Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.518 - FACILITY AND DESIGN STANDARDS: ADDITIONAL DESIGN CRITERIA FOR SURFACE WATER TREATMENT
Current through August 31, 2023
Performance criteria for surface water treatment facilities are specified in National Primary Drinking Water Regulations, as set forth in Sections 300, 301, and 310 of these rules. Surface water treatment systems must comply with applicable general design requirements in Section 503. In addition, the following design requirements apply specifically to surface water treatment facilities: (3-24-22)
01. Engineering Design Requirements. The system shall ensure that filtration and disinfection facilities for surface water or ground water directly influenced by surface water sources are designed, constructed and operated in accordance with all applicable engineering practices designated by the Department. The design of the water treatment plant must consider the worst raw water quality conditions that are likely to occur during the life of the facility. (3-24-22)
02. Removal of Pathogens. Filtration facilities (excluding disinfection) shall be designed, constructed and operated to achieve at least two (2) log removal of Giardia lamblia cysts, two (2) log removal of Cryptosporidium oocysts, and one (1) log removal of viruses, except as allowed under Subsection 518.09.b. (3-24-22)
03. Disinfection. Disinfection facilities shall be designed, constructed and operated so as to achieve at least point five zero (0.50) log inactivation of Giardia lamblia cysts; and (3-24-22)
04. Enhanced Disinfection. Higher levels of disinfection than specified under Subsection 518.03 may be required by the Department in order to provide adequate protection against Giardia lamblia and viruses. (3-24-22)
05. Filter to Waste. For plants constructed after December 31, 1992, each filter unit must be capable of filter to waste. For plants constructed prior to December 31, 1992, each filter unit must be capable of filter to waste unless the system demonstrates through continuous turbidity monitoring or other means acceptable to the Department that water quality is not adversely affected following filter backwashing, cleaning or media replacement. (3-24-22)
06. Continuous Turbidity Monitoring. For conventional, direct, membrane, and diatomaceous earth filtration technology, equipment must be provided to continuously measure the turbidity of each filter unit. (3-24-22)
07. Continuous Monitoring of Disinfectant. Equipment must be provided and operated for continuous measurement of disinfectant residual prior to entry to the distribution system, unless the system serves fewer than three thousand three hundred (3,300) people. (3-24-22)
08. Continuous Operation Required. Diatomaceous earth filtration facilities shall include an alternate power source with automatic startup and alarm, or be designed in a manner to ensure continuous operation. (3-24-22)
09. Acceptable Technology. The purveyor shall select a filtration technology acceptable to the Department. (3-24-22)
10. Pilot Studies. The system shall conduct pilot studies in accordance with the following requirements and in accordance with Subsection 501.19 for all proposed filtration facilities and structural modifications to existing filtration facilities, unless the Department modifies the requirements in writing: (3-24-22)
11. Redundant Disinfection. Surface water systems constructed after July 1, 1985, are required to install redundant disinfection components or maintain a backup unit on site as required to maintain constant application of disinfectant whenever water is being delivered to the distribution system. (3-24-22)