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5-Waters Volume 2 - Water Supplies
2 Arthurs Pass Water Supply
2.1 Scheme Summary
Estimated Population Served
| 357
|
Scheme Coverage (1 Jan 2021)
| Full Charges | 120 |
Half Charges | 0 |
>1 Charges | 3 |
System Components
| Bores/Intakes (No.) | 1 x surface water intake |
Treatment/Disinfection | 1 x water treatment plant with filtration, UV and chlorination |
Reservoirs (No.) | 4 x 30m3 |
Pump Stations (No.) | 1 |
Piped (m) | 4,705 |
History | Original scheme installation date | 1923 |
Value ($)
| Replacement Cost | $872,883
|
Depreciated Replacement Cost | $370,365
|
Financial
Demand (m3) (1 Jan – 31 Dec 2020)
| Operator cost (scheduled and reactive maintenance) per connection | $559.56/connection |
Average daily (m3/day) | 67 |
Peak daily (m3/day) | 129 |
Minimum daily (m3/day) | 11 |
Average daily per connection (m3/day) | 0.5 |
Type of Supply | | High pressure and unrestricted |
Target Pressure & Flow at boundary
| Pressure | |
Flow | >15 L/min |
Sustainability | Well Security | Unsecure |
2.2 Key Issues
The following key issues are associated with the Arthurs Pass water supply. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 2‑1 Arthurs Pass Scheme Issues
High cost to carry out maintenance and operation due to isolated location and distance from the maintenance contractors base. The rating base is small and there are also limited skills available in Arthurs Pass. | Council will investigate the potential for increased remote monitoring. Council also plan to investigate optimisation of maintenance and renewals to ensure costs stay at the minimum. |
The Arthurs Pass reticulation requires upgrading to comply with NZ Fire Fighting Code of Practise. For compliance this scheme would need to upgrade a number of existing water mains to 150 and 100 mm diameter and include headwork's storage.
| Investigate and cost works required, including upsizing mains and sufficient storage, to ensure sufficient fire fighting flows and volumes in accordance with the NZFFCoP This work will occur as part of the water supply treatment upgrade.. |
The Arthurs Pass water treatment plant requires upgrading to comply with the DWNZ. | The upgrade will address turbidity and protozoa compliance issues. It is important to deliver high quality water to Arthurs Pass as it is a popular tourist destination and risks will be managed through the Water Safety Plans. Upgrade budgeted 2017/18. |
2.3 Overview & History
The original scheme was installed in 1923 by the New Zealand Railways to serve a number of railway houses. The maintenance and administration of the scheme was taken over in 1975 by the then Malvern County Council. The scheme reticulation was extended during the 1980's and an upgrade of the intake and installation of a treatment plant occurred during 1999.
The water supply intake is located in a modified pool on Avalanche Creek, sourced from an unprotected alpine catchment above the village. Water is treated (UV and filtration) but doesn't comply with DWSNZ. Fire fighting capacity is available but when operational will cause contamination of the supply. In effect bypass of the treatment system is required to allow for fire fighting flows.
There are few permanent residents in the village, with most properties occupied periodically during weekends and holidays. Several businesses serve tourists and travellers passing through the village and provide tourist accommodation and services.
The remote location and harsh alpine environment present challenges for operation and maintenance of a water supply. The village can be isolated following heavy snowfall and storm events that periodically close State Highway 73.
The community is located within the alpine fault line, and is expected to incur significant damage to its water infrastructure resulting from a 76MMI event.
Council's Supervisory Control and Data Acquisition (SCADA) system monitors the UV and cartridge filtration systems, UPS, turbidity meter, temperature gauges and flowmeter recording among other things, daily water usage, differential pressure across the filters, UV system intensity, and air and water temperatures. Alarms include low UV intensity, high turbidity, low battery, low water temperature and communications failure. The telemetry system has battery backup.
In 2020, the Arthur’s Pass Water Supply Scheme was upgraded with the addition of automatic flushing, freezing control, validated UV disinfection, chlorination, treated water storage and surface pumps.
Treatment is provided by:
- Prefilter (four in parallel) with 20 micron cartridges
- Cartridge filter (two in parallel) with 1 micron cartridge
- UV Steriliser
- Chlorination
Figure 2‑2 Scheme Schematic
2.4 System Capacity
There are approximately 143 sections within the Arthur's Pass Village settlement of which 14 have the potential to be further developed for residential purposes. These sections comprise of 3.3 hectares with a potential yield of 29 additional households. In addition, there are currently 18 vacant lots available in Arthur's Pass. There is significantly less developable land available within Arthur's Pass Village compared to other townships in the Malvern area. However, static projected population growth, the presence of a number of significant resource management issues and the geographic location of the settlement contained within a National Park preclude significant growth in the township.
The Arthur's Pass WTP is constrained by intake capacity.
Current demand (daily and annual volume) exceeds that permitted by resource consent.
Table 2‑2 Capacity Summary
Max Intake Operating Flow
| 11
| -
| -
| Stream intake, no pumping
|
Treatment Capacity
| 21.87
| 622
| -
| UV Capacity (Max flow at 90% UVT)
|
Consented Take
| 11
| 200
| 30,000*
| -
|
Max Pump to Network Operating Flow
| 16.5
| -
| -
| -
|
Peak Demand
| 8.3
| 260** 198***
| 43,000****
| -
|
* inferred value, ** 21 Jan 2015, *** 29 Jan 2015, **** 2014
2.5 Resource Consents
The Arthurs Pass water supply has a number of resource consents. Table 2‑3 shows the water take permitted by the resource consents for this scheme.
Table 2‑3 Resource Consents
CRC991057
| To take surface water, at or about map reference NZMS 260 K33:925-064, for community water supply. | Arthurs Pass Township, ARTHURS PASS | 12-Aug-99 | 9-Feb-34 | 11 | 200 |
2.6 Water Quality
The Arthurs Pass water supply is a non-secure source and is currently sampled weekly for the source, treatment plant and monthly for the reticulation.
The following details E. coli transgressions for the sample periods 2012 to 2020.
Source
E. coli is regularly identified in samples of the Arthur's Pass source water, highlighting the importance of treatment for this scheme. There have been 132 incidences of E. coli in source waters since 2012.
Figure 2‑3 E.coli Transgressions - Source
Treatment
There have been six E. coli treatment transgressions during this period.
Figure 2‑4 E. coli Transgressions – Treatment
Zone
There have been twelve E. coli transgressions during this period.
Figure 2‑5 E. coli Trangressions - Zone
Chemical Analysis
The following is a summary of the raw water chemical analysis carried out at the Arthur's Pass Water Supply.
Table 2‑4 Arthur's Pass Water Supply Raw Water Chemical Analysis Summary
Total Lead (g/m3) | 0.01 (Maximum Acceptable Value)
| 0.00015
| <0.00011
| <0.00011
| <0.00011
| 0.000267 | 0.000966
| 0.000793
| ✓
|
pH (pH units) | 7-8.5 (Guideline Value)
| 7.1
| 7.6
| 7.3
| 7.8
| 7.4 | 7.7
| 7.9
| ✓
|
Total Hardness (g/m3 as CaCO3) | <200 (Guideline Value)
| <38
| 47
| 28
| 44
| 23.8
| 42.6
| 45.2
| ✓
|
Total Calcium (g/m3) | n/v | 14
| 17.7
| 10.4
| 16.5
| 8.88
| 15.98
| 16.92
| ✓ |
Total Iron (g/m3) | <0.2 (Guideline Value)
| <0.02
| <0.021
| <0.021
| <0.021 | < 0.021 | <0.021
| <0.021
| ✓
|
Total Sodium (g/m3) | <200 (Guideline Value)
| 1.8
| 2
| 1.39
| 2.1 | 1.27 | 1.94
| 2.01
| ✓
|
Nitrate - Nitrogen (g/m3) | 11.3 (Maximum Acceptable Value)
| 0.0093
| <0.05
| <0.05
| <0.05 | < 0.05 | <0.05
| <0.05
| ✓
|
2.7 Scheme Assets
A summary of material and diameter for pipes in Arthurs Pass is shown below by Figure 2‑6 and Figure 2‑7.
Figure 2‑6 Pipe Material – Arthurs Pass
Figure 2‑7 Pipe Diameter – Arthurs Pass
2.8 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.
2.9 Photos of Main Assets
Photo 1: Catchment
| Photo 2: Intake
|
Photo 3: Treatment Shed
|
|
2.10 Risk Assessment
A risk assessment has been undertaken for the Arthurs Pass 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 2‑5 outlines the risk priority rating and Table 2‑6 outlines the risks.
Table 2‑5 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 2‑6 Risks – Arthurs Pass
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 |
Frost issues | Review frost / freeze protection | 2014 | 27 | 6 | 6 |
Treatment is inadequate | Review treatment and upgrade as required | 2014 | 4 | 4 | 4 |
Water outages or treatment bypass when maintenance is carried out | Install reservoirs storage that could provide up to 8 hours storage to carry out maintenance without shutting off the water system. Place the reservoirs above shed or install booster pumps and you can put the reservoirs anywhere. | 2014
| 27
| 27
| 27 |
The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.
2.11 Asset Valuation Details
The total replacement value of assets within the Arthurs Pass water scheme is $872,883 with further details in Table 2‑7 below.
Table 2‑7 Replacement Value, Arthurs Pass
Plant and Equipment | $316,621
|
Water Reticulation
| Fire | $352
|
Hydrant | $32,966
|
Lateral | $27,146
|
Pipe | $373,540
|
Supply Point | $88,310
|
Valve | $33,948
|
2.12 Renewals
The renewal profile has been taken from the 2019 5 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 2‑8 below. The majority of renewals occur are due now, with smaller peaks in 2024 and 2033/34.
Figure 2‑8 Arthurs Pass Water Renewal Profile
2.13 Critical Assets
The criticality model for Arthurs Pass has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 2‑8 and Figure 2‑9 below shows the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 2‑8 Length of Assets per Criticality Level
5
| Low | 1,304
|
4
| Medium-Low | 2,033
|
3
| Medium | 555
|
2
| Medium-High | 696
|
1
| High | 0 |
2.14 Asset Condition
The asset condition model was run for Arthurs Pass in 2021. The methodology of the model can be found in 5Waters Activity Management Plan: Volume 1 which provides details of how the model has been calculated for the pipe reticulation assets. Figure 2‑10 below shows the level of asset condition for these assets within this scheme that have a recorded known condition.
Table 2‑9 provides a description of the condition rating used within the condition model.
Table 2‑9 Asset Condition Grading
1.0 | Excellent |
2.0 | Good |
3.0 | Moderate |
4.0 | Poor |
5.0+ | Fail |
The number of pipe faults is also measured through the asset management system. Figure 2‑11 shows the known historic pipe failures within this scheme.
2.15 Funding Program
The 10 year budgets are shown by Table 2‑10. Budgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in Volume 1. These can be found by following the links:
Renewal Strategy
Expenditure
All figures are ($) not adjusted for CPI “inflation". They are calculated on historical data, and population growth where relevant.
Table 2‑10 Budget Summary
2021/2022 | $11,000
| -
|
2022/2023
| -
| $120,000
|
2023/2024 | -
| -
|
2024/2025 | -
| $300,000
|
2025/2026 | -
| -
|
2026/2027 | -
| -
|
2027/2028 | -
| - |
2028/2029
| -
| -
|
2029/2030
| -
| -
|
2031/2032
| -
| -
|
Total | $11,000
| $420,000
|
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.
Table 2‑11 Key Projects
Capital Projects
| TBC
| Additional pressure sensors
| -
| $90,000
| -
| -
| 100% LoS
|
Capital Projects
| TBC
| 80/150mm raw water pipe freezing - SCADA scour automation
| -
| $30,000
| -
| -
| 100% LoS
|
Capital Projects
| TBC
| Second stage of Arthur's Pass School Terrace WTP upgrade
| -
| -
| -
| $300,000
| 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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5-Waters Volume 2 - Water Supplies