16 Del. Admin. Code § 4462-7.0

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

Section 4462-7.0 - Microbiological Requirements

7.1 Sampling:

7.1.1 Sampling Sites:

7.1.1.1 Compliance with bacteriological requirements of these regulations shall be based on examinations of samples collected at sites which are representative of water throughout the distribution system according to a written sample siting plan. These plans are subject to Division review and revision.

7.1.2 CWS Sampling Frequency:

7.1.1.2 The supplier of water for a CWS shall sample for total coliform bacteria at least monthly in numbers proportional to the population served by the system in accordance with the following:

Population Served	Number of Samples Per Month
25-1,000	1
1,001-2,500	2
2,501-3,300	3
3,301-4,100	4
4,101-4,900	5
4,901-5,800	6
5,801-6,700	7
6,701-7,600	8
7,601-8,500	9
8,501-12,900	10
12,901-17,200	15
17,201-21,500	20
21,501-25,000	25
25,001-33,000	30
33,001-41,000	40
41,001-50,000	50
50,001-59,000	60
59,001-70,000	70
70,001-83,000	80
83,001-96,000	90
96,001-130,000	100
130,001-220,000	120

7.1.3 Reduced Monitoring Frequency for CWSs:

7.1.3.1 If a CWS serving twenty-five (25) to one thousand (1000) persons has no history of total coliform contamination in its current configuration and a sanitary survey conducted in the past five (5) years shows that the system is supplied solely by a protected ground water source and is free of sanitary defects, the Division may reduce the monitoring frequency specified above, except that in no case may the Division reduce the monitoring frequency to less than one (1) sample per quarter. The Division must approve the reduced monitoring frequency in writing.

7.1.4 NCWS Sampling Frequency:

7.1.4.1 The supplier of water for a NCWS and NTNCWS shall sample for total coliform bacteria in accordance with the following:

7.1.4.1.1 A NCWS and NTNCWS using only ground water (except ground water under the direct influence of surface water) and serving one thousand (1000) persons or fewer must monitor each calendar quarter that the system provides water to the public, except that the Division may reduce this monitoring frequency, in writing, if a sanitary survey shows that the system is free of sanitary defects. Beginning June 29, 1994 the Division cannot reduce the monitoring frequency for a NCWS using only ground water (except ground water under the direct influence of surface water) and serving one thousand (1000) persons or fewer to less than once per year.

7.1.4.1.2 A NCWS and NTNCWS using only ground water (except ground water under the direct influence of surface water) and serving more than one thousand (1000) persons during any month must monitor at the same frequency as a like-sized CWS, as specified in subsection 7.1.2, except the Division may reduce this monitoring frequency, in writing, for any month the system serves one thousand (1000) persons or fewer. The Division cannot reduce the monitoring frequency to less than once per year. For systems using ground water under the direct influence of surface water, subsection 7.1.4.1.4 applies.

7.1.4.1.3 A NCWS and NTNCWS using surface water, in total or in part, must monitor at the same frequency as a like-sized CWS, as specified in subsection 7.1.2, regardless of the number of persons it serves.

7.1.4.1.4 A NCWS and NTNCWS using ground water under the direct influence of surface water must monitor at the same frequency as a like-sized CWS, as specified in subsection 7.1.2. The system must begin monitoring at this frequency beginning six (6) months after the Division determines that the ground water is under the direct influence of surface water.

7.1.5 Special Sampling for Surface Water Systems: A PWS that uses surface water or ground water under the direct influence of surface water, and does not practice filtration in compliance with subsection 1.1, must collect at least one (1) sample near the first service connection each day the turbidity level of the source water, measured as specified in subsection 7.1.2, exceeds one (1) NTU. This sample must be analyzed for the presence of total coliforms. When one (1) or more turbidity measurements in any day exceed one (1) NTU, the system must collect this coliform sample within twenty-four (24) hours of the first exceedance, unless the Division determines that the system, for logistical reasons outside the system's control, cannot have the sample analyzed within thirty (30) hours of collection. Sample results from this coliform monitoring must be included in determining the MCL for total coliforms.

7.1.6 Monthly/Quarterly Sampling: The PWS must collect samples at regular time intervals throughout the month/quarter, except that a system that uses only ground water (except ground water under the direct influence of surface water) and serves 4,900 persons or fewer, may collect all required samples on a single day if they are taken from different sites.

7.1.7 Special Purpose Samples: Special purpose samples, such as those taken to determine whether disinfection practices are sufficient following pipe placement, replacement, or repair, shall not be used to determine compliance with the MCL for total coliforms. Repeat samples taken pursuant to subsection 7.2.3 are not considered special purpose samples, and must be used to determine compliance with the MCL for total coliforms.

7.2 Microbiological MCLs

7.2.1 Total Coliforms, Fecal Coliforms and E. coli:

7.2.1.1 The MCLs for microbiological contaminants are in accordance with the following:

7.2.1.1.1 Until December 31, 2015, compliance with the MCL is based on the presence or absence of total coliforms in a sample, rather than coliform density in accordance with the following:

7.2.1.1.1.1 For a system which collects at least forty (40) samples per month/quarter, if no more than 5.0 percent of the samples collected during a month/quarter are total coliform-positive, the system is in compliance with the MCL for total coliforms.

7.2.1.1.1.2 For a system which collects fewer than forty (40) samples per month/quarter, if no more than one (1) sample collected during a month/quarter is total coliform-positive, the system is in compliance with the MCL for total coliforms.

7.2.1.1.2 Until December 31, 2015 any fecal coliform-positive repeat sample, or E. coli-positive repeat sample, or any total coliform-positive repeat sample following a fecal coliform-positive or E. coli-positive routine sample constitutes a violation of the MCL for total coliforms. For purposes of the public notification requirements in subsection 4.2, this is a violation that may pose an acute risk to health.

7.2.1.1.3 Beginning January 1, 2016, a system is in compliance with the MCL for E. coli for samples taken under the provisions of subsection 7.4 unless any of the conditions identified in subsections 7.2 .1.1.3.1 through 7.2.1.1.3.4 occur. For purposes of the public notification requirements in Section 4.0, violation of the MCL may pose an acute risk to public health.

7.2.1.1.3.1 The system has an E. coli-positive repeat sample following a total coliform-positive routine sample.

7.2.1.1.3.2 The system has a total coliform-positive sample following an E. coli-positive routine sample.

7.2.1.1.3.3 The system fails to take all required repeat samples following an E. coli-positive routine sample.

7.2.1.1.3.4 The system fails to test for E. coli when any repeat sample tests positive for total coliforms.

7.2.1.1.4 Until December 31, 2015, a public water system must determine compliance with the MCL for total coliforms in subsections 7.2.1.11 and 7.2.1.1.2 for each month in which it is required to monitor for total coliforms. Beginning January 1, 2016, a public water system must determine compliance with the MCL for E. coli in subsection 7.2.1.1.3 for each month in which it is required to monitor for total coliforms.

7.2.1.1.5 The Administrator, pursuant to section 1412 of the Safe Drinking Water Act, hereby identifies the following as the best technology, treatment techniques, or other means available for achieving compliance with the MCL for total coliforms in subsections 7.2.1.1.1 and 7.2.1.1.2 and for achieving compliance with the MCL for E. coli in subsection 7.2.1.1.3:

7.2.1.1.5.1 Protection of wells from fecal contamination by coliforms by appropriate placement and construction;

7.2.1.1.5.2 Maintenance of a disinfectant residual throughout the distribution system;

7.2.1.1.5.3 Proper maintenance of the distribution system including appropriate pipe replacement and repair procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, cross-connection and control, and continual maintenance of positive water pressure in all parts of the distribution system;

7.2.1.1.5.4 Filtration and/or disinfection of surface water, as described in Sections 16.0, 17.0, 19.0 and 20.0, or disinfection of ground water, as described in Section 8.0, using strong oxidants such as chlorine, chlorine dioxide, or ozone; and

7.2.1.1.5.5 For systems using groundwater, compliance with the requirements of an EPA-approved State Wellhead Protection Program under section 1428 of the Safe Drinking Water Act (SDWA).

7.2.1.1.6 The Administrator, pursuant to section 1412 of the Safe Drinking Water Act, hereby identifies the technology, treatment techniques, or other means available identified in subsection 7.2.1.1.5 as affordable technology, treatment techniques, or other means available to systems serving 10,000 or fewer people for achieving compliance with the MCL for total coliforms in subsections 7.2.1.1.1 and 7.2.1.1.2 and for achieving compliance with the MCL for E. coli in subsection 7.2.1.1.3.

7.2.2 Invalidation of Total Coliform-Positive Samples:

7.2.2.1 Each total coliform positive sample counts in compliance calculations, unless it has been invalidated by the Division. Invalidated samples do not count toward the minimum monitoring frequency. The Division may invalidate a sample if:

7.2.2.1.1 The analytical laboratory acknowledges that improper sample analysis caused the positive result;

7.2.2.1.2 A laboratory must invalidate a total coliform sample (unless total coliforms are detected) if the sample produces a turbid culture in the absence of gas production using an analytical method where gas formation is examined (e.g. the Multiple-Tube Fermentation Technique), produces a turbid culture in the absence of an acid reaction in the Presence-Absence (P-A) Coliform Test, or exhibits confluent growth or produces colonies too numerous to count with an analytical method using a membrane filter (e.g. Membrane Filter Technique). If a laboratory invalidates a sample because of such interference, the system must collect another sample from the same location as the original sample within twenty-four (24) hours of being notified of the interference problem, and have it analyzed for the presence of total coliforms. The system must continue to re-sample within twenty-four (24) hours and have the samples analyzed until it obtains a valid result. The Division may waive the twenty-four (24) hour time limit on a case-by-case basis.

7.2.2.1.3 The Division determines that the contamination is a domestic or other non-distribution system plumbing problem on the basis that one (1) or more repeat samples taken at the same tap as the original total coliform positive sample is total coliform positive, but all repeat samples at nearby sampling locations that are within five (5) service connections of the original tap are total coliform negative. A total coliform-positive sample cannot be invalidated under this provision if the PWS has only one (1) service connection; or

7.2.2.1.4 The Division has substantial grounds to believe that a total coliform positive result is due to some circumstance or condition which does not reflect water quality in the distribution system, if:

7.2.2.1.4.1 The basis for this determination is documented in writing.

7.2.2.1.4.2 This document is signed and approved by the Division.

7.2.2.1.4.3 The documentation is made available to EPA and the public. The written documentation must state the specific cause of the total coliform-positive sample, and what action the system has taken, or will take, to correct this problem.

7.2.2.1.4.4 The system must still collect all repeat samples required under subsection 7.2.3 to determine compliance with the MCL for total coliforms in subsection 7.2.1.

7.2.3 Repeat Monitoring:

7.2.3.1 When a total coliform-positive sample result is obtained, repeat sampling must be done in accordance with the following:

7.2.3.1.1 If a routine sample is total-coliform positive, the PWS must collect a set of repeat samples within twenty-four (24) hours of being notified of the positive result. A system which collects more than one (1) routine sample/month must collect no fewer than three (3) repeat samples for each total coliform positive sample found. A system which collects one (1) routine sample/month or fewer must collect no fewer than four (4) repeat samples for each total coliform positive sample found. The Division may extend the twenty-four (24) hour limit on a case-by-case basis if the system has a logistical problem in collecting the repeat samples within twenty-four hours that is beyond its control. In the case of an extension, the Division must specify how much time the system has to collect the repeat samples.

7.2.3.1.2 The system must collect at least one (1) repeat sample from the sampling tap where the original total coliform-positive sample was taken, and at least one (1) repeat sample at a tap within five (5) service connections upstream and at least one (1) repeat sample at a tap within five (5) service connections downstream of the original sampling site. If a total coliform-positive sample is at the end of the distribution system, or one (1) away from the end of the distribution system, the Division may waive the requirement to collect at least one (1) repeat sample upstream or downstream of the original sampling site.

7.2.3.1.3 The system must collect all repeat samples on the same day, except that the Division may allow a system with a single service connection to collect the required set of repeat samples over a four (4) day period or to collect a larger volume repeat sample(s) in one (1) or more sample containers of any size, as long as the total volume collected is at least four hundred (400) ml [three hundred (300) ml for systems which collect more than one (1) routine sample/month].

7.2.3.1.4 If one (1) or more repeat samples in the set is total coliform-positive, the PWS must collect an additional set of repeat samples in the manner specified in subsections 7.2.1, 7.2.2, and 7.2.3. The additional samples must be collected within twenty-four (24) hours of being notified of the positive result, unless the Division extends the limit as provided in subsection 7.2.1. The system must repeat this process until either total coliforms are not detected in one (1) complete set of repeat samples or the system determines that the MCL for total coliforms in subsection 7.2.1 has been exceeded and notifies the Division.

7.2.3.1.5 If a system collecting fewer than five (5) routine samples per month has one (1) or more total coliform-positive samples and the Division does not invalidate the sample(s) under subsection 7.2.2, it must collect at least five (5) routine samples during the next month the system provides water to the public, except that the Division may waive this requirement if the conditions of subsections 7.2.3.1.5.1 and 7.2.3.1.5.2 are met. The Division cannot waive the requirement for a system to collect repeat samples in subsections 7.2.3.1.1, 7.2.3.1.2, 7.2.3.1.3, and 7.2.3.1.4.

7.2.3.1.5.1 The Division may waive the requirements to collect five (5) routine samples the next month the system provides water to the public if the Division, or an agent approved by the Division, performs a site visit before the end of the next month the system provides water to the public. Although a sanitary survey need not be performed, the site visit must be sufficiently detailed to allow the Division to determine whether additional monitoring and/or any corrective action is needed. The Division cannot approve an employee of the system to perform the site visit, even if the employee is an agent approved by the Division to perform sanitary surveys.

7.2.3.1.5.2 The Division may waive the requirements to collect five (5) routine samples the next month the system provides water to the public if the Division has determined why the sample was total coliform-positive and establishes that the system has corrected the problem or will correct the problem before the end of the next month the system serves water to the public. In this case, the Division must document this decision to waive the following month's additional monitoring requirement in writing, have it approved and signed by the supervisor of the Division official who recommends such a decision, and make this document available to the EPA and the public. The written documentation must describe the specific cause of the total coliform-positive sample and what action the system has taken and/or will take to correct this problem. The Division cannot waive the requirement to collect five (5) routine samples the next month the system provides water to the public solely on the grounds that all coliform samples are total coliform-negative. Under this paragraph, a system must still take at least one (1) routine sample before the end of the next month it serves water to the public and use it to determine compliance with the MCL for total coliforms in subsection 7.2.1, unless the Division has determined that the system has corrected the contamination problem before the system took the set of repeat samples required in subsections 7.2.3.1.1, 7.2.3.1.2, 7.2.3.1.3, and 7.2.3.1.4, and all repeat samples were total coliform negative.

7.2.3.1.6 After a systems collects a routine sample and before it learns the results of the analysis of that sample, if it collects another routine sample(s) from within five (5) adjacent service connections of the initial sample, and the initial sample, after analysis, is found to contain total coliforms, then the system may count the subsequent sample(s) as a repeat sample instead of a routine sample.

7.2.3.1.7 Results of all routine and repeat samples not invalidated by the Division must be included in determining compliance with the MCL for total coliforms in subsection 7.2.1.

7.2.4 Initial/Subsequent Sanitary Surveys: PWSs which do not collect five (5) or more routine samples/month must undergo an initial sanitary survey by June 29, 1994 for CWSs and June 29, 1999 for NCWSs. Thereafter, systems must undergo another sanitary survey every five (5) years, except that NCWSs using only protected and disinfected ground water, as defined by the Division, must undergo subsequent sanitary surveys at least every ten (10) years after the initial sanitary survey. The Division must review the results of each sanitary survey to determine whether the existing monitoring frequency is adequate and what additional measures, if any, the system needs to undertake to improve drinking water quality. In conducting a sanitary survey of a system using ground water in a State having an EPA-approved wellhead protection program under section 1428 of the SDWA, information on sources of contamination within the delineated wellhead protection area that was collected in the course of developing and implementing the program should be considered instead of collecting new information, if the information was collected since the last time the system was subject to a sanitary survey. Sanitary surveys must be performed by the Division and the system is responsible for ensuring the survey takes place.

7.2.5 Fecal Coliforms/Escherichia coli(E. coli) Testing:

7.2.5.1 When a total coliform-positive sample result is obtained, the sample must be analyzed for fecal coliforms or E. coli in accordance with the following:

7.2.5.1.1 If any routine or repeat sample is total coliform-positive, the system must analyze that total coliform-positive culture medium to determine if fecal coliforms are present, except that the system may test for E. coli in lieu of fecal coliforms. If fecal coliforms or E. coli are present, the system shall notify the Division by the end of the day when the system is notified of the test result, unless the system is notified of the result after the Division office is closed, in which case the system shall notify the Division before the end of the next business day.

7.2.5.1.2 The Division has the discretion to allow the PWS, on a case by case basis, to forgo fecal coliform or E. coli testing on a total coliform-positive sample if that system assumes that the total coliform-positive sample is fecal coliform-positive or E. coli positive. Accordingly, the system shall notify the Division as specified in subsection 7.2.1.1.1 and the provisions of subsection 7.2.1.1.2 apply.

7.2.6 Response to Violation. A PWS which has exceeded the MCL for total coliforms in subsection 7.2.1 must report the violation to the Division no later than the end of the next business day after it learns of the violation, and notify the public in accordance with subsection 4.1. A PWS which has failed to comply with a coliform monitoring requirement, including the sanitary survey requirement, must report the monitoring violation to the Division within ten (10) days after the system discovers the violation, and notify the public in accordance with subsection 4.1.

7.2.7 The provisions of subsections 7.1.1 and 7.2.4 are applicable until December 31, 2015. The provisions of subsections 7.2.2, 7.2.3, 7.2.5, 7.3 and 7.2.6 are applicable until all required repeat monitoring under subsection 7.2 .3 and fecal coliform or E. coli testing under subsection 7.2.5 that was initiated by a total coliform-positive sample taken before January 1, 2016 is completed, as well as analytical method, reporting, recordkeeping, public notification, and consumer confidence report requirements associated with that monitoring and testing. Beginning January 1, 2016, the provisions of subsection 7.4 are applicable, with systems required to begin regular monitoring at the same frequency as the system-specific frequency required on December 31, 2015.

7.3 Analytical Requirements

7.3.1 Analytical Methodology. The standard sample volume required for total coliform analysis, regardless of analytical method used, is one hundred (100) ml. Public water systems need only determine the presence or absence of total coliforms. A determination of total coliform density is not required. Public water systems must conduct total coliform analyses in accordance with 40 CFR 141.21(f)(3). Copies may be obtained from the Office of Drinking Water.

7.4 Revised Total Coliform Rule

7.4.1 General.

7.4.1.1 General. The provisions of this subpart include both maximum contaminant level and treatment technique requirements.

7.4.1.2 Applicability. The provisions of this subpart apply to all public water systems.

7.4.1.3 Compliance date. Systems must comply with the provisions of this subpart beginning January 1, 2016, unless otherwise specified in this subpart.

7.4.1.4 Implementation with EPA as State. Systems falling under direct oversight of EPA, where EPA acts as the State, must comply with decisions made by EPA for implementation of subpart Y. EPA has authority to establish such procedures and criteria as are necessary to implement subpart Y.

7.4.1.5 Violations of national primary drinking water regulations. Failure to comply with the applicable requirements of §§ 141.851 through 141.861, including requirements established by the State pursuant to these provisions, is a violation of the national primary drinking water regulations under subpart Y.

7.4.2 Analytical methods and laboratory certification.

7.4.2.1 Analytical methodology.

7.4.2.1.1 The standard sample volume required for analysis, regardless of analytical method used, is 100 ml.

7.4.2.1.2 Systems need only determine the presence or absence of total coliforms and E. coli; a determination of density is not required.

7.4.2.1.3 The time from sample collection to initiation of test medium incubation may not exceed 30 hours. Systems are encouraged but not required to hold samples below 10° C during transit.

7.4.2.1.4 If water having residual chlorine (measured as free, combined, or total chlorine) is to be analyzed, sufficient sodium thiosulfate (Na2S2O3) must be added to the sample bottle before sterilization to neutralize any residual chlorine in the water sample. Dechlorination procedures are addressed in Section 9060A.2 of Standard Methods for the Examination of Water and Wastewater (20th and 21st editions).

7.4.2.1.5 Systems must conduct total coliform and E. coli analyses in accordance with one of the analytical methods in the following table or one of the alternative methods listed in Appendix A subsection 7.4.2.

Organism	Methodology category	Method1	Citation1
Total Coliforms	Lactose Fermentation Methods	Standard Total Coliform Fermentation Technique	Standard Methods 9221 B.1, B.2 (20th ed.; 21st ed.)2 3 Standard Methods Online 9221 B.1, B.2-992 3
		Presence-Absence (P-A) Coliform Test.	Standard Methods 9221 D.1, D.2 (20th ed.; 21st ed.)2 7 Standard Methods Online 9221 D.1, D.2-992 7
	Membrane Filtration Methods	Standard Total Coliform Membrane Filter Procedure.	Standard Methods 9222 B, C (20th ed.; 21st ed.)2 4
			Standard Methods Online 9222 B-97 2 4, 9222 C-972 4
		Membrane Filtration using MI medium. m-ColiBlue24® Test 2 4 Chromocult2 4	EPA Method 16042
	Enzyme Substrate Methods	Colilert®	Standard Methods 9223 B (20th ed.; 21st ed.)2 5
		Standard Methods Online 9223 B-972 5 Colisure® E*Colite® Test2 Readycult® Test2 modified Colitag® Test2	Standard Methods 9223 B (20th ed.; 21st ed.)2 5 6 Standard Methods Online 9223 B-972 5 6
Escherichia coli	Escherichia coli Procedure (following Lactose Fermentation Methods). Escherichia coli Partition Method	EC-MUG medium	Standard Methods 9221 F.1 (20th ed.; 21st ed.)2
		EC broth with MUG (EC-MUG)	Standard Methods 9222 G.1c(2) (20th ed.; 21st ed.)2 8
		NA-MUG medium	Standard Methods 9222 G.1c(1) (20th ed.; 21st ed.)2
	Membrane Filtration Methods	Membrane Filtration using MI medium.	EPA Method 16042
		m-ColiBlue24® Test24
		Chromocult2 4
	Enzyme Substrate Methods	Colilert®	Standard Methods 9223 B (20th ed.; 21st ed.)2 5 Standard Methods Online 9223 B-972 5 6
		Colisure® E*Colite® Test2 Readycult® Test2 modified Colitag® Test2	Standard Methods 9223 B (20th ed.; 21st ed.)2 5 6 Standard Methods Online 9223 B-972 5 6

¹ The procedures must be done in accordance with the documents listed in subsection 7.4.2.3. For Standard Methods, either editions, 20th (1998) or 21st (2005), may be used. For the Standard Methods Online, the year in which each method was approved by the Standard Methods Committee is designated by the last two digits following the hyphen in the method number. The methods listed are the only online versions that may be used. For vendor methods, the date of the method listed in subsection 7.4.2.3 is the date/version of the approved method. The methods listed are the only versions that may be used for compliance with this rule. Laboratories should be careful to use only the approved versions of the methods, as product package inserts may not be the same as the approved versions of the methods.

² Incorporated by reference. See subsection 7.4.2.3.

³ Lactose broth, as commercially available, may be used in lieu of lauryl tryptose broth, if the system conducts at least 25 parallel tests between lactose broth and lauryl tryptose broth using the water normally tested, and if the findings from this comparison demonstrate that the false positive rate and false-negative rate for total coliforms, using lactose broth, is less than 10 percent.

⁴ All filtration series must begin with membrane filtration equipment that has been sterilized by autoclaving. Exposure of filtration equipment to UV light is not adequate to ensure sterilization. Subsequent to the initial autoclaving, exposure of the filtration equipment to UV light may be used to sanitize the funnels between filtrations within a filtration series. Alternatively, membrane filtration equipment that is pre-sterilized by the manufacturer (i.e., disposable funnel units) may be used.

⁵ Multiple-tube and multi-well enumerative formats for this method are approved for use in presence-absence determination under this regulation.

⁶ ColisureR results may be read after an incubation time of 24 hours.

⁷ A multiple tube enumerative format, as described in Standard Methods for the Examination of Water and Wastewater 9221, is approved for this method for use in presence-absence determination under this regulation.

⁸ The following changes must be made to the EC broth with MUG (EC-MUG) formulation: Potassium dihydrogen phosphate, KH2PO4, must be 1.5g, and 4-methylumbelliferyl-Beta-D-glucuronide must be 0.05 g.

7.4.2.2 Laboratory certification. Systems must have all compliance samples required under this subpart analyzed by a laboratory certified by the EPA or a primacy State to analyze drinking water samples. The laboratory used by the system must be certified for each method (and associated contaminant(s)) used for compliance monitoring analyses under this rule.

7.4.2.3 Incorporation by reference. The standards required in this section are incorporated by reference into this section with the approval of the Director of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51 . To enforce any edition other than that specified in this section, EPA must publish notice of change in the Federal Register and the material must be available to the public. All approved material is available for inspection either electronically at www.regulations.gov, in hard copy at the Water Docket, or from the sources indicated below. The Docket ID is EPA-HQ-OW-2008-0878. Hard copies of these documents may be viewed at the Water Docket in the EPA Docket Center, (EPA/DC) EPA West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. The EPA Docket Center Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is 1-202-566-1744, and the telephone number for the Water Docket is 1-202-566-2426. Copyrighted materials are only available for viewing in hard copy. These documents are also available for inspection at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 1-202-741-6030 or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

7.4.2.3.1 American Public Health Association, 800 I Street, NW., Washington, DC 20001.

7.4.2.3.1.1 "Standard Methods for the Examination of Water and Wastewater," 20th edition (1998):

7.4.2.3.1.1.1 Standard Methods 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group," B.1, B.2, "Standard Total Coliform Fermentation Technique."

7.4.2.3.1.1.2 Standard Methods 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group," D.1, D.2, "Presence-Absence (P-A) Coliform Test."

7.4.2.3.1.1.3 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," B, "Standard Total Coliform Membrane Filter Procedure."

7.4.2.3.1.1.4 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," C, "Delayed-Incubation Total Coliform Procedure."

7.4.2.3.1.1.5 Standard Methods 9223, "Enzyme Substrate Coliform Test," B, "Enzyme Substrate Test," Colilert® and Colisure®.

7.4.2.3.1.1.6 Standard Methods 9221, "Multiple Tube Fermentation Technique for Members of the Coliform Group," F.1, "Escherichia coli Procedure: EC-MUG medium."

7.4.2.3.1.1.7 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," G.1.c(2), "Escherichia coli Partition Method: EC broth with MUG (EC-MUG)."

7.4.2.3.1.1.8 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," G.1.c(1), "Escherichia coli Partition Method: NA-MUG medium."

7.4.2.3.1.2 "Standard Methods for the Examination of Water and Wastewater," 21st edition (2005):

7.4.2.3.1.2.1 Standard Methods 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group," B.1, B.2, "Standard Total Coliform Fermentation Technique."

7.4.2.3.1.2.2 Standard Methods 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group," D.1, D.2, "Presence-Absence (P-A) Coliform Test."

7.4.2.3.1.2.3 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," B, "Standard Total Coliform Membrane Filter Procedure."

7.4.2.3.1.2.4 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," C, "Delayed-Incubation Total Coliform Procedure."

7.4.2.3.1.2.5 Standard Methods 9223, "Enzyme Substrate Coliform Test," B, "Enzyme Substrate Test," Colilert® and Colisure®.

7.4.2.3.1.2.6 Standard Methods 9221, "Multiple Tube Fermentation Technique for Members of the Coliform Group," F.1, "Escherichia coli Procedure: EC-MUG medium."

7.4.2.3.1.2.7 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," G.1.c(2), "Escherichia coli Partition Method: EC broth with MUG (EC-MUG)."

7.4.2.3.1.2.8 Standard Methods 9222, "Membrane Filter Technique for Members of the Coliform Group," G.1.c(1), "Escherichia coli Partition Method: NA-MUG medium."

7.4.2.3.1.3 "Standard Methods Online" available at http://www.standardmethods.org:

7.4.2.3.1.3.1 Standard Methods Online 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group" (1999), B.1, B.2-99, "Standard Total Coliform Fermentation Technique."

7.4.2.3.1.3.2 Standard Methods Online 9221, "Multiple-Tube Fermentation Technique for Members of the Coliform Group" (1999), D.1, D.2-99, "Presence-Absence (P-A) Coliform Test."

7.4.2.3.1.3.3 Standard Methods Online 9222, "Membrane Filter Technique for Members of the Coliform Group" (1997), B-97, "Standard Total Coliform Membrane Filter Procedure."

7.4.2.3.1.3.4 Standard Methods Online 9222, "Membrane Filter Technique for Members of the Coliform Group" (1997), C-97, "Delayed-Incubation Total Coliform Procedure."

7.4.2.3.1.3.5 Standard Methods Online 9223, "Enzyme Substrate Coliform Test" (1997), B-97, "Enzyme Substrate Test", Colilert® and Colisure®.

7.4.2.3.2 Charm Sciences, Inc., 659 Andover Street, Lawrence, MA 01843-1032, telephone 1-800-343-2170:

7.4.2.3.2.1 E*Colite®-"Charm E*ColiteTM Presence/Absence Test for Detection and Identification of Coliform Bacteria and Escherichia coli in Drinking Water," January 9, 1998.

7.4.2.3.2.2 Reserved

7.4.2.3.3 CPI International, Inc., 5580 Skylane Blvd., Santa Rosa, CA, 95403, telephone 1-800-878-7654:

7.4.2.3.3.1 modified Colitag®, ATP D05-0035-"Modified ColitagTM Test Method for the Simultaneous Detection of E. coli and other Total Coliforms in Water," August 28, 2009.

7.4.2.3.3.2 Reserved

7.4.2.3.4 EMD Millipore (a division of Merck KGaA, Darmstadt Germany), 290 Concord Road, Billerica, MA 01821, telephone 1-800-645-5476:

7.4.2.3.4.1 Chromocult-"Chromocult® Coliform Agar Presence/Absence Membrane Filter Test Method for Detection and Identification of Coliform Bacteria and Escherichia coli for Finished Waters," November 2000, Version 1.0.

7.4.2.3.4.2 Readycult®-"Readycult® Coliforms 100 Presence/Absence Test for Detection and Identification of Coliform Bacteria and Escherichia coli in Finished Waters," January 2007, Version 1.1.

7.4.2.3.5 EPA's Water Resource Center (MC-4100T), 1200 Pennsylvania Avenue NW., Washington, DC 20460, telephone 1-202-566-1729:

7.4.2.3.5.1 EPA Method 1604, EPA 821-R-02-024-"EPA Method 1604: Total Coliforms and Escherichia coli in Water by Membrane Filtration Using a Simultaneous Detection Technique (MI Medium)," September 2002, http://www.epa.gov/nerlcwww/1604sp02.pdf.

7.4.2.3.5.2 Reserved

7.4.2.3.6 Hach Company, P.O. Box 389, Loveland, CO 80539, telephone 1-800-604-3493:

7.4.2.3.6.1 m-ColiBlue24®-"Membrane Filtration Method m-ColiBlue24® Broth," Revision 2, August 17, 1999.

7.4.2.3.6.2 Reserved

7.4.3 General monitoring requirements for all public water systems.

7.4.3.1 Sample siting plans.

7.4.3.1.1 Systems must develop a written sample siting plan that identifies sampling sites and a sample collection schedule that are representative of water throughout the distribution system not later than December 31, 2015. These plans are subject to Division review and revision. Systems must collect total coliform samples according to the written sample siting plan. Monitoring required by 7.4.4 through 7.4.8 may take place at a customer's premise, dedicated sampling station, or other designated compliance sampling location. Routine and repeat sample sites and any sampling points necessary to meet the requirements of subpart S must be reflected in the sampling plan.

7.4.3.1.2 Systems must collect samples at regular time intervals throughout the month, except that systems that use only ground water and serve 4,900 or fewer people may collect all required samples on a single day if they are taken from different sites.

7.4.3.1.3 Systems must take at least the minimum number of required samples even if the system has had an E. coli MCL violation or has exceeded the coliform treatment technique triggers in subsection 7.4 .9.1.

7.4.3.1.4 A system may conduct more compliance monitoring than is required by this subpart to investigate potential problems in the distribution system and use monitoring as a tool to assist in uncovering problems. A system may take more than the minimum number of required routine samples and must include the results in calculating whether the coliform treatment technique trigger in subsections 7.4.9.1.1.1 and 7.4.9.1.1.2 has been exceeded only if the samples are taken in accordance with the existing sample siting plan and are representative of water throughout the distribution system.

7.4.3.1.5 Systems must identify repeat monitoring locations in the sample siting plan. Unless the provisions of subsections 7.4.3.1.5.1 or 7.4.3.1.5.2 are met, the system must collect at least one repeat sample from the sampling tap where the original total coliform-positive sample was taken, and at least one repeat sample at a tap within five service connections upstream and at least one repeat sample at a tap within five service connections downstream of the original sampling site. If a total coliform-positive sample is at the end of the distribution system, or one service connection away from the end of the distribution system, the system must still take all required repeat samples. However, the Division may allow an alternative sampling location in lieu of the requirement to collect at least one repeat sample upstream or downstream of the original sampling site. Except as provided for in subsection 7.4.3.1.5.2, systems required to conduct triggered source water monitoring under subsection 8.3.1 must take ground water source sample(s) in addition to repeat samples required under this subpart.

7.4.3.1.5.1 Systems may propose repeat monitoring locations to the Division that the system believes to be representative of a pathway for contamination of the distribution system. A system may elect to specify either alternative fixed locations or criteria for selecting repeat sampling sites on a situational basis in a standard operating procedure (SOP) in its sample siting plan. The system must design its SOP to focus the repeat samples at locations that best verify and determine the extent of potential contamination of the distribution system area based on specific situations. The Division may modify the SOP or require alternative monitoring locations as needed.

7.4.3.1.5.2 Ground water systems serving 1,000 or fewer people may propose repeat sampling locations to the Division that differentiate potential source water and distribution system contamination (e.g., by sampling at entry points to the distribution system). A ground water system with a single well required to conduct triggered source water monitoring may, with written Division approval, take one of its repeat samples at the monitoring location required for triggered source water monitoring under subsection 8.3.1 if the system demonstrates to the Division's satisfaction that the sample siting plan remains representative of water quality in the distribution system. If approved by the Division, the system may use that sample result to meet the monitoring requirements in both subsection 8.3.1 and this section.

7.4.3.1.5.2.1 If a repeat sample taken at the monitoring location required for triggered source water monitoring is E. coli-positive, the system has violated the E. coli MCL and must also comply with subsection 8.3.1.2.3. If a system takes more than one repeat sample at the monitoring location required for triggered source water monitoring, the system may reduce the number of additional source water samples required under subsection 8.3.1.2.3 by the number of repeat samples taken at that location that were not E. coli-positive.

7.4.3.1.5.2.2 If a system takes more than one repeat sample at the monitoring location required for triggered source water monitoring under subsection 8.3.1, and more than one repeat sample is E. coli-positive, the system has violated the E. coli MCL and must also comply with subsection 8.4.1.

7.4.3.1.5.2.3 If all repeat samples taken at the monitoring location required for triggered source water monitoring are E. coli-negative and a repeat sample taken at a monitoring location other than the one required for triggered source water monitoring is E. coli-positive, the system has violated the E. coli MCL, but is not required to comply with subsection 8.3 .1.2.3.

7.4.3.1.6 States may review, revise, and approve, as appropriate, repeat sampling proposed by systems under subsections 7.4.3.1.5.1 and 7.4.3.1.5.2. The system must demonstrate that the sample siting plan remains representative of the water quality in the distribution system. The Division may determine that monitoring at the entry point to the distribution system (especially for undisinfected ground water systems) is effective to differentiate between potential source water and distribution system problems.

7.4.3.2 Special purpose samples. Special purpose samples, such as those taken to determine whether disinfection practices are sufficient following pipe placement, replacement, or repair, must not be used to determine whether the coliform treatment technique trigger has been exceeded. Repeat samples taken pursuant to subsection 7.4.8 are not considered special purpose samples, and must be used to determine whether the coliform treatment technique trigger has been exceeded.

7.4.3.3 Invalidation of total coliform samples. A total coliform-positive sample invalidated under subsection 7.4.3.3 does not count toward meeting the minimum monitoring requirements of this subpart.

7.4.3.3.1 The Division may invalidate a total coliform-positive sample only if the conditions of subsections 7.4.3.3.1.1, 7.4.3.3.1.2 or 7.4.3.3.1.3 are met.

7.4.3.3.1.1 The laboratory establishes that improper sample analysis caused the total coliform-positive result.

7.4.3.3.1.2 The Division, on the basis of the results of repeat samples collected as required under subsection 7.4.8.1, determines that the total coliform-positive sample resulted from a domestic or other non-distribution system plumbing problem. The Division cannot invalidate a sample on the basis of repeat sample results unless all repeat sample(s) collected at the same tap as the original total coliform positive sample are also total coliform positive, and all repeat samples collected at a location other than the original tap are total coliform-negative (e.g., a State cannot invalidate a total coliform-positive sample on the basis of repeat samples if all the repeat samples are total coliform-negative, or if the system has only one service connection).

7.4.3.3.1.3 The Division has substantial grounds to believe that a total coliform-positive result is due to a circumstance or condition that does not reflect water quality in the distribution system. In this case, the system must still collect all repeat samples required under subsection 7.4.8.1, and use them to determine whether a coliform treatment technique trigger in subsection 7.4.9 has been exceeded. To invalidate a total coliform-positive sample under this paragraph, the decision and supporting rationale must be documented in writing, and approved and signed by the supervisor of the Division official who recommended the decision. The Division must make this document available to EPA and the public. The written documentation must state the specific cause of the total coliform-positive sample, and what action the system has taken, or will take, to correct this problem. The Division may not invalidate a total coliform-positive sample solely on the grounds that all repeat samples are total coliform negative.

7.4.3.3.2 A laboratory must invalidate a total coliform sample (unless total coliforms are detected) if the sample produces a turbid culture in the absence of gas production using an analytical method where gas formation is examined (e.g., the Multiple-Tube Fermentation Technique), produces a turbid culture in the absence of an acid reaction in the Presence-Absence (P-A) Coliform Test, or exhibits confluent growth or produces colonies too numerous to count with an analytical method using a membrane filter (e.g., Membrane Filter Technique). If a laboratory invalidates a sample because of such interference, the system must collect another sample from the same location as the original sample within 24 hours of being notified of the interference problem, and have it analyzed for the presence of total coliforms. The system must continue to re-sample within 24 hours and have the samples analyzed until it obtains a valid result. The Division may waive the 24-hour time limit on a case-by-case basis. Alternatively, the Division may implement criteria for waiving the 24-hour sampling time limit to use in lieu of case-by-case extensions.

7.4.4 Routine monitoring requirements for non-community water systems serving 1,000 or fewer people using only ground water.

7.4.4.1 General.

7.4.4.1.1 The provisions of this section apply to non-community water systems using only ground water (except ground water under the direct influence of surface water, as defined in Section 2.0) and serving 1,000 or fewer people.

7.4.4.1.2 Following any total coliform positive sample taken under the provisions of this section, systems must comply with the repeat monitoring requirements and E. coli analytical requirements in subsection 7.4 .8.

7.4.4.1.3 Once all monitoring required by this section and subsection 7.4.8 for a calendar month has been completed, systems must determine whether any coliform treatment technique triggers specified in subsection 7.4.9 have been exceeded. If any trigger has been exceeded, systems must complete assessments as required by subsection 7.4.9.

7.4.4.1.4 For the purpose of determining eligibility for remaining on or qualifying for quarterly monitoring under the provisions of subsection 7.4.4.6.4 and 7.4.4.7.2, respectively, for transient non-community water systems, the Division may elect to not count monitoring violations under subsection 7.4.10.3.1 if the missed sample is collected no later than the end of the monitoring period following the monitoring period in which the sample was missed. The system must collect the make-up sample in a different week than the routine sample for that monitoring period and should collect the sample as soon as possible during the monitoring period. The Division may not use this provision under subsection 7.4.4.8. This authority does not affect the provisions of subsections 7.4.10.3.1 and 7.4.11.1.4.

7.4.4.2 Monitoring frequency for total coliforms. Systems must monitor each calendar quarter that the system provides water to the public, except for seasonal systems or as provided under subsections 7.4.4.3 through 7.4.4.8 and 7.4.4.10. Seasonal systems must meet the monitoring requirements of subsection 7.4.4.9.

7.4.4.3 Transition to subsection 7.4 (Revised Total Coliform Rule).

7.4.4.3.1 Systems, including seasonal systems, must continue to monitor according to the total coliform monitoring schedules under subsection 7.1 that were in effect on December 31, 2015, unless any of the conditions for increased monitoring in subsection 7.4.4.6 are triggered on or after January 1, 2016, or unless otherwise directed by the Division.

7.4.4.3.2 Beginning January 1, 2016, the Division must perform a special monitoring evaluation during each sanitary survey to review the status of the system, including the distribution system, to determine whether the system is on an appropriate monitoring schedule. After the Division has performed the special monitoring evaluation during each sanitary survey, the Division may modify the system's monitoring schedule, as necessary, or it may allow the system to stay on its existing monitoring schedule, consistent with the provisions of this section. The Division may not allow systems to begin less frequent monitoring under the special monitoring evaluation unless the system has already met the applicable criteria for less frequent monitoring in this section. For seasonal systems on quarterly or annual monitoring, this evaluation must include review of the approved sample siting plan, which must designate the time period(s) for monitoring based on site-specific considerations (e.g., during periods of highest demand or highest vulnerability to contamination). The seasonal system must collect compliance samples during these time periods.

7.4.4.4 Annual site visits. Systems on annual monitoring, including seasonal systems, must have an initial and recurring annual site visit by the Division that is equivalent to a Level 2 assessment or an annual voluntary Level 2 assessment that meets the criteria in subsection 7.4.9.2 to remain on annual monitoring. The periodic required sanitary survey may be used to meet the requirement for an annual site visit for the year in which the sanitary survey was completed.

7.4.4.5 Criteria for annual monitoring. The Division may reduce the monitoring frequency for a well-operated ground water system from quarterly routine monitoring to no less than annual monitoring, if the system demonstrates that it meets the criteria for reduced monitoring in subsections 7.4.4.5.1 through 7.4.4.5.3, except for a system that has been on increased monitoring under the provisions of subsection 7.4.4.6. A system on increased monitoring under subsection 7.4.4.6 must meet the provisions of subsection 7.4.4.7 to go to quarterly monitoring and must meet the provisions of subsection 7.4.4.8 to go to annual monitoring.

7.4.4.5.1 The system has a clean compliance history for a minimum of 12 months;

7.4.4.5.2 The most recent sanitary survey shows that the system is free of sanitary defects or has corrected all identified sanitary defects, has a protected water source, and meets approved construction standards; and

7.4.4.5.3 The Division has conducted an annual site visit within the last 12 months and the system has corrected all identified sanitary defects. The system may substitute a Level 2 assessment that meets the criteria in subsection 7.4.9.2 for the Division's annual site visit.

7.4.4.6 Increased Monitoring Requirements for systems on quarterly or annual monitoring. A system on quarterly or annual monitoring that experiences any of the events identified in subsections 7.4.4.6.1 through 7.4.4.6.4 must begin monthly monitoring the month following the event. A system on annual monitoring that experiences the event identified in subsection 7.4 .4.6.5 must begin quarterly monitoring the quarter following the event. The system must continue monthly or quarterly monitoring until the requirements in subsection 7.4.4.7 for quarterly monitoring or subsection 7.4.4.8 for annual monitoring are met. A system on monthly monitoring for reasons other than those identified in subsections 7.4.4.6.1 through 7.4.4.6.4 is not considered to be on increased monitoring for the purposes of subsections 7.4.4.7 and 7.4.4.8.

7.4.4.6.1 The system triggers a Level 2 assessment or two Level 1 assessments under the provisions of subsection 7.4.9 in a rolling 12-month period.

7.4.4.6.2 The system has an E. coli MCL violation.

7.4.4.6.3 The system has a coliform treatment technique violation.

7.4.4.6.4 The system has two subsection 7.4 monitoring violations or one subsection 7.4 monitoring violation and one Level 1 assessment under the provisions of subsection 7.4.9 in a rolling 12-month period for a system on quarterly monitoring.

7.4.4.6.5 The system has one subsection 7.4 monitoring violation for a system on annual monitoring.

7.4.4.7 Requirements for returning to quarterly monitoring. The Division may reduce the monitoring frequency for a system on monthly monitoring triggered under 7.4.4.6 to quarterly monitoring if the system meets the criteria in subsections 7.4.4.7.1 and 7.4.4.7.2.

7.4.4.7.1 Within the last 12 months, the system must have a completed sanitary survey or a site visit by the Division or a voluntary Level 2 assessment by a party approved by the Division, be free of sanitary defects, and have a protected water source; and

7.4.4.7.2 The system must have a clean compliance history for a minimum of 12 months.

7.4.4.8 Requirements for systems on increased monitoring to qualify for annual monitoring. The Division may reduce the monitoring frequency for a system on increased monitoring under subsection 7.4.4.6 if the system meets the criteria in subsection 7.4.4.7 plus the criteria in subsections 7.4.4.8.1 and 7.4.4.8.2.

7.4.4.8.1 An annual site visit by the Division and correction of all identified sanitary defects. The system may substitute a voluntary Level 2 assessment by a party approved by the Division for the Division's annual site visit in any given year.

7.4.4.8.2 The system must have in place or adopt one or more additional enhancements to the water system barriers to contamination in subsections 7.4.4.8.2.1 through 7.4.4.8.2.5.

7.4.4.8.2.1 Cross-connection control, as approved by the Division.

7.4.4.8.2.2 An operator certified by the Division or regular visits by a circuit rider certified by the Division.

7.4.4.8.2.3 Continuous disinfection entering the distribution system and a residual in the distribution system in accordance with criteria specified by the Division.

7.4.4.8.2.4 Demonstration of maintenance of at least a 4-log removal or inactivation of viruses as provided for under subsection 8.4.2.3.

7.4.4.8.2.5 Other equivalent enhancements to water system barriers as approved by the Division.

7.4.4.9 Seasonal systems.

7.4.4.9.1 Beginning January 1, 2016, all seasonal systems must demonstrate completion of a Division-approved start-up procedure, which may include a requirement for startup sampling prior to serving water to the public.

7.4.4.9.2 A seasonal system must monitor every month that it is in operation unless it meets the criteria in subsections 7.4.4.9.2.1 through 7.4.4.9.2.3 to be eligible for monitoring less frequently than monthly beginning January 1, 2016, except as provided under subsection 7.4.4.3.

7.4.4.9.2.1 Seasonal systems monitoring less frequently than monthly must have an approved sample siting plan that designates the time period for monitoring based on site-specific considerations (e.g., during periods of highest demand or highest vulnerability to contamination). Seasonal systems must collect compliance samples during this time period.

7.4.4.9.2.2 To be eligible for quarterly monitoring, the system must meet the criteria in subsection 7.4.4.7.

7.4.4.9.2.3 To be eligible for annual monitoring, the system must meet the criteria under subsection 7.4.4.8.

7.4.4.9.3 The Division may exempt any seasonal system from some or all of the requirements for seasonal systems if the entire distribution system remains pressurized during the entire period that the system is not operating, except that systems that monitor less frequently than monthly must still monitor during the vulnerable period designated by the Division.

7.4.4.10 Additional routine monitoring the month following a total coliform positive sample. Systems collecting samples on a quarterly or annual frequency must conduct additional routine monitoring the month following one or more total coliform-positive samples (with or without a Level 1 treatment technique trigger). Systems must collect at least three routine samples during the next month, except that the Division may waive this requirement if the conditions of subsections 7.4.4.10.1, 7.4.4.10.2 or 7.4.4.10.3 are met. Systems may either collect samples at regular time intervals throughout the month or may collect all required routine samples on a single day if samples are taken from different sites. Systems must use the results of additional routine samples in coliform treatment technique trigger calculations under subsection 7.4.9.1.

7.4.4.10.1 The Division may waive the requirement to collect three routine samples the next month in which the system provides water to the public if the Division, or an agent approved by the Division, performs a site visit before the end of the next month in which the system provides water to the public. Although a sanitary survey need not be performed, the site visit must be sufficiently detailed to allow the Division to determine whether additional monitoring and/or any corrective action is needed. The Division cannot approve an employee of the system to perform this site visit, even if the employee is an agent approved by the Division to perform sanitary surveys.

7.4.4.10.2 The Division may waive the requirement to collect three routine samples the next month in which the system provides water to the public if the Division has determined why the sample was total coliform-positive and has established that the system has corrected the problem or will correct the problem before the end of the next month in which the system serves water to the public. In this case, the Division must document this decision to waive the following month's additional monitoring requirement in writing, have it approved and signed by the supervisor of the Division official who recommends such a decision, and make this document available to the EPA and public. The written documentation must describe the specific cause of the total coliform-positive sample and what action the system has taken and/or will take to correct this problem.

7.4.4.10.3 The Division may not waive the requirement to collect three additional routine samples the next month in which the system provides water to the public solely on the grounds that all repeat samples are total coliform negative. If the Division determines that the system has corrected the contamination problem before the system takes the set of repeat samples required in subsection 7.4.8, and all repeat samples were total coliform-negative, the Division may waive the requirement for additional routine monitoring the next month.

7.4.5 Routine monitoring requirements for community water systems serving 1,000 or fewer people using only ground water.

7.4.5.1 General.

7.4.5.1.1 The provisions of this section apply to community water systems using only ground water (except ground water under the direct influence of surface water, as defined in Section 2.0) and serving 1,000 or fewer people.

7.4.5.1.2 Following any total coliform positive sample taken under the provisions of this section, systems must comply with the repeat monitoring requirements and E. coli analytical requirements in subsection 7.4 .8.

7.4.5.1.3 Once all monitoring required by this section and subsection 7.4.8 for a calendar month has been completed, systems must determine whether any coliform treatment technique triggers specified in subsection 7.4.9 have been exceeded. If any trigger has been exceeded, systems must complete assessments as required by subsection 7.4.9.

7.4.5.2 Monitoring frequency for total coliforms. The monitoring frequency for total coliforms is one sample/month, except as provided for under subsections 7.4.5.3 through 7.4.5.6.

7.4.5.3 Transition to subsection 7.4.

7.4.5.3.1 All systems must continue to monitor according to the total coliform monitoring schedules under subsection 7.1 that were in effect on December 31, 2015, unless any of the conditions in subsection 7.4.5.5 are triggered on or after January 1, 2016, or unless otherwise directed by the Division.

7.4.5.3.2 Beginning January 1, 2016, the Division must perform a special monitoring evaluation during each sanitary survey to review the status of the system, including the distribution system, to determine whether the system is on an appropriate monitoring schedule. After the Division has performed the special monitoring evaluation during each sanitary survey, the Division may modify the system's monitoring schedule, as necessary, or it may allow the system to stay on its existing monitoring schedule, consistent with the provisions of this section. The Division may not allow systems to begin less frequent monitoring under the special monitoring evaluation unless the system has already met the applicable criteria for less frequent monitoring in this section.

7.4.5.4 Criteria for reduced monitoring.

7.4.5.4.1 The Division may reduce the monitoring frequency from monthly monitoring to no less than quarterly monitoring if the system is in compliance with Division certified operator provisions and demonstrates that it meets the criteria in subsections 7.4.5.4.1.1 through 7.4.5.4.1.3. A system that loses its certified operator must return to monthly monitoring the month following that loss.

7.4.5.4.1.1 The system has a clean compliance history for a minimum of 12 months.

7.4.5.4.1.2 The most recent sanitary survey shows the system is free of sanitary defects (or has an approved plan and schedule to correct them and is in compliance with the plan and the schedule), has a protected water source and meets approved construction standards.

7.4.5.4.1.3 The system meets at least one of the following criteria:

7.4.5.4.1.3.1 An annual site visit by the Division that is equivalent to a Level 2 assessment or an annual Level 2 assessment by a party approved by the Division and correction of all identified sanitary defects (or an approved plan and schedule to correct them and is in compliance with the plan and schedule).

7.4.5.4.1.3.2 Cross-connection control, as approved by the Division.

7.4.5.4.1.3.3 Continuous disinfection entering the distribution system and a residual in the distribution system in accordance with criteria specified by the Division.

7.4.5.4.1.3.4 Demonstration of maintenance of at least a 4-log removal or inactivation of viruses as provided for under subsection 8.4 .2.3.

7.4.5.4.3.1.5 Other equivalent enhancements to water system barriers as approved by the Division.

7.4.5.4.2 Reserved

7.4.5.5 Return to routine monthly monitoring requirements. Systems on quarterly monitoring that experience any of the events in subsections 7.4 .5.5.1 through 7.4.5.5.4 must begin monthly monitoring the month following the event. The system must continue monthly monitoring until it meets the reduced monitoring requirements in subsection 7.4 .5.4.

7.4.5.5.1 The system triggers a Level 2 assessment or two Level 1 assessments in a rolling 12-month period.

7.4.5.5.2 The system has an E. coli MCL violation.

7.4.5.5.3 The system has a coliform treatment technique violation.

7.4.5.5.4 The system has two subsection 7.4 monitoring violations in a rolling 12-month period.

7.4.5.6 Additional routine monitoring the month following a total coliform positive sample. Systems collecting samples on a quarterly frequency must conduct additional routine monitoring the month following one or more total coliform-positive samples (with or without a Level 1 treatment technique trigger). Systems must collect at least three routine samples during the next month, except that the Division may waive this requirement if the conditions of subsection 7.4.5.6.1, 7.4.5.6.2, or 7.4.5.6.3 are met. Systems may either collect samples at regular time intervals throughout the month or may collect all required routine samples on a single day if samples are taken from different sites. Systems must use the results of additional routine samples in coliform treatment technique trigger calculations.

7.4.5.6.1 The Division may waive the requirement to collect three routine samples the next month in which the system provides water to the public if the Division, or an agent approved by the Division, performs a site visit before the end of the next month in which the system provides water to the public. Although a sanitary survey need not be performed, the site visit must be sufficiently detailed to allow the Division to determine whether additional monitoring and/or any corrective action is needed. The Division cannot approve an employee of the system to perform this site visit, even if the employee is an agent approved by the Division to perform sanitary surveys.

7.4.5.6.2 The Division may waive the requirement to collect three routine samples the next month in which the system provides water to the public if the Division has determined why the sample was total coliform-positive and has established that the system has corrected the problem or will correct the problem before the end of the next month in which the system serves water to the public. In this case, the Division must document this decision to waive the following month's additional monitoring requirement in writing, have it approved and signed by the supervisor of the Division official who recommends such a decision, and make this document available to the EPA and the public. The written documentation must describe the specific cause of the total coliform-positive sample and what action the system has taken and/or will take to correct this problem.

7.4.5.6.3 The Division may not waive the requirement to collect three additional routine samples the next month in which the system provides water to the public solely on the grounds that all repeat samples are total coliform negative. If the Division determines that the system has corrected the contamination problem before the system takes the set of repeat samples required in subsection 7.4.8, and all repeat samples were total coliform-negative, the Division may waive the requirement for additional routine monitoring the next month.

7.4.6 Routine monitoring requirements for surface water or ground water under the direct influence of surface water public water systems serving 1,000 or fewer people.

7.4.6.1 General.

7.4.6.1.1 The provisions of this section apply to surface water or ground water under the direct influence of surface water public water systems of this part serving 1,000 or fewer people.

7.4.6.1.2 Following any total coliform positive sample taken under the provisions of this section, systems must comply with the repeat monitoring requirements and E. coli analytical requirements in subsection 7.4 .8.

7.4.6.1.3 Once all monitoring required by this section and subsection 7.4.8 for a calendar month has been completed, systems must determine whether any coliform treatment technique triggers specified in 7.4.9 have been exceeded. If any trigger has been exceeded, systems must complete assessments as required by subsection 7.4.9.

7.4.6.1.4 Seasonal systems.

7.4.6.1.4.1 Beginning January 1, 2016, all seasonal systems must demonstrate completion of a Division approved start-up procedure, which may include a requirement for start-up sampling prior to serving water to the public.

7.4.6.1.4.2 The Division may exempt any seasonal system from some or all of the requirements for seasonal systems if the entire distribution system remains pressurized during the entire period that the system is not operating.

7.4.6.2 Routine monitoring frequency for total coliforms. Surface water or ground water under the direct influence of surface water systems of this part (including consecutive systems) must monitor monthly. Systems may not reduce monitoring.

7.4.6.3 Unfiltered subpart H systems. In accordance with subsection 17.1 a surface water or ground water under the direct influence of surface water system that does not practice filtration shall be prohibited.

7.4.7 Routine monitoring requirements for public water systems serving more than 1,000 people.

7.4.7.1 General.

7.4.7.1.1 The provisions of this section apply to public water systems serving more than 1,000 persons.

7.4.7.1.2 Following any total coliform positive sample taken under the provisions of this section, systems must comply with the repeat monitoring requirements and E. coli analytical requirements in subsection 7.4.8.

7.4.7.1.3 Once all monitoring required by this section and subsection 7.4.8 for a calendar month has been completed, systems must determine whether any coliform treatment technique triggers specified in subsection 7.4.9 have been exceeded. If any trigger has been exceeded, systems must complete assessments as required by subsection 7.4.9.

7.4.7.1.4 Seasonal systems.

7.4.7.1.4.1 Beginning January 1, 2016, all seasonal systems must demonstrate completion of a Division approved start-up procedure, which may include a requirement for start-up sampling prior to serving water to the public.

7.4.7.1.4.2 The Division may exempt any seasonal system from some or all of the requirements for seasonal systems if the entire distribution system remains pressurized during the entire period that the system is not operating.

7.4.7.2 Monitoring frequency for total coliforms. The monitoring frequency for total coliforms is based on the population served by the system, as follows:

Total coliform monitoring frequency for public water systems serving more than 1,000 people

Population served	Minimum number of samples per month
1,001 to 2,500	2
2,501 to 3,300	3
3,301 to 4,100	4
4,101 to 4,900	5
4,901 to 5,800	6
5,801 to 6,700	7
6,701 to 7,600	8
7,601 to 8,500	9
8,501 to 12,900	10
12,901 to 17,200	15
17,201 to 21,500	20
21,501 to 25,000	25
25,001 to 33,000	30
33,001 to 41,000	40
41,001 to 50,000	50
50,001 to 59,000	60
59,001 to 70,000	70
70,001 to 83,000	80
83,001 to 96,000	90
96,001 to 130,000	100
130,001 to 220,000	120
220,001 to 320,000	150
320,001 to 450,000	180
450,001 to 600,000	210
600,001 to 780,000	240
780,001 to 90,000	270
970,001 to 1,230,000	300
1,230,001 to 1,520,000	330
1,520,001 to 1,850,000	360
1,850,001 to 2,270,000	390
2,270,001 to 3,020,000	420
3,020,001 to 3,960,000	450
3,960,001 or more	480

7.4.7.3 Unfiltered subpart H systems. In accordance with subsection 16.1 a surface water or ground water under the direct influence of surface water system that does not practice filtration shall be prohibited.

7.4.7.4 Reduced monitoring. Systems may not reduce monitoring, except for non-community water systems using only ground water (and not ground water under the direct influence of surface water) serving 1,000 or fewer people in some months and more than 1,000 persons in other months. In months when more than 1,000 persons are served, the systems must monitor at the frequency specified in subsection 7.4.7.2. In months when 1,000 or fewer people are served, the Division may reduce the monitoring frequency, in writing, to a frequency allowed under subsection 7.4.4 for a similarly situated system that always serves 1,000 or fewer people, taking into account the provisions in subsections 7.4.4.5 through 7.4.4.7.

7.4.8 Repeat monitoring and E. coli requirements.

7.4.8.1 Repeat monitoring.

7.4.8.1.1 If a sample taken under subsections 7.4.4 through 7.4.7 is total coliform-positive, the system must collect a set of repeat samples within 24 hours of being notified of the positive result. The system must collect no fewer than three repeat samples for each total coliform-positive sample found. The Division may extend the 24-hour limit on a case-by-case basis if the system has a logistical problem in collecting the repeat samples within 24 hours that is beyond its control. Alternatively, the Division may implement criteria for the system to use in lieu of case-by-case extensions. In the case of an extension, the Division must specify how much time the system has to collect the repeat samples. The Division cannot waive the requirement for a system to collect repeat samples in subsections 7.4.8.1.1 through 7.4.8.1.3.

7.4.8.1.2 The system must collect all repeat samples on the same day, except that the Division may allow a system with a single service connection to collect the required set of repeat samples over a three-day period or to collect a larger volume repeat sample(s) in one or more sample containers of any size, as long as the total volume collected is at least 300 ml.

7.4.8.1.3 The system must collect an additional set of repeat samples in the manner specified in subsections 7.4.8.1.1 through 7.4.8.1.3 if one or more repeat samples in the current set of repeat samples is total coliform positive. The system must collect the additional set of repeat samples within 24 hours of being notified of the positive result, unless the Division extends the limit as provided in subsection 7.4.8.1.1. The system must continue to collect additional sets of repeat samples until either total coliforms are not detected in one complete set of repeat samples or the system determines that a coliform treatment technique trigger specified in subsection 7.4.9.1 has been exceeded as a result of a repeat sample being total coliform-positive and notifies the Division. If a trigger identified in subsection 7.4.9 is exceeded as a result of a routine sample being total coliform positive, systems are required to conduct only one round of repeat monitoring for each total coliform positive routine sample.

7.4.8.1.4 After a system collects a routine sample and before it learns the results of the analysis of that sample, if it collects another routine sample(s) from within five adjacent service connections of the initial sample, and the initial sample, after analysis, is found to contain total coliforms, then the system may count the subsequent sample(s) as a repeat sample instead of as a routine sample.

7.4.8.1.5 Results of all routine and repeat samples taken under subsections 7.4.4 through 7.4.8 not invalidated by the Division must be used to determine whether a coliform treatment technique trigger specified in subsection 7.4.9 has been exceeded.

7.4.8.2Escherichia coli (E. coli) testing.

7.4.8.2.1 If any routine or repeat sample is total coliform-positive, the system must analyze that total coliform-positive culture medium to determine if E. coli are present. If E. coli are present, the system must notify the Division by the end of the day when the system is notified of the test result, unless the system is notified of the result after the Division office is closed and the Division does not have either an after-hours phone line or an alternative notification procedure, in which case the system must notify the Division before the end of the next business day.

7.4.8.2.2 The Division has the discretion to allow a system, on a case-by-case basis, to forgo E. coli testing on a total coliform-positive sample if that system assumes that the total coliform-positive sample is E. coli-positive. Accordingly, the system must notify the Division as specified in subsection 7.4.8.2.1 of this section and the provisions of subsection 7.2.1.1.3 apply.

7.4.9 Coliform treatment technique triggers and assessment requirements for protection against potential fecal contamination.

7.4.9.1 Treatment technique triggers. Systems must conduct assessments in accordance with subsection 7.4.9.2 after exceeding treatment technique triggers in subsections 7.4.9.1.1 and 7.4.9.1.2.

7.4.9.1.1 Level 1 treatment technique triggers.

7.4.9.1.1.1 For systems taking 40 or more samples per month, the system exceeds 5.0% total coliform-positive samples for the month.

7.4.9.1.1.2 For systems taking fewer than 40 samples per month, the system has two or more total coliform-positive samples in the same month.

7.4.9.1.1.3 The system fails to take every required repeat sample after any single total coliform-positive sample.

7.4.9.1.2 Level 2 treatment technique triggers.

7.4.9.1.2.1 An E. coli MCL violation, as specified in subsection 7.4.10.1.

7.4.9.1.2.2 A second Level 1 trigger as defined in subsection 7.4.9.1.1, within a rolling 12-month period, unless the Division has determined a likely reason that the samples that caused the first Level 1 treatment technique trigger were total coliform positive and has established that the system has corrected the problem.

7.4.9.1.2.3 For systems with approved annual monitoring, a Level 1 trigger in two consecutive years.

7.4.9.2 Requirements for assessments.

7.4.9.2.1 Systems must ensure that Level 1 and 2 assessments are conducted in order to identify the possible presence of sanitary defects and defects in distribution system coliform monitoring practices. Level 2 assessments must be conducted by parties approved by the Division.

7.4.9.2.2 When conducting assessments, systems must ensure that the assessor evaluates minimum elements that include review and identification of inadequacies in sample sites; sampling protocol; sample processing; atypical events that could affect distributed water quality or indicate that distributed water quality was impaired; changes in distribution system maintenance and operation that could affect distributed water quality (including water storage); source and treatment considerations that bear on distributed water quality, where appropriate (e.g., small ground water systems); and existing water quality monitoring data. The system must conduct the assessment consistent with any Division directives that tailor specific assessment elements with respect to the size and type of the system and the size, type, and characteristics of the distribution system.

7.4.9.2.3 Level 1 Assessments. A system must conduct a Level 1 assessment consistent with Division requirements if the system exceeds one of the treatment technique triggers in subsection 7.4.9.1.1.

7.4.9.2.3.1 The system must complete a Level 1 assessment as soon as practical after any trigger in subsection 7.4.9.1.1. In the completed assessment form, the system must describe sanitary defects detected, corrective actions completed, and a proposed timetable for any corrective actions not already completed. The assessment form may also note that no sanitary defects were identified. The system must submit the completed Level 1 assessment form to the Division within 30 days after the system learns that it has exceeded a trigger.

7.4.9.2.3.2 If the Division reviews the completed Level 1 assessment and determines that the assessment is not sufficient (including any proposed timetable for any corrective actions not already completed), the Division must consult with the system. If the Division requires revisions after consultation, the system must submit a revised assessment form to the Division on an agreed-upon schedule not to exceed 30 days from the date of the consultation.

7.4.9.2.3.3 Upon completion and submission of the assessment form by the system, the Division must determine if the system has identified a likely cause for the Level 1 trigger and, if so, establish that the system has corrected the problem, or has included a schedule acceptable to the Division for correcting the problem.

7.4.9.2.4 Level 2 Assessments. A system must ensure that a Level 2 assessment consistent with Division requirements is conducted if the system exceeds one of the treatment technique triggers in subsection 7.4.9.1.2. The system must comply with any expedited actions or additional actions required by the Division in the case of an E. coli MCL violation.

7.4.9.2.4.1 The system must ensure that a Level 2 assessment is completed by the Division or by a party approved by the Division as soon as practical after any trigger in subsection 7.4.9.1.2. The system must submit a completed Level 2 assessment form to the Division within 30 days after the system learns that it has exceeded a trigger. The assessment form must describe sanitary defects detected, corrective actions completed, and a proposed timetable for any corrective actions not already completed. The assessment form may also note that no sanitary defects were identified.

7.4.9.2.4.2 The system may conduct Level 2 assessments if the system has staff or management with the certification or qualifications specified by the Division unless otherwise directed by the Division.

7.4.9.2.4.3 If the Division reviews the completed Level 2 assessment and determines that the assessment is not sufficient (including any proposed timetable for any corrective actions not already completed), the Division must consult with the system. If the Division requires revisions after consultation, the system must submit a revised assessment form to the Division on an agreed-upon schedule not to exceed 30 days.

7.4.9.2.4.4 Upon completion and submission of the assessment form by the system, the Division must determine if the system has identified a likely cause for the Level 2 trigger and determine whether the system has corrected the problem, or has included a schedule acceptable to the Division for correcting the problem.

7.4.9.3 Corrective Action. Systems must correct sanitary defects found through either Level 1 or 2 assessments conducted under subsection 7.4.9.2. For corrections not completed by the time of submission of the assessment form, the system must complete the corrective action(s) in compliance with a timetable approved by the Division in consultation with the system. The system must notify the Division when each scheduled corrective action is completed.

7.4.9.4 Consultation. At any time during the assessment or corrective action phase, either the water system or the Division may request a consultation with the other party to determine the appropriate actions to be taken. The system may consult with the Division on all relevant information that may impact on its ability to comply with a requirement of this subpart, including the method of accomplishment, an appropriate timeframe, and other relevant information.

7.4.10 Violations.

7.4.10.1E. coli MCL Violation. A system is in violation of the MCL for E. coli when any of the conditions identified in subsections 7.4.10.1.1 through 7.4.10.1.4 occur.

7.4.10.1.1 The system has an E. coli-positive repeat sample following a total coliform positive routine sample.

7.4.10.1.2 The system has a total coliform positive repeat sample following an E. coli-positive routine sample.

7.4.10.1.3 The system fails to take all required repeat samples following an E. coli-positive routine sample.

7.4.10.1.4 The system fails to test for E. coli when any repeat sample tests positive for total coliform.

7.4.10.2 Treatment technique violation.

7.4.10.2.1 A treatment technique violation occurs when a system exceeds a treatment technique trigger specified in subsection 7.4.9.1 and then fails to conduct the required assessment or corrective actions within the timeframe specified in subsections 7.4.9.2 and 7.4.9.3.

7.4.10.2.2 A treatment technique violation occurs when a seasonal system fails to complete a Division-approved start-up procedure prior to serving water to the public.

7.4.10.3 Monitoring violations.

7.4.10.3.1 Failure to take every required routine or additional routine sample in a compliance period is a monitoring violation.

7.4.10.3.2 Failure to analyze for E. coli following a total coliform-positive routine sample is a monitoring violation.

7.4.10.4 Reporting violations.

7.4.10.4.1 Failure to submit a monitoring report or completed assessment form after a system properly conducts monitoring or assessment in a timely manner is a reporting violation.

7.4.10.4.2 Failure to notify the Division following an E. coli-positive sample as required by subsection 7.4.8.2.1 in a timely manner is a reporting violation.

7.4.10.4.3 Failure to submit certification of completion of Division-approved start-up procedure by a seasonal system is a reporting violation.

7.4.11 Reporting and recordkeeping.

7.4.11.1 Reporting.

7.4.11.1.1E. coli.

7.4.11.1.1.1 A system must notify the Division by the end of the day when the system learns of an E. coli MCL violation, unless the system learns of the violation after the Division office is closed and the Division does not have either an after-hours phone line or an alternative notification procedure, in which case the system must notify the Division before the end of the next business day, and notify the public in accordance with Section 4.0.

7.4.11.1.1.2 A system must notify the Division by the end of the day when the system is notified of an E. coli-positive routine sample, unless the system is notified of the result after the Division office is closed and the Division does not have either an after-hours phone line or an alternative notification procedure, in which case the system must notify the Division before the end of the next business day.

7.4.11.1.2 A system that has violated the treatment technique for coliforms in subsection 7.4.9 must report the violation to the Division no later than the end of the next business day after it learns of the violation, and notify the public in accordance with Section 4.0.

7.4.11.1.3 A system required to conduct an assessment under the provisions of subsection 7.4.9 must submit the assessment report within 30 days. The system must notify the Division in accordance with subsection 7.4.9.3 when each scheduled corrective action is completed for corrections not completed by the time of submission of the assessment form.

7.4.11.1.4 A system that has failed to comply with a coliform monitoring requirement must report the monitoring violation to the Division within 10 days after the system discovers the violation, and notify the public in accordance with Section 4.0.

7.4.11.1.5 A seasonal system must certify, prior to serving water to the public, that it has complied with the Division-approved start-up procedure.

7.4.11.2 Recordkeeping.

7.4.11.2.1 The system must maintain any assessment form, regardless of who conducts the assessment, and documentation of corrective actions completed as a result of those assessments, or other available summary documentation of the sanitary defects and corrective actions taken under subsection 7.4.9 for Division review. This record must be maintained by the system for a period not less than five years after completion of the assessment or corrective action.

7.4.11.2.2 The system must maintain a record of any repeat sample taken that meets Division criteria for an extension of the 24-hour period for collecting repeat samples as provided for under subsection 7.4.8.1.1.

16 Del. Admin. Code § 4462-7.0

24 DE Reg. 794(2/1/2021)
24 DE Reg. 904( 4/1/2021) (Errata)