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Levin Wastewater Treatment Plant

Fuseworks Media
Fuseworks Media

21 August 2008 - Horowhenua District Council staff continue to be intrigued by allegations made by the Green Party in relation to its Levin wastewater treatment plant. The suggestion that this is turning out to be a sewerage disaster is simply political point scoring.

Council staff and its contractors are working against the forces of nature to ensure that the risk of environmental impact is held at bay. It is extremely disappointing that the Greens have chosen to offer wide ranging criticism, much of it based on speculation rather than fact, when surely a far more sensible approach would have been to offer credible solutions.

The effect of heavy rainfall contributing to higher than average rainfall levels in July and August continues to play havoc on groundwater levels throughout the Horowhenua District. In many parts of the District, residents will be noticing water ponding in areas never before seen, with drainage taking considerably longer than normally expected.

Council staff, who regularly monitor groundwater levels note that in many areas of the District groundwater levels have already exceeded previous record levels. Whilst currently the rainfall has ceased, unfortunately the effect will continue to impact on groundwater levels for some time.

The groundwater levels are continuing to put pressure on Council infrastructure, particularly stormwater and wastewater systems. Council staff are continuing to monitor the level of the Levin wastewater ponds around the clock. Late last week, as a result of significant gains made, the levels of the buffer storage ponds had almost returned to normal levels. During normal circumstances, the daily inflow into Councils wastewater plant is around 400 cubic meters per hour. Our outflow pumping capacity is 695 cubic meters per hour. As a direct result of the rainfall and the impact this has had on groundwater levels, from Friday last week inflow levels reaching 1,400 cubic meters per hour were entering the plant. Naturally this is placing pressure on the buffer ponds storing treated effluent. Readings this morning show the inflow to have reduced to around 1,100 cubic metres per hour.

Reference is often made to an incident in 1998 where effluent flowed into the Lake and there has been some uninformed comment around what Council may or may not have done since that time. Prior to the 1998 event, Council had approximately 15,800 cubic metres of treated effluent storage. During the 1998 event Council added a further 8,200 cubic metres of treated effluent storage. Since then, in order to mitigate any negative environmental or cultural effects, Council has undertaken significant works to its Levin wastewater system and at its Levin Wastewater treatment plant. These include:

- In 2002 we added a further 13,800 cubic metres of storage. - Over the past 4 weeks we have increased the height of the bunding walls around the existing ponds thereby creating a further 8,300 cubic metres. - We are currently (Tuesday evening) completing work on the creation of an additional storage paddock which will add a further 23,000 cubic metres - over the last week we have enhanced our outflow pumping system to increase capacity from 14,500 cub metres per day to 16,500 cubic metres per day. - we have replaced 173 laterals with a combined length of 1,132 metres, - we have replaced 22 manholes, - we have replaced 133 sections of sewer pipe over a length of 9,628 metres, - engaged a fleet of suction trucks working 12 hours a day, - created a channel to divert groundwater around the treatment plant. - engaged an independent geo technical consultant to inspect the bund walls around the ponds.

The bunding of an additional pond is for protection against the further impact of the high ground water levels, not because the capacity of the existing ponds is insufficient.

All of these works have been funded from rating sources - there has been no offer of financial assistance by either Central Government or the Regional Council. Council staff continue to maintain dialogue with all directly affected parties on the ever changing situation. We are also taking water samples daily from both the Lake and from the storage ponds.

It is important that we acknowledge that the buffer storage ponds hold treated effluent. Council continues to explore all possible options to expand its buffer storage capacity for this treated effluent and mitigate any negative environmental or cultural effects on surrounding properties. We are mindful that the impact of groundwater levels will continue to be with us for some time, whilst at the same time we continue to explore all possible options to retain storage.

The situation that Council is currently facing is outside its control - we are dealing with highest ever recorded groundwater levels - a result of an act of nature, not an act of Council. In planning for infrastructural capacity needs, consideration is always given to existing demands, previous recorded levels, assessed risk and financial affordability. In designing its current plant Council took all of these issues into consideration - as noted earlier, all previous recorded highs have been significantly exceeded.

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