A GIS-Based Decision Support System for Optimal Renewal Planning of Sewers

1. A GIS-Based Decision Support System for Optimal Renewal Planning of Sewers Mahmoud Halfawy, Leila Dridi, & Samar Baker NRC-Centre for Sustainable Infrastructure Research INFRA 2007 5-7 November 2007 Québec

2. Background • Fragmentation of sewer management data and processes. • Need for proactive and optimized renewal planning. • State-of-practice in sewer management software. • Challenges for integrating sewer management data, processes, and software systems.

3. NRC-CSIR Integrated Asset Management Project • Objective: • Develop consistent/generalized models and protocols for asset management process systematization and data integration – Bridging the vertical (departmental) and horizontal (cross-disciplinary) gaps. • Develop algorithms and a set of interoperable GIS-based decision support tools for optimizing and coordinating asset management plans for water, sewer, and road networks. • Project Partners: City of Regina.

4. Condition Assessment Condition Assessment Condition Assessment Inspection/Monitoring Inspection/Monitoring Maintenance Mgt Risk Assessment Risk Assessment Risk Assessment Deterioration Modeling Deterioration Modeling Deterioration Modeling Performance Modeling Performance Modeling Performance Modeling Asset Prioritization Asset Prioritization Asset Prioritization Rehab Methods Rehab Methods Rehab Methods Renewal Planning Renewal Planning Renewal Planning Integration of Municipal Asset Mgt Processes Vertical Integration Horizontal Integration Optimized & Coordinated Plans

5. Prepare Asset Data Repository Year = 1 Define planning horizon Calculate condition index Calculate risk index Specify budget scenario Calculate prioritization ranking Specify condition/risk minimum requirements Select feasible rehabilitation options Specify option criteria & run MOO & calculate Pareto fronts Apply Delta Tables Revise budget scenario and/or condition/risk requirements Select a satisfying solution Year = Year + 1 Solution found? Print Renewal plan for one scenario no no yes Year = horizon? yes End Create Delta Tables The Renewal Planning Step-Wise Algorithm

6. Intranet/ Extranet Sewer Management Stakeholders GIS and Data Management Services Spatial and Inventory Data Inspection and Condition Data Integrated Asset Data Repository Financial/Cost Data Performance Data Maintenance and rehabilitation Data Simulation Models/Results Work Order and Operational Data Deterioration/Life cycle cost Data References to other databases (ERP, CIS, SCADA, etc.) Data and Process Integration Using Centralized Shared Repositories

7. Part of the UML class diagram for the integrated sewer data model

8. Renewal Planning Algorithm Implementation • Define an integrated data model and build asset data repository (inventory, hydraulic data, condition data, repair/incidence records, risk parameters, cost data, service levels, etc.). • Define an integrated condition rating index. • Define /calibrating deterioration curves. • Define risk assessment model. • Define asset prioritization criteria. • Define renewal technologies database, and algorithm for selecting feasible options. • Define a multi-objective optimization (MOO) algorithm (maximize condition, minimize risk, and minimize budget).

13. Sanitary sewers and Vitrified Clay (2881 records) Sanitary sewers and pipe condition = 3 (823 records)

14. Deterioration Modeling • Largely depends on the quantity and quality of available condition data. • May use deterministic or probabilistic models • Employs many different techniques: regression analysis, Markov processes, ANN, fuzzy models, etc. • Our approach: • Store a library of known or previously calibrated models • If a sewer or a group has sufficient data to do regression analysis, define a new model or calibrate an existing model. • If data is not enough, assist user to select a “suitable” model based on his/her intuition/experience with the system and the data available. • As more data become available, the models can be re-defined or re-calibrated.

16. Condition, Risk & Prioritization Analysis Tool

17. Risk Assessment & Prioritization Models • Risk = Consequence of Failure * Probability of Failure • Criticality factors affecting consequence of failure: • Sewer type, diameter, depth, embedment soil, land use, road classification, traffic volume, proximity to critical assets, socio-economic impact, site seismicity, etc. • Procedure: • Calculate a Risk Factor (1-5 scale) that reflects the consequence of failure using a weighted average equation. • Calculate the likelihood of failure index (LFI) for the sewer, based on its current age and expected service life. • Risk Index = RF * LFI • Prioritization ranks sewers based on their “priority index” (1-5 scale) to select candidates for renewal. • Priority index is derived from the condition index and risk indices according to a set of user-defined rules.

18. Renewal Methods Selection Tool • Applicability criteria for method selection: • Sewer characteristics (diameter, material, depth, type: gravity or pressure, structural condition state, hydraulic capacity, etc.) • Method characteristics (renewal type (NS/SS/FS), limitations, site and installation requirements) • Site characteristics (soil type, traffic, water table, etc.) • Cost vs. Condition Improvement: • Expected condition improvement • Technology construction cost • Technology overall cost (socio-economic cost) • Expected operational cost after improvement

19. Renewal Technologies Fully Structural Semi-Structural Rehabilitation - Lining Replacement Non-Structural Off-Line In-Line Sliplining Open-Cut(Dig) CIPP Horizontal Directional Drilling (HDD) Close fit pipe Pipe Bursting Pipe Jacking Formed in place Pipe Removal Micro-Tunelling Thermoformed Auger Boring Spiral wound Panel lining UCL Renewal Methods Selection Tool (Cont.)

21. GA-Based Multi-Objective Optimization Tool • Trade-offs of the renewal costs vs. network condition and risk improvements. • Three objective functions for cost, condition, and risk. • Solution using the NSGA II algorithm and the Open Beagle class library. • Calculate 2 Pareto fronts for condition-cost and risk-cost criteria. • Evaluate feasible solutions and select or synthesize a solution.

23. Conclusions & Future Work • Integrated approaches and DSSs are critical for supporting proactive asset management strategies. • The proposed approach and software prototype provided promising results. • Work is ongoing to refine/improve several models employed in the prototype, and to validate the software with more data sets. These activities are conducted in collaboration with the City of Regina as well as other industry partners. • The software modular architecture facilitated incremental development and testing, and would also facilitate future extensions, refinement, and interoperability with other (e.g. legacy) software systems. • Need to define an industry-wide agenda for developing and adopting open/standard integrated data & process models, and software architectures.