Lift Me Up

The Lake Mills Wastewater Utility has determined that to serve the customers in the Lake Street Alleyway area, because of the topography, the physical features of the earth, and the current design standards require that grinder pumps be installed at seven properties on Lake Street to be able pump sewage into the pipe of the downstream gravity pipeline.
Sewage lift/pump stations are used for pumping wastewater or sewage from a lower to higher elevation, particularly where the elevation of the source is not sufficient for gravity flow and/or when the use of gravity conveyance will result in excessive excavation and higher construction costs.
Four alternatives are available for the design of a wastewater collection system to serve the alleyway. The four alternatives are described as follows:
1. Gravity sewers with several private grinder pumps.
2. Gravity sewers with one public lift pump station.
3. Raising in-building plumbing to gravity flow; or
4. No action
The Utility's policy has been to construct gravity sewer line unless there is no other option. Where there are twenty or less users and gravity is not an option, individual Low Pressure Sewer Systems are the recommended option. Studies consistently show that cost analysis of Low Pressure Sewer Systems is the preferred option to lift stations in small service areas. One study reviewed four completed subdivisions to determine if grinder pumps would have been a realistic alternative. One of these was a 12 lot project where a lift station was installed. The comparative costs were:-
Lift Station and Gravity Sewer Cost for 12 Lots
$144,100.00
Cost Per Lot
$ 12,008.00
Pressure Sewer Cost For 12 Lots
$ 75,900.00
Cost Per Lot
$ 6,325.00
The cost of the pressure sewer system is only 53 per cent of the cost of the gravity system. The report concludes that any development of twenty homes or less where a lift station is required will find pressure sewers and grinder pumps to be a cost- effective alternative.
Key disadvantages of public lift stations include the high cost to construct, maintenance and the potential for odors and noise. Odors and corrosion are a problem in small service areas because the wastewater in the lift station goes septic because the pump does not pump often enough. The wet well of a lift station should be as small as possible in order to minimize detention time of the sewage. Should the wastewater remain too long in the wet well, septic action may occur. Although, the wet well should be large enough so excessive starting and stopping of the lift station pump will not take place.
The lift station would take up two parking spaces in the area and might be viewed as a negative appearance. Lift stations also require a significant amount of power, are sometimes expensive to upgrade, and may create public concerns and negative public reaction.