NR 110.14(3)(c)5.
5. Mechanical ventilation for wet wells shall provide at least 12 complete air changes per hour if ventilation is continuous and at least 30 complete air changes per hour if ventilation is intermittent. Air shall be forced into the wet well by mechanical means rather than exhausted from the wet well.
NR 110.14(3)(c)6.
6. Mechanical ventilation for dry wells shall provide at least 6 complete air changes per hour if ventilation is continuous and at least 30 complete air changes per hour if ventilation is intermittent. For conserving heat in large lift stations, the department may approve the following 2 exceptions:
NR 110.14(3)(c)6.a.
a. Intermittent ventilation with an initial ventilation rate of 30 complete air changes per hour for 10 minutes and automatic switch over to 6 complete air changes per hour.
NR 110.14(3)(c)6.b.
b. A continuous ventilation system at a rate of 6 complete air changes per hour when the dry well is occupied and at a rate of 2 complete air changes per hour when not occupied.
NR 110.14(3)(d)
(d) Auxiliary equipment. All of the following auxiliary equipment shall be installed in lift stations:
NR 110.14(3)(d)1.
1. All dry wells shall be equipped with automatic heaters. The department may waive this requirement if it can be demonstrated that the heat output from the pump motors or controls is sufficient to keep equipment in the dry well from freezing.
NR 110.14(3)(d)2.
2. The installation of dehumidifiers shall be considered for all underground dry wells.
NR 110.14(3)(d)3.
3. Running time meters shall be installed for each pump in all lift stations. Where the department determines that flow measurement is necessary for the proper operation of the collection system or treatment system, suitable devices for measuring, totalizing, and recording flow shall be installed.
NR 110.14(3)(e)
(e) Electrical equipment. Electrical systems and components including motors, lights, cables, conduits, switchboxes, and control circuits, which will be located in wet wells, or in enclosed or partially enclosed spaces where hazardous concentrations of flammable gases or vapors may be present, shall comply with the NEC requirements for Class 1, Group D, Division 1 locations. In addition, equipment located in the wet well shall be suitable for use under corrosive conditions. Each flexible cable shall be provided with a watertight seal and separate strain relief. A fused disconnect switch or equivalent circuit breaker located above ground shall be provided for the main power feed for all lift stations. When the equipment is exposed to weather, it shall meet the requirements of weatherproof equipment.
NR 110.14(3)(f)
(f) Duplicate units. At least 2 pumps or pneumatic ejectors shall be provided in each lift station. Each pump or ejector shall be capable of pumping the design pumping rate as determined by sub.
(2) (b). If 3 or more pumps are provided, they shall be designed to meet expected flow conditions and shall be capable of pumping the peak hour design pumping rate as determined by sub.
(2) (b), with the largest unit out of service. Where the lift station will serve not more than 25 residential units, a single pump or ejector may be used, provided that the station is designed to permit the installation of a future duplicate pump or ejector with no structural changes.
NR 110.14(3)(g)1.1. All pumps, except grinder and effluent pumps, shall be capable of passing spheres of at least 7.6 centimeters (3 inches) in diameter, and pump suction and discharge piping shall be at least 10 centimeters (4 inches) in diameter. The department may allow the use of pumps with a lesser solids handling ability provided the pump is protected by a comminutor, a mechanically cleaned bar screen, or other suitable equipment.
NR 110.14(3)(g)2.
2. All pumps shall be nonclogging. Where a potential for clogging exists, protection in the form of manual bar screens, mechanically cleaned bar screens, comminutors or other suitable means shall be provided. Bar screens and comminutors shall be installed in accordance with s.
NR 110.16.
NR 110.14(3)(g)3.
3. Each pump shall be located so that under normal operating conditions it will operate under a positive suction head. Self- priming or vacuum primed pumps with adequate suction lift capability are exempted from this requirement.
NR 110.14(3)(h)1.1. Each pump, except submersible, screw, grinder and effluent pumps, shall be equipped with individual suction piping. Suction piping shall be as straight as possible.
NR 110.14(3)(h)2.
2. When suction elbows are used, the bell shall be placed above the floor of the wet well at a distance which is not greater than 1/2 nor less than 1/3 the diameter of the bell.
NR 110.14(3)(h)3.
3. A suitable shutoff valve shall be placed on each discharge line, except for screw pumps. A shutoff valve shall be placed on each suction line of the dry well pump. A check valve shall be placed on each discharge line between the shutoff valve and the pump, except for screw pumps. Check valves shall be placed in horizontal sections of the discharge pipe, except for ball check valves which may be placed in the vertical run.
NR 110.14(3)(i)1.1. Control systems shall be of the air bubbler type, the encapsulated float or displacement type, the ultrasonic type, the pressure transducer type or capacitance probe type.
NR 110.14(3)(i)2.
2. The control system shall be located away from the turbulence of incoming flow and pump suction.
NR 110.14(3)(i)3.
3. Provisions shall be made to automatically alternate the pumps in use where multiple equivalent capacity pumps are installed.
NR 110.14(3)(i)4.
4. All lift stations shall be equipped with an alarm system. The alarm system shall include audible and visual signals. The alarm system shall be activated in cases of power failure, pump failure, and at a predesignated high water level. It is also recommended that alarm systems be activated in the event of unauthorized entry or other lift station malfunction. The department may require that alarm systems be telemetered to responsible authorities for large or main lift stations.
NR 110.14(3)(j)1.1. At the design pumping rate, a cleansing velocity of at least 61 centimeters per second (2 feet per second) shall be maintained.
NR 110.14(3)(j)2.
2. A combination automatic air relief and vacuum valve or an automatic or manual air relief valve shall be placed at each high point in the force main to prevent air locking.
NR 110.14(3)(j)3.
3. When a force main enters the gravity sewer manhole, it shall discharge at a point not more than 60 centimeters (2 feet) above the spring line of the receiving sewer.
NR 110.14(3)(j)4.
4. Friction losses through force mains shall be based on the Hazen and Williams formula or other acceptable method. The roughness coefficient “C" value used for design shall be noted on the design report.
NR 110.14 Note
Note: When the Hazen and Williams formula is used, the department recommends a “C" value between 100 and 125 be used for all pipe except plastic pipe. A “C" value between 120 and 140 is recommended for plastic pipe. When initially installed, force mains may have a significantly higher “C" value. The lower “C" value (higher coefficient of friction) should be considered when calculating the head at design conditions. The higher “C" value should be considered when calculating the minimum head in the pump operating range power requirements.
NR 110.14(4)
(4)
Suction lift pumps or wet well mounted lift stations. NR 110.14(4)(a)(a)
Priming. Suction lift pumps shall be of the self-priming or vacuum primed type and shall comply with applicable requirements of sub.
(3), except as modified in this subsection.
NR 110.14(4)(b)
(b) Lift. The total dynamic suction lift may not exceed 6.0 meters (20 feet), unless the department approves pumps which exceed this specified limit based on certified pump performance curves and detailed calculations which justify the higher heads.
NR 110.14(4)(c)
(c) Compartment separation. The pump equipment compartment shall be above grade, partially recessed in the ground or offset and shall be isolated from the wet well in a manner which will prevent the humid and corrosive sewer atmosphere from entering the equipment compartment. Wet well access may not be through the equipment compartment and shall be at least 61 centimeters (24 inches) in diameter or equivalent area.
NR 110.14(4)(d)
(d) Electrical. Float type displacement switches and electronic transducers which are used in wet wells shall comply with the applicable requirements of sub.
(5).
NR 110.14(5)(a)
(a)
Construction. Submersible pumps and motors shall be designed specifically for raw sewage use, and for total submergence during operation, and shall comply with the applicable requirements of sub.
(3), except as modified in this subsection.
NR 110.14(5)(b)
(b) Pump removal. Submersible pumps shall be readily removable and replaceable without dewatering the wet well or disconnecting any piping in the wet well. Removal of one submersible pump from the lift station may not interrupt the operation of other pumps in the station.
NR 110.14(5)(c)1.1. Electrical supply, control, and alarm circuits shall be designed to provide strain relief appurtenances. All junction boxes containing terminals and connectors shall be protected from corrosion by being located outside the wet well or through the use of a watertight seal. Junction boxes for motor power cable connections and for intrinsically safe control circuits shall meet the requirements of weatherproof equipment.
NR 110.14(5)(c)2.
2. The motor control center shall be located outside the wet well and be protected by conduit seals or other appropriate measures meeting the requirements of the NEC to prevent the atmosphere of the wet well from gaining access to the control center. The explosion proof seals shall be located so the pump motor and the level control float switches or transducers can be removed and electrically disconnected at the respective junction box without destroying the seal.
NR 110.14(5)(c)3.
3. Pump motor power cables shall be designed for flexibility and serviceability. Ground fault interruption protection shall be provided in accordance with the NEC requirements. Power cord terminal fittings shall be corrosion-resistant and constructed in a manner to prevent the entry of moisture into the cable, shall be provided with strain relief appurtenances, and shall be designed to facilitate field connecting.
NR 110.14(5)(d)
(d) Explosion prevention. In order to minimize the potential for ignition of explosive gases in submersible lift stations, one of the following requirements shall be met:
NR 110.14(5)(d)1.
1. Low water level controls may be set such that the pump motor will remain totally submerged at all times. The lift station shall be equipped with a low water alarm in addition to meeting the requirements of sub.
(3) (i) 4., and which is distinguishable from the high water alarm.
NR 110.14(5)(d)2.
2. The pump motor may be rated for compliance with the NEC explosion proof requirements of Class 1, Group D, Division 1 locations.
NR 110.14(6)(a)
(a)
Construction. The wet well and dry well lift stations shall be designed specifically for raw sewage use and shall comply with applicable requirements of sub.
(3), except as otherwise provided in this subsection.
NR 110.14(6)(b)
(b) Electrical. When float type displacement switches or electronic transducers are used to control the liquid level in the wet well, they shall comply with the applicable requirements of sub.
(5).
NR 110.14(7)(a)(a)
Applicability. Screw pumps may be approved by the department on a case-by-case basis upon submission of appropriate manufacturer's data and the detailed design calculations.
NR 110.14(7)(b)
(b) Construction. Screw pumps and motors shall be designed specifically for raw sewage use, and shall comply with applicable requirements of sub.
(3).
NR 110.14(8)(a)
(a)
Applicability. Pneumatic ejectors may be approved by the department on a case-by-case basis upon submission of appropriate manufacturer's data and the detailed design calculations.
NR 110.14(8)(b)
(b) Construction. Pneumatic ejectors shall be designed specifically for raw sewage use, and shall comply with the applicable requirements of sub.
(3).
NR 110.14(8)(c)
(c) Compressors. Multiple compressors shall be provided. The compressors shall be sized to handle the maximum hour design flow with the largest compressor out of service.
NR 110.14(9)
(9)
Grinder pump lift stations — duplex. The department may approve duplex grinder pump lift stations. All duplex grinder pump lift stations shall be designed specifically for raw sewage use. Submersible duplex grinder pump lift stations shall meet the submersible pump requirements of sub.
(5), and the non-submersible type duplex grinder pump lift stations shall comply with applicable requirements of sub.
(6), except that each grinder pump shall have a minimum 1
¼-inch pump opening and discharge piping. The total motor horsepower requirement for each pump shall be 5 horsepower or less.
NR 110.14(10)(a)
(a)
Applicability. The department may approve simplex or individual grinder pump lift stations if no more than 3 residential units are ultimately served by 1 pump.
NR 110.14(10)(b)
(b) Construction. All simplex grinder pump lift stations shall be designed specifically for raw sewage use. The submersible grinder pump shall be designed for total submergence during operation. Both the submersible and the non-submersible type simplex grinder pump stations shall comply with all of the following requirements:
NR 110.14(10)(b)1.
1. `Location.' The location of the grinder pump stations and pressure service laterals shall be shown on the plans.
NR 110.14(10)(b)2.
2. `Flood proofing.' Grinder pump stations located in the floodplain shall be flood proofed by constructing 2 feet above the 100 year flood elevation or by providing watertight covers.
NR 110.14(10)(b)3.
3. `Pump removal.' Grinder pumps shall be readily removable without entry into the wet well or dewatering the wet well.
NR 110.14(10)(b)4.a.a. All valving shall be accessible without entry into the wet well or dewatering the wet well.
NR 110.14(10)(b)4.b.
b. If a grinder pump station discharges to a common pressurized sewer, a redundant check valve shall be provided. All valves including redundant check valves shall be installed at the grinder pump station. If a grinder pump station discharges to a gravity sewer, the redundant check valve is not required.
NR 110.14(10)(b)5.
5. `Ventilation.' All grinder pump stations shall be vented to the atmosphere either from the wet well or from the service lateral.
NR 110.14(10)(b)6.
6. `Accessibility.' No permanent ladders or steps shall be provided in the wet wells.
NR 110.14(10)(b)7.
7. `Pump size.' All grinder pumps shall have a minimum 1
¼-inch pump inlet opening and discharge piping.
NR 110.14(10)(b)8.
8. `Velocity.' A minimum velocity of 61 centimeters (2 feet) per second shall be maintained in the discharge piping during pump operation.
NR 110.14(10)(b)9.
9. `Separation.' A minimum separation distance of 25 feet shall be maintained between the grinder pump lift station and a private well or any other well subject to ch.
NR 812. A minimum separation of 200 feet shall be maintained between the grinder pump station and a community water system well in accordance with ch.
NR 811.
NR 110.14(10)(b)11.b.
b. All junction boxes shall be located outside the wet well, and shall meet the requirements of weather proof equipment. Electrical supply, control and alarm circuits shall be designed to allow disconnection at the junction box, without destroying the conduit-seal.
NR 110.14(10)(b)11.c.
c. Level controls using float type displacement switches shall be suspended in the wet well to facilitate maintenance.
NR 110.14(10)(b)12.a.a. In order to reduce the potential for ignition of explosive gases in submersible grinder pump lift stations, one of the following conditions shall be met: the low water level alarm shall be set such that the pump motor will remain totally submerged at all times; the pump motor shall be rated explosion proof in accordance with NEC requirements of Class I, Group D, Division 1 locations; or the motor shall be listed as safe and appropriate for residential use by the Underwriters Laboratories, Inc.
NR 110.14(10)(b)12.b.
b. In order to reduce the potential for ignition of explosive gases in non-submersible grinder pump lift stations with non-explosion proof pump motors, the pump motor shall be completely isolated from the wet well atmosphere in a separate gas tight housing.
NR 110.14(11)
(11)
Effluent pumps. The department may approve the duplex and simplex effluent pump lift stations for septic tank effluent in accordance with the applicable requirements of subs.
(9) and
(10), respectively.
NR 110.14(12)(a)(a) General. Provisions for emergency operation of lift stations shall be provided to prevent the discharge of raw or partially treated sewage to a surface water or to a ground surface and to prevent sewage backups into basements.
NR 110.14(12)(b)
(b) Lift station requirements. One of the following provisions shall be made to insure continued operation of each lift station:
NR 110.14(12)(b)1.
1. An on-site generator, with automatic switching and starting equipment may be installed. The generator shall have sufficient capacity to meet the total electrical demands of the pumps, controls, and auxiliary equipment.
NR 110.14(12)(b)2.
2. An on-site gasoline or diesel engine driven pump, with automatic switching and starting equipment may be installed. The pump shall have a capacity equal to or greater than the lift station peak design pumping rate.
NR 110.14(12)(b)3.
3. A portable generator may be available for use at the lift station. The generator shall have sufficient capacity to meet the total electrical demands of the pumps, controls, and auxiliary equipment. Electrical connections shall be accessible without maintenance personnel having to enter the lift station.
NR 110.14(12)(b)4.
4. A portable pump with a pumping capacity equal to or greater than the lift station peak design pumping rate may be available for use at the lift station. Quick disconnect fittings shall be used to connect the portable pump to the suction and the discharge line, and shall be accessible without maintenance personnel having to enter the lift station.
NR 110.14(12)(b)5.
5. The lift station electrical system may be connected to 2 independent electrical transmission routes which receive power from the same electrical grid network which supplies power to the lift station service area.
NR 110.14(12)(b)6.
6. The lift station may be equipped with a holding facility which has a capacity to hold the average design flow for a minimum period of 24 hours.
