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Virginia Administrative Code (Last Updated: January 10, 2017) |
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Title 12. Health |
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Agency 5. Department of Health |
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Chapter 590. Waterworks Regulations |
Section 1080. General
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Article 5. Finished Water Storage Structures
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 available American Water Works Association 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.
A. Location of finished water storage facilities.
1. The bottom of ground level reservoirs, storage tanks and standpipes should be placed at the normal ground surface.
2. Where the bottom must be below normal ground surface, it shall be placed above the groundwater table. Sewers, drains, standing water, and similar sources of contamination shall be kept at least 50 feet from the reservoir. AWWA approved water pipe, pressure tested in place without leakage, shall be used for gravity sewers at lesser separations.
3. The top of all storage facilities shall not be less than two feet above the normal ground surface and shall be above the 100-year flood level. Clearwells constructed under filters may be excepted from this requirement when the total design gives the same protection.
B. All new finished water storage structures shall have suitable watertight roofs or covers which exclude birds, animals, insects, and dust.
C. No drain on a water storage structure shall have a direct connection to a sewer or storm drain.
All finished water storage structures shall be equipped with separate drains discharging to the atmosphere. Drainage of finished water storage structures to the distribution system through inlet and outlet piping shall not be allowed.
D. The overflow pipe of a finished water storage structure shall be brought down near the ground surface where any discharge will be visible and into a drainage inlet structure or a splash plate which will divert the overflow away from the storage structure. No overflow may be connected directly to a sewer or storm drain.
1. When an internal overflow pipe is used it shall be located in the access tube.
2. The overflow of a ground level finished water storage structure shall be high enough above normal or graded ground surface to prevent the entrance of surface water.
3. All nonpressure type finished water storage structures shall be provided with a downward discharging screened overflow.
E. Finished water storage structures shall be designed with convenient access to the interior for cleaning and maintenance. Manholes or scuttles above the waterline shall be:
1. Framed at least four inches, preferably six inches, above the surface of the roof at the opening; on ground level structures, manholes should be elevated 24 to 36 inches above the top or covering sod;
2. Fitted with a solid watertight cover which overlaps the framed opening and extends vertically down around the frame at leas two inches (shoebox type);
3. Hinged at one side; and
4. Fitted with a locking device.
F. Finished water storage structures shall be vented by separate vent structures. Open construction between the side wall and roof is not permissable.
1. Vents shall prevent the entrance of surface water.
2. Vents shall exclude birds and animals.
3. Vents shall exclude insects and dust, as much as this function can be compatible with effective venting, for elevated tanks and standpipes, four-mesh noncorrodible screen may be used.
4. Vents on ground level structures shall terminate in an inverted U construction the opening of which is 24 to 36 inches above the roof or sod and is covered with noncorrodible screen cloth to exclude insects.
G. The roof and sidewalls of all structures must be watertight with no openings except properly constructed vents, manholes, overflows, risers, drains, pump mountings, control ports, or piping for inflow and outflow.
1. Any pipes running through the roof or sidewall of a finished water storage structure must be welded or properly gasketed in metal tanks or should be connected to standard wall castings which were poured in place during the forming of a concrete structure; these wall castings shall have flanges imbedded in the concrete.
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 and shoebox type cover to prevent the access of surface water into the structure.
3. Valves and controls shall be located outside the storage structure so that valve stems and similar projections will not pass through the roof or top of the structure.
H. The roof or cover of the storage structure should be well drained, but downspout pipes shall not enter or pass through the reservoir.
I. The safety of employees shall be considered in the design of the storage structure. As a minimum, such matters shall conform to pertinent building codes, laws, and regulations of the area where the reservoir is constructed.
1. Ladders, ladder guards, balcony railings, and safe location of entrance hatches shall be provided.
2. Elevated tanks with riser pipes over eight inches in diameter shall have protective bars over the riser opening inside the tank.
J. All finished water storage structures and their appurtenances, especially the riser pipes, overflows, and vents, shall be designed to prevent freezing which will interfere with proper functioning.
K. Every catwalk over finished water in a storage structure shall have a solid floor with raised edges so designed that shoe scrapings and dirt will not fall into the water.
L. The area surrounding a ground level structure should be graded in a manner that will prevent surface water from standing within 50 feet of the structure.
M. Proper protection should be given to metal surfaces by paints or other protective coatings, by cathodic protective devices, or both. Paint systems consistent with the most current available American Water Works Association standards and otherwise acceptable to the division shall be used. Cathodic protection should be designed and installed by competent technical personnel.
N. All finished water storage facilities shall be cleaned to remove all dirt and loose materials prior to disinfection of the structure. Only potable water shall be used to clean and rinse the water storage facilities. All equipment including brooms, brushes, spray equipment and workmen's boots shall be disinfected before they are used to clean the storage facilities.
O. All finished water storage facilities shall be satisfactorily disinfected prior to being placed in operation. The disinfection of the storage facilities shall be repeated until it is determined, by bacteriological testing, that the water is free of coliform bacteria.
1. One of the following disinfection methods shall be used. Other methods of disinfection may be approved on a case-by-case basis by the division.
a. The tank shall be filled to the overflow level with potable water to which enough chlorine has been added to produce an initial chlorine concentration of 50 mg/L in the full tank. The full tank should stand for 24 hours; however, in no case shall it stand less than six hours. At the end of the holding period, the chlorinated water shall be drained to waste, the tank refilled with potable water, and tested for satisfactory bacteriological quality before placing the tank in service.
b. All interior surfaces of the tank shall have applied a chlorine solution containing at least 200 mg/L of free available chlorine. The chlorine solution shall be applied with either spray equipment or brushes. Any equipment used to apply the chlorine solution shall either be new or previously used only for disinfection purposes. The chlorine solution shall remain in contact with the tank surfaces for at least 30 minutes. The tank shall then be filled with potable water to the overflow level and tested for satisfactory bacteriological quality before placing the tank in service; or
c. Potable water containing a free chlorine residual of 50 mg/L shall be placed in the tank to such a depth that when the tank is filled, the resulting chlorine concentration in the water will be at least two mg/L. The water containing 50 mg/L of chlorine shall stand in the tank for 24 hours. The tank shall then be filled with potable water and allowed to stand for 24 additional hours. At the end of the second 24 hour period, the chlorine residual shall be at least two mg/L. After analyses of the water for satisfactory bacteriological quality, the tank may be placed in service without draining the water used to disinfect it.
2. Testing of the water following disinfection shall be in accordance with 12VAC5-590-800 C.
Historical Notes
Derived from VR355-18-011.01 § 3.45, eff. August 1, 1991.