405 - Pump Station Construction

405 Pump Station Construction 2012 STANDARD SPECIFICATIONS FOR CONSTRUCTION - SECTION 405

GENERAL DESCRIPTION

Definitions and Terms

American Water Works Association (AWWA): AWWA is an international non-profit scientific and educational association founded to improve water quality and supply.

Axial Flow Pump: An axial flow pump is a type of centrifugal pump which moves fluid axially using an impeller. The fluid enters and exits the pump in a parallel direction. The pump provides a high flow rate and low head.

Centrifugal Pump: A centrifugal pump consists of an impeller, a casing, and various mechanical components to change the course of a fluid from the center of the pump to the outer edges of the pump.

Check Valve: A check valve is a type of valve which only allows movement of fluid or gas in one direction. Confined Space: A confined space is any area which has limited entry or egress, generally not suitable for human inhabitants, and may contain hazards, such as toxic gas, flammable substances, or insufficient oxygen.

Control Panel: A control panel is a centralized location within a pump station which allows for control of the various components within the pump station. It controls the start/stop sequence of the pumps, monitors the operation, and provides alarms if components are not working properly.

Expansive Water Stop: An expansive water stop is a device installed within construction joints to prevent water movement through the joint by swelling when coming in contact with water.

Float Switch: A float switch is a device installed on a pump to either turn the pump on or off based on the level of the fluid and the switch location.

Force Main: A force main is a pressurized pipe system used to convey a fluid. This could be used in water mains, sanitary sewer, or in some cases storm water management. A pump station is typically the beginning point of a force main where a fluid is pressurized into a piping system by a pump.

Isolation Valve: An isolation valve is a valve used to stop the flow of fluid to a certain location. Machine Room: A machine room is a space within a pump station where pumps and other operational equipment are located.

Plug Valve: A plug valve is a valve which uses either a cylindrical or conically tapered plug to stop flow. Typically, there is a hole within the plug which will allow fluid to pass through, but if the plug is turned 90 degrees, the flow of the fluid is stopped.

Pump House: A pump house is structure or building that houses the pumps and related equipment used to convey fluid from one location to another.

Rack Room: A rack room is a room in which the electrical components and control panels are located. Submersible Pump: A submersible pump is a fully sealed pump designed to be operated while fully submerged in a fluid.

Trash Rack: A trash rack is a grating system within a pump station designed to prevent large debris from entering the pumps and causing damage.

Valve Chamber: A valve chamber is an enclosed below-grade structure designed to house isolation valves and other related control equipment necessary to operate a pump station.

Vertical Pump: A vertical pump is a pump that is driven by a vertical motor and shaft.

Wet Well: A wet well is a large tank that receives and temporarily stores fluid for the purpose of pumping.

General Overview

Pump station construction is extremely specialized work. Therefore, if a pump station is to be constructed, the plans and project special provisions are the primary resources detailing the work to be completed. It is important for the Inspector to know that a licensed electrical Contractor is required to perform all electrical work shown on the plans. The Contractor must guarantee the in-service operation of the mechanical and electrical equipment and related components for a period of six months following acceptance of the total contract, or as defined in the proposal, at which time all unexpired manufacturer’s equipment warranties will be assigned to MDOT. Refer to Division 8 of this manual for further information on pump station electrical requirements.

top

MATERIALS

All materials governed by the Standard Specifications for Construction must meet acceptance requirements in the Materials Source Guide and be listed on the Contractor-provided Material Source Lists in the project files. Pump stations include many materials, products, and equipment not addressed by the Standard Specifications for Construction. These products and materials require submittals be reviewed to ensure conformance with the design intent and performance characteristics necessary for proper operation of the pump station. Refer to the special provisions for these materials as well as required submittal and approval procedures. Submittals may be needed for items such as product/material details, material certifications, test results, and shop drawings.

Description of Materials

Piping

Exterior Piping

The pipe material and class are noted on the plans. MDOT defines the pipe by class, which is based on the amount of cover over the pipe. Refer to Table 402-1 of the Standard Specifications for Construction for acceptable pipe in each class.

Interior Piping

Discharge Piping and Fittings

Furnish discharge pipe and fittings that are in accordance with ASTM A36/A36M steel, or Class 53 ductile iron (DI), and connect to the discharge column pipe stub. Coating requirements for piping and fittings can be found in the Special Provision for Pump Station Special Coatings. Connections should meet the requirements detailed in the project special provisions.

Following are some common requirements:

1. Grooved pipe connections must be rigid and in accordance with AWWA C606.
2. Flanged pipe connections must be in accordance with AWWA C115. Flange hardware must meet AISI Grade 304 stainless steel and gaskets must be rubber and full face.
3. Plain end pipe connections are considered flexible couplings.

Vent and Vactor Pipe and Fitting

PVC Piping and Fittings All pipes and fittings called to be PVC must be polyvinyl chloride (PVC) Schedule 80 manufactured from virgin rigid PVC with a cell class of 12454 in accordance with ASTM D1784. Pipes must meet PVC Schedule 80 Iron Pipe Size (IPS) in accordance with ASTM D1785 and fittings must be injection molded in accordance with ASTM D2467. Pipe and fittings must be manufactured as a system and the product of one manufacturer. Connections are to be as shown on the plans and typically consist of:

1. Solvent cement joints in accordance with ASTM D2564.
2. Threaded flange hardware is AISI Grade 304 stainless steel.

Ductile Iron Piping and Fittings All piping required to be ductile iron must be AWWA C151, Class 54 with ductile iron fittings in accordance with AWWA C110. Ensure pipe and fittings are cement mortar lined in accordance with AWWA C104 and have an exterior asphaltic coating when buried and red primer otherwise. Ensure connections are as shown on the plans and as follows:

1. Flanges must meet AWWA C115.
2. Flange hardware must meet AISI Grade 304 stainless steel.
3. Flange gaskets must be rubber and full face.
4. All piping and fitting coatings must be in accordance with the Special Provision for Pump Station Special Coatings.

Modular Mechanical Seals

Ensure modular mechanical seals consist of interlocking, chemical resistant synthetic rubber links shaped to continuously fill the annular space between a pipe and wall opening. Ensure the seals expand by the tightening of stainless steel bolts. Furnish a pressure plate under each bolt head. Ensure the modular mechanical seal provides water-tight and gas-tight seals between passing pipe and sleeve.

Building Structure Components

The structure of a pump station is typically made of concrete, which is cast in place onsite and reinforced with epoxy coated steel bar. Criteria that are cause for rejection include:

• Defects that indicate imperfect proportioning, mixing, or forming.
• Honeycombed or open textured surfaces that would adversely affect the function of the pump station.
• Damaged ends preventing required joint construction.
• Concrete that does not attain the required compressive strength.
• Out of tolerance dimensions.
• Low or high air content.

Prepackaged pump station systems are built over the wet well and placed on a concrete pad.

Concrete

Concrete used for pump stations must be a homogenous mixture of cement, aggregates, admixtures, and water. The concrete design must have a minimum 28-day compressive strength as detailed on the plans, air content between 5.5% and 8.5%, and a maximum slump of 4 inches. If Type F or Type G admixtures are used, the maximum slump can be 7 inches.

Reinforcing Steel

Typically, bar reinforcement is used to reinforce the concrete structure of a pump station. Reinforcement must be placed within 1/2-inch of the location shown on the shop drawings and have a minimum of 3 inches of cover. Exposed reinforcement is just cause for a portion of the pump station to be rejected.

Wet Well

A wet well is typically a below-grade concrete structure that is the holding tank for incoming flow.

Coatings

Concrete surfaces are coated to provide protection from moisture and influent flow.

Granular Material (Class II, IIA, IIAA, III, and IIIA)

Granular backfill, often comprised of sand, is used to fill the space around existing or new features and the existing ground. Refer to Section 902 of the Standard Specifications for Construction for material requirements.

Aggregates

Aggregates are often used as a base to support the pump station over existing ground. Depending on the project specifics, either open-graded or dense-graded aggregate is used. All aggregate must be in accordance with Subsection 902.05, Subsection 902.06, and Table 902-1 of the Standard Specifications for Construction.

Pumps and Appurtenances

All mechanical materials must be in accordance with Section 405 of the Standard Specifications for Construction, ASTM standards, the Hydraulic Institute, and as specified in project special provisions. Lubricants for pumps are to be recommended by the pump manufacturer.

Pumping equipment includes motors, discharge heads, baseplates and elbows, sole plates, pump column assemblies, bowl assemblies, supports, anchor bolts, and other items.

Vertical Mixed Flow Pumps

A common requirement is for the principal components of vertical mixed flow pumps to be interchangeable with other pumps of like capacity. Vertical mixed flow pumps must be capable of pumping storm water carrying suspended sand and able to pass up to 2-inch solids.

Certified test curves for each pump based on the duty point shown on the plans and in accordance with Hydraulic Institute standards showing head, capacity, efficiency, and brake horsepower must be supplied for review by the Engineer. Pumps should be designed to not be damaged by reverse rotation caused by backflow on the pump. Stainless steel data plates must be on each pump unit detailing the manufacturer’s name, pump size and type, serial number, speed, and other pertinent data.

Other requirements for vertical mixed flow pumps will be detailed on the plans.

Submersible Pumps

Submersible pumps must be capable of pumping storm water carrying suspended sand and able to pass up to 2-inch solids. The pumps with appurtenances and cabling should all be capable of being continuously submerged underwater without loss of watertight integrity to a depth of 65 feet. Submersible pumps are also commonly required to be explosion-proof in accordance with NEC Class I, Division I, Group D with a Factory Mutual Research Corporation (FM) or UL certified and designed for continuous use. The motor and pump must be from the same manufacturer.

The contract documents will note required factory testing for all submersible pumps prior to shipping to site. Certified test curves for each pump showing head, capacity, and brake horsepower should be provided for a range of operating conditions. Following is an example table included within the contract documents that would detail the pump specifics.

Station Name Location Pump Type No. of Pumps Capacity, gallons per minute (gpm) Each Pump(a) Total Dynamic Head (a)(feet) Motor (volts)

D01 of 82101 Eastbound Old M-14 at CSX railroad crossing west of I-275

Submersible

2

1300

27

460 a. Ensure pumps in this table are capable of pumping at the capacity and head conditions (duty point) listed, within the performance tolerances of the Hydraulic Institute, level B.

Electrical Components

Electrical Power Conductors and Cables

Conductors and cables used for electrical power for a pump station are typically required to be one of the types listed below. Refer to project specifications for more details on conductor and cable requirements. • Type RHW, 600 volts, stranded copper, UL listed. • Type XHHW, 600 volts, stranded copper, UL listed. • Type THHN/THWN, 600 volts, stranded copper, UL listed.

Grounding and Bonding Equipment

All ground and bonding equipment must be in accordance with Subsection 918.02.B of the Standard Specifications for Construction and the National Electrical Code (NEC). Typically, a minimum of three ground rods are required at 3/4-inch diameter and 10 feet long.

Hangers and Supports for Electrical Systems

All hangers and supports for electrical systems must be 316 stainless steel and UL listed.

Building Conduits for Electrical Systems

Conduits for building electrical systems are to be supplied as detailed on the plans and special provisions. Regardless of the conduit type, seal-off fittings must be provided within 18 inches of where conduits enter/leave hazardous locations. Common types of conduits that will be detailed on the plans are as follows: • galvanized rigid steel. • PVC-coated rigid steel. • Rigid nonmetallic (PVC Schedule 40 or 80). • Liquid-tight flexible metallic.

2.1.6.5 Boxes and Covers Electrical boxes and covers used for pump stations must be sized in accordance with NEC requirements. Covers must include gaskets and be held in place with corrosion-resistant machine screws. Electrical boxes must be NEMA 4X 316 stainless steel. In hazardous locations, electrical boxes must be NEMA 7 rated. For outlet boxes, Type FS and FD boxes must be provided as required. 2.1.6.6 Transfer Switches 2.1.6.6.1 Manual Transfer Switches Manual transfer switches must be made from a NEMA 4X 316 stainless steel enclosure and be UL listed. They will be 3-phase, 4-pole, heavy-duty for the amperage detailed on the plans. 2.1.6.6.2 Automatic Transfer Switches Automatic transfer switches must be made from a NEMA 4X 316 stainless steel enclosure and be UL listed. They will be 3-phase, 4-pole, heavy-duty for the amperage detailed on the plans. 2.1.6.7 Panelboards Panelboards must be made from a NEMA 4X 316 stainless steel enclosure, be UL listed, have an integral surge protection device, and be a dead front type with a copper bus. Main and branch circuit breakers sizes will be detailed on the plans. 2.1.6.8 Wiring Devices 2.1.6.8.1 Switches All switches must be rated for 20 amps at 120 volts and be heavy-duty UL listed. 2.1.6.8.2 Receptacles All receptacles must be rated for 20 amps at 125 volts and be heavy-duty, including ground-fault circuit interrupter (GFCI) where required, with back and side wiring. They should have weatherproof while-in-use covers and be UL listed. Special purpose receptacles will be detailed in the contract documents. 2.1.6.9 Motor Control Centers All motor control centers must comply with NEC, NEMA, and UL. They must be constructed of code grade gauge steel, have a dead front, and be powered by 600-volt, 3-phase, 4-wire conductors with ampere interrupting capacity (AIC) ratings as well as have circuit breakers and motor starters as indicated on the plans. The main bus must be copper with fully rated horizontal bus bars the entire length and vertical bus bars sized for loads served. The enclosure for the motor control center must meet NEMA 12 rating. The electrical power main, metering, and surge protection for the devices will be indicated on the plans. 2.1.6.10 Pump Control Panels Pump control panels must be designed to minimize the number of pump starts per hour by providing first-on, first-off alternation. They must include the necessary circuit breakers, power supplies, automatic control equipment, etc., in a single enclosure. Pump control panels must incorporate all pumps into the alternation sequence, and provide each pump with an adjustable 0- to 30-second start time delay. If the high-level float switch is activated, bypass the normal level sensor control and start all pumps in auto mode with time delays to provide a staggered starting of the pumps. When started by the high-level float, pumps are to run until the level in the wet well drops to/below the low-level float switch elevation. The pump control panel must cycle pumps on float switch control until the control system is manually reset. Float switch control logic to function independently of the pump controller and override pump controller operation. Include separate overcurrent protection for the float switch and for the pump controller with 120-volt power circuitry. The pump control system must automatically resume normal operation after a power outage. 2.1.6.10.1 Enclosure All enclosures must be wall mounted, NEMA 4X rated, UL listed, and constructed of 14-gauge minimum stainless steel. Enclosures must include a thermostatically controlled heater to prevent condensation. 2.1.6.10.2 Control Relays Control relays must be NEMA style, NEMA rated industrial with 120-volt field replaceable coils and a minimum of two normally open and two normally closed contacts. Contacts must have plug-in type cartridges and be arranged for easy contact conversion or replacement. Plug-in style International Electrotechnical Communication (IEC) rated relays are prohibited. 2.1.6.10.3 Time Delay Relays All time delay relays must be plug-in type, electronic, adjustable with 10-amp, double pole-double throw (DPDT) contacts and operate on 120 volts. 2.1.6.10.4 Intrinsically Safe Relays Intrinsically safe relays must be provided for the high and low wet well level float switches. 2.1.6.10.5 Equipment Hour Meters Equipment hour meters must be mechanical with five digits (hours and tenths) and mounted on the pump control panel inner door. 2.1.6.10.6 Selector Switches Selector switches must be heavy duty, three-position, 30 mm, hand-off-auto, flush-mounted on pump control panel inner door. 2.1.6.10.7 Pilot Lights Pilot lights must be heavy-duty, 30 mm, push-to-test for alarm and running indication on pump control panel inner door. LED type lamps and lens colors as indicated on the plans. 2.1.6.10.8 Terminal Blocks Terminal blocks must be 1-3/8-inch in size, DIN rail mountable, sectional type with white marking strip for numbered identification, have recessed screw heads, have compression clamps, and be rated for 600 volts at the ampere as detailed on the plans. 2.1.6.10.9 Wiring Wiring must be a minimum 14 American Wire Gauge-Machine Tool Wire (AWG-MTW) and 60oC rated for AC connections. Thermoplastic wire cover rated at 600 volts and colored red for AC wires; light blue for DC wires, canary yellow for wired interconnecting with other control panels or systems which may be energized from alternate power source; green for all grounding; black wire for power source; and white for power neutral. 2.1.6.10.10 Control System The pump controller must be microprocessor-based with a pump module, user interface, and 120-volt power supply. The processor speed must be 200 megahertz (MHz) with 64 megabyte (MB) random access memory (RAM), and 32 MB of flash memory. Software for the control system must support multiple pump operations. A time delay between start-up of pumps during loss of power must be included in the system. The controller must operate in a “pump down” mode. The control system must include monitoring, control, alarming (including alarm dialing), and configuration for all devices. The system must have a web-based user interface requiring only an internet connection. The system must use a cellular data network connection for communicating between remote sites and the web interface, deliver alarm messages via mobile phone messaging or email, and allow alarm acknowledgement via website access or mobile phone. A cellular modem for wireless data communications via the internet must be included in the control system. The modem must include standards-based, quad-band, Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS) Class 10 performance; RS-232, USB, and Ethernet interfaces; embedded Transmission Control Protocol/Internet Protocol (TCP/IP) protocol stack; and support 850/900/1800/1900 MHz cellular connectivity. Pump controller must have the capability and hardware to monitor station 3-phase power and 3-phase motor current for each pump installed. The power monitoring circuitry must include fuse protection. The pump controller must have the capability of calculating flow based on wet well level and volume. 2.1.6.11 Lighting Fixtures Light fixtures must be LED type suitable for operation on 120-volt power with 3000K for machine room, 5000K for rake room, 4000K for other spaces, and be UL listed. As noted on the plans, all fixtures must be rated for installation in hazardous locations and suitable for wall or pendant mounting. Twin lamp LED type emergency lighting units must be suitable for operation on 120-volt power with battery-backup for 90 minutes of continuous operation, UL listed, and suitable for wall mounting. 2.1.6.12 Dry Type Transformers Dry type transformers sizing (KVA) will be detailed on the plans, but must be 480-volt primary and 240/120-volt secondary, single phase, 115°C temperature rise, NEMA 4X 316 stainless steel enclosure, and UL listed. They should be set up for wall or floor mounting. 2.1.6.13 Surge Protective Devices Surge protection devices must meet the requirements of ANSI/UL 1449 and ANSI/IEEE C.62.41. They must include a circuit breaker disconnect, provide line-to-line, line-to-neutral, and line-to-ground protection. Each device must be rated for 600 volts,100 KA per phase, and be UL listed. 2.1.6.14 Motor Controllers There are 3 main types of motor controllers used in pump stations: 1. Full-voltage non-reversing motor starters 2. Reduced-voltage solid-state motor starters 3. Variable frequence drives 2.1.6.14.1 Full-Voltage Non-Reversing Motor Starters Full-voltage non-reversing motor starters must be combination type, 3-phase, NEMA style, NEMA rated single speed, non-reversing, across the line, magnetic type motor starters with motor circuit protector disconnect for each pump. They must be a minimum of NEMA Size 1 with fused control power transformer, control devices, and two spare auxiliary contact in addition to those used in the pump control circuit. The motor controller must be solid-state type overload relays and wired as indicated on the plans. 2.1.6.15 Generators Generator sizing (KW) will be detailed on the plans to operate all pumps plus miscellaneous load at 480-volt or 240-volt, 3-phase, powered with natural gas or diesel as indicated, and UL listed. Fuel supply as indicated on the plans. Subbase fuel storage tank, emergency stop pushbutton, and remote annunciator must be supplied as indicated on the plans. 2.1.6.16 CT Cabinets All CT cabinets must be 3-phase, 600-volt with amperage as noted on the plans, and be UL listed. They must be approved by the local utility company. 2.1.6.17 Instrumentation 2.1.6.17.1 Float Switches Float switches must be Teflon coated, stainless steel, direct acting type approximately 5 inches in diameter with potted single-pole double-throw (SPDT) mercury contact switch and narrow activation range all UL listed. Wiring must be 16-gauge, chlorinated polyethylene (CPE) jacketed cable of sufficient length to reach the junction box. Cable splicing is prohibited. Clamps for installation on a stainless steel suspension cable, the stainless steel suspension cable, and plastisol coated cast iron weight must be included with all float switches. Float switches must be normally opened contacts, hermetically sealed, and rated for use in sewage applications. 2.1.6.17.2 Level Transmitter Level transmitters must be submersible hydrostatic type constructed with welded 316 stainless steel with a Teflon coated elastomeric diaphragm. Accuracy must be ±0.25% of full scale and output a 4-20 mA Direct Current (DC) signal, 2-wire, loop powered with intrinsically safe barriers. Lightning protection must be included with all level transmitters. Cable length must be sufficient to reach the junction box without splicing. 2.1.6.18 Hazardous Location All electrical equipment that will be installed in a hazardous location must be classified in accordance with National Fire Protection Association (NFPA) 820 and have intrinsically safe circuits for instrumentation and barriers. 2.1.7 Heating, Ventilation, and Air-Conditioning Systems 2.1.7.1 Piping and Fittings 2.1.7.1.1 PVC Piping and Fittings All pipes and fittings called to be PVC must be PVC Schedule 80 manufactured from virgin rigid PVC with a cell class of 12454 in accordance with ASTM D1784. Pipes must meet PVC Schedule 80 Iron Pipe Size (IPS) in accordance with ASTM D1785 and fittings must be injection molded in accordance with ASTM D2467. Pipe and fittings must be manufactured as a system and the product of one manufacturer. Connections are to be as shown on the plans and typically consist of: 1. Solvent cement joints in accordance with ASTM D2564. 2. Threaded flange hardware is AISI grade 304 stainless steel. 2.1.7.1.2 Ductile Iron Piping and Fittings All piping required to be ductile iron must be AWWA C151, Class 54 ductile iron fittings in accordance with AWWA C110. Ensure pipe and fittings are cement mortar lined in accordance with AWWA C104 and have an exterior asphaltic coating when buried and red primer otherwise. Ensure connections are as shown on the plans and as follows: 1. Flanges must meet AWWA C115. 2. Flange hardware must meet AISI Grade 304 stainless steel. 3. Flange gaskets must be rubber and full face. 4. All piping and fitting coatings must be in accordance with the Special Provision for Pump Station Special Coatings. 2.1.7.2 Heating Heating is typically provided by electric unit heaters with performance as noted on the plans. In unclassified (non-hazardous) areas, heaters to be 304 stainless steel, washdown (NEMA 4X) rated, and UL listed. In corrosive atmospheres, use epoxy coating. In hazardous areas, unit heaters to be explosion proof electric unit heaters with epoxy coating, and National Recognized Testing Laboratory (NRTL) listed as meeting UL requirements. Thermostats to be integral to unit heaters and should turn on to maintain space at 50°F (adjustable) with manual switch operation for personnel comfort. 2.1.7.3 Ventilation Louvers to be extruded aluminum with 2 coats Kynar finish and stainless steel with an internal bird screen. Louvers to have vandal-resistant security bars within them. Intake hoods must have vandal-resistant security bars, stainless steel bird screen, and 24-inch-tall roof curb. The hoods and roof curb must be coated with Hi-Pro Polyester coating. Dampers in non-hazardous areas must be aluminum or stainless steel with Hi-Pro Polyester coating. Dampers in hazardous areas must be all aluminum construction and with spark resistant construction. Dampers must be thermally broken, parallel blade. Damper actuator enclosures must be NEMA 4X rated in non-hazardous areas or explosion proof rated in hazardous or classified areas. Fans should be aluminum or stainless steel construction with Hi-Pro Polyester coating. Refer to plans for performance requirements and other special equipment. Fan motors must be Totally Enclosed, Fan-Cooled (TEFC) in non-hazardous areas, and explosion proof in hazardous areas. Fans in hazardous areas must be of all aluminum construction and Spark A or B rated. Fan controls must be as noted on the plans. Fans to run automatically, and associated dampers should open when fans are called to run. Manual operation switch must also be provided. Fan intake and exhaust stack heights must be as indicated on the plans. 2.1.7.4 Hazardous Location All mechanical equipment that will be installed in a hazardous location must be classified in accordance with NFPA 820 and have intrinsically safe circuits for instrumentation and barriers. 2.2 Pictures of Materials

Sound Earth Granular Material Class III (Sand)

Class II Sand

34R Aggregate (open-graded) 46G Aggregate (open-graded)

21AA Aggregate (dense graded) 3 EQUIPMENT The following equipment can be used for pump station work: • Excavator • Backhoe • Front end loader • Crane • Trench box • Cofferdam • Occasionally, a bulldozer and a vibratory roller for aggregate compaction • Plate compactor • Ho-Pac attachment • Gas powered rammer tamping machine • Air powered pogo thumper hammer • Sand/stone box • Portable concrete mixer • Cement/mortar mixing tub • Portable generator • Electric submersible pump • Trash pump • Pipe laser with target • Transit or laser level • Leveling/grade rod • Electric impact wrench • Pipe/spud bar • Small hand tools (shovel, level, pipe cutoff saw, etc.) 3.1 Description of Equipment Equipment used to construct pump stations varies greatly. This is primarily due to the varying size of pump stations from small, precast stations with only one pump to large stations which have to be constructed onsite and have numerous pumps. • For small pump stations, the excavator may dig the hole for the new pump station, place the precast components, lower the pumps in place, and backfill around the structure. Front end loaders, bulldozers, and compactors are also used in the backfilling process. • For large pump stations, an excavator is used to dig the hole where the new pump station will go. A crane is used to move forms into place to cast the new pump station onsite. Excavators, bulldozers, front end loaders, and compactors are used to backfill around the new pump station. The crane is also used to lower the pumps and various other components into the pump station. For areas requiring soil stabilization during construction, either an excavator or a crane is used to install components of a cofferdam. Both utilize special attachments to allow installation of sheeting for the cofferdam prior to excavation of earthen material where the proposed pump station will be installed. 3.2 Pictures of Equipment

Rubber Tired Crane

Excavator

Excavator with Plate Compactor Attachment (Ho-Pac)

Bulldozer

Rubber Tired Backhoe

Portable Concrete Mixer Plate Compactor

Jumping Jack Compactor Cutoff Saws

Trench Box

Stone/Sand Box

Sheet Piling (cold rolled)

Trench Boxes 4 PRECONSTRUCTION Prior to the start of construction, the Inspector should perform the following: 1. Inspect materials upon arrival to site. a. Verify the materials meet the requirements contained on the plans, specifications, and any addenda. b. Visually inspect (VI) the materials for defects originating from the manufacturing process or occurring during delivery and unloading at the site (such as cracks, scratches, dents, deformities, etc.). Any damaged materials or equipment should be promptly rejected by the Engineer. c. Verify stockpiled materials are protected from weather and sunlight as required by the specifications and manufacturer’s recommendations. 2. Verify approved shop drawings, dewatering plans, temporary cofferdams, bypass pumping plan, temporary shoring/earth retention systems, flow diversion plan, tie-back plan, and all applicable documents that require approval were submitted by the Contractor and approved by the Engineer. 3. Verify the survey stakes are placed according to the plans and are appropriately labeled for the intended pump station component. a. Ensure proper offset stakes are placed in the location of the proposed pump station. 4. Verify MISS DIG has flagged existing private and MDOT utilities. a. Take note of any potential utility crossings and reference the plans and profiles to ensure minimum clearances are met. 5. Verify reinforcement has been installed according to the plans and shop drawings, this may require an outside inspection service or review from a building department. Refer to the plans and special provisions for special inspections. 6. Review all pertinent environmental restrictions in the plans, special provisions, and/or permits. a. These could pertain to endangered plant or migratory animal species, or to prevent spread of disease between plants and hazardous materials such as asbestos and petroleum products. 7. Review the plans and the Special Provision for Maintenance of Traffic. There may be restrictions or staging requirements for installation. Installation restrictions are typically associated with staging requirements on a project and access to side streets and driveways. 8. Review the plans and proposal for the following special provisions: a. Vibratory exclusion areas. b. Vibration monitoring. c. Demolition plan requirements. d. Asbestos removal. e. Non-hazardous contaminated material handling and disposal. 9. Obtain photographs of material tickets, storage method, and location. 10. Hold an onsite meeting with the Contractor to discuss: a. The construction methods that will be used to complete the work. b. Coordination the Contractor will have with utility companies. c. Methods or operations that will be used if existing facilities must be maintained during the work. d. Required traffic control measures, proximity of traffic to the work area, and maintaining driveways during construction. e. Identification of right-of-way and/or grading easements required to complete the work. f. Review of existing features, such as sprinklers, signing, or landscaping, in the vicinity of the work, and what methods will be used to protect them. g. Coordination and permit requirements for work on or near a railroad. h. Communication required if impacting residents or businesses during installation. • Residents and businesses should be contacted if there will be disruptions to services. Coordination by the Contractor with impacted users may be required if disruption is necessary. i. Review of local ordinances. j. Disposal of excavated material and material stockpile locations. The Contractor should provide authorization letters to the Engineer noting material stockpile and disposal locations. k. Soil erosion and sedimentation control measures that will be utilized to minimize soil erosion and subsequent sedimentation. l. Environmental restrictions and permits associated with the project site. m. Methods for securing the site during work operations and at the end of each workday. • Lockout/tagout procedures that will be followed onsite. 5 CONSTRUCTION 5.1 New Pump Station Construction Pump station construction begins with preparing the site for the necessary work. This may include removal of trees and brush but often begins with excavation for the pump station wet well. The plans will detail the depth at which the wet well will be installed. Excavation should be completed to the tolerances detailed in the special provisions prior to installing any base material. Typically a sand subbase and aggregate base are installed to distribute the weight of the wet well through the existing ground. This is dependent on the size of the structure. The base material under the wet well is considered structural and must be compacted in 6-inch lifts to 100% of the maximum unit weight for that material. Common practice is to pour concrete onsite to build the new pump station. The plans and special provisions should be referenced to ensure a masonry structure or use of form liners is not required to construct the new pump station. During form setting, care should be taken to ensure the construction joints and any holes in the pump station are built according to the plans. Once forms are set, concrete is poured and allowed to cure according to the specifications before any subsequent pour or backfilling can occur. Prior to backfilling, the structure must be waterproofed according to the specifications. Granular material Class III is commonly used for backfilling around a pump station. Backfill should be placed in lifts with passing density testing before the next lift is applied. After the pump station structure is built and backfill has been placed around it, the mechanical and electrical components are installed within the pump station. All holes where electrical conduit or wiring pass through the structure must be sealed according to the specifications. Follow the details and special provisions for installation of all electrical and mechanical components. All project specified tests must be performed and approved prior to final acceptance of any electrical and mechanical component. 5.2 Work on Existing Pump Stations Most frequent pump station work consists of maintaining existing pump stations. This work varies in nature but commonly includes the replacement of various components within the pump station. This could include the replacement of pumps, control panels, valves, and the wiring required to connect these various components. The plans and specifications will detail the components required to be replaced. Careful attention should be given to the size of the existing and new components to ensure reconfiguration of other components inside the pump station is not needed to facilitate replacement of the desired component. Construction begins with locating the component(s) to be replaced. Ideally, only the components getting replaced are taken out of service. Although, for certain work, the entire pump station must be shut down for replacement of a component. Once the component(s) is isolated from the system, the Contractor will work on disconnecting and removing the component(s). After the existing component is removed, the mounting bracket must be reviewed to ensure it works with the new component. If the existing mounting bracket does not work with the new component, a new mounting bracket must be installed. For mounting brackets requiring the use of epoxy, mortar, or other like compounds, sufficient time should be permitted for the product to cure before mounting the new component. The new component is then installed in the pump station on the mounting brackets and connected into the system. Some projects have special provisions detailing a testing and integration period to verify operation of the new component prior to final acceptance. 6 INSPECTION & TESTING 6.1 Inspection The Inspector should utilize, at a minimum, the following tools to perform the required inspection: • 100-foot tape measure or longer • 25-foot tape measure • Measuring wheel • Chaining pin • 6-foot stick ruler • 4-foot level • Working plans • As-built sheets to update the plans • Survey equipment • Camera The Inspector should take the following steps during construction: 1. Verify the proper diameter of structure is supplied (both exterior and interior dimensions need to be checked). 2. Verify the correct number, size, and locations of holes for pipe are formed in the structure. 3. Paint marks in 6-inch increments on the structure to ensure backfill is being placed in appropriate lift depths. 4. Monitor excavation of the trench to ensure it meets the elevation requirements shown on the plans. 5. Verify the structure is set plumb according to the limits of the specifications. 6. Verify all bedding and backfill of excavated trenches is clean, dry, and meets design requirements. a. Verify there is no debris in the trench prior to backfilling. 7. Verify the form tie holes are filled with mortar and waterproofed prior to backfilling. 8. Verify waterproofing is applied to the structure as detailed on the plans. 9. Verify all coatings are applied in accordance with the special provisions. 10. Obtain grade shots and document the grades on the as-built plans. 11. Verify passing density tests are obtained on each lift of backfill material. Density for backfill must be achieved for each lift before subsequent layers are placed: a. Structure Embankment: The maximum lift thickness permitted is 6 inches after compaction. Density needs to achieve 100% compaction. b. Non-Load Bearing Backfill: The maximum lift thickness permitted is 12 inches after compaction. Density needs to achieve a minimum of 95% compaction. c. Regardless of the intended load bearing capacity, density checks on backfill should occur on every lift. 12. Record the density testing results of the backfill material in accordance with the Density Testing and Inspection Manual using the field established maximum density for the material being tested. The minimum testing frequency is shown in Appendix K (backfill) of this manual. The testing frequencies listed are minimums that are satisfactory for acceptance. However, it is emphasized that project conditions normally require more frequent testing for proper density control. 13. Perform a moisture test on the aggregate material if payment is based on weight. 14. Ensure the appropriate test is used to determine the maximum density of the material: a. The One-Point Michigan Cone if natural or slag aggregates are used; or b. The Michigan Modified T-180 if crushed concrete is used as detailed in the Density Testing and Inspection Manual. c. All excavated material should be either removed from the site or stockpiled for testing to be approved for re-use onsite. 15. Verify the excavated area is secured according to contract documents if backfilling is not completed the same day as excavation. 16. Document any deviations from the original plans or specifications and ensure they are properly addressed before proceeding with further construction activities. Ensure construction is performed in accordance with plans, specifications, and shop drawings. VI and document all accepted portions of the constructed pump station. Fabrication imperfections or construction damage to pump stations must be repaired by the Contractor, as approved by the Engineer, in accordance with Section 712 of the Standard Specifications for Construction for all concrete or masonry components and at no additional cost to the contract. Natural aggregates must be provided in accordance with Section 902 of the Standard Specifications for Construction if the pump station is located near a waterway. Crushed concrete is not allowed for any work within 100 feet of a waterway. Check that materials being delivered to the project site are from the MDOT Prequalified Aggregate Supplier List. If a material is not being delivered from an MDOT prequalified pit, verify the material has documentation showing passing QA results. Salvaged existing material may be used after passing results are obtained from QA testing of an onsite stockpile. All reinforcing steel must be epoxy-coated regardless of use. Refer to Section 905 of the Standard Specifications for Construction for additional steel reinforcement information. 6.2 Testing For evaluation of aggregate materials, use only certified aggregate sampling and testing technicians. Refer to the Procedures for Aggregate Inspection manual and project specifications for testing requirements and frequencies. The Engineer should track the approved testing of installed aggregate and coordinate with the respective testing lab to ensure the required number of aggregate tests for the project are being completed. For every new source, new day, or suspected change in material, a moisture check must be completed. Obtaining moisture readings from a nuclear density gauge is only an approximation and is often used as a guide in the field. Official determination of moisture content will be made from a field sample stored in a plastic bag with the moisture content checked for payment using the oven dry method only if it is paid for by weight. Perform density testing on compacted backfill. All backfill, regardless of material used, must be compacted to at least 95% of the maximum unit weight. Density tests need to be taken as close to the pipe as possible to obtain accurate information. To ensure excessive deformation of the pipe does not occur after backfilling and compaction, mandrel testing must be performed on at least 50% of all plastic pipe sizes. Refer to Division 4 of the Construction Manual for more information on mandrel testing of plastic pipe. Additional testing may be required for water tightness and pressure testing of the pump station piping. Refer to the special provisions for additional requirements. Start-up activities, including building inspections, electrical inspections, setting floats, and control system set-up may be required. Refer to the special provisions for additional requirements. 7 MEASUREMENT, DOCUMENTATION & PAYMENT 7.1 Measurement and Payment Measurement and payment of pump stations is typically described within the project special provisions. In situ material from the job site may be used for backfilling after the Contractor completes gradation testing of samples taken from an onsite stockpile. The respective MDOT materials lab will confirm the gradation of the onsite material meets the requirements for the desired backfill material. 7.2 Documentation The Daily Work Report (DWR) should show all computations, measurements, and supporting documentation needed to verify the quantity submitted for payment. Primary supporting documentation includes moisture and grade checks. Additional documentation once the work is completed should include: 1. Length, width, and height being paid on each date. 2. Survey or other approved methods for verification that the foundation and structure was constructed in conformance with the contract documents. 3. Volume and tonnage of bedding and backfill material placed. Form 1900, Aggregate Inspection Daily Report, will need to be completed for every sublot of aggregate to track gradation acceptance. Form 0582B, Moisture & Density Determination - Nuclear Method, is used to record density testing results. Delivery tickets must be verified for the source of material against the approved Materials Source List. Each ticket must include the required information. Refer to Subsection 109.01.B.6 of the Standard Specifications for Construction for the information required on each ticket. 8 LOCAL AGENCY PROJECTS Local agency projects sometimes have details and specifications for pump station construction. These standards are to be followed while working on a local agency project. 9 RAIL PROJECTS -Reserved-

[top of page]

---