Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.531 - FACILITY AND DESIGN STANDARDS: DESIGN STANDARDS FOR CHEMICAL APPLICATION

i. Feeders may be manually or automatically controlled, with automatic controls being designed so as to allow override by manual controls. (3-24-22)

ii. Chemical feeders shall be controlled by a flow sensing device so that injection of the chemicals will not continue when the flow of water stops. (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. A means to measure water flow must be provided in order to determine chemical feed rates. (3-24-22)

v. Provisions shall be made for measuring the quantities of chemicals used. (3-24-22)

vi. Weighing scales shall be provided for weighing cylinders at all plants utilizing chlorine gas, fluoride solution feed. (3-24-22)

vii. Weighing scales shall be capable of providing reasonable precision in relation to average daily dose. (3-24-22)

viii. Where conditions warrant, for example with rapidly fluctuating intake turbidity, coagulant and coagulant aid addition may be made according to turbidity, streaming current or other sensed parameter. (3-24-22)

i. The service water lines discharging to solution tanks shall be properly protected from backflow. (3-24-22)

ii. No direct connection exists between any sewer and a drain or overflow from the feeder, solution chamber or tank by providing that all drains terminate at least six (6) inches or two pipe diameters, whichever is greater, above the overflow rim of a receiving sump, conduit or waste receptacle. (3-24-22)

i. Ample in quantity and adequate in pressure. (3-24-22)

ii. Provided with means for measurement when preparing specific solution concentrations by dilution. (3-24-22)

iii. Properly treated for hardness, when necessary. (3-24-22)

iv. Properly protected against backflow. (3-24-22)

v. Obtained from a location sufficiently downstream of any chemical feed point to assure adequate mixing. (3-24-22)

i. Storage tanks and pipelines for liquid chemicals shall be specified for use with individual chemicals and not used for different chemicals. Off-loading areas must be clearly labeled to prevent accidental crosscontamination. (3-24-22)

ii. Chemicals shall be stored in covered or unopened shipping containers, unless the chemical is transferred into an approved storage unit. (3-24-22)

i. A means which is consistent with the nature of the chemical solution shall be provided in a solution tank to maintain a uniform strength of solution. Continuous agitation shall be provided to maintain slurries in suspension. (3-24-22)

ii. Means shall be provided to measure the liquid level in the tank. (3-24-22)

iii. Bulk liquid storage tanks shall be kept covered. Bulk liquid storage tanks with access openings shall have such openings curbed and fitted with overhanging covers. (3-24-22)

iv. Subsurface locations for bulk liquid storage tanks shall be free from sources of possible contamination, and assure positive drainage for ground waters, accumulated water, chemical spills and overflows. (3-24-22)

v. Bulk liquid storage tanks shall be vented, but shall not vent through vents common with day tanks. Acid storage tanks must be vented to the outside atmosphere, but not through vents in common with day tanks. (3-24-22)

vi. Each bulk liquid storage tank shall be provided with a valved drain, protected against backflow. (3-24-22)

vii. Bulk liquid storage tanks shall have an overflow that is turned downward with the end screened with a twenty-four (24) mesh or similar non-corrodible screen, have a free fall discharge, and be located where noticeable. (3-24-22)

viii. Bulk liquid storage tanks shall be provided with secondary containment so that chemicals from equipment failure, spillage, or accidental drainage shall be fully contained. A common receiving basin may be provided for each group of compatible chemicals. The bulk liquid storage tank basin or the common receiving basin shall provide a secondary containment volume sufficient to hold one hundred ten percent (110%) of the volume of the largest storage tank. Piping shall be designed to minimize or contain chemical spills in the event of pipe ruptures. (3-24-22)

ix. Where chemical feed is necessary for the protection of the supply, a means to assure continuity of chemical supply while servicing a bulk liquid storage tank shall be provided. (3-24-22)

i. Day tanks shall be provided where bulk storage of liquid chemicals are provided. The Department may allow chemicals to be fed directly from shipping containers no larger than fifty-five (55) gallons. (3-24-22)

ii. Day tanks shall meet all the requirements of Subsection 531.02.j., with the exception of Subsection 531.02.j.viii. Shipping containers do not require overflow pipes or drains as required by Subsection 531.02.j. and are not subject to the requirements of Subsection 531.02j.viii. (3-24-22)

iii. Where feasible, secondary containment shall be provided so that chemicals from equipment failure, spillage, or accidental drainage of day tanks shall be fully contained. A common receiving basin may be provided for each group of compatible chemicals. The common receiving basin shall provide a secondary containment volume sufficient to hold the volume of the largest storage tank. If secondary containment is not feasible, day tanks shall be located and protective curbings provided so that chemicals from equipment failure, spillage, or accidental drainage of day tanks shall not enter the water in conduits, treatment, or storage basins. Secondary containment is not required for a day tank if an Idaho licensed professional engineer demonstrates to the Department that the chemical concentration and volume, if spilled, will not be a safety hazard to employees, will not be hazardous to the public health, and will not harm the environment. (3-24-22)

iv. Day tanks and the tank refilling line entry points shall be clearly labeled with the name of the chemical contained. (3-24-22)

i. Each storage room shall be enclosed and separated from other operating areas. They shall be constructed in such a manner that all openings between the chlorine room and the remainder of the plant are sealed, and provided with doors equipped with panic hardware, assuring ready means of exit and opening outward only to the building exterior. (3-24-22)

ii. Each room shall be provided with a shatter resistant inspection window installed in an interior wall. (3-24-22)

iii. Each room shall have a ventilating fan with a capacity which provides one (1) complete air change per minute when the room is occupied. Where this is not appropriate due to the size of the room, a lesser rate may be allowed by the Department on a site specific basis. (3-24-22)

iv. The ventilating fan shall 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 to any rooms or structures. Air inlets shall be through louvers near the ceiling. (3-24-22)

v. Louvers for chlorine room air intake and exhaust shall facilitate airtight closure. (3-24-22)

vi. Separate switches for the fan and lights shall be located outside of the chlorine room and at the inspection window. Outside switches shall be protected from vandalism. A signal light indicating fan operation shall be provided at each entrance when the fan can be controlled from more than one (1) point. (3-24-22)

vii. Vents from feeders and storage shall discharge to the outside atmosphere, above grade. (3-24-22)

viii. Where provided, floor drains shall discharge to the outside of the building and shall not be connected to any internal drainage systems or external drainage systems unless the external drainage systems drain to an approved discharge point. (3-24-22)

ix. Chlorinator rooms shall be heated to sixty degrees Fahrenheit (60°F) and be protected from excessive heat. Cylinders and gas lines shall be protected from temperatures above that of the feed equipment. (3-24-22)

x. Pressurized chlorine feed lines shall not carry chlorine gas beyond the chlorinator room. (3-24-22)

xi. Critical isolation valves shall be conspicuously marked and access kept unobstructed. (3-24-22)

xii. All chlorine rooms, buildings, and areas shall be posted with a prominent danger sign warning of the presence of chlorine. (3-24-22)

xiii. Full and empty cylinders of chlorine gas shall be isolated from operating areas and stored in definitely assigned places away from elevators, stairs, or gangways. They shall be restrained in position to prevent being knocked over or damaged by passing or falling objects. In addition, they shall be stored in rooms separate from ammonia storage, out of direct sunlight, and at least twenty (20) feet from highly combustible materials. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards. (3-24-22)

i. Chlorite (sodium chlorite) shall be stored by itself in a separate room. It must be stored away from organic materials. The storage structure shall be constructed of noncombustible materials. If the storage structure must be located in an area where a fire may occur, water must be available to keep the sodium chlorite area cool enough to prevent heat-induced explosive decomposition of the chlorite. (3-24-22)

ii. Care shall be taken to prevent spillage. An emergency plan of operation shall be available for the clean up of any spillage. Storage drums shall be thoroughly flushed prior to recycling or disposal. (3-24-22)

i. Pressurized ammonia feed lines shall be restricted to the ammonia room. (3-24-22)

ii. An emergency air exhaust system, as described in Subsection 531.04.a., but with an elevated intake, shall be provided in the ammonia storage room. (3-24-22)

iii. Leak detection systems shall be fitted in all areas through which ammonia is piped. (3-24-22)

iv. Special vacuum breaker/regulator provisions must be made to avoid potentially violent results of backflow of water into cylinders or storage tanks. (3-24-22)

v. Consideration shall be given to the provision of an emergency gas scrubber capable of absorbing the entire contents of the largest ammonia storage unit whenever there is a risk to the public as a result of potential ammonia leaks. (3-24-22)

i. At least one pair of rubber gloves, a dust respirator of a type certified by NIOSH for toxic dusts, an apron or other protective clothing, and goggles or face mask shall be provided for each operator. (3-24-22)

ii. A deluge shower and eyewashing device shall be installed where strong acids and alkalis are used or stored. A water holding tank that will allow water to come to room temperature shall be installed in the water line feeding the deluge shower and eyewashing device. Other methods of water tempering will be considered on an individual basis. (3-24-22)

iii. For chemicals other than strong acids and alkalis, an appropriate eye washing device or station shall be provided. (3-24-22)

iv. Other protective equipment shall be provided as necessary. (3-24-22)

i. Hypochlorite shall be stored in the original shipping containers or in hypochlorite compatible containers. Storage containers or tanks shall be sited out of the sunlight in a cool and ventilated area. (3-24-22)

ii. Stored hypochlorite shall be pumped undiluted to the point of addition. Where dilution is unavoidable, deionized or softened water shall be used. (3-24-22)

iii. Storage areas, tanks, and pipe work shall be designed to avoid the possibility of uncontrolled discharges and a sufficient amount of appropriately selected spill absorbent shall be stored on-site. (3-24-22)

iv. Hypochlorite feeders shall be positive displacement pumps with compatible materials for wetted surfaces. (3-24-22)

v. To avoid air locking in smaller installations, small diameter suction lines shall be used with foot valves and degassing pump heads. In larger installations flooded suction shall be used with pipe work arranged to ease escape of gas bubbles. Calibration tubes or mass flow monitors which allow for direct physical checking of actual feed rates shall be fitted. (3-24-22)

vi. Injectors shall be made removable for regular cleaning where hard water is to be treated. (3-24-22)

i. A corrosion resistant, closed, unpressurized tank shall be used for bulk storage, vented through an inert liquid trap to a high point outside and an incompatible connector, or lockout provisions shall be made to prevent accidental addition of other chemicals to the storage tank. (3-24-22)

ii. The storage tank shall be designed to avoid conditions where temperature increases cause the ammonia vapor pressure over the aqua ammonia to exceed atmospheric pressure. This capability can be provided by cooling/refrigeration or diluting or mixing the contents with water without opening the system. (3-24-22)

iii. The aqua ammonia shall be conveyed direct from storage to the treated water stream injector without the use of a carrier water stream unless the carrier stream is softened. (3-24-22)

iv. The point of delivery to the main water stream shall be placed in a region of turbulent water flow. (3-24-22)

v. Provisions shall be made for easy access for removal of calcium scale deposits from the injector. (3-24-22)