Our History
The Nelson Regional Sewerage Scheme (NRSS) is a unique solution to an environmental problem facing every community – the safe and proper disposal of its wastes.
Its construction is the result of the efforts of three neighbouring local authorities and three major industries that cooperated over a ten year period to find an acceptable method of dealing with domestic and industrial wastes that, in the past, severely polluted the shallow and ecologically sensitive Waimea Estuary.
It is the largest single project ever undertaken by local authorities in the Nelson region.
The development of the Nelson Regional Sewerage Scheme can be split into two stages; the first was driven by environmental considerations and the need for a cost effective sewage treatment solution. This resulted in the creation of the Nelson Regional Sewerage Authority (NRSA), which was comprised of members from the three local authorities concerned and the industrial customers. This first stage began in the 1970s and was finalised in 1983 with the opening of the physical works comprising the NRSS.
The second stage was driven by legislation and the need for a more professional approach to managing local authority infrastructure, and this resulted in the establishment of the Nelson Regional Sewerage Business Unit in 2000.
Formation of the Nelson Regional Sewerage Authority (NRSA)
The Nelson Regional Sewerage Authority grew out of a voluntary regional planning committee, which existed when the idea of a regional sewerage scheme was first raised. That committee undertook the initial investigations.
When the Nelson, Richmond and Waimea Councils agreed to pursue the scheme jointly, a separate committee was established with representatives from each. This committee took full responsibility for the planning of the scheme and details such as land purchase, loan raising and deciding on the cost sharing formula.
On March 30 1981 the formal agreement setting out the terms of each Council’s membership, how the scheme should be administered and how costs should be shared was signed, and the Nelson Regional Sewerage Authority officially came into being.
Why a regional scheme
To protect the waters of the Waimea Estuary and adjacent areas of Tasman Bay, higher effluent standards were required. This resulted in the need for a new scheme.
In 1970, Nelson City Council realised the effluent from its Stoke treatment plant was not likely to meet the new water requirements and commissioned a report that identified the inadequacies of the system.
The report recommended the best long-term solution, both economically and environmentally, would be to build a combined scheme with Richmond Borough and the industries that had been established in nearby Waimea County.
At the same time, Richmond Borough was considering upgrading its treatment plant and outfall, while the industries were discharging untreated wastes into the estuary.
As a result, in 1973 the Nelson Regional Sewerage Committee was set up with representatives from Nelson City, Richmond Borough and Waimea County councils.
It considered a report on alternative strategies for dealing with the wastes at that time flowing into the estuary. The report recommended a scheme for collection, treatment and disposal of domestic effluent from the Stoke-Tāhunanui suburban area of Nelson city and all of Richmond Borough, and industrial effluent from the four major industries sited on the edge of the estuary – then the Apple and Pear Board’s processing factory, the Nelson freezing works, Nelson Pine Forest’s chip mill and Kempthorne Prosser fertiliser works. In 1977 the fertiliser works withdrew from the scheme. Today, these businesses are: ENZA foods site, Alliance Freezing works and Nelson Pine Industries.
Moving forward with a scheme
The committee decided to pursue a scheme and started with selecting a site. Four alternatives had been put forward in the report. The favoured option involved building treatment ponds in the estuarine channel between Best and Bell Islands. However, after local objections, the committee reconsidered and in 1976 bought the 120ha uninhabited Bell Island as its site.
In 1978, after extensive environmental investigations and planning procedures including several appeals, water rights and planning consents were granted.
Positive results from the scheme
Combined financial budgets produces savings
Combined management efforts produces efficiencies
Better environmental conditions in region
Greater degree of treatment of wastes
Better method of effluent release made possible by combined treatment and disposal
Treating effluent from a single source leads to significant improvement in water quality.
Savings by councils and industry from not having to upgrade individual treatment systems
Pooling resources achieves cost savings
Discharging highly treated effluent into the estuary
The Waimea Estuary presents considerable difficulties for the discharge of effluent. Disposal in shallow areas is liable to lead to concentration of nutrients and the growth of undesirable and environmentally degrading plants and algae. Public health safety must also be protected because of the recreational areas in the estuary and the beaches near its mouth.
Discharge in the head of Tasman Bay outside the estuary would be very costly and encounters problems with the shallowness of the water, the proximity of the beaches and conflicts with the shellfish resources.
The object of the scheme is to provide a high degree of treatment with particular emphasis on bacterial reduction, and to discharge well treated effluent only on the early phase of the outgoing tide in a position which ensures rapid mixing and interchange with the sea.
The treatment and mixing assures public health safety and the release times avoid significant nutrient accumulation in the sensitive upper reaches of the inlet.
The scheme was designed to cope with a peak daily volume of 52,000 cubic metres of wastewater. Industrial wastes account for nearly half the total volume.
There is sufficient storage on-site to ensure that the outflow to the estuary is limited to a maximum of 25,000m3 in one day.
Pipeline route
The final route selected was from the Pine Industries location around the estuary to Monaco, collecting flows from Richmond and the other two industries, and a second pipeline moved from the existing Stoke treatment works connecting into the system at Monaco. Then, a single pipeline crossed the estuary to the treatment site.
Treatment process
The treatment system consisted of an aeration basin, three facultative ponds and two maturation ponds.
After a total of 30 days in the pond system, the fully treated waste (90 percent of its BOD) is discharged through the outfall diffuser into the waters of the estuary on the first three hours of each outgoing tide.
The salt water rapidly kills the algae in the effluent and the now neutralised waste is flushed out into Tasman Bay. It was estimated that the number of faecal coliform (disease-causing baceria present in sewage) at the estuary entrance will not exceed 60 per 100ml. This is well within the classification standard of 200 per 100ml.
Construction and opening of the facilities
Work began in November 1981 with the laying of the pipeline and work on the treatment ponds started in May 1982. Final construction was completed in 1983 and the Minister of Health, Hon. AG Malcolm, opened the facilities on 29 November 1983. Administrative management of the Nelson Regional Sewerage Scheme was formalised in March 1981 prior to the start of official construction works.
The Waimea County Council administered the scheme from its inception and when the scheme was officially formed in 1981 the Council’s executive officer became secretary to the Authority. Nelson City Council engineers were responsible for the supervision and day-to-day running of the scheme. This structure was modified slightly when the Waimea County and Richmond Borough Councils were amalgamated into Tasman District Council in 1989. The role of Nelson City Council remained the same but the administrative and secretarial responsibilities of the former Waimea County Council were assumed by Tasman District Council. This was the modus operandi until an Audit NZ report in 1998 identified a number of opportunities for improvement. This ultimately lead to the founding of the NRSBU in 2000.
OUR HISTORY
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