OPTIMISATION OF THE CHRISTCHURCH WASTEWATER NETWORK USING RISK BASED COST REDUCTION STRATEGIES

Transcription

1 OPTIMISATION OF THE CHRISTCHURCH WASTEWATER NETWORK USING RISK BASED COST REDUCTION STRATEGIES

2 Acknowledgement David Heiler Mark Groves Chris Mance

3 Map of Events

4 Legend Repairs > $100k (houses which had significant damage but could be economically repaired! Rebuilds (houses which are beyond economic repair) Confirmed rebuilds (houses which were confirmed to be beyond economic repair) Approx Scale 1:50, (m) Notes: Low-resolution aerial photos sourced from Google Earth (Copyright: 2009). High-resolution aerials provided by New Zealand Aerial Mapping (February 2011) Property boundaries provided by Christchurch City Council Building damage based on data provided by AMI, Ansvar, EQC, FMG, Housing New Zealand, IAG, Lumley, MAS, Tower and Vero Canterbury Earthquake Recovery Authority DRAWN DRAFTING CHECKED APPROVED FILE :. APPROX. SCALE (AT A3 SIZE) NTS PROJECT No. FIG. No. CERA CANTERBURY EARTHQUAKE RECOVERY Aggregated Building Damage Map Building Damage After 4 September 2010 REV. 0

5 Legend Building Damage Ratio (Repair cost estimate / replacement cost)! 0% - 20% 20% - 40% 40% - 60% 60% - 80% 80% - 100% 100% (rebuild because it is uneconomic to repair the building) Approx Scale 1:50, (m) Notes: Low-resolution aerial photos sourced from Google Earth (Copyright: 2009). High-resolution aerials provided by New Zealand Aerial Mapping (February 2011) Property boundaries provided by Christchurch City Council Building damage based on data provided by AMI, Ansvar, EQC, FMG, Housing New Zealand, IAG, Lumley, MAS, Tower and Vero Canterbury Earthquake Recovery Authority DRAWN DRAFTING CHECKED APPROVED FILE :. APPROX. SCALE (AT A3 SIZE) NTS PROJECT No. FIG. No. CERA CANTERBURY EARTHQUAKE RECOVERY Aggregated Building Damage Map Aggregated Building Damage After 22 February 2011 REV. 0

6

7 Post Earthquake Situation Damage unprecedented in NZ Rapid response to underpin the recovery Clients did not have resources available No single Design or Construction provider could cope Ongoing uncertainty, and associated risk

8 SCIRT MODEL Relationship contract Mix of public and private organisations Programme of projects Performance incentivised Competitive delivery Collaborative environment

9

10 CHALLENGES AHEAD Achieving the Target Estimate ( Whole Of Network level of service, asset life and running costs) Demonstrate Value differing viewpoints Focus on critical resources Contain escalation Balance work schedule to maintain operational networks Integrate with other rebuild programmes

11 CHALLENGES The Right Work Definition of scope & standards Many work fronts Risk management

12 ASSET ASSESSMENT CCTV vital but expensive 2,000km of pipe

13 CCTV Examples

14 Alternative / Supplement Pipe Damage Assessment Tool Geospatial Statistical Optimisation Input into decisions on: Asset assessment scheduling CCTV Estimating and budgets Project prioritisation Project scoping Concept and detailed design

15 Damage Indicators Material Proximity to Watercourse Sub-catchment Road Damage Depth Diameter Direction Liquefaction Resistance Index

16 Summarised Damage Indicated

17 COST SAVING OPPORTUNITIES Network Performance Working Group

18 Background What we know EQ s have significantly increased I&I - in particular base flow conditions. Potentially increased overflow volumes Increased flow arriving at WwTP Operational costs have increased to deal with the exacerbated flows Pdat is predicting less damage in North and Western catchments

19 Opportunity areas for discussion Do we need to rehabilitate all pipes? What is the benefit in terms of level of service? Can we rationalise CCTV activity around risk? Can we offset rehabilitation works in the North and Western catchments if the net I&I reduction is offset by improvement in the Central and Eastern catchments? Assess the most cost effective technology in terms of net I&I reduction Provide an improved level of service in terms of overflow / WwTP performance using targeted rehab rather than broad brush methods

20 Methodology Phase 1 Data review and identify opportunities Phase 2 Use hydraulic models to: Assess pre and post EQ overflow performance Assess effect of pre and post EQ I&I on wastewater infrastructure Assess likely I&I reduction in scoped areas Define economic level of I&I removal to meet LOS requirements Review alternative option to meet LOS requirements Compare performance of wastewater network against consent requirements

21 Analysis Post EQ Water Table / Pipe Invert comparison

22 Analysis CCL Ongoing Maintenance costs (post EQ)

23 Analysis Lateral repairs post EQ

24 Analysis Comparison of Infiltration (pre and post EQ) - %age

25 Analysis Comparison of Infiltration (pre and post EQ) - Absolute

26 Analysis Catchment risk (opportunity)

27 Initial Conclusions from I&I Review There are definite areas of opportunity where I&I has not increased and pipes are above groundwater There are areas where ongoing maintenance costs are negligible The data supports that lateral issues are evident where pipes are under the ground water table >80% of laterals must be addressed in these areas to successfully remove I&I Is this cost effective? The hydraulic model must be developed to test the most economic level of I&I removal to meet level of service requirements.

28

29

30 Confirm proposed savings for: Total - $83M WW - $80M RD - $3M SW - $0.2M WS - $0M Total - $91M WW - $86M RD - $1.2M SW - $0.1M WS - $1.3M Total - $76M WW - $71.5M RD - $4M SW - $0.2M WS - $0.5M

31 Next Steps

32 Questions?