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5-Waters-Volume-5-Land-Drainage
10 Wairiri Valley Drainage Area
10.1 Scheme Summary
Scheme Area
| 377.46 ha |
Scheme Coverage in Ha (as at 1 July 2020)
| Class A | 152
|
| Class C | 45
|
Class E
| 155
|
Systems components
| Drain Length (m) | 14,440
|
| Pump stations (No.) | None |
| Other assets | None |
| History | Installation Date | Installed progressively from 1850's |
Value ($)
| Replacement Cost | $4,319,785
|
| Depreciated Replacement Cost | $4,319,785
|
| Financial | Annual maintenance cost
% of total Land Drainage maintenance
| $3,421/year on average
2% of total Land Drainage maintenance spend
|
Drainage Outlet
| Ultimate discharge point | Selwyn River |
| Sustainability | Sustainable drain management practices | Adopted and Encouraged |
10.2 Key Issues
The following key issues are associated with the Wairiri Valley Drainage area. A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.
Table 10‑1 Wairiri Valley Drainage District Key Issues
| The Wairiri Valley do not have a formal Land Drainage Committee to prioritise works and maintenance work is undertaken infrequently and on an ad hoc basis. | Continue to work with land owners and if more frequent requests for cleaning are received, ask Community to reinstate Committee. |
| Rates collected in this scheme are low and a low level of service is provided. | Continue to work with land owners as required to identify works required and increase the rate if necessary. |
10.3 Overview & History
The Wairiri scheme is located within the Wairiri Valley situated south west of the township of Whitecliffs.
The Wairiri Valley scheme has a rating area of 378ha, servicing a total area of 1690ha between Wairiri and Davis Roads. The ultimate receiving environment for this area is the Selwyn River.
There are 14.4km of classified drains.
Council staff met with local land owners in 2014 to discuss the level of service offered by the scheme and maintenance requirements. A single point of contact from the community has been appointed who should be contacted annually to determine cleaning requirements for the season.
In 2011, a variation to the Te Waihora Water Conservation Order was made, bringing a strong cultural focus into place. The Selwyn - Waihora Zone Committee (established under the Canterbury Water Management Strategy) also released its Zone Implementation Plan (ZIP) and ZIP addendum.
10.4 Resource Consents
There are no existing consents for this land drainage scheme.
Land drainage activities are controlled through Rules 5.57 and 5.58 under the Land and Water Plan. An application was lodged in November 2011, with a request that it be put on hold pending discussion with stakeholders.
10.5 Scheme Assets
This scheme is predominately Land drainage channels which are excavated open channels that intercept, convey and discharge groundwater to allow productive use of land.
No summary of material and diameter of these channels is available for this scheme.
10.6 Operational Management
Council delegates some aspects of management of the Land Drainage network to 9 Land Drainage Committee's comprising of local residents with an interest in the Land Drainage network. Council Service Delivery Staff work alongside the Committee's to prioritise and facilitate maintenance activities which are undertaken by a number of local contractors.
10.7 Photos of Main Assets
Photo 1: A Land Drainage Channel in the Scheme
|
10.8 Risk Assessment
A risk assessment has been undertaken for Wairiri Valley 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. No high risks have been identified for this scheme.
10.9 Asset Valuation Details
The total replacement value of assets within the Wairiri Valley Scheme is $4,319,785 with further details in Table 10‑2 below. All of the value is made up of channels.
Table 10‑2 Replacement Value, Wairiri Valley
|
Land Drainage | Channel | $4,319,785
|
Channels are broken down into drains, pipes and stock banks. The Wairiri Valley Land drainage district is made up of classified drains.
10.10 Renewals
The renewal profile has been taken from the 2019 5 Waters Valuation. There are no renewals for this scheme.
10.11 Critical Assets
The criticality model for Wairiri Valley 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 10‑3 and Figure 10‑2 below show the calculated criticality for all of the assets within this scheme that have a recorded known length.
Table 10‑3 Length of Assets per Criticality Level
5
| Low | 7,919 |
4
| Medium-Low | 0 |
3
| Medium | 0 |
2
| Medium-High | 0 |
1
| High | 6,541 |
10.12 Asset Condition
The asset condition model was run for the Wairiri Valley 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). There is no known recorded condition for assets within this scheme.
10.13 Funding Program
There are no projects specific to the Wairiri Valley scheme in the 10 year LTP budgets, however the scheme will benefit from a number of district-wide initiatives. The list of district wide projects can be found in 5Waters Activity Management Plan: Volume 1.
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