance requirements of this rule. The alternative compliance criteria for enhanced coagulation and enhanced softening are: A. The system’s source water TOC level, measured according to 10 CSR 605.010, is less than 2.0 mg/L, calculated quarterly as a running annual average; B. The system’s treated water TOC level, measured according to 10 CSR 605.010, is less than 2.0 mg/L, calculated quarterly as a running annual average; C. The system’s source water TOC level, measured according to 10 CSR 605.010, 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 sixty (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 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; 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; 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 (254 nm), 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 254 nm (UV254) (in m=1) by its concentration of dissolved organic carbon (DOC) (in mg/L); and F. The system’s finished water SUVA, measured monthly according to 10 CSR 605.010, is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average. 2. Additional alternative compliance criteria 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 (3)(C)3. of this rule. Systems must still comply with monitoring and compliance requirements of this rule. A. Softening that results in lowering the treated water alkalinity to less than sixty (60) mg/L (as CaCO3), measured monthly according to 10 CSR 60-5.010 and calculated quarterly as a running annual average. B. Softening that results in removing at least ten (10) mg/L of magnesium hardness (as CaCO3), measured monthly according to 10 CSR 60-5.010 and calculated quarterly as an annual running average. 3. Enhanced coagulation and enhanced softening performance requirements. A. Systems must achieve the percent reduction of TOC specified in Table 1 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. For systems required to meet Step 1 TOC removals, if the value calculated under part (3)(C)4.A.(IV) of this rule is less than 1.00, the system is in violation of the treatment technique requirements 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. 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 far right column (Source water alkalinity >120 mg/L) for the specified source water TOC. 1Systems meeting at least one (1) of the conditions in paragraph (3)(C)1. of this rule are not required to operate with enhanced coagulation. 2Softening systems meeting one (1) of the alternative compliance criteria in paragraph (3)(C)1. of this rule are not required to operate with enhanced softening. 3Systems practicing softening must meet the TOC removal requirements in this column. C. Conventional treatment systems using surface water or ground water 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 removal (Step 2) 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 7DEOH5HTXLUHG6WHS72&5HGXFWLRQ    6WHS5HTXLUHG5HPRYDORI72&E\(QKDQFHG&RDJXODWLRQDQG (QKDQFHG6RIWHQLQJIRU6XUIDFH:DWHUDQG*:8',6:6\VWHPV 8VLQJ&RQYHQWLRQDO7UHDWPHQW   6RXUFHZDWHU72&PJ/ 6RXUFHZDWHUDONDOLQLW\PJ/DV&D&2 ± !± ! !± !± !               determining compliance. Until the department approves the alternate minimum TOC removal (Step 2) requirements, the system must meet the Step 1 TOC removals. 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 (3)(C)3.C. of this rule must include, as a minimum, results of bench- or pilot-scale testing conducted under this subparagraph (3)(C)3.D. and used to determine the alternate enhanced coagulation level. (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 1 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 bench- and pilot-scale test. Failure to achieve department-set alternative minimum TOC removal levels is a violation. (II) Bench- or 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 2. (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. (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 subparagraph (3)(C)3.C. of this rule. (V) If the TOC removal is consistently 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. 4. Compliance calculations. A. Systems using surface water or ground water under the direct influence of surface water, other than those identified in paragraphs (3)(C)1. or (3)(C)2. of this rule, must comply with requirements contained in subparagraphs (3)(C)3.B. or (3)(C)3.C. 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: (I) Determine actual monthly TOC percent removal, equal to: (1 – (treated water TOC/source water TOC)) × 100; (II) Determine the required monthly TOC percent removal; (III) Divide the value in part (3)(C)4.A.(I) by the value in part (3)(C)4.A.(II); and (IV) Add together the results of part (3)(C)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. B. Systems may use the following provisions in lieu of the calculations in subparagraph (3)(C)4.A. of this rule to determine compliance with TOC percent removal requirements: (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 (3)(C)4.A.(III) of this rule); (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 (3)(C)4.A.(III) of this rule); (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 (3)(C)4.A.(III) of this rule); (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 (3)(C)4.A.(III) of this rule); and (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 (3)(C)4.A.(III) of this rule). C. Systems using conventional treatment and surface water or ground water under the direct influence of surface water may also comply with the requirements of this rule by meeting the criteria in paragraphs (3)(C)1. or (3)(C)2. of this rule. (D) Disinfection Byproducts. 1. 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 (2)(A)4. 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. 2. Chlorite. Compliance must be based on an arithmetic average of each three (3) sample set taken in the distribution system as prescribed by item (2)(A)3.C.(II) and subparagraph (2)(A)3.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. 3. Total Trihalomethane (TTHM) and Haloacetic Acid (HAA). A. Stage 2 Disinfectants/Disinfection Byproducts—Locational Running Annual Average (LRAA) Compliance. The MCLs of 0.080 mg/L for TTHM and 0.060 mg/L for HAA5 must be complied with as a locational running annual average at each monitoring location. B. If the system is required to conduct quarterly monitoring, the system must make  7DEOH(QKDQFHG&RDJXODWLRQ 6WHS7DUJHWS+  $ONDOLQLW\PJ/DV&D&2 7DUJHWS+  ! ! !      compliance calculations at the end of the fourth calendar quarter that follows the compliance date and at the end of each subsequent quarter (or earlier if the LRAA calculated based on fewer than four (4) quarters of data would cause the MCL to be exceeded regardless of the monitoring results of subsequent quarters). If the system is required to conduct monitoring at a frequency that is less than quarterly, the system must make compliance calculations beginning with the first compliance sample taken after the compliance date. C. The department may determine that the combined distribution system does not include certain consecutive systems based on factors such as receiving water from a wholesale system only on an emergency basis or receiving only a small percentage and small volume of water from a wholesale system. The department may also determine that the combined distribution system does not include certain wholesale systems based on factors such as delivering water to a consecutive system only on an emergency basis or delivering only a small percentage and small volume of water to a consecutive system. (E) Operational Evaluation Levels. 1. The system has exceeded the operational evaluation level at any monitoring location where the sum of the two (2) previous quarters of TTHM results plus twice the current quarter’s TTHM result, divided by four (4) to determine an average, exceeds 0.080 mg/L, or where the sum of the two (2) previous quarters of HAA5 results plus twice the current quarter’s HAA5 result, divided by four (4) to determine an average, exceeds 0.060 mg/L. 2. If Operational Evaluation Levels are Exceeded. A. If the system exceeds the operational evaluation level, the system must conduct an operational evaluation and submit a written report of the evaluation to the department no later than ninety (90) days after being notified of the analytical result that causes the system to exceed the operational evaluation level. The written report must be made available to the public upon request. B. The system’s operational evaluation must include an examination of system treatment and distribution operational practices, including storage tank operations, excess storage capacity, distribution system flushing, changes in sources or source water quality, and treatment changes or problems that may contribute to TTHM and HAA5 formation and what steps could be considered to minimize future exceedences. (I) The system may request and the department may allow a limit to the scope of the evaluation if the system is able to identify the cause of the operational evaluation level exceedance. (II) The system’s request to limit the scope of the evaluation does not extend the schedule in subparagraph (3)(E)2.A. of this rule for submitting the written report. The department must approve this limited scope of evaluation in writing, and the system must keep that approval with the completed report. (F) Stage 2 D/DBP Reporting and RecordKeeping Requirements. 1. Reporting requirements are found in 10 CSR 60-7.010, Reporting Requirements. 2. Record-keeping requirements are found in 10 CSR 60-9.010, Requirements for Maintaining Public Water System Records. AUTHORITY: section 640.100, RSMo 2016.* Original rule filed Feb. 27, 2009, effective Oct. 30, 2009. Amended: Filed June 13, 2018, effective Feb. 28, 2019. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999, 2002, 2006, 2012, 2014.