1​   Acheron Water Supply​

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1.1       Scheme Summary

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1.2       Key Issues

The following key issues are associated with the Acheron water supply.  A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.​

Table 1‑1 Acheron Scheme Issues

1.3       Overview & History

The Acheron water supply (previously part of the Selwyn Rural Water Scheme) provides treated surface water to over 13,180 hectares of rural land. Water is also supplied to the Terrace Downs High Country resort and the Tui Creek development (a single connection for each). These are private water schemes beyond the point of supply.

The Acheron scheme is a restricted supply with a design of 65 L/ha/day for stock use and 2m³ for domestic use per 200 ha of a single title farm.  Water is predominantly used for agricultural purposes.
The water source is a weir intake on the Dry Acheron Stream. Disinfection is by way of gas chlorination at the two 500 m³ timber tank reservoirs.  The supply is a gravity system with three break pressure tanks and four pressure reducing valves through the system.  

 Council's Supervisory Control and Data Acquisition (SCADA) system is used to monitor the reservoirs and flowmeter, recording parameters including daily flows and reservoir levels.  There is no remote control functionality.  The SCADA system generates alarms when operator intervention is required.  These include low reservoir water level and communications failure.  A battery backup is provided to maintain essential SCADA functions and alarms in event of a power supply failure.  The SCADA system is monitored at Council's Rolleston office, SICON's Rolleston office and key staff and operators have remote access to SCADA.  A formalised alarm response procedure is documented. 

The scheme was installed in 1982 to replace the unreliable Snowden and Glenroy Water Race Schemes which had been in operation for over 100 years. The original scheme did not include Fighting Hills area which was added after the main system was commissioned.  The Downs Road scheme was included in the 1990s. A duplicate water main (100 mm diameter) was installed in the Acheron area in 2000 to serve the Terrace Downs High Country Resort and perceived additional demand.​

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​​ Figure 1-1
ACHERON Water - Scheme map
Open larger map: 'Water Scheme'

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Figure 1‑2 Scheme Schematic

1.4       System Capacity

The Rural Water Supply (RWS) provides water to about 100 connections across a large rural area.  This is used for stock and other on-farm purposes, as well as for residential drinking water.  The Terrace Downs High Country Resort and Tui Creek development also receive water from the RWS.   Water is supplied to a tank at each point of supply via a flow restrictor that limits the daily volume to an agreed allocation.  Peak day demand is approaching the consented abstraction limit capacity.  There is some uncertainty regarding the two consents that needs to be resolved.  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 1‑2 Capacity Summary

1.5       Resource Consents

TheAcheron water supply has a number of resource consents. Table 1‑3 shows the water take permitted by the resource consents for this scheme.

Table 1‑3 Resource Consents

1.6       Water Quality

The Acheron water supply source is non-secure.

The following details E. coli transgressions for the period 2012 to 2020.  

Source

There have been 127 incidences of E. coli identified in source water samples during this period.

​Figure 1‑3 Number of samples with E.coli identified (Acheron source water)

Treatment

There has been 1 E. coli treatment transgression during this period for Acheron which occurred in January 2017.​

Zone

There have been 2 E. coli Zone transgressions during this period for the Acheron water supply.

Chemical Analysis

The following is a summary of the raw water chemical analysis carried out at the Acheron Water Supply. 

Table 1‑4 Acheron Water Supply Raw Water Chemical Analysis Summary

1.7       Scheme Assets

A summary of material and diameter for pipes in Acheron is shown below in Figure 1‑4 and Figure 1‑5.

Figure 1‑4 Pipe Material – Acheron

 ​Figure 1‑5  Pipe Diameter – Acheron

​1.8       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.

1.9       Photos of Main Assets

​ Photo 1 - Dry Acheron weir and intake structure	​ Photo 2 - ​Reservoirs and chlorination shed
​ Photo 3 - BPT 1​	​ Photo 4 - Fighting Hill BPT-2​

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1.10       Risk Assessment

A risk assessment has been undertaken for the Acheron 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 1‑5 outlines the risk priority rating, Table 1‑6 outlines the risks and the list of key projects is found in Table 1‑11.

Table 1‑5 Risk Priority Rating

 Table 1‑6 Risks – Acheron

​​The list of district wide risks can be found in 5 Waters Activity Management Plan: Volume 1.

1.11       Asset Valuation Details

The total replacement value of assets within the Acheron water scheme is $6,997,173 with further details in Table 1‑7 below.

Table 1‑7 Replacement Value, ​Acheron

1.12       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 1‑6 below. Some assets are already due for renewal. There is another peak in renewals in 2032 and 2049.

Figure 1‑6 Acheron Water Renewal Profile

​1.13       Critical Assets

The criticality model for Hororata-Acheron 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 1‑8 and Figure 1‑7 below shows the calculated criticality for all of the assets within this scheme that have a recorded known length.

Table 1‑8 Length of Assets per Criticality Level

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​​ Figure 1-7
ACHERON Water - Criticality
Open larger map: 'Water Criticality'

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​1.14       Asset Condition

The asset condition model was run for the Acheron 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 1‑8 below shows the level of asset condition for these assets within this scheme that have a recorded known condition.​

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​​ Figure 1-8
ACHERON Water - Condition
Open larger map: 'Water Condition'

Table 1‑9 provides a description of the condition rating used within the condition model.

Table 1‑9 Asset Condition Grading

The number of pipe faults is also measured through the asset management system. Figure 1‑9​ shows the known historic pipe failures within this scheme.

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​​ Figure 1-9
ACHERON Water - Pipe Faults
Open larger map: 'Water Pipe Faults'

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​1.15       Funding Program

The 10 year budgets for Acheron are shown by Table 1‑10. Bu​dgets 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 1‑10 Acheron Budget Summary

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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 three major projects for Acheron water scheme in the LTP budget.

Table 1‑11 Key Projects

* 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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