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 the wells and the security of the 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.

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.

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Below- and above-ground well heads

Work timeframes

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 Timeframe

Burnside

Expected completion end of Jan 2019

Farrington

Expected completion end of Jan 2019

Grampian

Expected completion end of Jan 2019

Hills

Expected completion Jan 2019

Kainga

Expected completion end of Jan 2019

Denton

Expected completion Jul 2019

Dunbars

Expected completion Jul 2019

Lake Terrace

Expected completion Jul 2019

Trafalgar

Expected completion Jul 2019

Brooklands

Expected completion Jul 2019

Grassmere

Expected completion Sep 2019

Mays

Expected completion Sep 2019

Kainga

Expected completion end of Jan 2019

Auburn

Expected completion Sep 2019

St Johns

Expected completion Sep 2019

Hillmorton

Expected completion Sep 2019

Making sure there's enough water while we upgrade

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