490-90.01 Design.
Pump station design shall be done by a registered professional engineer licensed in the State of Georgia. The depth of the wet well shall determine whether a submersible or mounted pump is used. Wet wells for mounted pumps shall not exceed 15 feet in depth, subject to the design conditions and approval of the PCWS.
490-90.02 General.
The following minimum requirements shall apply to wastewater pump stations:
A.Pump stations having less than 500 GPM capacity (per pump) shall utilize two pumps each having a capacity equal to the design flow.
B.Pump stations having a capacity of 500 GPM or more shall be reviewed on an individual basis and may have requirements differing from those outlined herein.
C.Grinder type centrifugal pumps will be used for pumps having a capacity of less than 100 GPM. Force mains shall be sized to provide a velocity of at least two feet per second.
D.The design shall allow for easy removal of any pump or equipment item without the need for shut-down of the entire pump station. A lift assembly shall be provided for pump or equipment removal.
E.The design engineer should consult the department after preliminary design data has been developed for information on approved pump manufacturers.
PCWS reserves the right to review each application on an individual basis and to reject the use of nonapproved manufacturers.
490-90.03 Submittals.
Submittal of construction plans shall include the following pump station information:
A.Capacity calculations. Use one GPM capacity per house on residential developments of less than 200 units, except that the minimum pump capacity shall be 30 GPM.
B.System head calculations, tabulated and plotted on the pump curve. Include a plot of force main velocity.
C.Construction drawings, details and specifications in sufficient detail to ascertain compliance with these regulations.
D.Cycle time. Calculations showing determination of wet well volume and cycle time at design conditions. Wet well volume should be sufficient to provide a cycle time of no less than five minutes from a pump "on" to next pump "on"
time.
E.Storage volume. Calculations showing volume of storage available in the event of a power outage. The storage zone shall be delineated on plan and profile drawings of the sanitary sewer system (see the subsection below on "standby power").
F.Buoyancy computations showing that structures are protected against flotation.
G.Manufacturer's catalog sheets, performance curves, installation drawings, specifications and list of options for the specific pump that is offered for approval. System head calculations, tabulated and plotted on the pump curve.
Include a plot of force main velocity.
H.Similar catalog data for controls, valves, hatches, yard hydrants, precast wet well and other manufactured items.
490-90.04 Post Installation.
A.After installation and before placing the system into full operation, the work must be inspected by the developer's engineer, who must then issue a certification to PCWS verifying that all work has been completed in accordance with approved plans. This certification shall include all construction of the pump station and force main. After acceptance of the work by the engineer, a factory representative shall inspect and start up the system certifying rotation, capacity, amperage draw, lack of vibration and other standard check points.
This certification shall state the beginning date of the warranty and include a copy of the warranty.
B.After installation and before placing the system into full operation, the work must be inspected by the developer's engineer, who must then issue a certification to the PCWS verifying that all work has been completed in accordance with approved plans. This certification shall include all construction of the pump station and force main. After acceptance of the work by the engineer, a factory representative shall inspect and start up the system certifying rotation, capacity, amperage draw, lack of vibration and other standard check points. This certification shall state the beginning date of the warranty and include a copy of the warranty.
C.After construction is complete, as-built drawings shall be furnished including one set of mylar sepias plus four sets of prints.
490-90.05 Spare Parts.
Pump stations shall be supplied with a spare complete pump, an extra impeller, set of bearings and a complete set of manufacturer's recommended spare parts.
490-90.06 Standby Power.
A.The minimum requirement for standby power for pump stations shall be that each station that does not have a permanent in-place generator shall have installed a manual transfer switch and receptacle for quick connection of a portable generator.
B.The need for providing a permanent in-place generator will be determined on the basis of storage time in the sanitary sewers leading to the pump station. If the storage time is less than 12 hours then a permanent generator must be installed. If storage time equals 12 hours or more only a transfer switch and provisions for connecting to a portable generator will be required. The following rules shall apply:
1.Storage volume available shall be taken as the volume between the low water level in the wet well and the elevation at which overflow would first occur (this might be the top of the wet well or that upstream manhole having the lowest top elevation). Volume of the wet well, manholes and sanitary sewer mains will be counted.
2.The rate of sewage inflow for these computations shall be taken as 150 gallons per day per residential unit. Systems serving other than residential customers will be considered individually.
3.Height of manholes shall not be extended above normal for the purpose of meeting this rule. The design shall ensure overflow before backing sewage into a dwelling or other building.
C.When required, emergency power will be supplied by an on-site emergency generator. The generator shall be diesel powered with an automatic transfer switch and provisions for an automatic exercise cycle. Specifications for the generator shall be submitted to the PCWS for approval.
490-90.07 Site Requirements.
A.Pump stations shall remain fully operational and accessible during the 25-year flood. All electrical controls shall be above the 100-year flood level. All motors and mechanical equipment shall be protected against physical damage from the 100-year flood.
B.Access roads shall be paved with a 12-foot wide surface of either concrete (six-inches thick with wire mesh) or asphalt (six-inches graded aggregate base plus two inches Type E asphalt). Maximum grade shall be 20 percent. Where access road lengths exceed 350 feet, six inches graded aggregate base may be used in lieu of a paved driveway. In cases where gravel driveways are utilized, the maximum grade shall be ten percent.
C.Both the pump station and the access road right-of-way shall have fee simple ownership dedicated to the county, and this shall be indicated on the subdivision plat. The dedicated space for the pump station shall include sufficient space for parking two trucks, plus turn-around, plus slope maintenance. The dedicated width on road right-of-way shall be 40 feet minimum.
D.Pump station sites shall be fenced with a minimum of six-foot high chain link fencing topped with three strands of barbed wire. Access gates shall be a minimum of 15 feet in width. The space inside the fencing shall be large enough to facilitate service vehicle access to the pumping station whenever the access road length exceeds 200 feet or when the road grade exceeds ten percent.
E.A metered water supply line (one-inch minimum size) shall be installed to the site, with the meter placed on the outside of the fencing. Inside the fence, in an insulated, vented, above ground enclosure, a pressure reducing valve shall be placed in the water main, followed by a reduced pressure zone back flow preventer with by-pass. Beyond the enclosure, a freeze-proof yard hydrant (Murdock BFHM-100 or approved equal) shall be installed near the wet well.
The hydrant shall be equipped with a suitable backflow preventer (Watts No.
NF8 or approved equal).
F.One pole-mounted, photo cell controlled, 150-watt security light shall be installed. It shall be equipped with a manual on/off switch (located in the main control panel) to override the photo cell control.
G.Where natural screening is not present to screen the site from view of residences, special plantings shall be installed to screen the site.
H.All unpaved ground areas inside the fence and extending four feet beyond the fence shall be treated with an herbicide and covered with a geotextile fabric, followed with a four-inch layer of no. 57 stone. The geotextile fabric shall be a nonwoven polypropylene weighing eight ounces per square yard with a minimum burst strength of 250 PSI such as Amoco Type 4553 or equal.
490-90.08 Design Features.
A.The wet well volume shall be sized to limit pump cycles to no more than six cycles per hour under worst conditions.
B.For wet wells, the minimum requirement shall be two-gravity vent pipes designed for natural ventilation. Vents shall be elevated to a minimum of two feet above the 100-year floodplain. Where conditions are conducive to formation of hazardous conditions (in the design engineer's opinion), then mechanical ventilation shall be provided. For dry wells, mechanical ventilation shall be required.
C.Submersible pump stations shall have a wet well structure and a separate valve pit. Both structures shall be precast concrete with a monolithic base. The valve pit shall be a minimum of four-foot by four-foot by five-foot deep with an aluminum ladder, and provided with a floor drain pipe, and a three foot by three-foot lockable aluminum access hatch. Wet wells may be either round or rectangular and shall have a diameter or width of at least five feet. Wet wells shall be sized to meet cycle time requirements with a drawdown (i.e., the distance between high water level and low water level) of not more than three feet. The wet well shall have a lockable aluminum hatch large enough for easy removal of pumps. Riser sections in precast units shall be sealed watertight using butyl rubber sealant or another approved sealant. Mastic shall not be used. Structures shall be adequately reinforced for all loading conditions normally encountered during shipping, construction and service. All openings (for pipes, hatch, conduits) shall be either cast in place or cored. Sanitary sewer pipe connections shall utilize rubber boot connectors, and be watertight. The wet well shall be equipped with an aluminum ladder.
D.All materials in the wet well and valve pit shall be corrosion resistant.
Mechanical equipment requiring ferrous metals shall have a coal tar epoxy coating. Guide rails for pumps shall be stainless steel. Miscellaneous metals including fasteners shall be aluminum or stainless steel; anchor bolts shall be stainless steel.
E.A pressure gauge shall be installed on the force main downstream of the gate valves, inside the valve pit and visible from ground level. A corporation stop shall be installed on the tap to allow removal of the gauge.
F.The discharge pipe of each pump shall have a slow-closing check valve followed by a gate valve before the two pipes join into a common force main.
G.Surge control valves. The pumping system shall be checked to determine if a surge control valve is required. If a valve is required, it shall be located within the valve pit on the common force main and a drain line installed to drain the wet well.
H.Pumps shall have the following features:
1.Non-clog, Vortex, or suitable substitution impeller made from cast iron unless extreme conditions require stainless steel.
2.Be capable of passing a three-inch sphere (except grinder and vortex pumps).
3.Be capable of dry operation without overheating.
4.Have mechanical seals with seal leak/overload sensor read by the controller.
5.Pump and motor casings shall be cast iron, and all fasteners shall be stainless steel.
6.Motor shall be selected to be non-overloading under all operating conditions.
7.Motor winding shall have a heat sensor with auto reset to prevent overheating; three-phase motors shall have two sensors.
8.Operating speed of the pump shall not exceed 3,600 rpm without special Title 3: Chapter 490 approval.
9.Pumps shall have a 5-year warranty.
10.The pump shall be automatically connected to the discharge connection elbow when lowered into place, and shall be easily removed for inspection or service. There shall be no need for personnel to enter pump well. Sealing of the pumping unit to the discharge connection elbow shall be accomplished by a simple linear downward motion of the pump. Each pump shall be equipped with a stainless-steel chain for easy removal.
11.Pumps shall be manufactured by Paulding County approved products listed in Appendix 4.0 or approved equal.
12.Motors shall be capable of ten starts per hour.
490-90.09. Force Main.
A.The force main shall be sized for a minimum velocity of two feet per second with one pump operating.
B.Force mains of four-inch diameter or larger shall be Class 350 or equivalent Pressure Class ductile iron pipe or L905, DR-14 PVC Pipe or approved equal.
Smaller force mains may be used only with grinder pumps and shall be PVC Pipe, SDR-21 with gasket joints. Buried PVC Pipe shall be marked continuously with metallized locator wire.
C.The force main profile shall slope continuously upward where practical. If high points occur where air could be trapped in the pipe, then a combination air release and vacuum relief valve (of the type made for sewage applications) will be installed at the high points.
D.The minimum depth of cover over force mains shall be four feet.
490-90.10 Electrical.
A.Pump station controls and electrical components shall be factory-wired in completely weather-proof stainless steel metal cabinets (NEMA 4X stainless steel). The cabinet shall be provided with condensate heaters, ventilation fans, air conditioning where required for VFD. Spare fuses of each type that is used in the electrical/control system shall be furnished. Panels shall be manufactured by Goforth Williamson Inc.
B.A main circuit breaker shall be installed to disconnect power to the entire station.
C.Three phase power will be provided for all motors exceeding five HP. Phase converters will not be allowed.
D.Protection against voltage surge and loss of a phase for control power and three phase service shall be provided.
E.The factory-wired panel shall be equipped with a ground bus and neutral bus.
Terminal shall be suitable for either aluminum or copper wire. All internal panel wiring shall be copper.
F.Motors shall be suitable for either 230 volt or 460 volt operations. Design engineer shall consult with the appropriate local electric utility provider to verify specifics pertaining to electrical power availability.
G.Wet well level shall be controlled by four sealed mercury tube float switches.
All floats shall be provided with 25 feet of Type SJO flexible cord and shall be attached to a bracket mounted at the top of the wet well. Float functions shall be as follows:
1.Float no. 1—Low level (pumps off)
2.Float no. 2—High level (lead pump on)
3.Float no. 3—Extra high level (lag pump on)
4.Float no. 4—Surcharge level (alarm activated)
H.The pump control system shall include the following features:
1.Lead pump/lag pump alternator.
2.From 20 HP to 49 HP shall have soft starts with a six-year drive protection warranty
3.From 50 HP and above shall have VFDs with a six-year drive protection warranty.
4.Pump failure indicating light.
5.Condensate heater.
6.Lead pump selector switch.
7.H-O-A switch and run light for each pump.
8.Control voltage shall be 120V.
9.Wiring shall be neatly tied and number coded to facilitate maintenance. A schematic diagram shall be furnished with the panel.
10.A 120V GFCI type electrical receptacle shall be located at the control panel.
11.Pump stations will be equipped with a cellular based telemetering circuitry connecting to the PCWS's SCADA system (Grundfos Utility Connect). the specific requirements are:
(a)Grundfos IO 351B Controller
(b)Grundfos CU 362 Controller Interface
(c)MP 204 Electronic Motor Protection Unit
(d)Vega C21 Radar Title 3: Chapter 490 TRANSPORTATION STANDARDS.