Mark Shepherd PrEng Consultant to ethekwini Water and Sanitation Durban, South Africa

Transcription

1 Mark Shepherd PrEng Consultant to ethekwini Water and Sanitation Durban, South Africa

2 Does Mains Replacement Always Reduce Real Losses? Results and Lessons Learned from a Largescale Mains Replacement Program in Durban

3 ethekwini Quick Stats 3,6 million people properties Supply 845 Ml/day of water from 9 Treatment Works Treat 500 Ml/day of Waste Water 263 Water Reservoirs 27 Waste Water Treatment Works km of sewer mains km of water mains water connections

4 Non-Revenue Water by Volume (%) Key Performance Indicator Trends 45.0% ethekwini Municipality Non-Revenue Water and Inefficiency of Use Trends 40.0% 35.0% 31.8% 33.4% 36.4% 38.9% 37.5% 33.2% 35.4% 37.6% 30.0% 25.0% 29.0% 22.1% 24.9% 25.8% 23.9% 26.9% 27.6% 20.0% 19.1% 19.0% 19.2% 15.0% 10.0% 5.0% 0.0% 2004/ / / / / / / / /13 Q2 Fi46 NRW by Volume (%) WR1 Inefficiency of Use (%)

5 Key Performance Indicator Trends

6 Key Performance Indicator Trends

7 NRW Program Implementation The ethekwini Municipality has been undertaking a large-scale Non-Revenue Water reduction program since 2007 through two parallel initiatives: the targeted replacement of small diameter undipped Asbestos Cement (AC) pipes; real loss reduction interventions coupled with apparent loss reduction/billing improvement interventions

8 NRW Program Implementation The distribution network (11 300km) comprises of pipe materials ranging from asbestos cement (undipped and dipped) and steel to plastic (upvc and mpvc) The ethekwini Municipality had identified undipped AC pipes as being problematic in terms of burst frequency and upon preliminary investigation determined that pipe end failure, typified by softening of pipe ends and delamination, was the primary cause

9 Why pipe replacement?

10 AC Pipe Delamination

11 AC Mains Replacement Program The majority of these failures took place on the smaller diameter reticulation pipes, so a program to replace all 100mm and 150mm diameter undipped AC mains was identified and commissioned in 2007 The ethekwini mains replacement program eventually replaced 1 370km of pipe (12% of the total network)

12 Extent of Pipe Replacement

13 Trial Hole Excavation

14 CCTV Inspection

15 Manual Excavation and Pipe Replacement

16 Pipe cracking

17 Real Loss Reduction Framework Speed and Quality of Repairs + Pressure Management Current Annual Volume of Real Losses Economic Level of Real Losses Unavoidable Annual Real Losses - Active Leakage Control - Pipeline Materials Management - +

18 Results of Mains Replacement

19 Results of Mains Replacement

20 Results of Mains Replacement

21 Results of Mains Replacement

22 Burst Frequency Analysis

23 Secondary Impacts DMA/Zone Number of Connections Analyzed Difference in Average Consumption (kl/day) Before and After Mains Rehabilitation Alverstone Nek Bluff South Chatsworth Emoyeni Knelsby Montille Phoenix Tongaat South Umlazi Totals

24 Decision Flow Chart (1)

25 Decision Flow Chart (2)

26 Preparatory Considerations (1) The Water Utility needs to recognize that as the water distribution infrastructure is in a continuous state of deterioration, the replacement of mains must an ongoing, continuous program Budget must be provided on a permanent basis to cover the cost of the annual mains replacement.

27 Preparatory Considerations (2) Systems must be put in place to gather and store system and performance data for future analysis. The deterioration rates of water mains must be tracked in order to predict replacement times. Staff must be trained to recognize the different types of water main faults and sensitize them to the importance of having accurate information in the faults database.

28 Preparatory Considerations (3) Analysis of the causes of failures must be undertaken and forwarded to the engineers and the procurement department in order to shape future mains replacement material selection and installation methodologies. Pressures in each DMA must be reduced as much as possible before mains replacement. Be aware that this reduction may improve the zone performances such that the replacement of the pipes is considerably deferred. The importance of the step cannot be overemphasized.

29 Preparatory Considerations (4) Minimize the real losses as much as possible through consecutive leak detection and repair exercises. Track the mains failures for at least three years prior to prioritizing areas for replacement and determine the Burst Frequency Index (BFI) for both mains and service connections.

30 Preparatory Considerations (5) Prioritized zones must be assessed and it must be proved beyond doubt that the prioritized area will yield significant results when rehabilitated. Conduct assessments to determine if it will be beneficial to replace service connections only as this can be done at a fraction of the cost of rehabilitating the reticulation mains.

31 Construction Considerations (1) Various contractual implementation vehicles should be investigated to derive the solution that best fits the objectives of the Water Utility. If not conducted in-house, turnkey contracts such as the New Engineering Contact (NEC) offer a number of advantages to tackling a programme of this nature.

32 Construction Considerations (2) Thoughtful consideration should be given to not only the type of material used (PVC, HDPE, Ductile Iron, etc) but also to the construction methodology used as each material and methodology can potentially offer significant benefits in terms of reducing construction times, reducing environmental impacts and pro

33 Construction Considerations (3) For areas where partial mains replacement occurs, ensure that the pressure across the entire supply area is managed in order to ensure that leakage levels are in fact reduced.

34 Construction Considerations (4) The mains replacement contractor must be made responsible for the performance of the new infrastructure and at hand over, various KPI s must be measured as part of the hand over process back to the Water Utility. Factors such as real loss, NRW, MNF, snapshot ILI, fire flow, average pressure, etc can be used for this purpose. The main driver for mains replacement contracts should never be just the length of mains replaced.

35 Construction Considerations (5) Coordinate with other service providers so as to rehabilitate all services at the same time where possible to limit future disturbances as these disturbances have the potential to damage or destabilize the existing services. Replace all service connections during the replacement of the water mains as these connections are often of a similar age to the distribution mains and statistically they account for 50% of the leakage.

36 Thank you!!