(a) Design basis. The capacity of the water treatment or water production system shall be designed for the maximum daily demand at the design year. Where water use records are not available to establish water use, the equivalent per capita water use shall be at least 125 gpd (475 liters per day) and 340 gpd (1,285 liters per day) to size facilities for average and maximum daily water demand, respectively.
(b) Siting requirements. - (i) Location. Treatment facilities shall be located such that no sources of pollution may affect the quality of the water supply or treatment system. The facilities shall not be located within 500 feet of landfills, garbage dumps, or wastewater treatment systems.
- (ii) Flood protection. All treatment process structures, mechanical equipment, and electrical equipment shall be protected from the maximum flood of record or the 100-year flood, whichever is greater. The treatment facilities shall remain fully operational and accessible during the 100-year flood.
(c) Level of treatment. Treatment shall be provided to produce a potable water that is bacteriologically, chemically, radiologically, and physically safe as determined by the administrator. - (i) Surface supplies. Treatment shall include:
- (A) Chemical addition/coagulation, flocculation, sedimentation, filtration and disinfection; or
- (B) Where the raw water maximum turbidity is less than 50 TU and is not attributable to clay and maximum color is less than 30 TU, treatment facilities may include slow sand filtration and disinfection; or
- (C) Where the maximum monthly average raw water turbidity is less than 25 TU, the color is less than 30 TU and fecal coliform organisms are less than 100 mpn/100 ml, treatment facilities may be diatomaceous earth filters and disinfection.
- (ii) Groundwater supplies. Groundwater supply facilities shall provide disinfection equipment and connections, as a minimum.
(d) Hydraulic and treatment reliability. - (i) Multiple units. Treatment facilities with 100,000 gallons per day (gpd) (378.5 m3/day) capacity and over shall provide duplicate units, as a minimum, for chemical feed, flocculation, sedimentation, filtration and disinfection. Treatment facilities under 100,000 gpd (378.5 m3/day) capacity shall provide duplicate units as described above or may provide finished water system storage equal to twice the maximum daily demand.
- (ii) Multiple equipment. All treatment facility pumping shall provide the maximum daily flow with the largest single unit not in service. Finished water pumping in combination with finished water storage that floats on the distribution systems shall provide the maximum hour flow with the single largest unit not in service. When fire protection is provided, pumping and finished water storage that floats on the system shall provide the fire demand plus the maximum daily demand, or the maximum hour demand, whichever is greater.
- (iii) Alternative power source. Where the finished water storage volume that floats on the distribution system is not capable of supplying the maximum daily demand, an alternative power shall be provided for the finished water pumps. The combined finished water storage volume and pumping capacity supplied by alternative power shall be at least adequate to provide the maximum daily demand. Acceptable alternative power sources include an engine generator, engine drive pumps, or a second independent electrical supply.
(e) Housing. Process equipment, including filters and appurtenances, disinfection, chemical feed and storage, electrical and controls, and pipe galleries shall be housed.
(f) Electrical. - (i) Equipment location. Service transformers and other critical electrical equipment shall be located above the 100-year flood and above-grade. Transformers shall be located so that they are remote or protected by substantial barriers from traffic. Motor controls shall be located in superstructures and in rooms that do not contain corrosive atmospheres.
- (ii) Code requirements. Electrical design shall comply with the National Electrical Code as enacted and amended by the Wyoming Department of Fire Prevention and Electrical Safety. Areas in which the occurrence of explosive concentrations of hazardous gases, flammable fluids, or explosive dusts can occur shall be designed for hazardous locations in accordance with the National Electrical Code Class 1, Groups C and D, Division 1 locations.
(g) Structural. - (i) Construction materials. Construction materials shall be selected, apportioned, and/or protected to provide water tightness, corrosion protection, and resistance to weather variations.
- (ii) Coatings. Coatings used to protect structures, equipment, and piping shall be suitable for atmospheres containing moisture and low concentrations of chlorine. Surfaces exposed in chemical areas shall be protected from chemical attack. Paints shall not contain lead, mercury, or other toxic metals or chemicals.
- (iii) Geological conditions. Structural design shall consider the seismic zone, groundwater, and soil support. Soils investigations shall be made, or adequate previous soils investigations shall be available to develop structural design.
(h) Safety. The Wyoming Occupational Health and Safety (OHSA) Rules and Regulations shall be complied with. The following items shall also be provided: - (i) Instruction manuals. Instruction manuals shall be provided for all mechanical and electrical equipment describing operation, maintenance, and safety.
- (ii) Handrails. In addition to all Wyoming OHSA requirements, barriers around treatment basins shall be provided.
- (iii) Warning signs. Warning signs for pipes or hose bibs containing nontreated water, electrical hazards, mechanical hazards, chemical hazards, or other unsafe features shall be provided. Warning signs shall be permanently attached to the structure or appropriate equipment.
- (iv) Equipment guards. Shields to protect operators from rotating or moving machinery shall be provided.
- (v) Lighting. Provisions shall be made to light walkways, paths, and other accessways around basins, in buildings and on the site. All areas shall be lit in a manner that the failure of one lighting fixture will not cause an area to be dark, or the loss of power will not cause a room or enclosed area to be dark.
- (vi) Climate conditions. Design of facilities such as exposed stairs, walkways, and sidewalks shall include nonskid surfaces.
(i) Instrumentation. - (i) Metering. The treatment facility shall have a flow measuring device provided for raw water influent and clear well effluent. The accuracy of the device shall be at least plus or minus two percent of span.
- (ii) Type. All flow meters shall provide totalized flow. For plants with a maximum daily flow of 50,000 gpd (189 m3/d) or more, the meter shall also include recording of instantaneous flow rate.
- (iii) Controls. Automatic controls shall be designed to permit manual override.
- (iv) Alarms. High effluent turbidity and chlorine leaks (when chlorine gas is used) shall be alarmed at an attended location.
(j) Sample taps. Sample taps shall be provided so that water samples can be obtained from each water source and from appropriate locations in each unit operation of treatment. Taps shall be consistent with sampling needs and shall not be of the petcock type. Taps used for obtaining samples for bacteriological analysis shall be of the smooth-nosed type without interior or exterior threads, shall not be of the mixing type, and shall not have a screen, aerator, or other such appurtenance.
(k) Ventilation. All enclosed spaces shall be provided with forced ventilation, except pumping station wetwells or clearwells. In areas where there are open treatment units exposed to the room, ventilation shall be provided to limit relative humidity to less than 85 percent but not less than 6 air changes per hour. In electrical and equipment rooms, ventilation shall be provided to limit the temperature rise in the room to less than 15° F (8° C) above ambient, but not less than 6 air changes per hour. Rooms housing chlorine storage and/or feeders shall have provisions for exhausting the room contents in 2 minutes and continuous ventilation to provide not less than 12 air changes per hour.
(l) Dewatering of treatment units. All treatment units, channels, basins, clearwells and wetwells shall be provided with drains or sumps that facilitate draining the unit for access and maintenance. Drainage shall be to the process waste system, filter washwater system or sanitary sewer. Basin slabs shall be designed to successfully resist the hydrostatic uplift pressure or an area dewatering system shall be provided. Considerations must be given in structural design to long span breakage in basins designed to resist uplift.
(m) Cold weather protection. All equipment not required to be in or on open basins (such as clarifier drives and flocculator) shall be housed in heated, lighted, and ventilated structures. Structure entrances shall be above grade. Piping shall be buried below frost level, placed in heated structures, or provided with heat and insulated.
(n) Chemical storage. All chemical storage shall be housed or buried. Areas designated for storage of specific chemicals shall be separated from areas designated for other reactive chemicals. Liquid storage containers shall be isolated from other portions of the structure by a curb that will contain ruptured tank contents. Concrete floors, walls, and curbs in chemical storage and feed areas shall be coated to protect the concrete from aggressive chemicals. Floors in polymer feed and storage areas shall be provided with nonslip surfaces. Rooms for chlorine storage and feed equipment shall be gastight and be provided with entry from outdoors. All toxic chemical storage areas shall be provided with lighting and ventilation switched from outside the room near the door. All toxic chemical storage areas shall be provided with windows either in the door or near the door to permit viewing the room from outside. Explosive chemicals shall be stored to protect operations personnel and equipment from injury or damage.
(o) Facility water supply. The facility water supply service line and the plant finished water sample tap shall be supplied from a source of finished water at a point where all chemicals have been thoroughly mixed, and the required disinfectant contact time has been achieved. There shall be no cross-connections between the facility water supply service line and any piping, troughs, tanks, or other treatment units containing wastewater, treatment chemicals, raw or partially treated water. The potable plant water supply line shall have provisions to prevent backflow.
(p) Design capacities. The plant capacity shall include maximum daily water demand, filter backwash quantities, and industrial water use. In the absence of data, filter backwash quantity shall be five percent of the maximum daily demand.
(q) Monitoring equipment. Water treatment plants having a capacity of 0.5 mgd (1892.6 m3/d) or more shall be provided with continuous finished water turbidimeters (including recorders).
(r) Labels. All process piping shall be labeled to identify materials being conveyed.
020-12 Wyo. Code R. § 12-8