Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 811 - Requirements For The Operation And Design Of Community Water Systems
Subchapter IX - Storage Facilities
Section NR 811.64 - Construction details

Universal Citation: WI Admin Code ยง NR 811.64

Current through August 26, 2024

(1) MATERIALS. Materials used in the construction of storage facilities shall meet all the following requirements:

(a) General requirements. 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. Unless the design engineer can justify the use of other materials, the department shall approve only steel, fiberglass, or concrete for use in a water storage facility. Porous materials, including wood and concrete block, may not be used.

(b) AWWA standards. Structures shall be constructed in accordance with the AWWA standards D100, D102, D103, D104, D110, D115, D120, and D130 concerning steel; concrete or fiberglass tanks, standpipes, reservoirs, and elevated tanks in effect at the time of construction wherever they are applicable.

(2) PROTECTION. Storage facilities shall be constructed and maintained to protect the water supply in accordance with the following requirements:

(a) General requirements. All water storage structures shall have watertight roofs or covers which exclude surface water, rain, snow, birds, animals, insects and dust.

(b) Installation of ancillary equipment. The installation of ancillary equipment, such as antennas, shall be done in a manner that ensures no damage to the tank, coatings, or water quality. Any damage that occurs to the tank during installation shall be corrected.

(c) Adjacent compartments. Finished water may not be stored or conveyed in a compartment adjacent to nonpotable water when the 2 compartments are only separated by a single wall. The department may waive this requirement for backwash water holding compartments meeting potable water reservoir construction on a case-by-case basis.

(d) Security. Locks on access manholes, fences and ladder cage bottoms and any other necessary measures shall be provided to prevent trespassing, vandalism and sabotage.

Note: The department recommends that intrusion alarms and/or motion sensors be installed as applicable and where feasible for elevated tank pedestal access doors and reservoir access hatches. The department recommends that high strength, cut resistant locks or lock covers be installed to prevent direct cutting of a lock.

(3) DRAINS. Drains for storage structures shall meet all the following requirements:

(a) General drain discharge requirements.
1. Piping used to drain water from a water storage structure shall discharge to the ground surface. The drain piping shall be brought down to within 12 to 24 inches of the ground surface and discharged with a free air break over a drainage inlet structure, splash pad or riprap.

2. Reservoir drains may not be directly connected to a storm sewer. A WPDES permit is required for any discharge with a free air break over a storm sewer manhole or through a valved connection to the overflow piping.

3. Reservoir drains may not be directly connected to a sanitary sewer. Water from drains may not be discharged to a sanitary sewer except on a temporary basis when the drain water contains sediment or chemicals used for cleaning, such as during temporary cleaning of water storage facilities.

(b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of drainage water shall be prevented.

(4) OVERFLOW. Each reservoir shall be provided with overflow piping meeting all the following requirements:

(a) General overflow discharge requirements.
1. 'Discharge.' The overflow pipe of a water storage structure shall terminate downward facing from horizontal, 45-degrees at a minimum of 12 to 24 inches above the final graded ground surface with a free air break over a drainage inlet structure, splash pad, or riprap. A WPDES permit is required for any discharge with a 12 to 24 inch free air break over a storm sewer manhole. Overflows may not discharge to a sanitary sewer.

2. 'Pipe diameter.' The overflow pipe shall be of sufficient diameter to permit wasting water in excess of the maximum filling rate.

3. 'Pipe material.' The overflow pipe shall be constructed of ductile iron, steel, or stainless steel.

4. 'Visibility.' All overflow pipes shall be located so that any discharge is visible.

5. 'Flapper.' If a metal flapper valve is used, a screen shall be provided in accordance with pars. (c) and (d).

6. 'Rubber duckbill valve.' If a rubber duckbill valve is used, a screen is not required. Provisions shall be included to prevent the duckbill from freezing shut.

7. 'Overflow location.' An internal overflow pipe on an elevated storage tank shall be located in the access tube and discharge in accordance with par. (a). Internal overflows are prohibited on standpipes, ground storage reservoirs, and ground level storage tanks.

(b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of overflow water shall be prohibited.

(c) Elevated tanks and standpipes. The overflow pipe shall be provided with a 4-mesh corrosion resistant screen installed within the pipe at a location least susceptible to damage by vandalism.

(d) Ground level structures.
1. Overflow pipes shall terminate downward facing 90-degrees at a minimum of 12 to 24 inches above the final graded ground surface.

2. The overflow shall be screened with 24-mesh corrosion resistant screen installed within the pipe at a location least susceptible to damage by vandalism.

3. Each reservoir chamber that can be isolated from the rest of the reservoir so that it can remain in service while other chambers are out of service shall be provided with its own overflow pipe terminating outside the reservoir in accordance with the requirements of subds. 1. and 2.

(5) INLET-OUTLET PIPING. Inlet and outlet piping to a storage structure shall meet all the following requirements:

(a) Pressure requirements. Inlet and outlet piping from a storage structure shall be under positive pressure at all times wherever practical and in conformance with s. NR 811.37 (1). The department may approve inlet piping that is not under positive pressure at all times on a case-by-case basis where the piping is exposed and located above grade.

(b) Pipe sizing. Piping shall be sized to accommodate design fill and removal rates including considerations for future improvements.

(6) BYPASS PIPING.

(a) Groundwater facilities.If the water system design is such that all water passes through one ground reservoir, there shall be bypass piping from the well pumps to the high lift pumps to allow the reservoir to be taken out of service for cleaning and maintenance. The department may waive this requirement if the well pumps can provide sufficient volume and pressure directly to the distribution system, if the well pumps and high lift pumps are greatly different in capacity, or if the reservoir is divided into multiple cells which can be independently removed from service. If CT is required, the department will approve bypass piping around reservoirs only if the required minimum CT can be met with the reservoir chamber or chambers out of service.

(b) Surface water facilities. If the water treatment plant design is such that all water passes through one ground reservoir, bypass piping or multiple cells shall be installed to allow the reservoir to be totally or partially taken out of service for cleaning and maintenance. The design shall provide for maintaining the required minimum CT while the reservoir is totally or partially out of service.

(7) ACCESS. Water storage structures shall be designed with reasonably convenient access for cleaning and maintenance. Manholes installed above the waterline shall meet the following requirements:

(a) Elevated storage structures and reservoirs covered by inhabitable structures. Manholes on elevated tanks, standpipes and reservoirs covered by inhabitable structures shall be framed a minimum of 4 inches above the surface of the roof. Manhole openings shall be fitted with a solid watertight cover. Manhole covers for elevated tanks shall overlap the framed opening and extend down around the frame a minimum of 2 inches. A compressible gasket shall be provided so that when the cover is closed it will provide a water tight seal around the manhole opening.

(b) Ground storage structures. On ground level structures, manholes shall be elevated no less than 24 inches above the top or covering sod. Manhole openings shall be fitted with a solid watertight cover that overlaps the framed opening and extends down around the frame a minimum of 2 inches. A compressible gasket shall be provided so that when the cover is closed it will provide a water tight seal around the manhole opening.

(c) Locks. Overlapping interior and exterior manhole covers shall be locked at all times except when being used by authorized personnel.

(d) Other openings. All other manholes, openings, or access ways shall be provided with watertight, bolted, and gasketed covers.

(8) VENTS. Water storage structures shall be vented to the atmosphere. Vent installations shall meet the following requirements:

(a) General requirements.
1. The overflow pipe shall not be considered a vent.

2. Open construction between the sidewalls and the roof to act as a vent is not allowed.

(b) Exclude contamination. Vents shall be constructed to:
1. Prevent the entrance of surface water, rain and snow as applicable.

2. Exclude birds and animals.

3. Exclude insects and dust to the extent this can be done while providing effective venting.

(c) Elevated tanks and standpipes. Vents installed on elevated tanks and standpipes shall terminate with a mushroom cap constructed with the opening at least 4 inches above the roof and shall be provided with a 4-mesh outer screen and 4- to 24-mesh inner screen constructed of corrosion resistant material installed within the pipe at a location protected from the environment. The mushroom cap shall be provided with an automatically resetting pressure-vacuum relief frost-proof mechanism. The skirted sides of mushroom caps shall totally cover any screens when viewing the cap from the side.

(d) Ground level structures. Vents installed on ground level structures shall terminate in a U-bend or mushroom cap constructed with the opening 24 to 36 inches above the roof or sod and covered with 24-mesh corrosion resistant screen installed within the pipe or cap at a location least susceptible to vandalism. The skirted sides of mushroom caps shall totally cover any screens when viewing the cap from the side.

(e) Size. Vents shall be sized to allow an air flow consistent with maximum water inflow and outflow rates.

(f) Materials of construction.
1. Vent pipes shall be constructed of ductile iron, steel, or stainless steel pipe.

2. Mushroom caps shall be constructed of steel, stainless steel, or aluminum.

3. Screens shall be constructed of stainless steel or aluminum.

4. Inner pallet screens of frost-proof mushroom cap vents shall be constructed of corrosion resistant material.

(9) SILT STOP. The discharge pipes from all water storage structures shall be located in a manner that will prevent the flow of sediment into the distribution system. Removable silt stops shall be required where feasible.

(10) ROOF AND SIDEWALLS. The roof and sidewalls of all storage structures shall be constructed to meet the following requirements:

(a) Watertight construction. 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, or piping for inflow and outflow.

(b) Sealed openings. Any pipes running through the roof, floor or sidewall of a finished water storage structure shall be sealed watertight. Openings for metal tanks shall be welded or properly gasketed. Pipes running through openings in a concrete structure shall be connected to a standard wall pipe or run through a wall sleeve which were poured in place during the formation of the structure. These wall pipes and wall sleeves shall be metal and have seepage rings embedded in the concrete. Pipes running through a wall sleeve shall be provided with a department approved watertight seal installed between the pipe and the wall sleeve.

(c) Roof curbing. Openings in a storage structure roof or top, designed to accommodate control apparatus, pump columns and other equipment, shall be provided with minimum 4-inch high curbing and sleeved with proper additional flashing to prevent the access of surface or floor drainage water to the structure.

(d) Installation of appurtenances. Valves and controls shall be located outside the storage structure so that valve stems and similar projections do not pass through the roof or top of the reservoir unless the department determines that this requirement need not be met to fulfill the other requirements of this chapter. The department may allow floor drain piping carrying graywater or a trench drain carrying graywater, electrical conduits, water service piping, and chemical feed piping to be encased in a concrete reservoir roof. Other appurtenances, including drain piping carrying blackwater, shall not be encased in a concrete reservoir roof. Toilets shall not be located above the reservoir roof.

(e) Earth cover over reservoirs.
1. In addition to meeting the requirements of s. NR 811.63 (6), the top of any earth covered reservoir shall be covered with a flexible waterproof membrane. The minimum membrane thickness shall be 0.060 inches. Department approval of the specific membrane proposed is required. Protective boards shall be placed over the membrane before applying the earth cover when recommended by the membrane manufacturer.

2. Bentonite panel membranes may not be used to meet the waterproof membrane requirement.

3. Earth covering of reservoirs shall be avoided where possible.

(f) Roof slope. The top of any storage structure shall have a minimum slope of 0.015 feet per foot to facilitate drainage.

(g) Drainage for roof or cover. The roof or cover of the storage structure shall be well drained, but downspout pipes may not enter or pass through the reservoir. Where parapets or similar construction which would hold water and snow on the roof are constructed, adequate waterproofing and drainage shall be provided.

(h) Exposed grouted precast concrete planked roofs. Grouted precast concrete planked roofs exposed to the environment shall meet the following requirements:
1. A minimum 2 inch thick reinforced concrete topping shall be installed over the top surface of the grouted plank roof. Fiber mesh may be used to provide reinforcing.

2. A minimum 0.060 inch thick flexible waterproofing membrane shall be installed over the concrete topping. Department approval of the specific membrane proposed is required. The installation of stone ballast over the membrane is optional.

3. The roof planks, concrete topping, or any insulation boards installed over the topping shall be installed to provide the minimum slope of 0.015 feet per foot required in par. (f).

(i) Exposed reinforced poured-in-place flat concrete roofs. Reinforced poured-in-place flat concrete roofs exposed to the environment shall be provided with a minimum roof slope of 0.015 feet per foot to facilitate drainage and a minimum 0.060 inch thick flexible waterproofing membrane installed over the roof. Department approval of the specific membrane proposed is required. The installation of stone ballast over the membrane is optional.

(11) SAFETY. Worker safety shall be considered in the design of the storage structure. The following shall apply:

(a) Ladders, ladder cages or safety climbing devices, balcony railings, landing platforms, guardrails, and safe locations of entrance hatches shall be provided where applicable.

(b) On elevated tanks where persons transfer from the access tube to the water compartment railings, handholds and landing platforms shall be provided, where applicable.

(c) On elevated tanks with riser pipes over 8 inches in diameter, protective bars shall be installed over the riser openings inside the tank.

(d) A handrail system shall be installed on the roof of any elevated tank.

(e) Storage structures shall be constructed to meet applicable local, state, including applicable portions of ch. SPS 332, and federal OSHA codes for specific safety requirements.

(f) Confined space entry should be in accordance with the requirements of s. SPS 332.29 and federal OSHA codes.

(12) FREEZING. All of the following actions shall be taken to minimize the potential for freezing:

(a) All water storage structures and their appurtenances, especially riser pipes, overflows, and vents shall be designed to minimize freezing that would interfere with proper operation.

(b) Riser pipes shall be insulated where possible.

(c) Recirculation pumps and air bubbler systems may be used to minimize freezing.

(d) Equipment used for freeze protection that will come into contact with the potable water shall meet ANSI/NSF Standard 61 or be approved by the department.

(13) TURNOVER. Storage facilities shall be designed to facilitate turnover of water in order to prevent freezing and stagnant water conditions. Consideration shall be given to installing separate inlet and outlet pipes, diffusers, baffle walls, adjusting controls to temporarily reduce storage capacities, or other department approved means where necessary.

(14) INTERNAL CATWALK. Every catwalk over a storage structure containing finished water or water to become finished water shall have a solid floor with sealed raised edges to prevent shoe scrapings, dirt, and other contaminants from falling into the water.

(15) PAINTING AND CATHODIC PROTECTION. Interior paints, coatings, and cathodic protection systems shall be installed in accordance with all of the following requirements:

(a) Metal surfaces shall be protected by paints or other protective coatings. The paints or coatings may be accompanied by cathodic protection devices.

(b) Interior paint and coating systems and application procedures shall be consistent with AWWA standard D102 in effect at the time of application, have ANSI/NSF Standard 61 approval for use in potable water, and be approved by the department in accordance with s. NR 810.09 (5). Paint and coating systems shall be applied, cured, and used in a manner consistent with the ANSI/NSF approval. After curing, the paint or coating shall not transfer any substance to the water that will be toxic or cause taste or odor problems.

(c) Cathodic protection shall be designed and installed by competent technical personnel.

Note: A copy of the cited AWWA standards is available from the American Water Works Association, 6666 West Quincy Ave., Denver, Colorado 80235.

(16) MISCELLANEOUS APPURTENANCES. The following miscellaneous appurtenances shall be installed where feasible or applicable and in accordance with the following requirements:

(a) Smooth-end sampling faucet. A smooth-end sampling faucet shall be installed in the connecting main or riser pipes of elevated tanks, standpipes, and reservoirs, if design permits. The sampling faucet shall be installed in accordance with the requirements of s. NR 811.37 (5) (b) 3.

(c) Valve vaults and above grade enclosures. Valve vaults and above grade enclosures installed at the base of storage facilities shall be protected against freezing and provided with floor drainage. Floor drains may be connected to a sanitary sewer, when available, if the floor elevation is at least one foot above the rim elevation of the nearest upstream sanitary sewer manhole. If a sanitary sewer is available but a manhole is not located nearby or the manhole does not comply with the upstream location or the one-foot requirement, the department may require installation of an additional manhole on the sanitary sewer main or on the sanitary building sewer. The facility may discharge to the ground surface by gravity, if possible, or else by a floor sump with a sump pump permanently installed. If constructed outside of the storage facility, the entrance to the vault or enclosure shall be locked to prevent unauthorized access.

(d) Condensate platform drains. Condensate platform drains shall not be directly connected to the overflow piping. The condensate platform drain shall be a minimum 2-inch diameter pipe and shall be brought down to within 12 to 24 inches of the ground surface and discharge downward facing with a free air break over a drainage inlet structure, splash pad, or riprap.

(17) DISINFECTION. Water storage structures shall be disinfected in accordance with all the following requirements:

(a) Disinfection required. Water storage structures shall be disinfected before being put into service or before being returned to service following maintenance or repair work to the water storage structure. Detailed procedures for disinfection, equivalent to those outlined in AWWA standard C652 in effect at the time of disinfection, shall be written into the specifications by the design engineer or contractor as applicable.

(b) Bacteriological sampling. Disinfection and bacteriological sampling requirements shall meet the requirements of s. NR 810.09 (4). Detailed procedures for bacteriological sampling shall be written into the specifications by the design engineer or contractor as applicable.

(c) Allowable chlorine in wasted water. The amount of chlorine in any water wasted from a storage structure to the environment shall be assessed to prevent harmful impacts. Dechlorination prior to discharge may be necessary in some cases to prevent harmful impacts. Water wasted to surface water may not contain any substances in concentrations that adversely affect the water as determined under chs. NR 105 and 106. For chlorine, no total residual chlorine may be measured in water being discharged to a surface water.

A copy of the AWWA standards is available for inspection at the central office of the department of natural resources and may be obtained for personal use from the American Water Works Association, 6666 West Quincy Avenue, Denver, Colorado 80235.

Disclaimer: These regulations may not be the most recent version. Wisconsin may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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