ut-20260915-R309-520: R309-520. Facility Design and Operation: Disinfection

1. Agency Information

Title catchline: Environmental Quality, Drinking Water Building: Multi Agency State Building Street address: 195 N 1950 W City, state: Salt Lake City, UT 84116 Mailing address: PO Box 144830 City, state and zip: Salt Lake City, UT 84114-4830

2. Contact Persons

Name: Phone: Email: Rebecca Yoo 801-388-3594 ryoo@utah.gov Dani Zebelean 385-278-5110 dzebelean@utah.gov Sarah Page 385-272-5778 sepage@utah.gov Please address questions regarding information on this notice to the persons listed above. 58 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES

A. Rule or section catchline:

R309-520. Facility Design and Operation: Disinfection

B. Purpose of the new rule or reason for the change:

The Division of Drinking Water (division or DDW), through regular use and review of this rule, determined that this rule required updates. The division proposes to make changes to Rule R309-520 to make it easier to navigate, consolidate related sections from other rules, reflect current standard practices, clarify ambiguous language, and strengthen requirements to better protect public health.

C. Summary of the new rule or change:

The proposed amendments to Rule 309-520 reorganizes requirements by application scenario, consolidates relevant chemical addition provisions from Rule R309-525, and eliminates regulatory ambiguity by establishing explicit standards for submittals, pilot studies, and flow-powered pumps. Additionally, it strengthens public health protections by requiring backup power for uninterruptible disinfection systems, continuous chlorination throughout the distribution system, and the use of digital chlorine analyzers over subjective color strips to achieve accurate water quality monitoring. The following changes have financial implications. 1. Digital analyzers: Public Water Systems (PWS) currently relying on visual color-matching testing methods will incur a one-time capital expense to purchase digital chlorine analyzers to satisfy the updated rule. 2. Backup power for uninterruptible systems: PWS using non-gaseous chlorination systems to treat spring sources will incur capital costs for backup power systems. These financial impacts include the purchase of a generator, auxiliary equipment, and electrical labor for installation. 3. Secondary containment: PWS whose current secondary containment capacity is insufficient to hold the full volume of their chemical storage totes will incur costs to retrofit or purchase larger secondary containment. 4. Organization and explicit requirements: Clarifying and restructuring the rule requirements will streamline the project permitting process, reducing the time and administrative resources needed for communication between PWS staff, consultants, and regulatory staff. Additionally, clearer standards will decrease compliance violations resulting from improper disinfection practices, ultimately yielding cost savings for water systems. 5. Fiscal Information Provide an estimate and written explanation of the aggregate anticipated cost or savings to:

A. State budget:

The proposed rule revisions are estimated to yield $38,700 in annual savings through reduced enforcement, permitting, and technical consultation workloads. Because regulatory efficiencies cannot always be precisely measured in advance, the following cost savings reflect conservative estimates based on available workload data. 1. Prevented Level 2 (L2) Violations: $32,000 annually. Issuing a L2 Violation requires significant staff resources, due to field work, data review, team meetings, communications with the PWS, and administrative costs for preparing the letter. Each L2 costs DDW an estimated $3,200. Assuming the new rule prevents 10% of these incidents, staff time savings are estimated at $32,000 per year. 2. Prevented Boil Orders: $1,400 annually. Preparing and issuing a Boil Order incurs approximately $1,400 in staff administrative and technical assistance costs per order. Preventing one Boil Order per year, which is a 10% reduction, yields an annual savings of $1,400. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 59 NOTICES OF PROPOSED RULES 3. Streamlined Permitting Process: $2,000 annually. Standardized submittal requirements reduce staff review time for approximately 35 chlorinator projects per year, saving an initial $2,000 annually. As the total number of installed chlorinators grows each year, DDW staff time savings will increase over time. 4. Reduced TechnicalAssistance: $3,300 annually. Eliminating regulatory ambiguities reduces the back-and-forth communication required between DDW staff, PWS, and engineering consultants regarding compliance and disinfection remedies, saving an estimated $3,300 in staff time each year.

B. Local governments:

$0. The division is unable to determine how many and to what extent each public water system is operated exclusively by a local government, as the governing mechanism, financial decisions, and decision-making responsibilities are unique to each system. The division does not have data regarding the governance of PWS. For this reason, each system has been categorized as either a small or non-small business.

C. Small businesses ("small business" means a business employing 1-49 persons):

The division does not have data on the number of employees at each PWS. However, PWS serving less than 10,000 people were considered "small businesses" because most PWS serving less than 10,000 people are likely to employ less than 50 people. Costs: The costs are largely capital costs and were normalized with an anticipated equipment lifespan of 25 years. 1. Chlorine analyzers: $16,200 to $32,400 capital cost; normalized cost of $30 per year per system for 22 to 43 systems (based on assumption of 5 to 10% of systems lacking chlorine analyzers). 2. Backup power for uninterruptible systems: $38,000 to $152,000 capital cost; normalized cost of $20 to $80 per year per system for 76 systems; average cost of $48 per year per system for 76 systems. 3. Secondary containment: $34,300 capital cost; normalized cost of $6 per year per system for 165 systems that use liquid chlorine. Savings: While the overall savings to PWS are unquantifiable, this rule updates provide direct financial benefits by preventing costly compliance violations, emergency boil orders, and project review delays. Streamlining permitting submittals and eliminating regulatory confusion lowers overall administrative and consultant overhead for PWS.

D. Non-small businesses ("non-small business" means a business employing 50 or more persons):

The division does not have data on the number of employees at each PWS. However, PWS serving 10,000 or more people were considered "non-small businesses" because many PWS serving 10,000 people or more are likely to employ 50 or more people. Costs: The costs are largely capital costs and were normalized with an anticipated equipment lifespan of 25 years.

1. Chlorine analyzers: $0, based on assumption that all systems that lack chlorine analyzers are small systems.

2. Backup power for uninterruptible systems: $8,300 to $33,000 capital cost; normalized cost of $20 to $80 per year per system for 17 systems; average cost of $48 per year per system for 17 systems. 3. Secondary containment: $101,000 capital cost; normalized cost of $60 per year for 48 systems that use liquid chlorine. Savings: While the overall savings to PWS are unquantifiable, this rule updates provide direct financial benefits by preventing costly compliance violations, emergency boil orders, and project review delays. Streamlining permitting submittals and eliminating regulatory confusion lowers overall administrative and consultant overhead for PWS. 60 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES E. Persons other than small businesses, non-small businesses, state, or local government entities ("person" means any individual, partnership, corporation, association, governmental entity, or public or private organization of any character other than an agency): While the overall economic value to the population served by the PWS is unquantifiable, ensuring a safe and continuous drinking water supply provides significant financial benefits. Reliable disinfection prevents waterborne illnesses and the associated healthcare costs, missed workdays, and lost household income. Furthermore, protecting public health ensures business continuity, safeguarding individual livelihoods and driving the long-term economic stability and viability of local communities.

F. Compliance costs for affected persons:

The relevant cost for each system varies according to the needs and context of each system. The cost of each type of compliance change is described below. 1. Chlorine analyzers: $750 capital cost per system; normalized cost of $30 per year per system for 22 to 43 systems (based on assumption of 5-10% of systems lacking chlorine analyzers). 2. Backup power for uninterruptible systems: $500 to $2,000 capital cost per system; normalized cost of $20 to $80 per year per system for 76 systems; average cost of $48 per year per system for 76 systems. 3. Secondary containment: $150 to $1,500 capital cost per system; normalized cost of $6 per year per system for 165 systems that use liquid chlorine. Savings: While the overall savings to Public Water Systems are unquantifiable, this rule updates provide direct financial benefits by preventing costly compliance violations, emergency boil orders, and project review delays. Streamlining permitting submittals and eliminating regulatory confusion lowers overall administrative and consultant overhead for PWS. 6. Regulatory Impact Summary Table Enter the cost or savings in the relevant cell. If there is no cost or savings, enter, "$0." If a cost or savings is inestimable, enter, "inestimable." Fiscal Cost FY2027 FY2028 FY2029 FY2030 FY2031 State Budget $0 $0 $0 $0 $0 Local Governments $0 $0 $0 $0 $0 Small Businesses $88,500 to $0 $0 $0 $0 $218,700 Non-Small Businesses $109,300 to $0 $0 $0 $0 $134,000 Other Persons $0 $0 $0 $0 $0 Total Fiscal Cost $197,800 to $0 $0 $0 $0 $352,700 Fiscal Benefits FY2027 FY2028 FY2029 FY2030 FY2031 State Budget $38,700 $38,700 $38,700 $38,700 $38,700 Local Governments $0 $0 $0 $0 $0 Small Businesses Inestimable Inestimable Inestimable Inestimable Inestimable Non-Small Businesses Inestimable Inestimable Inestimable Inestimable Inestimable Other Persons Inestimable Inestimable Inestimable Inestimable Inestimable Total Fiscal Benefits Inestimable Inestimable Inestimable Inestimable Inestimable Net Fiscal Benefits Inestimable Inestimable Inestimable Inestimable Inestimable UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 61 NOTICES OF PROPOSED RULES 7. Regulatory Impact Analysis Approval The Commissioner of the Department of Environmental Quality, Tim Davis, has reviewed and approved this regulatory impact analysis. 8. Family Impact Information

A. The agency has considered this rule's impact on family health, stability, and formation: ☒

9. Citation Information Provide citations to the statutory authority for the rule. If there is also a federal requirement for the rule, provide a citation to that requirement: Section 19-4-104 10. Incorporation by Reference Information Incorporation by Reference: A. This rule adds or updates the following title of material incorporated by reference (a copy of the material incorporated by reference must be submitted to the Office of Administrative Rules. If none, leave blank): Official Title of Materials Incorporated Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced (from title page) Surface Water Treatment Rule Publisher United States Environmental Protection Agency Issue Date November 2006 B. This rule adds or updates the following title of material incorporated by reference (a copy of the material incorporated by reference must be submitted to the Office of Administrative Rules. If none, leave blank): Official Title of Materials Incorporated InnovativeApproaches for Validation of Ultraviolet Disinfection Reactors for Drinking (from title page) Water Systems Publisher United States Environmental Protection Agency Issue Date April 2020 11. Public Notice Information The public may submit written or oral comments to the agency identified in box 1.

A. Comments will be accepted until: 10/15/2026

12. Effective Date Information This rule change MAY become effective on: 11/03/2026 (NOTE: This is the date the agency anticipates making the filing effective. It is NOT the effective date) 13. Agency Authorization Information Agency head or Nathan Lunstad, Director Date: 08/11/2026 designee and title: R309. Environmental Quality, Drinking Water. R309-520. Facility Design and Operation: Disinfection. [R309-520-1. Purpose. This rule specifies requirements for facilities that disinfect public drinking water. It is to be applied in conjunction with rules R309- 500throughR309-550,DrinkingWaterFacilityConstruction,Design,andOperation. Collectively,theseRulesgovernthedesign,construction, and operation and maintenance of public drinking water system facilities. These Rules are intended to assure that such facilities are reliably capable of supplying adequate quantities of water that consistently meet applicable drinking water quality requirements and do no harm to general public health. 62 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES R309-520-2. Authority. This rule is promulgated by the Drinking Water Board as authorized by Title 19, Environmental Quality Code, Chapter 4, Safe Drinking Water Act, Subsection 104(1)(a)(ii) of the Utah Code and in accordance with Title 63G, Chapter 3 of the same, known as the Administrative RulemakingAct. R309-520-3. Definitions. Definitions for certain terms used in this rule are given in R309-110 but may be further clarified herein. R309-520-4. Primary Disinfectants. Primary disinfection is the means to provide adequate levels of inactivation of pathogenic microorganisms within the treatment process. The effectiveness of chemical disinfectants is measured as CT, a function of disinfectant residual and contact time. The effectiveness of UV disinfection is determined through validation testing of each model and specific configuration of UV reactor proposed in the design, as described in R309-520-8. Four disinfectants: chlorine, ozone, ultraviolet light, and chlorine dioxide are approved as primary disinfectants of drinking water. R309-520-5. Secondary Disinfectants. Secondary disinfection provides an adequate disinfectant residual in the distribution system to maintain the quality of treated water by controlling microbiological contamination. Secondary chemical disinfection is achieved by maintaining a detectable disinfectant residual throughout the distribution system. Allowable secondary disinfectants are chlorine and chloramine. R309-520-6. General. (1) Continuous Disinfection. (a) Continuousdisinfectionisrequiredofallgroundwatersourcesthatdonototherwisecontinuouslymeetmicrobiologicalstandards. Intermittent or batch disinfection, such as adding hypochlorite tablets or concentrated hypochlorite solution to a tank, is not acceptable for ongoing operation if continuous disinfection is required. (b) Disinfection is not an acceptable remedy to physical deficiencies or sources susceptible to surface water influence. Disinfection shall not be used to mask ongoing contamination and shall not be used as a substitute for correcting deficiencies. (c) Where continuous disinfection is required, the design shall provide a means to isolate or service the disinfection equipment without allowing untreated water to enter the distribution system. If the untreated water is to be discharged, it shall not cause environmental or property damage. (2) ANSI/NSF Standard 60 Certification. Allchemicalsaddedtodrinkingwater,includingchlorine(i.e.,gas,hypochloritesolution,hypochloritetablets,granules,andpowder), chloramines, and chemicals used to generate hypochlorite solutions and chlorine dioxide, shall be certified as complying with ANSI/NSF Standard 60, Drinking Water Treatment Chemicals. (3) Required Disinfection. (a) Surface water, or groundwater underthe directinfluence of surfacewater, shall be filtered byconventional surfacewatertreatment or alternative surface water treatment methods and disinfected to meet the requirements of R309-200-7. (b) Where microbiologicaltreatmentisrequiredfor a ground watersource thatisnotundertheinfluence ofsurface water, disinfection without filtration may be considered adequate. (4) Point ofApplication and CT. A combination of disinfectant residual and contact time is defined as disinfection CT in R309-110-4. The following requirements apply to disinfectant point of application and CT: (a) Consideration shall be given to the contact time of the disinfectant in water with relation to pH, ammonia, taste-producing substances, temperature, biological quality, and other pertinent factors. (b) Where possible, the design shall minimize the formation of disinfection byproducts. (c) Treatment of ground water sources shall provide sufficient CT to achieve a minimum of 4-log virus inactivation and/or removal. (d) Point of application of disinfectants shall be at a location that will achieve the required disinfection CT prior to the first service connection. (5) Site Selection. Disinfection installations shall be sited to permit convenient access during the operation period. These installations shall be sited with due consideration of possible danger to nearby population and of possible jeopardy from seismic fault zones. R309-520-7. Chlorine. (1) General Requirements for all Chlorination Installations. (a) Chemical Types. Disinfection by chlorination shall be accomplished by gaseous chlorine or hypochlorite solutions. Hypochlorite solutions can be purchased, generated on site, or prepared by dissolving solids. (b) Feed Equipment. Solution-feed gas type chlorinators, direct-feed gas type chlorinators or hypochlorite liquid feeders of a positive displacement type shall be provided. Solution-feed gas type chlorinators are preferred. Use caution when selecting direct-feed gas type chlorinators. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 63 NOTICES OF PROPOSED RULES (c) Chlorine Feed Capacity. (i) The capacity of the chlorine feed equipment shall be sized to provide at least 2 mg/L during peak demand. (ii) The feed equipment shall operate accurately over the design feeding range. (iii) The feed equipment shall be designed to maintain a detectable residual at all times, at all points within the intended area in the distribution system. (d) Automatic Proportioning. Automatic proportioning chlorinators shall be required where the rate of flow of the water to be treated or chlorine demand of the water to be treated is not reasonably constant. (e) Injector, Eductor, or Diffuser. (i) Chlorine shall be added at a point that allows rapid and thorough mixing. The center of a pipeline is the preferred application point. (ii) The selection of equipment shall consider the point of application, the quantity of chlorine to be added, the size and flow of the chlorine solution line, the back pressure of the to-be-treated water flow, and the equipment operating pressure. (iii) A suitable strainer to prevent small debris from clogging chlorine feed equipment shall be provided. Provision for flushing the strainer is required. (f) Point ofApplication for Surface Water. The design of plants treating surface water or ground water under the direct influence of surface water shall make provisions to add chlorine at various process points as needed. (g) Minimization of Chlorinated Overflow. The design shall minimize the release of chlorinated water into the environment, for example, the discharge of chlorinated water from tank overflows. Such releases must comply with rules of Division of Water Quality that pertain to discharge of pollution. (h) Prevention of Cross Connections. (i) The design shall prevent contamination of the treated water supply by make-up water of lesser quality. (ii) All chlorine solution make-up water shall be at least of equal quality to the water receiving the chlorine solution. At surface water treatment facilities, pre-chlorination and post-chlorination processes shall be independent to prevent cross connections where pre- chlorination make-up water is not finished water. (i) Flow Measurement. The design of the chlorination system shall provide a means to measure the flow rate of treated water as a basis for dosing. (j) Residual Testing Equipment. The water system shall have chlorine residual test equipment capable of measuring residuals to the nearest 0.1 mg/L in the range below 0.5 mg/L, to the nearest 0.3 mg/L between 0.5 mg/L and 1.0 mg/L and to the nearest 0.5 mg/L above 1.0 mg/L. (k) Standby and Backup Equipment. (i) Aspare parts kit shall be provided and maintained for all chlorinators to repair parts subject to wear and breakage. If there could be a large difference in feed rates between routine and emergency dosages, multiple gas metering tubes shall be provided, at least one for each dose range, to assure accurate control of the chlorine feed under both routine and emergency conditions. (ii) Where chlorination is required for disinfection of a water supply, standby equipment of sufficient capacity shall be available to replace the largest unit in the event of its failure. (iii) Standby power shall be available, during power outages, for operation of chlorinators where disinfection of the water supply is required unless operation of the chlorinator does not require power. (l) Heating, Lighting, Ventilation. Chlorinator buildings shall be heated, lighted and ventilated as necessary to assure proper operation of the equipment and safety of the operators. (m) Incompatible Chemicals. The design shall ensure that incompatible chemicals that may damage or deteriorate chlorination facilities are stored separately from chlorination equipment and chemicals. (2) Additional Requirements for Gas Chlorinators. (a) Automatic Switch over. Automatic Switch over of chlorine cylinders shall be provided if continuous disinfection is required. (b) Gas Scrubbers. One-ton chlorine cylinder operating areas shall be equipped with a gas scrubber per the International Fire Code capable of treating the release of chlorine gas from the largest single cylinder at its maximum flow rate. Furthermore, local toxic gas ordinances shall be complied with if they exist. (c) Heat. The design of the chlorination room shall assure that the temperature in the room will not fall below 32 degrees F or the temperature required for proper operation of the chlorinator, whichever is greater. (d) Ventilation. (i) Chlorination equipment rooms which contain chlorine cylinders, tanks, equipment and gaseous chlorine lines under pressure shall have at least one exhaust fan. (ii) Chlorine room exhaust fan(s), when operating, shall provide at least one complete room air change per minute. (iii) Chlorine room exhaust fan(s) shall take suction inside the chlorine room near the floor, as far as practical from the door and air inlet, and discharge air outside of the building away from air inlets. (iv) Chlorine room air inlets shall be through wall louvers near the ceiling. 64 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (v) Separate switches for the chlorine room fans and lights shall be located near the entrance to the room and shall be protected from vandalism. The switches shall be located outside the chlorine room if housed in a water treatment plant. (vi) The ventilation system for one-ton chlorine cylinder operating areas shall be designed to operate independently from the ventilation system for the rest of the treatment plant. One-ton chlorine cylinder operating areas shall be designed to maintain negative pressure per the International Fire Code. (e) Chlorine Vent Line. The chlorine vent line shall discharge outside, above grade, at a point least susceptible to vandalism, and shall have the end covered with a No. 14 mesh non-corrodible screen. (f) Housing. (i) Housing shall be provided for chlorination equipment and storage to ensure proper function and security. (ii) Chlorine cylinders shall not be stored in direct sunlight or exposed to excessive heat. (g) Housing at Water Treatment Plants. A separate chlorine room, for chlorine cylinders and feed equipment, shall be provided at all water treatment plants with multiple processes and operating areas. (i) The chlorine room shall have shatter resistant inspection window(s) installed in an interior wall preferably located so that an operator may read the weighing scales without entering the chlorine room. (ii) All openings between the chlorine room and the remainder of the plant shall be sealed. (iii) Outward-opening doors shall be equipped with panic bars to allow rapid exit. (iv) Floor drains are discouraged but, where provided, shall discharge to the outside of the building and shall not be connected to other internal or external drain systems. (v) Chlorine feed lines shall not carry pressurized chlorine gas beyond the chlorine room. Only vacuum lines may be routed to other portions of the building outside the chlorine room. Any openings for these lines must be adequately sealed. (vi) The design of operating areas for one-ton cylinders shall allow full and empty cylinders to be stored in separate areas. (h) Cylinder Security. Chlorine cylinders shall be restrained in position to prevent upset. (i) Weighing Scales. Scales shall be provided for determining chlorine cylinder weight. Scales should be of a corrosion resistant material and should be placed in a location remote from any moisture. Scales shall be accurate enough to indicate loss of weight to the nearest one pound for 150 pound cylinders and to the nearest 10 pounds for one ton cylinders. (j) Pressure Gauges. Pressure gauges shall be provided on the inlet and outlet of each chlorine eductor. (k) Gas Masks. (i) Where chlorine gas in one-ton cylinders is handled, respiratory protection equipment, meeting the requirements of the National Institute for Occupational Safety and Health (NIOSH) shall be available and shall be stored at a convenient location, but not inside any room where chlorine is used or stored. The units shall use compressed air, have at least a 30 minute capacity, and be compatible with units used by the fire department responsible for the plant. (ii) Where 150 pound chlorine cylinders are used, a respirator recommended by the National Institute for Occupational Safety and Health must be available. (l) Chlorine Leak Detection and Repair. (i) Abottle ofAmmonium Hydroxide, 56% ammonia solution, shall be available for chlorine leak detection. (ii) Where one-ton cylinders are used, a leak repair kit approved by the Chlorine Institute shall be provided. (iii) Continuous chlorine leak detection equipment is required for one-ton cylinders. (iv) Where a continuous leak detector is provided, it shall be equipped with both an audible alarm and a warning light to ensure operator safety. (3) Additional Requirements for Hypochlorite Systems. (a) General Requirements. (i) Emergency Eyewash and Safety Showers. Emergency eyewash stations and safety showers shall be provided at all hypochlorite installations where concentrated hypochlorite solutions, containing 5% or greater available chlorine by volume, are handled in containers greater than 55 gallons. Where hypochlorite solutions are used at remote locations or in quantities of 55 gallons or less on site, safety showers are not required and alternative emergency eyewash may be provided. (ii) Storage of Liquid Hypochlorite to Prevent Decay. Storage and injection areas shall be designed to minimize the decay in strength of concentrated hypochlorite solutions from excessive heat or direct sunlight. (iii) Feed Equipment - ChemicalAddition. Hypochlorite feed equipment shall generally conform with R309-525-11, ChemicalAddition. (iv) Feed Equipment - Certification. The hypochlorite feed equipment for drinking water treatment shall be certified to meetANSI/NSF Standard 61. (b) Concentrated Hypochlorite Solutions. The water system shall provide an operational means to avoid the injection of significantly decayed hypochlorite solutions, for example by keeping records on site of the delivery date of the hypochlorite solution. (c) On-Site Generation of Hypochlorite Solutions. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 65 NOTICES OF PROPOSED RULES (i) The on-site hypochlorite generation systems used for drinking water treatment shall be certified as meeting the NSF/ANSI Standard 61. (ii) Manufacturer recommendations for safety with respect to equipment and electrical power shall be followed. (iii) The make-up water used in on-site generation shall be of drinking water quality. (iv) The hydrogen gas generated in the electrolytic cell of the on-site generation system shall be vented upward to the outside of the building in a dedicated, unobstructed line. (d) Hypochlorite Tablets. (i) Before selecting a hypochlorite tablet disinfection process, water hardness, solubility of hypochlorite tablets, water temperature, and other water quality factors shall be taken into consideration. (ii) The hypochlorite dissolution equipment for drinking water treatment shall be certified as meeting theANSI/NSF Standard 61. (iii) The design shall allow the hypochlorite tablets to be stored in accordance with the manufacturer's safety guidelines and in their original containers in a cool, dry, well-ventilated area. The hypochlorite tablets shall not be stored near combustible materials or acids to avoid fire or the release of toxic gases. R309-520-8. Ultraviolet Light. (1) General Requirements. This rule shall apply to the public drinking water systems that use ultraviolet (UV) disinfection for inactivation of Cryptosporidium, Giardia, and virus. The Director may reduce the requirements of monitoring and reporting on a case by case basis for the water systems that use UV as ancillary means of disinfection and do not claim credit for UV disinfection or for water systems using UV without a SCADAsystem and treating less than 30 gallons per minute. Terminology used in this rule is based on the definitions in the EPA Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule (2006 Final UVDGM). (a) Water systems using surface water or ground water under the influence of surface water shall not use UV as the sole means of disinfection. For these types of water systems, at least one alternative primary disinfectant must be used for virus disinfection, and a secondary disinfectant shall be provided to maintain a disinfectant residual in the distribution system. (b) The following requirements apply to the water systems that wish to receive credit for UV disinfection: (i) The water system shall submit a UV plan which clearly identifies the dose monitoring strategy, such as the UV intensity setpoint approach, the calculated dose approach or an alternative approach. (ii) The water system shall identify the goals for the UV facility as part of a comprehensive disinfection strategy, including target pathogens, target log inactivation, and corresponding required UV dose per Table 215-5 in R309-215-15(19)(d). (iii) The water system shall submit a UV reactor validation report in accordance with R309-520-8(2), to the Director for review prior to installation of UV facility. (iv) The water system must demonstrate that the reactor is delivering the required UV dose using a validated dose monitoring system and continue to comply with the monitoring and reporting requirements specified in R309-215-15(19) and (20). (2) Validation Testing. The Director may accept a validation report that was conducted based on the 2003 draft UVDisinfection Guidance Manual on a case- by-case basis. (a) Each model and specific configuration of UV reactor must undergo off-site, full-scale validation testing by an independent third party test facility prior to being approved for use.The validation testing shall be conducted in qualified test facilities that are deemed acceptable by NSF, EPA, or the Director. (b) Validation testing results shall provide data, including calculations and tables or graphical plots, on dose delivery by the UV reactor under design conditions of flow rate, UVtransmittance (UVT), UV intensity, lamp status, power ballast setting, as well as consideration of lamp aging and lamp fouling. The validation report shall demonstrate that the monitoring algorithm is valid over the range expected with the application. The data is used to define the dose monitoring algorithm for the UV reactor and the operating conditions that can be monitored by a utility to ensure that the UV dose required for a given pathogen inactivation credit is delivered. (c) The UV reactor validation report shall include: (i) Description of the reactor and validation test set-up, including general arrangement and layout drawings of the reactor and validation test piping arrangement. (ii) Description of the methods used to empirically validate the reactor. (iii) Descriptionof the dosemonitoringequation for the reactortoachievethetarget pathogeninactivationcreditandrelatedgraphical plots showing how the equation was derived from measured doses obtained through validation testing under varying test conditions. (iv) Range of validated conditions for flow, UVT, UV dose, and lamp status. (v) Description and rationale for selecting the challenge organism used in validation testing, and analysis to define operating dose for pathogen inactivation credit. (vi) Tabulated data, analysis, and quality assurance/quality control (QA/QC) measures during validation testing. (vii) Alicensedprofessional engineer's third party oversight certification indicating that the testing and data analyses in the validation report are conducted in a technically sound manner and without bias. (viii) The validation report shall be accompanied with completed Checklists 5.1 through 5.5 included in the EPA Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule (2006 Final UVDGM). (3) Design Criteria 66 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (a) Awater system considering UV disinfection shall gather sufficient water quality data prior to design. The water samples shall be representative of the source water to be treated by the UV facility. Frequent testing may be required if significant variation or seasonal trending in water quality is expected. (b) The following water quality parameters shall be considered in UV facility planning: (i) UV Transmittance or UVAbsorbance (ii) Calcium (iii) Alkalinity (iv) Hardness (v) Iron (vi) Manganese (vii) Turbidity (viii) pH (ix) Oxidation-Reduction Potential (ORP) (x) Particle content and algae (c) The design flow rate and UVT used to size the UV system shall be selected to provide the required dose at least 95 percent of the time, accounting for seasonal variations of flow and UVT combinations. Specifying a matrix of flow and UVT conditions for the UV reactors may be necessary. (d) The water system may consider increasing the delivered dose beyond the required UV dose listed in Table 215-5 in R309-215- 15(19)(d) to provide flexibility and conservatism. (e) UV reactor inlet and outlet configurations shall meet the validated hydraulic distribution of flow conditions or be more hydraulically conservative. This can be achieved using one of the following approaches: (i) The inlet and outlet configuration shall meet one of the conditions specified in Section 3.6.2 of the 2006 Final UVDGM. (ii) Computational fluid dynamics (CFD)-based modeling may be used to demonstrate that the given conditions of inlet and outlet piping with the UV installation provides equal or greater dose delivery. The CFD modeling shall be conducted at the minimum and maximum values of the validated range of flow, UVT, and lamp status. (f) The UV disinfection system shall be capable of applying the required design dose with a failed or out-of-service reactor. The design shall account for an on-line backup UV reactor or an operating scheme to apply the design dose with one reactor out of service. (g) It shall be possible to isolate each reactor for maintenance. (h) Signals and alarms shall be provided for the operation of the UV facility for the parameters necessary for dose monitoring algorithm, such as low UV dose, high flow rate, low UVT, UVT monitoring failure, UV sensor failure, off specification event, Ground Fault Interrupt (GFI), high water temperature, and low water level. (i) All materials used in constructing or coating the UV reactors that come in contact with water shall be certified NSF Standard 61 - Drinking Water System Components - Health Effects. (j) Any chemicals used in the cleaning of the UV reactor components in contact with the drinking water such as quartz sleeves shall be certified as meeting theANSI/NSF Standard 60 - Drinking Water Treatment Chemicals - Health Effects. (k) A flow or time delay shall be provided to permit a sufficient time for tube warm-up, per manufacturer recommendations, before water flows from the unit upon start up.The flow or time delay shall be included in the design so they do not result in excessive off specification conditions. (l) To ensure a continuous supply of power, a backup power supply of sufficient capacity shall be provided for the UV disinfection system. If power quality problems, such as frequent power interruptions or brownouts, or remote location with unknown power quality, are anticipated, power conditioning equipment, such as uninterruptible power supply (UPS), shall be included in the design. (m) The design shall include a redundant disinfection mechanism that will apply an approved primary disinfectant to achieve the CT or log removal/inactivation required for compliance if a UV facility is off specification or offline within a maximum response time of 15 minutes. One example of such response is to shut down the off- specification UV train and either bring a parallel UV train on line or initiate a back-up primary disinfection system within 15 minutes, so the continuous duration of an off- specification event is limited to no more than 15 minutes. (n) UV disinfection units rated at 30 gallons per minute or less shall be certified as meeting theANSI/NSF Standard 55, ClassA, or other equivalent or more stringent validation or certification standards that are deemed acceptable by the Director. (o) The dose monitoring approach used for UV facility must be reviewed and accepted by the Director. Typically the calculated dose approach is suitable for large systems or systems with significant flow variation, and the UV intensity setpoint approach is for small systems or systems with fixed flow rate. The dose monitoring approaches need to be consistent with the guidelines stated in the 2006 Final UVDGM. (p) If Programmable Logic Controller (PLC) or SCADA interface is used for UV reactor's process control, the programming shall be in accordance with the validated dose monitoring algorithm and the validated conditions. The algorithm shall use inputs of flow, UV intensity sensor readings, lamps status, and/or UVT equal to or more conservative than values measured during the operation of the UV system. Ifthe measuredUVTisabove the validated range, themaximum validated UVTshall be used astheinput tothe dosealgorithm. Ifthe measured flow rate is below the validated range, the minimum validated flow rate shall be used as the input to the dose algorithm. If the dose algorithm uses relative lamp output determined from the UVintensity sensor readings as an input, the relative lamp output shall be based on the measured UVT, even if it exceeds the maximum validated UVT. (q) The UV reactor's PLC or microprocessor shall be programmed to record off specification events for the following conditions: (i) Delivered UV dose less than the required dose, (ii) Flow greater than the validated range, (iii) UVT less than the validated range, UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 67 NOTICES OF PROPOSED RULES (iv) Lamp status outside the validated range, (v) Failure of UV sensors, flow meters, or on-line UVT monitors used in the dose calculation. Laboratory measurements of UVT may be used temporarily in the program until the on-line UVT monitor is repaired. (4) Operation and Maintenance The operation and maintenance tasks and the frequency of performing them can be specific to the UV equipment installed. The water systems with approved UV installations should follow the manufacturer's recommendation or the operation and maintenance guidelines stated in Section 6.2 through 6.5 of the 2006 Final UVDGM. (a) Startup testing. (i) The UV reactor manufacturer must provide a site-specific operation and maintenance manual, which shall include the procedure for starting up and shutting down the UV treatment system. (ii) Provide schedules and performance standards for start-up testing and initial operation. Schedules shall include anticipated start- up date and proposed testing duration. Performance standards shall reference applicable regulations and specific equipment capabilities. (iii) Operators shall receive site-specific training on the operation of the UV disinfection system. (b) An incident plan shall be developed to address lamp breakage and release of mercury, response to alarms, power supply interruptions, activation of standby equipment, failure of systems, etc. (c) To verify that the UV reactors are operated within the validated limits, selected parameters shall be monitored. The routine operation and maintenance shall include the monitoring and calibration requirements listed in R309-215-15(19) and (20) and are in accordance with the monitoring and reporting protocol approved by the Director. For very small UVsystems, the Director may consider granting exception to allow reduced monitoring and reporting on a case-by-case basis. R309-520-9. Ozone. (1) General Requirements. (a) Ozone is approved as a primary disinfectant, but is not approved as a secondary disinfectant for the distribution system because of its rapid decomposition in aqueous solution. A different disinfectant approved for secondary disinfection must be used if a minimum disinfection residual is required in the distribution system. Ozone may also be used for taste and odor control, oxidation of inorganic and organic compounds and for enhanced performance of other water treatment processes such as microflocculation and filtration. Some of the requirements of this section may not be applicable if ozone is used only for reasons other than primary disinfection. (b) Pilot studies or bench scale studies shall be conducted for all surface waters unless there is sufficient data available from other studies performed on the same water source. The studies shall determine the initial ozone demand, the rate of ozone decay, the minimum and maximum ozone dosages for the range of water conditions for disinfection "CT" compliance, and the ozone dosage required for other desired benefits. Pilot studies or bench scale studies shall take into account the seasonal and other variations of the source water. Plans for pilot studies or bench scale studies shall be reviewed and accepted by the Director prior to commencement of the studies. (2) Ozone Generation. (a) The ozone system should be designed with backup capability such that required inactivation can be achieved with one generator out of service. (b) The ozone generators shall be housed in an enclosed temperature controlled building for protection. Adequate ventilation shall be provided in the building, and be capable of providing six or more air changes per hour when needed in case of an ozone leak. (c) The ozone generators shall be of the medium or high frequency type. (d) The power supply units for the ozone generators shall have a backup electrical power source, normally an emergency generator, or the system shall have an alternate primary disinfection system that may be used in case of an electrical power outage. (e) The ozone generators shall be water-cooled with a maximum increase in cooling water temperature of 10 degrees F (5.6 degrees C). If necessary, the cooling water should be treated to minimize corrosion, scaling, and microbiological fouling of the water side of the tubes. A closed-loop cooling water system may be used to assure proper water conditions are maintained. The power supply units to the ozone generators may also be water cooled. (f) The ozone generators shall comply with Section 3705 of Chapter 37, "Ozone Gas Generators," of the 2006 International Fire Code. (3) Ozone Generator Feed Gas. (a) Feed gas may be air, vaporized high purity liquid oxygen, or oxygen enriched air. Oxygen may be generated on-site or delivered in bulk. Oxygen-enriched air is typically generated on-site. (b) The design of the feed gas system must ensure that the maximum dew point of the feed gas of -76 degrees F (-60 degrees C) is not exceeded at any time. (c) Liquid Oxygen Feed Gas Systems. (i) Liquid oxygen storage tanks shall be sized to provide a minimum of a 7-day supply to the ozone generators at the maximum operating rate. (ii) There shall be two or more vaporizers to convert liquid oxygen to the gaseous form. Vaporizers must be capable of maintaining oxygen flow at the minimum design air temperature with one unit on standby. (iii) Liquid oxygen storage tanks and system shall comply with Chapters 40, "Oxidizers," of the 2006 International Fire Code. (d) Air or Oxygen EnrichedAir Feed Gas Systems. (i) There shall be two or more air compressors to supply air. The capacity of the compressors shall be such that the demand during maximum ozone production and for other compressed air uses at the treatment plant can be met when the largest compressor is out of service. 68 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (ii) Entrainment separators, refrigeration dryers, desiccant dryers, and filters shall be used as necessary to provide a sufficiently dried, dust-free, and oil-free feed gas to the ozone generators. Multiple units of this equipment shall be used so that the ozone generation is not interrupted in the event of a breakdown. (4) Ozone Contactors. (a) An ozone contactor shall consist of two or more chambers to provide for introduction of ozone into the water and contact time. In a water treatment plant, ozone may be introduced in the raw water, or ozone may be introduced later in the process, such as to settled water after solids have been removed. An ozone contactor must be a closed vessel that is kept under less than atmospheric pressure to prevent escape of ozone gas. The materials of construction must be ozone-resistant to prevent premature failure of the contactor. (b) Ozone gas may be injected into the water under positive pressure through bubble diffusers using porous-tube or dome diffusers. Alternatively, ozone gas may be injected into the water using side stream injection. This is where ozone gas is drawn into the side stream using negative pressure, which is generated in a pipe section with a venturi. (c) An ozone contactor shall be designed to achieve a minimum transfer efficiency of 85 percent. (d) Multiple sampling points shall be provided in an ozone contactor to enable sampling of treated water for purposes of determining an accurate measure of the concentration to be used in the "CT" disinfection calculation. (e) Arecommended minimum disinfection contact time is ten minutes. (f) Ozone contactors shall have provision for cleaning, maintenance, and drainage of the contactor. Each contactor chamber shall be equipped with an access hatchway or other means of entry. (g) An ozone contactor shall have an emergency off-gas pressure/vacuum relief system to prevent damage to the unit. (h) Asystem must be provided for worker safety at the end of the ozone contactor for compliance with OSHAstandards. Specifically, ozone levels in the gas space above treated water that has exited the contactor must not exceed the established OSHA8-hour exposure limit of 0.1 ppm. This system may be an ozone residual quenching system where a chemical is used to destroy remaining ozone in the water, or this system may be a monitoring system that provides sufficient time to lower the residual ozone level in the water by natural decay to an acceptable level. Any chemical used to quench residual ozone shall comply withANSI/NSF Standard 60. (5) Off-Gas Destruction Units. (a) A system for treating the final off-gas from each ozone contactor must be provided in order to meet safety standards. Systems using thermal destruction or catalytic destruction may be used. At least two units shall be provided which are each capable of handling the entire off-gas flow. (b) Exhaust blowers shall be provided in order to draw off-gas from the contactor into the destruction units. (c) Provisions must be made to drain water from condensation in the off-gas piping and to protect the destruction units and piping from moisture and other impurities that may cause damage. (d) The maximum allowable ozone concentration in the gas discharge from a destruction unit is 0.1 ppm by volume. Provisions may be made for temporary transient concentration spikes that may exceed this limit. (6) Piping and Connections. (a) Because ozone is a strong oxidant, consideration shall be given to piping materials used in ozone service. Generally, only low carbon 304L and 316L stainless steel should be used for ozone gas service. (b) Connections on piping used for ozone service should be welded where possible. Threaded connections should be avoided for ozone gas piping because of their tendency to leak. Connections with meters, valves, or other equipment should be made with flanged joints with ozone-resistant gaskets. (c) A positive-closing 90-degree turn isolation valve, or other equivalent means, shall be provided in the piping between an ozone generator and a contactor to prevent moisture from reaching the ozone generator during shutdowns. (7) Instrumentation and Monitoring. (a) Aflow meter shall be provided to measure the flow rate of the water being treated. Atemperature gauge or transmitter shall also be provided to measure the temperature of the water being treated. The pH shall also be measured to indicate changes in the water being treated. (b) An ozone gas analyzer, a flow meter, and a temperature measurement shall be provided on the gaseous ozone feed line going to the ozone injection point. (c) Ozone aqueous residual analyzers shall be provided to measure the ozone residual concentration in the water being treated in order to determine "CT" credit. (d) An ozone gas analyzer shall be provided on the gas discharge of each ozone destruction unit, or combined vent gas discharge, to determine the exiting ozone concentration. (e) Ambient ozone monitors shall be installed in the vicinity of the ozone generators, the ozone contactors, the ozone destruction units, and other areas where ozone gas may accumulate. (f) Acontinuous dew point monitor shall be provided on the feed gas line to the ozone generators. (g) Instrumentation such as pressure gauges, temperature gauges, flow meters, and power meters shall be provided as necessary to monitor the feed gas system, ozone generators, power supply units, and cooling water to protect the equipment and monitor performance. (8) Alarms and Shutdowns. (a) An ambient ozone monitor shall be provided. (b) The design shall include alarms and shutdowns. (9) Safety. (a) Training shall be provided to the operators of ozone systems by the manufacturers of the ozone equipment, or other professionals with experience in ozone treatment, to promote the safe operation of the systems. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 69 NOTICES OF PROPOSED RULES (b) Appropriate signs shall be installed around ozone and liquid oxygen equipment to warn operators, emergency responders, and others of the potential dangers. (c) Ameans shall be provided, such as portable purge air blowers and portable monitors, to reduce residual ozone levels in an ozone contactor or other equipment to safe levels prior to entry for repair, maintenance, or emergency. (10) Operation and Maintenance. (a) An ambient ozone monitor should activate an alarm when the ozone level exceeds 0.1 ppm. Because the natural ozone levels can exceed 0.1 ppm under certain atmospheric conditions, it is permissible to set the alarm level at a slightly higher level to avoid nuisance alarms. Ozone generator shutdown shall occur when ambient levels exceed 0.3 ppm in the vicinity of an ozone generator or a contactor. Operators of the water treatment system may set the alarm level andthe shutdown level lower at their discretion. It is required that an ozone ambient monitor activates a local audible alarm and/or flashing light warning, in addition to an alarm at the operator control system panel. (b) There shall be an alarm/shutdown to prevent the dew point of the feed gas exceeding the maximum of -76 degrees F (-60 degrees C). (c) Alarms and shutdowns shall be programmed based on the pressure gauges, temperature gauges, flow meters, and power meters, to protect the feed gas system, ozone generators, power supply units, and cooling water system. R309-520-10. Chlorine Dioxide. Public water systems must take into consideration that chlorine dioxide and its byproducts may have similar effects as chloramines on sensitive populations. Chlorine dioxide should not be intentionally used as a secondary disinfectant. The water system must monitor the chlorine dioxide residuals and byproducts in the distribution system. If the chlorine dioxide residual in the distribution system may affect sensitive populations, the public water system shall notify the public of the change. Sensitive populations include hospital and kidney dialysis patients. Sensitive industries include fisheries. (1) Pre-design Proposal. Proposals for the use of chlorine dioxide shall be discussed with the Division prior to the preparation of final plans and specifications. Awater system must submit a detailed written proposal to the Director for review, including: (a) The make, model, and specifications for proposed chlorine dioxide generator (b) References of other U.S. potable water installations of the proposed unit (c) Information on the operational and maintenance training program (d) The expected total applied dosage of chlorine dioxide and other disinfectants as well as the points of application for all disinfectants and the type and amount of residuals and by-products expected in the distribution system (2) Chlorine dioxide generators (a) Chlorine dioxide generation should be designed to be efficient compared to industry standard, and production of excess chlorine shall be minimized. (b) The generator shall not produce a solution with chlorine dioxide concentration more than 6,000 mg/L to minimize the explosion hazard. (c) The design shall include capability to measure concentrations of chlorine dioxide, chlorite, chlorate, and free chlorine of the solution leaving the generator. (d) The chlorine dioxide generator shall be equipped with a chlorine dioxide analyzer to measure the strength of the solution leaving the generator. (e) Generators which use solid chlorite will not be allowed. (3) Chlorine Dioxide Feed and Storage System (a) Chlorine Dioxide Feed system. (i) Use fiberglass reinforced vinyl ester plastic (FRP) or high density linear polyethylene (HDLPE) tanks with no insulation. (ii) If centrifugal pumps are used, provide Teflon packing material. Pump motors must be totally enclosed, fan-cooled, equipped with permanently sealed bearings, and equipped with double mechanical seals or other means to prevent leakage. (iii) Provide chlorinated PVC, vinyl ester or Teflon piping material. Do not use carbon steel or stainless steel piping systems. (iv) Provide glass view ports for the reactor if it is not made of transparent material. (v) Provide flow monitoring on all chemical feed lines, dilution water lines, and chlorine dioxide solution lines. (vi) Provide a means to verify calibrated feed flow to each application feed point. (vii) Control air contact with chlorine dioxide solution to limit potential for explosive concentrations building up within the feed facility. (viii) All chlorite solutions shall have concentrations less than 30%. Higher strength solutions are susceptible to crystallization and stratification. (b) Chlorine Dioxide Storage and OperatingArea. The following requirements apply to the chlorite storage and chlorine dioxide day tank area. (i) The chlorine dioxide facility shall be physically located in a separate room from other water treatment plant operating areas. (ii) The chlorine dioxide area shall have a ventilation system separate from other operating areas. (iii) Provisionshallbemadetoventilatethechlorinedioxidefacilityareaandmaintaintheambientairchlorinedioxideconcentrations below the Permissible Exposure Limit (PEL). (A) The ventilating fan(s) take suction near the floor, as far as practical from the door and air inlet, with the point of discharge so located as not to contaminate air inlets of any rooms or structures. (B) Air inlets are provided near the ceiling. (C) Air inlets and outlets shall be louvered. 70 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (D) Separate switches for the fans are outside and near the entrance of the facility. (iv) The area housing chlorine dioxide facility shall be constructed of non-combustible materials such as concrete. (v) There shall be an ambient air chlorine dioxide sensor in the vicinity of the chlorine dioxide operating area. The ambient air chlorine dioxide readouts and alarm or warning light shall be audible and visible in the operating area and on the outside of the door to the operating area. The design shall include distinguishing audible alarms that are triggered by the ambient air chlorine dioxide sensor readings. (vi) There shall be observation windows through which the operating area can be observed from outside the room to ensure operator safety. (vii) Manual switches to the light in the operating area shall be located outside the door to the room. (viii) There shall be an emergency shower and eyewash outside and close to the door to the operating area. (ix) An emergency shutoff control to shut flows to the generator shall be located outside the operating area. (x) The design shall minimize the possibility of chlorite leaks. (xi) The chlorite tank and chlorine dioxide solution tank shall be vented to the outdoors away from any operating areas. (xii) Gaseous chlorine feed to the chlorine dioxide generator shall enter the chlorine dioxide facility area through lines which can only feed to vacuum. (xiii) The floor of the chlorine dioxide facility area shall slope to a sump. (xiv) There shall not be any open drains in the chlorine dioxide operating area. (xv) Provide secondary containments with sumps for chlorine dioxide storage, and chlorine dioxide solutions which can hold the entire volume of these vessels. This containment shall prevent these solutions from entering the rest of the operating area. (xvi) Provide wash-down water within the operating area. (xvii) The operating area shall be designed to avoid direct exposure to sunlight, UV light, or excessive heat. (4) Other Design Criteria. (a) Provide secondary containment, a sump, wash-down water, and a shower and eyewash at the bulk delivery transfer point. (b) Finished water shall be used for chlorine dioxide generation. (c) The finished water line to the chlorine dioxide generator shall be protected with a high hazard assembly. (d) Provide a water supply near the storage and handling area for cleanup. (e) The parts of the chlorine dioxide system in contact with the strong oxidizing or acid solutions shall be of inert material. (f) The design shall provide the capability to shut off the chlorine dioxide operation remotely, i.e., from a location that is outside of the chlorine dioxide operating area. (5) Operation and Maintenance. (a) Donot storeor handlecombustible or reactivematerials, such asacids, reducedmetals, or organic material, in thechlorine dioxide operating area. (b) Store chemicals in clean, closed, non-translucent containers. (c) Personal protective equipment and first aid kits shall be stored at a nearby location that is outside the chlorine dioxide facility area. (d) The temperature of the chlorine dioxide operating area shall be maintained between 60 and 100 degrees F. (e) After delivery allow chlorite solutions to equalize with the ambient temperature of the operating area to avoid stratification. (f) The Operating and Maintenance manual shall include operator safety and emergency response procedures. Personnel shall have ongoing training for operator safety and emergency response procedures. (g) All wastes should be disposed of in accordance to any existing solid and hazardous waste regulations. (h) The operating area should be inspected daily for chlorite spills and solid chlorite buildup. The daily inspections shall be logged. (i) Chlorite leaks and solid chlorite buildup should be cleaned up and disposed of immediately. (j) Solid chlorite should be washed down before removal. (k) The ventilation system in the chlorine dioxide facility area shall be operated to maintain the ambient air chlorine dioxide concentrations below the Permissible Exposure Limit (PEL). (l) Audible alarms shall be programmed to alert water treatment plant personnel when the ambient air chlorine dioxide sensor in the vicinity of the chlorine dioxide operating area detects the chlorine dioxide concentration above the Permissible Exposure Limit (PEL) and the Short Term Exposure Limit (STEL). R309-520-11. Chloramines. Proposals for the use of Chloramines as a disinfectant shall be discussed with the Division prior to the preparation of final plans and specifications. ]R309-520-1. Purpose. This rule specifies requirements for facilities that disinfect public drinking water.APublic Water System (PWS) shall apply this rule in conjunction with Rules R309-500 through R309-550. These rules govern the design, construction, operation, and maintenance of PWS facilities. The intent of these rules is to ensure that PWS facilities reliably supply adequate quantities of water that consistently meet drinking water quality requirements and do no harm to public health. R309-520-2. Authority. The Drinking Water Board promulgates Rule R309-520 as authorized by Subsection 19-4-104(1)(a)(ii) and in accordance with Title 63G, Chapter 3, UtahAdministrative RulemakingAct. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 71 NOTICES OF PROPOSED RULES R309-520-3. Definitions. Rule R309-110 provides definitions for certain terms used in this rule but this rule may further clarify them. (1) Primary disinfection is the means to provide adequate levels of inactivation of pathogenic microorganisms within the treatment process. (2) Secondary disinfection is the means to provide a disinfectant residual in the distribution system. A supplier achieves secondary disinfection by maintaining a measurable disinfectant residual at every service connection. R309-520-4. Applicability of Disinfection Requirements. (1) For surface water and groundwater under the direct influence (GWUDI), a supplier shall: (a) treat the water using conventional or alternative surface water treatment methods; (b) disinfect the water to meet the requirements of Section R309-200-7; and (c) determine disinfection CT based on the treatment technology used. (2) For groundwater: (a) where a groundwater source does not continuously meet microbiological standards per Rule R309-215, the supplier shall disinfect the groundwater source; (b) where the division requires microbiological treatment for a groundwater source that is not GWUDI, a supplier may disinfect without filtration; and (c) where the division requiresprimary disinfection of a groundwater source, the supplier shall provide sufficient treatment toachieve a minimum of 4-log virus inactivation. (3) Primary disinfection requirements are listed in Subsections (a) through (c). (a) The division allows only chlorine, ozone, ultraviolet (UV) light, and chlorine dioxide as primary disinfectants. A supplier may not use chlorocyanurates species, such as Dichlor or Trichlor dissolution products, as primary disinfectants. (b) Asupplier shall obtain director approval for the baffle factors used in the calculation of CT. (c) Asupplier that is required to achieve primary disinfection shall also achieve secondary disinfection. (4) Secondary disinfection requirements are listed in Subsections (a) and (b). (a) The division allows only chlorine and chloramine as secondary disinfectants. (b) Asupplier may not use chlorocyanurates species such as Dichlor or Trichlor dissolution products) as secondary disinfectants. (5) Point-of-use disinfection is not an acceptable form of disinfection for regulatory compliance. (6) Suppliers of distribution systems that have multiple sources shall meet the requirements in Subsections (a) and (b). (a) Distribution systems downstream of a chlorinated source shall meet secondary disinfection requirements. (b) Ina distribution system where chlorinated water is blended with unchlorinatedwater, the distribution system shall meet secondary disinfection requirements.Asupplier may add chlorination to meet secondary disinfection requirements. (7) Distribution systems with orthophosphate addition shall meet the requirements in Subsections (a) and (b). (a) Any distribution system downstream of orthophosphate injection shall meet secondary disinfection requirements and achieve disinfection residuals of at least 0.2 mg/L of free chlorine in the distribution system at every service connection. (b) A distribution system shall meet secondary disinfection requirements where water with orthophosphate injection is blended. A supplier may add chlorination to meet secondary disinfection requirements. A distribution system where water with orthophosphate injection is blended shall maintain disinfection residuals of at least 0.2 mg/L of free chlorine at every service connection. R309-520-5. Requirements for Disinfection Systems. (1) Continuous disinfection requirements include Subsections (a) through (i). (a) Each disinfection process shall operate continuously and may not stop unless the division provides a written approval to the supplier. (b) Asuppliermaynotuseintermittentorbatchdisinfection,suchasaddinghypochloritetabletsorconcentratedhypochloritesolution to a tank, to achieve primary or secondary disinfection. (c) Asupplier may use intermittent or batch disinfection during seasonal startup or operation and maintenance procedures. (d) The design shall provide a means to isolate or service the disinfection equipment without allowing untreated water to enter the distribution system. (e) The design shall provide a means to continuously disinfect or a plan to shut off the source or system in case of equipment or power failure. (f) Asupplier shall have standby power available for the operation of chlorinator systems unless: (i) the chlorinator system does not require power; or (ii) the source requires power but does not have standby power. (g) A supplier may not have bypasses around disinfection processes, except for oxidation processes that are not used as primary disinfection. (h) Asupplier shall maintain a spare parts kit for disinfection equipment to replace parts subject to wear and breakage. (i) Asupplier shall contact the division within eight hours of a malfunction of any disinfection facility such that a detectable residual cannot be maintained at every service connection. Division personnel may be reached at 801-536-4123. (2) Each disinfection facility shall comply with the requirements in Subsections (a) through (g). (a) The location of the facility shall provide for convenient access and shall consider risks to nearby populations and from seismic fault zones. (b) Asupplier shall provide a lock and secure a facility to prevent vandalism and unauthorized entry. 72 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (c) Disinfection processes after filters shall be fully enclosed and may not daylight. (d) The facility shall include heating, lighting, and ventilation as needed to protect and operate the disinfection system. (e) The facility floors shall be sloped to drain. (f) Where facilities are located underground, the facility shall include a drain and shall drain to daylight where feasible. Where drainage to daylight is not possible, drainage to an underground gravel-filled absorption pit is permissible if the site has adequate drainage and is not subject to flooding. If a drain to daylight or absorption pit are not feasible, a sump pump is permissible. (g) The facility design shall be in accordance with the Utah Occupational Safety and HealthAct (UOSHA), in accordance with Title 34A, Chapter 6, Utah Occupational Safety and HealthAct. (3) Asupplier shall obtain prior written approval from the director for any modifications that may affect the water quality or quantity, including changes in chlorine type. (4) Asupplier may not use disinfection: (a) to mask ongoing contamination; (b) to remedy a source susceptible to surface water influence; or (c) as a substitute for correcting physical deficiencies. (5) Any material that may contact drinking water shall be certified to meet NSF/ANSI 61. (6) Any chemical added to drinking water, including chlorine gas, hypochlorite solution, hypochlorite tablets, granules, powder, chloramines, chemicals used to generate hypochlorite solution and chlorine dioxide, and chemicals used in the cleaning of components in contact with the drinking water, shall be NSF/ANSI Standard 60 certified. (7) A supplier shall follow the requirements of the International Plumbing Code, as adopted in Section 15A-2-103 and amended in Title 15A, Chapter 3, Statewide Amendments Incorporated as Part of State Construction Code and Title 15A, Chapter 4, Local Amendments Incorporated as Part of State Construction Code, as applicable. (8) Asupplier shall follow the cross connection control requirements of Rule R309-105. (9) Asupplier shall make provisions for proper disposal of water treatment plant waste discharges and meet the requirements of Title R317. R309-520-6. Chemical Feed Equipment. (1) Asupplier shall submit the information in Subsections (a) through (d) for division review and director approval: (a) descriptions of chemical feed equipment, including maximum and minimum feed rates; (b) location of chemical feeders, piping layout and points of application; (c) descriptions of chemical storage and handling facilities; and (d) chemical specifications. (2) Asupplier shall prominently display Safety Data Sheets of chemicals and ensure they are easily accessible. (3) Asupplier shall have a safe handling and leak response Standard Operating Procedure (SOP) for each chemical. (4) To ensure chemical compatibility, a supplier: (a) may not feed, store, or handle incompatible chemicals together; (b) shall conduct each chemical from the chemical feeder to the point of application in a separate conduit; (c) shall ensure chemical-contact materials and surfaces are compatible with the chemicals; (d) shall locate the injection point at the center of a pipeline; and (e) shall ensure chemical feeders are readily accessible for servicing, repair, and observation. (5) Chemical feed rate controls shall meet the requirements in Subsections (a) through (f). (a) Chemical feeders shall supply the chemicals at an accurately controlled rate, throughout the anticipated range of feed. (b) Asupplier shall use automatic proportioning chemical feeders where the rate of flow varies. (c) Asupplier shall provide a means of measuring water flow rate. (d) Asupplier shall provide a means of measuring the quantities of chemicals used to prepare chemical feed solutions and quantities of chemicals added in the treatment process. (e) A supplier shall manually or automatically control chemical feeders. Suppliers with automatic controls shall design automatic controls to allow override by manual controls. (f) Chemical feeders and pumps shall operate within the manufacturer design feed range. (6) At surface water and GWUDI treatment facilities, a supplier shall provide at least one active feeder and one standby feeder. (7) Chemical feed pump requirements are listed in Subsections (a) through (c). (a) Asupplier shall size the pump to match or exceed maximum head conditions found at the point of injection. (b) Liquid chemical feed pumps shall be positive displacement type solution-feed pumps or other feed pump designs as approved by the director. Liquid chemical feed pumps shall include devices which prevent backpressure, backsiphonage, or siphonage of liquid chemicals through the pump by using: (i) positive pressure at the point of injection; (ii) vacuum relief; (iii) an air gap; (iv) an anti-siphon device; or (v) another means to prevent siphoning. (c) Chemical feed pumps shall have a strainer and a means of flushing the strainer. The strainer shall be located upstream of the chemical feed pumps. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 73 NOTICES OF PROPOSED RULES (8) Liquid chemical storage tanks shall adhere to the requirements in Subsections (a) through (f) unless otherwise approved by the director in writing. (a) Asupplier shall keep chemical solutions covered. (b) Asupplier shall label tanks to designate the chemical contained. (c) Asupplier shall provide chemical storage tanks with secondary containment unless otherwise approved by the director in writing. The director may grant approval for an alternative approach if the authority responsible for receiving or regulating the discharge provides a written letter supporting the alternative.Asupplier shall submit the letter of support to the director for consideration. (i) The secondary containment material shall be impermeable and compatible with the stored chemical. (ii) Asupplier shall design secondary containment drainage such that it prevents uncontrolled releases outside the containment area. The drainage shall drain to a containment area designed for compatibility with the stored chemical and shall receive drainage of compatible chemicals only. (iii) Secondary containment volumes shall be at least the same volume as the largest chemical storage tank. (iv) A supplier is not required to provide secondary containment for hypochlorite solution tanks with a hypochlorite concentration less than or equal to 1% and volume less than or equal to 350 gallons. (d) If a supplier provides overflow pipes, the overflow pipes shall: (i) have a No. 4 mesh, non-corrodible screen; (ii) have a free-fall discharge to a receiving basin; and (iii) be readily visible. (e) If a tank has a drain, the supplier shall provide a shut-off valve for the tank drain. (f) Tanks equal to or greater than 350 gallons shall have: (i) a liquid level indicator; (ii) an overflow; and (iii) a downturned air vent with a No. 14 mesh, non-corrodible screen. (g) Bulk chemical delivery transfer points shall include a means of chemical containment, wash-down water, a shower, and an eyewash station. (9) Weighing scales shall be corrosion resistant and accurate to measure increments of at most 0.5% of scale capacity. (10) Make-up water is water used for diluting a chemical. Make-up water supply shall be of a quality equal to or better than the water at the point of application.Asupplier shall provide a means to measure make-up water when preparing solution concentrations by dilution. (11) Asupplier shall meet cross connection control requirements in Subsections (a) through (d). (a) Make-up water lines that discharge into solution tanks shall include protection against backpressure or backsiphonage according to the International Plumbing Code, as adopted in Section 15A-2-103 and amended in Title 15A, Chapter 3, Statewide Amendments Incorporated as Part of State Construction Code and Title 15A, Chapter 4, LocalAmendments Incorporated as Part of State Construction Code, as applicable. (b) Chemical feed system drains and overflows may not have a direct connection to any sewer. The drains or overflows shall have an air gap above the receiving vessel of at least six inches or two pipe diameters, whichever is greater. (c) At surface water and GWUDI treatment facilities, pre- and post-chlorination systems shall have independent pumping systems, unless a vacuum breaker is installed between the pre- and post-chlorination systems to prevent backpressure or backsiphonage of partially treated water into the clear well. (d) Each eductor shall have a separate shut-off valve on the water supply and not a master shut-off valve. R309-520-7. Chlorine. (1) Requirements for each chlorine system are listed in Subsections (a) through (f). (a) Asupplier shall submit a basis of design to the division. The basis of design shall include: (i) an estimate and justification of breakpoint chlorination dose; (ii) expected seasonal variation; and (iii) target chlorine residual above breakpoint chlorination dose. (b) The director may require a chlorine demand study when the director determines that the proposed disinfection process may not maintain a disinfectant residual throughout the distribution system. (c) Each chlorinator shall have a designated Point-of-Entry (POE) that: (i) is located after sufficient mixing to achieve a stable chlorine residual; (ii) is located before or at the first service connection; and (iii) has a continuous disinfectant analyzer for suppliers serving populations of 3,300 or more. (d) Disinfection by chlorination shall be accomplished by gaseous chlorine or hypochlorite solutions. Hypochlorite solutions can be purchased, generated on site, or prepared by dissolving solids. (e) Chlorine feed equipment requirements are listed in Subsections (i) through (iv). (i) Chlorine feed equipment shall: (A) operate accurately over the design feeding range; (B) be sized to provide at least 2 mg/L free chlorine residual at the POE during peak demand; and (C) be sized to deliver a chlorine dose sufficient to maintain a measurable residual continuously at each service connection in the distribution system. (ii) If a supplier uses an eductor, the supplier shall provide a strainer upstream of the eductor and a means of flushing the strainer. (iii) Chlorine injectors and eductors shall: 74 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (A) inject chlorine at the center of a pipeline where possible; (B) inject chlorine at a point that allows rapid mixing; (C) be compatible with; (I) the point of application; (II) the flowrate of chlorine; (III) the size of the chlorine solution line; (IV) the back pressure from the water line; and (V) the equipment operating pressure. (iv) When releasing chlorinated water into the environment, the supplier shall comply with Rule R317-2. (f) Asupplier shall have a digital chlorine residual analyzer capable of measuring residual to the nearest 0.1 mg/L. (2) Gas chlorinator systems shall: (a) be a solution-feed type; (b) have automatic switchover unless at least three cylinders or containers are operational continuously; (c) have at least two chlorine cylinders unless the gas chlorinator system uses fewer than one per year; (d) have a gas scrubber in operating areas with a one-ton chlorine cylinder; (e) include the ventilation requirements in Subsections (e)(i) through (iii); (i) chlorination equipment rooms that contain chlorine cylinders, tanks, equipment and gaseous chlorine lines under pressure shall have at least one exhaust fan unless power is not available or human entrance to the room is not possible. Chlorine room exhaust fans, when operating, shall provide at least one complete room air change per minute. (ii) The ventilation system shall include air inlet louvers near the ceiling and discharge venting near the floor, as far as practical from the door. (iii) The supplier shall design the ventilation system for one-ton chlorine cylinder operating areas to maintain negative pressure and operate independently from the ventilation system for the rest of the facility. (f) discharge the chlorine vent line outside above grade and screen the end with a No. 14 mesh non-corrodible screen. (g) Requirements for chlorine cylinder storage are listed in Subsections (g)(i) through (ii). (i) Chlorine cylinders shall have restraints and be stored in an upright position. (ii) Chlorine cylinders may not be located in direct sunlight or exposed to excessive heat. (h) Requirements for gas chlorinator housing at water treatment plants with multiple processes are listed in Subsections (h)(i) through (vi). (i) The supplier shall provide a separate chlorine room to house chlorine cylinders and feed equipment. (ii) The supplier shall seal openings between the chlorine room and the rest of the facility. (iii) The supplier shall design doors to open outward and equip them with panic bars to allow rapid exit. (iv) Floor drains, though discouraged, shall discharge outside the building and may not connect to other drain systems of the facility. (v) Chlorine feed lines may not carry pressurized chlorine gas outside the chlorine room. Vacuum lines may be routed to other portions of the building outside the chlorine room. The supplier shall seal any openings for these lines. (vi) Gas chlorine rooms with doors interior to a facility shall have a shatter resistant inspection window. (i) The supplier shall provide pressure gauges on the inlet and outlet of each chlorine eductor. (j) Operator safety requirements are in Subsections (j)(i) through (iv). (i) The supplier shall make a bottle ofAmmonium Hydroxide solution with 56% ammonia available for leak detection. (ii) Where a supplier provides a continuous leak detector, it shall be equipped with an audible alarm and a readily visible warning light. (iii) The supplier shall make NIOSH-approved respiratory protection equipment immediately accessible. (iv) Where one-ton cylinders are used, the supplier shall: (A) store and make available NIOSH-approved Self Contained BreathingApparatus (SCBA) outside the chlorine room; (B) ensure the SCBAhas a minimum 30-minute capacity of compressed air; (C) ensure the SCBAis compatible with units used by the fire department responsible for the plant; (D) store and make available a leak repair kit approved by the Chlorine Institute; and (E) provide continuous chlorine leak detection equipment with an audible alarm and a visible warning light. (3) Additional requirements for hypochlorite systems are in Subsections (a) through (c). (a) General requirements for each hypochlorite system are in Subsections (i) through (iii). (i) Emergency Eyewash and Safety Showers.Asupplier shall provide an emergency eyewash and safety shower where hypochlorite solutions containing chlorine concentration of at least 5% are handled in containers of at least 55 gallons. For installations using hypochlorite at chlorine concentrations less than 5%, or volumes less than 55 gallons, the supplier shall provide an alternative emergency eyewash. If a supplier provides a shower or eyewash station, they shall be plumbed with drinking water. (ii) Liquid hypochlorite storage shall prevent decay. The supplier shall design storage and injection areas to minimize the effects of excessive heat or direct sunlight. (iii) For flow-powered pump systems, the flow through the pump shall meet the minimum pump flow as required bythe manufacturer at every flow scenario.Atank with a control valve may follow the pump to ensure manufacturer-required pump flow requirements are met. (b) On-Site generated hypochlorite system requirements are in Subsections (i) through (iii). (i) Asupplier shall follow manufacturer recommendations for safety with respect to equipment and electrical power. (ii) The hydrogen gas generated in the electrolytic cell of the on-site generation system shall vent upward to the outside of the building in a dedicated line with a non-corrodible No. 14 mesh screen at the end. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 75 NOTICES OF PROPOSED RULES (iii) Hypochlorite tanks shall have a downturned air vent with a non-corrodible No. 14 mesh screen at the end. (c) Hypochlorite tablet system requirements are in Subsections (i) and (ii). (i) Hypochlorite tablet disinfection processes shall be compatible with the water hardness, solubility of hypochlorite tablets, water temperature, and other water quality factors. (ii) A supplier shall store the hypochlorite tablets in accordance with the manufacturer's safety guidelines and in their original containers in a cool, dry, well-ventilated area. Asupplier may not store hypochlorite tablets near combustible materials or acids. R309-520-8. Ultraviolet Light. (1) This rule shall apply to the use of ultraviolet (UV) disinfection for inactivation of Cryptosporidium, Giardia, and viruses. The director may reduce the requirements of monitoring and reporting on a case-by-case basis for water systems that use UV for other reasons. (a) Suppliers using surface water or GWUDI may not use UV as the sole means of achieving primary disinfection and shall provide a backup primary disinfectant. The backup primary disinfectant shall be approved to achieve the CT, log removal, or inactivation required for compliance. The backup primary disinfectant shall be able to achieve treatment requirements within 15 minutes so that the continuous duration of an off- specification event is limited to no more than 15 minutes. (b) Asupplier that wishes to receive Log Removal or Inactivation Credit for UV disinfection shall: (i) submit a UV plan which identifies the dose monitoring strategy, such as the UV intensity setpoint approach, the calculated dose approach, or an alternative approach; (ii) identify the goals for the UV facility as part of a comprehensive disinfection strategy, including target pathogens, target log removal or inactivation, and corresponding required UV dose per Rule R309-215; (iii) submit a UV reactor validation report; and (iv) monitor and report per Rule R309-215 after installation. (2) Validation testing requirements are listed in Subsections (a) through (c). (a) The director may accept a validation report that was conducted based on the 2006 Final Ultraviolet Disinfection Guidance Manual For The Final Long Term 2 Enhanced Surface Water Treatment Rule (UVDGM), incorporated by reference in this rule, the 2020 Innovative Approaches of Ultraviolet Disinfection Reactors for Drinking Water Systems (IAUDRDWS), incorporated by reference in this rule, or on a case-by-case basis. The supplier shall ensure UV disinfection units rated at 30 gallons per minute or less meet ANSI/NSF Standard 55, Class A, or other equivalent standards that the director considers acceptable in lieu of a validation report. (b) Each model and configuration of UV reactor must undergo off-site, full-scale validation testing by an independent third party test facility. The validation testing shall be conducted in qualified test facilities that are deemed acceptable by NSF, EPA, or the director. (c) The UV reactor validation report shall include: (i) descriptionofthereactorandvalidationtestsetup,includinggeneralarrangementandlayoutdrawingsofthereactorandvalidation test piping arrangement; (ii) description of the methods used to empirically validate the reactor; (iii) description of the dose monitoring equation for the reactor to achieve the target pathogen inactivation credit and related graphical plots showing how the equation was derived from measured doses obtained through validation testing under varying test conditions; (iv) range of validated conditions for flow, UV Transmittance (UVT), UV dose, and lamp status; (v) description and rationale for selecting the challenge organism used in validation testing, and analysis to define operating dose for pathogen inactivation credit. (vi) tabulated data, analysis, quality assurance and quality control, and measures during validation testing; (vii) a licensed professional engineer's third party oversight certification indicating that the testing and data analyses in the validation report are conducted in a technically sound manner and without bias; and (viii) the validation report shall be accompanied with completed Checklists 5.1 through 5.5 included in the 2006 UVDGM. (3) Design criteria requirements are listed in Subsections (a) through (j). (a) Asupplier shall gather water quality data representative of the water to be treated by the UV facility. The director may prescribe a testing frequency to characterize variation or seasonal trends in water quality. The supplier shall submit and consider the following water quality results in UV facility planning as determined by the director: (i) UVT or UV absorbance; (ii) calcium; (iii) alkalinity; (iv) hardness; (v) iron; (vi) manganese; (vii) turbidity; (viii) pH; (ix) Oxidation-Reduction Potential (ORP); and (x) particle content and algae. (b) UV systems shall provide the required dose to at least 95% of the water delivered, accounting for seasonal variations of flow and UVT combinations. The director may require the supplier to submit a matrix of flow and UVT conditions for the UV reactors. (c) UV reactor inlet and outlet configurations shall meet the validated hydraulic distribution of flow conditions. The supplier can achieve this using one of the following approaches: (i) The inlet and outlet configuration meets one of the conditions specified in Section 3.6.2 of the 2006 UVDGM. 76 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (ii) Computational fluid dynamics, CFD-based modeling demonstrates that the given conditions of inlet and outlet piping with the UV installation provides equal or greater dose delivery. The CFD modeling shall be conducted at the minimum and maximum values of the validated range of flow, UVT, and lamp status. (d) The UV system shall be capable of applying the required design dose with one out-of-service reactor or otherwise provide redundant treatment for target pathogens. (e) The design shall allow isolation of each reactor for maintenance. (f) The UV system shall include signals and alarms for the operation of the UV facility for the parameters necessary for dose monitoring algorithm, such as low UV dose, high flow rate, low UVT, UVT monitoring failure, UV sensor failure, off-specification event, Ground Fault Interrupt GFI, high water temperature, and low water level. (g) Any chemicals used in the cleaning of the UV reactor components in contact with the drinking water such as quartz sleeves shall be certified as meeting theANSI/NSF Standard 60 - Drinking Water Treatment Chemicals - Health Effects. (h) The control system shall include a flow or time delay to permit a sufficient time for lamp warm-up, per manufacturer recommendations, before water flows from the unit upon startup. (i) The supplier shall submit the dose monitoring approach of the UV system to the director for review and approval. The dose monitoring approaches shall meet the guidelines stated in the 2006 UVDGM or the 2020 IAUDRDWS. (j) If the supplier uses a Programmable Logic Controller (PLC) or SCADA interface for a UV reactor's process control, the programming shall be in accordance with the validated dose monitoring algorithm and the validated conditions. The algorithm shall use inputs of flow, UV intensity sensor readings, lamps status, and UVT equal to or more conservative than values measured during the operation of the UV system. (i) If the measured UVT is above the validated range, the dose algorithm shall use the maximum validated UVT as the input. If the measured flow rate is below the validated range, the dose algorithm shall use the minimum validated flow rate as the input. (ii) If the dose algorithm uses relative lamp output determined from the UV intensity sensor readings as an input, the supplier shall base the relative lamp output on the measured UVT, even if it exceeds the maximum validated UVT. (iii) Asupplier shall program the UV reactor's PLC or microprocessor to record off-specification events for the following conditions: (A) delivered UV dose less than the required dose; (B) flow greater than the validated range; (C) UVT less than the validated range; (D) lamp status outside the validated range; and (E) failure of UV sensors, flow meters, or on-line UVT monitors used in the dose calculation. Laboratory measurements of UVT may be used in the program until the on-line UVT monitor is repaired for a maximum of 30 days. (4) Asupplier shall have an operation and maintenance manual that follows the manufacturer's recommendation or the operation and maintenance guidelines stated in Sections 6.2 through 6.5 of the 2006 UVDGM. R309-520-9. Ozone. (1) Section R309-520-8 applies to ozone used for primary disinfection only. (2) A supplier using surface water or GWUDI may not use ozone as the sole means of disinfection. A supplier shall provide an approved primary disinfectant as an alternative primary disinfectant to achieve the CT, log removal, or inactivation required for compliance. The alternative primary disinfectant shall be able to achieve the treatment requirements within 15 minutes so that the continuous duration of an off- specification event is limited to no more than 15 minutes. (3) Asupplier shall conduct a pilot study or bench scale study for surface water or GWUDI unless the director determines sufficient data is available from other studies performed on the same water source. (a) The study shall determine the initial ozone demand, the rate of ozone decay, the minimum and maximum ozone dosages for the range of water conditions for disinfection "CT" compliance, and the ozone dosage required for other desired benefits. (b) Pilot studies or bench scale studies shall consider the seasonal and other variations of the source water. A supplier shall ensure plans for pilot studies or bench scale studies are reviewed and approved by the director before starting the study. (4) Ozone installations shall comply with the Utah Fire Code. (5) Ozone generation systems shall meet the requirements in Subsections (a) through (d). (a) The ozone system shall be designed with backup capability such that required inactivation can be achieved with one generator out of service. (b) The ozone generators shall be housed: (i) in an enclosed temperature-controlled building for protection; and (ii) with ventilation capable of providing six or more air changes per hour in case of an ozone leak. (c) The ozone generators shall be of the medium or high frequency type. (d) Water-cooled ozone generators and water-cooled power supply units shall meet the requirements in Subsections (i) through (v). (i) A supplier shall water-cool ozone generators and power supply units to manufacturer specifications. A supplier shall submit documentation demonstrating compliance with these specifications including water flow rate, pressure, and temperature to the division. (ii) The design shall include appropriate cross connection control measures for the heat exchanger to prevent the contamination of the drinking water supply. Where cooling water is treated, a supplier shall provide cross connection control to prevent contamination of the drinking water supply. Steam condensation, engine jacket cooling water, or water used by heat exchange dryers may not return to the drinking water supply. (iii) The design engineer shall specify the allowable maximum increase in cooling water temperature, which may not exceed 10 degrees Fahrenheit unless otherwise justified by manufacturer specifications and approved by the reviewing authority. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 77 NOTICES OF PROPOSED RULES (iv) Where necessary, the design shall include provisions for cooling water treatment to minimize corrosion, scaling, and microbiological fouling of the water side of the tubes. The selection of any treatment method shall be justified and submitted for review. (v) The director may require a supplier to use a closed-loop cooling water system to ensure proper water conditions are maintained. (6) Ozone generator feed gas shall meet the requirements in Subsections (a) through (e). (a) Asupplier may use feed gas that is air, vaporized high purity liquid oxygen, or oxygen-enriched air. (b) Asupplier shall use oxygen that is generated on site or delivered in bulk. (c) The design of the feed gas system shall ensure feed gas does not exceed the maximum dew point of -76 degrees F. (d) Liquid oxygen feed gas system shall meet the requirements in Subsections (i) through (iii). (i) Asupplier shall size liquid oxygen storage tanks to provide a minimum of a 7-day supply to the ozone generators at the maximum operating rate. (ii) Asupplier shall provide two or more vaporizers to convert liquid oxygen to the gaseous form. (iii) Vaporizers shall be capable of maintaining oxygen flow at the minimum design air temperature with one unit on standby. (e) Air- or Oxygen-enriched air feed gas system shall meet the requirements in Subsections (i) though (iv). (i) Asupplier shall provide two or more air compressors to supply air. (ii) The capacity of the compressors shall meet the demand during maximum ozone production and compressed air usage with the largest compressor out of service. (iii) Asupplier shall provide entrainment separators, refrigeration dryers, desiccant dryers, and filters as necessary to ensure a dried, dust-free, and oil-free feed gas to the ozone generators. (iv) Asupplier shall provide redundant equipment to ensure continuous operation when the largest equipment is out of service. (7) Ozone contactors shall meet the requirements in Subsections (a) through (n). (a) An ozone contactor shall consist of two or more chambers to introduce ozone into the water and achieve contact time. (b) Asupplier shall seal and maintain an ozone contactor at less than atmospheric pressure to prevent escape of ozone gas. (c) The materials of construction shall be ozone-resistant. (d) A supplier may inject ozone gas into the water by using positive pressure through bubble diffusers using porous-tube or dome diffusers. Alternatively, a supplier may inject ozone gas into the water by using side stream injection using negative pressure generated with a venturi. (e) Asupplier shall design ozone contactors to achieve a minimum transfer efficiency of 85%. (f) Asupplier shall provide sampling points in an ozone contactor to demonstrate CT. (g) Asupplier shall have provision for cleaning, maintenance, and drainage of the ozone contactor. (h) Asupplier shall equip each contactor chamber with an access hatchway or other means of entry. (i) An ozone contactor shall have an emergency off-gas pressure-vacuum relief system to prevent damage to the unit. (j) Asupplier shall provide a system for worker safety at the end of the ozone contactor for compliance with OSHAstandards. Ozone levels in the gas space above treated water that has exited the contactor may not exceed the established OSHA 8-hour exposure limit of 0.1 ppm. (k) Asupplier shall provide a system for treating the final off-gas from each ozone contactor. The off-gas treatment system shall have at least two units which are each capable of handling the entire off-gas flow.Asupplier shall use a system using thermal destruction or catalytic destruction. (l) Asupplier shall provide exhaust blowers to draw off-gas from the contactor into the destruction units. (m) Asupplier shall provide a means of protecting the destruction units and piping from moisture and other impurities that may cause damage. The system shall include a means of draining condensation from the off-gas piping. (n) The maximum allowable ozone concentration in the gas discharge from a destruction unit is 0.1 ppm by volume. (8) For piping and connections, a supplier shall: (a) use low carbon 304L and 316L stainless steel for ozone gas service; (b) provide welded piping connections for ozone service; (c) provide connections with meters, valves, or other equipment with flanged joints with ozone-resistant gaskets; and (d) provide a positive-closing 90-degree turn isolation valve or other equivalent means in the piping between an ozone generator and a contactor for use when the contactor is not operating. (9) Instrumentation and monitoring equipment shall include: (a) a flow meter, temperature sensor, and pH sensor to monitor the influent water parameters of the ozone system; (b) an ozone gas analyzer, a flow meter, and a temperature sensor on the gaseous ozone feed line going to the ozone injection point; (c) dissolved ozone analyzers to measure the ozone residual concentration throughout the ozone contactor as needed to determine CT credit; (d) an ozone gas analyzer on the gas discharge of each ozone destruction unit or combined vent gas discharge to determine the discharge ozone concentration; (e) ambient ozone monitors in the vicinity of the ozone generators, the ozone contactors, the ozone destruction units, and other areas where ozone gas may accumulate; (f) a dew point monitor on the feed gas line to the ozone generators; and (g) instrumentation such as pressure gauges, temperature gauges, flow meters, and power meters as needed to monitor the feed gas system, ozone generators, power supply units, and cooling water to protect the equipment and monitor performance. (10) Alarms and shutdowns requirements are in Subsections (a) through (c). (a) Anambientozonemonitorshallactivateanalarmwhentheozonelevelexceeds0.1ppm.Ifatmosphericconditionscausenuisance alarms, the director may approve a higher alarm trigger level. 78 UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 NOTICES OF PROPOSED RULES (b) Ozone generator shutdown shall occur when ambient levels exceed 0.3 ppm or lower in the vicinity of an ozone generator or a contactor.An ozone ambient monitor shall activate a local audible alarm or flashing light warning, in addition to an alarm at the operator control system panel. (c) An alarm or shutdown shall prevent the dew point of the feed gas from exceeding -76 degrees F. (11) Safety requirements are in Subsections (a) through (d). (a) An operator of an ozone system shall receive site-specific training from the manufacturers of the ozone equipment or other professionals with experience in ozone treatment. (b) Asupplier shall receive an operations and maintenance manual from the manufacturer. (c) A supplier shall install signs around ozone and liquid oxygen equipment to warn operators and emergency responders of the potential dangers. (d) A supplier shall provide a means to reduce residual ozone levels in an ozone contactor or other equipment to safe levels before entry for repair, maintenance, or emergency. R309-520-10. Chlorine Dioxide. (1) Asupplier shall use chlorine dioxide only as a primary disinfectant.Asupplier shall obtain the director's approval for the storage and use of sodium chlorite before the preparation of final plans and specifications. (2) A supplier shall submit a pre-design proposal for the use of chlorine dioxide to the division before the preparation of final plans and specifications. The proposal shall include: (a) rationale for implementation of chlorine dioxide; (b) chemicals to be used in the generation of chlorine dioxide; (c) the make, model, and specifications for proposed chlorine dioxide generator; (d) references of other drinking water installations of the proposed unit in the US; (e) information on the operational and maintenance training program; (f) the expected total applied dosage of chlorine dioxide and other disinfectants; (g) points of application for disinfectants; (h) type and quantity of residuals and byproducts expected in the distribution system; and (i) strategy to limit potential for explosion. (3) Chlorine dioxide generation requirements are in Subsections (a) through (f). (a) Asupplier shall use finished water for chlorine dioxide generation.Asupplier shall protect the finished water line to the chlorine dioxide generator with a high hazard backflow prevention assembly. (b) Asupplier shall design chlorine dioxide generation to minimize excess production. (c) The generator may not produce a solution with chlorine dioxide concentration more than 6,000 mg/L to minimize the explosion hazard. (d) A supplier shall provide a means to measure concentrations of chlorite, chlorate, and free chlorine of the solution leaving the generator. (e) A supplier shall equip the chlorine dioxide generator with a continuous chlorine dioxide analyzer to measure the strength of the solution leaving the generator. (f) Asupplier may not use generators which use solid chlorite. (4) Chlorine Dioxide Feed system requirements are in Subsections (a) through (h). (a) The system shall store sodium chlorite and hydrochloric acid in fiberglass reinforced vinyl ester plastic (FRP) or high density linear polyethylene (HDLPE) tanks without insulation. (b) The system shall use positive displacement feeders where possible. If a supplier uses centrifugal pumps, the pump shall have Teflon packing material. Pump motors shall be totally enclosed, fan-cooled, have permanently sealed bearings, and have double mechanical seals or other means to prevent leakage. (c) Tubingforconveying sodium chlorite orchlorine dioxide solutionsshall beType 1 PVC, polyethylene,or materialsrecommended by the manufacturer. Piping material shall be chlorinated PVC, vinyl ester, or Teflon. A supplier may not use carbon steel or stainless steel piping systems. (d) The system shall include check valves to prevent the backflow of chlorine into the sodium chlorite line. (e) The system shall include glass view ports for the reactor if it is not made of transparent material. (f) The system shall include a calibration tube for each chemical feed line, dilution water line, and chlorine dioxide solution line. (g) The maximum concentration of chlorite solutions shall be 30%. (5) The chlorine dioxide operating area, which includes the chlorite storage and chlorine dioxide day tank area, requirements are in Subsections (a) through (p). (a) A supplier shall properly store and handle sodium chlorite to eliminate any danger of explosion. The chlorine dioxide facility shall be in an independent room separated from other chemicals and treatment equipment. (b) The chlorine dioxide facility shall be constructed of non-combustible materials. (c) A supplier may not store or handle combustible or reactive materials, such as acids, reduced metals, or organic material in the chlorine dioxide operating area. (d) The facility shall include observation windows to allow the operating area to be viewed from outside the room. (e) Switches to the light in the operating area shall be outside the room. (f) An emergency shower and eyewash shall be outside and close to the door of the operating area. UTAH STATE BULLETIN, September 15, 2026, Vol. 2026, No. 18 79 NOTICES OF PROPOSED RULES (g) An emergency shut-off control for flows to the generator shall be outside the operating area. Additionally, the capability to shut off the chlorine dioxide operation remotely shall be available. (h) The chlorite tank and chlorine dioxide solution tank shall include vents. The vent shall discharge outside, discharge above grade, and have a No. 14 mesh non-corrodible screen cover at the end. (i) Gaseous chlorine feed to the chlorine dioxide generator shall enter the chlorine dioxide facility area through lines which can only feed to vacuum. (j) The operating area shall have wash-down water. (k) The floor of the chlorine dioxide facility area shall slope to a sump.Achlorine dioxide operating area may not have a drain. (l) Chlorine dioxide storage and chlorine dioxide solutions shall have secondary contaminants which can hold the entire volume of the vessel. The secondary containment shall have concrete curbs and a sump. (m) A supplier shall store personal protective equipment and first aid kits at a nearby location that is outside the chlorine dioxide facility area. (n) The chlorine dioxide area shall have a separation ventilation system from other operating areas to maintain the ambient air chlorine dioxide concentrations below the Permissible Exposure Limit (PEL). (i) The ventilating fan shall take suction near the floor, as far as practical from the door and air inlet, with the point of discharge located to prevent contamination of air inlets to any rooms or structures. (ii) Air inlets shall be provided near the ceiling. (iii) Air inlets and outlets shall be louvered. (iv) Switches for the fans shall be outside and near the entrance of the facility. (o) The chlorine dioxide operating area shall have an ambient air chlorine dioxide sensor. The sensor shall trigger audible and visible alarms in the operating area and outside the door to the operating area. (p) Asupplier shall maintain the temperature of the chlorine dioxide operating area between 60 and 100 degrees F. R309-520-11. Chloramines. If a supplier desires to use chloramines as a disinfectant, the supplier shall submit a proposal to the director for review and approval. The director may determine the acceptability of chloramines as a disinfectant. KEY: drinking water, primary disinfectants, secondary disinfectants, operation and maintenance Date of Last Change: [November 16, 2015]2026 Notice of Continuation: February 10, 2025 Authorizing, and Implemented or Interpreted Law: 19-4-104 NOTICE OF SUBSTANTIVE CHANGE TYPE OF FILING: Repeal and Readopt Filing ID: 58215