NR 811.64(3)(a)1.1. 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.

NR 811.64(3)(a)2.2. 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.

NR 811.64(3)(a)3.3. 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.

NR 811.64(3)(b)(b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of drainage water shall be prevented.

NR 811.64(4)(a)(a) General overflow discharge requirements.

NR 811.64(4)(a)1.1. ‘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.

NR 811.64(4)(a)6.6. ‘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.

NR 811.64(4)(a)7.7. ‘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.

NR 811.64(4)(b)(b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of overflow water shall be prohibited.

NR 811.64(4)(c)(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.

NR 811.64(4)(d)(d) Ground level structures.

NR 811.64(4)(d)2.2. The overflow shall be screened with 24-mesh corrosion resistant screen installed within the pipe at a location least susceptible to damage by vandalism.

NR 811.64(4)(d)3.3. 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.

NR 811.64(5)(a)(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.

NR 811.64(5)(b)(b) Pipe sizing. Piping shall be sized to accommodate design fill and removal rates including considerations for future improvements.

NR 811.64(6)(a)(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.

NR 811.64(6)(b)(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.

NR 811.64(7)(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:

NR 811.64(7)(a)(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.