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17 Springfield Stormwater Scheme

17.1 Scheme Summary

Description		Quantity
Scheme Area		38.94 ha
Scheme Coverage (as at 1 Jan 2021)	Rating numbers	141
System components	Piped (m)	120
	Swales (m)	1,160
	Drains (m)	0
	Manholes/Inspection Chambers (No.)	0
	Treatment	N/A
	Other	8 soakholes
Value ($)	Replacement Cost	$41,399
Value ($)	Depreciated Replacement Cost	$41,399
Financial	Operator cost (scheduled and reactive maintenance) per connection	$17.87/connection
Planning	Stormwater Management Plan	Required
Planning	No. SDC stormwater consents	1
Demand	Mean Annual Rainfall (mm)	950
Demand	10% AEP (10 year) 1hr rainfall depth (mm)	20.3
Sustainability	Sustainable drain management practices	Adopted and Encouraged

17.2 Key Issues

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

Table 17‑1 Springfield Scheme Issues

What's the Problem	What we plan to do
Stormwater discharge is a non-consented activity	Development of a stormwater catchment consent (underway with consent application lodged with ECan).

17.3 Overview & History

Springfield is located on SH73 near the foot hills. Stormwater is disposed of to roadside soakholes. Soakholes are maintained by roading however a stormwater budget line exists for Environment Canterbury compliance and consenting.

Figure 17-1
SPRINGFIELD Stormwater - Scheme map
Open larger map: 'Stormwater Scheme'

Figure 17‑2 Scheme Schematic

17.4 Resource Consents

Council have applied for a global consent for the Springfield stormwater network (Table 17-2). The application is in progress with ECan.

Table 17-2 Resource Consent

Consent	Description	Location	Date Issued	Expiry Date
CRC186176	To discharge stormwater to land from the existing stormwater network of Springfield	Springfield	TBC	TBC

17.5 Integrated Stormwater Management Plan

An integrated stormwater management plan has been prepared for Sprinfield and submitted to ECan (June 2017), as part of the application for CRC186176.

17.6 Scheme Assets

Council has a wide variety of stormwater assets within the district. A brief description of the assets within this scheme is provided below:

a. Swale (Grassed) – Is a longitudinal open channel which is lined with grass. The swale both conveys and treats stormwater.

b. Infiltration basin – is a stormwater management device which is used to store, treat and dispose of stormwater to the ground via soakage.

c. Soakholes – Are used to dispose of stormwater to ground in areas where the ground water table is low and soil permeability is high.

A summary of material and diameter for channels and pipes is shown in Figures 17-3 and 17-4 below.

Figure 17‑3 Pipe Material - Springfield

Figure 17‑4 Pipe Diameter - Springfield

17.7 Operational Management

The stormwater network 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.
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.

17.8 Photos of Main Assets

There were no photos available for this scheme.

17.9 Rapid Flood Modelling

The Council has undertaken 'Rapid Flood Hazard Assessment' modelling for its main townships. The modelling uses DHI MIKE 21 to simulate rainfall on grid with the outputs processed through ArcGIS producing maps illustrating a range of flood deeps during different rainfall intensities and durations.

The rapid flood assessment has been generated to provide a high level summary of potential flood and ponding areas across the district during extreme rainfall events. The results from this study are not to be used to set floor levels. The results have not been ground tested and therefore are indicative only.

For a 50 year event, Figure 17-3 shows the predicted flooding for Springfield.

Figure 17‑5 Rapid Flood Modelling, Springfield

17.10 Risk Assessment

A risk assessment has been undertaken for the Springfield 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 17‑3 details the risk priority rating and Table 17‑4 outlines the risks for this scheme.

Table 17‑3 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 17‑4 Risks - Springfield

Risk	Action/Project	Year Identified	2014 Risk Rating	2017 Risk Rating	Residual Risk Rating
Non-consented activities	Renewal of consents	2014	27	27	6

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

17.11 Asset Valuation Details

The total replacement value of assets within the Springfield Scheme is $41,399 as detailed in Table 17‑5 below.

Table 17‑5 Replacement Value, Springfield

Asset Class 1	Asset Class 2	Sum of Replacement Value
Stormwater Reticulation	Channel	$41,399

17.12 Renewals

The renewal profile has been taken from the 2019 5 Waters Valuation. There are no renewals scheduled for this scheme.

17.13 Critical Assets

The criticality model for Springfield 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 17‑6 and Figure 17‑6 below show the calculated criticality for all of the assets within this scheme that have a recorded known length.

Table 17‑6 Length of Assets per Criticality Level

Criticality Bands		Length (m)
5	Low	1,163
4	Medium-Low	0
3	Medium	0
2	Medium-High	0
1	High	0

Figure 17-6
SPRINGFIELD Stormwater - Criticality map
Open larger map: 'Stormwater Criticality'

17.14 Asset Condition

The asset condition model was run for Springfield 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 17‑7 below shows the level of asset condition for all of the assets within this scheme that have a recorded known condition.

Figure 17-7
SPRINGFIELD Stormwater - Condition map
Open larger map: 'Stormwater Condition'

Table 17‑7 provides a description of the condition rating used within the condition model.

Table 17‑7 Asset Condition Grading

Condition Rating	Grading
1.0	Excellent
2.0	Good
3.0	Moderate
4.0	Poor
5.0+	Fail

17.15 Funding Program

The 10 year budgets are shown by Table 17‑8. 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 17‑8 Budget Summary

Years	Projects	Capital Projects
2021/2022	-	$15,000
2022/2023	-	-
2023/2024	-	$50,000
2024/2025	-	-
2025/2026	-	-
2026/2027	-	-
2027/2028	-	-
2028/2029	-	-
2029/2030	-	-
2031/2032	-	-
Total	-	$65,000

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 17‑9 Key Projects

Account Label	GL	Description	Year 1($)	Year 2($)	Year 3($)	Years 4 to 10	Funding Split *
Capital Projects	-	Opening up of culvert - railway station; new structure e.g. scruffy dome	$15,000	-	$50,000	-	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.