Okara Park pump station upgrade

Many sewer pump stations in New Zealand are reaching the point where significant upgrading is required either because of their age or due to insufficient capacity.

This paper looks at the upgrades that were made to one such station in Whangarei.

The problems and solutions addressed in this paper include:

• Design of the construction sequence to enable continued safe operation of the station
• Increasing the suction pipes between the wet well and drywell from 300mm diameter to 600mm diameter
• Fitting pumps into the drywell when the pumps are nearly as high as the drywell itself
• Installing a second rising main into the existing station
• Safe operation of pumps when the wetwell was significantly smaller than desirable
• And many other details that are made more difficult by the limited space in the existing station and the need to keep the existing station operational at all times.

The pump station and rising mains are now fully operational. The station can now pump more than twice its original flow rate and has less kW’s of pumps installed. Overflows from this pump station as a result of insufficient pump capacity should no longer occur.