By Don Farmer
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Slashing the amount of treated effluent discharged into Mangaterere Stream and the building of a huge reservoir on Daleton Farm to hold wastewater collected in the winter months are on the drawing board for Carterton.
District councillors will discuss a detailed report at tomorrow’s final council meeting of the year which outlines plans for the town’s sewage treatment plant and irrigation scheme prior to Resource Consent for the work being sought from Greater Wellington Regional Council.
Existing consents for the plant and irrigation expire in October next year.
The new application aims to secure consent for the maximum allowable term of 35 years.
Council chief executive Jane Davis said the stage two development would mean wastewater would continue to be irrigated to land during the summer months but instead of having to mostly discharge into the stream during wet winter months when the soil was too saturated to absorb it, the effluent would be stored in a 200,000m3 capacity reservoir.
Any treated effluent that could not then be irrigated to land would be released into the stream only at times of high flow.
To help with disposal, the plan is to install a second centre-pivot irrigator and to open up far more of the Daleton Farm area than is now being used for the discharge to land.
Ms Davis said the “overall objective” of the project was to minimise the occasions when treated effluent had to go into Mangaterere Stream and the stage two proposal would achieve that.
The first stage of the project was finished in 2014, with partial development of Daleton Farm.
This saw the installation of a centre-pivot irrigator that has been summer irrigating to 20ha, or half, of the site.
During the first two years of operation, long summer periods had resulted in no discharges into the stream for four or five months of each year.
This, along with a noticeable drop in nutrients from trade wastes had brought about improved water quality in the stream.
Stage two work would include relocating the discharge outfall which now feeds into an unnamed tributary of the Mangaterere Stream close to the wastewater treatment plant.
It would be moved to the true left bank of the Mangatarere Stream just upstream of the bridge across State Highway 2 where research has determined river flows to be much higher than at the existing discharge point.
Ms Davis said although the council aims to produce a plan which is innovative and maximises the use of Daleton Farm, councillors recognise forecasted costs for the project need to be affordable.
“Making sure what we do is affordable while providing a sustainable development plan is key for our ratepayers.
“However, it is incredibly important to invest in our wastewater treatment infrastructure, supporting growth which will take us into the future,” she said.
Councillors are expected to support stage two, at least in principle, at tomorrow’s meeting along with the framing of the draft consent application.
The plan, if adopted, would be completed over a three-year span with the estimated cost of the project being $6.8 million over 10 years.
This would mean a sewer rate increase for Carterton town ratepayers of about $5 a week, or roughly $260 a year, for the first year, and smaller increases for the last two years of planning.
