Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.552 - OPERATING CRITERIA FOR PUBLIC WATER SYSTEMS

Universal Citation: ID Admin Code 58.01.08.552

Current through August 31, 2023

01. Quantity and Pressure Requirements. Design requirements regarding pressure analysis are found in Section 542.13. (3-24-22)

a. Minimum Capacity. The capacity of a public drinking water system shall be at least eight hundred (800) gallons per day per residence. (3-24-22)
i. The minimum capacity of eight hundred (800) gallons per day shall be the design maximum day demand rate exclusive of irrigation and fire flow requirements. (3-24-22)

ii. The minimum capacity of eight hundred (800) gallons per day is only acceptable if the public drinking water system has equalization storage of finished water in sufficient quantity to compensate for the difference between a water system's maximum pumping capacity and peak hour demand. (3-24-22)

iii. The design capacity of a public drinking water system for material modifications may be less than eight hundred (800) gallons per day per residence if the water system owner provides information that demonstrates to the Department's satisfaction the maximum day demand for the system, exclusive of irrigation and fire flows, is less than eight hundred (800) gallons per day per residence. (3-24-22)

b. Pressure. All public water systems shall meet the following requirements: (3-24-22)
i. Any public water system shall be capable of providing sufficient water during maximum day demand conditions, including fire flow where provided, to maintain a minimum pressure of twenty (20) psi throughout the distribution system, at ground level, as measured at the service connection or along the property line adjacent to the consumer's premises. (3-24-22)

ii. Public Notification. (3-24-22)
(1) During unplanned or emergency situations, when water pressure within the system is known to have fallen below twenty (20) psi, the water supplier must notify the Department, provide public notice to the affected customers within twenty-four (24) hours, and disinfect or flush the system as appropriate. When sampling and corrective procedures have been conducted and after determination by the Department that the water is safe, the water supplier may re-notify the affected customers that the water is safe for consumption. The water supplier shall notify the affected customers if the water is not safe for consumption. (3-24-22)

(2) During planned maintenance or repair situations, when water pressure within the system is expected to fall below twenty (20) psi, the water supplier must provide public notice to the affected customers prior to the planned maintenance or repair activity and shall ensure that the water is safe for consumption. (3-24-22)

iii. If an initial investigation by the water supplier fails to discover the causes of inadequate or excessive pressure, the Department may require the water supplier to conduct a local pressure monitoring study to diagnose and correct pressure problems. Compliance with these requirements by water systems that do not have a meter vault or other point of access at the service connection or along the property line adjacent to the consumer's premises where pressure in the distribution system can be reliably measured shall be determined by measurements within the consumer's premises, or at another representative location acceptable to the Department. (3-24-22)

iv. Copies of pressure monitoring study reports required under Subsection 552.01.b.iii. detailing study results and any resulting corrective actions planned or performed by the public water system shall be submitted to the Department in accordance with these rules. (3-24-22)

v. The following public water systems or service areas of public water systems shall maintain a minimum pressure of forty (40) psi throughout the distribution system, during peak hour demand conditions, excluding fire flow, measured at the service connection or along the property line adjacent to the consumer's premises. (3-24-22)
(1) Any public water system constructed or substantially modified after July 1, 1985. (3-24-22)

(2) Any new service areas. (3-24-22)

(3) Any public water system that is undergoing material modification where it is feasible to meet the pressure requirements as part of the material modification. (3-24-22)

vi. Any public water system shall keep static pressure within the distribution system below one hundred (100) psi and should ordinarily keep static pressure below eighty (80) psi. Pressures above one hundred (100) psi shall be controlled by pressure reducing valve stations installed in the distribution main. In areas where failure of installed pressure reducing valve stations would result in extremely high pressure, pressure relief valves may be required. The Department may approve the use of pressure reducing devices at individual service connections on a case by case basis, if it can be demonstrated that higher pressures in portions of the distribution system are required for efficient system operation. If system modification will cause pressure to routinely exceed eighty (80) psi, or if a check valve or an individual pressure reducing device is added to the service line, the water system owner shall notify affected customers. Notification may include reasons for the elevated pressure, problems or damage that elevated pressure can inflict on appliances or plumbing systems, and suggested procedures or mitigation efforts affected property owners may initiate to minimize problems or damage. (3-24-22)

vii. The Department may allow the installation of booster pump systems at individual service connections on a case by case basis. However, such an installation may only occur with the full knowledge and agreement of the public water system, including assurance by the water system that the individual booster pump will cause no adverse effects on system operation. (3-24-22)

viii. For elevated storage tanks, pressure calculations during peak hour demand shall be based on the lowest water level after both operational storage and equalization storage have been exhausted. Pressure calculations during fire flow demands shall be based on the lowest water level after operational storage, equalization storage, and fire suppression storage have been exhausted. (3-24-22)

ix. For hydropneumatic tanks, pressure calculations shall be based on the lowest pressure of the pressure cycle and this requirement shall be noted in the operation and maintenance manual. (3-24-22)

c. Fire Flows. Any public water system designed to provide fire flows shall ensure that such flows are compatible with the water demand of existing and planned fire-fighting equipment and fire fighting practices in the area served by the system. (3-24-22)

d. Irrigation Flows. (3-24-22)
i. Any public water system constructed after November 1, 1977, shall be capable of providing water for uncontrolled, simultaneous foreseeable irrigation demand, which shall include all acreage that the system is designed to irrigate. (3-24-22)
(1) The Department must concur with assumptions regarding the acreage to be irrigated. In general, an assumption that no outside watering will occur is considered unsound and is unlikely to be approved. (3-24-22)

(2) An assumption of minimal outside watering, as in recreational subdivisions, may be acceptable if design flows are adequate for maintenance of "green zones" for protection against wildland fire. (3-24-22)

ii. The requirement of Subsection 552.01.d.i. may be modified by the Department if: (3-24-22)
(1) A separate irrigation system is provided; or (3-24-22)

(2) The supplier of water can regulate the rate of irrigation through its police powers, and the water system is designed to accommodate a regulated rate of irrigation flow. The Department may require the water system to submit a legal opinion addressing the enforceability of such police powers. (3-24-22)

iii. If a separate non-potable irrigation system is provided for the consumers, all mains, hydrants and appurtenances shall be easily identified as non-potable. The Department must concur with a plan to ensure that each new potable water service is not cross-connected with the irrigation system. (3-24-22)

02. Ground Water. (3-24-22)

a. Public water systems constructed after July 1, 1985, and supplied by ground water, shall treat water within the system by disinfection if the ground water source is not protected from contamination. (3-24-22)

b. The Department may, in its discretion, require disinfection for any existing public water system supplied by ground water if the system has repeated coliform present samples or E.coli MCL exceedances, and if the system does not appear adequately protected from contamination. Adequate protection will be determined based upon at least the following factors: (3-24-22)
i. Location of possible sources of contamination; (3-24-22)

ii. Size of the well lot; (3-24-22)

iii. Depth of the source of water; (3-24-22)

iv. Bacteriological quality of the aquifer; (3-24-22)

v. Geological characteristics of the area; and (3-24-22)

vi. Adequacy of development of the source. (3-24-22)

03. Operating Criteria. The operating criteria for systems that provide filtration shall be as follows: (3-24-22)

a. A project specific operation and maintenance manual shall be provided as required in Subsection 501.12. See definition of Operation and Maintenance Manual in Section 003 for the typical contents of an operation and maintenance manual and the included operations plan. For the operations plan in the operation and maintenance manual, additional guidance for several types of filtration systems can be found in the Department's SWTR Compliance Guidance referenced in Subsection 002.02. (3-24-22)

b. The system shall conduct monitoring specified by the Department before serving water to the public in order to protect the health of consumers served by the system. (3-24-22)

c. New treatment facilities shall be operated in accordance with Subsection 552.03.a., and the system shall conduct monitoring specified by the Department for a trial period specified by the Department before serving water to the public in order to protect the health of consumers served by the system. (3-24-22)

04. Chlorination. Systems that regularly add chlorine to their water are subject to the provisions of Section 320. Systems using surface water or ground water under the direct influence of surface water, are subject to the disinfection requirements of Sections 300 and 518. (3-24-22)

a. Systems using only ground water that add chlorine for the purpose of disinfection, as defined in Section 003, are subject to the following requirements: (3-24-22)
i. Chlorinator and chlorine contact tank capacity shall be such that the system is able to demonstrate that it is routinely achieving four (4) logs (ninety-nine point ninety-nine percent) (99.99%)) inactivation/removal of viruses. The required effective contact time will be specified by the Department. This condition must be attainable even when the plant design capacity coincides with anticipated maximum chlorine demands. (3-24-22)

ii. A detectable chlorine residual shall be maintained throughout the distribution system. (3-24-22)

iii. Automatic proportioning chlorinators are required where the rate of flow or chlorine demand is not reasonably constant. (3-24-22)

iv. Analysis for free chlorine residual shall be conducted at a location at or prior to the first service connection at least daily and records of these analyses shall be kept by the supplier of water for at least one (1) year. A report of all daily chlorine residual measurements for each calendar month shall be submitted to the Department no later than the tenth day of the following month. The frequency of measuring free chlorine residuals shall be sufficient to detect variations in chlorine demand or changes in water flow. (3-24-22)

v. If gas chlorination equipment is provided, a separate and ventilated room is required. (3-24-22)

vi. The Department may, in its discretion, require a treatment rate higher than that specified in Subsection 552.04.a.i. (3-24-22)

vii. When chlorine gas is used, chlorine leak detection devices and safety equipment shall be provided and equipped with both an audible alarm and a warning light. (3-24-22)

viii. The Department may require redundant chlorine pumping capabilities with automatic switchover for systems with documented source water contamination problems and that lack adequate storage to supply the system during a pump failure. (3-24-22)

b. Systems using only ground water that add chlorine for the purpose of maintaining a disinfectant residual in the distribution system, when the source(s) is not at risk of microbial contamination, are subject to the following requirements: (3-24-22)
i. Automatic proportioning chlorinators are required where the rate of flow or chlorine demand is not reasonably constant. (3-24-22)

ii. Analysis for free chlorine residual shall be made at a frequency that is sufficient to detect variations in chlorine demand or changes in water flow. (3-24-22)

c. Systems using only ground water that add chlorine for other purposes, such as oxidation of metals or taste and odor control, when the source(s) is known to be free of microbial contamination, must ensure that chlorine residual entering the distribution system after treatment is less than four (4.0) mg/L. The requirements in Subsection 552.04.b.ii. also apply if the system maintains a chlorine residual in the distribution system. (3-24-22)

05. Fluoridation. (3-24-22)

a. Commercial sodium fluoride, sodium silico fluoride and hydrofluosilicic acid which conform to the applicable American Water Works Association (AWWA) Standards, incorporated by reference into these rules at Subsection 002.01, are acceptable. Use of other chemicals shall be specifically approved by the Department. (3-24-22)

b. Fluoride compounds shall be stored in covered or unopened shipping containers. (3-24-22)

c. Provisions shall be made to minimize the quantity of fluoride dust. Empty bags, drums, or barrels shall be disposed of in a manner that will minimize exposure to fluoride dusts. (3-24-22)

d. Daily records of flow and amounts of fluoride added shall be kept. An analysis for fluoride in finished water shall be made at least weekly. Records of these analyses shall be kept by the supplier of water for five (5) years. (3-24-22)

06. Cross Connection Control Program - Community Water Systems. The water purveyor is responsible through its cross connection control program to take reasonable and prudent measures to protect the water system against contamination and pollution from cross connections through premises isolation, internal or in-plant isolation, fixture protection, or some combination of premises isolation, internal isolation, and fixture protection. Pursuant to Section 543, all suppliers of water for community water systems shall implement a cross connection control program to prevent the entrance to the system of materials known to be toxic or hazardous. The water purveyor is responsible to enforce the system's cross connection control program. The program will at a minimum include: (3-24-22)

a. An inspection program to locate cross connections and determine required suitable protection. For new connections, suitable protection must be installed prior to providing water service. (3-24-22)

b. Required installation and operation of adequate backflow prevention assemblies. Appropriate and adequate backflow prevention assembly types for various facilities, fixtures, equipment, and uses of water should be selected from the AWWA Pacific Northwest Section Cross Connection Control Manual, the Uniform Plumbing Code, the AWWA Recommended Practice for Backflow Prevention and Cross Connection Control (M14), the USC Foundation Manual of Cross Connection Control, or other sources deemed acceptable by the Department. The assemblies must meet the requirements of Section 543 and comply with local ordinances. (3-24-22)

c. Annual inspections and testing of all installed backflow prevention assemblies by a tester licensed by a licensing authority recognized by the Department. Testing shall be done in accordance with the test procedures published by the University of Southern California Foundation for Cross-Connection Control and Hydraulic Research. See the USC Foundation Manual of Cross-Connection Control referenced in Subsection 002.02. (3-24-22)

d. Discontinuance of service to any structure, facility, or premises where suitable backflow protection has not been provided for a cross connection. (3-24-22)

e. Assemblies that cannot pass annual tests or those found to be defective shall be repaired, replaced, or isolated within ten (10) business days. If the failed assembly cannot be repaired, replaced, or isolated within ten (10) business days, water service to the failed assembly shall be discontinued. (3-24-22)

07. Cross Connection Control - Non-Community Water Systems. All suppliers of water for noncommunity water systems shall ensure that cross connections do not exist or are isolated from the potable water system by an approved backflow prevention assembly. Backflow prevention assemblies shall be inspected and tested annually for functionality by an Idaho licensed tester, as specified in Subsections 552.06.c. and 552.06.e. (3-24-22)

08. Start-up Procedures For Seasonal Systems Subject To Subsections 100.01.a., c., and d. (3-24-22)

a. All seasonal system owners and operators must demonstrate completion of a Department approved start-up procedure, including start-up sampling, prior to serving water to the public. The system owner or operator must submit information on a Department provided or approved form that includes a statement certifying that the system owner or operator followed proper start-up procedures. The form shall be submitted to the Department within 30 (thirty) days following the system's start-up date. (3-24-22)

b. The Department may exempt any seasonal system from Subsection 552.08.a. if the entire distribution system remains pressurized during the entire period that the system is not operating, except that the systems that monitor less frequently than monthly must still monitor during the vulnerable period designated by the Department. The Department may exempt a seasonal system from Subsection 552.08.a. if the owner or operator of the system meets all of the following conditions: (3-24-22)
i. Requests an exemption in writing to the Department for approval; (3-24-22)

ii. Demonstrates a clean compliance history as defined in Section 003 for a minimum of five (5) years; (3-24-22)

iii. Has no uncorrected significant deficiencies from the most recent sanitary survey; and (3-24-22)

iv. Total coliform samples submitted to a certified laboratory within 30 (thirty) days prior to serving water to the public demonstrate the absence of total coliform. (3-24-22)

Disclaimer: These regulations may not be the most recent version. Idaho may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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