Efficient Capital Expenditure for Wastewater Systems

Transcription

1 Queensland Modelling Group (QMG) - Collection System Focus Group Efficient Capital Expenditure for Wastewater Systems From 5xADWF to Reality- Based Planning in Qld Assessment of dynamic modelling benefits Murrumba Downs Case Study Inflow and Infiltration Management Programs Presented by Joel Wilson 1

2 Part 1 Transitioning from 5xADWF to Reality-Based Planning in Qld Sydney Water Rational Approach 2

3 Overview 1. Snapshot of the QMG initiative 2. Brief history of 5xADWF design standard 3. Summary of standards in other regions 4. Challenges and benefits of transitioning from 5x 5. Role of:» EHP» Healthy Waterways» DEWS» Net Serve 6. QMG s proposed Road-Map to help improve standards of practice in Qld 3

4 Snapshot of QMG Initiative The current Standard in Queensland is inconsistent with other codes of practice in other states and countries. The industry is largely in support of transitioning from the current theoretical-based planning approach to a reality-based planning approach to enable more efficient capital expenditure on wastewater infrastructure This transition will require a framework that supports calibrated hydraulic modelling and helps operators to establish wet-weather overflow abatement targets based on affordability and location-specific environmental risks. The QMG plans to work with each operator to better understand specific challenges and objectives, coordinate with EHP, DEWS, HWW and WSAA to identify key environmental objectives, and ultimately to assist with developing improved planning guidelines and codes of practice. 4

5 Qld Guidelines 5

6 History of 5xADWF A Royal Commission on Sewage Disposal was appointed in the United Kingdom on 7 May The final report was submitted in February Some of the approaches to the hydraulic design of sewers and overflows in sewers and treatment plants, which are still used today, originated with this Royal Commission. 6

7 History of 5xADWF A paper by Howard Merrill Gifft (Professor at Cornell University, Ithaca) which was published in 1945 in the United States of America greatly influenced sewer design in Queensland. Gifft analysed previous work by Harmon (1918), Babbitt (1932), Metcalf & Eddy (1935), Stanley (1942), Johnson (1942), and Malcolm (1944). A dimensionless coefficient was applied to the average daily flow as a function of population. 7

8 History of 5xADWF 8

9 History of 5xADWF Gifft intended that his equations should be used for predicting minimum or maximum instantaneous flows during dry weather. In other words, flows above C = 5 would be the result of other sources of flow such as infiltration, illegal connections, and trade, institutional, and commercial waste water. The Queensland Government has published guidelines for designing sewers and treatment plants since the late 1950s. All of them used the Gifft Factor graph. 9

10 National Resource Management Ministerial Council (NRMMC) National Water Quality Management Strategy Guidelines for Sewerage System Overflows November 2004 Publication 10

11 NRMMC National Guidelines for Sewerage System Overflows The actual flows in the systems may be vastly different from the original design flows. The use of such tools as flow monitoring and hydraulic modelling should be used to assess the existing system's actual performance and to find the best improvement options When using hydraulic models of the system, it will need to be calibrated using flow-monitoring data 11

12 National Guidelines Summary Overflow Abatement Plan (OAP) should be a balance between community expectations, environmental protection and affordability Use of calibrated models is recommended Evaluation of alternatives is recommended (i.e. determine cost-effective balance of I/I source control, storage and conveyance/treatment amplification) (5xADWF is not compatible with any of above for an OAP) 12

13 Standards in Other Regions Sydney Water (uses calibrated models) Standard varied based on environ/social impacts and cost effectiveness, for example:» Sydney Harbour 1 in 6-month Average of two overflow events per year ( 2/year ) based on typical 10-year rainfall analysis (related to swimability high health risk)» Blue Mountains 1 in 5-year (because that was the standard already being achieved i.e. do no make worse)» Work done to correlate critical chloroform count at user locations to overflow volumes based on river-system water quality modeling 13

14 Standards in Other Regions Regional NSW (uses calibrated models) EPA major stakeholder to set standard based on environ/social impacts and cost effectiveness» Some regions set at 1 in 5-year because it was cost effective to fix current overflows at 4/year to achieve 1 in 5-year» Hunter Water at 4/year in some areas and 2/year in other areas with higher environmental sensitivity (based on 10-year rainfall data) 14

15 Standards in Other Regions Victoria (uses calibrated models) 1 in 5-year critical duration design storm Push to transition to risk-management based approach (Note that Vic 1 in 5-year event significantly different from Qld 1 in 5-year event) 15

16 Standards in Other Regions New Zealand (uses calibrated models) Target Level of Service (LOS) often a function of existing system performance and cost to achieve a particular LOS hence variability North Shore City - 4/year based on 17-year rainfall (determined based on knee-of-the-curve and community acceptance of beach closure frequency Queenstown 1 in 10-year 16

17 United States (uses Calibrated Models) Region/ Utility JCW, MO Springfield, MO Fort Worth, TX South Bend, IN San Francisco Standard 10-year, 24-hour duration design storm event 10-year, 24-hour duration design storm event 5-year, 6-hour duration design storm event 4 overflow events/year based on typical year continuous analysis No fixed standard Comment Sanitary Collection System EPA Consent Decree Sanitary Collection System EPA Consent Decree Sanitary Collection System EPA Consent Decree Combined System Determined based on knee-ofcurve, community affordability and negotiation with EPA SFPUC have avoided EPA consent decrees through being proactive with overflow management Chicago 1 in 5 year design storm Varies for different parts of system 17

18 Power and Water - Alice Springs Cairns Water and Waste (Cairns Regional Council) Water Corporation - Bunbury (sewerage) South East Water Ltd Yarra Valley Water Central Gippsland Water GWMWater Goulburn Valley Water Hunter Water Corporation Tweed Shire Council Water Corporation - Perth Barwon Water Albury City Council Wagga Wagga Council Sydney Water Corporation Water Corporation - Mandurah Queensland Urban Utilities Bathurst Regional Council Bega Valley Shire Council City West Water East Gippsland Water SA Water - Mount Gambier Unitywater Wide Bay Water City of Kalgoorlie-Boulder (sewerage) Dubbo City Council Shoalhaven City Council Ballina Shire Council Port Macquarie Hastings Council Queanbeyan City Council Wyong Shire Council Water Corporation - Albany Kempsey Shire Council SA Water - Adelaide Water Corporation - Geraldton Coffs Harbour City Council Lower Murray Water Western Water Coliban Water Westernport Water MidCoast Water Power and Water - Darwin Water and Waste Services (Mackay Regional Council) Essential Energy Goulburn Mulwaree Council Orange City Council Lismore City Council Gosford City Council ACTEW Wingecarribee Shire Council North East Water Eurobodalla Shire Council South Gippsland Water Melbourne Water Wannon Water Byron Shire Council Redlands Water Fitzroy River Water (Rockhampton Regional Council) Logan City Council Townsville Water (Townsville City Council) Gold Coast Water Overflows per 100 km Though GCW is almost up-to-date in delivering the infrastructures to manage growth, the number of overflows remains very high (source: WSAA NPR) No. of Sewer Overflows in FY 09/10 & 10/11 (per '00 km) Water Utility 18

19 Transitioning from 5xADWF to Reality-Based Planning What do we mean by reality-based planning? Calibrated models based on flow survey (or best available data) Establish wet-weather overflow abatement targets based on affordability and location-specific environmental risks 19

20 Transitioning from 5xADWF to Reality-Based Planning Challenges 1. Additional upfront cost to collect flow survey data and calibrate models 2. Additional complexity (dynamic modelling, long-term rainfall analysis, optimisation, etc.) 3. There is a lack of understanding and/or support from upper management and regulators to support change Benefits 1. Significant long-term cost savings and environmental benefits will be achieved 2. The Queensland industry will have a framework to implement engineering best-practice 3. Operators and regulators KPIs will improve significantly reduce customer complaints, reduce rates, improve water quality. 20

21 Cost Effective Control Level Optimised solution for each control level Improve environ outcome at same cost Do Both! Reduce cost for same environ outcome 5 x ADWF Solution 21

22 Justifying the business case for investing into calibration The next step in the QMG initiative was to use a case study to justify the investment into calibration. We often hear utility managers say, why should we invest hundreds of thousands into model calibration when we can follow the accepted 5xADWF guidelines with no additional upfront investment? 22

23 Part 2 Preliminary Assessment of Calibrated Model Benefits - Murrumba Downs Case Study (Unity Water) 23

24 Case Study Objective 1. Demonstrate the effective environmental performance of a 5xADWF planning solution by evaluating the performance of the 5x solution based on 10-year rainfall data and calibrated inflow and infiltration. 2. Use the resulting overflow volume and frequency from the 5xADWF solution to define the environmental performance objective for alternative solutions developed based on the calibrated model inflows 3. Demonstrate the magnitude of cost savings that can be achieved by using dynamic modelling to achieve the same environmental outcome as would be achieved with a 5x solution. 24

25 Methodology Overview 1. Model calibration Completed in Performance review of 5xADWF solution using calibrated model inflows and 10-year continuous rainfall a) Develop solution for xADWF b) Take the xADWF solution and replace the hydraulic loadings with that from the calibrated model c) Utilize 1997 to year rainfall data and run the 10-year continuous simulation to determine the frequency and volume of overflows occurring in the 5xADWF solution d) Create a system layout figure showing overflow frequencies and volumes 25

26 Methodology Overview 1. Model calibration Completed in Performance review of 5xADWF solution using calibrated model inflows and 10-year continuous rainfall 3. Develop alternative solutions to achieve similar performance to the 5xADWF solution (under 10-year continuous rainfall) 26

27 Murrumba Downs Case Study Unity Water Step 2a Develop Solution for Steady State 5xADWF xADWF Solution Gravity sewer improvements only Satisfy 1m freeboard Required augmentations shown in orange Total Cost = $ 9.8 M 27

28 Murrumba Downs Case Study Unity Water Step 2b Replace loadings with calibrated dry and wet weather flows and run 10-year continuous rainfall Overflows shown in red (size prop. to frequency) Total OF Vol = 14,700 kl Most of system has approx. 2 overflows in 10 years Highest frequency of 18 overflows in ten years Overall 5xADWF solution approx. 1 in 2-year to 1 in 5-year containment standard 28

29 Murrumba Downs Case Study Unity Water Step 3 Develop alternative solution to achieve similar performance to 5xADWF sol. Augmentations shown in blue Total OF Vol = 14,200 kl Most of system has approx. 2 overflows in 10 years Highest frequency of 3 overflows in ten years Overall solution approx. 1 in 3-year to 1 in 5-year containment standard Total Cost (gravity only) = $ 4.8 M 29

30 5xADWF Vs Calibrated Solutions Performance Measure 5xADWF Solution Reality-Based Solution Total 10-Year Overflow Volume 14,700 kl 14,200 kl No. Overflows 10 (1 per year) 1 0 No. Overflows 5 (1 in 2-year) 6 0 No. Overflows 3 (1 in 3-year) 0 3 No. Overflows 2 (1 in 5-year) Solution Cost (Gravity Only) $ 9.8 M $ 4.8 M Total Solution Cost* $ 20 M $10 M * Extrapolated trend assuming gravity cost is approximately 50% of total solution cost (based on past planning studies) Reality-Based Planning Cost savings > 50% (in the order of $10 M) Investment in upgrades to address actual system issues Improved environmental performance 30

31 Justifying the business case for investing into calibration The Murrumba Downs Case Study demonstrated a significant return on investment from model calibration Approx. Cost of Model Calibration = $ 0.2 M Approx. Savings = $10 M ROI = 50:1 to achieve similar (but slightly better) environmental performance when compared to the solution that would otherwise be developed using 5xADWF 31

32 Murrumba Downs Case Study Unity Water Review of existing system designed based on 5xADWF Orange lines show pipes with maximum depth during 1 in 2-year design event at less than 50% of pipe diameter (i.e. overdesigned) Approx. value of existing gravity sewers = $188 M Value of existing gravity sewers sized based on design flow = $156 M $30 M / 20% over investment 32

33 Part 3 Inflow and Infiltration Management Programs 33

34 2012 New Orleans WEF Conference Collection System Committee formed I/I Technical Group Typical drivers for rehab programs:» Structural Integrity» Avoided Capacity Utilisation» O&M Efficiency Key challenges:» Ranking asset criticality» Predicting flow reductions» Cost-effective expenditure 34

35 June 19, 2013 Workshop Significant interest in WEF membership and industry in gaining deeper knowledge of do s and don ts in implementing effective I/I management programs with verifiable results. [2014] workshop will build on the 2013 workshop by providing a series of case studies offering an indepth look at state-of-the-art methodologies, techniques and tools to achieve I/I removal through sewer rehabilitation and to verify the effectiveness of I/I removal 35

36 2004 Conference Max Anderson (MWH) et al Review of rehab work in Australia, New Zealand, Singapore and US Help managers set achievable targets many utilities enter the process on the expectation of reducing I/I to a considerable extent... the temptation is to over exaggerate the reductions that will be achieved by system rehabilitation. 36

37 The qualification with the relationship presented in Figure 5 is that the percentage of HSLs lined and the percentage of manholes sealed are not included. 37

38 Rehab has a high level of associated risk A high level of rehab and associated cost is necessary to achieve a small reduction in I/I Rehab is more effective if all components of the system are targeted Use the calibrated hydraulic model to simulate the benefits of RDII and use a combination of augmentation works to achieve the desired level of service The maximum expected level of reduction in RDII should not exceed 40% and only considered at these levels if 80% of the sewer mains, house service lines and manholes were to be rehabilitated Undertake a cost to benefit calculation on any planned rehabilitation projects 38

39 Rick Nelson (CH2M HILL) et al, 2010 Johnson County, Kansas - project completed in 2007 Comparison of cost per unit I/I removed for various sources Cost to benefit analysis of I/I removal, conveyance, storage and treatment alternatives 39

40 40

41 I/I (gal/acre/day) I/I rate vs. Meter basin area Level 1 03 Level 2 TC Level Level 4 08 Threshold for maximum removal 2,500 gpapd Cumulative Area (Acres) Threshold of maximum removal Leaky catchments could achieve 80% reduction Catchments with low I/I may only achieve 5% reduction North Shore City (NZ), demonstrated that the threshold of maximum removal changes depending on existing conditions 41

42 2009 Water NZ Conference Nick Brown (NSCC) et al Based on pre- and post-rehab data collected over a 10-year period (1999 to 2009) Continuation of early work done by Sydney Water to address outstanding issues with I/I data Consistent approach and methodology used to determine: 1. By how much will rehabilitation reduce the I/I? 2. What confidence can we have that the proposed rehabilitation works will reduce I/I to our performance target? 42

43 Data collected for 32 gauged catchments University of Auckland assisted with the statistical analysis of data Rehabilitation targeted both private and public assets Reliable results only achieved when 100% of target area was relined (i.e. source migration observed when spot repairs undertaken) Consistent antecedent conditions, network configuration, population, etc. helped to minimise bias. 43

44 Public and Private Rehabilitation Scenario 44

45 Public Only Rehabilitation Scenario 45

46 Challenge for Qld Utilities Should utilities address private sector I/I sources (e.g. illegal connections and private lateral defects) before calibrating hydraulic models? 46

47 Challenge for Qld Utilities Should utilities address private sector I/I sources (e.g. illegal connections and private lateral defects) before calibrating hydraulic models? - On one hand, if the property owner is willing to pay the cost of the private rehab then perhaps it is a near-free win. - And why calibrate the model if the inflows are only going to change due to I/I removal 47

48 Challenge for Qld Utilities What would your I/I strategy look like if you developed it based on the calibrated model compared with developing the I/I strategy without any information about actual system deficiencies? 48

49 Challenge for Qld Utilities To what extent will the private rehab improve the system and over what time frame? Will it address the major deficiencies in the system? What will be used to make planning decisions while model calibration is further delayed? 49