216 R.I. Code R. 216-RICR-50-05-1.8

Current through December 26, 2024

Section 216-RICR-50-05-1.8 - Disinfectant Residuals, Disinfection Byproducts, and Disinfection Byproduct Precursors

1.8.1Maximum Contaminant Levels (MCLs) for Disinfection Byproducts

A. The maximum contaminant levels (MCLs) for disinfection byproducts are as follows:

Disinfection Byproduct	MCL (mg/L)
Total Trihalomethanes (TTHM)	0.080
Haloacetic Acids (five) (HAA5)	0.060
Bromate	0.010
Chlorite	1.0

B. Compliance dates

1. Community PWS and non-transient, non-community PWS. § 1.6 PWS must comply with this Section as follows:

a. Stage 1 TTHM and HAA5-RAA Compliance. All PWS must comply with the MCLs for TTHM and HAA5 as a running annual average (RRA) until the date specified for § 1.8.10 of this Part compliance in § 1.8.10(A)(3) of this Part.

b. Stage 2 Disinfection Byproducts-LRAA Compliance. The MCLs for TTHM and HAA5 must be complied with as a locational running annual average (LRRA) at each monitoring location beginning the date specified for § 1.8.10 of this Part compliance in § 1.8.10(A)(3) of this Part.

C. Best Technology, Treatment Techniques, or Other Means for Achieving Compliance

1. The following are identified as the best technology, treatment techniques, or other means available for achieving compliance with the maximum contaminant levels for disinfection byproducts identified in § 1.8.1(A) of this Part:

a. Bromate: Control of ozone treatment process to reduce production of bromate.

b. Chlorite: Control of treatment processes to reduce disinfectant demand and control of disinfection treatment processes to reduce disinfectant levels.

2. The following are identified as the best technology, treatment techniques, or other means available for achieving compliance with the maximum contaminant levels for TTHM and HAA5 identified in § 1.8.1(A) of this Part for all PWS that disinfect their source water:

a. TTHM and HAA5: Enhanced coagulation or enhanced softening plus GAC10; or nanofiltration with a molecular weight cutoff less than or equal to 1000 daltons; or GAC20.

3. The following are identified as the best technology, treatment techniques, or other means available for achieving compliance with the maximum contaminant levels for TTHM and HAA5 identified in § 1.8.1(A) of this Part, for consecutive PWS and applies only to the disinfected water that consecutive PWS buy or otherwise receive:

a. TTHM and HAA5:

(1) Systems serving greater than or equal to 10,000: Improved distribution system and storage tank management to reduce residence time, plus the use of chloramines for disinfectant residual maintenance.

(2) Systems serving less than 10,000: Improved distribution system and storage tank management to reduce residence time.

1.8.2Maximum Residual Disinfectant Levels (MRDLs)

A. Maximum residual disinfectant levels (MRDLs) are as follows:

1. Chlorine: 4.0 (as Cl2)

2. Chloramines: 4.0 (as Cl2)

3. Chlorine dioxide: 0.8 (as ClO2)

B. Compliance Dates

1. Community PWS and non-transient non-community PWS. § 1.6 PWS serving 10,000 or more persons must comply with this Section. § 1.6 PWS serving fewer than 10,000 persons and PWSs using only groundwater not under the direct influence of surface water must comply with this Section.

2. Transient non-community PWS. § 1.6 PWS serving 10,000 or more persons and using chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL. § 1.6 PWS serving fewer than 10,000 persons and using chlorine dioxide as a disinfectant or oxidant and PWSs using only groundwater not under the direct influence of surface water and using chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL.

C. The following are identified as the best technology, treatment techniques, or other means available for achieving compliance with the maximum residual disinfectant levels identified in § 1.8.2(A) of this Part: control of treatment processes to reduce disinfectant demand and control of disinfection treatment processes to reduce disinfectant levels.

1.8.3General Requirements

A. The requirements of § 1.8 of this Part constitute the State of Rhode Island primary drinking water regulations.

1. The regulations in this Section establish criteria under which community PWS and non-transient, non-community PWS which add a chemical disinfectant to the water in any part of the drinking water treatment process must modify their practices to meet MCLs and MRDLs in §§ 1.8.1 and 1.8.2 of this Part, respectively, and must meet the treatment technique requirements for disinfection byproduct precursors in § 1.8.8 of this Part.

2. The regulations in this Section establish criteria under which transient non-community PWS that use chlorine dioxide as a disinfectant or oxidant must modify their practices to meet the MRDL for chlorine dioxide in § 1.8.2 of this Part.

3. The EPA has established MCLs for TTHM and HAA5 and treatment technique requirements for disinfection byproduct precursors to limit the levels of known and unknown disinfection byproducts which may have adverse health effects. These disinfection byproducts may include chloroform, bromodichloromethane, dibromochloromethane, bromoform, dichloroacetic acid, and trichloroacetic acid.

B. Each community PWS and non-transient non-community PWS regulated under § 1.8.3(A) of this Part, must be operated by qualified personnel who meet the requirements specified by the Director and be certified in accordance with the rules and regulations titled, "Certification of Public Drinking Water Supply Treatment and Public Water Supply Transmission and Distribution Operators" (Part 5 of this Subchapter).

C. Control of Disinfectant Residuals. Notwithstanding the MRDLs in § 1.8.2 of this Part, PWS may increase residual disinfectant levels in the distribution system of chlorine or chloramines (but not chlorine dioxide) to a level and for a time necessary to protect public health, to address specific microbiological contamination problems caused by circumstances such as, but not limited to, distribution line breaks, storm run-off events, source water contamination events, or cross-connection events.

1.8.4Analytical Requirements

A. General

1. PWS must use only the analytical method(s) specified in § 1.8.4 of this Part, and § 1.21 of this Part, or their equivalent as approved by EPA, to demonstrate compliance with the requirements of § 1.8 of this Part.

B. Disinfection Byproducts

1. PWS must measure disinfection byproducts by the methods (as modified by the footnotes) listed in § 1.21 of this Part.

2. A party approved by EPA or the Director must measure daily chlorite samples at the entrance to the distribution system.

C. Disinfectant Residuals

1. PWS must measure residual disinfectant concentrations for free chlorine, combined chlorine (chloramines), and chlorine dioxide by the methods listed in the § 1.21 of this Part.

2. If approved by the Director, PWS may also measure residual disinfectant concentrations for chlorine, chloramines, and chlorine dioxide by using DPD colorimetric test kits.

3. A party approved by EPA or the Director must measure residual disinfectant concentration.

D. Additional Analytical Methods. PWS required to analyze parameters not included in §§ 1.8.4(B) and (C) of this Part must use the following methods. A party approved by EPA or the Director must measure these parameters.

1. Alkalinity. All methods allowed in § 1.21 of this Part for measuring alkalinity.

2. Bromide. All methods allowed in § 1.21 of this Part for measuring bromide.

3. Total Organic Carbon (TOC). All methods allowed in § 1.21 of this Part for measuring total organic carbon (TOC).

4. Specific Ultraviolet Absorbance (SUVA). SUVA is equal to the UV absorption at 254 nm (UV254) (measured in m-1) divided by the dissolved organic carbon (DOC) concentration (measured as mg/L). In order to determine SUVA, it is necessary to separately measure UV254 and DOC. When determining SUVA, PWSs must use the methods stipulated in § 1.21 of this Part

5. pH. All methods allowed in § 1.21 of this Part for measuring pH.

6. Magnesium. All methods allowed in § 1.21 of this Part for measuring magnesium.

1.8.5Monitoring Requirements

A. General Requirements

1. PWS must take all samples during normal operating conditions.

2. PWS may consider multiple wells drawing water from a single aquifer as one (1) treatment plant for determining the minimum number of TTHM and HAA5 samples required, with approval of the Director in accordance with criteria developed by the Director.

3. Failure to monitor in accordance with the monitoring plan required under § 1.8.5(F) of this Part, is a monitoring violation.

4. 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 PWS's failure to monitor makes it impossible to determine compliance with MCLs or MRDLs.

5. PWS may use only data collected under the provisions of this Section subpart or the Information Collection Rule known as subpart M of 40 C.F.R. § 141 to qualify for reduced monitoring.

B. Monitoring Requirements for Disinfection Byproducts

1. TTHMs and HAA5

a. Routine monitoring. PWS must monitor at the frequency indicated in the following table. Multiple wells drawing water from a single aquifer may be considered one (1) treatment plant for determining the minimum number of samples required, with Director approval in accordance with criteria developed by the Director:

Routine Monitoring Frequency for TTHM and HAA5
Type Of PWS	Minimum Monitoring Frequency	Sample Location in The Distribution System
§ 1.6 PWS serving at least 10,000 persons.	Four (4) water samples per quarter per treatment plant.	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. If a PWS elects to sample more frequently than the minimum required, at least twenty-five percent (25%) 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.
§ 1.6 PWS serving from 500 to 9,999 persons.	One (1) water sample per quarter per treatment plant.	Locations representing maximum residence time.
§ 1.6 PWS serving fewer than 500 persons.	One (1) sample per year per treatment plant during month of warmest water temperature.	Locations representing maximum residence time. If the sample (or average of annual samples, if more than one (1) sample is taken) exceeds the MCL, the PWS must increase monitoring to one (1) sample per treatment plant per quarter, taken at a point reflecting the maximum residence time in the distribution system, until the PWS meets criteria in § 1.8.5(B)(1)(d) of this Part.
PWS using only groundwater not under direct influence of surface water using chemical disinfectant and serving at least 10,000 persons.	One (1) water sample per quarter per treatment plant.	Locations representing maximum residence time.
PWS using only groundwater not under direct influence of surface water using chemical disinfectant and serving fewer than 10,000 persons.	One (1) water sample per year per treatment plant during month of warmest water temperature.	Locations representing maximum residence time. If the sample (or average of annual samples, if more than one (1) sample is taken) exceeds the MCL, the PWS must increase monitoring to one (1) sample per treatment plant per quarter, taken at a point reflecting the maximum residence time in the distribution system, until the PWS meets criteria in § 1.8.5(B)(1)(d) of this Part.

b. PWS may reduce monitoring, except as otherwise provided, in accordance with the following table:

Reduced Monitoring Frequency for TTHM and HAA5
If You Are A...	You May Reduce Monitoring If You Have Monitored At Least One (1) Year And Your...	To This Level
§ 1.6 PWS serving at least 10,000 persons which has a source water annual average TOC level, before any treatment, [LESS THAN OR EQUAL TO]4.0 mg/L.	TTHM annual average [LESS THAN OR EQUAL TO]0.040 mg/L and HAA5 annual average [LESS THAN OR EQUAL TO]0.030 mg/L.	One (1) sample per treatment plant per quarter at distribution system location reflecting maximum residence time.
§ 1.6 PWS serving from 500 to 9,999 persons which has a source average TOC level, before any treatment, [LESS THAN OR EQUAL TO]4.0 mg/L.	TTHM annual average [LESS THAN OR EQUAL TO]0.040 mg/L and HAA5 [LESS THAN OR EQUAL TO]0.030 mg/L.	One (1) sample per treatment plant per year at distribution system location reflecting maximum residence time during month of warmest water temperature. NOTE: Any § 1.6 PWS serving fewer than 500 persons may not reduce its monitoring to less than one (1) sample per treatment plant per year.
PWS using only groundwater not under direct influence of surface water using chemical disinfectant and serving at least 10,000 persons.	TTHM annual average [LESS THAN OR EQUAL TO]0.040 mg/L and HAA5 annual average [LESS THAN OR EQUAL TO]0.030 mg/L.	One (1) sample per treatment plant per year at distribution system location reflecting maximum residence time during month of warmest water temperature.
PWS using only groundwater not under direct influence of surface water using chemical disinfectant and serving fewer than 10,000 persons.	TTHM annual average [LESS THAN OR EQUAL TO]0.040 mg/L and HAA5 distribution annual average [LESS THAN OR EQUAL TO]0.030 mg/L for two (2) consecutive years OR TTHM annual average [LESS THAN OR EQUAL TO]0.020 mg/L and HAA5 annual average [LESS THAN OR EQUAL TO]0.015 mg/L for one (1) year.	One (1) sample per treatment plant per three-year monitoring cycle at PWS location reflecting maximum residence time during month of warmest water temperature, with the three-year cycle beginning on January 1 following quarter in which PWS qualifies for reduced monitoring.

c. Monitoring requirements for source water TOC. In order to qualify for reduced monitoring for TTHM and HAA5 under § 1.8.5(B)(1)(b) of this Part, § 1.6 PWS not monitoring under the provisions of § 1.8.5(D) of this Part, must take monthly TOC samples every thirty (30) days at a location prior to any treatment, beginning April 1, 2008 or earlier, if specified by the Director. In addition to meeting other criteria for reduced monitoring in § 1.8.5(B)(1)(b) of this Part, the source water TOC running annual average must be [LESS THAN OR EQUAL TO]4.0 mg/L (based on the most recent four quarters of monitoring) on a continuing basis at each treatment plant to reduce or remain on reduced monitoring for TTHM and HAA5. Once qualified for reduced monitoring for TTHM and HAA5 under § 1.8.5(B)(1)(b) of this Part, a PWS may reduce source water TOC monitoring to quarterly TOC samples taken every ninety (90) days at a location prior to any treatment.

d. PWS on a reduced monitoring schedule may remain on that reduced schedule as long as the average of all samples taken in the year (for PWSs which must monitor quarterly) or the result of the sample (for PWSs which must monitor no more frequently than annually) is no more than 0.060 mg/L and 0.045 mg/L for TTHMs and HAA5, respectively. PWS that do not meet these levels must resume monitoring at the frequency identified in § 1.8.5(B)(1)(a) of this Part, (minimum monitoring frequency column) in the quarter immediately following the monitoring period in which the PWS exceeds 0.060 mg/L or 0.045 mg/L for TTHM or HAA5 respectively. For PWS using only groundwater not under the direct influence of surface water and serving fewer than 10,000 persons, if either the TTHM annual average is >0.080 mg/L or the HAA5 annual average is >0.060 mg/L, the PWS must go to the increased monitoring identified in § 1.8.5(B)(1)(a) of this Part, (sample location column) in the quarter immediately following the monitoring period in which the PWS exceeds 0.080 mg/L or 0.060 mg/L for TTHMs or HAA5, respectively.

e. PWS on increased monitoring may return to routine monitoring if, after at least one (1) year of monitoring, their TTHM annual average is [LESS THAN OR EQUAL TO]0.060 mg/L and their HAA5 annual average is [LESS THAN OR EQUAL TO]0.045 mg/L.

f. The Director may return a PWS to routine monitoring at the Director's discretion.

2. Chlorite. Community and non-transient, non-community PWS using chlorine dioxide, for disinfection or oxidation, must conduct monitoring for chlorite.

a. Routine Monitoring

(1) Daily monitoring: PWS must take daily samples at the entrance to the distribution system. For any daily sample that exceeds the chlorite MCL, the PWS must take additional samples in the distribution system the following day at the locations required by § 1.8.5(B)(2)(b) of this Part, in addition to the sample required at the entrance to the distribution system.

(2) Monthly monitoring: PWS must take a three-sample set each month in the distribution system. The PWS 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-sample sets, at the specified locations). The PWS may use the results of additional monitoring conducted under § 1.8.5(B)(2)(b) of this Part, to meet the requirement for monitoring in this Paragraph.

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 PWS 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

(1) Chlorite monitoring at the entrance to the distribution system required by § 1.8.5(B)(2)(a)((1)) of this Part, may not be reduced.

(2) Chlorite monitoring in the distribution system required by § 1.8.5(B)(2)(a)((2)) of this Part, may be reduced to one (1) three-sample set per quarter after one (1) year of monitoring where no individual chlorite sample taken in the distribution system under § 1.8.5(B)(2)(a)((2)) of this Part, has exceeded the chlorite MCL and the PWS has not been required to conduct monitoring under § 1.8.5(B)(2)(b) of this Part. The PWS may remain on the reduced monitoring schedule until either any of the three (3) individual chlorite samples taken quarterly in the distribution system under § 1.8.5(B)(2)(a)((2)) of this Part, exceeds the chlorite MCL or the PWS is required to conduct monitoring under § 1.8.5(B)(2)(b) of this Part, at which time the PWS must revert to routine monitoring.

3. Bromate

a. Routine monitoring. Community and non-transient non-community PWS using ozone, for disinfection or oxidation, must take one (1) sample per month for each treatment plant in the PWS using ozone. PWS must take samples monthly at the entrance to the distribution system while the ozonation system is operating under normal conditions.

b. Reduced monitoring

(1) A PWS required to analyze for bromate may reduce monitoring from monthly to quarterly, if the PWS's running annual average bromate concentration is [LESS THAN OR EQUAL TO] 0.0025 mg/L based on monthly bromate measurements under § 1.8.5(B)(3)(a) of this Part, for the most recent four quarters, with samples analyzed using Method 317.0 Revision 2.0, 326.0 or 321.8. If a PWS has qualified for reduced bromate monitoring under § 1.8.5(B)(3)(b)((1)) of this Part, that PWS may remain on reduced monitoring as long as the running annual average of quarterly bromate samples is [LESS THAN OR EQUAL TO]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 PWS must resume routine monitoring required by § 1.8.5(B)(3)(a) of this Part.

C. Monitoring Requirements for Disinfectant Residuals

1. Chlorine and Chloramines

a. Routine monitoring. Community and non-transient, non-community PWS that use chlorine or chloramines must measure the residual disinfectant level in the distribution system at the same point in the distribution system and at the same time as total coliforms are sampled, as specified in §§ 1.16 and 1.17 of this Part. § 1.6 PWS may use the results of residual disinfectant concentration sampling conducted under §§ 1.6.6(A)(6) and 1.6.7(A)(3) of this Part, in lieu of taking separate samples.

b. Reduced monitoring. Monitoring may not be reduced.

2. Chlorine Dioxide

a. Routine monitoring. Community, non-transient non-community, and transient non-community PWS that use chlorine dioxide for disinfection or oxidation must take daily samples at the entrance to the distribution system. For any daily sample that exceeds the MRDL, the PWS must take samples in the distribution system the following day at the locations required by § 1.8.5(C)(2)(b) of this Part, 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 exceeds the MRDL, the PWS is required to take three (3) chlorine dioxide distribution system samples. If chlorine dioxide or 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 (i.e., no booster chlorination), the PWS 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 (i.e., booster chlorination), the PWS 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.

D. Monitoring Requirements for Disinfection Byproduct Precursors (DBPP)

1. Routine Monitoring. § 1.6 PWS which use conventional filtration treatment (as defined in § 1.2 of this Part) must monitor each treatment plant for TOC no later than the point of combined filter effluent turbidity monitoring and representative of the treated water. All PWS required to monitor under § 1.8.5(D)(1) of this Part, 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 PWS must monitor for alkalinity in the source water prior to any treatment. PWS 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.

2. Reduced Monitoring. § 1.6 PWS 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 PWS 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.

E. Bromide. PWS required to analyze for bromate may reduce bromate monitoring from monthly to once per quarter, if the PWS 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 PWS must continue bromide monitoring to remain on reduced bromate monitoring.

F. Monitoring Plans. Each PWS required to monitor under this subpart must develop and implement a monitoring plan. The PWS must maintain the plan and make it available for inspection by the Director and the general public no later than thirty (30) days following the applicable compliance dates in § 1.8.3 of this Part. All § 1.6 PWSs serving more than 3,300 people must submit a copy of the monitoring plan to the Director no later than the date of the first report required under § 1.8.7 of this Part. The Director may also require the plan to be submitted by any other PWS. After review, the Director may require changes in any plan elements. The plan must include at least the following elements.

1. Specific locations and schedules for collecting samples for any parameters included in this subpart.

2. How the PWS will calculate compliance with MCLs, MRDLs, and treatment techniques.

3. If approved by the Director for monitoring as a consecutive PWS, or if providing water to a consecutive PWS, the sampling plan must reflect the entire distribution system.

1.8.6Compliance Requirements

A. General Requirements

1. Where compliance is based on a running annual average of monthly or quarterly samples or averages and the PWS 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. Where compliance is based on a running annual average of monthly or quarterly samples or averages and the PWS 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.

2. All samples taken and analyzed under the provisions of this Section must be included in determining compliance, even if that number is greater than the minimum required.

3. If, during the first year of monitoring under § 1.8.5 of this Part, any individual quarter's average will cause the running annual average of that PWS to exceed the MCL, the PWS is out of compliance at the end of that quarter.

B. Disinfection Byproducts

1. TTHMs and HAA5

a. For PWS monitoring quarterly, compliance with MCLs in § 1.8.1 of this Part, must be based on a running annual arithmetic average, computed quarterly, of quarterly arithmetic averages of all samples collected by the PWS as prescribed by § 1.8.5(B)(1) of this Part.

b. For PWS monitoring less frequently than quarterly, PWSs demonstrate MCL compliance if the average of samples taken that year under the provisions of § 1.8.5(B)(1) of this Part does not exceed the MCLs in § 1.8.1 of this Part. If the average of these samples exceeds the MCL, the PWS must increase monitoring to once per quarter per treatment plant and such a PWS is not in violation of the MCL 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 PWS is in violation at the end of that quarter. PWS required to increase monitoring frequency to quarterly monitoring must calculate compliance by including the sample which triggered the increased monitoring plus the following three (3) quarters of monitoring.

c. If the running annual arithmetic average of quarterly averages covering any consecutive four-quarter period exceeds the MCL, the PWS is in violation of the MCL and must notify the public pursuant to § 1.16.6 of this Part, whichever is effective for your PWS, in addition to reporting to the State pursuant to § 1.8.7 of this Part.

d. If a PWS 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.

2. Bromate. Compliance must be based on a running annual arithmetic average, computed quarterly, of monthly samples (or, for months in which the PWS takes more than one (1) sample, the average of all samples taken during the month) collected by the PWS as prescribed by § 1.8.5(B)(3) of this Part. If the average of samples covering any consecutive four-quarter period exceeds the MCL, the PWS is in violation of the MCL and must notify the public pursuant to § 1.16.6 of this Part, in addition to reporting to the Director pursuant to § 1.8.7 of this Part. If a PWS fails to complete twelve (12) consecutive months' monitoring, compliance with the MCL for the last four-quarter compliance period must be based on an average of the available data.

3. Chlorite. Compliance must be based on an arithmetic average of each three (3) sample set taken in the distribution system as prescribed by §§ 1.8.5(B)(2)(a)((2)) and 1.8.5(B)(2)(b) of this Part. If the arithmetic average of any three (3) sample set exceeds the MCL, the PWS is in violation of the MCL and must notify the public pursuant to § 1.16.6 of this Part, in addition to reporting to the Director pursuant to § 1.8.7 of this Part.

C. Disinfectant Residuals

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 PWS under § 1.8.5(C)(1) of this Part. If the average covering any consecutive four-quarter period exceeds the MRDL, the PWS is in violation of the MRDL and must notify the public pursuant to § 1.16.6 of this Part, in addition to reporting to the Director pursuant to § 1.8.7 of this Part.

b. In cases where PWS 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 § 1.8.7 of this Part, 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 PWS under § 1.8.5(C)(2) of this Part. 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 PWS 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 § 1.16.6 of this Part in addition to reporting to the Director pursuant to § 1.8.7 of this Part. 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 PWS must notify the public of the violation in accordance with the provisions for acute violations under § 1.16.6 of this Part in addition to reporting to the Director pursuant to § 1.8.7 of this Part.

b. Nonacute violations. Compliance must be based on consecutive daily samples collected by the PWS under § 1.8.5(C)(2) of this Part. 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 PWS 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 will notify the public pursuant to the procedures for nonacute health risks in § 1.16.6 of this Part in addition to reporting to the Director pursuant to § 1.8.7 of this Part. 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 PWS must notify the public of the violation in accordance with the provisions for nonacute violations under § 1.16.6 of this Part in addition to reporting to the Director pursuant to § 1.8.7 of this Part.

D. Disinfection Byproduct Precursors (DBPP). Compliance must be determined as specified by § 1.8.8(C) of this Part. PWS may begin monitoring to determine whether Step 1 TOC removals can be met twelve (12) months prior to the compliance date for the PWS. This monitoring is not required and failure to monitor during this period is not a violation. However, any PWS 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 in § 1.8.8(B)(2) of this Part, 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 as allowed pursuant to § 1.8.8 (B)(3) of this Part, and is in violation. PWS may apply for alternate minimum TOC removal (Step 2) requirements any time after the compliance date. For PWS required to meet Step 1 TOC removals, if the value calculated under § 1.8.8 of this Part, is less than 1.00, the PWS is in violation of the treatment technique requirements and must notify the public pursuant to § 1.16.6 of this Part, in addition to reporting to the Director pursuant to § 1.8.7 of this Part.

1.8.7Reporting and Recordkeeping Requirements

A. PWS required to sample quarterly or more frequently must report to the Director within ten (10) days after the end of each quarter in which samples were collected. PWS required to sample less frequently than quarterly must report to the Director within ten (10) days after the end of each monitoring period in which samples were collected.

B. Disinfection Byproducts. PWS must report the information specified in the following table:

If you are a	You must report (The Director may choose to perform calculations and determine whether the MCL was exceeded, in lieu of having the PWS report that information)
(1) PWS monitoring for TTHMs and HAA5 under the requirements of § 1.8.5(B) of this Part, on a quarterly or more frequent basis.	(i) The number of samples taken during the last quarter. (ii) The location, date, and result of each sample taken during the last quarter. (iii) The arithmetic average of all samples taken in the last quarter. (iv) The annual arithmetic average of the quarterly arithmetic averages of this Section for the last four (4) quarters. (v) Whether, based on § 1.8.6(B)(1) of this Part, the MCL was violated
(2) PWS monitoring for TTHMs and HAA5 under the requirements of § 1.8.5(B) less frequently than quarterly (but as least annually).	(i) The number of samples taken during the last year. (ii) The location, date, and result of each sample taken during the last monitoring period. (iii) The arithmetic average of all samples taken over the last year. (iv) Whether, based on § 1.8.6(B)(1) of this Part, the MCL was violated.
(3) PWS monitoring for TTHMs and HAA5 under the requirements of § 1.8.5(B) of this Part, less frequently than annually.	(i) The location, date, and result of each sample taken. (ii) Whether, based on § 1.8.6(B)(1) of this Part, the MCL was violated.
(4) PWS monitoring for chlorite under the requirements of § 1.8.5 (B) of this Part.	(i) The number of entry point samples taken each month for the last 3 months. (ii) The location, date, and result of each sample (both entry point and distribution system) taken during the last quarter. (iii) For each month in the reporting period, the arithmetic average of all samples taken in each three (3) samples set taken in the distribution system. (iv) Whether, based on § 1.8.6(B)(3) of this Part, the MCL was violated, in which month, and how many times it was violated each month.
(5) PWS monitoring for bromate under the requirements of § 1.8.5(B) of this Part.	(i) The number of samples taken during the last quarter. (ii) The location, date, and result of each sample taken during the last quarter. (iii) The arithmetic average of the monthly arithmetic averages of all samples taken in the last year. (iv) Whether, based on § 1.8.6(B)(2) of this Part, the MCL was violated.

C. Disinfectants. PWS must report the information specified in the following table:

If you are a	You must report (The Director may choose to perform calculations and determine whether the MRDL was exceeded, in lieu of having the PWS report that information)
(1) PWS monitoring for chlorine or chloramines under the requirements of § 1.8.5(C) of this Part.	(i) The number of samples taken during each month of the last quarter. (ii) The month arithmetic average of all samples taken in each month for the last 12 months. (iii) The arithmetic average of the monthly averages for the last 12 months. (iv) Whether, based on § 1.8.6(C)(1) of this Part, the MRDL was violated.
(2) PWS monitoring for chlorine dioxide under the requirements of § 1.8.5(C) of this Part.	(i) The dates, result, and locations of samples taken during the last quarter. (ii) Whether, based on § 1.8.6(C)(2) of this Part, the MRDL was violated. (iii) Whether the MRDL was exceeded in any two (2) consecutive daily samples and whether the resulting violation was acute or nonacute.

D. Disinfection Byproduct Precursors and Enhanced Coagulation or Enhanced Softening. PWSs must report the information specified in the following table:

If you are a	You must report (The Director may choose to perform calculations and determine whether the treatment technique was met, in lieu of having the PWS report that information)
(1) PWS monitoring monthly or quarterly for TOC under the requirements of § 1.8.5(D) of this Part and required to meet the enhanced coagulation or enhanced softening requirements in § 1.8.8(B)(2) or (3) of this Part.	(i) The number of paired (source water and treated water) samples taken during the last quarter. (ii) The location, date, and results of each paired sample and associated alkalinity taken during the last quarter. (iii) For each month in the reporting period that paired samples were taken, the arithmetic average of the percent reduction of TOC for each paired sample and the required TOC percent removal. (iv) Calculations for determining compliance with the TOC percent removal requirements, as provided in § 1.8.8(C)(1) of this Part. (v) Whether the PWS is in compliance with the enhanced coagulation or enhanced softening percent removal requirements in § 1.8.8(B) of this Part for the last four (4) quarters.
(2) PWS monitoring monthly or quarterly for TOC under the requirements of § 1.8.5(D) of this Part and meeting one (1) or more of the alternative compliance criteria in §§ 1.8.8(A)(2) or (3) of this Part.	(i) The alternative compliance criterion that the PWS is using. (ii) The number of paired samples taken during the last quarter. (iii) The location, date, and result of each paired sample and associated alkalinity taken during the last quarter. (iv) The running annual arithmetic average based on monthly averages (or quarterly samples) of source water TOC for PWS meeting a criterion in §§ 1.8.8(A)(2)(a) or (c) or of treated water TOC for PWS meeting the criterion in § 1.8.8(A)(2)(b) of this Part. (v) The running annual arithmetic average based on monthly averages (or quarterly samples) of source water SUVA for PWS meeting the criterion in § 1.8.8(A)(2)(e) or of treated water SUVA for PWS meeting the criterion in § 1.8.8(A)(2)(f) of this Part. (vi) The running annual average of source water alkalinity for PWS meeting the criterion in § 1.8.8(A)(2)(c) and of treated water alkalinity for PWS meeting the criterion in § 1.8.8(A)(3)(a) of this Part. (vii) The running annual average for both TTHM and HAA5 for PWS meeting the criterion in §§ 1.8.8(A)(2)(c) or (d) of this Part. (viii) The running annual average of the amount of magnesium hardness removal (as CaCO3, in mg/L) for PWS meeting the criterion in § 1.8.8(A)(3)(b) of this Part. (ix) Whether the PWS is in compliance with the particular alternative compliance criterion in §§ 1.8.8(A)(2) or (3) of this Part.

1.8.8Treatment Technique for Control of Disinfection Byproduct (DBP) Precursors

A. Applicability

1. § 1.6 PWS using conventional filtration treatment (as defined in § 1.2 of this Part) must operate with enhanced coagulation or enhanced softening to achieve the TOC percent removal levels specified in § 1.8.8(B) of this Part unless the PWS meets at least one (1) of the alternative compliance criteria listed in §§ 1.8.8(A)(2) or (3) of this Part.

2. Alternative Compliance Criteria for Enhanced Coagulation and Enhanced Softening Systems. § 1.6 PWS using conventional filtration treatment may use the alternative compliance criteria in §§ 1.8.8(A)(2)(a) through (f) of this Part to comply with this Section in lieu of complying with § 1.8.8(B) of this Part. PWS must still comply with monitoring requirements in § 1.8.5(D) of this Part.

a. The PWS's source water TOC level, measured according to § 1.8.4(D)(3) of this Part, is less than 2.0 mg/L, calculated quarterly as a running annual average.

b. The PWS's treated water TOC level, measured according to § 1.8.4(D)(3) of this Part, is less than 2.0 mg/L, calculated quarterly as a running annual average.

c. The PWS's source water TOC level, measured according to § 1.8.4(D)(3) of this Part, is less than 4.0 mg/L, calculated quarterly as a running annual average; the source water alkalinity, measured according to § 1.8.4(D)(1) of this Part, 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. PWS 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 Director for approval. Failure to install and operate these technologies by the date in the approved schedule will constitute a violation of this Part.

d. The TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively, and the PWS uses only chlorine for primary disinfection and maintenance of a residual in the distribution system.

e. The PWS's source water SUVA, prior to any treatment and measured monthly according to § 1.8.4(D)(4) of this Part, is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.

f. The PWS's finished water SUVA, measured monthly according to § 1.8.4(D)(4) of this Part, is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.

3. Additional Alternative Compliance Criteria for Softening Systems. PWS practicing enhanced softening that cannot achieve the TOC removals required by § 1.8.8(B)(2) of this Part may use the alternative compliance criteria in §§ 1.8.8(A)(3)(a) and (b) of this Part in lieu of complying with § 1.8.8(B) of this Part. PWS must still comply with monitoring requirements in § 1.8.5(D) of this Part.

a. Softening that results in lowering the treated water alkalinity to less than 60 mg/L (as CaCO3), measured monthly according to § 1.8.4(D)(1) of this Part, and calculated quarterly as a running annual average.

b. Softening that results in removing at least 10 mg/L of magnesium hardness (as CaCO3), measured monthly according to § 1.8.4(D)(6) of this Part, and calculated quarterly as an annual running average.

B. Enhanced Coagulation and Enhanced Softening Performance Requirements

1. PWS must achieve the percent reduction of TOC specified in § 1.8.8(B)(2) of this Part, between the source water and the combined filter effluent, unless the Director approves a PWS's request for alternate minimum TOC removal (Step 2) requirements under § 1.8.8(B)(3) of this Part.

2. Required Step 1 TOC reductions, indicated in the following table, are based upon specified source water parameters measured in accordance with § 1.8.4(D) of this Part. PWS 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.

Step 1 Required Removal of TOC by Enhanced Coagulation and Enhanced Softening for § 1.5 PWSs Using Conventional Treatment. PWS meeting at least one (1) of the conditions in §§ 1.8.8(A)(2)(a) through (f) of this Part are not required to operate with enhanced coagulation. Softening systems meeting one (1) of the alternative compliance criteria in § 1.8.8(A)(3) of this Part are not required to operate with enhanced softening.
Source-water TOC, mg/L	Source-water alkalinity, mg/L as CaCO3 (in percentages)
	0-60	>60- 120	>120 (PWS practicing softening must meet the TOC removal requirements in this column)
>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

3. § 1.6 conventional treatment systems that cannot achieve the Step 1 TOC removals required by § 1.8.8(B)(2) of this Part, due to water quality parameters or operational constraints must apply to the Director, within three (3) months of failure to achieve the TOC removals required by § 1.8.8(B)(2) of this Part, for approval of alternative minimum TOC (Step 2) removal requirements submitted by the PWS. If the Director approves the alternative minimum TOC removal (Step 2) requirements, the Director may make those requirements retroactive for the purposes of determining compliance. Until the Director approves the alternate minimum TOC removal (Step 2) requirements, the PWS must meet the Step 1 TOC removals contained in § 1.8.8(B)(2) of this Part.

4. Alternate Minimum TOC Removal (Step 2) Requirements. Applications made to the Director by enhanced coagulation systems for approval of alternate minimum TOC removal (Step 2) requirements under § 1.8.8(B)(3) of this Part must include, at a minimum, results of bench- or pilot-scale testing conducted under § 1.8.8(B)(4)(a) of this Part. The submitted bench- or pilot-scale testing must be used to determine the alternate enhanced coagulation level.

a. Alternate enhanced coagulation level is defined as coagulation at a coagulant dose and pH as determined by the method described in §§ 1.8.8(B)(4)(a) through (e) of this Part, such that an incremental addition of 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 PWS. Once approved by the Director, this minimum requirement supersedes the minimum TOC removal required by the table in § 1.8.8(B)(2) of this Part. This requirement will be effective until such time as the Director approves a new value based on the results of a new bench- and pilot-scale test. Failure to achieve Director- set alternative minimum TOC removal levels is a violation of this Part.

b. 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 the following table:

Enhanced Coagulation Step 2 Target pH
Alkalinity (mg/L as CaCO3)	Target pH
0-60	5.5
>60-120	6.3
>120-240	7.0
>240	7.5

c. For waters with alkalinities of less than 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 PWS 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.

d. The PWS may operate at any coagulant dose or pH necessary (consistent with the other requirements of this Part) to achieve the minimum TOC percent removal approved under § 1.8.8(B)(3) of this Part.

e. 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 PWS may then apply to the Director for a waiver of enhanced coagulation requirements.

C. Compliance Calculations

1. § 1.6 PWS other than those identified in §§ 1.8.8(A)(2) or (3) of this Part must comply with requirements contained in §§ 1.8.8(B)(2) or (3) of this Part. PWS must calculate compliance quarterly, beginning after the PWS has collected twelve (12) months of data, by determining an annual average using the following method:

a. Determine actual monthly TOC percent removal, equal to: (1 - (treated water TOC/source water TOC)) [CROSS] 100

b. Determine the required monthly TOC percent removal (from either the table in § 1.8.8(B)(2) or from § 1.8.8(B)(3) of this Part.

c. Divide the value in § 1.8.8(C)(1)(a) of this Part by the value in § 1.8.8(C)(1)(b) of this Part.

d. Add together the results of § 1.8.8(C)(1)(c) of this Part, for the last twelve (12) months and divide by 12.

e. If the value calculated in § 1.8.8(C)(1)(d) of this Part is less than 1.00, the PWS is not in compliance with the TOC percent removal requirements.

2. PWS may use the provisions in §§ 1.8.8(C)(2)(a) through (e) of this Part in lieu of the calculations in §§ 1.8.8(C)(1)(a) through (e) of this Part, to determine compliance with TOC percent removal requirements.

a. In any month that the PWS's treated or source water TOC level, measured according to § 1.8.4(D)(3) of this Part, is less than 2.0 mg/L, the PWS may assign a monthly value of 1.0 (in lieu of the value calculated in § 1.8.8(C)(1)(c) of this Part) when calculating compliance under the provisions of § 1.8.8(C)(1) of this Part.

b. In any month that a PWS practicing softening removes at least 10 mg/L of magnesium hardness (as CaCO3), the PWS may assign a monthly value of 1.0 (in lieu of the value calculated in § 1.8.8(C)(1)(c) of this Part) when calculating compliance under the provisions of § 1.8.8(C)(1) of this Part.

c. In any month that the PWS's source water SUVA, prior to any treatment and measured according to § 1.8.4(D)(4) of this Part, is [LESS THAN OR EQUAL TO]2.0 L/mg-m, the PWS may assign a monthly value of 1.0 (in lieu of the value calculated in § 1.8.8(C)(1)(c) of this Part) when calculating compliance under the provisions of § 1.8.8(C)(1) of this Part.

d. In any month that the PWS's finished water SUVA, measured according to § 1.8.4(D)(4) of this Part, is [LESS THAN OR EQUAL TO]2.0 L/mg-m, the PWS may assign a monthly value of 1.0 (in lieu of the value calculated in § 1.8.8(C)(1)(c) of this Part) when calculating compliance under the provisions of § 1.8.8(C)(1) of this Part.

e. In any month that a PWS practicing enhanced softening lowers alkalinity below 60 mg/L (as CaCO3), the PWS may assign a monthly value of 1.0 (in lieu of the value calculated in § 1.8.8(C)(1)(c) of this Part) when calculating compliance under the provisions of § 1.8.8 (C)(1) of this Part.

3. § 1.6 PWS using conventional treatment may also comply with the requirements of this Section by meeting the criteria in §§ 1.8.8(A)(2) or (3) of this Part.

D. Treatment Technique Requirements for DBP Precursors. The following are identified as treatment techniques to control the level of disinfection byproduct precursors in drinking water treatment and distribution systems. For § 1.6 PWS using conventional treatment, enhanced coagulation or enhanced softening.

1.8.9Initial Distribution System Evaluations

A. General Requirements

1. The requirements of § 1.8.9 of this Part constitute national primary drinking water regulations. The regulations in § 1.8.9 of this Part establish monitoring and other requirements for identifying § 1.8.10 of this Part, compliance monitoring locations for determining compliance with maximum contaminant levels for total trihalomethanes (TTHM) and haloacetic acids (five)(HAA5). You must use an Initial Distribution System Evaluation (IDSE) to determine locations with representative high TTHM and HAA5 concentrations throughout your distribution system. IDSEs are used in conjunction with, but separate from, § 1.8 compliance monitoring, to identify and select § 1.8.10 of this Part, compliance monitoring locations.

2. Applicability. You are subject to these requirements if your PWS is a community PWS that uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light; or if your PWS is a non-transient non-community PWS that serves at least 10,000 people and uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light.

3. Schedule

a. You must comply with the requirements of § 1.8.9 of this Part on the schedule i n the table below.

If you serve this population	You must submit your standard monitoring plan or system specific study plan (If, within 12 months after the date identified in this column, the Director does not approve your plan or notify you that it has not yet completed its review, you may consider the plan that you submitted as approved. You must implement that plan and you must complete standard monitoring or a system specific study no later than the date identified in the third column) or 40/30 certification (You must submit your 40/30 certification under § 1.8.9(D) of this Part by the date indicated) to the Director by or receive very small system waiver from Director	You must complete your standard monitoring system specific study by	You must submit your IDSE report Director by (If, within three months after the date identified in this column (nine months after the date identified in this column if you must comply on the schedule in § 1.8.9(A)(3)(a) of this Part, the Director does not approve your IDSE report or notify you that it has not yet completed its review, you may consider the report that you submitted as approved and you must implement the recommended § 1.8.10 of this Part monitoring as required)
Systems that are not part of a combined distribution system and systems that serve the largest population in the combined distribution system
(i) Greater than or equal to 100,000	October 1, 2006	September 30, 2008	January 1, 2009
(ii) 50,000-99,999	April 1, 2007	March 31, 2009	July 1, 2009
(iii) 10,000-49,999	October 1, 2007	September 30, 2009	January 1, 2010
(iv) Less than 10,000 (CWS only)	April 1, 2008	March 31, 2010	July 1, 2010
Other systems that are part of a combined distribution system
(v) Wholesale system or consecutive system	At the same time as the system with the earliest compliance date in the combined distribution system

b. For the purpose of the schedule in § 1.8.9(A)(3)(a) of this Part, the Director may determine that the combined distribution system does not include certain consecutive PWS based on factors such as receiving water from a wholesale PWS only on an emergency basis or receiving only a small percentage and small volume of water from a wholesale PWS. The Director may also determine that the combined distribution system does not include certain wholesale PWS based on factors such as delivering water to a consecutive PWS only on an emergency basis or delivering only a small percentage and small volume /of water to a consecutive PWS.

4. You must conduct standard monitoring that meets the requirements in § 1.8.9(B) of this Part, or a system specific study that meets the requirements in § 1.8.9(C) of this Part, or certify to the Director that you meet 40/30 certification criteria under § 1.8.9(D) of this Part, or qualify for a very small system waiver under § 1.8.9(E) of this Part.

a. You must have taken the full complement of routine TTHM and HAA5 compliance samples required of a PWS with your population and source water under § 1.8 of this Part (or you must have taken the full complement of reduced TTHM and HAA5 compliance samples required of a PWS with your population and source water under § 1.8 of this Part if you meet reduced monitoring criteria under § 1.8 of this Part during the period specified in § 1.8.9(D)(1) of this Part to meet the 40/30 certification criteria in § 1.8.9(D) of this Part. You must have taken TTHM and HAA5 samples under §§ 1.8.4 and 1.8.5 of this Part to be eligible for the very small system waiver in § 1.8.9(E) of this Part.

b. If you have not taken the required samples, you must conduct standard monitoring that meets the requirements in § 1.8.9(B) of this Part, or a system specific study that meets the requirements in § 1.8.9(C) of this Part.

5. You must use only the analytical methods specified in § 1.8.4 of this Part, or otherwise approved by EPA for monitoring under this subpart, to demonstrate compliance with the requirements of this subpart.

6. IDSE results will not be used for the purpose of determining compliance with MCLs in § 1.8 of this Part.

B. Standard Monitoring

1. Standard Monitoring Plan. Your standard monitoring plan must comply with §§ 1.8.9(B)(1)(a) through (d) of this Part. You must prepare and submit your standard monitoring plan to the Director according to the schedule in § 1.8.9(A)(3) of this Part.

a. Your standard monitoring plan must include a schematic of your distribution system (including distribution system entry points and their sources, and storage facilities), with notes indicating locations and dates of all projected standard monitoring, and all projected § 1.8 compliance monitoring.

b. Your standard monitoring plan must include justification of standard monitoring location selection and a summary of data you relied on to justify standard monitoring location selection.

c. Your standard monitoring plan must specify the population served and PWS type (§ 1.6 or groundwater).

d. You must retain a complete copy of your standard monitoring plan submitted under § 1.8.9(B)(1) of this Part, including any Director modification of your standard monitoring plan, for as long as you are required to retain your IDSE report under § 1.8.9(B)(3)(d) of this Part.

2. Standard Monitoring

a. You must monitor as indicated in the table below. You must collect dual sample sets at each monitoring location. One sample in the dual sample set must be analyzed for TTHM. The other sample in the dual sample set must be analyzed for HAA5. You must conduct one monitoring period during the peak historical month for TTHM levels or HAA5 levels or the month of warmest water temperature. You must review available compliance, study, or operational data to determine the peak historical month for TTHM or HAA5 levels or warmest water temperature.

Source Water Type	Population Size Category	Monitoring periods and frequency of sampling	Distribution system monitoring locations18
			Total per monitoring period	Near entry points	Average residence time	High TTHM locations	High HAA5 locations
	< 500 consecutive systems	One (during peak historical month)19	2	1	......	1
	< 500 non- consecutive systems	.................	2	......	......	1	1
	500-3,300 consecutive systems	Four (every 90 days)	2	1	......	1
	500-3,300 non- consecutive systems	.................	2	......	......	1	1
	3,301-9,999	.................	4	......	1	2	1
	10,000-49,999	Six (every 60 days)	8	1	2	3	2
	50,000-249,999	.................	16	3	4	5	4
	250,000-999,999	.................	24	4	6	8	6
	1,000,000-4,999,999	.................	32	6	8	10	8
	[GREATER THAN OR EQUAL TO] 5,000,000	.................	40	8	10	12	10
Ground Water:
	< 500 consecutive systems	One (during peak historical month)19	2	1	..........	1
	< 500 non- consecutive systems	.................	2		..........	1	1
	500-9,999	Four (every 90 days)	2		..........	1	1
	10,000-99,999	.................	6	1	1	2	2
	1,000,000-4,999,999	.................	8	1	1	3	3
	[GREATER THAN OR EQUAL TO]5,000,000	.................	12	2	2	4	4
18 A dual sample set (i.e., a TTHM and an HAA5 sample) must be taken at each monitoring location during each monitoring period 19 The peak historical month is the month with the highest TTHM or HAA5 levels or the warmest water temperature.

b. You must take samples at locations other than the existing § 1.8 of this Part monitoring locations. Monitoring locations must be distributed throughout the distribution system.

c. If the number of entry points to the distribution system is fewer than the specified number of entry point monitoring locations, excess entry point samples must be replaced equally at high TTHM and HAA5 locations. If there is an odd extra location number, you must take a sample at a high TTHM location. If the number of entry points to the distribution system is more than the specified number of entry point monitoring locations, you must take samples at entry points to the distribution system having the highest annual water flows.

d. Your monitoring under § 1.8.9(B)(2) of this Part may not be reduced under the provisions of other sections of this Part.

3. IDSE Report. Your IDSE report must include the elements required in § 1.8.9(B)(3)(a) through (d) of this Part. You must submit your IDSE report to the Director according to the schedule in § 1.8.9(A)(3) of this Part.

a. Your IDSE report must include all TTHM and HAA5 analytical results from § 1.8 of this Part compliance monitoring and all standard monitoring conducted during the period of the IDSE as individual analytical results and LRAAs presented in a tabular or spreadsheet format acceptable to the Director. If changed from your standard monitoring plan submitted under § 1.8.9(B)(1) of this Part, your report must also include a schematic of your distribution system, the population served, and PWS type (§ 1.6 or groundwater).

b. Your IDSE report must include an explanation of any deviations from your approved standard monitoring plan.

c. You must recommend and justify § 1.8.10 of this Part compliance monitoring locations and timing based on the protocol in § 1.8.9(F) of this Part.

d. You must retain a complete copy of your IDSE report submitted under § 1.8.9(B) of this Part for 10 years after the date that you submitted your report. If the Director modifies the § 1.8.10 of this Part monitoring requirements that you recommended in your IDSE report or if the Director approves alternative monitoring locations, you must keep a copy of the Director's notification on file for 10 years after the date of the Director's notification. You must make the IDSE report and any Director notification available for review by the Director or the public.

C. System Specific Studies

1. System Specific Study Plan. Your system specific study plan must be based on either existing monitoring results as required under § 1.8.9(C)(1)(a) of this Part or modeling as required under § 1.8.9(C)(1)(b) of this Part. You must prepare and submit your system specific study plan to the Director according to the schedule in § 1.8.9(A)(3) of this Part.

a. Existing Monitoring Results. You may comply by submitting monitoring results collected before you are required to begin monitoring under § 1.8.9(A)(3) of this Part. The monitoring results and analysis must meet the criteria in §§ 1.8.9(C)(1)(a)((1)) and ((2)) of this Part.

(1) Minimum Requirements

(AA) TTHM and HAA5 results must be based on samples collected and analyzed in accordance with § 1.8.4 of this Part. Samples must be collected no earlier than five years prior to the study plan submission date.

(BB) The monitoring locations and frequency must meet the conditions identified in this paragraph [§ 1.8.9(C)(1)(a)((1))((BB)) of this Part]. Each location must be sampled once during the peak historical month for TTHM levels or HAA5 levels or the month of warmest water temperature for every 12 months of data submitted for that location. Monitoring results must include all § 1.8 of this Part compliance monitoring results plus additional monitoring results as necessary to meet minim um sample requirements.

System Type	Population Size Category	Number of Monitoring Locations	Number of Samples
			TTHM	HAA5
	< 500	3	3	3
	500-3,300	3	9	9
	3,301-9,999	6	36	36
	10,000-49,999	12	72	72
	50,000-249,999	24	144	144
	250,000-999,999	36	216	216
	1,000,000-4,999,999	48	288	288
	[GREATER THAN OR EQUAL TO] 5,000,000	60	300	300
Ground Water:
	< 500	3	3	3
	500-9,999	3	9	9
	10,000-99,999	12	48	48
	1,000,000-4,999,999	18	72	72
	[GREATER THAN OR EQUAL TO] 5,000,000	24	96	96

(2) Reporting Monitoring Results. You must report the information in this paragraph [§ 1.8.9(C)(1)(a)((2)) of this Part].

(AA) You must report previously collected monitoring results and certify that the reported monitoring results include all compliance and non-compliance results generated during the time period beginning with the first reported result and ending with the most recent § 1.8 of this Part results.

(BB) You must certify that the samples were representative of the entire distribution system and that treatment, and distribution system have not changed significantly since the samples were collected.

(CC) Your study monitoring plan must include a schematic of your distribution system (including distribution system entry points and their sources, and storage facilities), with notes indicating the locations and dates of all completed or planned system specific study monitoring.

(DD) Your system specific study plan must specify the population served and PWS type (§ 1.6 or groundwater).

(EE) You must retain a complete copy of your system specific study plan submitted under § 1.8.9(C)(1)(a) of this Part including any Director modification of your system specific study plan, for as long as you are required to retain your IDSE report under § 1.8.9(C)(2)(g) of this Part.

(FF) If you submit previously collected data that fully meet the number of samples required under § 1.8.9(C)(1)(a)((1))((BB)) of this Part and the Director rejects some of the data, you must either conduct additional monitoring to replace rejected data on a schedule the Director approves or conduct standard monitoring under § 1.8.9(B) of this Part.

b. Modeling. You may comply through analysis of an extended period simulation hydraulic model. The extended period simulation hydraulic model and analysis must meet the criteria in this paragraph, § 1.8.9(C)(1)(b) of this Part.

(1) Minimum Requirements.

(AA) The model must simulate 24-hour variation in demand and show a consistently repeating 24-hour pattern of residence time.

(BB) The model must represent the criteria listed in §§ 1.8.9(C)(1)(b)((1))((BB))((i)) through ((ix)) of this Part.

(i) Seventy-five percent (75%) of pipe volume;

(ii) Fifty percent (50%) of pipe length;

(iii) All pressure zones;

(iv) All 12-inch diameter and larger pipes;

(v) All 8-inch and larger pipes that connect pressure zones, influence zones from different sources, storage facilities, major demand areas, pumps, and control valves, or are known or expected to be significant conveyors of water;

(vi) All 6-inch and larger pipes that connect remote areas of a distribution system to the main portion of the system;

(vii) All storage facilities with standard operations represented in the model; and

(viii) All active pump stations with controls represented in the model; and

(ix) All active control valves.

(CC) The model must be calibrated, or have calibration plans, for the current configuration of the distribution system during the period of high TTHM formation potential. All storage facilities must be evaluated as part of the calibration process. All required calibration must be completed no later than twelve (12) months after plan submission.

(2) Reporting Modeling. Your system specific study plan must include the information in this paragraph [§ 1.8.9(C)(1)(b)((2)) of this Part].

(AA) Tabular or spreadsheet data demonstrating that the model meets requirements in § 1.8.9(C)(1)(b)((1))((BB)) of this Part.

(BB) A description of all calibration activities undertaken, and if calibration is complete, a graph of predicted tank levels versus measured tank levels for the storage facility with the highest residence time in each pressure zone, and a time series graph of the residence time at the longest residence time storage facility in the distribution system showing the predictions for the entire simulation period (i.e., from time zero until the time it takes to for the model to reach a consistently repeating pattern of residence time).

(CC) Model output showing preliminary 24-hour average residence time predictions throughout the distribution system.

(DD) Timing and number of samples representative of the distribution system planned for at least one monitoring period of TTHM and HAA5 dual sample monitoring at a number of locations no less than would be required for the PWS under standard monitoring in § 1.8.9(B) of this Part, during the historical month of high TTHM. These samples must be taken at locations other than existing § 1.8 of this Part compliance monitoring locations.

(EE) Description of how all requirements will be completed no later than twelve (12) months after you submit your system specific study plan.

(FF) Schematic of your distribution system (including distribution system entry points and their sources, and storage facilities), with notes indicating the locations and dates of all completed system specific study monitoring (if calibration is complete) and all § 1.8 of this Part compliance monitoring.

(GG) Population served and PWS type (§ 1.6 or groundwater).

(HH) You must retain a complete copy of your system specific study plan submitted under this § 1.8.9(C)(1)(b) of this Part, including any Director modification of your system specific study plan, for as long as you are required to retain your IDSE report under § 1.8.9(C)(2)(g) of this Part.

(3) If you submit a model that does not fully meet the requirements under § 1.8.9(C)(1)(b) of this Part, you must correct the deficiencies and respond to the Director's inquiries concerning the model. If you fail to correct deficiencies or respond to inquiries to the Director's satisfaction, you must conduct standard monitoring under § 1.8.9(B) of this Part.

2. IDSE Report. Your IDSE report must include the elements required in §§ 1.8.9(C)(2)(a) through (f) of this Part. You must submit your IDSE report according to the schedule in § 1.8.9(A)(3) of this Part.

a. Your IDSE report must include all TTHM and HAA5 analytical results from § 1.8 of this Part compliance monitoring and all system specific study monitoring conducted during the period of the system specific study presented in a tabular or spreadsheet format acceptable to the Director. If changed from your system specific study plan submitted under § 1.8.9(C)(1) of this Part, your IDSE report must also include a schematic of your distribution system, the population served, and PWS type (§ 1.6 or groundwater).

b. If you used the modeling provision under § 1.8.9(C)(1)(b) of this Part, you must include final information for the elements described in § 1.8.9(C)(1)(b)((2)) of this Part, and a 24-hour time series graph of residence time for each § 1.8.10 compliance monitoring location selected.

c. You must recommend and justify § 1.8.10 compliance monitoring locations and timing based on the protocol in § 1.8.9(F) of this Part.

d. Your IDSE report must include an explanation of any deviations from your approved system specific study plan.

e. Your IDSE report must include the basis (analytical and modeling results) and justification you used to select the recommended § 1.8.10 of this Part monitoring locations.

f. You may submit your IDSE report in lieu of your system specific study plan on the schedule identified in § 1.8.9(A)(3) of this Part for submission of the system specific study plan if you believe that you have the necessary information by the time that the system specific study plan is due. If you elect this approach, your IDSE report must also include all information required under § 1.8.9(C)(1) of this Part.

g. You must retain a complete copy of your IDSE report submitted under this Section for 10 years after the date that you submitted your IDSE report. If the Director modifies the § 1.8.10 monitoring requirements that you recommended in your IDSE report or if the Director approves alternative monitoring locations, you must keep a copy of the Director's notification on file for 10 years after the date of the Director's notification. You must make the IDSE report and any Director notification available for review by the Director or the public.

D. 40/30 Certification

1. Eligibility. You are eligible for 40/30 certification if you had no TTHM or HAA5 monitoring violations under § 1.8 of this Part, and no individual sample exceeded 0.040 mg/L for TTHM or 0.030 mg/L for HAA5 during an eight-consecutive calendar quarter period beginning no earlier than the date specified in the table below.

If your 40/30 certification is due	Then your eligibility for 40/30 certification is based on eight consecutive calendar quarters of § 1.8 of this Part compliance monitoring results beginning no earlier than (unless you are on reduced monitoring under § 1.8 of this Part and were not required to monitor during the specified period. If you did not monitor during the specified period, you must base your eligibility on compliance samples taken during the 12 months preceding the specified period)
(1) October 1, 2006	January 2004
(2) April 1, 2007	January 2004
(3) October 1, 2007	January 2005
(4) April 1, 2008	January 2005

2. 40/30 Certification

a. You must certify to the Director that every individual compliance sample taken under § 1.8 of this Part during the periods specified in paragraph (a) of this Section were [LESS THAN OR EQUAL TO] 0.040 mg/L for TTHM and [LESS THAN OR EQUAL TO] 0.030 mg/L for HAA5, and that you have not had any TTHM or HAA5 monitoring violations during the period specified in § 1.8.9(D)(1) of this Part.

b. The Director may require you to submit compliance monitoring results, distribution system schematics, and/or recommended § 1.8.10 of this Part compliance monitoring locations in addition to your certification. If you fail to submit the requested information, the Director may require standard monitoring under § 1.8.9(B) of this Part or a system specific study under § 1.8.9(C) of this Part.

c. The Director may still require standard monitoring under § 1.8.9(B) of this Part or a system specific study under § 1.8.9(C) of this Part even if you meet the criteria in § 1.8.9(D)(1) of this Part.

d. You must retain a complete copy of your certification submitted under this Section for ten (10) years after the date that you submitted your certification. You must make the certification, all data upon which the certification is based, and any Director notification available for review by the Director or the public.

E. Very Small System Waivers

1. If you serve fewer than five hundred (500) people and you have taken TTHM and HAA5 samples under § 1.8 of this Part, you are not required to comply with § 1.8.9 of this Part unless the Director notifies you that you must conduct standard monitoring under § 1.8.9(B) of this Part or a system specific study under § 1.8.9(C) of this Part.

2. If you have not taken TTHM and HAA5 samples under § 1.8 of this Part or if the Director notifies you that you must comply with § 1.8.9 of this Part, you must conduct standard monitoring under § 1.8.9(B) of this Part or a system specific study under § 1.8.9(C) of this Part.

F. Stage 2 (§ 1.8.10) Compliance Monitoring Location Recommendations

1. Your IDSE report must include your recommendations and justification for where and during what month(s) TTHM and HAA5 monitoring for § 1.8.10 of this Part should be conducted. You must base your recommendations on the criteria in §§ 1.8.9(F)(2) through (5) of this Part.

2. You must select the number of monitoring locations specified in the table below. You will use these recommended locations as § 1.8.10 of this Part routine compliance monitoring locations, unless the Director requires different or additional locations. You should distribute locations throughout the distri bution system to the extent possible.

Source Water Type	Population Size Category	Monitoring Frequency	Distribution system monitoring location
			Total per monitoring period	Highest TTHM locations	Highest HAA5 locations	Existing § 1.8 locations
§ 1.6	Less than 500	Per year	2	1	1
	500-3,300	Per quarter	2	1	1
	3,301-9,999	Per quarter	2	1	1
	10,000-49,999	Per quarter	4	2	2	1
	50,000-249,999	Per quarter	8	3	3	2
	250,000-999,999	Per quarter	12	5	5	3
	1,000,000-4,999,999	Per quarter	16	6	6	4
	Greater than or equal to 5,000,00 0	Per quarter	20	8	7	5
Ground Water	Less than 500	Per year	2	1	1
	500-9,999	Per year	2	1	1
	10,000-99,999	Per quarter	4	2	1	1
	1,000,000-4,999,999	Per quarter	6	3	2	1
	Greater than or equal to 5,000,00 0	Per quarter	8	3	3	2

a. All PWS must monitor during month of highest DBP concentrations.

b. PWS on quarterly monitoring must take dual sample sets every ninety (90) days at each monitoring location, except for § 1.6 PWSs serving 500-3,300. Groundwater PWS serving 500-9,999 on annual monitoring must take dual sample sets at each monitoring location. All other PWS on annual monitoring and § 1.6 PWS serving 500-3,300 are required to take individual TTHM and HAA5 samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. For PWS serving fewer than five hundred (500) people, only one (1) location with a dual sample set per monitoring period is needed if highest TTHM and HAA5 concentrations occur at the same location and month.

3. You must recommend § 1.8.10 compliance monitoring locations based on standard monitoring results, system specific study results, and § 1.8 of this Part compliance monitoring results. You must follow the protocol in §§ 1.8.9(F)(3)(a) through (h) of this Part. If required to monitor at more than eight locations, you must repeat the protocol as necessary. If you do not have existing § 1.8 of this Part compliance monitoring results or if you do not have enough existing § 1.8 of this Part compliance monitoring results, you must repeat the protocol, skipping the provisions of §§ 1.8.9(F)(3)(c) and (g) of this Part, as necessary, until you have identified the required total number of monitoring locations.

a. Location with the highest TTHM LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

b. Location with the highest HAA5 LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

c. Existing § 1.8 of this Part average residence time compliance monitoring location (maximum residence time compliance monitoring location for groundwater PWSs) with the highest HAA5 LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

d. Location with the highest TTHM LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

e. Location with the highest TTHM LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

f. Location with the highest HAA5 LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

g. Existing § 1.8 of this Part average residence time compliance monitoring location (maximum residence time compliance monitoring location for groundwater PWSs) with the highest TTHM LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

h. Location with the highest HAA5 LRAA not previously selected as a § 1.8.10 of this Part monitoring location.

4. You may recommend locations other than those specified in § 1.8.9(F)(3) of this Part if you include a rationale for selecting other locations. If the Director approves the alternate locations, you must monitor at these locations to determine compliance under § 1.8.10 of this Part.

5. Your recommended schedule must include § 1.8.10 of this Part monitoring during the peak historical month for TTHM and HAA5 concentration, unless the Director approves another month. Once you have identified the peak historical month, and if you are required to conduct routine monitoring at least quarterly, you must schedule § 1.8.10 of this Part compliance monitoring at a regular frequency of every 90 days or fewer.

1.8.10Stage 2 Disinfection Byproducts Requirements

A. General Requirements

1. General. The requirements of § 1.8.10 of this Part constitute national primary drinking water regulations. The regulations in § 1.8.10 of this Part establish 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 PWSs.

2. Applicability. You are subject to these requirements if your PWS is a community PWS or a non-transient non-community PWS that uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light.

3. Schedule. You must comply with the requirements in this subpart on the schedule in the fo llowing table based on your PWS type.

If you are this type of PWS	You must comply with § 1.8.10 of this Part monitoring by: (The Director may grant up to an additional twenty-four (24) months for compliance with MCLs and operational evaluation levels if you require capital improvements to comply with an MCL.)
PWS that are not part of a combined distribution system and PWS that serve the largest population in the combined distribution system
a. PWS serving [GREATER THAN OR EQUAL TO] 100,000	April 1, 2012
b. PWS serving 50,000-99,999	October 1, 2012
c. PWS serving 10,000-49,999	October 1, 2013
d. PWS serving < 10,000	October 1, 2013 if no Cryptosporidium monitoring is required under § 1.6.9(B)(1)(d) of this Part, or October 1, 2014 if Cryptosporidium monitoring is required under §§ 1.6.9(B)(1)(d) or (f) of this Part
Other PWS that are part of a combined distribution system
e. Consecutive PWS or wholesale PWS	At the same time as the PWS with the earliest compliance date in the combined distribution system
f. Your monitoring frequency is specified in § 1.8.10(B)(1)(b) of this Part. (1) If you are required to conduct quarterly monitoring, you must begin monitoring in the first full calendar quarter that includes the compliance date in the table in § 1.8.10(A)(3) of this Part. (2) If you are required to conduct monitoring at a frequency that is less than quarterly, you must begin monitoring in the calendar month recommended in the IDSE report prepared under §§ 1.8.9(B) or 1.8.9(C) of this Part or the calendar month identified in the § 1.8.10 monitoring plan developed under § 1.8.10(C) of this Part, no later than twelve (12) months after the compliance date in this table.
g. If you are required to conduct quarterly monitoring, you must make 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 quarters of data would cause the MCL to be exceeded regardless of the monitoring results of subsequent quarters). If you are required to conduct monitoring at a frequency that is less than quarterly, you must make compliance calculations beginning with the first compliance sample taken after the compliance date.
h. For the purpose of the schedule in § 1.8.10(A)(3) of this Part, the Director may determine that the combined distribution system does not include certain consecutive PWS based on factors such as receiving water from a wholesale PWS only on an emergency basis or receiving only a small percentage and small volume of water from a wholesale PWS. The Director may also determine that the combined distribution system does not include certain wholesale PWS based on factors such as delivering water to a consecutive PWS only on an emergency basis or delivering only a small percentage and small volume of water to a consecutive PWS.

4. Monitoring and Compliance

a. PWS Required to Monitor Quarterly. To comply with the MCLs in § 1.8.1 of this Part, you must calculate LRAAs for TTHM and HAA5 using monitoring results collected under this subpart and determine that each LRAA does not exceed the MCL. If you fail to complete four consecutive quarters of monitoring, you must calculate compliance with the MCL based on the average of the available data from the most recent four quarters. If you take more than one sample per quarter at a monitoring location, you must average all samples taken in the quarter at that location to determine a quarterly average to be used in the LRAA calculation.

b. PWS Required to Monitor Yearly or Less Frequently. To determine compliance with the MCLs in § 1.8.1 of this Part, you must determine that each sample taken is less than the MCL. If any sample exceeds the MCL, you must comply with the requirements of § 1.8.10(F) of this Part. If no sample exceeds the MCL, the sample result for each monitoring location is considered the LRAA for that monitoring location.

5. Violation. You are in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if you fail to monitor.

B. Routine Monitoring

1. Monitoring

a. If you submitted an IDSE report, you must begin monitoring at the locations and months you have recommended in your IDSE report submitted under § 1.8.9(F) of this Part following the schedule in § 1.8.10(A)(3) of this Part, unless the Director requires other locations or additional locations after its review. If you submitted a 40/30 certification under § 1.8.9(D) of this Part or you qualified for a very small system waiver under § 1.8.9(E) of this Part or you are a non-transient non-community PWS serving < 10,000, you must monitor at the location(s) and dates identified in your monitoring plan in § 1.8.5(F) of this Part, updated as required by § 1.8.10(C) of this Part.

b. You must monitor at no fewer than the number of locations identified in the table below.

Source Water Type	Population Size Category	Monitoring Frequency	Distribution system monitoring location per monitoring period
§ 1.6	Less than 500	Per year	2
	500-3,300	Per quarter	2
	3,301-9,999	Per quarter	2
	10,000-49,999	Per quarter	4
	50,000-249,999	Per quarter	8
	250,000-999,999	Per quarter	12
	1,000,000-4,999,999	Per quarter	16
	Greater than or equal to 5,000,000	Per quarter	20
Ground Water	Less than 500	Per year	2
	500-9,999	Per year	2
	10,000-99,999	Per quarter	4
	1,000,000-4,999,999	Per quarter	6
	Greater than or equal to 5,000,000	Per quarter	8

(1) All PWS must monitor during month of highest DBP concentrations.

(2) PWS on quarterly monitoring must take dual sample sets every ninety (90) days at each monitoring location, except for § 1.6 PWS serving 500-3,300. Groundwater PWS serving 500-9,999 on annual monitoring must take dual sample sets at each monitoring location. All other PWS on annual monitoring and § 1.6 PWS serving 500-3,300 are required to take individual TTHM and HAA5 samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. For PWS serving fewer than five hundred (500) people, only one (1) location with a dual sample set per monitoring period is needed if the highest TTHM and HAA5 concentrations occur at the same location and month.

c. If you are an undisinfected PWS that begins using a disinfectant other than UV light after the dates in § 1.8.9 of this Part for complying with the Initial Distribution System Evaluation requirements, you must consult with the Director to identify compliance monitoring locations for § 1.8.10 of this Part. You must then develop a monitoring plan under § 1.8.10(C) of this Part, that includes those monitoring locations.

2. Analytical Methods. You must use an approved method listed in § 1.8.4 of this Part for TTHM and HAA5 analyses in § 1.8.10 of this Part. Analyses must be conducted by laboratories that have received certification by EPA or the Director as specified in § 1.8.4 of this Part.

C. Monitoring Plan

1. You must develop and implement a monitoring plan to be kept on file for Director and public review. The monitoring plan must contain the elements in §§ 1.8.10(C)(1)(a) through (d) of this Part and be complete no later than the date you conduct your initial monitoring under this subpart.

a. Monitoring locations;

b. Monitoring dates;

c. Compliance calculation procedures; and

d. Monitoring plans for any other PWS in the combined distribution system if the Director has reduced monitoring requirements under the Director's authority.

e. If you were not required to submit an IDSE report under either §§ 1.8.9(B) or 1.8.9(C) of this Part, and you do not have sufficient § 1.8 of this Part monitoring locations to identify the required number of § 1.8.10 of this Part compliance monitoring locations indicated in § 1.8.9(F)(2) of this Part, you must identify additional locations by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of compliance monitoring locations have been identified. You must also provide the rationale for identifying the locations as having high levels of TTHM or HAA5. If you have more § 1.8 of this Part monitoring locations than required for § 1.8.10 of this Part compliance monitoring in § 1.8.9(F)(2) of this Part, you must identify which locations you will use for § 1.8.10 of this Part compliance monitoring by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of § 1.8.10 of this Part compliance monitoring locations have been identified.

2. If you are a § 1.6 PWS serving > 3,300 people, you must submit a copy of your monitoring plan to the Director prior to the date you conduct your initial monitoring under this subpart, unless your IDSE report submitted under § 1.8.9 of this Part, contains all the information required by this Section.

3. You may revise your 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 Director-approved reasons, after consultation with the Director regarding the need for changes and the appropriateness of changes. If you change monitoring locations, you 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 Director may also require modifications in your monitoring plan. If you are a § 1.6 PWS serving > 3,300 people, you must submit a copy of your modified monitoring plan to the Director prior to the date you are required to comply with the revised monitoring plan.

D. Reduced Monitoring

1. You may reduce monitoring to the level specified in the table below any time the LRAA is [LESS THAN OR EQUAL TO] 0.040 mg/L for TTHM and [LESS THAN OR EQUAL TO] 0.030 mg/L for HAA5 at all monitoring locations. You may only use data collected under the provisions of §§ 1.8.5 or 1.8.10 of this Part to qualify for reduced monitoring. In addition, the source water annual average TOC level, before any treatment, must be [LESS THAN OR EQUAL TO] 4.0 mg/L at each treatment plant treating surface water or groundwater under the direct influence of surface water, based on monitoring conducted under either §§ 1.8.5(B)(1)(c) or 1.8.5(D) of this Part.

Source Water Type	Population Size Category	Monitoring Frequency	Distribution system monitoring location per monitoring period
§ 1.6	Less than 500		Monitoring may not be reduced
	500-3,300	Per year	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; 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter
	3,301-9,999	Per year	2 dual sample sets: 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
	10,000-49,999	Per quarter	2 dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs
	50,000-249,999	Per quarter	4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs
	250,000-999,999	Per quarter	6 dual sample sets at locations with the three highest TTHM and three highest HAA5 LRAAs
	1,000,000-4,999,999	Per quarter	8 dual sample sets at the locations with the four highest TTHM and four highest HAA5 LRAAs
	Greater than or equal to 5,000,000	Per quarter	10 dual sample sets at the locations with the five highest TTHM and five highest HAA5 LRAAs
Ground Water	Less than 500	Every third year	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; 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter
	500-9,999	Per year	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; 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter
	10,000-99,999	Per year	2 dual sample sets: 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
	1,000,000-4,999,999	Per quarter	2 dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs
	Greater than or equal to 5,000,000	Per quarter	4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs

a. Systems on quarterly monitoring must take dual sample sets every 90 days.

2. You may remain on reduced monitoring as long as the TTHM LRAA [LESS THAN OR EQUAL TO] 0.040 mg/L and the HAA5 LRAA [LESS THAN OR EQUAL TO] 0.030 mg/L at each monitoring location (for PWS with quarterly reduced monitoring) or each TTHM sample [LESS THAN OR EQUAL TO] 0.060 mg/L and each HAA5 sample [LESS THAN OR EQUAL TO] 0.045 mg/L (for PWS with annual or less frequent monitoring). In addition, the source water annual average TOC level, before any treatment, must be [LESS THAN OR EQUAL TO] 4.0 mg/L at each treatment plant treating surface water or groundwater under the direct influence of surface water, based on monitoring conducted under either §§ 1.8.5(B)(1)(c) or 1.8.5(D) of this Part.

3. 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 groundwater under the direct influence of surface water, you must resume routine monitoring under § 1.8.10(B) of this Part or begin increased monitoring if § 1.8.10(F) of this Part applies.

4. The Director may return your PWS to routine monitoring at the Director's discretion.

E. Additional Requirements for Consecutive PWS. If you are a consecutive PWS that does not add a disinfectant but delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light, you must comply with analytical and monitoring requirements for chlorine and chloramines in §§ 1.8.4(C) and 1.8.5(C)(2) of this Part and the compliance requirements in § 1.8.6(C)(1) of this Part, beginning April 1, 2009, unless required earlier by the Director, and report monitoring results under § 1.8.7(C) of this Part.

F. Conditions Requiring Increased Monitoring

1. If you are required to monitor at a particular location annually or less frequently than annually under §§ 1.8.10(B) or 1.8.10(D) of this Part, you must increase monitoring to dual sample sets once per quarter (taken every 90 days) at all locations if a TTHM sample is >0.080 mg/L or a HAA5 sample is >0.060 mg/L at any location.

2. You are in violation of the MCL when the LRAA exceeds the MCLs in § 1.8.1 of this Part, calculated based on four consecutive quarters of monitoring (or the LRAA calculated based on fewer than four quarters of data if the MCL would be exceeded regardless of the monitoring results of subsequent quarters). You are in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if you fail to monitor.

3. You may return to routine monitoring once you have conducted increased monitoring for at least four consecutive quarters and the LRAA for every monitoring location is [LESS THAN OR EQUAL TO] 0.060 mg/L for TTHM and [LESS THAN OR EQUAL TO] 0.045 mg/L for HAA5.

G. Operational Evaluation Levels

1. You have exceeded the operational evaluation level at any monitoring location where the sum of the two previous quarters' TTHM results plus twice the current quarter's TTHM result, divided by 4 to determine an average, exceeds 0.080 mg/L, or where the sum of the two previous quarters' HAA5 results plus twice the current quarter's HAA5 result, divided by 4 to determine an average, exceeds 0.060 mg/L.

2. If you exceed the operational evaluation level, you must conduct an operational evaluation and submit a written report of the evaluation to the Director no later than 90 days after being notified of the analytical result that causes you to exceed the operational evaluation level. The written report must be made available to the public upon request.

a. Your operational evaluation must include an examination of PWS 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 exceedances.

(1) You may request and the Director may allow you to limit the scope of your evaluation if you are able to identify the cause of the operational evaluation level exceedance.

(2) Your request to limit the scope of the evaluation does not extend the schedule in § 1.8.10(G)(2) of this Part, for submitting the written report. The Director must approve this limited scope of evaluation in writing and you must keep that approval with the completed report.

H. Requirements for Remaining on Reduced TTHM and HAA5 Monitoring Based on Stage 1 Results

1. You may remain on reduced monitoring after the dates identified in § 1.8.10(A)(3) of this Part for compliance with § 1.8.10 of this Part only if you qualify for a 40/30 certification under § 1.8.9(D) of this Part or have received a very small system waiver under § 1.8.9(E) of this Part, plus you meet the reduced monitoring criteria in § 1.8.10(D)(1) of this Part, and you do not change or add monitoring locations from those used for compliance monitoring under § 1.8.5 of this Part. If your monitoring locations under § 1.8.10 of this Part differ from your monitoring locations under § 1.8.5 of this Part, you may not remain on reduced monitoring after the dates identified in § 1.8.10(A)(3) of this Part for compliance with § 1.8.10 of this Part.

I. Requirements for Remaining on Increased TTHM and HAA5 Monitoring Based on Stage 1 Results

1. If you were on increased monitoring under § 1.8.5(B)(1) of this Part, you must remain on increased monitoring until you qualify for a return to routine monitoring under § 1.8.10(F)(3) of this Part. You must conduct increased monitoring under § 1.8.10(F) of this Part, at the monitoring locations in the monitoring plan developed under § 1.8.10(C) of this Part, beginning at the date identified in § 1.8.10(A)(3) of this Part, for compliance with § 1.8.10 of this Part and remain on increased monitoring until you qualify for a return to routine monitoring under § 1.8.10(F)(3) of this Part.

J. Reporting and Recordkeeping Requirements

1. Reporting

a. You must report the following information for each monitoring location to the Director within 10 days of the end of any quarter in which monitoring is required:

(1) Number of samples taken during the last quarter.

(2) Date and results of each sample taken during the last quarter.

(3) Arithmetic average of quarterly results for the last four quarters for each monitoring location (LRAA), beginning at the end of the fourth calendar quarter that follows the compliance date and at the end of each subsequent quarter. 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, you must report this information to the Director as part of the first report due following the compliance date or anytime thereafter that this determination is made. If you are required to conduct monitoring at a frequency that is less than quarterly, you must make compliance calculations beginning with the first compliance sample taken after the compliance date, unless you are required to conduct increased monitoring under § 1.8.10(F) of this Part.

(4) Whether, based on §§ 1.8.1 and 1.8.10 of this Part, the MCL was violated at any monitoring location.

(5) Any operational evaluation levels that were exceeded during the quarter and, if so, the location and date, and the calculated TTHM and HAA5 levels.

b. If you are a § 1.6 PWS seeking to qualify for or remain on reduced TTHM/HAA5 monitoring, you must report the following source water TOC information for each treatment plant that treats surface water or groundwater under the direct influence of surface water to the Director within 10 days of the end of any quarter in which monitoring is required:

(1) The number of source water TOC samples taken each month during last quarter.

(2) The date and result of each sample taken during last quarter.

(3) The quarterly average of monthly samples taken during last quarter or the result of the quarterly sample.

(4) The running annual average (RAA) of quarterly averages from the past four quarters.

(5) Whether the RAA exceeded 4.0 mg/L.

c. The Director may choose to perform calculations and determine whether the MCL was exceeded or the PWS is eligible for reduced monitoring in lieu of having the PWS report that information

2. Recordkeeping. You must retain any § 1.8.10 of this Part monitoring plans and your § 1.8.10 of this Part monitoring results as required by § 1.11 of this Part.

216 R.I. Code R. 216-RICR-50-05-1.8

Amended effective 9/18/2024