The operation of force main-lift station systems is usually automated and does not require continuous on-site operator presence. However, annual force main route inspections are recommended to ensure normal functioning and to identify potential problems.
Special attention is given to the integrity of the force main surface and pipeline connections, unusual noise, vibration, pipe and pipe joint leakage and displacement, valving arrangement and leakage, lift station operation and performance, discharge pump rates and pump speed, and pump suction and discharge pressures. Depending on the overall performance of the lift station-force main system, the extent of grease build-up and the need for pipeline pigging are also assessed.
If there is an excessive increase in pump head and the head loss increase is caused by grease build-up, the pipeline is pigged. Corrosion is rarely a problem since pipes are primarily constructed of ductile iron or plastic, which are highly resistant to corrosion. Buildup can be removed by pigging the pipeline.
Force main costs depend on many factors including:
Conveyed wastewater quantity and quality
Force main length
Soil properties and underground conditions
Pipeline trench depth
Appurtenances such as valves and blow offs
These site and system specific factors must be examined and incorporated in the preparation of force main cost estimates.
Unit force main construction costs are usually expressed in $ per linear foot of installed pipeline and costs typically include labor and the equipment and materials required for pipeline installation. Costs are usually base installation costs and do not include the following:
General contractor overhead and profit
Engineering and construction management
Land or right-of-way acquisition
Legal, fiscal, and administrative costs
Interest during construction
Force main operation and maintenance costs include labor and maintenance requirements. Typically, labor costs account for 85 to 95 percent of total operation and maintenance costs and are dependent on the force main length.
The maintenance costs usually vary from $9 to $26/meter ($3 to $8/linear foot), depending on the size and number of appurtenances installed on the force main. An internal inspection using TV equipment can be completed, if visual inspection is not sufficient. TV inspection can be costly, ranging from $1,300 to $15,250 per mile with an average cost of $6,120 per mile.