The most labor-intensive task for lift stations is routine preventive maintenance. A well planned maintenance program for lift station pumps prevents unnecessary equipment wear and downtime. Lift station operators must maintain an inventory of critical spare parts. The number of spare parts in the inventory depends on the critical needs of the unit, the rate at which the part normally fails, and the availability of the part. The operator should tabulate each pumping element in the system and its recommended spare parts. This information is typically available from the operation and maintenance manuals provided with the lift station.
Performance of routine and preventative maintenance can save the onsite lift station owner from costly repair bills. The following are suggestions that may insure fewer breakdowns and problems:
* Wet wells should be pumped out and cleaned at least twice a year, or more often if necessary, to prevent solids and grease build-up. Build-up of solids can create odors and damage the pump.
* Inspection of submersible pumps should be performed quarterly. Inspection of the impeller should be performed quarterly or when motor hours are not within 10% of each other. The inspections would assure that the impeller is free of debris.
* Inspection of the check valves should be performed at least twice a year to insure proper working order and to prevent backflow from the force main to the wet well.
* Cleaning and inspections of floats four times a year assure proper performance. The buildup of grease prevents floats from working properly.
* Inspection of the light and alarm systems should be performed weekly. An alarm system in working order can alert you to problems immediately.
* Installation of hour meters on each motor will give one an accurate record of how often each motor is cycling; and hence, the amount of water being pumped through the system. A logbook of motor hours, dates and maintenance performed should be kept.
* Amp readings should be taken at least once a month on each motor in the on-site lift station. If the amp readings do not meet the manufacturer’s specifications, it is an indication that debris is lodged in the propeller within the motor, or that water has entered the motor housing or the wiring.
* A semi-annual inspection of all electrical motor control equipment to find poor connections and worn parts should be performed.
* Connection points to a generator in a lift station should be checked and tightened annually.
Costs Lift station costs depend on many factors, including:
* Wastewater quality, quantity, and projections
* Zoning and land use planning of the area where the lift station will be located
* Alternatives for standby power sources
* Operation and maintenance needs and support
* Soil properties and underground conditions
* Required lift to the receiving (discharge) sewer line
* The severity of impact of accidental sewage spill upon the local area
* The need for an odor control system
These site and system specific factors must be examined and incorporated in preparing a lift station cost estimate. The most important factors influencing cost are the design lift station capacity and the installed pump power. Another cost factor is the lift station complexity.
Factors which classify a lift station as complex include two or more of the following:
Extent of excavation
Congested site and/or restricted access
Extensive dewatering requirements, such as cofferdams
Site conflicts, including modification or removal of existing facilities
Special foundations, including piling
Dual power supply and on-site switch stations and emergency power generator
High pumping heads (design heads in excess of 200 ft)
Mechanical, electrical, and control equipment delivered to a pumping station construction site typically account for 15 to 30 percent of total construction costs. Lift station construction has a significant economy-of-scale. Typically, if the capacity of a lift station is increased 100 percent, the construction cost would increase only 50 to 55 percent. An important consideration is that two identical lift stations will cost 25 to 30 percent more than a single station of the same combined capacity. Usually, complex lift stations cost two to three times more than more simple lift stations with no construction complications.