(A) General.
(1) Public pumping stations serving more than one parcel are not normally allowed. They may be considered under extraordinary circumstances, but only by specific approval by the District Engineer during the preliminary design stages. If a public pump station is allowed, the planning and design must consider at a minimum, but not limited to, the following:
(a) SCADA;
(b) Remote monitoring with redundant alarm notification;
(c) Noise;
(d) Backup power;
(e) Corrosion;
(f) Odor;
(g) Pumping equipment;
(h) Electrical equipment; and
(I) Telemetry.
(2) Further conditions are provided in this section. They should be considered minimum conditions for use in the basis of design.
(3) Plans and specifications for all lift stations are to be prepared by a registered professional engineer and submitted to the District for review and approval.
(B) Hydraulics. Hydraulics include the following:
(1) Design conditions:
(a) Minimum force main velocity: two fps;
(b) Maximum force main velocity: eight fps; and
(c) Minimum inlet pipe slope: 2%.
(2) Firm-capacity for the lift station is defined as the pumping capacity for the facility with the largest pump out of service;
(3) The preferred operating region (POR) for a given pump is between 70% and 120% of the flow at the best-efficiency-point (BEP). Use the pump speed affinity relationships to estimate the BEP at reduced speeds;
(4) Design the lift station to serve the entire tributary area using build-out densities that conform to the District’s most recent capacity study based on the city’s or county’s latest general plan;
(5) The lift station must be capable of operating within the POR at all flows between the firm-capacity and one quarter of the firm-capacity;
(6) The ratio of minimum net positive suction head available (NPSHa) to net positive suction head required at BEP (NPSHr) must be 2.0 or greater;
(7) Pump station design calculations shall address surge and “water hammer”, and, if required, surge control shall be provided; and
(8) Unless waived by the District Engineer, a hydrogen sulfide study will be required. Corrosion control and odor control may be required based on the results of the hydrogen sulfide study.
(C) Pumps and motors. Pumps and motors are subject to the following:
(1) All pumps shall be designed to handle solids and must be capable of passing a minimum three-inch diameter sphere;
(2) All pumps shall be identical;
(3) All pumps shall be fitted with 240/480 VAC, three-phase, premium-efficiency, inverter-duty motors, except as approved by the District Engineer;
(4) Brake horsepower shall not exceed the nominal rating of the motor between shutoff and the maximum flow shown on the manufacturers’ published performance curves;
(5) The service factor for all motors shall be 1.15;
(6) Provide thermal and seal minder overload protection for all pump motors; and
(7) Provide a spare mechanical seal and other spare parts as recommended by the pump manufacturer.
(D) Wet well. Wet well includes the following:
(1) Working capacity of the wet well is defined as the volume between the maximum and minimum normal operating levels;
(2) Wet well shall have enough working capacity to prevent any pump from starting more than four times per hour;
(3) Wet wells shall be designed in accordance with Hydraulic Institute Standard No. 9.8 (Pump Intake Design) except as noted otherwise in this standard;
(4) Set the high-level alarm at the invert elevation of the nearest upstream manhole. Provide a minimum clearance of six inches between the maximum normal operating level and the high-level alarm;
(5) Set the low-level alarm at least one foot above the motor (for submersible pumps), and at least three feet above the suction bell. Provide a minimum clearance of six inches between the minimum normal operating level and the low-level alarm;
(6) Design the wet well to counteract the effects of buoyancy due to high groundwater conditions. The groundwater elevation used for design shall be determined by a licensed geotechnical engineer. Ground surface may be used as groundwater level in lieu of a geotechnical report;
(7) Wet well shall be constructed using reinforced concrete. Concrete mix design shall be suitable to resist damage from sulfides;
(8) Wet wells shall be lined with GSE 5 mm HDPE Studliner in accordance with manufacturer’s recommendations; and
(9) Penetrations into the wet well shall resist infiltration and exfiltration.
(E) Piping and valves. Piping and valves are subject to the following:
(1) Provide a control gate or plug valve on the wet well inlet to permit isolation of the wet well;
(2) Provide a plug valve and rubber flapper style check valve on the discharge of each pump. Plug valves shall be non-lubricated neoprene faced eccentric. Check valves shall be installed in the horizontal plane;
(3) Buried pressure piping shall be AWWA C151 ductile iron or C900/C905 PVC with AWWA C110 and/or HDPE with mechanical joint fittings;
(4) Provide mechanical joint restraint at all fittings and pipe joints. Thrust blocks are permitted only if mechanical joint restraint is not feasible;
(5) Design pressure piping to maintain velocities between two feet/second and eight feet/second;
(6) Design gravity piping in accordance with the District’s standard for sewer construction;
(7) Provide a connection to the force main to permit bypass pumping. Coordinate sizing and connection details with District staff;
(8) Provide restrained flanged coupling adapters to permit removal of all valves, meters and other mechanical equipment connected to the piping; and
(9) District Engineer will determine if swabbing or pigging facilities are required at the lift station. If so, all downstream piping and related equipment shall be designed to accommodate this appurtenance. Launching facility will be detailed on lift station plans and must accommodate using lift station pumps for propulsion. Provide all necessary valving. Contact the District for suggested design requirements.
(F) Electrical equipment. Electrical equipment is subject to the following:
(1) Install all major electrical equipment, including utility meter and main circuit breaker enclosures, panel boards, control panels and motor control centers outside of hazardous areas, as defined in the National Electric Code, Article 500;
(2) Provide utility meter and main circuit breaker in an overall 316 stainless steel enclosure rated NEMA 4X with a viewing window centered on the utility meter;
(3) Provide NEMA 4X, 316 stainless steel enclosures for electrical equipment and control devices where ventilation or air conditioning of the devices is required. Provide NEMA 4X, 316 stainless steel enclosures for all other equipment and devices;
(4) Provide OSHA approved rubber mat in front of all indoor control panels;
(5) Provide industrial LED strip fixtures in the building interior;
(6) Provide an exterior light in accordance with STD #601. Provide 12-inch diameter pole-mounted LED luminaires at 120V; and
(7) Provide a NEMA combination motor starter. Manufacturer: Allen Bradley, CUTLER-HAMMER or equal.
(G) Instrumentation and controls. Instrumentation and controls are subject to the following:
(1) No flow tube or flow meter required unless stated by the District Engineer;
(2) Provide Siemens Hydroranger for continuous level monitoring in the wet well;
(3) Provide discrete level float switches for high-high level and low-low wet well level alarms;
(4) Provide a programmable logic controller (PLC) and human-machine interface (HMI) for monitoring all instrumentation signals, alarm conditions and pump control. Provide a minimum of 20% spare I/O capacity. Manufacturer and model shall be approved by the District Engineer;
(5) Develop local operator interface (LOI) for the District’s SCADA system. Coordinate screen development with District Engineer; and
(6) Provide facility for pump testing.
(H) Telemetry. All control panels will have the following general features: Panel design will incorporate the following features:
(1) LED lamp with switch;
(2) 120 VAC duplex convenience outlet;
(3) Provide 120 VAC uninterruptible power supply (UPS) APC SC620 or an equivalent DC voltage subsystem sized for 150% of peak load for all internal panel components for a minimum of 30 minutes run time; and
(4) Provide documentation that adequate interface with the District’s SCADA system is achievable to the satisfaction of the District Engineer.
(I) Standby generator. Standby generator is subject to the following:
(1) A standby generator is required for all new pump stations. The following minimum requirements for the standby generator are as provided herein;
(2) Provide permanently installed, natural gas generator with an automatic transfer switch. The generator’s engine must meet the Monterey Bay Air Resources District (MBARD) emission standards;
(3) Generator sizing calculations will assume loading based on lead pump running, lag pump starting and full operation of all electrical equipment at the site;
(4) Provide instrumentation:
(a) Generator voltage, frequency and amp meters;
(b) Oil pressure gauge;
(c) Battery volt meter;
(d) Water temperature gauge;
(e) Hour meter;
(f) External battery with trickle charge; and
(g) Dry contacts for telemetry - showing generator running and generator failure.
(5) Provide automatic shut-off and alarms:
(a) Low engine oil pressure;
(b) High engine temperature;
(c) Over speed; and
(d) Over crank.
(6) Provide sound attenuation as necessary to meet or exceed applicable noise standards for location. Attenuation may include silencers and/or insulation.
(J) Details required on improvement plans. Details required on improvement plans include the following:
(1) Site plan: locations of power pole, transfer switch, emergency generator, grounding electrode, control panel, wet well, driveway, fencing, water service, emergency suction/discharge boxes. Provide site grading and drainage details;
(2) Wet well: influent piping (standard inside drop manhole); suction piping (minimum six inches off bottom of manhole); emergency suction line; water/alarm levels (pump on, pump off, low level, high level); redundant high-water float switch; and
(3) Force main discharge details.
(K) Record drawings and manuals. Record drawings and manuals are subject to the following:
(1) Provide three copies of approved record drawings and an electronic scan of the drawings in *.TIF or *.PDF format with a minimum 200 dpi resolution, and an electronic copy in AutoCAD latest version; and
(2) Provide three copies of O&M Manuals plus an electronic copy when available.
(L) Building structure. Pump station buildings shall be constructed of split-face concrete masonry unit (CMU) with standing-seam metal roofing unless otherwise approved by the District Engineer.
(Ord. 2019-02, passed 4-25-2019)