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5-Waters Volume 2 - Water Supplies <<
Te Pirita Water Supply
27 Upper Selwyn Huts Water Supply
27.1 Scheme Summary
| Estimated Population Served | 80
(Only 12 dwellings permanently occupied, the balance are occupied periodically)
|
Scheme Coverage (1 Jan 2021)
| Full Charges | 1 charge
97 connections
|
| Half Charges | 0
|
| >1 Charges | 0
|
System Components
| Bores/Intakes (No.) | 1 |
Treatment/Disinfection
| 1
|
| Reservoirs (No.) | 2 |
| Pump Stations (No.) | 1
|
| Piped (m) | 1,230
|
| History | Original scheme installation date | Unknown |
Value ($)
|
Replacement Cost |
$166,452 |
|
Depreciated Replacement Cost |
$96,427
|
|
Financial | Operator cost (scheduled and reactive maintenance) per connection
|
$237.40/connection |
Demand (m3)
(1 Jan – 31 Dec 2020)
| Average daily | 28.9
|
| Peak daily | 61.1
|
| Minimum daily | 0.6
|
| Average daily per connection | 0.3
|
| Type of Supply | | Unrestricted |
Target Pressure & Flow at boundary
| Pressure |
|
| Flow | |
| Sustainability | Well Security | Unsecure |
27.2 Key Issues
The following key issues are associated with the Upper Selwyn Huts water supply. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 27‑1 Upper Selwyn Huts Scheme Issues
| There is great deal of uncertainty surrounding the reticulation location, size and condition. As a result the data confidence for the Upper Selwyn Huts Water Supply is low. | The Upper Selwyn Huts Committee will provide Council with the reticulation location for GIS mapping. Council plans to undertake a progressive pipe location and sampling programme. The results will be incorporated into the AMS, Valuation and Activity Plan.
|
Financing
| Upper Selwyn Huts residents do not contribute to the District-wide water rating system. They instead pay for via a lease-hold agreement to Selwyn District Council. This relationship limits the availability of funding to invest in larger scale upgrades, investigations, pipe renewals, backflow prevention and water metering projects.
|
Chlorination
| Continuous low-dose chlorination is currently being planned for the scheme
|
Backflow
| There are no high risk industrial sites in Upper Selwyn Huts however the domestic backflow protection is limited with a number of the households without manifolds.
|
| Water metering
| Upper Selwyn Huts is not metered. Water usage data is not obtained.
|
Firefighting
| This scheme does not comply with New Zealand Fire Service Firefighting Water Supplies Code of Practice (SNZ PAS 4509:2008) due to a lack of capacity and pressure.
|
Climate change
| Upper Selwyn Huts sits alongside the Selwyn River at the mouth of Lake Ellesmere. The scheme is vulnerable to flooding and climate change related sea level changes. The extent of this risk, and the likely timeframe for climatic changes is unknown. This causes challenges when preparing long term plans and strategies for the water network.
|
Renewals
| Upper Selwyn Huts network is not managed under the district-wide renewals program. Some infrastructure is older than its design life but Selwyn District Council have no plans to renew the infrastructure due to the unique financial constraints.
|
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.
|
27.3 Overview & History
The community was formally established in 1895 when the land was permanently set aside as a reserve. The initial water system was installed by the community in 1929. The Springston South Reserve Management Committee operated and maintained the water supply (using Allied Water Systems and Nairn Electrical), directly funded by the community, until the Committee was discharged by Selwyn District Council in June 2011.
The supply has been upgraded over the years. Reducing artesian pressure necessitated installation of a small pump at the well head to fill the suction tank from which water is pumped to the elevated header tank.
A total of 97 dwellings exist within the reserve area and are considered to have access to water and wastewater services
Following the September 2010 earthquake structural damage occurred to the reinforced concrete tank stand. This was repaired through installation of a steel external frame.
Figure 27‑2 Scheme Schematic
27.4 System Capacity
This water supply serves 97 dwellings on Reserve land, only 12 of which may be permanently occupied and the balance occupied no more than 9 months in the year. All connections have been allocated and are utilised. No additional connections are anticipated. Existing capacity is adequate.
Table 27‑2 Capacity Summary
| Abstraction Capacity | - | - | - | 1 x bore pump |
| Consented Take | No limit | 90 ** | 9,000 * | |
| Peak Demand | - | -
| - | No SCADA |
* inferred value, ** estimated, based on 7 day average of 60 m3/day
27.5 Resource Consents
The Upper Selwyn Huts water supply has a number of resource consents. Table 27‑3 shows the water take permitted by the resource consents for this scheme.
Table 27‑3 Resource Consents
CRC146688
| to take and use groundwater. | Days Road And Spackman Avenue, SPRINGSTON | 19-Mar-02 | 31-Jan-35 | 60
(420 per week) |
27.6 Water Quality
The Upper Selwyn Huts water supply is a non-secure supply, which is sampled weekly in the treatment plant and monthly in the reticulation zone.
The following details E. coli transgressions for the period 2012 to 2020.
Treatment
There have been three E. coli source transgressions during this period. These occurred in October 2016, March 2017 and April 2017.
Zone
There have been two E. coli treatment transgressions during this period which occurred in March 2015 and April 2017.
Chemical Analysis
The following is a summary of the raw water chemical analysis carried out at the Upper Selwyn Huts water supply.
Table 27‑4 Upper Selwyn Huts Water Supply Raw Water Chemical Analysis Summary
| Total Lead (g/m3) | 0.01 (Maximum Acceptable Value)
| <0.00011 | < 0.00011 | 0.00011
| 0.00011
| <0.00011
| ✓
|
| pH (pH units) | 7-8.5 (Guideline Value)
| 8 | 7.9
| -
| 7.9
| 8.0
| ✓
|
| Total Hardness (g/m3 as CaCO3) | <200 (Guideline Value)
| 66 | 64.2
| 62.9
| 64.1
| 61.6
| ✓
|
| Total Calcium (g/m3) | n/v | 20 | 19.10
| 19.17
| 19.54
| 18.81
| ✓
|
| Total Iron (g/m3) | <0.2 (Guideline Value)
| <0.021 | < 0.021 | 0.021
| 0.021
| <0.021
| ✓
|
| Total Sodium (g/m3) | <200 (Guideline Value)
| 13.4 | 13.61 | 12.75
| 12.19
| 12.00
| ✓ |
Nitrate - Nitrogen (g/m3)
| 11.3 (Maximum Acceptable Value)
| 0.25
| 0.230
| 0.234
| 0.227
| 0.232
| ✓
|
27.7 Scheme Assets
A summary of material and diameter for pipes is not available for this scheme.
Figure 27‑3 Pipe Material – Upper Selwyn Huts
Figure 27‑4 Pipe Diameter – Upper Selwyn Huts
27.8 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.
27.9 Photos of Main Assets
Photo 1: Well and pump shed
|
27.10 Risk Assessment
A risk assessment has been undertaken for the Upper Selwyn Huts 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 26‑8 details the risk priority, Table 27‑6 outlines the risks and the list of key projects is found in Table 27‑9.
Table 27‑5 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 27‑6 Risks – Upper Selwyn Huts
| Electrical failure due to lightning or network spikes | Install surge diverters | 2014 | 6 | 6 | 6 |
| 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-consented activities | Renewal of consents | 2014 | 27 | 27 | 6 |
| Inadequate As-builts | as-builts | 2017 | | 9 | 0.7 |
The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.
27.11 Asset Valuation Details
The total replacement value of assets within the Upper Selwyn Huts water scheme is detailed in Table 27‑7 below.
Table 27‑7 Replacement Value, Upper Selwyn Huts
|
Plant and Equipment | $85,303
|
|
Water Reticulation | $81,149
|
27.12 Renewals
The renewal profile has been taken from the 2019 5 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 27‑3 below. There is a backlog of assets due for renewal now. Another peak occurs in 2038 and 2050.
Figure 27‑5 Upper Selwyn Huts Water Renewal Profile
27.13 Critical Assets
The criticality model for Upper Selwyn Huts has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 27‑8 shows the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 27‑8 Length of Assets per Criticality Level
5
| Low
| 1,263
|
4
| Medium-Low
| -
|
3
| Medium
| -
|
2
| Medium-High
| -
|
1
| High
| -
|
27.14 Asset Condition
There is no condition information available for this scheme.
27.15 Funding Program
The 10 year budgets for Upper Selwyn Huts are shown by Table 27‑8. Budgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in Volume 1.
All figures are ($) not adjusted for CPI “inflation". They are calculated on historical data, and population growth where relevant.
Table 27‑8 Upper Selwyn Huts Budget Summary
| 2021/2022 | $4,000
| -
|
| 2022/2023 | $35,000
| -
|
| 2023/2024 | -
| -
|
| 2024/2025 | -
| -
|
| 2025/2026 | -
| -
|
| 2026/2027 | -
| -
|
2027/2028
| -
| -
|
2028/2029
| -
| -
|
2029/2030
| -
| -
|
2030/2031
| -
| -
|
|
Total |
$39,000
| -
|
An explanation of the categories within the budgets are as follows below:
-
Expenditure consists of operation and maintenance costs;
-
Renewals are replacement of assets which are nearing or exceeded their useful life;
-
Projects are investigations, decisions and planning activities which exclude capital works; and
-
Capital projects are activities involving physical works.
There are several investigation projects planned for the Upper Selwyn Huts water scheme in the LTP budget.
Table 27‑9 Key Projects
Projects
| 4069023 | Asbuilt | -
| $10,000
| -
| -
| 100% LoS
|
Projects
| TBC
| CCTV survey
| -
| $15,000
| -
| -
| 100% LoS
|
Projects
| TBC
| Investigate options to achieve borehead security
| $2,000
| -
| -
| -
| 100% LoS
|
Projects
| TBC
| Fire risk management options and procedures
| $2,000
| -
| -
| -
| 100% LoS
|
Projects
| TBC
| Scheme continuity plan
| -
| $10,000
| -
| -
| 100% LoS
|
* Where LoS refers to Level of Service and G refers to Growth
The list of district wide projects can be found in 5Waters Activity Management Plan: Volume 1.
Discussion on Projects
Projects have been determined based on their:
- Relevance to the scheme
- Requirement to be completed under legislation
- Ability to bring the scheme up to or maintain the Level of Service required under council's Asset Management Policy.
Many projects are
jointly funded by more than one scheme and activity. Each scheme pays a pro-rata share only, equivalent to the number of connections.
Discussion on Capital and Projects
Where relevant, Capital (Levels of Service) and Capital (Growth) projects have been included in the scheme financial details.
Levels of Service Projects and growth splits have been provided to ensure the costs of population driven works are clear.
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Te Pirita Water Supply
