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5-Waters-Volume-3-Wastewater
5 Doyleston Wastewater Scheme
5.1 Scheme Summary
| Estimated Population Served | 357
|
Scheme Coverage (1 Jan 2021)
| Full Charges
| 113
|
| Half Charges | 6
|
| >1 Charges | 4
|
System Components
| Piped (m) | 6,470
|
| Manholes (No.) | 34
|
| Pump Stations (No.) | 3
|
| Treatment | N/A (conveyed to Ellesmere STP) |
| Disposal | N/A (conveyed to Ellesmere STP) |
| History | Original scheme installation date | 1996 |
Value ($)
| Replacement Cost | $2,025,568
|
| Depreciated Replacement Cost | $1,541,295
|
Financial
| Operator cost (scheduled and reactive maintenance) per connection
| $380.87/connection
|
Demand
(1 Jan - 31 Dec 2020)
| Annually (m3)
| 91,578
|
| Average daily (m3) | 250.9
|
| Peak daily (m3) | 860
|
| Minimum daily (m3) | -
|
| Infiltration | Yes
|
| Sustainability | Ultimate discharge point | Conveyed to Ellesmere WWTP |
5.2 Key Issues
The following key issues are associated with the Doyleston Wastewater Scheme. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 5‑1 Doyleston Scheme Issues
| Potential for future infiltration issues as scheme ages | Monitor groundwater levels and daily flows. Investigate issues as required |
5.3 Overview & History
The reticulation was installed in the township in 1996 and replaced a variety of disposal systems i.e. septic tanks (with disposal to adjacent drains) and chemical toilets. High groundwater levels during winter made disposal via standard soak holes difficult and there was a significant amount of discharge to local waterways. The trunk mains are located at the back of properties.
The wastewater from properties is reticulated to a central pump station in Doyleston, and then pumped approximately 2.8 km to Leeston wastewater treatment plant.
Figure 5‑2 Scheme Schematic
Figure 5‑3 Doyleston Master Plan
Figure 5‑4 Pump Station Failure Map
5.4 System Capacity
The scheme is operating within operating limits. Refer to section 5.6.3 for design information. Pump and pressure main upgrades will be required to provide for additional capacity for growth.
Master Plan upgrades are provided in Figure 5‑3.
Figure 5‑5 Wet Weather Flow Capacity Map
5.5 Resource Consents
Doyleston township is part of the Ellesmere scheme. Therefore, all wastewater is pumped to the Ellesmere Treatment Plant located in Leeston. The resource consents required for this treatment plant are in the Ellesmere section of this plan.
5.6 Scheme Assets
A summary of the assets within this scheme is outlined in this section.
5.6.1 Reticulation Overview
A summary of material and diameter for pipes is shown in Figure 5‑6 and Figure 5‑7.
Figure 5‑6 Pipe Material – Doyleston
Figure 5‑7 Pipe Diameter – Doyleston
5.6.2 Treatment and Disposal
No treatment is carried out with all wastewater pumped to Leeston.
5.6.3 Design
The original design data for the Doyleston system is tabled below.
Table 5‑2 Design Data
The Doyleston, scheme is ultimately limited by the capacity of the Leeston WWTP, which in turn is bound by the resource consents for discharging from the works. This is also the case with Leeston and Southbridge Schemes. These schemes therefore need to be considered collectively in determining future capacity for growth in the three schemes.
Pump and pressure main upgrades will be required to provide for additional capacity for growth.
Master Plan upgrades are provided in Figure 5‑3.
5.6.4 Pump Stations
There are three pump stations within the Doyleston scheme, with the main pump station pumping to the Leeston WWTP. Details are tabled below.
Table 5‑3 Pump Station
| Doyleston (S) Main | 2000 Ø | 3.1 | 3 | 2 | Flygt FP3124 SH246 7.4 kW | 5 | 4 | 0.8 | 0.17 |
| Doyleston (S) Minor | 1200 Ø | 1.1 | 2.5 | 1 | Flygt CP3057 260 2.4 kW | N/A | 5 | 0.07 | 0.17 |
| Doyleston (S) Greenan Pl | 1400 Ø | 1.5 | 4 | 2 | Flygt CP3068 251 2.4 kW | N/A | 3 | 0.03 | 0.08 |
Table 5‑4 Pump Station Storage Time Analysis
| Doyleston (S) Main | Doyleston | 9:00 | 8:30 | 8.7 | 11.5 | 15.03 | 24214 |
| Doyleston (S) Minor | Doyleston | 9:00 | 8:30 | 27.6 | 32 | 19.29 | 3408 |
| Doyleston (S) Greenan Place | Doyleston | 9:00 | 8:30 | 25 | 28.5 | 15.308 | 80926 |
5.6.5 Rising Mains
Table 5‑5 Rising Main Overview
| Doyleston PS to Cunningham rising main | PVCU | PN12 | 100/80 | Assumed Pressure Rating |
| Doyleston (S) Greenan PS | MDPE | PN12.5 | 51 | |
| Doyleston (S) Minor PS | PVCU | PN12.5 | 53 | Assumed Pressure Rating |
5.7 Operational Management
The wastewater schemes are operated and maintained under the maintenance contract as follows:
- Contract 1241: Water Services Contract. Contract is with SICON who undertakes investigations, conditions inspections, proactive and reactive maintenance and minor asset renewals.
Wastewater sampling is completed under an agreement with Food and Health Ltd as required.
5.8 Photos of Main Assets
Photo 1 - Leeston Rd Pump Station
| 
Photo 2 - Doyleston Main Pump Station
|
5.9 Risk Assessment
A risk assessment has been undertaken for the Doyleston 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 5‑6 details the risk priority matrix and Table 5‑7 outlines the risks for this scheme.
Table 5‑6 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 5‑7 Risks - Doyleston
| Failure of low class pipework | Renewal: Upgrade last 1km of pipe from Leeston-Doyleston | 2014 | 12 | 12 | 12 |
The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.
5.10 Asset Valuation Details
The total replacement value of assets within the Doyleston Scheme is $2,025,568 as detailed in Table 5‑8 below.
Table 5‑8 Replacement Value, Doyleston
Plant and Equipment
| $245,882
|
Wastewater Reticulation
| Chamber | $2,898
|
| Lateral | $350,681
|
| Manhole | $223,743
|
| Pipe | $1,192,404
|
| Valve | $9,961
|
5.11 Renewals
The renewal profile has been taken from the 2019 5 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 5‑8 below.
Figure 5‑8 Doyleston Wastewater Renewal Profile
5.12 Critical Assets
The criticality model for Doyleston has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 5‑9 and Figure 5‑9 below show the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 5‑9 Length of Assets per Criticality Level
5
| Low | 5,334
|
4
| Medium-Low | 714
|
3
| Medium | 76
|
2
| Medium-High | 0 |
1
| High | 0 |
5.13 Asset Condition
The asset condition model was run for Doyleston in 2021. The methodology of the model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the model has been calculated for the reticulation assets (particularly pipes). Figure 5‑10 below shows the level of asset condition for all of the assets within this scheme that have a recorded known condition.
Table 5‑10 provides a description of the condition rating used within the condition model.
Table 5‑10 Asset Condition Grading
1.0
| Excellent |
| 2.0 | Good |
| 3.0 | Moderate |
| 4.0 | Poor |
| 5.0+ | Fail |
5.14 Funding Program
The 10 year budgets for Doyleston are shown by Table 5‑11. Budgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in Volume 1.
All figures are ($) not adjusted for CPI “inflation". They are calculated on historical data, and population growth where relevant.
Table 5‑11 Doyleston Budget Summary
| 2021/2022 | -
| -
|
| 2022/2023 | $10,000
| -
|
| 2023/2024 | -
| -
|
| 2024/2025 | -
| -
|
| 2025/2026 | -
| -
|
2026/2027
| -
| -
|
2027/2028
| -
| -
|
2028/2029
| -
| -
|
2029/2030
| -
| -
|
2030/2031
| -
| -
|
|
Total | $10,000
| -
|
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 5‑12 Key Projects
Capital Projects
| -
| Greenan Place pumps upgrades
| -
| $10,000
| -
| -
| TBC
|
* LoS refers to Level of Service; 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-3-Wastewater
