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3 Castle Hill Water Supply

3.1 Scheme Summary

Description		Quantity
Estimated Population Served		406
Scheme Coverage (1 Jan 2021)	Full Charges	131
	Half Charges	0
	>1 Charges	0
System Components	Bores/Intakes (No.)	1 River Gallery
	Treatment/Disinfection	1
	Reservoirs (No.)	3
	Pump Stations (No.)	1
	Piped (m)	8,820
History	Original scheme installation date	1982
Value ($)	Replacement Cost	$2,696,878
Value ($)	Depreciated Replacement Cost	$1,233,115
Financial	Operator cost (scheduled and reactive maintenance) per connection	$291.05/connection
Demand (m³) (1 Jan – 31 Dec 2020)	Average daily (m³/day)	140
	Peak daily (m³/day)	739
	Minimum daily (m³/day)	-
	Average daily per connection (m³/day)	0.5
Type of Supply		Unrestricted
Target Pressure & Flow at boundary	Pressure	>310 kPa
Target Pressure & Flow at boundary	Flow	>20 L/min
Sustainability	Well Security	Unsecure

3.2 Key Issues

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

Table 3‑1 Castle Hill Scheme Issues

What's the Problem	What we plan to do
Castle Hills isolated location and distance from the maintenance contractors base keeps the operational and maintenance costs high. The rating base is small and there are also limited skills available within Castle Hill.	Council will investigate the potential for remote monitoring in conjunction with identifying and training and local operators to perform basic operation and maintenance tasks, including consideration of health, safety and employment regulations. Council also plans to investigate optimisation of maintenance and renewals to ensure costs stay at a minimum.
The water treatment plant requires upgrading to comply with the Health Act and DWSNZ. However, this may prove difficult for an unprotected source catchment with variable water quality.	Council will identify options. Through the Water Safety Plans, process barriers will be installed to manage potential risks.
Catchment management	Council are investigating water quality within the water supply protection zones, and working with ECan on this matter
Pressure zoning	Council are considering pressure zoning and additional pressure monitoring in the reticulation network. We are developing a Target Pressure Plan and Network Management Strategy.

3.3 Overview & History

The Castle Hill Water Supply was commissioned during 1982 servicing the township, which was developed to utilise the high country tourist attractions within the area i.e. skiing and tramping.

The scheme draws water from an infiltration gallery established in the base of Thomas Stream, an unprotected, but undeveloped catchment. Water is treated and has turbidity control and chlorination but does not fully comply with DWSNZ. This is a gravity fed supply and full fire fighting capacity is provided from 3 of 500 m³ timber tanks.

There are few permanent residents in the village which has been developed in stages since the early 1980s. Most properties are used as seasonal holiday homes with a number available for holiday rental. There are currently no business activities in the village. Further development is planned, with a hospitality facility. The water headworks will provide sufficient capacity, in line with the 1982 design.

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.

Figure 3-1
CASTLE HILL Water - Scheme map
Open larger map: 'Water Scheme'

Figure 3‑2 Scheme Schematic

3.4 System Capacity

Castle Hill Village has not developed to the extent anticipated when the water supply was constructed in the early 1980s. About 126 houses have been built. Most are holiday homes used predominantly over the winter period (ski season) with a few occupied by permanent residents. There is no business activity. Small subdivisions and land sales continue but this can easily be accommodated by the current headworks infrastructure. Figure 3-3 shows the projected water demand, based on housing projections.

The supply includes three large reservoirs providing a total of around 1500 m³ of treated water storage capacity, about five times peak day demand. The large storage volume permits selective abstraction of water from Thomas Stream, i.e. when water quality is poor the intake is shut down. The 200mm diameter supply main from the reservoir offers plenty of capacity for current and foreseeable needs.

Hydraulic models have been used to plan future water infrastructure for Castle Hill, as part of a master planning exercise. The master planning provides an assessment of the sizing and timing of new infrastructure for new water sources and pipelines to service growth. Part of the master planning requires a water balance to be developed to forecast growth, using historical peak demand per household. The water balance forecasts the peak instantaneous flow per year versus the water resources available to determine the staging of new water sources. The master planning exercise has identified that a new water source or consent amendment will be required in 2022/23, to service growth in Castle Hill (Table 3-3).

Table 3‑2 Capacity Summary

Flow Rate

(L/s)

Daily Volume

(m³)

Annual Volume

(m³)

Comments

Consented Take

13.8

1192

178,800 *

Peak Demand

9.2 **

580 **

~60,800

* inferred value, ** 10 Jan 2015

Table 3-3 Future Sources

	Year	Yield (L/s)
Additional source/consent amendment/ Treated water capacity upgrade	2022/23	14

V2 Castle Hill - Water Balance Assessment.PNG

Figure 3‑3 Castle Hill Water Demand

Figure 3-4 Castle Hill Master Plan

3.5 Resource Consents

The Castle Hill water supply has a number of resource consents. Table 3‑4 shows the water take permitted by the resource consents for this scheme.

Table 3‑4 Resource Consents

Consent	Description	Location	Date Issued	Expiry Date	Consented Max Instantaneous Flow (L/s)	Consented Max Daily Volume (m³/day)
CRC991053	To take surface water, at or about map reference NZMS 260 K34:040-773, for community water supply.	Castle Hill Village, CASTLE HILL	24-Dec-98	23-Dec-33	13.8	1192

3.6 Water Quality

The Castle Hill water supply is a non-secure source where the source and treatment plant is sampled weekly and reticulation is sampled monthly.

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

Source

There have been 110 samples with E. coli identified during the period 2013 - 2020, highlighting the importance of water treatment for this scheme.

Figure 3‑5 E. coli identified in source water

Treatment

There have been four E. coli treatment transgressions within this period, they all occurred in July 2012.

Zone

There have been three E. coli transgression during this period, they all occurred in July 2012.

Chemical Analysis

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

Table 3‑5 Castle Hill Water Supply Raw Water Chemical Analysis Summary

Parameter	Standards	2008	2011	2013	2015	2017	2018	2020	Status
Total Lead (g/m3)	0.01 (Maximum Acceptable Value)	0.00022	0.00023	0.00014	0.00031	0.00013	0.000232	<0.00011	✓
pH (pH units)	7-8.5 (Guideline Value)	7.5	7	7.1	7.4	7.4	7.3	7.6	✓
Total Hardness (g/m3 as CaCO₃)	<200 (Guideline Value)	21	19.6	19.9	21	22.3	21.03	23.17	✓
Total Calcium (g/m3)	n/v	7	6.6	6.9	7.3	7.67	7.27	7.89	✓
Total Iron (g/m3)	<0.2 (Guideline Value)	<0.02	0.051	0.025	0.023	< 0.021	<0.021	<0.021	✓
Total Sodium (g/m3)	<200 (Guideline Value)	2.5	2.5	2.4	2.6	2.55	2.26	2.61	✓
Nitrate - Nitrogen (g/m3)	11.3 (Maximum Acceptable Value)	0.05	0.09	0.07	0.08	< 0.05	0.057	0.052	✓

3.7 Scheme Assets

A summary of material and diameter for pipes in Castle Hill is shown below by Figure 3‑6 and Figure 3‑7.

Figure 3‑6 Pipe Material – Castle Hill

Figure 3‑7 Pipe Diameter – Castle Hill

3.8 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.

3.9 Photos of Main Assets

Photo 1: Northern End of Intake Structure	Photo 2: Silt Trap (lid been replaced)
Photo 3: Treatment Shed	Photo 4: Reservoirs

3.10 Risk Assessment

A risk assessment has been undertaken for the Castle Hill 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 3‑6 outlines the risk priority rating, Table 3‑7 outlines the risks and the list of key projects is found in Table 3‑11.

Table 3‑6 Risk Priority Rating

Risk Score	Level of Risk	Risk Response
> 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 3‑7 Risks – Castle Hill

Risk	Action/Project	Year Identified	2014 Risk Rating	2017 Risk Rating	Residual Risk Rating
High water use due to leaks causes additional operation costs	Leak detection	2014	27	27	12
Insufficient monitoring of Cl2 results in treatment system over or inadequately chlorinating	Install chlorine analyser before reservoirs to check dose	2014	12	2.1	2.1
Manual operation of scheme is costly	Automate flushing to waste at reservoir site	2014	4	2.1	2.1
No reservoir turnover and bottom filled	Upgrade pipework so that water goes through all reservoirs (connect 2 res's to the other 1). Install additional pressure transducer.	2014	12	12	6
Poor tank maintenance leads to tank failure	Maintenance - re tighten covers/liners	2014	6	6	2.1
Electrical failure due to lightning or network spikes	Install surge diverters	2014	6	2.1	2.1
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 treatment under all conditions	Water quality upgrade	2017		45	3.5

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

3.11 Asset Valuation Details

The total replacement value of assets within the Castle Hill water scheme is $2,696,878 with further details in Table 3‑8 below.

Table 3‑8 Replacement Value, Castle Hill

Asset Class 1	Asset Class 2	Sum of Replacement Value
Plant and Equipment		$1,369,222
Water Reticulation	Hydrant	$47,316
	Hydrant	$47,316
	Lateral	$69,980
	Pipe	$942,613
	Supply Point	$221,352
	Valve	$46,394

3.12 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 3‑8 below. The majority of renewals occur in 2037/38.

Figure 3‑8 Castle Hill Water Renewal Profile

3.13 Critical Assets

The criticality model for Castle Hill 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 3‑9 and Figure 3‑9 below shows the calculated criticality for all of the assets within this scheme that have a recorded known length.

Table 3‑9 Length of Assets per Criticality Level

Criticality Bands		Length (m)
5	Low	3,705
4	Medium-Low	1,787
3	Medium	1,711
2	Medium-High	1,860
1	High	169

Figure 3-9
CASTLE HILL Water - Criticality
Open larger map: 'Water Criticality'

3.14 Asset Condition

The asset condition model was run for Castle Hill 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 3‑10 below shows the level of asset condition for these assets within this scheme that have a recorded known condition.

Figure 3-10
CASTLE HILL Water - Condition
Open larger map: 'Water Condition'

Table 3‑10 provides a description of the condition rating used within the condition model.

Table 3‑10 Asset Condition Grading

Condition Rating	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 3‑11 shows the known historic pipe failures within this scheme.

Figure 3-11
CASTLE HILL Water - Pipe Faults map
Open larger map: 'Water Pipe Faults'

3.15 Funding Program

The 10 year budgets are shown by Table 3‑11. Budgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in

Volume 1. 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 3‑11 Budget Summary

Years	Projects	Capital Projects
2021/2022	$5,000	-
2022/2023	-	$30,000
2023/2024	-	-
2024/2025	-	-
2025/2026	-	-
2026/2027	-	-
2027/2028	-	-
2028/2029	-	-
2029/2030	-	-
2031/2032	-	-
Total	$5,000	$30,000

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 3‑12 Key Projects

Account Label	GL	Description	Year 1($)	Year 2($)	Year 3($)	Years 4 to 10	Funding Split *
Capital Projects	TBC	Pressure sensors	-	$30,000	-	-	100% LoS
Projects	TBC	Investigate water loss	$5,000	-	-	-	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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​​​​​​​​​​3​ Castle Hill Water Supply

3.1 Scheme Summary

3.2 Key Issues

​

3.3 Overview & History

3.4 System Capacity​

3.5 ​Resource Consents

3.6 Water Qu​​​ality