Nelson City Council

With 61 submissions received on the Nelson Regional Sewerage Business Unit’s (NRSBU) regional pipeline upgrade strategy for the Bells Island Wastewater Scheme, NRSBU is analysed submissions and met to discuss them on 3 April. Twelve submitters spoke to their submission. The NRSBU has made its recommendation to both Councils.

The existing issue

Sewage from the service area is treated at the Nelson Regional Sewerage Business Unit's (NRSBU) Bells Island Treatment Plant and discharged into one of the main channels of the Waimea Estuary on the outgoing tide. In recent months the NRSBU has identified a critical issue with the sewer pipe for this treatment plant.

NRSBU's strategy for the regional pipeline upgrade is driven by two key concerns:

1. The risk of a pipeline failure in the estuary between Monaco and Bells Island - identified as an extreme risk - that would necessitate repairs that could take a significant time to complete.
2. The present pipeline to the Bells Island Wastewater Treatment Plant cannot handle present flows, let alone future higher flows. It is likely there will be an increasing frequency of overflow discharges to the Waimea Inlet during extreme wet weather.

Why consultation is necessary

In order to make the necessary upgrades to repair this critical pipe fault, the NRSBU is required to apply for resource consent and must, therefore, seek public consultation on its proposed plans.

Nelson Regional Sewerage Business Unit (NRSBU)

The Nelson Regional Sewerage Business Unit is a joint committee of the Tasman District and Nelson City Councils and was instigated to look after the owner’s (the two Council’s) interests in the Regional Sewerage Scheme. It was set up as a business unit in October 2000 and previously operated as the Nelson Regional Sewerage Authority. A Memorandum of Understanding that was signed by the two Mayors and CEOs in December 2000 governs the operation of the NRSBU.

Area covered by the NRSBU

The NRSBU treats municipal wastes (mainly domestic sewage) from Nelson City, Stoke, Tahunanui, Richmond, Wakefield, Brightwater (the Waimea Basin) and Mapua as well as industrial wastewater from Alliance Nelson,ENZA Food, and Nelson Pine Industries. The Councils also have additional sewerage schemes and associated treatment and disposal schemes.

The proposed strategy

Suggested upgrade options

Upgrade options focus on addressing both key concerns outlined above. 

Three upgrade concepts have been identified - labelled Options A, B, and C - and are described as follows:

A

New pipework continues to direct flows in an anticlockwise flow direction around the Waimea Inlet, as at present.

B

New pipework reverses the present flow direction to a clockwise direction around the Waimea Inlet, allowing the existing estuary crossing from Monaco to Bells Island to be abandoned and avoiding other new significant estuary crossings.

C

New pipework directs flows in both directions around the Waimea Inlet for maximum operational flexibility and more effective utilisation of existing assets.

Sub-categories relating to pipe location

Within each of these three fundamental options, three further sub-categories relating to the location of the pipelines within or beyond the estuary boundaries have been considered:

1. Pipelines are kept out of the estuary, except for a short crossing from Bests Island to Bells Island at the present tidal road access causeway.
2. Pipelines are land based as much as practicable, following the estuary shoreline to reduce the length of pipeline needed and reduce installation costs.
3. Pipelines continue to cross estuary, reducing pipeline lengths and keeping costs to a minimum.

Evaluation of options

The evaluation of the different options must take into account four principle factors:

• cultural
• social
• environmental
• economic

For instance, the laying of wastewater pipelines in an estuarine environment, and even the siting of the present treatment plant within this environment, is of concern to many people. Additionally, with increasing pressure on agricultural water supplies in the region, future longer term planning may include considering the relocation of the present treatment plant inland so that treated effluent can be productively applied to land. How the different options might provide for future growth is also important.

In addition to these considerations, the following principles will be important to the evaluation of the options:

1. Maximum economic benefit from existing plant and infrastructure should be achieved.
2. All viable means of reducing the carbon footprint should be considered.
3. The options should lower the use of non-renewable energy and work towards optimising energy efficiency. Energy generation will be considered.
4. The minimisation of waste streams – domestic and industrial – should be encouraged.
5. An ongoing effort to lessen the cost of the treatment process to customers.
6. Alternative sites, away from the coast, will be considered in areas of future growth.
7. Continue to consider treatment at source in order to minimise energy costs and maximise reuse opportunities.
8. Include international best practice and sustainability policies in all decisions.

 Download the full report

Full Bells Island Pipeline Upgrade Consultation strategy document (PDF @ 900KB).

Contact

For more information contact Senior Executive Infrastructure, +64 3 546 0309.