16 Del. Admin. Code § 4462-20.0

Current through Register Vol. 28, No. 7, January 1, 2025

Section 4462-20.0 - Enhanced Treatment for Cryptosporidium

20.1 General requirements for the Long Term 2 Enhanced Surface Water Treatment Rule.

20.1.1 The requirements of Section 20.0 are national primary drinking water regulations. The regulations in this section establish or extend treatment technique requirements in lieu of maximum contaminant levels for Cryptosporidium. These requirements are in addition to requirements for filtration and disinfection in Sections 16.0, 17.0, and 19.0 of these regulations.

20.1.2 Applicability. The requirements of this section apply to all subpart H systems, which are public water systems supplied by a surface water source and public water systems supplied by a ground water source under the direct influence of surface water.

20.1.2.1 Wholesale systems, as defined in Section 1.0, must comply with the requirements of this section based on the population of the largest system in the combined distribution system.

20.1.2.2 The requirements of this section for filtered systems apply to systems required by National Primary Drinking Water Regulations to provide filtration treatment, whether or not the system is currently operating a filtration system.

20.1.2.3 The requirements of this section for unfiltered systems apply only to unfiltered systems that timely met and continue to meet the filtration avoidance criteria in Sections 16.0, 17.0, and 19.0 of this regulation, as applicable.

20.1.3 Requirements. Systems subject to this section must comply with the following requirements:

20.1.3.1 Systems must conduct an initial and a second round of source water monitoring for each plant that treats a surface water or GWUDI source. This monitoring may include sampling for Cryptosporidium, E. coli, and turbidity as described in subsections 20.2 through 20.7, to determine what level, if any, of additional Cryptosporidium treatment they must provide.

20.1.3.2 Systems that plan to make a significant change to their disinfection practice must develop disinfection profiles and calculate disinfection benchmarks, as described in subsections 20.9 through 20.10.

20.1.3.3 Filtered systems must determine their Cryptosporidium treatment bin classification as described in subsection 20.11 and provide additional treatment for Cryptosporidium, if required, as described in subsection 20.12. All unfiltered systems must provide treatment for Cryptosporidium as described in subsection 20.13. Filtered and unfiltered systems must implement Cryptosporidium treatment according to the schedule in subsection 20.14.

20.1.3.4 Systems with uncovered finished water storage facilities must comply with the requirements to cover the facility or treat the discharge from the facility as described in subsection 20.15.

20.1.3.5 Systems required to provide additional treatment for Cryptosporidium must implement microbial toolbox options that are designed and operated as described in subsections 20.16 through 20.21.

20.1.3.6 Systems must comply with the applicable recordkeeping and reporting requirements described in subsections 20.22 through 20.23.

20.1.3.7 Systems must address significant deficiencies identified in sanitary surveys performed by the Division as described in subsection 20.24.

20.2 Source water monitoring.

20.2.1 Initial round of source water monitoring. Systems must conduct the following monitoring on the schedule in subsection 20.4 of this section unless they meet the monitoring exemption criteria in subsection 20.2.3.

20.2.1.1 Filtered systems serving at least 10,000 people must sample their source water for Cryptosporidium, E. coli, and turbidity at least monthly for 24 months.

20.2.1.2 Unfiltered systems serving at least 10,000 people must sample their source water for Cryptosporidium at least monthly for 24 months.

20.2.1.3 Filtered Systems

20.2.1.3.1 Filtered systems serving fewer than 10,000 people must sample their source water for E. coli at least once every two weeks for 12 months.

20.2.1.3.2 A filtered system serving fewer than 10,000 people may avoid E. coli monitoring if the system notifies the Division that it will monitor for Cryptosporidium as described in subsection 20.2.1.4. The system must notify the Division no later than 3 months prior to the date the system is otherwise required to start E. coli monitoring under subsection 20.2.3.

20.2.1.4 Filtered systems serving fewer than 10,000 people must sample their source water for Cryptosporidium at least twice per month for 12 months or at least monthly for 24 months if they meet one of the following, based on monitoring conducted under subsection 20.2.1.3.1:

20.2.1.4.1 For systems using lake/reservoir sources, the annual mean E. coli concentration is greater than 10 E. coli/100 mL.

20.2.1.4.2 For systems using flowing stream sources, the annual mean E. coli concentration is greater than 50 E. coli/100 mL.

20.2.1.4.3 The system does not conduct E. coli monitoring as described in subsection 20.2.1.3.1.

20.2.1.4.4 Systems using ground water under the direct influence of surface water (GWUDI) must comply with the requirements of subsection 20.2.1.4 based on the E. coli level that applies to the nearest surface water body. If no surface water body is nearby, the system must comply based on the requirements that apply to systems using lake/reservoir sources.

20.2.1.5 For filtered systems serving fewer than 10,000 people, the Division may approve monitoring for an indicator other than E. coli under subsections 20.2.1.3.1 and 20.2.1.3.2. The Division also may approve an alternative to the E. coli concentration in subsections 20.2.1.4.1, 20.2.1.4.2 or 20.2.1.4.4 of this section to trigger Cryptosporidium monitoring. This approval by the Division must be provided to the system in writing and must include the basis for the Division's determination that the alternative indicator and/or trigger level will provide a more accurate identification of whether a system will exceed the Bin 1 Cryptosporidium level in subsection 20.11.

20.2.1.6 Unfiltered systems serving fewer than 10,000 people must sample their source water for Cryptosporidium at least twice per month for 12 months or at least monthly for 24 months.

20.2.1.7 Systems may sample more frequently than required under this section if the sampling frequency is evenly spaced throughout the monitoring period.

20.2.2 Second round of source water monitoring. Systems must conduct a second round of source water monitoring that meets the requirements for monitoring parameters, frequency, and duration described in subsection 20.2.1, unless they meet the monitoring exemption criteria in subsection 20.2.4. Systems must conduct this monitoring on the schedule in subsection 20.2.3.

20.2.3 Monitoring schedule. Systems must begin the monitoring required in subsections 20.2.1 and 20.2.2 no later than the month beginning with the date listed in this table:

Source Water Monitoring Starting Dates Table

Systems that serve	Must begin the first round of source water monitoring no later than the month beginning...	And must begin the second round of source water monitoring no later than the month beginning ...
At least 100,000 people	October 1, 2006	April 1, 2015
From 50,000 to 99,999 people	April 1, 2007	October 1, 2015
From 10,000 to 49,999 people	April 1, 2008	October 1, 2016
Fewer than 10,000 and monitor for E. coli¹	October 1, 2008	October 1, 2017
Fewer than 10,000 and monitor for Cryptosporidium²	April 1, 2010	April 1, 2019

¹ Applies only to filtered systems.

² Applies to filtered systems that meet the conditions of subsection 20.2.1.4 and unfiltered systems.

20.2.4 Monitoring avoidance.

20.2.4.1 Filtered systems are not required to conduct source water monitoring under this section if the system will provide a total of at least 5.5-log of treatment for Cryptosporidium, equivalent to meeting the treatment requirements of Bin 4 in subsection 20.12.

20.2.4.2 Unfiltered systems are not required to conduct source water monitoring under this section if the system will provide a total of at least 3-log Cryptosporidium inactivation, equivalent to meeting the treatment requirements for unfiltered systems with a mean Cryptosporidium concentration of greater than 0.01 oocysts/L in subsection 20.13.

20.2.4.3 If a system chooses to provide the level of treatment in subsections 20.2.4.1 or 20.2.4.2, as applicable, rather than start source water monitoring, the system must notify the Division in writing no later than the date the system is otherwise required to submit a sampling schedule for monitoring under subsection 20.3. Alternatively, a system may choose to stop sampling at any point after it has initiated monitoring if it notifies the Division in writing that it will provide this level of treatment. Systems must install and operate technologies to provide this level of treatment by the applicable treatment compliance date in subsection 20.14.

20.2.5 Plants operating only part of the year. Systems with surface water or ground water under the direct influence of surface water plants that operate for only part of the year must conduct source water monitoring in accordance with this section, but with the following modifications:

20.2.5.1 Systems must sample their source water only during the months that the plant operates unless the Division specifies another monitoring period based on plant operating practices.

20.2.5.2 Systems with plants that operate less than six months per year and that monitor for Cryptosporidium must collect at least six Cryptosporidium samples per year during each of two years of monitoring. Samples must be evenly spaced throughout the period the plant operates.

20.2.6 New sources.

20.2.6.1 A system that begins using a new source of surface water or GWUDI after the system is required to begin monitoring under subsection 20.2.3 must monitor the new source on a schedule the Division approves. Source water monitoring must meet the requirements of this section. The system must also meet the bin classification and Cryptosporidium treatment requirements of subsections 20.11 and 20.12 or subsection 20.13, as applicable, for the new source on a schedule the Division approves.

20.2.6.2 The requirements of subsection 20.2.6 apply to surface water or ground water under the direct influence of surface water systems that begin operation after the monitoring start date applicable to the system's size under subsection 20.2.3.

20.2.6.3 The system must begin a second round of source water monitoring no later than 6 years following initial bin classification under subsection 20.11 or determination of the mean Cryptosporidium level under subsection 20.13 as applicable.

20.2.7 Failure to collect any source water sample required under this section in accordance with the sampling schedule, sampling location, analytical method, approved laboratory, and reporting requirements of subsections 20.3 through 20.7 is a monitoring violation.

20.2.8 Grandfathering monitoring data. Systems may use (grandfather) monitoring data collected prior to the applicable monitoring start date in subsection 20.2.3 to meet the initial source water monitoring requirements in subsection 20.2.1. Grandfathered data may substitute for an equivalent number of months at the end of the monitoring period. All data submitted under this paragraph must meet the requirements in subsection 20.8.

20.3 Sampling schedules.

20.3.1 Systems required to conduct source water monitoring under subsection 20.2 must submit a sampling schedule that specifies the calendar dates when the system will collect each required sample.

20.3.1.1 Systems must submit sampling schedules no later than 3 months prior to the applicable date listed in subsection 20.2.3 for each round of required monitoring.

20.3.1.1.1 Systems serving at least 10,000 people must submit their sampling schedule for the initial round of source water monitoring under subsection 20.2.1 to EPA electronically at https://intranet.epa.gov/lt2/.

20.3.1.1.2 If a system is unable to submit the sampling schedule electronically, the system may use an alternative approach for submitting the sampling schedule that EPA approves.

20.3.1.2 Systems serving fewer than 10,000 people must submit their sampling schedules for the initial round of source water monitoring under subsection 20.2.1 to the Division.

20.3.1.3 Systems must submit sampling schedules for the second round of source water monitoring conducted under subsection 20.2.2 to the Division.

20.3.1.4 If EPA or the Division does not respond to a system regarding its sampling schedule, the system must sample at the reported schedule.

20.3.2 Systems must collect samples within two days before or two days after the dates indicated in their sampling schedule (i.e., within a five-day period around the schedule date) unless one of the conditions of subsections 20.3.2.1 or 20.3.2.1.1 applies.

20.3.2.1 If an extreme condition or situation exists that may pose danger to the sample collector, or that cannot be avoided and causes the system to be unable to sample in the scheduled five-day period, the system must sample as close to the scheduled date as is feasible unless the Division approves an alternative sampling date. The system must submit an explanation for the delayed sampling date to the Division concurrent with the shipment of the sample to the laboratory.

20.3.2.1.1 If a system is unable to report a valid analytical result for a scheduled sampling date due to equipment failure, loss of or damage to the sample, failure to comply with the analytical method requirements, including the quality control requirements in subsection 20.5, or the failure of an approved laboratory to analyze the sample, then the system must collect a replacement sample.

20.3.2.1.2 The system must collect the replacement sample not later than 21 days after receiving information that an analytical result cannot be reported for the scheduled date unless the system demonstrates that collecting a replacement sample within this time frame is not feasible or the Division approves an alternative resampling date. The system must submit an explanation for the delayed sampling date to the Division concurrent with the shipment of the sample to the laboratory.

20.3.3 Systems that fail to meet the criteria of subsection 20.3.2 of this subsection for any source water sample required under subsection 20.2 must revise their sampling schedules to add dates for collecting all missed samples. Systems must submit the revised schedule to the Division for approval prior to when the system begins collecting the missed samples.

20.4 Sampling locations.

20.4.1 Systems required to conduct source water monitoring under subsection 20.2 must collect samples for each plant that treats a surface water or GWUDI source. Where multiple plants draw water from the same influent, such as the same pipe or intake, the Division may approve one set of monitoring results to be used to satisfy the requirements of subsection 20.2 for all plants.

20.4.2 Source water samples

20.4.2.1 Systems must collect source water samples prior to chemical treatment, such as coagulants, oxidants and disinfectants, unless the system meets the condition of subsection 20.4.2.2.

20.4.2.2 The Division may approve a system to collect a source water sample after chemical treatment. To grant this approval, the Division must determine that collecting a sample prior to chemical treatment is not feasible for the system and that the chemical treatment is unlikely to have a significant adverse effect on the analysis of the sample.

20.4.3 Systems that recycle filter backwash water must collect source water samples prior to the point of filter backwash water addition.

20.4.4 Bank filtration.

20.4.4.1 Systems that receive Cryptosporidium treatment credit for bank filtration under subsections 10.4.4 or 10.4.5, as applicable, must collect source water samples in the surface water prior to bank filtration.

20.4.4.2 Systems that use bank filtration as pretreatment to a filtration plant must collect source water samples from the well (i.e., after bank filtration). Use of bank filtration during monitoring must be consistent with routine operational practice. Systems collecting samples after a bank filtration process may not receive treatment credit for the bank filtration under subsection 20.18.3.

20.4.5 Multiple sources. Systems with plants that use multiple water sources, including multiple surface water sources and blended surface water and ground water sources, must collect samples as specified in subsections 20.4.5.1 or 20.4.5.2. The use of multiple sources during monitoring must be consistent with routine operational practice.

20.4.5.1 If a sampling tap is available where the sources are combined prior to treatment, systems must collect samples from the tap.

20.4.5.2 If a sampling tap where the sources are combined prior to treatment is not available, systems must collect samples at each source near the intake on the same day and must follow either subsections 20.4.5.2.1 or 20.4.5.2.2 of this subsection for sample analysis.

20.4.5.2.1 Systems may composite samples from each source into one sample prior to analysis. The volume of sample from each source must be weighted according to the proportion of the source in the total plant flow at the time the sample is collected.

20.4.5.2.2 Systems may analyze samples from each source separately and calculate a weighted average of the analysis results for each sampling date. The weighted average must be calculated by multiplying the analysis result for each source by the fraction the source contributed to total plant flow at the time the sample was collected and then summing these values.

20.4.6 Additional Requirements. Systems must submit a description of their sampling location(s) to the Division at the same time as the sampling schedule required under subsection 20.3. This description must address the position of the sampling location in relation to the system's water source(s) and treatment processes, including pretreatment, points of chemical treatment, and filter backwash recycle. If the Division does not respond to a system regarding sampling location(s), the system must sample at the reported location(s).

20.5 Analytical methods.

20.5.1Cryptosporidium. Systems must analyze for Cryptosporidium using Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 2005, United States Environmental Protection Agency, EPA-815-R-05-002 or Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2005, United States Environmental Protection Agency, EPA-815-R-05-001, which are incorporated by reference. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 . You may obtain a copy of these methods online from the United States Environmental Protection Agency, Office of Ground Water and Drinking Water, 1201 Constitution Ave., NW, Washington, DC 20460 (Telephone: 800-426-4791). You may inspect a copy at the Water Docket in the EPA Docket Center, 1301 Constitution Ave., NW, Washington, DC, (Telephone: 202-566-2426) or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

20.5.1.1 Systems must analyze at least a 10 L sample or a packed pellet volume of at least 2 mL as generated by the methods listed in subsection 20.5.1. Systems unable to process a 10 L sample must analyze as much sample volume as can be filtered by two filters approved by EPA for the methods listed in subsection 20.5.1, up to a packed pellet volume of at least 2 mL.

20.5.1.2 Matrix Spike samples

20.5.1.2.1 Matrix spike (MS) samples, as required by the methods in subsection 20.5.1, must be spiked and filtered by a laboratory approved for Cryptosporidium analysis under subsection 20.5.

20.5.1.2.2 If the volume of the MS sample is greater than 10 L, the system may filter all but 10 L of the MS sample in the field, and ship the filtered sample and the remaining 10 L of source water to the laboratory. In this case, the laboratory must spike the remaining 10 L of water and filter it through the filter used to collect the balance of the sample in the field.

20.5.1.3 Flow cytometer-counted spiking suspensions must be used for MS samples and ongoing precision and recovery (OPR) samples.

20.5.2E. coli. Systems must use methods for enumeration of E. coli in source water approved in subsection 16.6.

20.5.2.1 The time from sample collection to initiation of analysis may not exceed 30 hours unless the system meets the condition of subsection 20.5.2.2.

20.5.2.2 The Division may approve on a case-by-case basis the holding of an E. coli sample for up to 48 hours between sample collection and initiation of analysis if the Division determines that analyzing an E. coli sample within 30 hours is not feasible. E. coli samples held between 30 to 48 hours must be analyzed by the Colilert reagent version of Standard Method 9223B as listed in subsection 10.6 of this regulation.

20.5.2.3 Systems must maintain samples between 0ºC and 10ºC during storage and transit to the laboratory.

20.5.3 Turbidity. Systems must use methods for turbidity measurement approved in subsection 16.6.

20.6 Approved laboratories.

20.6.1Cryptosporidium. Systems must have Cryptosporidium samples analyzed by a laboratory that is approved under EPA's Laboratory Quality Assurance Evaluation Program for Analysis of Cryptosporidium in Water or a laboratory that has been certified for Cryptosporidium analysis by an equivalent Division laboratory certification program.

20.6.2E. coli. Any laboratory certified by the EPA, the National Environmental Laboratory Accreditation Conference or the Division for total coliform or fecal coliform analysis under subsection 16.6 is approved for E. coli analysis under this subsection when the laboratory uses the same technique for E. coli that the laboratory uses for subsection 16.6.

20.6.3 Turbidity. Measurements of turbidity must be made by a party approved by the Division.

20.7 Reporting source water monitoring results.

20.7.1 Systems must report results from the source water monitoring required under subsection 20.2 no later than 10 days after the end of the first month following the month when the sample is collected.

20.7.2 Electronic Reporting

20.7.2.1 All systems serving at least 10,000 people must report the results from the initial source water monitoring required under subsection 20.2.1 to EPA electronically at https://intranet.epa.gov/lt2/ (dated compliance requirement retained for Federal consistency; link not active).

20.7.2.2 If a system is unable to report monitoring results electronically, the system may use an alternative approach for reporting monitoring results that EPA approves.

20.7.3 Systems serving fewer than 10,000 people must report results from the initial source water monitoring required under subsection 20.2.1 to the Division.

20.7.4 All systems must report results from the second round of source water monitoring required under subsection 20.2.2 to the Division.

20.7.5 Systems must report the applicable information in subsections 20.7.5.1 and 20.7.5.2 for the source water monitoring required under section 20.2.

20.7.5.1 Systems must report the following data elements for each Cryptosporidium analysis:

Data element

PWS ID.

Facility ID.

Sample collection date.

Sample type (field or matrix spike).

Sample volume filtered (L), to nearest 1/4\ L.

Was 100% of filtered volume examined.

Number of oocysts counted.

20.7.5.1.1 For matrix spike samples, systems must also report the sample volume spiked and estimated number of oocysts spiked. These data are not required for field samples.

20.7.5.1.2 For samples in which less than 10 L is filtered or less than 100% of the sample volume is examined, systems must also report the number of filters used and the packed pellet volume.

20.7.5.1.3 For samples in which less than 100% of sample volume is examined, systems must also report the volume of resuspended concentrate and volume of this resuspension processed through immunomagnetic separation.

20.7.5.2 Systems must report the following data elements for each E. coli analysis:

Data element

PWS ID.

Facility ID.

Sample collection date.

Analytical method number.

Method type.

Source type (flowing stream, lake/reservoir, GWUDI).

E. coli/100 mL.

Turbidity.1

¹ Systems serving fewer than 10,000 people that are not required to monitor for turbidity under subsection 20.2 are not required to report turbidity with their E. coli results.

20.8 Grandfathering previously collected data.

20.8.1 Grandfathering

20.8.1.1 Systems may comply with the initial source water monitoring requirements of subsection 20.2.1 by grandfathering sample results collected before the system is required to begin monitoring (i.e., previously collected data). To be grandfathered, the sample results and analysis must meet the criteria in this section and the Division must approve.

20.8.1.2 A filtered system may grandfather Cryptosporidium samples to meet the requirements of subsection 20.2.1 when the system does not have corresponding E. coli and turbidity samples. A system that grandfathers Cryptosporidium samples without E. coli and turbidity samples is not required to collect E. coli and turbidity samples when the system completes the requirements for Cryptosporidium monitoring under subsection 20.2.1.

20.8.2E. coli sample analysis. The analysis of E. coli samples must meet the analytical method and approved laboratory requirements of subsections 20.5 through 20.6.

20.8.3Cryptosporidium sample analysis. The analysis of Cryptosporidium samples must meet the criteria in this paragraph.

20.8.3.1 Laboratories analyzed Cryptosporidium samples using one of the analytical methods in subsections 20.8.3.1.1 through 20.8.3.1.6, which are incorporated by reference. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 . You may obtain a copy of these methods on-line from the United States Environmental Protection Agency, Office of Ground Water and Drinking Water, 1201 Constitution Ave, NW, Washington, DC 20460 (Telephone: 800-426-4791). You may inspect a copy at the Water Docket in the EPA Docket Center, 1301 Constitution Ave., NW, Washington, DC, (Telephone: 202-566-2426) or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code--of--federal--regulations/ibr--locations.html.

20.8.3.1.1Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 2005, United States Environmental Protection Agency, EPA-815-R-05-002.

20.8.3.1.2Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2005, United States Environmental Protection Agency, EPA-815-R-05-001.

20.8.3.1.3Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 2001, United States Environmental Protection Agency, EPA-821-R-01-025.

20.8.3.1.4Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2001, United States Environmental Protection Agency, EPA-821--R-01-026.

20.8.3.1.5Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 1999, United States Environmental Protection Agency, EPA-821-R-99-006.

20.8.3.1.6Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 1999, United States Environmental Protection Agency, EPA-821-R-99-001.

20.8.3.2 For each Cryptosporidium sample, the laboratory analyzed at least 10 L of sample or at least 2 mL of packed pellet or as much volume as could be filtered by 2 filters that EPA approved for the methods listed in subsection 20.8.3.1.

20.8.4 Sampling location. The sampling location must meet the conditions in subsection 20.4.

20.8.5 Sampling frequency. Cryptosporidium samples were collected no less frequently than each calendar month on a regular schedule, beginning no earlier than January 1999. Sample collection intervals may vary for the conditions specified in subsections 20.3.2.1 and 20.3.2.2 if the system provides documentation of the condition when reporting monitoring results.

20.8.5.1 The Division may approve grandfathering of previously collected data where there are time gaps in the sampling frequency if the system conducts additional monitoring the Division specifies to ensure that the data used to comply with the initial source water monitoring requirements of subsection 20.2.1 are seasonally representative and unbiased.

20.8.5.2 Systems may grandfather previously collected data where the sampling frequency within each month varied. If the Cryptosporidium sampling frequency varied, systems must follow the monthly averaging procedure in subsections 20.11.2.5 or 20.13.1.3, as applicable, when calculating the bin classification for filtered systems or the mean Cryptosporidium concentration for unfiltered systems.

20.8.6 Reporting monitoring results for grandfathering. Systems that request to grandfather previously collected monitoring results must report the following information by the applicable dates listed in this paragraph. Systems serving at least 10,000 people must report this information to EPA unless the Division approves reporting to the Division rather than EPA. Systems serving fewer than 10,000 people must report this information to the Division.

20.8.6.1 Systems must report that they intend to submit previously collected monitoring results for grandfathering. This report must specify the number of previously collected results the system will submit, the dates of the first and last sample, and whether a system will conduct additional source water monitoring to meet the requirements of subsection 20.2.1. Systems must report this information no later than the date the sampling schedule under subsection 20.3 is required.

20.8.6.2 Systems must report previously collected monitoring results for grandfathering, along with the associated documentation listed in subsections 20.8.6.2.1 through 20.8.6.2.4, no later than two months after the applicable date listed in subsection 20.2.3.

20.8.6.2.1 For each sample result, systems must report the applicable data elements in subsection 20.8.

20.8.6.2.2 Systems must certify that the reported monitoring results include all results the system generated during the time period beginning with the first reported result and ending with the final reported result. This applies to samples that were collected from the sampling location specified for source water monitoring under this section, not spiked, and analyzed using the laboratory's routine process for the analytical methods listed in this section.

20.8.6.2.3 Systems must certify that the samples were representative of a plant's source water(s) and the source water(s) have not changed. Systems must report a description of the sampling location(s), which must address the position of the sampling location in relation to the system's water source(s) and treatment processes, including points of chemical addition and filter backwash recycle.

20.8.6.2.4 For Cryptosporidium samples, the laboratory or laboratories that analyzed the samples must provide a letter certifying that the quality control criteria specified in the methods listed in subsection 20.8.3.1 were met for each sample batch associated with the reported results. Alternatively, the laboratory may provide bench sheets and sample examination report forms for each field, matrix spike, IPR, OPR, and method blank sample associated with the reported results.

20.8.7 If the Division determines that a previously collected data set submitted for grandfathering was generated during source water conditions that were not normal for the system, such as a drought, the Division may disapprove the data. Alternatively, the Division may approve the previously collected data if the system reports additional source water monitoring data, as determined by the Division, to ensure that the data set used under subsections 20.11 or 20.13 represents average source water conditions for the system.

20.8.8 If a system submits previously collected data that fully meet the number of samples required for initial source water monitoring under subsection 20.2.1 and some of the data are rejected due to not meeting the requirements of this section, systems must conduct additional monitoring to replace rejected data on a schedule the Division approves. Systems are not required to begin this additional monitoring until two months after notification that data have been rejected and additional monitoring is necessary.

20.9 Requirements when making a significant change in disinfection practice.

20.9.1 Following the completion of initial source water monitoring under subsection 20.2.1, a system that plans to make a significant change to its disinfection practice, as defined in subsection 20.9.2, must develop disinfection profiles and calculate disinfection benchmarks for Giardia lamblia and viruses as described in subsection 20.10. Prior to changing the disinfection practice, the system must notify the Division and must include in this notice the information in subsections 20.9.1.1 through 20.9.1.3;

20.9.1.1 A completed disinfection profile and disinfection benchmark for Giardia lamblia and viruses as described in subsection 20.10;

20.9.1.2 A description of the proposed change in disinfection practice; and

20.9.1.3 An analysis of how the proposed change will affect the current level of disinfection.

20.9.2 Significant changes to disinfection practice are defined as follows:

20.9.2.1 Changes to the point of disinfection;

20.9.2.2 Changes to the disinfectant(s) used in the treatment plant;

20.9.2.3 Changes to the disinfection process; or

20.9.2.4 Any other modification identified by the Division as a significant change to disinfection practice.

20.10 Developing the disinfection profile and benchmark

20.10.1 Systems required to develop disinfection profiles under subsection 20.9 must follow the requirements of this section. Systems must monitor at least weekly for a period of 12 consecutive months to determine the total log inactivation for Giardia lamblia and viruses. If systems monitor more frequently, the monitoring frequency must be evenly spaced. Systems that operate for fewer than 12 months per year must monitor weekly during the period of operation. Systems must determine log inactivation for Giardia lamblia through the entire plant, based on CT99.9 values in Tables 1.1 through 1.6, 2.1 and 3.1 of 40 CFR § 141.74(b) as applicable. Copies are available from the Office of Drinking Water upon request. Systems must determine log inactivation for viruses through the entire treatment plant based on a protocol approved by the Division.

20.10.2 Systems with a single point of disinfectant application prior to the entrance to the distribution system must conduct the monitoring in subsections 20.10.2.1 through 20.10.2.4. Systems with more than one point of disinfectant application must conduct the monitoring in subsections 20.10.2.1 through 20.10.2.4 for each disinfection segment. Systems must monitor the parameters necessary to determine the total inactivation ratio, using analytical methods in subsection 16.6.

20.10.2.1 For systems using a disinfectant other than UV, the temperature of the disinfected water must be measured at each residual disinfectant concentration sampling point during peak hourly flow or at an alternative location approved by the Division.

20.10.2.2 For systems using chlorine, the pH of the disinfected water must be measured at each chlorine residual disinfectant concentration sampling point during peak hourly flow or at an alternative location approved by the Division.

20.10.2.3 The disinfectant contact time(s) (T) must be determined during peak hourly flow.

20.10.2.4 The residual disinfectant concentration(s) (C) of the water before or at the first customer and prior to each additional point of disinfectant application must be measured during peak hourly flow.

20.10.3 In lieu of conducting new monitoring under subsection 20.10.2, systems may elect to meet the requirements of subsection 20.10.3.1 or 20.10.3.2 of this section.

20.10.3.1 Systems that have at least one year of existing data that are substantially equivalent to data collected under the provisions of subsection 20.10.2 may use these data to develop disinfection profiles as specified in this section if the system has neither made a significant change to its treatment practice nor changed sources since the data were collected. Systems may develop disinfection profiles using up to three years of existing data.

20.10.3.2 Systems may use disinfection profile(s) developed under subsection 17.5 or Subpart H systems serving fewer than 10,000 people may use disinfection profiles developed under subsection 19.1 in lieu of developing a new profile if the system has neither made a significant change to its treatment practice nor changed sources since the profile was developed. Systems that have not developed a virus profile under subsection 17.5 or Subpart H systems serving fewer than 10,000 people under subsection 19.1 must develop a virus profile using the same monitoring data on which the Giardia lamblia profile is based.

20.10.4 Systems must calculate the total inactivation ratio for Giardia lamblia as specified in subsections 20.10.4.1 through 20.10.4.3.

20.10.4.1 Systems using only one point of disinfectant application may determine the total inactivation ratio for the disinfection segment based on either of the methods in subsection 20.10.4.1.1 or 20.10.4.1.2.

20.10.4.1.1 Determine one inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly flow.

20.10.4.1.2 Determine successive CTcalc/CT99.9 values, representing sequential inactivation ratios, between the point of disinfectant application and a point before or at the first customer during peak hourly flow. The system must calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values together to determine ([SIGMA](CTcalc/CT99.9)).

20.10.4.2 Systems using more than one point of disinfectant application before the first customer must determine the CT value of each disinfection segment immediately prior to the next point of disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. The (CTcalc/CT99.9) value of each segment and ([SIGMA](CTcalc/CT99.9)) must be calculated using the method in subsection 20.10.4.1.2.

20.10.4.3 The system must determine the total logs of inactivation by multiplying the value calculated in subsections 20.10.4.1 or 20.10.4.2 by 3.0.

20.10.4.4 Systems must calculate the log of inactivation for viruses using a protocol approved by the Division.

20.10.5 Systems must use the procedures specified in subsections 20.10.5.1 and 20.10.5.2 to calculate a disinfection benchmark.

20.10.5.1 For each year of profiling data collected and calculated under subsections 20.10.1 through 20.10.4, systems must determine the lowest mean monthly level of both Giardia lamblia and virus inactivation. Systems must determine the mean Giardia lamblia and virus inactivation for each calendar month for each year of profiling data by dividing the sum of daily or weekly Giardia lamblia and virus log inactivation by the number of values calculated for that month.

20.10.5.2 The disinfection benchmark is the lowest monthly mean value (for systems with one year of profiling data) or the mean of the lowest monthly mean values (for systems with more than one year of profiling data) of Giardia lamblia and virus log inactivation in each year of profiling data.

20.11 Bin classification for filtered systems

20.11.1 Following completion of the initial round of source water monitoring required under subsection 20.2.1, filtered systems must calculate an initial Cryptosporidium bin concentration for each plant for which monitoring was required. Calculation of the bin concentration must use the Cryptosporidium results reported under subsection 20.2.1 and must follow the procedures in subsections 20.11.2.1 through 20.11.2.5.

20.11.2 Bin classification

20.11.2.1 For systems that collect a total of at least 48 samples, the bin concentration is equal to the arithmetic mean of all sample concentrations.

20.11.2.2 For systems that collect a total of at least 24 samples, but not more than 47 samples, the bin concentration is equal to the highest arithmetic mean of all sample concentrations in any 12 consecutive months during which Cryptosporidium samples were collected.

20.11.2.3 For systems that serve fewer than 10,000 people and monitor for Cryptosporidium for only one year (i.e., collect 24 samples in 12 months), the bin concentration is equal to the arithmetic mean of all sample concentrations.

20.11.2.4 For systems with plants operating only part of the year that monitor fewer than 12 months per year under subsection 20.2.5, the bin concentration is equal to the highest arithmetic mean of all sample concentrations during any year of Cryptosporidium monitoring.

20.11.2.5 If the monthly Cryptosporidium sampling frequency varies, systems must first calculate a monthly average for each month of monitoring. Systems must then use these monthly average concentrations, rather than individual sample concentrations, in the applicable calculation for bin classification in subsections 20.11.2.1 through 20.11.2.4.

20.11.3 Filtered systems must determine their initial bin classification from the following table and using the Cryptosporidium bin concentration calculated under subsections 20.11.1 and 20.11.2:

Bin Classification Table for Filtered Systems

For systems that are:

With a Cryptosporidium bin concentration of...¹

The bin classification is...

...required to monitor for Cryptosporidium under subsection 20.2

Cryptosporidium <0.075 oocyst/L.

0.075 oocysts/L Cryptosporidium < 1.0 oocysts/L.

1.0 oocysts/L Cryptosporidium <3.0 oocysts/L

Cryptosporidium [GREATER THEN OR EQUAL TO]3.0 oocysts/L

Bin 1.

Bin 2.

Bin 3.

Bin 4.

...serving fewer than 10,000 people and NOT required to monitor for Cryptosporidium under subsection 20.2.1.4

N/A

Bin 1.

¹ Based on calculations in subsection 20.11.1 or 20.11.4, as applicable.

20.11.4 Following completion of the second round of source water monitoring required under subsection 20.2.2, filtered systems must recalculate their Cryptosporidium bin concentration using the Cryptosporidium results reported under subsection 20.2.2 and following the procedures in subsections 20.11.2.1 through 20.11.2.4. Systems must then re-determine their bin classification using this bin concentration and the table in subsection 20.11.3.

20.11.5 Reporting bin classification

20.11.5.1 Filtered systems must report their initial bin classification under subsection 20.11.3 to the Division for approval no later than 6 months after the system is required to complete initial source water monitoring based on the schedule in subsection 20.3.

20.11.5.2 Systems must report their bin classification under subsection 20.11.4 to the Division for approval no later than 6 months after the system is required to complete the second round of source water monitoring based on the schedule in subsection 20.2.3.

20.11.5.3 The bin classification report to the Division must include a summary of source water monitoring data and the calculation procedure used to determine bin classification.

20.11.6 Failure to comply with the conditions of subsection 20.11.5 is a violation of the treatment technique requirement.

20.12 Filtered system additional Cryptosporidium treatment requirements

20.12.1 Filtered systems must provide the level of additional treatment for Cryptosporidium specified in this paragraph based on their bin classification as determined under subsection 20.11 and according to the schedule in subsection 20.14.

If the system bin classification is...	And the system uses the following filtration treatment in full compliance with Sections 16.0, 17.0 and 19.0 (as applicable), then the additional Cryptosporidium treatment requirements are...
If the system bin classification is...	Conventional filtration treatment (including softening)	Direct filtration	Slow sand or diatomaceous earth filtration	Alternative filtration technologies
Bin 1...	No additional treatment...	No additional treatment...	No additional treatment...	No additional Treatment
Bin 2...	1-log treatment...	1.5-log treatment...	1-log treatment...	(¹)
Bin 3...	2-log treatment...	2.5-log treatment...	2-log treatment...	(²)
Bin 4...	2.5-log treatment...	3-log treatment...	2.5-log treatment...	(³)

¹ As determined by the Division such that the total Cryptosporidium removal and inactivation is at least 4.0-log.

² As determined by the Division such that the total Cryptosporidium removal and inactivation is at least 5.0-log.

³ As determined by the Division such that the total Cryptosporidium removal and inactivation is at least 5.5-log.

20.12.2 Treatment options

20.12.2.1 Filtered systems must use one or more of the treatment and management options listed in subsection 20.16, termed the microbial toolbox, to comply with the additional Cryptosporidium treatment required in subsection 20.12.1.

20.12.2.2 Systems classified in Bin 3 and Bin 4 must achieve at least 1-log of the additional Cryptosporidium treatment required under subsection 20.12.1 using either one or a combination of the following: bag filters, bank filtration, cartridge filters, chlorine dioxide, membranes, ozone, or UV, as described in subsections 20.17 through 20.21.

20.12.3 Failure by a system in any month to achieve treatment credit by meeting criteria in subsections 20.17 through 20.21 for microbial toolbox options that is at least equal to the level of treatment required in subsection 20.12.1 is a violation of the treatment technique requirement.

20.12.4 If the Division determines during a sanitary survey or an equivalent source water assessment that after a system completed the monitoring conducted under subsection 20.2.1 or subsection 20.2.2, significant changes occurred in the system's watershed that could lead to increased contamination of the source water by Cryptosporidium, the system must take actions specified by the Division to address the contamination. These actions may include additional source water monitoring and/or implementing microbial toolbox options listed in subsection 20.16.

20.13 Unfiltered system Cryptosporidium treatment requirements

20.13.1 Determination of mean Cryptosporidium level.

20.13.1.1 Following completion of the initial source water monitoring required under subsection 20.2.1, unfiltered systems must calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under subsection 20.2.1. Systems must report this value to the Division for approval no later than 6 months after the month the system is required to complete initial source water monitoring based on the schedule in subsection 20.2.3.

20.13.1.2 Following completion of the second round of source water monitoring required under subsection 20.2.2, unfiltered systems must calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under subsection 20.2.2. Systems must report this value to the Division for approval no later than 6 months after the month the system is required to complete the second round of source water monitoring based on the schedule in subsection 20.1.3.

20.13.1.3 If the monthly Cryptosporidium sampling frequency varies, systems must first calculate a monthly average for each month of monitoring. Systems must then use these monthly average concentrations, rather than individual sample concentrations, in the calculation of the mean Cryptosporidium level in subsections 20.13.1.1 or 20.13.1.2.

20.13.1.4 The report to the Division of the mean Cryptosporidium levels calculated under subsections 20.13.1.1 and 20.13.1.2 must include a summary of the source water monitoring data used for the calculation.

20.13.1.5 Failure to comply with the conditions of subsection 20.13.1 is a violation of the treatment technique requirement.

20.13.2Cryptosporidium inactivation requirements. Unfiltered systems must provide the level of inactivation for Cryptosporidium specified in this paragraph, based on their mean Cryptosporidium levels as determined under subsection 20.13.1 and according to the schedule in subsection 20.14.

20.13.2.1 Unfiltered systems with a mean Cryptosporidium level of 0.01 oocysts/L or less must provide at least 2-log Cryptosporidium inactivation.

20.13.2.2 Unfiltered systems with a mean Cryptosporidium level of greater than 0.01 oocysts/L must provide at least 3-log Cryptosporidium inactivation.

20.13.3 Inactivation treatment technology requirements. Unfiltered systems must use chlorine dioxide, ozone, or UV as described in subsection 20.21 to meet the Cryptosporidium inactivation requirements of this section.

20.13.3.1 Systems that use chlorine dioxide or ozone and fail to achieve the Cryptosporidium inactivation required in subsection 20.13.2 on more than one day in the calendar month are in violation of the treatment technique requirement.

20.13.3.2 Systems that use UV light and fail to achieve the Cryptosporidium inactivation required in subsection 20.13.2 by meeting the criteria in subsection 20.21.4.2 are in violation of the treatment technique requirement.

20.13.4 Use of two disinfectants. Unfiltered systems must meet the combined Cryptosporidium inactivation requirements of this section and Giardia lamblia and virus inactivation requirements of section 16.3 using a minimum of two disinfectants, and each of two disinfectants must separately achieve the total inactivation required for either Cryptosporidium, Giardia lamblia, or viruses. Note: these regulations prohibit unfiltered surface water systems.

20.14 Schedule for compliance with Cryptosporidium treatment requirements

20.14.1 Following initial bin classification under subsection 20.11.3, filtered systems must provide the level of treatment for Cryptosporidium required under subsection 20.12 according to the schedule in subsection 20.14.3.

20.14.2 Following initial determination of the mean Cryptosporidium level under subsection 20.13.1.1, unfiltered systems must provide the level of treatment for Cryptosporidium required under subsection 20.13 according to the schedule in subsection 20.14.3.

20.14.3Cryptosporidium treatment compliance dates.

Cryptosporidium Treatment Compliance Dates Table

Systems that serve...	Must comply with Cryptosporidium treatment requirements no later than...¹
(1) at least 100,000 people	(i) April 1, 2012
(2) From 50,000 to 99,999 people	(i) October 1, 2012
(3) From 10,000 to 49,999 people	(i) October 1, 2013
(4) Fewer than 10,000 people	(i) October 1, 2014

¹ The Division may allow up to an additional two years for complying with the treatment requirement for systems making capital improvements.

20.14.4 If the bin classification for a filtered system changes following the second round of source water monitoring, as determined under subsection 20.11.4, the system must provide the level of treatment for Cryptosporidium required under subsection 20.12 on a schedule the Division approves.

20.14.5 If the mean Cryptosporidium level for an unfiltered system changes following the second round of monitoring, as determined under subsection 20.13.1.2, and if the system must provide a different level of Cryptosporidium treatment under subsection 20.13 due to this change, the system must meet this treatment requirement on a schedule the Division approves.

20.15 Requirements for uncovered finished water storage facilities

20.15.1 Systems using uncovered finished water storage facilities must comply with the conditions of this section.

20.15.2 Systems must notify the Division of the use of each uncovered finished water storage facility no later than April 1, 2008.

20.15.3 Systems must meet the conditions of subsections 20.15.3.1 or 20.15.3.2 for each uncovered finished water storage facility or be in compliance with a Division-approved schedule to meet these conditions no later than April 1, 2009.

20.15.3.1 Systems must cover any uncovered finished water storage facility.

20.15.3.2 Systems must treat the discharge from the uncovered finished water storage facility to the distribution system to achieve inactivation and/or removal of at least 4-log virus, 3-log Giardia lamblia, and 2-log Cryptosporidium using a protocol approved by the Division.

20.15.4 Failure to comply with the requirements of this section is a violation of the treatment technique requirement.

20.16 Microbial toolbox options for meeting Cryptosporidium treatment requirements.

20.16.1 Treatment credits

20.16.1.1 Systems receive the treatment credits listed in the table in subsection 20.16.2 by meeting the conditions for microbial toolbox options described in subsections 20.17 through 20.21. Systems apply these treatment credits to meet the treatment requirements in subsections 20.12 or 20.13, as applicable.

20.16.1.2 Unfiltered systems are eligible for treatment credits for the microbial toolbox options described in subsection 20.21 only.

20.16.2 The following table summarizes options, treatment credits, and criteria in the microbial toolbox:

Microbial Toolbox Summary Table: Options, Treatment Credits and Criteria

Toolbox Option	Cryptosporidium Treatment credit with design and implementation criteria
Source Protection and Management Toolbox Options
(1) Watershed control program	0.5-log credit for Division-approved program comprising required elements, annual program status report to Division, and regular watershed survey. Unfiltered systems are not eligible for credit. Specific criteria are in subsection 20.17.1.
(2) Alternative source/intake management	No prescribed credit. Systems may conduct simultaneous monitoring for treatment bin classification at alternative intake locations or under alternative intake management strategies. Specific criteria are in subsection 20.17.2.
Pre-Filtration Toolbox Options
(3) Presedimentation basin with coagulation	0.5-log credit during any month that presedimentation basins achieve a monthly mean reduction of 0.5-log or greater in turbidity or alternative Division-approved performance criteria. To be eligible, basins must be operated continuously with coagulant addition and all plant flow must pass through the basins. Specific criteria are in subsection 20.18.1.
(4) Two-stage lime softening	0.5-log credit for two-stage softening where chemical addition and hardness precipitation occur in both stages. All plant flow must pass through both stages. Single-stage softening is credited as equivalent to conventional treatment. Specific criteria are in subsection 20.18.2.
(5) Bank filtration	0.5-log credit for 25-foot setback; 1.0-log credit for 50-foot setback; aquifer must be unconsolidated sand containing at least 10 percent fines; average turbidity in wells must be less than 1 NTU. Systems using wells followed by filtration when conducting source water monitoring must sample the well to determine bin classification and are not eligible for additional credit. Specific criteria are in subsection 20.18.3.
Treatment Performance Toolbox Options
(6) Combined filter performance	0.5-log credit for combined filter effluent turbidity less than or equal to 0.15 NTU in at least 95 percent of measurements each month. Specific criteria are in subsection 20.19.1.
(7) Individual filter performance	0.5-log credit (in addition to 0.5-log combined filter performance credit) if individual filter effluent turbidity is less than or equal to 0.15 NTU in at least 95 percent of samples each month in each filter and is never greater than 0.3 NTU in two consecutive measurements in any filter. Specific criteria are in subsection 20.19.2.
(8) Demonstration of performance	Credit awarded to unit process or treatment train based on a demonstration to the Division with a Division-approved protocol. Specific criteria are in subsection 20.19.3.
Additional Filtration Toolbox Options
(9) Bag or cartridge filters (individual filters)	Up to 2-log credit based on the removal efficiency demonstrated during challenge testing with a 1-log factor of safety. Specific criteria are in subsection 20.20.1.
(10) Bag or cartridge filter (in series)	Up to 2.5-log credit based on the removal efficiency demonstrated during challenge testing with a 0.5-log factor of safety. Specific criteria are in subsection 20.20.1.
(11) Membrane filtration	Log credit equivalent to removal efficiency demonstrated in challenge test for device if supported by direct integrity testing. Specific criteria are in subsection 20.20.2.
(12) Second stage filtration	0.5-log credit for second separate granular media filtration stage if treatment train includes coagulation prior to first filter. Specific criteria are in subsection 20.20.3.
(13) Slow sand filters	2.5-log credit as a secondary filtration step; 3.0-log credit as a primary filtration process. No prior chlorination for either option. Specific criteria are in subsection 20.20.4.
Inactivation Toolbox Options
(14) Chlorine dioxide	Log credit based on measured CT in relation to CT table. Specific criteria are in subsection 20.21.2.
(15) Ozone	Log credit based on measured CT in relation to CT table. Specific criteria are in subsection 20.21.2.
(16) UV	Log credit based on validated UV dose in relation to UV dose table; reactor validation testing required to establish UV dose and associated operating conditions. Specific criteria are in subsection 20.21.4.

20.17 Source toolbox components

20.17.1 Watershed control program. Systems receive 0.5-log Cryptosporidium treatment credit for implementing a watershed control program that meets the requirements of this section.

20.17.1.1 Systems that intend to apply for the watershed control program credit must notify the Division of this intent no later than two years prior to the treatment compliance date applicable to the system in subsection 20.14.

20.17.1.2 Systems must submit to the Division a proposed watershed control plan no later than one year before the applicable treatment compliance date in subsection 20.14. The Division must approve the watershed control plan for the system to receive watershed control program treatment credit. The watershed control plan must include the elements in subsections 20.17.1.2.1 through 20.17.1.2.4.

20.17.1.2.1 Identification of an "area of influence" outside of which the likelihood of Cryptosporidium or fecal contamination affecting the treatment plant intake is not significant. This is the area to be evaluated in future watershed surveys under subsection 20.17.1.5.2.

20.17.1.2.2 Identification of both potential and actual sources of Cryptosporidium contamination and an assessment of the relative impact of these sources on the system's source water quality.

20.17.1.2.3 An analysis of the effectiveness and feasibility of control measures that could reduce Cryptosporidium loading from sources of contamination to the system's source water.

20.17.1.2.4 A statement of goals and specific actions the system will undertake to reduce source water Cryptosporidium levels. The plan must explain how the actions are expected to contribute to specific goals, identify watershed partners and their roles, identify resource requirements and commitments, and include a schedule for plan implementation with deadlines for completing specific actions identified in the plan.

20.17.1.3 Systems with existing watershed control programs (i.e., programs in place on January 5, 2006) are eligible to seek this credit. Their watershed control plans must meet the criteria in subsection 20.17.1.2 and must specify ongoing and future actions that will reduce source water Cryptosporidium levels.

20.17.1.4 If the Division does not respond to a system regarding approval of a watershed control plan submitted under this section and the system meets the other requirements of this section, the watershed control program will be considered approved and 0.5 log Cryptosporidium treatment credit will be awarded unless and until the Division subsequently withdraws such approval.

20.17.1.5 Systems must complete the actions in subsections 20.17.1.5.1 through 20.17.1.5.3 to maintain the 0.5-log credit.

20.17.1.5.1 Submit an annual watershed control program status report to the Division. The annual watershed control program status report must describe the system's implementation of the approved plan and assess the adequacy of the plan to meet its goals. It must explain how the system is addressing any shortcomings in plan implementation, including those previously identified by the Division or as the result of the watershed survey conducted under subsection 20.17.1.5.2. It must also describe any significant changes that have occurred in the watershed since the last watershed sanitary survey. If a system determines during implementation that making a significant change to its approved watershed control program is necessary, the system must notify the Division prior to making any such changes. If any change is likely to reduce the level of source water protection, the system must also list in its notification the actions the system will take to mitigate this effect.

20.17.1.5.2 Undergo a watershed sanitary survey every three years for community water systems and every five years for non-community water systems and submit the survey report to the Division. The survey must be conducted according to Division guidelines and by persons the Division approves.

20.17.1.5.2.1 The watershed sanitary survey must meet the following criteria: encompass the region identified in the Division-approved watershed control plan as the area of influence; assess the implementation of actions to reduce source water Cryptosporidium levels; and identify any significant new sources of Cryptosporidium.

20.17.1.5.2.2 If the Division determines that significant changes may have occurred in the watershed since the previous watershed sanitary survey, systems must undergo another watershed sanitary survey by a date the Division requires, which may be earlier than the regular date in subsection 20.17.1.5.2.

20.17.1.5.3 The system must make the watershed control plan, annual status reports, and watershed sanitary survey reports available to the public upon request. These documents must be in a plain language style and include criteria by which to evaluate the success of the program in achieving plan goals. The Division may approve systems to withhold from the public portions of the annual status report, watershed control plan, and watershed sanitary survey based on water supply security considerations.

20.17.1.6 If the Division determines that a system is not carrying out the approved watershed control plan, the Division may withdraw the watershed control program treatment credit.

20.17.2 Alternative source.

20.17.2.1 A system may conduct source water monitoring that reflects a different intake location (either in the same source or for an alternate source) or a different procedure for the timing or level of withdrawal from the source (alternative source monitoring). If the Division approves, a system may determine its bin classification under subsection 20.11 based on the alternative source monitoring results.

20.17.2.2 If systems conduct alternative source monitoring under subsection 20.17.2.1, systems must also monitor their current plant intake concurrently as described in subsection 20.2.

20.17.2.3 Alternative source monitoring under subsection 20.17.2.1 must meet the requirements for source monitoring to determine bin classification, as described in subsections 20.2 through 20.7. Systems must report the alternative source monitoring results to the Division, along with supporting information documenting the operating conditions under which the samples were collected.

20.17.2.4 If a system determines its bin classification under subsection 20.11 using alternative source monitoring results that reflect a different intake location or a different procedure for managing the timing or level of withdrawal from the source, the system must relocate the intake or permanently adopt the withdrawal procedure, as applicable, no later than the applicable treatment compliance date in subsection 20.14.

20.18 Pre-filtration treatment toolbox components

20.18.1 Presedimentation. Systems receive 0.5-log Cryptosporidium treatment credit for a presedimentation basin during any month the process meets the criteria in this paragraph.

20.18.1.1 The presedimentation basin must be in continuous operation and must treat the entire plant flow taken from a surface water or GWUDI source.

20.18.1.2 The system must continuously add a coagulant to the presedimentation basin.

20.18.1.3 The presedimentation basin must achieve the performance criteria in subsections 20.18.1.3.1 or 20.18.1.3.2.

20.18.1.3.1 Demonstrates at least 0.5-log mean reduction of influent turbidity. This reduction must be determined using daily turbidity measurements in the presedimentation process influent and effluent and must be calculated as follows: log10 (monthly mean of daily influent turbidity)-log10 (monthly mean of daily effluent turbidity).

20.18.1.3.2 Complies with Division-approved performance criteria that demonstrate at least 0.5-log mean removal of micron-sized particulate material through the presedimentation process.

20.18.2 Two-stage lime softening. Systems receive an additional 0.5-log Cryptosporidium treatment credit for a two-stage lime softening plant if chemical addition and hardness precipitation occur in two separate and sequential softening stages prior to filtration. Both softening stages must treat the entire plant flow taken from a surface water or GWUDI source.

20.18.3 Bank filtration. Systems receive Cryptosporidium treatment credit for bank filtration that serves as pretreatment to a filtration plant by meeting the criteria in this paragraph. Systems using bank filtration when they begin source water monitoring under subsection 20.2.1 must collect samples as described in subsection 20.4.4 and are not eligible for this credit.

20.18.3.1 Wells with a ground water flow path of at least 25 feet receive 0.5-log treatment credit; wells with a ground water flow path of at least 50 feet receive 1.0-log treatment credit. The ground water flow path must be determined as specified in subsection 20.18.3.4.

20.18.3.2 Only wells in granular aquifers are eligible for treatment credit. Granular aquifers are those comprised of sand, clay, silt, rock fragments, pebbles or larger particles, and minor cement. A system must characterize the aquifer at the well site to determine aquifer properties. Systems must extract a core from the aquifer and demonstrate that in at least 90 percent of the core length, grains less than 1.0 mm in diameter constitute at least 10 percent of the core material.

20.18.3.3 Only horizontal and vertical wells are eligible for treatment credit.

20.18.3.4 For vertical wells, the ground water flow path is the measured distance from the edge of the surface water body under high flow conditions (determined by the 100 year floodplain elevation boundary or by the floodway, as defined in Federal Emergency Management Agency flood hazard maps) to the well screen. For horizontal wells, the ground water flow path is the measured distance from the bed of the river under normal flow conditions to the closest horizontal well lateral screen.

20.18.3.5 Systems must monitor each wellhead for turbidity at least once every four hours while the bank filtration process is in operation. If monthly average turbidity levels, based on daily maximum values in the well, exceed 1 NTU, the system must report this result to the Division and conduct an assessment within 30 days to determine the cause of the high turbidity levels in the well. If the Division determines that microbial removal has been compromised, the Division may revoke treatment credit until the system implements corrective actions approved by the Division to remediate the problem.

20.18.3.6 Springs and infiltration galleries are not eligible for treatment credit under this subsection, but are eligible for credit under subsection 20.19.3.

20.18.3.7 Bank filtration demonstration of performance. The Division may approve Cryptosporidium treatment credit for bank filtration based on a demonstration of performance study that meets the criteria in this paragraph. This treatment credit may be greater than 1.0-log and may be awarded to bank filtration that does not meet the criteria in subsections 20.18.3.1 through 20.18.3.5.

20.18.3.7.1 The study must follow a Division-approved protocol and must involve the collection of data on the removal of Cryptosporidium or a surrogate for Cryptosporidium and related hydrogeologic and water quality parameters during the full range of operating conditions.

20.18.3.7.2 The study must include sampling both from the production well(s) and from monitoring wells that are screened and located along the shortest flow path between the surface water source and the production well(s).

20.19 Treatment performance toolbox components

20.19.1 Combined filter performance. Systems using conventional filtration treatment or direct filtration treatment receive an additional 0.5-log Cryptosporidium treatment credit during any month the system meets the criteria in this paragraph. Combined filter effluent (CFE) turbidity must be less than or equal to 0.15 NTU in at least 95 percent of the measurements. Turbidity must be measured as described in subsections 16.5.1.

20.19.2 Individual filter performance. Systems using conventional filtration treatment or direct filtration treatment receive 0.5-log Cryptosporidium treatment credit, which can be in addition to the 0.5-log credit under subsection 20.19.1, during any month the system meets the criteria in this paragraph. Compliance with these criteria must be based on individual filter turbidity monitoring as described in subsection 10.10 or 40 CFR section 141.560 (Copy available at the Office of Drinking Water as applicable).

20.19.2.1 The filtered water turbidity for each individual filter must be less than or equal to 0.15 NTU in at least 95 percent of the measurements recorded each month.

20.19.2.2 No individual filter may have a measured turbidity greater than 0.3 NTU in two consecutive measurements taken 15 minutes apart.

20.19.2.3 Any system that has received treatment credit for individual filter performance and fails to meet the requirements of subsections 20.19.2.1 or 20.19.2.2 during any month does not receive a treatment technique violation under subsection 20.12.3 if the Division determines the following:

20.19.2.3.1 The failure was due to unusual and short-term circumstances that could not reasonably be prevented through optimizing treatment plant design, operation, and maintenance.

20.19.2.3.2 The system has experienced no more than two such failures in any calendar year.

20.19.3 Demonstration of performance. The Division may approve Cryptosporidium treatment credit for drinking water treatment processes based on a demonstration of performance study that meets the criteria in this paragraph. This treatment credit may be greater than or less than the prescribed treatment credits in subsection 20.12 or subsections 20.18 through 20.21 and may be awarded to treatment processes that do not meet the criteria for the prescribed credits.

20.19.3.1 Systems cannot receive the prescribed treatment credit for any toolbox box option in subsections 20.18 through 20.21 if that toolbox option is included in a demonstration of performance study for which treatment credit is awarded under this paragraph.

20.19.3.2 The demonstration of performance study must follow a Division-approved protocol and must demonstrate the level of Cryptosporidium reduction the treatment process will achieve under the full range of expected operating conditions for the system.

20.19.3.3 Approval by the Division must be in writing and may include monitoring and treatment performance criteria that the system must demonstrate and report on an ongoing basis to remain eligible for the treatment credit. The Division may designate such criteria where necessary to verify that the conditions under which the demonstration of performance credit was approved are maintained during routine operation.

20.20 Additional filtration toolbox components

20.20.1 Bag and cartridge filters. Systems receive Cryptosporidium treatment credit of up to 2.0-log for individual bag or cartridge filters and up to 2.5-log for bag or cartridge filters operated in series by meeting the criteria in subsections 20.20.1.1 through 20.20.1.10. To be eligible for this credit, systems must report the results of challenge testing that meets the requirements of subsections 20.20.1.2 through 20.20.1.9 to the Division. The filters must treat the entire plant flow taken from a surface water or ground water under the direct influence of surface water source.

20.20.1.1 The Cryptosporidium treatment credit awarded to bag or cartridge filters must be based on the removal efficiency demonstrated during challenge testing that is conducted according to the criteria in subsections 20.20.1.2 through 20.20.1.9. A factor of safety equal to 1-log for individual bag or cartridge filters and 0.5-log for bag or cartridge filters in series must be applied to challenge testing results to determine removal credit. Systems may use results from challenge testing conducted prior to January 5, 2006 if the prior testing was consistent with the criteria specified in subsections 20.20.1.2 through 20.20.1.9.

20.20.1.2 Challenge testing must be performed on full-scale bag or cartridge filters, and the associated filter housing or pressure vessel, that are identical in material and construction to the filters and housings the system will use for removal of Cryptosporidium. Bag or cartridge filters must be challenge tested in the same configuration that the system will use, either as individual filters or as a series configuration of filters.

20.20.1.3 Challenge testing must be conducted using Cryptosporidium or a surrogate that is removed no more efficiently than Cryptosporidium. The microorganism or surrogate used during challenge testing is referred to as the challenge particulate. The concentration of the challenge particulate must be determined using a method capable of discreetly quantifying the specific microorganism or surrogate used in the test; gross measurements such as turbidity may not be used.

20.20.1.4 The maximum feed water concentration that can be used during a challenge test must be based on the detection limit of the challenge particulate in the filtrate (i.e., filtrate detection limit) and must be calculated using the following equation:

Maximum Feed Concentration = 1 x 104 x (Filtrate Detection Limit)

20.20.1.5 Challenge testing must be conducted at the maximum design flow rate for the filter as specified by the manufacturer.

20.20.1.6 Each filter evaluated must be tested for a duration sufficient to reach 100 percent of the terminal pressure drop, which establishes the maximum pressure drop under which the filter may be used to comply with the requirements of this section.

20.20.1.7 Removal efficiency of a filter must be determined from the results of the challenge test and expressed in terms of log removal values using the following equation:

LRV = LOG10 (Cf)-LOG10 (Cp)

Where:

LRV = log removal value demonstrated during challenge testing;

Cf = the feed concentration measured during the challenge test; and

Cp = the filtrate concentration measured during the challenge test.

20.20.1.7.1 In applying this equation, the same units must be used for the feed and filtrate concentrations. If the challenge particulate is not detected in the filtrate, then the term Cp must be set equal to the detection limit.

20.20.1.8 Each filter tested must be challenged with the challenge particulate during three periods over the filtration cycle: within two hours of start-up of a new filter; when the pressure drop is between 45 and 55 percent of the terminal pressure drop; and at the end of the cycle after the pressure drop has reached 100 percent of the terminal pressure drop. An LRV must be calculated for each of these challenge periods for each filter tested. The LRV for the filter (LRVfilter) must be assigned the value of the minimum LRV observed during the three challenge periods for that filter.

20.20.1.9 If fewer than 20 filters are tested, the overall removal efficiency for the filter product line must be set equal to the lowest LRVfilter among the filters tested. If 20 or more filters are tested, the overall removal efficiency for the filter product line must be set equal to the 10th percentile of the set of LRVfilter values for the various filters tested. The percentile is defined by (i/(n+1)) where i is the rank of an individual data points ordered lowest to highest. If necessary, the 10th percentile may be calculated using linear interpolation.

20.20.1.10 If a previously tested filter is modified in a manner that could change the removal efficiency of the filter product line, challenge testing to demonstrate the removal efficiency of the modified filter must be conducted and submitted to the Division.

20.20.2 Membrane filtration.

20.20.2.1 Systems receive Cryptosporidium treatment credit for membrane filtration that meets the criteria of this paragraph. Membrane cartridge filters that meet the definition of membrane filtration in Section 2.0 are eligible for this credit. The level of treatment credit a system receives is equal to the lower of the values determined under subsections 20.20.2.1.1 and 20.20.2.1.2.

20.20.2.1.1 The removal efficiency demonstrated during challenge testing conducted under the conditions in subsection 20.20.2.2.

20.20.2.1.2 The maximum removal efficiency that can be verified through direct integrity testing used with the membrane filtration process under the conditions in subsection 20.20.2.3.

20.20.2.2 Challenge Testing. The membrane used by the system must undergo challenge testing to evaluate removal efficiency, and the system must report the results of challenge testing to the Division. Challenge testing must be conducted according to the criteria in subsections 20.20.2.2.1 through 20.20.2.2.7. Systems may use data from challenge testing conducted prior to January 5, 2006 if the prior testing was consistent with the criteria in subsections 20.20.2.2.1 through 20.20.2.2.7.

20.20.2.2.1 Challenge testing must be conducted on either a full-scale membrane module, identical in material and construction to the membrane modules used in the system's treatment facility, or a smaller-scale membrane module, identical in material and similar in construction to the full-scale module. A module is defined as the smallest component of a membrane unit in which a specific membrane surface area is housed in a device with a filtrate outlet structure.

20.20.2.2.2 Challenge testing must be conducted using Cryptosporidium oocysts or a surrogate that is removed no more efficiently than Cryptosporidium oocysts. The organism or surrogate used during challenge testing is referred to as the challenge particulate. The concentration of the challenge particulate, in both the feed and filtrate water, must be determined using a method capable of discretely quantifying the specific challenge particulate used in the test; gross measurements such as turbidity may not be used.

20.20.2.2.3 The maximum feed water concentration that can be used during a challenge test is based on the detection limit of the challenge particulate in the filtrate and must be determined according to the following equation:

Maximum Feed Concentration = 3.16 x 106 x (Filtrate Detection Limit)

20.20.2.2.4 Challenge testing must be conducted under representative hydraulic conditions at the maximum design flux and maximum design process recovery specified by the manufacturer for the membrane module. Flux is defined as the throughput of a pressure driven membrane process expressed as flow per unit of membrane area. Recovery is defined as the volumetric percent of feed water that is converted to filtrate over the course of an operating cycle uninterrupted by events such as chemical cleaning or a solids removal process (i.e., backwashing).

20.20.2.2.5 Removal efficiency of a membrane module must be calculated from the challenge test results and expressed as a log removal value according to the following equation:

LRV = LOG10(Cf) - LOG10(Cp)

Where:

LRV = log removal value demonstrated during the challenge test;

Cf = the feed concentration measured during the challenge test; and

Cp = the filtrate concentration measured during the challenge test.

Equivalent units must be used for the feed and filtrate concentrations. If the challenge particulate is not detected in the filtrate, the term Cp is set equal to the detection limit for the purpose of calculating the LRV. An LRV must be calculated for each membrane module evaluated during the challenge test.

20.20.2.2.6 The removal efficiency of a membrane filtration process demonstrated during challenge testing must be expressed as a log removal value (LRVC-Test). If fewer than 20 modules are tested, then LRVC-Test is equal to the lowest of the representative LRVs among the modules tested. If 20 or more modules are tested, then LRVC-Test is equal to the 10th percentile of the representative LRVs among the modules tested. The percentile is defined by (i/(n+1)) where i is the rank of n individual data points ordered lowest to highest. If necessary, the 10th percentile may be calculated using linear interpolation.

20.20.2.2.7 The challenge test must establish a quality control release value (QCRV) for a non-destructive performance test that demonstrates the Cryptosporidium removal capability of the membrane filtration module. This performance test must be applied to each production membrane module used by the system that was not directly challenge tested in order to verify Cryptosporidium removal capability. Production modules that do not meet the established QCRV are not eligible for the treatment credit demonstrated during the challenge test.

20.20.2.2.8 If a previously tested membrane is modified in a manner that could change the removal efficiency of the membrane or the applicability of the non-destructive performance test and associated QCRV, additional challenge testing to demonstrate the removal efficiency of, and determine a new QCRV for, the modified membrane must be conducted and submitted to the Division.

20.20.2.3 Direct integrity testing. Systems must conduct direct integrity testing in a manner that demonstrates a removal efficiency equal to or greater than the removal credit awarded to the membrane filtration process and meets the requirements described in subsections 20.20.2.3.1 through 20.20.2.3.6. A direct integrity test is defined as a physical test applied to a membrane unit in order to identify and isolate integrity breaches (i.e., one or more leaks that could result in contamination of the filtrate).

20.20.2.3.1 The direct integrity test must be independently applied to each membrane unit in service. A membrane unit is defined as a group of membrane modules that share common valving that allows the unit to be isolated from the rest of the system for the purpose of integrity testing or other maintenance.

20.20.2.3.2 The direct integrity method must have a resolution of 3 micrometers or less, where resolution is defined as the size of the smallest integrity breach that contributes to a response from the direct integrity test.

20.20.2.3.3 The direct integrity test must have a sensitivity sufficient to verify the log treatment credit awarded to the membrane filtration process by the Division, where sensitivity is defined as the maximum log removal value that can be reliably verified by a direct integrity test. Sensitivity must be determined using the approach in either subsection 20.20.2.3.3.1 or 20.20.2.3.3.2 as applicable to the type of direct integrity test the system uses.

20.20.2.3.3.1 For direct integrity tests that use an applied pressure or vacuum, the direct integrity test sensitivity must be calculated according to the following equation:

LRVDIT = LOG10 (Qp/(VCF x Qbreach))

Where:

LRVDIT = the sensitivity of the direct integrity test;

Qp = total design filtrate flow from the membrane unit;

Qbreach = flow of water from an integrity breach associated with the smallest integrity test response that can be reliably measured, and

VCF = volumetric concentration factor. The volumetric concentration factor is the ratio of the suspended solids concentration on the high pressure side of the membrane relative to that in the feed water.

20.20.2.3.3.2 For direct integrity tests that use a particulate or molecular marker, the direct integrity test sensitivity must be calculated according to the following equation:

LRVDIT = LOG10 (Cf)- LOG10(Cp)

Where:

LRVDIT = the sensitivity of the direct integrity test;

Cf = the typical feed concentration of the marker used in the test; and Cp = the filtrate concentration of the marker from an integral membrane unit.

20.20.2.3.4 Systems must establish a control limit within the sensitivity limits of the direct integrity test that is indicative of an integral membrane unit capable of meeting the removal credit awarded by the Division.

20.20.2.3.5 If the result of a direct integrity test exceeds the control limit established under subsection 20.20.2.3.4, the system must remove the membrane unit from service. Systems must conduct a direct integrity test to verify any repairs, and may return the membrane unit to service only if the direct integrity test is within the established control limit.

20.20.2.3.6 Systems must conduct direct integrity testing on each membrane unit at a frequency of not less than once each day that the membrane unit is in operation. The Division may approve less frequent testing, based on demonstrated process reliability, the use of multiple barriers effective for Cryptosporidium, or reliable process safeguards.

20.20.2.4 Indirect integrity monitoring. Systems must conduct continuous indirect integrity monitoring on each membrane unit according to the criteria in subsections 20.20.2.4.1 through 20.20.2.4.5. Indirect integrity monitoring is defined as monitoring some aspect of filtrate water quality that is indicative of the removal of particulate matter. A system that implements continuous direct integrity testing of membrane units in accordance with the criteria in subsections 20.20.2.3.1 through 20.20.2.3.5 is not subject to the requirements for continuous indirect integrity monitoring. Systems must submit a monthly report to the Division summarizing all continuous indirect integrity monitoring results triggering direct integrity testing and the corrective action that was taken in each case.

20.20.2.4.1 Unless the Division approves an alternative parameter, continuous indirect integrity monitoring must include continuous filtrate turbidity monitoring.

20.20.2.4.2 Continuous monitoring must be conducted at a frequency of no less than once every 15 minutes.

20.20.2.4.3 Continuous monitoring must be separately conducted on each membrane unit.

20.20.2.4.4 If indirect integrity monitoring includes turbidity and if the filtrate turbidity readings are above 0.15 NTU for a period greater than 15 minutes (i.e., two consecutive 15-minute readings above 0.15 NTU), direct integrity testing must immediately be performed on the associated membrane unit as specified in subsections 20.20.2.3.1 through 20.20.2.3.5.

20.20.2.4.5 If indirect integrity monitoring includes a Division-approved alternative parameter and if the alternative parameter exceeds a Division-approved control limit for a period greater than 15 minutes, direct integrity testing must immediately be performed on the associated membrane units as specified in subsections 20.20.2.3.1 through 20.20.2.3.5.

20.20.3 Second stage filtration. Systems receive 0.5-log Cryptosporidium treatment credit for a separate second stage of filtration that consists of sand, dual media, GAC, or other fine grain media following granular media filtration if the Division approves. To be eligible for this credit, the first stage of filtration must be preceded by a coagulation step and both filtration stages must treat the entire plant flow taken from a surface water or GWUDI source. A cap, such as GAC, on a single stage of filtration is not eligible for this credit. The Division must approve the treatment credit based on an assessment of the design characteristics of the filtration process.

20.20.4 Slow sand filtration (as secondary filter). Systems are eligible to receive 2.5-log Cryptosporidium treatment credit for a slow sand filtration process that follows a separate stage of filtration if both filtration stages treat entire plant flow taken from a surface water or GWUDI source and no disinfectant residual is present in the influent water to the slow sand filtration process. The Division must approve the treatment credit based on an assessment of the design characteristics of the filtration process. This paragraph does not apply to treatment credit awarded to slow sand filtration used as a primary filtration process.

20.21 Inactivation toolbox components

20.21.1 Calculation of CT values.

20.21.1.1 CT is the product of the disinfectant contact time (T, in minutes) and disinfectant concentration (C, in milligrams per liter). Systems with treatment credit for chlorine dioxide or ozone under subsection 20.21.2 or 20.21.3 must calculate CT at least once each day, with both C and T measured during peak hourly flow as specified in subsection 10.6.

20.21.1.2 Systems with several disinfection segments in sequence may calculate CT for each segment, where a disinfection segment is defined as a treatment unit process with a measurable disinfectant residual level and a liquid volume. Under this approach, systems must add the Cryptosporidium CT values in each segment to determine the total CT for the treatment plant.

20.21.2 CT values for chlorine dioxide and ozone.

20.21.2.1 Systems receive the Cryptosporidium treatment credit listed in this table by meeting the corresponding chlorine dioxide CT value for the applicable water temperature, as described in subsection 20.21.1.

CT Values (mg-min/L) for Cryptosporidium Inactivation by Chlorine Dioxide ¹

Log credit	Water Temperature, oC
Log credit	[LESS THEN OR EQUAL TO]0.5	1	2	3	5	7	10	15	20	25	30
(i) 0.25	159	153	140	128	107	90	69	45	29	19	12
(ii) 0.5	319	305	279	256	214	180	138	89	58	38	24
(iii) 1.0	637	610	558	511	429	360	277	179	116	75	49
(iv) 1.5	956	915	838	767	643	539	415	268	174	113	73
(v) 2.0	1275	1220	1117	1023	858	719	553	357	232	150	98
(vi) 2.5	1594	1525	1396	1278	1072	899	691	447	289	188	122
(vii) 3.0	1912	1830	1675	1534	1286	1079	830	536	347	226	147

¹ Systems may use this equation to determine log credit between the indicated values: Log credit = (0.001506 x (1.09116) Temp)x CT.

20.21.2.2 Systems receive the Cryptosporidium treatment credit listed in this table by meeting the corresponding ozone CT values for the applicable water temperature, as described in subsection 20.21.1.

CT Values (mg-min/L) for Cryptosporidium Inactivation by Ozone¹

Log credit	Water Temperature, oC
Log credit	[LESS THEN OR EQUAL TO]0.5	1	2	3	5	7	10	15	20	25	30
(i) 0.25	6.0	5.8	5.2	4.8	4.0	3.3	2.5	1.6	1.0	0.6	0.39
(ii) 0.5	12	12	10	9.5	7.9	6.5	4.9	3.1	2.0	1.2	0.78
(iii) 1.0	24	23	21	19	16	13	9.9	6.2	3.9	2.5	1.6
(iv) 1.5	36	35	31	29	24	20	15	9.3	5.9	3.7	2.4
(v) 2.0	48	46	42	38	32	26	20	12	7.8	4.9	3.1
(vi) 2.5	60	58	52	48	40	33	25	16	9.8	6.2	3.9
(vii) 3.0	72	69	63	57	47	39	30	19	12	7.4	4.7

¹ Systems may use this equation to determine log credit between the indicated values: Log credit = (0.0397 x (1.09757)Temp) x CT.

20.21.3 Site-specific study. The Division may approve alternative chlorine dioxide or ozone CT values to those listed in subsection 20.21.2 on a site-specific basis. The Division must base this approval on a site-specific study a system conducts that follows a Division-approved protocol.

20.21.4 Ultraviolet light. Systems receive Cryptosporidium, Giardia lamblia, and virus treatment credits for ultraviolet (UV) light reactors by achieving the corresponding UV dose values shown in subsection 20.21.4.1. Systems must validate and monitor UV reactors as described in subsections 20.21.4.2 and 20.21.4.3 to demonstrate that they are achieving a particular UV dose value for treatment credit.

20.21.4.1 UV dose table. The treatment credits listed in this table are for UV light at a wavelength of 254 nm as produced by a low pressure mercury vapor lamp. To receive treatment credit for other lamp types, systems must demonstrate an equivalent germicidal dose through reactor validation testing, as described in subsection 20.21.4.2. The UV dose values in this table are applicable only to post-filter applications of UV in filtered systems and to unfiltered systems.

UV Dose Table for Cryptosporidium, Giardia lamblia, and Virus Inactivation Credit

Log credit	Cryptosporidium UV dose (mJ/cm2)	Giardia lamblia UV dose (mJ/cm2)	Virus UV dose (mJ/cm2)
(i) 0.5	1.6	1.5	39
(ii) 1.0	2.5	2.1	58
(iii) 1.5	3.9	3.0	79
(iv) 2.0	5.8	5.2	100
(v) 2.5	8.5	7.7	121
(vi) 3.0	12	11	143
(vii) 3.5	15	15	163
(viii) 4.0	22	22	186

20.21.4.2 Reactor validation testing. Systems must use UV reactors that have undergone validation testing to determine the operating conditions under which the reactor delivers the UV dose required in subsection 20.21.4.1 (i.e., validated operating conditions). These operating conditions must include flow rate, UV intensity as measured by a UV sensor, and UV lamp status.

20.21.4.2.1 When determining validated operating conditions, systems must account for the following factors: UV absorbance of the water; lamp fouling and aging; measurement uncertainty of on-line sensors; UV dose distributions arising from the velocity profiles through the reactor; failure of UV lamps or other critical system components; and inlet and outlet piping or channel configurations of the UV reactor.

20.21.4.2.2 Validation testing must include the following: Full scale testing of a reactor that conforms uniformly to the UV reactors used by the system and inactivation of a test microorganism whose dose response characteristics have been quantified with a low-pressure mercury vapor lamp.

20.21.4.2.3 The Division may approve an alternative approach to validation testing.

20.21.4.3 Reactor monitoring.

20.21.4.3.1 Systems must monitor their UV reactors to determine if the reactors are operating within validated conditions, as determined under subsection 20.21.4.2. This monitoring must include UV intensity as measured by a UV sensor, flow rate, lamp status, and other parameters the Division designates based on UV reactor operation. Systems must verify the calibration of UV sensors and must recalibrate sensors in accordance with a protocol the Division approves.

20.21.4.3.2 To receive treatment credit for UV light, systems must treat at least 95 percent of the water delivered to the public during each month by UV reactors operating within validated conditions for the required UV dose, as described in subsections 20.21.4.1 and 20.21.4.2 of this section. Systems must demonstrate compliance with this condition by the monitoring required under subsection 20.21.4.3.1.

20.22 Reporting requirements

20.22.1 Systems must report sampling schedules under subsection 20.3 and source water monitoring results under subsection 20.7 unless they notify the Division that they will not conduct source water monitoring due to meeting the criteria of subsection 20.2.4.

20.22.2 Systems must report the use of uncovered finished water storage facilities to the Division as described in subsection 20.15.

20.22.3 Filtered systems must report their Cryptosporidium bin classification as described in subsection 20.11.

20.22.4 Unfiltered systems must report their mean source water Cryptosporidium level as described in subsection 20.13.

20.22.5 Systems must report disinfection profiles and benchmarks to the Division as described in subsections 20.9 through 20.10 prior to making a significant change in disinfection practice.

20.22.6 Systems must report to the Division in accordance with the following table for any microbial toolbox options used to comply with treatment requirements under subsections 20.12 or 20.13.

20.22.6.1 Alternatively, the Division may approve a system to certify operation within required parameters for treatment credit rather than reporting monthly operational data for toolbox options.

Microbial Toolbox Reporting Requirements

Toolbox option	Systems must submit the following information	On the following schedule
(1) Watershed control program (WCP)	(1) Notice of intention to develop a new or continue an existing watershed control program.	No later than two years before the application treatment compliance date in subsection 20.14.
	(2) Watershed control plan	No later than one year before the application compliance date in subsection 20.14.
	(3) Annual watershed control program status report	Every 12 months, beginning one year after the applicable treatment compliance date in subsection 20.14.
	(4) Watershed sanitary survey report	For community water systems, every three years beginning three years after the applicable treatment compliance date in subsection 20.14. For non-community water systems, every five years beginning five years after the applicable treatment compliance date in subsection 20.14.
(2) Alternative source/intake management	Verification that system has relocated the intake or adopted the intake withdrawal procedure reflected in monitoring results.	No later than applicable treatment compliance date in subsection 20.14.
(3) Presedimentation	Monthly verification of the following: (1) Continuous basin operation; (2) Treatment of 100% of the flow; (3) Continuous addition of a coagulant; and, (4) At least 0.5-log mean reduction of influent turbidity or compliance with alternative Division-approved performance criteria.	Monthly reporting within 10 days following the month in which the monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(4) Two-stage lime softening	Monthly verification of the following: (1) Chemical addition and hardness precipitation occurred in two separate and sequential softening stages prior to filtration; and, (2) Both stages treated 100% of the plant flow.	Monthly reporting within 10 days following the month in which the monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(5) Bank filtration	(1) Initial demonstration of the following: (A) Unconsolidated, predominantly sandy aquifer; and (B) Setback distance of at least 25 ft. (0.5-log credit) or 50 ft. (1.0-log credit)	No later than the applicable compliance date in subsection 20.14.
(5) Bank filtration	(2) If monthly average of daily max turbidity is greater than 1 NTU then the system must report result and submit an assessment of the cause.	Report within 30 days following the month in which the monitoring was conducted, beginning on the applicable compliance date in subsection 20.14.
(6) Combined filter performance	Monthly verification of combined filter effluent (CFE) turbidity levels less than or equal to 0.15 NTU in at least 95 percent of the 4 hour CFE measurements taken each month.	Monthly reporting within 10 days following the month in which the monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(7) Individual filter performance	Monthly verification of the following: (1) Individual filter effluent (IFE) turbidity levels less than or equal to 0.15 NTU in at least 95 percent of the samples each month in each filter; and, (2) No individual filter greater than 0.3 NTU in two consecutive readings 15 minutes apart.	Monthly reporting within 10 days following the month in which the monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(8) Demonstration of performance	(1) Results from testing following a Division approved protocol.	No later than the applicable compliance date in subsection 20.14.
(8) Demonstration of performance	(2) As required by the Division, monthly verification of operation within conditions of Division approval for demonstration of performance credit.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(9) Bag filters and cartridge filters	(1) Demonstration that the following criteria are met: (A) Process meets the definition of bag or cartridge filter; and, (B) Removal efficiency established through challenge testing that meets criteria in this section.	No later than applicable treatment compliance date in subsection 20.14.
(9) Bag filters and cartridge filters	(2) Monthly verification that 100% of plant flow was filtered.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(10) Membrane filtration	(1) Results of verification testing demonstrating the following: (A) Removal efficiency established through challenge testing that meets criteria in this section: and, (B) Integrity test method and parameters, including resolution, sensitivity, test frequency, control limits, and associated baseline.	No later than the applicable treatment compliance date in subsection 20.14.
(10) Membrane filtration	(2) Monthly report summarizing the following: (A) All direct integrity tests above the control limit: and, (B) If applicable, any turbidity or alternative Division-approved indirect integrity monitoring results triggering direct integrity testing and the corrective action that was taken.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(11) Second stage filtration	Monthly verification that 100% of flow was filtered through both stages and that first stage was preceded by coagulation step.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(12) Slow sand filtration (as secondary filter)	Monthly verification that both a slow sand filter and a preceding separate stage of filtration treated 100% of flow from surface water or ground water under the direct influence of surface water sources.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(13) Chlorine dioxide	Summary of CT values for each day as described in subsection 20.21.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(14) Ozone	Summary of CT values for each day as described in subsection 20.21	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.
(15) UV	(1) Validation test results demonstrating operating conditions that achieve required UV dose.	No later than the applicable treatment compliance date in subsection 20.14.
(15) UV	(2) Monthly report summarizing the percentage of water entering the distribution system that was not treated by UV reactors operating within validated conditions for the required dose as specified in subsection 20.21.4.	Within 10 days following the month in which monitoring was conducted, beginning on the applicable treatment compliance date in subsection 20.14.

20.23 Recordkeeping requirements

20.23.1 Systems must keep results from the initial round of source water monitoring under subsection 20.2.1 and the second round of source water monitoring under subsection 20.2.2 until 3 years after bin classification under subsection 20.11 for filtered systems or determination of the mean Cryptosporidium level under subsection 20.11 for unfiltered systems for the particular round of monitoring.

20.23.2 Systems must keep any notification to the Division that they will not conduct source water monitoring due to meeting the criteria of subsection 20.2.4 for 3 years.

20.23.3 Systems must keep the results of treatment monitoring associated with microbial toolbox options under subsections 20.17 through 20.21 and with uncovered finished water reservoirs under subsection 20.15, as applicable, for 3 years.

20.24 Requirements to respond to significant deficiencies identified in sanitary surveys performed by the Division.

20.24.1 A sanitary survey is an onsite review of the water source (identifying sources of contamination by using results of source water assessments where available), facilities, equipment, operation, maintenance, and monitoring compliance of a PWS to evaluate the adequacy of the PWS, its sources and operations, and the distribution of safe drinking water.

20.24.2 For the purposes of this section, a significant deficiency includes a defect in design, operation, or maintenance, or a failure or malfunction of the sources, treatment, storage, or distribution system that the Division determines to be causing, or has the potential for causing the introduction of contamination into the water delivered to consumers.

20.24.3 For sanitary surveys performed by the Division, systems must respond in writing to significant deficiencies identified in sanitary survey reports no later than 45 days after receipt of the report, indicating how and on what schedule the system will address significant deficiencies noted in the survey.

20.24.4 Systems must correct significant deficiencies identified in sanitary survey reports according to the schedule approved by the Division, or if there is no approved schedule, according to the schedule reported under subsection 20.24.3 if such deficiencies are within the control of the system.

16 Del. Admin. Code § 4462-20.0

20 DE Reg. 555(1/1/2017)
20 DE Reg. 808(4/1/2017)
24 DE Reg. 794(2/1/2021)
25 DE Reg. 713( 1/1/2022) (Final)