SECT-46_SEWAGE_PUMPING_STATIONS.rtf

SECTION 46 - SEWAGE PUMPING STATIONS

SECTION 46 - SEWAGE PUMPING STATIONS

Item No. Title

46.1 GENERAL

46.2 DESIGN STANDARDS

46.1 GENERAL

A. This division includes the general requirements for the design criteria and installation of sewage pumping stations.

B. The design, materials of construction, and installation procedures shall comply with the applicable provisions set forth in the following codes and in the following technical specifications contained herein:

Southern Building Code (SBC) - Building and Structural Sites Southern Building Code (SBC) - Building and Structures Southern Building Code (SBC) - Painting National Electrical Code (Modified) NEC - Electrical See Section 32 - Utility Excavation, Trenching and Backfilling See Sections 45, 52, and 55 - Pipe, Fittings, Valves and Appurtenances See Sections 40 and 41 - Sanitary Gravity Sewers See Section 45 - Sanitary Sewage Force Mains

C. All information shall be signed and sealed by a professional engineer licensed in the state of Florida. Submittals will be reviewed and approved by the City before approval of the site construction plans.

46.2 DESIGN STANDARDS

A. References The developer shall comply with the applicable regulations established by the Florida Department of Environmental Protection. Additionally, the criteria provided in Chapter 40, Wastewater Pumping Stations, of the Ten-State Standards Recommended Standards for Sewage Works, and WEF [Manual of Practice No.9] may generally be utilized as design guidelines, if not in conflict with state, county, City, or other regulatory agency requirements.

B. Design Flows Sewage pumping station wet wells shall be designed for the total ultimate development flow from all contributory areas. The design average daily flow shall be computed at the unit rates set forth in the following table. The maximum required pumping capability shall be the product of selected peak factors times the average daily design flow from the total service area. In general, the following factors shall be applicable for the range of flow indicated in gallons per minute (GPM) unless larger values are required or smaller amounts are justified with prior approval from the City Manager’s designated Engineer.

DESIGN AVERAGE DAILY FLOW

PEAK FACTOR

Less than 100,000 GPD 4.0 100,000 to 250,000 GPD 3.5 250,000 to 500,000 GPD 3.0 500,000 to 1,000,000 GPD 2.5 Greater than 1,000,000 GPD 2.0 1 Million gallons per day = 694 gallons per minute

C. Site Pumping stations shall be INSTALLED on readily accessible sites outside of the right-of-way, unless otherwise approved by the City Manager’s designated Engineer, and shall have adequate area provided for operation and maintenance of the facility. The site shall be a tract dedicated to the City. The site shall have a width and depth a minimum of twice the depth of the wet well. The site shall be well drained and not subject to flooding. Site preparation, pavement and walkways as necessary for good all-weather operations, site security and landscaping shall be in accordance with the SBC. (See standard detail drawings and Section 48.)

D. Structures Where buildings and/or structures are constructed, the relevant provisions of SIB’S shall apply, with special design consideration where applicable.

E. Hoisting Equipment Where required in large installations, in order to assist in maintenance operations, hoisting equipment shall be provided to lift pumps, motors, and other heavy equipment. Hoists shall be sized to accommodate the load for which provided, and may be hand-operated to a capacity of two (2) tons. Those units above two (2) ton capacity shall be motor-driven. Where hoisting equipment cannot be permanently installed or at minor equipment items, hoist eyes shall be installed over the unit.

F. Ventilation Facilities When required ventilating fans or blowers, ductwork and other appurtenances shall be installed in accordance with the recommendations of the ASHRAE Guide. Ducts shall be of non-corrosive material, such as aluminum, fiberglass, etc.

The following material or items shall be suitable for the indicated operational service.

(a) Gravity sewer influent pipe and fittings (within the limits of the site) – PVC, SDR35 (24" diameter or less).

(b) Sewer pressure pipe and fittings inside wet well and valve vault shall be HDPE DR11 with necessary electrofused fittings, transitions, MJ adapters, etc., required per pump station standard drawing internal and external pipe, plumbing configuration, or ductile iron flanged mechanical joint DIP with interior coating of Proctecto 401, Permite, Polybond or approved equal, complying with ANSI/ASTM D1248; virgin polyethylene lining material minimum DFT of 40 mils. Exterior coating of DIP and fittings shall be factory coated with a bituminous coating as specified in ANSI specifications A21.51. (Special Note: No raw sewage piping shall be less than four (4) inch diameter).

(c) Sewage service valves (valve vault plumbing) - gate valves (resilient wedge), with rising stem and hand wheels for exposed units; or gate valves with nonrising stem and hand wheels for underground; and, check valves as specified for "General Service."

(d) Potable water - Polyethylene tubing, with appropriate fittings, backflow preventer and valves per standard detail drawings.

2. Connections at Structures Where pressurized pipes are to extend into or through structures from the exterior, flexible connections shall be provided with Kor-N-Seal rubber boot or “link seal” connectors.

3. Supports and Restraining Special consideration shall be given to the support and restraining for piping systems. This requirement shall apply to both interior and exterior systems, with restraining of flanged pressure piping required where flexible connections are used.

H. Station Water System All sewage pumping stations shall be provided with a station water system, with adequate capacity and pressure, for wash-down, pump seal water or other non-potable utilization. Said supply shall be completely separated from the potable supply by use of reduced pressure type backflow preventers or other approved protective systems. Hose bibs shall be provided at convenient locations to facilitate maintenance.

I. Flow Meters Flow meters indicating, totalizing and recording flow meters shall be provided for all sewage pumping stations with ultimate rating of 1500 gallons per minute or larger, or as directed by the City Manager’s designated Engineer.

J. Pressure Gauges Gauges and gauge taps, per City standard detail, shall be provided for each sewage pump discharge. The gauges shall read in pounds per square inch of water, with a range suitable for the required service, and shall be 3½-inch dial, stainless steel case, “Duragauge,” as manufactured by Ashcroft, or approved equal. Gauges shall be equipped with diaphragms (neoprene or stainless steel), or other separating device, to preclude sewage from entering the mechanism. Liquid filled only.

K. Emergency Connections For sewage pumping stations not equipped with stationary stand-by power generators, an approved emergency power receptacle, pursuant to City standard details, shall be provided. In addition to the emergency receptacle, a pumping by-pass connection shall be provided. Said connection shall be located downstream of the pump chamber, with easy access and shall be coupled to the discharge main with valving as required for making a dead hook-up. The emergency pump connection shall be located within valve chamber or pump housing. The connection pipe shall be ductile iron, four (4) inches in diameter, with City standard “Quick” connector and cap.

L. Surge Control Surge control valves, or other approved systems, shall be provided for all sewage pumping stations or where hydraulic conditions indicate the necessity, as determined by the City Manager’s designated Engineer.

M. Telemetry System All new lift stations shall be supplied with a SCADA telemetry system in accordance with the City standard of Data Flow Systems (DFS). The control system shall be a “Tac Pack” with a “back-up” relay logic system actuated by a toggle switch on the inner door marked as “Bypass”.

2. The selected sewage pump system shall have the minimum capacity of pumping the design peak flow at the maximum computed system total dynamic head (TDH) requirements, with the largest pumping unit out of service. The pumps shall be capable of meeting all system hydraulic conditions without motors overloading.

3. Hydraulic efficiency shall be considered for pump selection. Hydraulic efficiency shall be maximized using only standard motors and impellers from an approved manufacturer. Nonstandard motors or trimmed impellers will not be accepted.

4. Head-capacity curves shall be prepared for the proposed pumping system in order to determine the various operational conditions. Hydraulic computations shall be in accordance with good engineering practice, with pipe friction loss calculated by the “Hazen-Williams Formula”, using standard friction factors based on the materials utilized; however, not greater than "C=110", unless the justification for higher values is authorized by the City Manager’s designated Engineer. The system head-capacity analysis shall be based on ultimate rated capacity and provide the following:

O. Wet Well Design The wet well structure shall provide a minimum capacity between operational water levels sufficient to allow a minimum of five (5) minutes between successive starts of the pumps. A minimum of twenty-four (24) inches between shutoff and lead pump start levels shall be provided. A minimum of twelve (12) inches between lead and lag pump shall be provided. A minimum of six (6) inches between lag pump and influent/alarm elevation shall be provided. Low water levels shall provide adequate submergence to preclude pump inlet vortexing, air binding or other design considerations. Operational maximum high water levels shall not exceed the invert elevation point of the lowest gravity influent pipe. Where the wet well extends below the ground water table, the structure shall be designed to eliminate any possibility of flotation. No interior ladders shall be permitted in the wet well. The wet wells shall be constructed of the same materials as sanitary sewer manholes. They shall be of an approved fiberglass construction, or be precast concrete with a fiberglass, AGRU Sure Grip, or GSE Studliner or approved equal, minimum 80 MIL/2MM thickness. The liner installation shall be installed in accordance with the manufacturer’s recommendations.