Current through Register Vol. XLI, No. 45, November 8, 2024
Section 64-77-9 - Finished Water Storage9.1. General. -- The materials and designs used for finished water storage structures shall provide stability and durability as well as protect the quality of the stored water. Steel structures shall follow the current AWWA standards concerning steel tanks, standpipes, reservoirs, and elevated tanks wherever they are applicable. Other materials of construction are acceptable when properly designed to meet the requirements of this section. 9.1.a. Sizing. -- Storage facilities shall have sufficient capacity, as determined from engineering studies, to meet domestic, commercial and industrial demands, and where fire protection is provided, fire flow demands. 9.1.a.1. Fire flow requirements established by the ISO shall be satisfied where fire protection is provided.9.1.a.2. The minimum storage capacity (or equivalent capacity) for systems providing fire protection shall be equal to twice the average daily demand of one hundred fifty (150) gallons per customer per day plus fire flow unless it can be demonstrated that the supply capacity of the system is sufficient to warrant less. This requirement may be reduced when the source and treatment facilities have sufficient capacity with standby power to supplement peak demands of the system.9.1.a.3. A recommended storage capacity for community and non-community, non-transient public water systems not providing fire protection shall be equal to twice the average daily demand of one hundred fifty (150) gallons per customer per day.9.1.b. Location of ground-level reservoirs. -- The bottom of reservoirs and standpipes shall be placed at the normal ground surface and shall be above the one hundred (100) year flood level. When the bottom is below normal ground surface, it shall be placed above the groundwater table. At least fifty per cent (50%) of the water depth of the reservoir may be above grade. Sewers, drains, standing water, and similar sources of possible contamination shall be kept at least fifty (50) feet from the reservoir. A water main pipe, pressure tested in place to fifty (50) pounds per square inch without leakage, may be located from twenty (20) to fifty (50) feet from a sewer, but under no circumstances shall it be located within twenty (20) feet of a sewer. The top of a partially buried storage structure shall be at least two (2) feet above normal ground surface. Clearwells constructed under filters may be excepted from this requirement when the design provides adequate protection from contamination.
9.1.c. Protection. -- All finished water storage structures shall have suitable watertight roofs and screened vents that exclude birds, animals, insects, and excessive dust. The installation of appurtenances, such as antenna, shall be done in a manner that ensures no damage to the tank, coatings or water quality.9.1.d. Protection from trespassers. -- Fencing, locks on access manholes, and other necessary precautions shall be provided to prevent trespassing, vandalism and sabotage, including the installation of high strength locks or lock covers to prevent direct cutting of a lock, if possible.9.1.e. Drains. -- No drain on a water storage structure may have a direct connection to a sewer or storm drain. The design shall allow draining the storage facility for cleaning or maintenance without causing loss of pressure in the distribution system.9.1.f. Overflow. -- All water storage structures shall be provided with an overflow that is brought down to an elevation between twelve (12) and twenty-four (24) inches above the ground surface and that discharges over a drainage inlet structure or a splash plate. No overflow may be connected directly to a sewer or a storm drain. All overflow pipes shall be located so that any discharge is visible. 9.1.f.1. When an internal overflow pipe is used on elevated tanks, it shall be located in the access tube. For vertical drops on other types of storage facilities, the overflow pipe shall be located on the outside of the structure.9.1.f.2. The overflow of a ground-level structure shall open downward and be screened with twenty-four (24) mesh non-corrodible screen installed within the pipe at a location least susceptible to damage by vandalism.9.1.f.3. The overflow pipe shall be of sufficient diameter to permit waste of water in excess of the filling rate.9.1.g. Access. -- Finished water storage structures shall be designed with reasonably convenient access to the interior for cleaning and maintenance. Manholes above the water line: shall be framed at least four (4) inches, and preferably (6) six inches, above the surface of the roof at the opening; on ground-level structures, shall be elevated twenty-four (24) to thirty-six (36) inches above the top or covering sod; shall be fitted with a solid watertight cover that overlaps the framed opening and extends down around the frame at least two (2) inches; shall be hinged at one (1) side; and shall have a locking device.9.1.h. Vents. -- Finished water storage structures shall be vented. Overflows shall not be considered as vents. Open construction between the sidewall and roof is not permissible. Vents shall prevent the entrance of surface water and rainwater and shall exclude birds, animals and insects, as much as this function can be made compatible with effective venting. For elevated tanks and standpipes, four (4) mesh non-corrodible screen may be used. On ground-level structures, standpipes shall terminate in an inverted U construction with the opening twenty-four (24) to thirty-six (36) inches above the roof or sod and be covered with twenty-four (24) mesh non-corrodible screen installed within the pipe at a location least susceptible to vandalism.9.1.i. Roof and sidewall. -- The roof and sidewalls of all structures shall be watertight with no openings except properly constructed vents, manholes, overflows, risers, drains, pump mountings, control ports and piping for inflow and outflow. 9.1.i.1. Any pipes running through the roof or sidewall of a finished water storage structure shall be welded, or properly gasketed in metal tanks. In concrete tanks, these pipes shall be connected to standard wall castings that were poured in place during the forming of the concrete. These wall castings shall have seepage rings imbedded in the concrete.9.1.i.2. Openings in a storage structure roof or top, designed to accommodate control apparatus or pump columns, shall be curbed and sleeved with proper additional shielding to prevent the access of surface or floor drainage water into the structure.9.1.i.3. Valves and controls shall be located outside the storage structure so that the valve stems and similar projections do not pass through the roof or top of the reservoir.9.1.i.4. The roof of concrete reservoirs with an earthen cover shall be sloped to facilitate drainage. Consideration shall be given to installation of an impermeable membrane roof covering.9.1.i.5. Locks shall be provided on valve vaults where applicable.9.1.j. Drainage of roof. -- The roof of the storage structure shall be well drained. Downspout pipes shall not enter or pass through the reservoir. Parapets, or similar construction that would tend to hold water and snow on the roof, shall not be approved by the BPH unless adequate waterproofing and drainage are provided.9.1.k. Safety. -- The safety of employees shall be considered in the design of the storage structure. As a minimum, employee safety matters shall conform to pertinent laws and rules. 9.1.k.1. Ladders, ladder guards, balcony railings, and safely located entrance hatches shall be provided where applicable. Elevated tanks with riser pipes more than eight inches in diameter shall have protective bars over the riser openings inside the tank. Railings or handholds shall be provided on elevated tanks where persons transfer from the access tube to the water compartment. Confined space entry requirements shall be considered.9.1.l. Freezing. -- All finished water storage structures and their appurtenances, especially the riser pipes, overflows, and vents, shall be designed to prevent freezing that interferes with proper functioning. Equipment used for freeze protection that comes into contact with the potable water shall meet ANSI/NSF Standard 61 or be approved by the BPH. If a water circulation system is used, it is recommended that the circulation pipe be located separately from the riser pipe.9.1.m. Internal catwalk. -- Every catwalk over finished water in a storage structure shall have a solid floor with raised edges designed so that shoe scrapings and dirt do not fall into the water.9.1.n. Silt stop. -- The discharge pipes from all reservoirs shall be located in a manner that prevents the flow of sediment into the distribution system. Removable silt stops shall be provided.9.1.o. Grading. -- The area surrounding a ground-level structure shall be graded in a manner that prevents surface water from standing within fifty (50) feet.9.1.p. Painting and cathodic protection. -- Proper protection shall be given to metal surfaces by paints or other protective coatings, by cathodic protective devices, or by both. Paint systems shall be certified to conform to ANSI/NSF Standard 61: Drinking Water System Components - Health Effects. Interior paint shall be properly applied and cured. After curing, the coating shall not transfer any substance to the water that is toxic or cause tastes or odors. Prior to placing in service, an analysis for volatile organic compounds is advisable to establish that the coating is properly cured. Consideration shall be given to 100% solids coatings. Wax coatings for the tank interior shall not be used on new tanks. Recoating with a wax system is not allowed. Old wax coating shall be completely removed before using another coating. Cathodic protection shall be installed on below grade steel reservoirs and shall be designed and installed by competent technical personnel; a maintenance contract shall be provided.9.1.q. Disinfection. -- Finished water storage structures shall be disinfected in accordance with current AWWA Standard C652. Two (2) or more successive sets of samples, taken at twenty-four (24) hour intervals, shall be microbiologically satisfactory before the facility is placed into operation. Disposal of heavily chlorinated water from the tank disinfection process shall be in accordance with the requirements of the WVDEP. The disinfection procedure (AWWA C652 chlorination method 3, subsection 4.3.) that allows use of the chlorinated water held in the storage tank for disinfection purposes is not recommended. When that procedure is used, it is recommended that the initial heavily chlorinated water be properly disposed in order to prevent the release of water that may contain various chlorinated organic compounds into the distribution system.9.1.r. Provisions of Sampling. -- Smooth-nosed sampling taps shall be provided to facilitate collection of water samples for both bacteriologic and chemical analysis. The sampling tap(s) shall be easily accessible.9.2. Plant Storage. -- The applicable design standards for finished water storage shall be followed for plant storage. 9.2.a. Filter Washwater tanks. -- Filter washwater tanks shall be sized, in conjunction with available pump units and finished water storage, to provide the backwash water required. Consideration shall be given to the backwashing of several filters in rapid succession.9.2.b. Clearwell. -- Clearwell storage shall be sized, in conjunction with distribution system storage, to relieve the filters from having to follow fluctuations in water use and meet peak demands, including filter backwash water. When finished water storage is used to provide contact time for chlorine, special attention shall be given to size and baffling. To ensure adequate chlorine contact time in accordance with the West Virginia Bureau for Public Health rule, Public Water Systems, 64CSR3, sizing of the clearwell shall include extra volume to accommodate depletion of storage during the nighttime for intermittently operated filtration plants with automatic high service pumping from the clearwell during non-treatment hours. An overflow and vent shall be provided. A minimum of two (2) clearwell compartments shall be provided.9.2.c. Adjacent compartments. -- Finished water shall not be stored or conveyed in a compartment adjacent to untreated or partially treated water when the two compartments are separated by a single wall.9.2.d. Other treatment plant storage tanks. -- Receiving basins, detention basins, backwash reclaim tanks and pump wet wells for finished water shall be designed as finished water storage structures.9.3. Hydropneumatic Tanks. -- Hydropneumatic (pressure) tanks serving community and non-community, non-transient public water systems, when provided as the only storage facility, are acceptable only in very small service areas. Systems serving more than 150 living units shall have ground or elevated storage. Hydropneumatic tank storage is not permitted for fire protection purposes. Pressure tanks shall meet ASME code requirements or an equivalent requirement of state or local laws and rules of construction and installation of unfired pressure vessels. Non-ASME, factory-built hydropneumatic tanks may be allowed if approved by the BPH.9.3.a. Location. -- The tank shall be located above normal ground surface and be completely housed.9.3.b. Sizing. -- The capacity of the pumps in a hydropneumatic system shall be at least ten (10) times the average daily consumption rate. The gross volume of the hydropneumatic tank, in gallons, shall be at least ten (10) times the capacity of the largest pump, rated in gallons per minute. For example, a two hundred fifty (250) gallon per minute pump shall have a two thousand five hundred (2,500) gallon pressure tank, unless other measures, such as variable speed drives in conjunction with the pump motors are provided to meet the maximum demand. Sizing of hydropneumatic storage tanks shall consider the need for chlorine detention time, as applicable, independent of the storage requirements. If hydropneumatic tanks are considered for chlorine contact, separate inlet and outlet connectors at top and bottom of the tank are required.9.3.c. Piping. -- The hydropneumatic tank shall have bypass piping to permit operation of the system while it is being repaired or painted.9.3.d. Appurtenances. -- Each hydropneumatic tank shall have an access manhole, a drain and control equipment consisting of pressure gauge, water sight glass, automatic or manual air blow-off, a means for adding air, and pressure operated start-stop controls for the pumps. A pressure relief valve shall be installed and be capable of handling the full pumpage rate of flow at the pressure vessel design limit. Where practical the access manhole shall be twenty-four (24) inches in diameter.9.3.e. Coatings. -- The interior coating of all tanks shall meet ANSI/NSF Standard 61: Drinking Water System Components - Health Effects.9.4. Distribution Storage. -- The applicable design standards of subsection 9.1. of this rule shall be followed for distribution system storage. The minimum storage capacity (or equivalent capacity) for systems providing fire protection shall be equal to twice the average daily demand of one hundred fifty (150) gallons per customer per day plus fire flow unless it can be demonstrated that the supply capacity of the system is sufficient to warrant less. All tanks shall be controlled to provide an adequate turn-over of at least twenty percent (20%) of the total volume each twenty-four (24) hour period. The BPH may allow a variance to the minimum twenty percent (20%) turn-over requirement, if adequate justification is provided such as no distribution water quality violations, booster chlorination, etc. This may require a main line altitude valve or externally controlled valves. 9.4.a. Pressures. -- The maximum variation between high and low levels in standpipes or elevated storage structures providing pressure to a distribution system shall not exceed thirty (30) feet (thirteen (13) pounds per square inch). The minimum pressure in the distribution system shall be thirty (30) pounds per square inch under static conditions and twenty (20) pounds per square inch under all flow conditions. The normal working pressures of the distribution mains shall be designed based upon the pipe manufacturer's recommendations and the applicable AWWA standards for the type of pipe. Pressure regulating/pressure reducing valves shall be used to protect the distribution mains from excessive pressures. When static pressures in the distribution mains exceed one hundred thirty five (135) pounds per square inch, the utility shall have the option of installing pressure reducing valves on service lines or requiring (or recommending) the customer install and maintain a pressure reducing valve on the customer's service line.9.4.b. Drainage. -- Storage structures that provide pressure directly to the distribution system shall be designed so they can be isolated from the distribution system and drained for cleaning or maintenance without necessitating loss of pressure in the distribution system. The drain shall discharge to the ground surface with no direct connection to a sewer or storm drain.9.4.c. Level controls. -- Commercially available control systems shall be provided to maintain levels in distribution system storage structures for community and non-community, non-transient public water systems. Level indicating devices shall be provided at a central location. Pumps shall be controlled from tank levels with the signal transmitted by telemetering equipment when any appreciable head loss occurs in the distribution system between the source and the storage structure. Altitude valves or equivalent controls may be required for additional structures on the system. Overflow and low-level warnings or alarms shall be located at places in the community where they are under responsible surveillance twenty-four (24) hours a day.