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5.2 Key Issues
The following key issues are associated with the Dalethorpe water supply. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 5‑1 Dalethorpe Scheme Issues
Achieving compliance with the Health Act and amendments will require additional treatment at the intake, including chlorination.
| Council will confirm the requirements for the Rural Agricultural Water Supplies from 2016.
|
Over allocation in selected areas has had a significant effect on levels of service. Modelling has confirmed under supply in some sections of the reticulation. Future renewals and replacements must be carried out in a manner that ensures levels of service are not affected. | Council will implement capital works plan to provide water treatment upgrades to meet the DWSNZ, |
The condition assessment and renewal programme for pipe main replacement to ensure sufficient funding is available when replacement is required. | Ongoing inspections and sampling of pipes at time of repair. |
Council require easements/agreements to ensure access to reticulation mains.
| Council will identify critical assets requiring easements/agreements and acquire these at time of upgrade works.
|
Backflow: all of the domestic connections only have air gaps, so the scheme is potentially vulnerable to for potential backflow issues.
| There is currently a district wide backflow prevention project underway.
|
5.3 Overview & History
Malvern Hills Rural Water Scheme (MHRWS) was installed from 1974 to 1978 for stock and domestic use for the area from Russell's Flat to the Selwyn River, but was extended to serve the townships of Whitecliffs, Glentunnel and Coalgate. The scheme was designed as a restricted supply with flow rates of about 90L/ha/day including domestic use. Water is provided at low pressure and flow to the customer's storage tanks.
The MHRWS included two separate supply, treatment and distribution networks which are now known separately as Dalethorpe Water Supply and Hartleys Water Supply. The Dalethorpe Water Supply is the northern part of the MHRWS and covers approximately 8,223ha of rural land. The intake is located adjacent to the Hawkins River near Dalethorpe Road.
Chlorine was originally used as the primary form of water treatment for the Dalethorpe scheme. In 1986 a decision was made to remove chlorination. This occurred in 1987 with the addition of UV treatment. Chlorine was used as required mainly during times of high turbidity.
In 2016 a UV treatment upgrade occurred at the Dalethorpe scheme. At this time Gas chlorination was introduced replacing the temperamental liquid chlorination system.
Figure 5‑2 Scheme Schematic
5.4 System Capacity
The Dalethorpe Water Supply provides water to a large rural area. This is used for stock and other on-farm purposes, as well as for residential drinking water. There are no towns connected to this water supply. Water is supplied to a tank at each point of supply via a flow restrictor that limits the daily volume to an agreed allocation (2000L/day per dwelling plus 65 L/day/ha). Peak day demand is approaching current abstraction capacity. Further investigation and analysis would be required to confirm the adequacy of source and distribution capacity if the scheme area were to be expanded.
Table 5‑2 Capacity Summary
Abstraction Capacity | 6.9
| 596
| -
| 2 x pumps (duty/standby) |
Consented Take
| 7.2 | 624 | 140,000 * | CRC173785
|
Filter Capacity
| 27.99
| -
| -
| -
|
UV Capacity
| 21.87
| -
| -
| Max flow at 90% UVT
|
Peak Demand | 7.2 ** | 620 | 148,640 *** | -
|
* inferred value, ** Pump flow, *** 2014
Note, the consent allows water to be shared as part of a water users group. Refer CRC173786 & CRC173785
5.5 Resource Consents
The Dalethorpe water supply has one resource consent. Table 5‑3 shows the water take permitted by the resource consent for this scheme.
Table 5‑3 Resource Consents
CRC173785
| To take and use water
| Dalethorpe Road, SHEFFIELD
| Lodged 31-Oct-00 | 4-May-36 | 7.2 | 624 |
5.6 Water Quality
The water source for Dalethorpe Water Supply is non-secure. The source, treatment plant and reticulation zone are sampled twice weekly.
The following details E. coli transgressions for the period 2012 to 2020.
Source
There have been 234 incidences of E. coli identified in source water during this period for Dalethorpe, highlighting the importance of water treatment.
Figure 5‑3 E. coli Transgressions – Source
Treatment
There have been six E. coli treatment transgressions during this period for Dalethorpe.
Figure 5‑4 E.coli Transgressions – Treatment Dalethorpe
Zone
There have been four transgressions during this period for Dalethorpe, two in November 2012 and two in Jan 2013.
Chemical Analysis
The following is a summary of the raw water chemical analysis carried out at the Dalethorpe Water Supply.
Table 5‑4 Dalethorpe Water Supply Raw Water Chemical Summary
Total Lead (g/m3) | 0.01 (Maximum Acceptable Value)
| <0.0001
| 0.0002
| 0.00034
| 0.00014
| 0.000266
| 0.000119
| 0.00022
| 0.000255
| ✓ |
pH (pH units) | 7-8.5 (Guideline Value)
| 7.1
| 7
| 6.9
| 7.4
| 7.3 | 6.9
| 7.1
| 7.5
| ✓ |
Total Hardness (g/m3 as CaCO3) | <200 (Guideline Value)
| 33
| 38
| 41
| 43
| 40.2 | 31.3
| 36.5
| 41.8
| ✓ |
Total Calcium (g/m3) | n/v | 8.7
| 10.1
| 11
| 11.4
| 10.7
| 8.32
| 9.66
| 11.09
| ✓ |
Total Iron (g/m3) | <0.2 (Guideline Value)
| <0.02
| <0.021
| <0.021
| 0.029
| < 0.021
| <0.021
| <0.021
| <0.021
| ✓ |
Total Sodium (g/m3) | <200 (Guideline Value)
| 5
| 5.9
| 6.1
| 7.4
| 5.98
| 5.11
| 6.09
| 6.71
| ✓ |
Nitrate - Nitrogen (g/m3) | 11.3 (Maximum Acceptable Value)
| 2.1
| 0.25
| 0.4
| 0.27
| 0.318 | 0.595
| 0.418
| 0.203
| ✓
|
5.7 Scheme Assets
A summary of material and diameter for pipes in Dalethorpe is shown by Figure 5‑5 and Figure 5‑6.
Figure 5‑5 Pipe Material – Dalethorpe
Figure 5‑6 Pipe Diameter – Dalethorpe
5.8 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.
5.9 Photos of Main Assets
5.10 Risk Assessment
A risk assessment has been undertaken for the Dalethorpe 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 5‑5 outlines the risk priority rating, Table 5‑6 outlines the risks and the list of key projects is found in Table 5‑11. The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.
Table 5‑5 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 5‑6 Risks – Dalethorpe
Cl2 does not have adequate contact time | Reconfigure tanks at Dalethorpe to allow effective chlorination | 2014 | 27 | 27 | 12 |
Contamination within reticulation | Investigate Chlorination | 2014 | 12 | 2.1 | 2.1 |
Lack of SCADA results in undetected failures | Put SCADA at the other reservoir (Springfield Road) or/and Bluff Road shed | 2014 | 6 | 2.1 | 2.1 |
Contamination | Backflow preventer needed well head to be brought above ground | 2014 | 12 | 12 | 12 |
Electrical failure due to lightning or network spikes | Install surge diverters | 2014 | 6 | 2.1 | 2.1 |
Non-consented activities | Renewal of consents | 2014 | 27 | 27 | 6 |
Inadequate treatment under all conditions | Install filtration
| 2017 | | 20 | 3.5 |
Scheme impacted by poor water quality | auto flush
| 2017 | | 45 | 20 |
Inadequate capacity into the future | Dalthorpe Wyndale Road cnr to Springfield Road PS | 2017 | | 12 | 2 |
5.11 Asset Valuation Details
The total replacement value of assets within the Dalethorpe water scheme is $4,711,133 with further details in Table 5‑7 below.
Table 5‑7 Replacement Value, Dalethorpe
Plant and Equipment | $656,563
|
Water Reticulation | Fire
| $42,476
|
|
Hydrant | $4,620
|
Lateral
| $27,137
|
Pipe | $3,867,299
|
Supply Point | $68,192
|
Valve | $44,846
|
5.12 Renewals
The renewal profile has been taken from the 2019 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 5‑7 below. The majority of renewals occur in the first ten years.
Figure 5‑7 Dalethorpe Water Renewal Profile
5.13 Critical Assets
The criticality model for Dalethorpe has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 5‑8 and Figure 5‑8 below shows the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 5‑8 Length of Assets per Criticality Level
5
| Low
| 50,714 |
4
| Medium-Low | 6,047 |
3
| Medium | 868 |
2
| Medium-High | 3,600 |
1
| High
| 0
|
5.14 Asset Condition
The asset condition model was run for Dalethorpe in 2021. The methodology of the model can be found in 5Waters Activity Management Plan: Volume 1 which provides details of how the model has been calculated for the pipe reticulation assets. Figure 5‑9 below shows the level of asset condition for these assets within this scheme that have a recorded known condition. Table 5‑9 provides a description of the condition rating used within the condition model.
The number of pipe faults is also measured through the asset management system. Figure 5‑10 shows the known historic pipe failures within this scheme.
Table 5‑9 Asset Condition Grading
1.0 | Excellent |
2.0 | Good |
3.0 | Moderate |
4.0 | Poor |
5.0+ | Fail
|
5.15 Funding Program
The 10 year budgets are shown by Table 5‑10. Budgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in Volume 1.
All figures are ($) not adjusted for CPI “inflation". They are calculated on historical data, and population growth where relevant.
Table 5‑10 Budget Summary
2021/2022 | $5,000
| -
|
2022/2023
| $10,000
| $150,000
|
2023/2024 | -
| -
|
2024/2025 | -
| $100,000
|
2025/2026 | -
| -
|
2026/2027 | -
| $300,000
|
2027/2028 | -
| -
|
2028/2029
| -
| $400,000
|
2029/2030
| -
| -
|
2031/2032
| -
| -
|
Total | $15,000
| $950,000
|
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 5‑11 Key Projects
Capital Projects
| -
| Additional reservoir site
| -
| -
| -
| $300,000
| TBC
|
Capital Projects
| -
| Second Bluff Road reservoir
| -
| -
| -
| $200,000
| TBC
|
Capital Projects
| -
| Pumping main upsized
| -
| -
| -
| $100,000
| TBC
|
Capital Projects
| -
| Additional chlorine analysers
| -
| $150,000
| |
| 100% LoS
|
Capital Projects
| -
| Treatment upgrades
| -
| -
| -
| $200,000
| 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