Levin

The system was installed in the mid 50s. It consists primarily of glazed earthenware (GEW) gravity network leading towards a treatment Plant at the Western end of Makomako Road beside Lake Horowhenua. Seven pump stations serve low lying parts of the town.

The Wastewater is fully treated with inlet screens and grit trap, primary clarification, sludge digesters, trickling filters and a solids contact and reaeration tank followed by a secondary clarifier and aerated ponds.

The treated effluent is pumped through a 7 km long pipeline to the Effluent Disposal site commonly known as "the Pot". The effluent is contained in a basin formed amongst the sand hills and is pumped out and spray irrigated onto the surrounding land.

The operation parameters of the scheme are:

Population served: 15,400
Connections: 6,431

Consent Requirements

Resource consents are held for discharges at the Levin Wastewater Treatment Plant and Effluent disposal site respectively. These cover discharges to air, discharges to groundwater and discharge to land.

The discharge parameters for effluent quality at the Levin Wastewater Treatment Plant, prior to discharge to the Pot are 40/40 g/m3 CBOD5/SS.

The term of these consents is 20 years.

A separate resource consent is held for the discharge to air from the soil filter and the gas flare. This consent expires in May 2005.

The consent for the discharge to groundwater at the treatment plant expires in 2009, and it requires that significant progress is made in reducing this discharge. Council has determined that the sludge drying system (which contaminates groundwater and gives rise to odours) be decommissioned after a dewatering machine has been commissioned. That work is programmed for 2003/2004. The sludge will continue to be spread on land at the Pot, or used as soil conditioner on completed parts of the Levin Landfill.

Current Issues

The transfer system to the pot is limited incapacity to around 16,000 cubic metres per day and the average flow is around 6,000. Very occasionally the amount of water entering the sewers has exceeded this capacity for an extended time, resulting in an overflow into the lake. The most recent such event occurred in 1998. As a result a working party was set up to review the system and it proposed a new sewerage strategy as follows:

That stormwater connections to the sewer continue to be subject to a regular programme leading to minimising the incidence of inflow.
That sewer pipes continue to be subject to a regular programme leading to minimising the incidence of infiltration and overflow.
That Council take no further the idea of lowering the groundwater by draining it through the upper aquiclude.
That Council give urgency to increasing the capacity of the transfer system to the Pot.
That Council secure further land for the disposal field, either at the present location as an extension to it, or at a new location.
That the additional capacity be provided by pumps at an alternative location, which will become the primary transfer system with sufficient capacity to carry four times the dry weather flow, allowing for population growth and laid to the new disposal site.
That the new pump station be located where there is reduced risk of overflow to the Lake: if not possible, then that station shall be designed and managed to minimise the risk.
That the existing pump station continue to be used until such time as the new pump station/transfer system is operational. In the meantime risk management principles should be adopted, in conjunction with Tangata Whenua, to manage the possibility of failure leading to overflows into the Lake, with particular attention to contingency measures to deal with the failure of the rising main, as it approaches the end of its service life.
That Council relocate the treatment plant to a new site in the perpetual ownership of the Council once the location of land for the disposal field is secured.
That Council, when undertaking the planning for the works described above, undertakes full and proper consultation with affected parties.
That the strategy be completed as soon as practicable, and, because of the long timeframes involved in consultation and planning, work on this should begin immediately.

This strategy was adopted by Council in October 2002.