Christchurch City Council

Supplementary Agenda

 

 

Notice of Meeting:

An ordinary meeting of the Christchurch City Council will be held on:

 

Date:                                     Thursday 12 May 2016

Time:                                    9.30am

Venue:                                 Council Chambers, Civic Offices,
53 Hereford Street, Christchurch

 

 

Membership

Chairperson

Deputy Chairperson

Members

Mayor Lianne Dalziel

Deputy Mayor Vicki Buck

Councillor Jimmy Chen

Councillor Phil Clearwater

Councillor Pauline Cotter

Councillor David East

Councillor Jamie Gough

Councillor Yani Johanson

Councillor Ali Jones

Councillor Paul Lonsdale

Councillor Glenn Livingstone

Councillor Raf Manji

Councillor Tim Scandrett

Councillor Andrew Turner

 

 

9 May 2016

 

 

 

Principal Advisor

Dr Karleen Edwards

Chief Executive

Tel: 941 8554

 

Jo Daly

Council Secretary

941 8581

Jo.Daly@ccc.govt.nz

www.ccc.govt.nz

Note:  The reports contained within this agenda are for consideration and should not be construed as Council policy unless and until adopted.  If you require further information relating to any reports, please contact the person named on the report.
Watch Council meetings live on the web:
http://councillive.ccc.govt.nz/live-stream

 


Council

12 May 2016

 

 


Council

12 May 2016

 

TABLE OF CONTENTS

 

55.     Resolution to Include Supplementary Reports...................................................................... 4

Infrastructure, Transport and Environment

56.     Avon Temporary Stopbanks Management............................................................................. 5

57.     Resolution to Exclude the Public........................................................................................... 24


Council

12 May 2016

 

 

55 Resolution to Include Supplementary Reports

1.       Background

1.1          Approval is sought to submit the following reports to the Council meeting on 12 May 2016:

56.   Avon Temporary Stopbanks Management

58.   Community Capital Delivery Unit: Bruce Terrace Cottages (Akaroa) Social Housing Complex Rebuild

1.2          The reason, in terms of section 46A(7) of the Local Government Official Information and Meetings Act 1987, why the reports were not included on the main agenda is that they were not available at the time the agenda was prepared.

1.3          It is appropriate that the Council receive the reports at the current meeting.

2.       Recommendation

2.1          That the reports be received and considered at the Council meeting on 12 May 2016.

 

 


Council

12 May 2016

 

Report from Infrastructure, Transport and Environment Committee  – 5 May 2016

 

56.    Avon Temporary Stopbanks Management

Reference:

16/516426

Contact:

Keith Davison

keith.davison@ccc.govt.nz

941 8071

 

 

 

1.   Infrastructure, Transport and Environment Committee Consideration

 

Councillor Livingstone joined the table for the discussion of this item.

The Committee considered the staff report and noted that the Part A report containing the Committee Recommendations will be considered at the Council meeting on 12 May 2016.

 

 

2.   Staff Recommendations

 

That the Infrastructure, Transport and Environment Committee recommend that the Council:

1.         Grant approval for the fast-tracked sandbag replacement construction works to be procured under existing staff delegations.

2.         Progress the preferred Temporary Stopbanks Management option (Option 1) to detailed design, consenting and construction.    

 

 

3.   Infrastructure, Transport and Environment Committee Decisions Under Delegation

 

Part C

The Committee made no decisions under delegation.

 

4.   Infrastructure, Transport and Environment Committee Recommendation to Council

 

Part A

That the Council:

1.         Grant approval for the fast-tracked sandbag replacement construction works to be procured under existing staff delegations.

2.         Progress the preferred Temporary Stopbanks Management option (Option 1) to detailed design, consenting and construction.    

 

 

 

Attachments

No.

Report Title

Page

1

Avon Temporary Stopbanks Management

7

 

 

 


Council

12 May 2016

 

 

Avon Temporary Stopbanks Management

Reference:

16/418006

Contact:

Keith Davison

keith.davison@ccc.govt.nz

941 8071

 

 

1.       Purpose and Origin of Report

Purpose of Report

1.1          The purpose of this report is for the Infrastructure, Transport and Environment Committee to recommend to Council which option for management of the Avon Temporary Stopbanks progresses to detailed design and construction.

Origin of Report

1.2          This report is staff generated.

2.       Significance

2.1          The decision in this report is of low significance in relation to the Christchurch City Council’s Significance and Engagement Policy.

2.1.1     The level of significance was determined by considering the proposed improvement (or maintenance) of the level of service, and the area which benefits from the temporary stopbanks. There has been a level of public interest in the stopbanks, and this project will provide greater certainty about Council's intentions for the management of the temporary stopbanks. The overall programme is significant and has wide ranging impacts across the city however the proposed costs are comparably low.  The temporary stopbanks management project is one of the projects being delivered on a fast-track programme within the LDRP.  As a result any community engagement will be undertaken in parallel with the detailed design tasks to speed project delivery.

2.1.2     At this stage community consultation has been limited to engagement with the Burwood-Pegasus Community Board who have had a presentation and discussion on the results of the investigation in the temporary stopbanks.

 

3.       Staff Recommendations

That the Infrastructure, Transport and Environment Committee recommend that the Council:

1.              Grant approval for the fast-tracked sandbag replacement construction works to be procured under existing staff delegations.

2.              Progress the preferred Temporary Stopbanks Management option (Option 1) to detailed design, consenting and construction.       

 

4.       Key Points

4.1          This report supports the Council's Long Term Plan (2015 - 2025):

4.1.1     Activity: Flood Protection and Control Works

·           Level of Service: 14.1.5 Implement Land Drainage Recovery Programme works to reduce flooding

4.2          The following feasible options have been considered:

·      Option 1 - Enhanced level of service (preferred option)

·      Option 2 - Maintenance of existing design level of service

·      Option 3 - Do minimum

4.3          Option Summary - Advantages and Disadvantages (Preferred Option)

4.3.1     The advantages of this option include:

·           Increased level of service provided along the majority of the temporary stopbanks

·           Reduced risk of failure

·           Greater certainty for residents about the level of protection provided

4.3.2     The disadvantages of this option include:

·           No increase in level of service provided to a small area of residential red zone

·           Higher cost than maintaining current level of service

 

5.       Context/Background

Construction of Avon Temporary Stopbanks

5.1          Temporary stopbanks were constructed following the 2011 earthquakes to mitigate tidal flood risk in the lower reaches of the Avon River. They extend from just upstream of North Avon Road to Bridge Street (Figure 1).

Figure 1 Temporary Stopbanks Extent

5.2          The stopbanks were initially constructed to a level of 10.8 m and later raised to 11.2 m RL (Christchurch Drainage Datum, CDD. All subsequent levels are quoted in CDD). The stopbanks were constructed under emergency circumstances without the level of detail or design that would typically apply to a permanent structure. At the time of construction the temporary stopbanks had a perceived design life of 5 years and while their height intended to match expected tide events, they were not designed for any specific flood event.

Avon Temporary Stopbank Management Investigation

5.3          The long-term management options for river and tidal flood protection are not decided, and the location and timing of permanent stopbanks is dependent on decisions about the Residential Red Zone (RRZ) as the optimal location for the permanent stopbanks is further away from the river than the current alignment.

5.4          Due to the dependency on RRZ decisions a study was initiated by the LDRP to:

·      Assess the condition of the stopbanks through a walkover and geotechnical investigations;

·      Determine the risks to the temporary stopbanks during future earthquakes, flood events and daily tidal flows, and develop a decision tree with regards to modifying the form and location of ongoing temporary measures;

·      Investigate options for altering existing temporary stopbanks to extend their lifespan and make them more permanent whilst adhering to the objectives of the Flood Protection Activity Management Plan; and

·      Produce an issues and options report detailing potential strategies for the temporary stopbanks, recommending a preferred option.

5.5          The Temporary Stopbanks investigation considered the current state of the temporary stopbanks and whether their life could be extended up to a maximum of 20 years. The rationale for extending their life is that:

·      The location of the permanent stopbanks is dependent on decisions about the Residential Red Zone (RRZ);

·      Permanent stopbanks will need to be considered in the context of sea level rise and other adaptive strategies, and as such will take some time to fully resolve; and

·      The capital cost of the permanent stopbanks is significant, and outlaying this large amount of capital early in the programme will restrict addressing some other high risk areas.

5.6          The study has been completed and draft reports submitted. The study concluded that aside from the sections with sandbag construction, the temporary stopbanks are relatively stable. This was contrary to the expectations of the Project Control Group, which expected the study to identify that significant strengthening works are required. However, the Project Control Group and Project Advisory Group are satisfied that the assessment carried out is robust and have confidence in the findings.

5.7          A peer review is currently underway and is expected to be completed within a month. Any findings from this peer review will be incorporated into the final reports and included in the detailed design.

Key risks identified

5.8          The key risks identified by the study were inundation of protected areas either by overtopping and/or piping failure due to:

·      Deterioration of sandbags

·      River flooding (as opposed to the tidal events that the stopbanks were designed to protect against)

5.9          The stopbanks are also susceptible to large earthquake events, but it is not considered economic to strengthen the temporary stopbanks to withstand large magnitude earthquakes. Much of the stopbanks are currently located on the edge of the river which is at highest risk of lateral spread in an earthquake. Permanent stopbanks are likely to follow an alternative alignment so investment in strengthening the stopbanks to withstand seismic events would be lost, and is better withheld until the final alignment of the permanent stopbanks has been decided.

5.10       In the recent February 14 2016 earthquake (M5.7) the stopbanks experienced cracking at one location on New Brighton Road (Figure 2). Increased seepage was also identified at another location near Waitaki Street. An emergency works package was developed to repair these two sections, and the crack has since been repaired and the seepage works are soon to begin.

5.11       Seepage through the stopbanks in some locations is not unexpected and in some places may cause some nuisance ponding on adjacent land. However, the risk of failure as a result of this has been assessed and is not considered a significant risk. If seepage is noticed to increase in an area then remedial works may be required to reduce this.

5.12       A survey of the stopbank crest following the February 14 2016 earthquake revealed only minor (<100 mm) changes in level of the stopbank since the previous crest survey in May 2015 (except where sandbags had deteriorated or been removed). This has shown that aside from some localised failures the stopbanks as a whole performed well during the earthquake.

Figure 2 Earthquake damage to temporary stopbanks (New Brighton Rd after 14.2.16)

 

5.13       To address damage arising from earthquakes there are two approaches to the short- to medium-term management of the stopbanks:

·      As the stopbanks are largely stable, intervene in a reactive manner only when damage occurs; or

·      Strengthen the stopbanks to minimise damage due to earthquakes

5.14       Reactive strengthening and seepage control is seen to provide the best value to Council while maintaining the level of protection required. It will involve the capital funds already allocated being applied over time as required in localised strengthening works.

Replacement of sandbag sections

5.15       Addressing the sections with deteriorated sandbags (Figure 3) has been identified as the highest priority. Five specific sections, totally 560 m, were identified where strengthening work is recommended to commence as soon as possible.

5.16       Sandbags were used during the original construction where there was limited space available or only a nominal height required. In some locations these access restrictions have now been resolved, which enables alternative construction methods to be considered. Such alternatives include concrete barriers (either with or without, the backing of a compacted gravel bank), or compacted gravel embankments. 

5.17       The replacement of the sandbag sections with more robust materials is included in all the options presented.

 

Figure 3 Deteriorated temporary stopbank sandbags on New Brighton Road

 

Flood overtopping

5.18       The temporary stopbanks were originally installed to provide tidal protection for a 1% Annual Exceedance Probability (AEP) tide with 300 mm freeboard. This equated to a design level of RL11.2 m. No allowance for sea level rise was made.

5.19       Permanent stopbanks are likely to provide protection (with 400 mm freeboard) for the 1% AEP fluvial event down to a minimum RL dictated by the peak 1% AEP tide level with sea level rise.

5.20       The risk assessment considered the risks due to overtopping for the 0.5%, 1% and 2% AEP events. This assessed the societal and individual risks from these events using Failure Modes and Effects Analysis (FMEA) method and risk analysis as prescribed within the Australian Council of Large Dams (ANCOLD) guidelines. FMEA is a systematic method for evaluating a structure to identify where and how it might fail and the risk analysis is used to assess the relative impact of different failures, in order to identify the parts of the structure that are most in need of change. 

5.21       The conclusion of this analysis was that for all three events (0.5%, 1%, and 2% AEP) the risk posed by overtopping exceed the ANCOLD limit of tolerability for societal and individual risk for the existing stopbanks.

5.22       The risks are driven by deterioration of the sandbags (outlined above) and flood overtopping. If these two risks were resolved, then the risk of failure associated with the temporary stopbanks would be within societal and individual tolerability limits, as defined by the ANCOLD criteria, for a design life up to 20 years.

5.23       The options presented below provide three alternatives for the management of the temporary stopbanks and these risks.


5.24        

6.       Option 1 - Enhanced level of service (preferred)

Option Description

6.1          This option consists of:

·      Replacement of the sandbags with more robust materials; and

·      Raising the stopbank level to increase levels of service over the majority of the length.

Sandbag Replacement

6.2          Due to the urgency of the works detailed design of the replacement of the sandbag sections has commenced. This works package also includes provide rock protection to a short section of the stopbanks exposed to undercutting due to vegetation die-off at Kibblewhite Street.

6.3          In some places consideration may need to be given to encroaching into the existing road footprint. This will need to be negotiated with Council's roading planners and with SCIRT. This is likely to be limited to small sections where the river is close to the road and a limited stable footprint is available for the stopbank.

6.4          A tight design timeframe has been agreed, with delivery of the detailed design scheduled for mid-May 2016. Construction is currently programmed to begin at the end of July 2016.

6.5          The construction for the replacement of the sandbags sections is expected to cost up to $1M. It is proposed to procure these works under existing delegations once a more detailed construction estimate is completed.

6.6          Seepage through the stopbanks is not unexpected and represents a low risk of failure. However, seepage will require some remedial works over time to reduce this where it is noticed to increase. Seepage control works are underway at Pump Station 204 (Waitaki Street) and it is expected that remedial works may be required to reduce seepage at other locations over time. Any replacement works or raising of the stopbank level will also consider this issue.

Raising Stopbank Levels

6.7          The risk assessment considered the risks due to overtopping for the 0.5%, 1% and 2% AEP events. This risk can be reduced through raising the crest level of the stopbanks.

6.8          To consider the levels required the stopbanks can be considered as three distinct sections (Figure 4):

·      Downstream, tidally dominated (from the estuary to upstream Avondale Road bridge or chainage[1] 14,500)

·      Middle section from upstream of Avondale Road bridge to just upstream of Porrit Park (chainage 12,100)

·      Upper section from Porrit Park to the end of the temporary stopbanks, just downstream of the western end of Retreat Road.

 

Figure 4 Temporary stopbank sections

6.9          The water levels throughout these sections change distinctly, as shown in Figure 5. The upper section has higher flood levels which reflect the increased gradient of the Avon River at that point, and the higher land level. The middle section has relatively flat flood levels and the required stopbank level is dominated by river flooding. Flood levels in the downstream section drop rapidly, and the 1% AEP tide with 300mm freeboard dictates the stopbank height.

Figure 5 Avon River sections

 

Downstream section (tidally influenced areas)

6.10       This section extends from the estuary up to chainage 14,500 (or just upstream of the Avondale Road bridge). Overtopping in this section is dominated by extreme tide events.

6.11       It is recommended that the stopbanks are maintained at the original design level of RL11.2 m. This will provide protection against overtopping for the 1% AEP tidal event (with 300 mm freeboard), and will still be higher than the 0.5% AEP design flood event (with freeboard decreasing with distance up the river).

6.12       The level of service provided by the temporary stopbanks will be less than that planned for the permanent stopbanks, which are likely to be constructed at least 400 mm above the 1% AEP floor or tide level with allowance for 1 m sea level rise (SLR). However, it is considered that the proposed level of service with a reduced freeboard and no allowance for SLR is acceptable within the design horizon of 20 years.

6.13       Raising the stopbanks to a constant RL11.2 m will require topping up the level of the stopbanks along parts of both banks of the river, although the majority of the stopbanks currently meets this design level.

6.14       Some work to sections with oversteep batters may also be required, and this section also includes some sandbag sections which will be replaced in the early works.

6.15       The preliminary rough order construction cost estimate to raise the downstream section to RL11.2 m is $0.5M. This is based on the material costs and costs to place the materials without any geotechnical or physical constraints. The final construction cost may be up to three times this amount, or $1.5M.

Middle section (from Avondale Road bridge to just upstream of Porrit Park)

6.16       This section extends from chainage 14,500 up to chainage 12,100 (or from Avondale Road bridge to just upstream of Porrit Park).

6.17       In this section the tidal influence decreases and the water level for the 0.5% AEP design flood event is above RL11.2 m (CDD) (although the 1% and 2% AEP events remain below this level).

6.18       Overtopping in this section represents the highest risk due to the number of green zone properties exposed to flood risk.

6.19       It is considered feasible to raise the stopbanks in this section to RL11.3 m which is approximately 50 mm above the 0.5% AEP flood level, approximately 150 mm above the 1% AEP flood level, and approximately 250 mm above the 2% AEP flood level.

6.20       While this does not provide the level of protection proposed for the permanent stopbanks (1% AEP flood plus 400 mm), it is considered this is sufficient for the maximum 20 year timeframe being considered for the temporary stopbanks.

6.21       Raising the stopbanks to this level will reduce the societal and individual risks identified in the risk assessment to below the limit of tolerability for existing structures (although without the standard freeboard normally adopted in stopbank design).

6.22       Some work to sections with oversteep batters may also be required, and this section also includes some sandbag sections which will be replaced in the early works.

6.23       The preliminary rough order construction cost estimate to raise the downstream section to RL11.3 m is $0.4M. This is based on the material costs and costs to place the materials without any geotechnical or physical constraints. The final construction cost may be up to three times this amount, or $1.2M.

Upper section (from Porrit Park to the end of the stopbanks)

6.24       This section extends from chainage 12,100 (upstream of Porrit Park) to the end of the stopbanks (upstream of North Avon Road).

6.25       Initial review of the modelling data shows that stopbanks in this area only protect unoccupied RRZ property, and that there are no green zone properties or occupied red zone properties at risk of flooding above the floor level as a result of overtopping. Overland flow paths do not appear to exist between the RRZ and the green zone ensuring that flood waters will remain in the RRZ.

6.26       Figure 6 shows the extents of the RL11.2 m water level (assuming that water can freely flow with no restriction to these locations, commonly referred to as a 'bathtub' model). This shows that in the middle and downstream sections there are substantial areas of occupied properties which would be affected if the stopbanks failed and the water reached that level (or higher). However, in the upper section there are no occupied properties at risk of flooding above the floor level, even in a 1% AEP event. This is higher than the level of service provided in many other parts of the city.

Figure 6 Avon River sections and inundated properties at RL11.2 m

 

6.27       In the upper section the flood levels also start to rise significantly above the original design level of RL11.2 m. At the upper limit of the temporary stopbanks the 0.5% AEP flood level is approximately RL11.7 m, and works to increase the height of the stopbanks to provide that level of flood protection would be significant.

6.28       Furthermore, upstream of the upper extent of the temporary stopbanks there are properties at risk of inundation from flood events that have no stopbank protection. This is common throughout the city in the older residential areas. Protection for the properties upstream of the current temporary stopbanks will be considered under the separate downstream rivers and tidal flood protection LDRP project, but this is considered outside the scope of the temporary stopbanks project.

6.29       Based on this analysis it is not proposed to raise the stopbanks in the upper area as it is not subject to the same risks as the middle section. This will result in no increase (or decrease) in the level of service currently offered. However, there are two caveats to this which will be confirmed during detailed design:

·      A check needs to be made to determine if any occupied red zone properties in this area will be at risk of flooding above the floor level in a 2% AEP event; and

·      Overland flow paths need to be rigorously scrutinised to confirm that there are no flow paths between this area and the green zone.

6.30       If the investigations identify that either of these situations present a risk then the decision not to raise the level of the stopbanks in this area will be reviewed.

6.31       The cost of the maintenance of this section at existing levels has not been quantified. The costs will either be included in the operational budget, or will be required when reactive strengthening capital works is identified.

Significance

6.32       The level of significance of this option is low consistent with section 2 of this report.  Engagement requirements for this level of significance are to inform the community of the works.

6.33       The Community Board has been informed of the findings of the condition assessment and risk analysis and will be further informed about the preferred option and design process at the next board meeting.

Impact on Mana Whenua

6.34       This option does not involve a significant decision in relation to ancestral land or a body of water or other elements of intrinsic value, therefore this decision does not specifically impact Ngāi Tahu, their culture and traditions.

Community Views and Preferences

6.35       There is an interest in the condition and management of the temporary stopbanks in some sectors in the community, and the media have also requested information recently. From these interactions it is understood that the community wants to be assured that the stopbanks are fit for purpose, and that there is a preference for an increased level of maintenance of the stopbanks.

6.36       The LDRP presented the findings of the Temporary Stopbanks Report to the Burwood-Pegasus Community Board on 4 April 2016. At this point the preferred option had not been confirmed with the Programme Control Group and so was not presented to the Board. A memo on this option will be prepared and circulated to the Board to seek feedback, and a request made for time to present this option to the Board on 16 May 2016.

6.37       Community views and preferences have not been specifically canvassed for this option other than engagement with the Community Board and through enquiries from the community to the project team.

Alignment with Council Plans and Policies

6.38       This option is consistent with Council’s Plans and Policies.

Financial Implications

6.39       Cost of Implementation - The current estimate is for detailed design and construction costs to be up to $4M. This is dependent on the ground conditions encountered, and the ability to utilise parts of the road corridor where the separation between the river and the road is minimal.

6.40       Maintenance / Ongoing Costs - Maintenance costs for the stopbank will not be materially affected over the life of the asset as the proposed option does not result in the construction of a new asset. However, if the temporary stopbanks are to be a longer term feature of the riverside then a more intensive maintenance programme may be required.

6.41       Funding source - The Long Term Plan has funding allocated to the Land Drainage Recovery Programme.  Within the budget for next financial year (2016/17) there is sufficient provision to enact the works.  The construction of the original temporary stopbanks was supported through the cost share agreement with central Government. HIGG approval will be required to support cost share funding of replacement of the sandbag sections and raising the level along parts of the stopbanks.

Legal Implications

6.42       A detailed consenting analysis will be undertaken during the next design stage but initial investigations have identified that the proposed works may be consistent with conditions of specific and/or global consents already held by Council.

6.43       If partial road closures are necessary (to allow for economical construction of portions of the stopbank) then approvals will be required.

Risks and Mitigations

6.44       Costs will be re-estimated during the detailed design stage.  The detailed design cost estimates may vary from the current cost estimates.

6.45       Evaluation of tree removals has not occurred at this stage.  Tree surveys and arborist reports have been commissioned and tree removals may be identified.  Any removals will follow standard Council approvals processes, though this will primarily occur for trees within the current stopbank which are dead or dying.

6.46       The temporary stopbanks are not designed to prevent groundwater flow from the river into the surrounding land, and this will continue to be an issue in some of the downstream areas.  

Implementation

6.47       Implementation dependencies - There are no particular dependencies that have been identified that could delay the project.

6.48       Implementation timeframe - Detailed design for the sandbag replacement is scheduled for completion mid-May 2016, with completion expected by the end of December 2016. Detailed design for raising the stopbank levels is currently programmed for completion by the end of September 2016 with completion of physical works by the end of next financial year (mid 2017).

Option Summary - Advantages and Disadvantages

6.49       The advantages of this option include:

·      Increased level of service provided along the majority of the temporary stopbanks

·      Reduced risk of failure

·      Greater certainty for residents about the level of protection provided

6.50       The disadvantages of this option include:

·      No increase in level of service provided to a small area of residential red zone

·      Higher cost than maintaining current level of service

7.       Option 2 - Maintenance of existing design level of service

Option Description

7.1          Rather than increasing the level of service in the middle section this option is to maintain the level of the stopbanks at the original design RL of 11.2 m in the middle and upper sections. No change is proposed to the current levels in the upper section.

7.2          This option also requires the replacement of the sandbag sections with more robust materials as per Option 1. The cost estimate remains similar with a cost of up to $1M.

7.3          The cost for this option in the downstream section is the same as for Option 1 which is $1.5M.

7.4          The middle section, rather than being raised to RL11.3 m, would be increased to only RL11.2 m. This would not reduce the societal and individual risk to the same level, with the level of risk likely to remain above the limit of tolerability for existing structures under the ANCOLD guidelines.

7.5          The cost for raising the low portions of the middle section to RL11.2 m is estimated at $0.5M, compared to the estimate of $1.2M for raising the stopbanks to RL11.3 m.

Significance

7.6          The level of significance of this option is low consistent with section 2 of this report.  Engagement requirements for this level of significance are to inform the community of the works as there is no reduction in the level of service.

7.7          The Community Board has been informed of the findings of the condition assessment and risk analysis and will be further informed about this option and design process at the next board meeting.

Impact on Mana Whenua

7.8          This option does not involve a significant decision in relation to ancestral land or a body of water or other elements of intrinsic value, therefore this decision does not specifically impact Ngāi Tahu, their culture and traditions.

Community Views and Preferences

7.9          There is an interest in the condition and management of the temporary stopbanks in some sectors in the community, and the media have also requested information recently. From these interactions it is understood that the community wants to be assured that the stopbanks are fit for purpose.

7.10       In general there appears to be a preference for an increased level of maintenance of the stopbanks and this option may not meet community expectations when tolerable risk limits are explained.

7.11       The LDRP presented the findings of the Temporary Stopbanks Report to the Burwood-Pegasus Community Board on 4 April 2016. At this point this option was not presented to the Board. A memo on this option will be prepared and circulated to the Board to seek feedback, and a request made for time to present this option to the Board on 16 May 2016.

7.12       Community views and preferences have not been specifically canvassed for this option other than engagement with the Community Board and through enquiries from the community to the project team.

Alignment with Council Plans and Policies

7.13       This option is consistent with Council’s Plans and Policies, although the impact on the level of service has not been specifically calculated.

Financial Implications

7.14       The current estimate for detailed design and construction costs for this option is up to $3M. This is dependent on the ground conditions encountered, and the ability to utilise parts of the road corridor where the separation between the river and the road is minimal.

7.15       Maintenance / Ongoing Costs - Maintenance costs for the stopbank will not be materially affected over the life of the asset as the proposed option does not result in the construction of a new asset. However, if the temporary stopbanks are to be a longer term feature of the riverside then a more intensive maintenance programme may be required.

7.16       Funding source - The Long Term Plan has funding allocated to the Land Drainage Recovery Programme.  Within the budget for next financial year (2016/17) there is sufficient provision to enact the works.  The construction of the original temporary stopbanks was supported through the cost share agreement with central Government. HIGG approval will be required to support cost share funding of replacement of the sandbag sections and raising the level along parts of the stopbanks.

Legal Implications

7.17       A detailed consenting analysis will be undertaken during the next design stage but initial investigations have identified that the proposed works may be consistent with conditions of specific and/or global consents already held by Council.

7.18       If partial road closures are necessary (to allow for economical construction of portions of the stopbank) then approvals will be required.

Risks and Mitigations

7.19       Costs will be re-estimated during the detailed design stage.  The detailed design cost estimates may vary from the current cost estimates.

7.20       Evaluation of tree removals has not occurred at this stage.  Tree surveys and arborist reports have been commissioned and tree removals may be identified.  Any removals will follow standard Council approvals processes, though this will primarily occur for trees within the current stopbank which are dead or dying.

7.21       There is a risk that the community will not accept this level or service. However, it represents a maintenance or improvement over the existing levels of service.

Implementation

7.22       Implementation dependencies - There are no particular dependencies that have been identified that could delay the project.

7.23       Implementation timeframe - Detailed design for the sandbag replacement is scheduled for completion mid-May 2016, with completion expected by the end of December 2016. Detailed design for raising the stopbank levels is currently programmed for completion by the end of September 2016 with completion of physical works by the end of next financial year (mid 2017).

Option Summary - Advantages and Disadvantages

7.24       The advantages of this option include:

·      Reduced cost (up to $1M saving) over Option 1.

·      Potentially less disruption due to lower design levels in the middle section.

7.25       The disadvantages of this option include:

·      Reduced level of service over Option 1.

·      The level of risk which remains is above that deemed tolerable for existing structures under the ANCOLD guidelines.

8.       Option 3 - Do minimum

Option Description

8.1          This option only allows for the replacement of the sandbag sections with more robust materials as per Option 1. The cost estimate remains similar with a cost of up to $1M.

8.2          No change in levels will be made to the upper, middle or downstream sections except where structural instabilities are identified.

Significance

8.3          The level of significance of this option is low consistent with section 2 of this report.  Engagement requirements for this level of significance are to inform the community of the works as there is no reduction in the level of service.

8.4          The Community Board has been informed of the findings of the condition assessment and risk analysis and will be further informed about the range of options and proposed design process at the next board meeting.

Impact on Mana Whenua

8.5          This option does not involve a significant decision in relation to ancestral land or a body of water or other elements of intrinsic value, therefore this decision does not specifically impact Ngāi Tahu, their culture and traditions.

Community Views and Preferences

8.6          There is an interest in the condition and management of the temporary stopbanks in some sectors in the community, and the media have also requested information recently. From these interactions it is understood that the community wants to be assured that the stopbanks are fit for purpose.

8.7          In general there appears to be a preference for an increased level of maintenance of the stopbanks and this option may not meet community expectations when tolerable risk limits are explained.

8.8          The LDRP presented the findings of the Temporary Stopbanks Report to the Burwood-Pegasus Community Board on 4 April 2016. At this point this option was not presented to the Board. A memo on this option will be prepared and circulated to the Board to seek feedback, and a request made for time to present this option to the Board on 16 May 2016.

8.9          Community views and preferences have not been specifically canvassed for this option other than engagement with the Community Board and through enquiries from the community to the project team.

Alignment with Council Plans and Policies

8.10       This option is consistent with Council’s Plans and Policies, although the impact on the level of service has not been specifically calculated. It does not represent a reduction in existing levels of service.

Financial Implications

8.11       The current estimate for detailed design and construction costs for this option is up to $1M. This is dependent on the ground conditions encountered, and the ability to utilise parts of the road corridor where the separation between the river and the road is minimal.

8.12       Maintenance / Ongoing Costs - Maintenance costs for the stopbank will not be materially affected over the life of the asset as the proposed option does not result in the construction of a new asset. However, if the temporary stopbanks are to be a longer term feature of the riverside then a more intensive maintenance programme may be required.

8.13       Funding source - The Long Term Plan has funding allocated to the Land Drainage Recovery Programme.  Within the budget for next financial year (2016/17) there is sufficient provision to enact the works.  The construction of the original temporary stopbanks was supported through the cost share agreement with central Government. HIGG approval will be required to support cost share funding of replacement of the sandbag sections and raising the level along parts of the stopbanks.

Legal Implications

8.14       A detailed consenting analysis will be undertaken during the next design stage but initial investigations have identified that the proposed works may be consistent with conditions of specific and/or global consents already held by Council.

8.15       If partial road closures are necessary (to allow for economical construction of portions of the stopbank) then approvals will be required.

Risks and Mitigations

8.16       Costs will be re-estimated during the detailed design stage.  The detailed design cost estimates may vary from the current cost estimates.

8.17       Evaluation of tree removals has not occurred at this stage.  Tree surveys and arborist reports have been commissioned and tree removals may be identified.  Any removals will follow standard Council approvals processes, though this will primarily occur for trees within the current stopbank which are dead or dying.

8.18       There is a risk that the community will not accept this level or service. However, it represents a maintenance or improvement over the existing levels of service.

Implementation

8.19       Implementation dependencies - There are no particular dependencies that have been identified that could delay the project.

8.20       Implementation timeframe - Detailed design for the sandbag replacement is scheduled for completion mid-May 2016, with completion expected by the end of December 2016. Detailed design for raising the stopbank levels is currently programmed for completion by the end of September 2016 with completion of physical works by the end of next financial year (mid 2017).

Option Summary - Advantages and Disadvantages

8.21       The advantages of this option include:

·      Reduced cost (up to $3M saving) over Option 1.

·      Less construction disruption.

8.22       The disadvantages of this option include:

·      Reduced level of service over Option 1.

·      The level of risk which remains is above that deemed tolerable for existing structures under the ANCOLD guidelines.

·      Reduced level of community confidence in the temporary stopbanks for a 20 year design life.


 

 

Attachments

There are no attachments to this report.

 

Confirmation of Statutory Compliance

Compliance with Statutory Decision-making Requirements (ss 76 - 81 Local Government Act 2002).

(a) This report contains:

(i)  sufficient information about all reasonably practicable options identified and assessed in terms of their advantages and disadvantages; and

(ii) adequate consideration of the views and preferences of affected and interested persons bearing in mind any proposed or previous community engagement.

(b) The information reflects the level of significance of the matters covered by the report, as determined in accordance with the Council's significance and engagement policy.

 

Signatories

Author

Peter Christensen

Senior Water Resources Engineer

Approved By

Keith Davison

Peter Langbein

John Mackie

David Adamson

Unit Manager - Storm Water & Land Drainage Rebuild

Finance Business Partner

Head of Three Waters & Waste

General Manager City Services

 

 

 

  


Council

12 May 2016

 

 

57.  Resolution to Exclude the Public

Section 48, Local Government Official Information and Meetings Act 1987.

 

I move that the public be excluded from the following parts of the proceedings of this meeting, namely items listed overleaf.

 

Reason for passing this resolution: good reason to withhold exists under section 7.

Specific grounds under section 48(1) for the passing of this resolution: Section 48(1)(a)

 

Note

 

Section 48(4) of the Local Government Official Information and Meetings Act 1987 provides as follows:

 

“(4)     Every resolution to exclude the public shall be put at a time when the meeting is open to the public, and the text of that resolution (or copies thereof):

 

             (a)       Shall be available to any member of the public who is present; and

             (b)       Shall form part of the minutes of the local authority.”

 

This resolution is made in reliance on Section 48(1)(a) of the Local Government Official Information and Meetings Act 1987 and the particular interest or interests protected by Section 6 or Section 7 of that Act which would be prejudiced by the holding of the whole or relevant part of the proceedings of the meeting in public are as follows:


Council

12 May 2016

 

 

ITEM NO.

GENERAL SUBJECT OF EACH MATTER TO BE CONSIDERED

SECTION

SUBCLAUSE AND REASON UNDER THE ACT

PLAIN ENGLISH REASON

WHEN REPORTS CAN BE RELEASED

58

Community Capital Delivery Unit: Bruce Terrace Cottages (Akaroa) Social Housing Complex Rebuild

s7(2)(b)(ii)

Prejudice Commercial Position

Would prejudice commercial position prior to tendering activities.

14 April 2017

 

 



[1] Chainage refers to measurements of the length (in metres) of the river and is used to identify locations in the hydraulic models and for surveying purposes.