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.
(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.
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.
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 which overlaps the framed opening and extends down around the frame a minimum of 2 inches. A compressible gasket shall be attached to the bottom side of the cover 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 which overlaps the framed opening and extends down around the frame a minimum of 2 inches. A compressible gasket shall be attached to the bottom side of the cover so that when the cover is closed it will provide a water tight seal around the manhole opening.
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.
Water storage structures shall be vented to the atmosphere. Vent installations shall meet the following requirements:
Open construction between the sidewalls and the roof to act as a vent is not allowed.
Prevent the entrance of surface water, rain and snow as applicable.
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 in a U-bend or mushroom cap constructed with the opening at least 4 inches above the roof and covered with 4- to 24-mesh corrosion resistant screen installed within the pipe or cap at a location protected from the environment. Mushroom caps 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.
Vents shall be sized to allow an air flow consistent with maximum water inflow and outflow rates.
Vent pipes shall be constructed of ductile iron, steel, or stainless steel pipe.
Mushroom caps shall be constructed of steel, stainless steel, or aluminum.
(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.
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.
Bentonite panel membranes may not be used to meet the waterproof membrane requirement.
(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:
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.
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.
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 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.
NR 811.64 Note
Note: For this section flat does not mean level.
Worker safety shall be considered in the design of the storage structure. The following shall apply:
Ladders, ladder cages or safety climbing devices, balcony railings, landing platforms, guardrails, and safe locations of entrance hatches shall be provided where applicable.
On elevated tanks where persons transfer from the access tube to the water compartment railings, handholds and landing platforms shall be provided, where applicable.
On elevated tanks with riser pipes over 8 inches in diameter, protective bars shall be installed over the riser openings inside the tank.
A handrail system shall be installed on the roof of any elevated tank.
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.
All of the following actions shall be taken to minimize the potential for freezing:
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.
Recirculation pumps and air bubbler systems may be used to minimize freezing.
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.
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:
Metal surfaces shall be protected by paints or other protective coatings. The paints or coatings may be accompanied by cathodic protection devices.
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.
Cathodic protection shall be designed and installed by competent technical personnel.
NR 811.64 Note
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.
(b) Chlorination tap.
A threaded tap for chlorination purposes shall be installed in the connecting main or riser pipes of elevated tanks, standpipes, and reservoirs.
(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 facilities discharging 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.
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
. For chlorine, no total residual chlorine may be measured in water being discharged to a surface water.
NR 811.64 Note
Note: 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.
NR 811.64 History
History: CR 09-073
: cr. Register November 2010 No. 659
, eff. 12-1-10; correction in (11) (e), (f) made under s. 13.92 (4) (b) 7.
, Stats., Register December 2011 No. 672
The applicable design standards of ss. NR 811.63
shall be followed for plant storage. In addition:
(1) 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 by s. NR 811.49
. The design shall address the possibility of having to backwash more than one filter at a time, or several filters in succession.
Clearwell storage shall be sized, in conjunction with distribution system storage, to relieve the filters from the strain of fluctuations in water use or peak demands.
When water storage is used to provide proper contact time for disinfection, documentation, including tracer testing, shall be provided to assure adequate detention time under all operating conditions. The department may require the installation of baffle walls or additional reservoir capacity if necessary to prevent short circuiting and to obtain adequate contact times.
(3) Basins and wet-wells.
Receiving basins, pump cans, and pump wet-wells for finished water or water to become finished water shall be designed as finished water storage structures.
NR 811.65 History
History: CR 09-073
: cr. Register November 2010 No. 659
, eff. 12-1-10.
Distribution system storage.
The applicable design standards of ss. NR 811.63
shall be followed for distribution storage. In addition:
(1) Pressure variation.
Distribution system storage facilities shall meet all the following requirements:
(a) Allowable head range.
The maximum variation between high and low levels in storage structures which float on a distribution system may not exceed 30 feet during normal usage.
(b) Minimum and maximum pressures.
The minimum and maximum pressure in service areas shall be 35 and 100 psi respectively at ground level.
In areas where a minimum of 35 psi cannot be maintained, a high pressure zone shall be established in the distribution system by means of booster pumps and related facilities or pressure boosting systems on individual service lines as required in subch. XI
. The use of individual service line booster pumps shall be limited to the extent possible.
In situations where static pressures exceed 100 psi, pressure reducing devices may be required on mains in distribution systems having documented system deficiencies or problems due to high pressure such as main breaks and service line breaks.
NR 811.66 Note
Section SPS 382.40 (7) (d) 2. a.
requires a pressure reducing device to be installed to protect individual services when the incoming pressure exceeds 80 psig.
The design shall allow draining of storage facilities for cleaning or maintenance while maintaining adequate positive pressure in the distribution system. The drains shall discharge to the ground surface as required in s. NR 811.64 (3)