Jeffreys replacement water tank alternative option

The earthquake – damaged below ground suction tank at Jeffreys Pump Station needs to be replaced as soon as possible, so that all four deep wells on site can be connected. This will ensure security and resilience for the Northwest water supply network. The existing 200 cubic metre suction tank is not in use, and only two wells are directly connected to the water supply. At the moment water is supplied from other wells in the network when there is high demand in the area.

When all the four wells are connected, Jeffreys Pump Station will exceed pre-earthquake supply capacity and meet design standards for at least 500 cubic metres per hour with a one hour buffer capacity.

This will ensure water quality at all times including peak demand, including the ability to treat the water in an emergency if needed. A stand-by diesel generator supports the pump station during emergency power failure.

The concept design and location put forward for comment in October last year was chosen because of its low capital cost, compliance with resource consent requirements and low impact on useable park space.

Key issues raised by most of the 35 submitters included the size, shape and proximity of the tank and the effects on adjacent neighbours and park, safety and security, general visual concerns, and ground conditions.

In response to consultation feedback the project team analysed and assessed eight possible new sites.

• Summary of options assessment [PDF, 2.4 MB]
• Options assessments (detailed report) [PDF, 1.9 MB]
• Options multi criteria analysis [PDF, 419 KB]
• Option 1 draft concept design [PDF, 2.7 MB]

The location of the eight options considered (amended Option 1)

The following criteria were used to select a compact, secure site, and a tank designed to future proof water supply.

• Technical  - hydraulic performance, design construction, site features
• Environmental -site contamination, impact on waterways
• Social  - community and visual impact, CPTED  (Crime Prevention through Environmental Design) principles
• Financial -  capital and operational cost

Given a high weighting in the assessment

The ranking for the options was (highest to lowest) - Option 2, 7, 5, 6, 1, 8, 3, 4

• 

  Concept drawings showing location of Option 2, and amended Option 1 reducing height to 4 metres

  A consolidated overall design includes the new tank next to the existing, re-clad pump station
• The site - specific architectural design for the tank and pump station includes a pergola
• Visual effects are reduced as the height of the tank will be four metres above ground and half a metre below ground
• Minimal park space is used for the tank, as the integrated design of pump station and the tank is more compact, and there are more opportunities for landscaping
• The location has less overall impact on neighboring properties and is visually less dominant in the park. Proposed trees will give scale and soften the tank façade along with appropriate landscape planting
• For safety and security, the existing barbed wire will be replaced with a pool - style black steel railing fence to also enclose the rear of the pump station
• Ground conditions by the stream will be managed through engineering design and construction
• Asphalt surfaces in the park will be reduced to match a reduction in vehicle circulation areas
• New pedestrian circulation paths will  link in with the existing path network
• There will be savings in energy use and pump upgrades because the pump station and suction tank are in close proximity.

Option 2 draft concept design [PDF, 7.2 MB]

The Fendalton-Waimairi-Harewood Community Board needs to make a decision about the new tank location and design (the preferred option is Option 2). Following consultation, the project team will get back to submitters with a consultation summary, the staff recommendation and the meeting date and time.

Once a plan is finalised work will be done in two stages: Stage 1—Detailed Design Stage 2—Construction.

Construction work (estimated to take eight months) will be during usual working hours but there will be some inconvenience to residents and park users. Every effort will be made to minimise noise and disruption.

Adjacent residents will be able to provide input to the colour of the tank and building. Timeframes are indicative only.

View across park from Jeffreys Road to existing pump station and tank