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5-Waters Volume 2 - Water Supplies
25 Taumutu Water Supply
25.1 Scheme Summary
| Estimated Population Served | 30 |
Scheme Coverage (1 Jan 2021)
| Full Charges | Approx. 16 Connections
|
| Half Charges |
| >1 Charges |
System Components
| Bores/Intakes (No.) | 1 |
| Treatment/Disinfection | None, but a new WTP is planned and underway
|
| Reservoirs (No.) | None, however 60m3 of storage is planned and underway
|
| Pump Stations (No.) | 1
|
| Piped (m) | 850.4
|
| History | Original scheme installation date | 1960's |
Value ($)
| Replacement Cost | $131,279
|
| Depreciated Replacement Cost | $56,023
|
Financial
| Operator cost (scheduled and reactive maintenance) per connection
| $1,356.64/connection
|
Demand (m3)
(1 Jan – 31 Dec 2020)
| Average daily | 11.7
|
| Peak daily | 43.9
|
| Minimum daily | 0.1
|
| Average daily per connection | 0.69
|
| Type of Supply | | Medium pressure and unrestricted |
Target Pressure & Flow at boundary
| Pressure | >240kPa |
| Flow | >15L/min |
| Sustainability | Well Security | Unsecure |
25.2 Key Issues
The following key issues are associated with the Taumutu water supply. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 25‑1 Taumutu Scheme Issues
| There is great deal of uncertainty surrounding the reticulation location, size and condition. As a result the data confidence for the Taumutu Water Supply is low. | Council have undertaken a GPS survey of the reticulation and the results have been incorporated into the AMS and valuation data sets. |
The Taumutu community have previously requested Council to consider transferring the water supply into local ownership and management. With approximately 11 connections, this would be possible but is not a priority.
| The Local Government Act 2002 permits such a transfer (S131 and S135) where a scheme serves less than 200 persons. The following would be required for a Transfer: - A plan be developed on all aspects of scheme operation and maintenance and management
- The Medical Officer of Health prepare a report on any health issues and make this publicly available
- A binding referendum be held with > 50% in favour support.
The Water Safety Plan will address and confirm if the operational requirements are appropriate for transfer.
|
Fire-fighting: There is no firefighting capability in the system.
| With the proximity to Lake Ellesmere, water for firefighting would be drawn from the lake.
|
Water metering: There is only one single meter on the system which is at the pump station.
| Action plan?
|
Climate change
| Action plan?
|
Finance: This is a metered system with one bill payer – Ngai Tahu Property.
| Action plan?
|
Catchment management
| To encompass a holistic view of the drinking water supply improved liaison with ECan and study of ground water quality within the water supply protection zones are being investigated.
|
Backflow risk
| There is currently only backflow protection at the source pump station. There is a district-wide backflow prevention project underway.
|
Emergency chlorination
| To allow on-demand chlorination as a result of a treatment or storage transgression or contamination event, provision for emergency chlorination is currently being planned for the scheme as part of the WTP implementation.
|
25.3 Overview & History
The Taumutu Water Supply provides untreated groundwater to a small coastal community located at the south-western corner of Te Waihora/Lake Ellesmere, near the lake opening. The community is a Maori Reserve consisting of three land parcels all owned by Ngai Tahu Property Ltd (the Trust), which is the sole ratepayer for the community.
The residents of Fisherman’s Point implemented the water supply via a small artesian bore in 1960. At the request of the residents Selwyn District Council (Council) began to operate the supply at Pohau Road in 1963. Council has never owned the water infrastructure, the location of which was not well understood, however this has recently been mapped by Council, with approximately 16 connection points which may be in use. It was agreed in principle that Council would maintain the supply for an agreed fee on behalf of the Fisherman’s Point residents under Section 386 of the Local Government Act.
In August 1988, Council investigated terminating responsibility for the supply as the maintenance fee was deemed inadequate for the upkeep of the supply. However, this would have been a breach of the Health Act 1956, therefore it was agreed that they would continue as status quo. The scheme currently operates for a fixed fee of 10.5 times the Council minimum water supply charge.
Water for the Taumutu water supply is obtained from a single artesian bore in the community. The source is considered to be secure groundwater but does not hold secure status due to the bore being too small for a complying assessment. A single surface pump delivers water to the reticulation.
In 2019 Council committed to installing water treatment at the scheme. The new water infrastructure to be provided includes:
- Selective abstraction and flush to waste
- Water treatment plant with UV treatment
- 60 m3 treated water storage tanks
- Surface pumps set (duty-standby)
- Full SCADA install
- Undergrounding and upgrade of the existing power line
- New larger pipeline between the treatment plant and the reticulation
- Option for future disinfection
The improvements are intended to provide the following benefits:
- Compliance with current DWSNZ and expected changes
- Sufficient space to allow easy retrofit for any future DWSNZ changes
- Improved redundancy in the system
- Better capacity to meet peak demand
- Improved water pressure in the reticulation
- Greater electrical capacity and improved reliability
Works to date at the site include a new pump, pressure cylinder, pressure switch and an additional air valve to prevent air blockages that the bore has been experiencing. Council have also purchased and are holding a spare pump for the site to improve reaction times.
Council are planning to undertake significant renewals of the underground reticulation for this scheme, within the 2021-2031 LTP timeframes.
Figure 25‑2 Scheme Schematic
25.4 System Capacity
This water supply was developed to serve this small coastal community. All connections have been allocated and are utilised. No additional connections are anticipated. Existing capacity is adequate.
Table 25‑2 Capacity Summary
| Abstraction Capacity | 1
| -
| -
| 1 x bore pump |
| Consented Take | 1 | 76 | 11,400 | -
|
Peak Demand
| -
| 77 | 14,400
| Recent demand has returned within consent limits |
25.5 Resource Consents
The Taumutu water supply has one resource consents (Table 25‑3).
Table 25‑3 Resource Consents
CRC010894.1
| To take and use groundwater. | Fishermans Point, TAUMUTU | 12-Feb-10 | 31-Jan-35 | 1 | 76 |
25.6 Water Quality
The Taumutu water supply is currently sampled weekly at the source and monthly in the reticulation zone.
The following details E. coli transgressions for the period 2012 to 2020.
Source
There have been no E. coli source transgressions during this period.
Zone
There have been no E. coli treatment transgressions during this period.
Chemical Analysis
The following is a summary of the raw water chemical analysis carried out at the Taumutu Water Supply.
Table 25‑4 Taumutu Water Supply Raw Water Chemical Analysis
| Total Lead (g/m3) | 0.01 (Maximum Acceptable Value)
| <0.0001
| 0.00012
| <0.00011
| 0.00016 | 0.000112 | 0.000131
| <0.00011
| 0.000149
| ✓
|
pH (pH units)
| 7-8.5 (Guideline Value)
| 7.6
| 7.5
| 7.7
| 7.7 | 7.7 | 7.7
| 7.7
| 7.8
| ✓
|
| Total Hardness (g/m3 as CaCO3) | <200 (Guideline Value)
| 35
| 38
| 37
| 37
| 35.9 | 36.7
| 37.6
| 34.9
| ✓
|
| Total Calcium (g/m3) | n/v | 11
| 11.8
| 11.5
| 11.4
| 11.11 | 11.31
| 11.7
| 10.8
| ✓
|
| Total Iron (g/m3) | <0.2 (Guideline Value)
| <0.02
| <0.021
| <0.021
| <0.021 | < 0.021 | <0.021
| <0.021
| <0.021
| ✓
|
| Total Sodium (g/m3) | <200 (Guideline Value)
| 5.8
| 5.9
| 5.9
| 6.2
| 6.04
| 5.32
| 5.77
| 5.75
| ✓ |
| Nitrate - Nitrogen (g/m3) | 11.3 (Maximum Acceptable Value)
| 0.91
| 0.98
| 1.04
| 1.08
| 1.16
| 1.216
| 1.155
| 1.26
| ✓
|
25.7 Scheme Assets
A summary of material and diameter for pipes in Taumutu is shown below in Figure 25‑3 and Figure 25‑4.
Figure
25‑3 Pipe Material – Taumutu
Figure 25‑4 Pipe Diameter – Taumutu
25.8 Operational Management
The water supply is operated and maintained under two maintenance contracts as follows:
- Contract 1241: Water Services Contract. Contract is with SICON who undertakes investigations, conditions inspections, proactive and reactive maintenance and minor asset renewals; and
- Contract 1202: Parks and Reserves Contract. Contract is with SICON who undertakes the maintenance of land scape features related to water services e.g. mowing, gardens etc.
Water quality sampling is completed under an agreement with Food and Health Ltd as required.
25.9 Photos of Main Assets
Photo 1: Bore head
|  Photo 2: Taumutu bore head site layout
|
 Photo 3 & 4: Pumping shed and backflow arrangements
|
25.10 Risk Assessment
A risk assessment has been undertaken for the Taumutu scheme. The key output from the risk assessment is the identification of any extreme and high risks which need to be mitigated. In order to mitigate these risks they have been included and budgeted for in the projects within this LTP. Table 25‑5 details the risk priority, Table 25‑6 outlines the risks. Many of these risks have been addressed by the WTP upgrade, which is currently underway, and renewals planned within the 2021 - 2031 LTP timeframes.
Table 25‑5 Risk Priority Rating
| > 50 | Extreme | Awareness of the event to be reported to Council. Urgent action to eliminate / mitigate / manage the risk. Document risk and action in the AMP. |
| 35-50 | Very High | Risk to be eliminated / mitigated / managed through normal business planning processes with responsibility assigned. |
| 14-35 | High | Manage risk using routine procedures. |
| 3.5-14 | Moderate | Monitor the risk. |
| < 3.5 | Low | Awareness of the event to be reported to Council. Immediate action required to eliminate / mitigate / manage the risk. Document risk and action in the AMP. |
Table 25‑6 Risks – Taumutu
| Electrical failure due to lightning or network spikes | Install surge diverters | 2014 | 6 | 2.1 | 2.1 |
| Failure to meet NES water meter standards | NES Water Meter Compliance | 2014 | 20 | 6 | 6 |
| Inability to collect income from non-metered properties | Install property water meters | 2014 | 27 | 27 | 2.1 |
| Non-compliance with the DWSNZ | DWSNZ - Age Testing | 2014 | 6 | 0.7 | 0.7 |
| Non-compliance with the DWSNZ | DWSNZ - Bore-head security | 2014 | 6 | 6 | 6 |
| Non-consented activities | Renewal of consents | 2014 | 27 | 27 | 6 |
| Scheme efficiency | locate PRV and move to head works + res and surface pumps | 2017
|
| 4 | 0.7
|
The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.
25.11 Asset Valuation Details
The total replacement value of assets within the Taumutu water scheme is $131,279 with further details in Table 25‑7 below.
Table 25‑7 Replacement Value, Taumutu
|
Plant and Equipment | $81,390
|
Water Reticulation
| Lateral | $15,251
|
Pipe
| $33,521
|
Supply point
| $369
|
| Valve | $747
|
25.12 Renewals
The renewal profile has been taken from the 2019 5 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 25‑5 below.
Figure 25‑5 Taumutu Water Renewal Profile
25.13 Critical Assets
The criticality model for Taumutu has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 25‑8 and Figure 25‑6 below show the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 25‑8 Length of Assets per Criticality Level
5
| Low
| 928
|
4
| Medium-Low
| 0
|
3
| Medium
| 0 |
2
| Medium-High | 0 |
1
| High | 0 |
25.14 Asset Condition
The asset condition model was run for Taumutu in 2021. The methodology of the model can be found in 5Waters Activity Management Plan: Volume 1 which provides details of how the model has been calculated for the pipe reticulation assets. Figure 25‑7 below shows the level of asset condition for these assets within this scheme that have a recorded known condition.
Table 25‑9 provides a description of the condition rating used within the condition model.
Table 25‑9 Asset Condition Grading
| 1.0 | Excellent |
| 2.0 | Good |
| 3.0 | Moderate |
| 4.0 | Poor |
| 5.0+ | Fail |
The number of pipe faults is also measured through the asset management system. Figure 25‑8 shows the known historic pipe failures within this scheme.
25.15 Funding Program
There are no scheme-specific projects for Taumutu in the 10 year budget, although parts of the scheme will be renewed from the district-wide renewals budget. Expenditure and renewals have been reported on a district-wide basis in Volume 1.
An upgrade to the scheme (including a new WTP and reservoir storage) was budgeted for under previous LTPs and is currently underway.
The list of district wide projects can be found in 5Waters Activity Management Plan: Volume 1.
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5-Waters Volume 2 - Water Supplies
