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7 Dunsandel Water Supply

7.1 Scheme Summary

Description		Quantity
Estimated Population Served		511
Scheme Coverage (1 Jan 2021)	Full Charges	172
	Half Charges	0
	>1 Charges	4
System Components	Bores/Intakes (No.)	1
	Treatment/Disinfection	UV
	Reservoirs (No.)	1
	Pump Stations (No.)	1
	Piped (m)	9,762
History	Original scheme installation date	1986
Value ($)	Replacement Cost	$1,906,696
Value ($)	Depreciated Replacement Cost	$1,201,694
Financial	Operator cost (scheduled and reactive maintenance) per connection	$319.06/connection
Demand (m³) (1 Jan – 31 Dec 2020)	Average daily	336
	Peak daily	856
	Minimum daily	5.9
	Average daily per connection	1.78
Type of Supply		Medium pressure and unrestricted
Target Pressure & Flow at boundary	Pressure	>310 kPa
Target Pressure & Flow at boundary	Flow	>40 L/min
Sustainability	Well Security	Unsecure

7.2 Key Issues

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

Table 7‑1 Dunsandel Scheme Issues

What's the Problem	What we plan to do
Supply is reliant on one source of water	Investigate an alternative site for a new bore.
Catchment management	To encompass a holistic view of the drinking water supply improved liaison with ECan and study of groundwater quality within the water supply protection zones are being investigated.
Backflow risk: the scheme is vulnerable to potential backflow issues associated with commercial and industrial connections.	There is currently a district wide backflow prevention project underway.

7.3 Overview & History

The Dunsandel Water Supply provides untreated groundwater to Dunsandel township and the adjacent 40 lot rural residential subdivision on Irvines Road (Sherwood Estate).

The current scheme was formed by combining the Dunsandel Township (installed 1986) and Sherwood Rural Residential (installed in 1991) schemes in July 1997. This allowed decommissioning of the problematic Dunsandel Well (ECan number L36/0601), and an improved cost/benefit relationship for operating both schemes.

There was also a previous subdivision on the Hororata-Dunsandel Road constructed in 1976 with a communal water scheme that was absorbed and decommissioned with the Dunsandel Township work.

The scheme was designed as a medium pressure, unrestricted metered supply complying with NZ Fire Fighting Code of Practice.

In 2009 the number of water quality transgressions rose significantly, and a combined regional, Selwyn District Council and community approach was taken to investigating the cause and recommending options to make the water safe to drink. An ultraviolet light system was installed and has eliminated bacteria (E.coli) entering the township network.

Figure 7-1
DUNSANDEL Water - Scheme map
Open larger map: 'Water Scheme'

Figure 7‑2 Scheme Schematic

7.4 System Capacity

Dunsandel has some potential for growth in terms of zoned land availability.

Table 7‑2 Capacity Summary

	Flow Rate (L/s)	Daily Volume (m³)	Annual Volume (m³)	Comments
Consented Take	25	1944	291,600 ⁽¹⁾	CRC010891.1
Peak Demand - current	25L/s ⁽²⁾	1,380⁽³⁾	215,111 ⁽⁴⁾
Abstraction capacity	24.7	2134	-	1 bore pump
Treatment capacity	24.7	2134	-	Assume UV can accommodate bore pump flow rate. Note current UV is non-compliant. And upgrade programmed 2015.
Distribution pumping	35	1944	291,600	2 pumps (duty/assist) from 70m³ storage – can buffer peak flows but not peak days

(1) inferred value, (2) Jan 2013, (3) 25 Jan 2015 (excluding fire fighting events), (4) Dec 2014- Dec 2015

7.5 Resource Consents

The Dunsandel water supply has a number of resource consents. Table 7‑3 shows the water take permitted by the resource consents for this scheme.

Table 7‑3 Resource Consents

Consent	Description	Location	Date Issued	Expiry Date	Consented Max Instantaneous Flow (L/s)	Consented Max Daily Volume (m³/day)
CRC010891.1	To take and use groundwater	cnr Sh1 & Hororata Dundanel Roads And Cnr Tramway And, IRVINES ROADS DUNSANDEL	12-Feb-10	31-Jan-35	22.5	1944

7.6 Water Quality

The Dunsandel water supply is a non-secure source and is currently sampled twice weekly at the source, treatment plant and weekly in the reticulation.

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

Source

There have been 50 incidences of E. coli identified in source water during this period, highlighting the importance of water treatment for this scheme.

Figure 7‑3 E. coli Transgressions - Source

Treatment

There has been one E. coli treatment transgression during this period which occurred in October 2014.

Zone

There has been one E. coli transgressions during this period which occurred in January 2013.

Chemical Analysis

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

Table 7‑4 Dunsandel Water Supply Raw Water Chemical Analysis Summary

Parameter	Standards	2008	2011	2013	2015	2017	2018	2019	Status
Total Lead (g/m3)	0.01 (Maximum Acceptable Value)	<0.0001	<0.00011	0.00013	0.0002	< 0.00011	<0.00011	<0.00011	✓
pH (pH units)	7-8.5 (Guideline Value)	7.1	7.1	7.3	7.4	7.2	7.3	7.3	✓
Total Hardness (g/m3 as CaCO₃)	<200 (Guideline Value)	63	54	54	67	63.2	74.3	79.7	✓
Total Calcium (g/m3)	n/v	16	13.7	13.9	16.8	16.64	19.71	21.02	✓
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)	9.4	8.8	8.6	10	9.86	11.01	11.94	✓
Nitrate - Nitrogen (g/m3)	11.3 (Maximum Acceptable Value)	4.2	2.8	2.7	3.6	4.5	6.54	6.54	✓

7.7 Scheme Assets

A summary of material and diameter for pipes in Dunsandel is shown by Figure 7‑4 and Figure 7‑5.

Figure 7‑4 Pipe Material – Dunsandel

Figure 7‑5 Pipe Diameter – Dunsandel

7.8 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.

7.9 Photos of Main Assets

Photo 1: Site Layout

7.10 Risk Assessment

A risk assessment has been undertaken for the Dunsandel 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 7‑5 outlines the risk priority rating, Table 7‑6 outlines the risks and the list of key projects is found in Table 7‑10. The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.

Table 7‑5 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 7‑6 Risks – Dunsandel

Risk	Action / Project	Year Identified	2014 Risk Rating	2017 Risk Ratinh	Residual Risk Rating
Lack of water storage	Demolish the concrete tank and replace with 33m3 tanks (min 4)	2014	27	27	12
Often power outages (especially when wind storms occur)	Install a generator on this scheme	2014	12	2.1	2.1
Only one source of supply - risk of loss	Investigate suitable location for second bore	2014	6	6	6
Electrical failure due to lightning or network spikes	Install surge diverters	2014	10	3.5	3.5
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	0.6	0.6
Non-compliance with the DWSNZ	DWSNZ - Age Testing	2014	10	0.7	0.7
Non-consented activities	Renewal of consents	2014	27	27	6
Inadequate treatment under all conditions	Install filtration	2017		40	7

7.11 Asset Valuation Details

The total replacement value of assets within the Dunsandel water scheme is $1,906,636 with further details in Table 7‑7 below.

Table 7‑7 Replacement Value, Dunsandel

Asset Class 1	Asset Class 2	Sum of Replacement Value
Plant and Equipment		$596,693
Water Reticulation	Hydrant	$59,003
	Lateral	$39,417
	Pipe	$1,040,827
	Supply Point	$136,576
	Valve	$30,256

7.12 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 7‑6 below. The majority of renewals occur in 2022/2023.

Figure 7‑6 Dunsandel Water Renewal Profile

7.13 Critical Assets

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

Table 7‑8 Length of Assets per Criticality Level

Criticality Bands		Length (m)
5	Low	2,559
4	Medium-Low	3,039
3	Medium	2,127
2	Medium-High	1,088
1	High	0

Figure 7-7
DUNSANDEL Water - Criticality
Open larger map: 'Water Criticality'

7.14 Asset Condition

The asset condition model was run for Dunsandel 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 7‑8 below shows the level of asset condition for these assets within this scheme that have a recorded known condition.

Figure 7-8
DUNSANDEL Water - Condition
Open larger map: 'Water Condition'

Table 7‑9 provides a description of the condition rating used within the condition model.

Table 7‑9 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 7‑9 shows the known historic pipe failures within this scheme.

Figure 7-9
DUNSANDEL Water - Scheme map
Open larger map: 'Water Scheme'

7.15 Funding Program

The 10 year budgets are shown by Table 3‑12. 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 7-10 Budget Summary

Years	Projects	Capital Projects
2021/2022	$31,000	$15,000
2022/2023	-	$590,000
2023/2024	-	$400,000
2024/2025	-	-
2025/2026	-	-
2026/2027	-	-
2027/2028	-	-
2028/2029	-	-
2029/2030	-	-
2031/2032	-	$600,000
Total	$31,000	$1,605,000

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 7-11 Key Projects

Account Label	GL	Description	Year 1($)	Year 2($)	Year 3($)	Years 4 to 10	Funding Split *
Capital Projects	-	WTP Upgrade	-	$560,000	$400,000	-	TBC
Capital Projects	-	Second WTP/source/reservoir	-	-	-	$600,000	TBC
Capital Projects	-	Valves each side of SH	-	$30,000	-	-	100% LoS
Capital Projects	-	Pressure sensors	$15,000				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.