A multi-criteria approach for asset management of waste water networks

1. A multi-criteria approach for asset management of waste water networks D2-Decision Deck project Workshop, March 8-9, 2007 , University of Luxembourg. Amir NAFI, Caty WEREY Joint Unit Research in Water Utilities Management Cemagref-Engees 1 quai Koch 67070 Strasbourg, France.

2. Context Data Encodage REREAU Proposition Conclusion Context 152 sewerage utilities Joint international conference on computing and decision making in civil and building engineering - june 14-16 2006 - Montreal

3. Data on the pipe and its environment 5 100 km (4 600 km waste water) Defects noticed by CCTV inspectionsunder « local » codification 32 232 inspections 89 311 defects Context Data Encodage REREAU Proposition Conclusion Sewers inventory in 2003: • Data base called CHIMERE

4. Context Data Encodage REREAU Proposition Conclusion CCTV « local » codification (extract)

5. Context Data Encodage REREAU Proposition Conclusion EN 13508-2 standard codification (2003) Defect: Break/collapse Main Aditional information description code BAC characterisation The nature of the observation is: Break (A) – pieces of pipe visibly displaced - - Missing (B) – missing pieces of wall - Collapse (C) – complete loss of structural integrity quantification The length of the observation in millimetres Circumferential location The position of the observation Joint international conference on computing and decision making in civil and building engineering - june 14-16 2006 - Montreal

6. Exemple of recodification with EN 13508-2 Joint international conference on computing and decision making in civil and building engineering - june 14-16 2006 - Montreal

7. Context Data Encodage REREAU Proposition Conclusion RERAU methodology • Defects:actual physical state of the pipe • Dysfunctions: consequences of defects • Impacts: effects of the dysfunctions if vulnerability: segment and environment. • Direct observation (O): it is the case of CCTV inspection • Observation-based estimations (E/O): some time results of defects observed by CCTV • Estimations based on risk factors (E/R): step before CCTV inspection.

8. Context Data Encodage REREAU Proposition Conclusion Main categories of dysfunctions

9. Context Data Encodage REREAU Proposition Conclusion RERAU methodology: E/O T criteria valuation Dysfunction INFILTRATION DYSFONCT INF4 - E/O - T indicator , estimated by CCTV inspection Infiltration risk Valuation scale Network and sub - system segment Ø Valuation type Observed Dysfunction Observed - based estimation of Dysfunction Ø Est imations of Dysfunction based on risk factors Unit or gravity levels level : 1/2/3/4 1 – coding Ci of observations Oi according standard EN 13508 - 2 ; Valuation 2 – translating in Ni of coded observations Ci according following table ; 3 – calcul ation of density D = N / Lt , S with N = Ni, et LT :length of the segment (m) ; 4 – comparison of D with thresholds S1, S2, S3 : level 1 if D ? S1 ; 2 if S1 < D ? S2 ; 3 S2 < D ? S3 ; 4 i S3 < D. [ [

10. Context Data Encodage REREAU Proposition Conclusion • Available data • Sewers data and CCTV inspections • The methodolgy • EN 13508 standard for dysfunctions encodage • Using RERAU methodology: Density assess • Calssification of sewers in three main categories Good, medium and bad Application • Use mutli-criteria approach for classification: Electre-tri method • Use an assignment example according given by an expert • Partial inference: wheights and profils Decisions • Investigation plans • Rehabilitation programms Chimer

11. Context Data Encodage REREAU Proposition Conclusion • Available data • Sewers data and CCTV inspections The methodolgy • Using RERAU methodology: Density assess • EN 13508 standard for dysfunctions encodage • Calssification of sewers in three main categories Good, medium and bad • Application • Use mutli-criteria approach for classification: Electre-tri method • Use an assignment example according given by an expert • Partial inference: wheights and profils Decisions • Investigation plans • Rehabilitation programms Chimer EN 13508-2 RERAU methodology Dysfonctions asses Sewers hierarchisation Muti-criteria approach Electre-Tri

12. Context Data Encodage REREAU Proposition Conclusion • Available data • Sewers data and CCTV inspections • The methodolgy • Using RERAU methodology: Density assess • EN 13508 standard for dysfunctions encodage • Calssification of sewers in three main categories • Good, medium and bad • Application • Use mutli-criteria approach for classification: Electre-tri method • Use an assignment example according given by an expert • Partial inference: wheights and profiles • Decisions • Investigation plans • Rehabilitation programms Chimer EN 13508-2 RERAU methodology Dysfonctions asses Sewers hierarchisation Muti-criteria approach Electre-Tri • Investigation plans • Rehabilitation programms

13. Context Data Encodage REREAU Proposition Conclusion • Asset management approach for a given segment • 10 dysfunctions taken into account in decision making, number of • criteria equal to 10. • 3 categories , 2 profiles • We consider an assignment problem of 60 sewers , • 20 for each category according to expert decision Criteria Sewers Categories

14. Context Data Encodage REREAU Proposition Conclusion January 2007 – May 2007 • encoding data available : last year - 2006 • RERAU methodology and density calculation for each criterion • assignment example: expert asses, sample of 60 segments • determination of profiles and weights of criteria : IRIS • application to extended set of sewers in order to propose rehabilitation programs