5 Colo. Code Regs. § 1002-11.25
Current through Register Vol. 47, No. 11, June 10, 2024
Section 5 CCR 1002-11.25 - DISINFECTION BYPRODUCTS RULE11.25(1)Total Trihalomethanes (TTHM) and Haloacetic Acids (HAA5)(a)Applicability and Definitions for TTHM and HAA5(i) For all community water systems and non-transient, non-community water systems that supply water treated with a primary or residual disinfectant other than ultraviolet light, the supplier must comply with the requirements specified in this section, 11.25(1).(ii) "DUAL SAMPLE SET" means a set of two samples collected at the same time and same location for the purposes of determining compliance with the TTHM and HAA5 MCLs. One sample is analyzed for TTHM and the other is analyzed for HAA5.(iii) "INITIAL DISTRIBUTION SYSTEM EVALUATION REPORT" or "IDSE REPORT" means a report resulting from a historical requirement where the supplier identified sampling locations that represent high TTHM and HAA5 concentrations in the distribution system. (A) IDSE Reports include: (I) Historical TTHM and HAA5 individual sampling results and LRAAs;(II) A schematic of the distribution system;(III) The population supplied;(V) A recommendation and explanation of sampling timing and locations that will represent the highest TTHM and HAA5 concentrations.(a) The supplier must include the peak historical month for TTHM and HAA5 concentrations in the recommendation, unless the Department approved another month to collect samples.(B) For new systems or reclassified systems that now meet the applicability of this rule, the supplier is not required to complete an IDSE Report.(iv) "HALOACETIC ACIDS" or "HAA5" means the sum of the concentrations in mg/L of the five regulated haloacetic acid compounds (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid), rounded to two significant figures after addition.(v) "TOTAL TRIHALOMETHANES" or "TTHM" means the sum of the concentrations in mg/L of the four regulated trihalomethane compounds (trichloromethane [chloroform], dibromochloromethane, bromodichloromethane and tribromomethane [bromoform]), rounded to two significant figures after addition.(b)MCL Requirements for TTHM and HAA5(i) The TTHM and HAA5 MCLs are as follows: TABLE 11.25-I MCLs FOR TTHM AND HAA5 |
Disinfection byproduct | MCL (mg/L) |
Total trihalomethanes (TTHM) | 0.080 |
Haloacetic acids (five) (HAA5) | 0.060 |
(ii) The BATs for achieving compliance with the MCLs for TTHM and HAA5 are specified in 40 CFR 141.64(b)(2)(ii). (iii) The BATs for achieving compliance with the MCLs for TTHM and HAA5 for consecutive systems which only apply to the disinfected water that the consecutive system buys or receives are specified in 40 CFR 141.64(b)(2)(iii).(c)Sampling Requirements for TTHM and HAA5(i) To determine compliance with the MCLs for TTHM and HAA5, the supplier must comply with the sampling requirements specified in this section, 11.25(1)(c).(ii) If the supplier submitted an IDSE report, the supplier must sample for TTHM and HAA5 at the sampling locations and in the months recommended in the IDSE report, unless the Department requires other or additional sampling locations or months. (iii) If the supplier did not submit an IDSE report, the supplier must select TTHM and HAA5 sampling locations as follows, unless the Department requires other or additional locations: (A) Alternate between selecting sampling locations that represent high TTHM concentrations and sampling locations that represent high HAA5 concentrations until the required number of sampling locations, as specified in Table 11.25-II, have been identified.(B) For systems not chemically disinfecting, if the supplier begins using a chemical disinfectant, the supplier must consult with the Department to identify TTHM and HAA5 sampling locations.(iv) For routine sampling, the supplier must sample at the number of sampling locations and at the sampling frequencies specified in Table 11.25-II. TABLE 11.25-II ROUTINE SAMPLING LOCATIONS AND FREQUENCIES
Source water type | Population supplied | Sampling frequency | Number of sampling locations and sample type |
Surface Water | <500 | annually | 1 individual sample for TTHM collected at the sampling location with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location with the highest HAA5 concentration; or 1 dual sample set if the highest TTHM and HAA5 concentrations occur at the same sampling location and in the same month. |
Surface Water | 500 - 3,300 | quarterly | 1 individual sample for TTHM collected at the sampling location with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location with the highest HAA5 concentration. |
Surface Water | 3,301 - 9,999 | quarterly | 2 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Surface Water | 10,000 - 49,999 | quarterly | 4 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Surface Water | 50,000 - 249,999 | quarterly | 8 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Surface Water | 250,000 - 999,999 | Quarterly | 12 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Surface Water | 1,000,000 - 4,999,999 | quarterly | 16 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Source water type | Population supplied | Sampling frequency | Number of sampling locations and sample type |
Surface Water | >= 5,000,000 | quarterly | 20 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Groundwater | <500 | annually | 1 individual sample for TTHM collected at the sampling location with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location with the highest HAA5 concentration; or 1 dual sample set if the highest TTHM and HAA5 concentrations occurred at the same sampling location and in the same month. |
Groundwater | 500 - 9,999 | annually | 2 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Groundwater | 10,000 - 99,999 | quarterly | 4 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Groundwater | 100,000 - 499,999 | quarterly | 6 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
Groundwater | >= 500,000 | quarterly | 8 dual sample sets at sampling locations as specified in 11.25(1)(c)(ii) or 11.25(1)(c)(iii). |
(v) For routine sampling, the supplier must collect samples during the month when the highest TTHM and HAA5 concentrations occur.(vi) For routine, reduced, or increased sampling, if the supplier is on a quarterly sampling frequency, the supplier must collect samples at least every 90 days.(vii) The supplier may reduce the sampling frequency and/or the number of sampling locations as specified in Table 11.25-III if all of the following criteria are met: (A) The LRAA for TTHM is less than or equal to ([LESS THAN EQUAL TO]) 0.040 mg/L at all sampling locations.(B) The LRAA for HAA5 is less than or equal to ([LESS THAN EQUAL TO]) 0.030 mg/L at all sampling locations.(C) For surface water systems, the LRAA of the source water TOC samples is less than or equal to ([LESS THAN EQUAL TO]) 4.0 mg/L at each surface water treatment plant. (I) If the supplier is required to sample as specified in 11.24(3), the supplier must use these TOC sample results to determine the LRAA.(II) If the supplier is not required to sample as specified in 11.24(3), the supplier must collect optional source water TOC samples every 30 days for at least 12 months and use these optional TOC sample results to determine the LRAA. (a) If the supplier chooses to sample source water TOC and the system subsequently qualifies for reduced TTHM and HAA5 sampling, the supplier must continue to sample the source water for TOC but may reduce the sampling frequency to at least every 90 days. TABLE 11.25-III REDUCED SAMPLING LOCATIONS AND FREQUENCIES
Source water type | Population supplied | Sampling frequency | Number of sampling locations and sample type |
Surface Water | <500 | The sampling may not be reduced. | The sampling cannot be reduced. |
Surface Water | 500 - 3,300 | annually | 1 individual sample for TTHM collected at the sampling location and during the quarter with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location and during the quarter with the highest HAA5 concentration; or 1 dual sample set if the highest TTHM and HAA5 concentrations occurred at the same sampling location and in the same quarter. |
Surface Water | 3,301 - 9,999 | annually | 2 dual sample sets with 1 collected at the sampling location and during the quarter with the highest TTHM concentration and 1 collected at the sampling location and during the quarter with the highest HAA5 concentration. |
Surface Water | 10,000 - 49,999 | quarterly | 2 dual sample sets collected at the sampling locations with the highest TTHM and highest HAA5 LRAAs. |
Surface Water | 50,000 - 249,999 | quarterly | 4 dual sample sets collected at the sampling locations with the 2 highest TTHM and 2 highest HAA5 LRAAs. |
Surface Water | 250,000 - 999,999 | quarterly | 6 dual sample sets collected at the sampling locations with the 3 highest TTHM and 3 highest HAA5 LRAAs. |
Surface Water | 1,000,000 - 4,999,999 | quarterly | 8 dual sample sets collected at the sampling locations with the 4 highest TTHM and 4 highest HAA5 LRAAs. |
Surface Water | >= 5,000,000 | quarterly | 10 dual sample sets collected at the sampling locations with the 5 highest TTHM and 5 highest HAA5 LRAAs. |
Groundwater | <500 | every third calendar year | 1 individual sample for TTHM collected at the sampling location and during the quarter with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location and during the quarter with the highest HAA5 concentration; or 1 dual sample set if the highest TTHM and HAA5 concentrations occurred at the same sampling location and in the same quarter. |
Groundwater | 500 - 9,999 | annually | 1 individual sample for TTHM collected at the sampling location and during the quarter with the highest TTHM concentration and 1 individual sample for HAA5 collected at the sampling location and during the quarter with the highest HAA5 concentration; or 1 dual sample set if the highest TTHM and HAA5 concentrations occurred at the same sampling location and in the same quarter. |
Groundwater | 10,000 - 99,999 | annually | 2 dual sample sets with 1 collected at the sampling location and during the quarter with the highest TTHM concentration and 1 collected at the location and during the quarter with the highest HAA5 concentration. |
Groundwater | 100,000 - 499,999 | quarterly | 2 dual sample sets at the sampling locations with the highest TTHM and highest HAA5 LRAAs. |
Groundwater | >= 500,000 | quarterly | 4 dual sample sets collected at the sampling locations with the 2 highest TTHM and 2 highest HAA5 LRAAs. |
(viii) If the supplier is sampling at a reduced sampling frequency and/or at the reduced number of sampling locations, the supplier must return to the routine sampling frequency and the routine number of sampling locations specified in Table 11.25-II if one or more of the following criteria are met: (A) For surface water systems, the LRAA of the source water TOC samples collected under 11.24(3) or 11.25(1)(c)(vii)(C)(II), is greater than (>) 4.0 mg/L at any surface water treatment plant.(B) For a supplier sampling at a quarterly sampling frequency, the TTHM LRAA is greater than (>) 0.040 mg/L or the HAA5 LRAA is greater than (>) 0.030 mg/L.(C) For a supplier sampling at an annual or less frequent sampling frequency, any individual TTHM sample is greater than (>) 0.060 mg/L or any individual HAA5 sample is greater than (>) 0.045 mg/L at any sampling location.(ix) If the supplier is sampling at an annual or less frequent sampling frequency and any individual TTHM sample result is greater than (>) 0.080 mg/L or any individual HAA5 sample result is greater than (>) 0.060 mg/L, the supplier must increase the sampling to dual sample sets collected quarterly at all sampling locations. (A) The supplier may return to routine sampling at the frequency and at the number of sampling locations specified in Table 11.25-II if all of the following criteria are met: (I) The supplier conducted increased sampling for at least four consecutive quarters.(II) The LRAA is less than or equal to ([LESS THAN EQUAL TO]) 0.060 mg/L for TTHM and less than or equal to ([LESS THAN EQUAL TO]) 0.045 mg/L for HAA5 at all sampling locations.(d)Sampling Plan for TTHM and HAA5(i) The supplier must develop and comply with a TTHM and HAA5 individual rule sampling plan as part of the system's monitoring plan specified in 11.5.(A) If the supplier submitted an IDSE report that includes all the information required by this section, 11.25(1)(d), the supplier is not required to develop the individual rule sampling plan.(B) The sampling plan must consist of all of the following: (III) Compliance calculation procedures.(IV) The rationale for identifying the sampling locations as having high concentrations of TTHM or HAA5.(V) For consecutive systems, if the Department has reduced the sampling requirements for the supplier responsible for the consecutive system under 11.42(4), the sampling plans for all other systems included in the combined distribution system.(C) The sampling plan must be complete no later than the date the supplier collects the first TTHM or HAA5 sample.(D) The supplier must keep the sampling plan on file for Department and public review.(ii) For surface water systems supplying greater than (>) 3,300 people, the supplier must submit a copy of the sampling plan no later than the date the supplier collects the first TTHM or HAA5 sample.(iii) The supplier may revise the sampling plan to reflect changes in treatment, distribution system operations and layout, other factors that may affect TTHM or HAA5 formation or for Department-approved reasons after consulting with the Department regarding the need and appropriateness of changes. (A) If the supplier revises the sampling locations, the supplier must replace the existing sampling locations with the lowest LRAA with new locations that reflect the highest expected TTHM or HAA5 concentrations.(iv) The Department may require the supplier to revise the sampling plan.(v) If the supplier revises the sampling plan, the supplier must submit a copy of the revised sampling plan before the Department-specified date that the supplier must comply with the revised sampling plan.(e)Operational Evaluation Levels for TTHM and HAA5(i) The supplier must calculate operational evaluation levels for TTHMs and HAA5s quarterly as follows: (A) The sum of the two previous quarters' TTHM results plus twice the current quarter's TTHM result, divided by 4.(B) The sum of the two previous quarters' HAA5 results plus twice the current quarter's HAA5 result, divided by 4.(ii) If the operational evaluation level is greater than (>) 0.080 mg/L for TTHM or greater than (>) 0.060 mg/L for HAA5 at any monitoring location, the supplier must:
(A) Complete an operational evaluation that includes all of the following: (I) An examination of the system's treatment and distribution operational practices for all of the following: (b) Excess storage capacity.(c) Distribution system flushing.(d) Treatment changes or failures that may contribute to TTHM and HAA5 formation.(II) Changes in sources or source water quality.(III) Steps to consider for minimizing future exceedances.(B) Submit an operational evaluation report no later than 90 days after being notified of the sample result(s) that caused the system to exceed the operational evaluation level. (I) The operational evaluation report must be made available to the public upon request.(f)Compliance Determination for TTHM and HAA5(i) If the supplier samples at a quarterly frequency, MCL compliance is based on the LRAA. (A) For new systems or reclassified systems that now meet the applicability of this rule, the supplier must calculate the LRAA after the end of the fourth quarter of required sampling or earlier if the LRAA calculated based on fewer than four quarters of data would cause the MCL to be exceeded regardless of the monitoring results of subsequent quarters.(B) If the supplier collects more than one sample in a quarter at a sampling location, the supplier must average all sample results collected in the quarter at that sampling location to determine a quarterly average to be used in the LRAA calculation instead of the individual sample results.(ii) If the supplier samples at an annual or less frequent sampling frequency, compliance is based on each individual sample result.(A) If any sample result is greater than (>) the MCL, the supplier must increase the sampling frequency to quarterly sampling as specified in 11.25(1)(c)(ix). This sample will count as the first quarterly sample. Compliance with the MCLs will be determined after the fourth quarter of required sampling.(B) For new or reclassified systems that now meet the applicability of this rule, the supplier must determine compliance beginning with the first sample collected.(g)MCL Violations for TTHM and HAA5(i) The following constitute TTHM and/or HAA5 MCL violations: (A) The LRAA at any sampling location is greater than (>) the MCL for TTHM and/or HAA5.(B) The LRAA, calculated before four consecutive quarters of samples have been collected at a sampling location, is greater than (>) the MCL for TTHM and/or HAA5 regardless of the subsequent sample results.(h)Response to MCL Violations for TTHM and HAA5(i) In the event of a TTHM and/or HAA5 MCL violation, the supplier must:(A) Notify the Department no later than 48 hours after the violation occurs.(B) Distribute Tier 2 public notice as specified in 11.33. (i)Reporting Requirements for TTHM and HAA5(i) The supplier must submit all of the following information for each sampling location no later than the 10th of the month following the end of each quarter in which the sample(s) was collected: (A) Number of samples collected during the last quarter.(B) Date each sample was collected.(C) Results of each sample collected during the last quarter.(D) If the supplier is required to sample at a quarterly frequency, LRAA(s). (I) For new systems or reclassified systems that now meet the applicability of this rule, the supplier must begin submitting the LRAA after the end of the fourth quarter that the supplier is required to sample.(E) Whether the MCL was exceeded at any sampling location.(F) Whether the operational evaluation level(s) was exceeded during the quarter. (I) If the operational evaluation level(s) was exceeded, the supplier must submit the location and date of the exceedance and the calculated operational evaluation level(s).(ii) For the supplier of a surface water system seeking to qualify for, or remain on, reduced TTHM and HAA5 sampling, the supplier must submit all of the following source water TOC information for each surface water treatment plant no later than the 10th of the month following the end of each quarter in which samples were collected: (A) Number of source water TOC samples collected each month during the last quarter.(B) Date each TOC sample was collected during the last quarter.(C) Result of each TOC sample collected during the last quarter.(D) The quarterly average of monthly TOC samples collected during the last quarter or the result of the quarterly sample.(E) The LRAA of quarterly averages.(F) Whether the LRAA was greater than (>) 4.0 mg/L.(iii) The Department may choose to complete the calculations and determine whether the MCL was violated or whether the supplier is eligible for reduced sampling instead of having the supplier report that information.11.25(2)Chlorite(a)Applicability and Definitions for Chlorite(i) For all community and non-transient, non-community water systems that use chlorine dioxide for disinfection or oxidation, the supplier must comply with the requirements specified in this section, 11.25(2), when using chlorine dioxide.(ii) "THREE-SAMPLE SET" means that one chlorite sample is collected at each of the following locations: (A) As close to the first customer as possible;(B) At a location representative of average residence time; and(C) At a location representative of maximum residence time.(b)MCL Requirement for Chlorite(i) The chlorite MCL is as follows: TABLE 11.25-IV MCL FOR CHLORITE |
Disinfection byproduct | MCL (mg/L) |
Chlorite | 1.0 |
(ii) The BATs for achieving compliance with the MCL for chlorite are specified in 40 CFR 141.64(b)(1)(ii).(c)Sampling Requirements for Chlorite(i) To determine compliance with the MCL for chlorite, the supplier must comply with the sampling requirements specified in this section, 11.25(2)(c) and as identified in the monitoring plan developed under 11.5(3)(a)(v).(ii) At each entry point that supplies water from a treatment plant using chlorine dioxide and at a time that represents normal operating conditions, the supplier must collect daily chlorite samples.(iii) In the distribution system, the supplier must collect a routine three-sample set each month.(iv) If any daily entry point sample result collected under 11.25(2)(c)(ii) is greater than (>) the chlorite MCL, the next day the supplier must collect a three-sample set in the distribution system in addition to the daily entry point sample. (A) The supplier may use the results from the three-sample set collected in the distribution system to meet the routine sampling requirement specified in 11.25(2)(c)(iii).(v) The supplier may reduce the routine three-sample set sampling frequency in the distribution system to a three-sample set each quarter if, after one year of sampling all of the following criteria are met:(A) No individual chlorite sample result collected in the distribution system was greater than (>) the chlorite MCL.(B) No daily entry point sample result was greater than (>) the chlorite MCL.(vi) If the supplier is sampling at a reduced sampling frequency in the distribution system, the supplier must return to the routine monthly sampling frequency if: (A) An individual chlorite sample in the distribution system is greater than (>) the chlorite MCL; or(B) A daily entry point sample result is greater than (>) the chlorite MCL.(d)Compliance Determination for ChloriteCompliance with the MCL for chlorite is based on the average of the results of any three-sample set collected in the distribution system under 11.25(2)(c)(iii), 11.25(2)(c)(iv), or 11.25(2)(c)(v).
(e)MCL Violation and Response for Chlorite(i) If the average of the results of any three-sample set collected in the distribution system is greater than (>) the chlorite MCL, a chlorite MCL violation occurs.(ii) In the event of a chlorite MCL violation, the supplier must: (A) Distribute Tier 2 public notice as specified in 11.33.(B) Report the violation to the Department as specified in 11.25(2)(f).(f)Reporting Requirements for Chlorite(i) The supplier must submit all of the following information no later than the 10th of the month following the end of each quarter in which samples were collected:(A) The number of entry point samples collected each month during the last quarter.(B) The location, date, and sample result of each sample (both entry point and distribution system) collected during the last quarter.(C) For each month in the quarter, the average of the results of each three-sample set collected in the distribution system.(D) Whether the MCL was violated, in which month(s) the MCL was violated, and how many times it was violated in that month(s).(ii) The Department may complete the calculations and determine whether the MCL was violated instead of having the supplier report that information.11.25(3)Bromate(a)Applicability for BromateFor all community and non-transient, non-community water systems that use ozone for disinfection or oxidation, the supplier must comply with the requirements specified in this section, 11.25(3), when using ozone.
(b)MCL Requirement for Bromate(i) The bromate MCL is as follows: TABLE 11.25-V MCL FOR BROMATE |
Disinfection byproduct | MCL (mg/L) |
Bromate | 0.010 |
(ii) The BATs for achieving compliance with the MCL for bromate are specified in 40 CFR 141.64(b)(1)(ii).(c)Sampling Requirements for Bromate(i) To determine compliance with the MCL for bromate, the supplier must comply with the sampling requirements specified in this section, 11.25(3)(c) and as identified in the monitoring plan developed under 11.5(3)(a)(v).(ii) At each entry point that supplies water from a treatment plant using ozone and at a time that represents normal operating conditions, the supplier must collect one routine samples each month.(iii) The supplier may reduce the routine sampling frequency at each entry point to one sample each quarter if, during the four most recent quarters all of the following criteria are met:(A) The LRAA of all sample results collected under 11.25(3)(c)(ii) is less than or equal to ([LESS THAN EQUAL TO]) 0.0025 mg/L.(B) Monthly samples were analyzed using Method 317.0 Revision 2.0, 326.0 or 321.8.(iv) If the supplier is sampling at a reduced sampling frequency and the LRAA of all sample results analyzed using Method 317.0 Revision 2.0, 326.0 or 321.8 is greater than (>) 0.0025 mg/L, the supplier must return to the routine monthly sampling frequency immediately.(d)Compliance Determination for Bromate(i) Compliance with the MCL for bromate is determined quarterly based on the LRAA of all monthly sample results collected. (A) If the supplier collects more than one bromate sample in a month at an entry point, the supplier must average all sample results collected that month at that entry point to get the monthly average. The supplier must use the monthly average when calculating the LRAA.(e)MCL Violation for Bromate(i) The following constitute bromate MCL violations:(A) The LRAA is greater than (>) the bromate MCL.(B) The LRAA, calculated during the first four consecutive quarters of sampling at a sampling location, is greater than (>) the MCL for bromate regardless of the subsequent sample results.(f)Response to an MCL Violation for Bromate(i) In the event of a bromate MCL violation, the supplier must:(A) Distribute Tier 2 public notice as specified in 11.33.(B) Report the violation to the Department as specified in section 11.25(3)(g).(g)Reporting Requirements for Bromate(i) The supplier must submit all of the following information no later than the 10th of the month following the end of each quarter in which samples were collected:(A) The number of samples collected during the last quarter.(B) The location, date, and sample result of each sample collected during the last quarter.(C) The LRAA of all sample results collected in the last year.(D) Whether the MCL was violated.(ii) The Department may complete the calculations and determine whether the MCL was violated, instead of having the supplier report that information.38 CR 07, April 10, 2015, effective 4/30/201541 CR 11, June 10, 2018, effective 6/30/201841 CR 23, December 10, 2018, effective 12/30/201843 CR 07, April 10, 2020, effective 4/30/202043 CR 17, September 10, 2020, effective 9/30/202045 CR 24, December 25, 2022, effective 1/14/2023