A well head is the physical structure at the top of the well that connects to the water supply network.

The Council has 104 wells with below ground well heads and 36 wells with above ground well heads. All new well heads are built above ground to improve the resilience and safety of wells and the security of water supply.

In order for groundwater to be provided without the need for treatment such as chlorination, three criteria must be met:

  1. The bore water must not be directly affected by surface or climatic influences (i.e. the water is at least a year old, by which time any pathogens will have died)
  2. The well head must provide satisfactory protection to prevent contamination of the water supply
  3. E. coli must be absent in the bore water.

Below and above ground well heads

The Council is upgrading its well heads so they meet the interpretation of the standard required to meet criteria 2 above. Once well heads are secure, temporary chlorination can stop at that pump station.

All new well heads are built above ground.

There are 11 well heads at four pump stations that meet the standard required to be considered secure from contamination. Water at these sites is not chlorinated (Keyes, Estuary, Prestons and Gardiners).

Stage 1 work

We looked at what work we could get underway immediately and identified seven pump stations to focus on with the aim of removing the need to chlorinate water supplied from those pump stations.

The seven pump stations, planned work and time-frame for completion is outlined below. 

Pump station and supply zone Well heads Planned work Timeframe

Burnside

(North West)

1 below ground

5 above ground

Raise below ground well head, minor work to make above ground well heads secure.

Work due to start in August 2018

Expected completion November 2018

Farrington

(North West)

1 below ground

4 above ground

Raise below ground well head, minor work to make above ground well heads secure.

Work due to start in August 2018

Expected completion November 2018

Grampian

(North West)

1 below ground

1 above ground

Raise below ground well head, minor work to make above ground well head secure.

Work due to start August 2018

Expected completion November 2018

Hills

(Central)

1 below ground

2 above ground

Raise below ground well head, minor work to make above ground well heads secure.

Work due to start in August 2018

Expected completion November 2018

Grassmere

(Central)

3 below ground Drill one replacement well, raise two below ground well heads.

Work due to start in November 2018

Expected completion June 2019

Mays

(Central)

3 below ground Drill one replacement well, raise two below ground well heads.

Work due to start in December 2018

Expected completion July 2018

Kainga

(Brooklands/Kainga)

1 above ground Minor work to make above ground well head secure.

Work due to start in July 2018

Expected completion October 2018

Stage 2 work

We have confirmed our approach for upgrading another 49 wells at 17 pump stations.

We prioritised these pump stations after considering the security of the source water, the capacity of the pump station and the likelihood of being able to progress the works without undue delay. 

The pump stations and planned work at each are outlined below. Construction is proposed to begin in 2019.

Pump station and supply zone Well  heads Planned work

Brooklands

(Brookland/Kainga)

2 below ground Raise below ground well head for well 1, abandon well 2.

Addington

(Central)

2 below ground Raise below ground well heads.

Blighs

(Central)

1 below ground

1 above ground

Raise below ground well head, minor works to make above ground well head secure.

Hilmorton

(Central)

3 below ground Raise below ground well heads (may drill two new wells to replace Thorrington and Palatine)

Sydenham

(Central)

2 below ground

2 drilled

Raise below ground well heads, complete head works on drilled wells.

Trafalgar

(Central)

2 below ground

1 above ground

Raise below ground well heads, minor works to make above ground well head secure 

Worcester

(Central)

2 below Raise below ground well heads.

St Johns

(Central/Ferrymead)

2 below ground

1 above ground

Raise below ground well heads, minor works to make above ground well head secure.

Carters

(Central/Rawhiti)

4 below ground Raise below ground well heads

Lake Terrace

(Central/Rawhiti)

1 below ground

2 above ground

Raise below ground well head, minor works to make above ground well heads secure

Auburn

(North West)

2 below ground Raise below ground well head for well 5, abandon well 3.

Crosbie

(North West)

2 below ground

1 above ground

Raise below ground well heads, minor works to make above ground well head secure.

Burwood

(Parklands)

2 below ground Raise below ground well heads.

Picton

(Riccarton)

3 below ground Raise below ground well heads.

Making sure there's enough water while we upgrade well heads

Demand for water fluctuates depending on the season and at different times of the day. We need to provide enough for people’s basic needs, as well as for emergencies such as firefighting.

While we work on a well head to upgrade it, we can’t use water from it. We have to carefully consider where we do maintenance and upgrades so we can continue to provide enough water to all parts of the city. Our analysis has led to an initial programme of work that, when completed, will provide enough unchlorinated water to meet typical demand over winter. If demand goes above this level, we may need to use the other sites and that water will need to be treated.

Favouring supply from above ground well heads

Some pump stations are supplied by a mix of below ground and above ground well heads. We intend to upgrade the above ground well heads so they are secure. We will also isolate the below ground well head so no water is being taken from it. This means water from these pump stations will not be chlorinated, including while any further remediation is done on the below ground well head such as bringing it above ground or drilling a new well.

The pump stations where this is planned are:

  • Grampian
  • Farrington
  • Hills
  • Burnside
  • Lake Terrace
  • Thompsons
  • Woolston

Upgrading above ground well heads

We are undertaking minor works on 23 above ground well heads to bring them up to the required standard so they can be signed off as secure.

This includes installing air valves, putting mesh on air valves to prevent contaminants getting in, sealing around cable penetrations and a concrete plinth around one of the well heads.

Remediating below ground well heads

Options for the below ground well heads include:

  • Raising the well head above ground.
  • Stop using the well and decommissioning it.
  • Drilling new wells on site.
  • Exploring new sites for new wells.