WSSC Ad-Hoc Committee on Large Diameter Water Mains. November 22, 2013

Transcription

1 WSSC Ad-Hoc Committee on Large Diameter Water Mains November 22, 2013

2 Purpose: To Gain an Understanding of WSSC s Current Approach to Prioritizing PCCP Inspections and Repairs 2

3 PCCP Inspection Prioritization How Did We Get Here? In 2006 and 2007, WSSC Re-organized the PCCP Program and Began to put in Place Some of the Components that Have Led to the Current Program Strategy. Electromagnetic Testing was Introduced to Establish a Wire Break Baseline for Each Pipeline and Acoustical Fiber Optic Monitoring was also Introduced to the Program. In order to Focus Limited Resources a Risk Rating System was Developed to Prioritize 36-inch and Larger PCCP Pipelines for Inspection. The Risk Rating System Assigned a Score to each Pipeline Which was Later Called the Safety Analysis Score (SAS). 3

4 Risk Rating System - Safety Analysis Score (SAS) Safety Analysis Score (SAS) High Score Higher Risk Risk Factors Included in the Score: Land Use (LF) Operational Needs (ON) Known Manufacturing Defects (KD) Repair History (RH) Date Last Inspected (LI) Pipe Diameter (DI) An Empirical Formula was Used to Calculate the Rating for all 36-inch And Larger PCCP Mains 4

5 Land Use Factor (LF) Rating Description 0 Limited Damage Caused by Pipe Rupture 1 Home Water Damage greater than 75 ft from pipe or Down Stream 2 Structural Damage Limited use Road 3 Major Road Likely Flooding 4 Home within 75 ft of Pipe Potential Structural Damage 5 Commercial Facility Likely Water Damage 6 Commercial Facility within 75ft of Pipe - Potential Structural Damage 7 Major Road - Structural Damage 8 Bridge Structural Damage

6 Known Manufacturing Defects Rating Description 1 Lap Joint Weld (Pipe Greater than 60 ) 1 Class III 8 ga pre " and Greater in Diameter Lined Cylinder Pipe 3 Poured Concrete Coating 3 Class IV Wire 5/16 Diameter 4 Class IV Wire 1/4 Diameter 5 Class IV Wire 6 ga (post 1977) 6 Class IV Wire 6 ga (pre 1977) 6 Class IV Wire 8ga (post 1977) 7 Class IV Wire 8ga (pre 1977) 8 Grade E Cylinder

7 Operational Needs (ON) Last Inspection (LI) Operational Needs Rating Description 1 Local Effect Only 2 Water Restriction during Peak Demand 8 Water Restriction during Non - Peak Demand Last Inspection Rating Description 1 Less than 5 Years ago 2 5 to 8 Years Ago 3 9 to 12 Years Ago 4 13 to 15 Years Ago 5 16 to never

8 Diameter (DI) Empirical Formula Diameter Rating Description 0 36" or less 2 42" to 54" 4 60" to 66" 6 72" to 78" 8 Greater than 78 EMPIRICAL FORMULA: RISK = (Defects)*(Operational Needs)*(Land Use) RISK = (RH+DI+KD)*(ON*4+LI) (LF)

9 5-Year PCCP Inspection Plan In 2007, the Risk Rating System was Used to Develop the First 5-Year PCCP Inspection Plan for 54-inch and Larger Mains with an Annual Mileage Goal of 6 Miles of Inspection and 6 miles of AFO Installation. Robotic Technology was Not Available so all Inspections were Manned and Limited to 54-inch and Larger. In FY 09, the Program Mileage was Ramped up to 12 Miles per Year and 48-inch Pipelines were added to the Program so that all Mains 48-inch and Larger Could Achieve the Optimum 5 to 7 Year Inspection Cycle. At the End of 2013, All PCCP Mains 48-inch and Larger will be Inspected and Equipped with AFO Monitoring and 2013 also Marks the Completion of the Inspection Cycle. In FY 13, the Program Mileage was Ramped Up Again to 18 Miles per Year to Include Robotic Inspections of 36-inch and 42-inch mains. 9

10 Prioritizing AFO Monitored PCCP Pipelines FY 14 is the Start of the First Inspection Cycle where all PCCP Mains 48- inch and Larger are Equipped with AFO Monitoring. PCCP Inspections for AFO Monitored Pipelines will be Performed in the Same Priority Order Established Under the 5-Year Plan Depending on the Level of AFO Activity. The AFO Monitoring System will Allow us to Identify the Higher Risk Pipelines to Adjust the Priority of Inspections. If There is Notable AFO Activity for a Particular Pipeline we will Consider Three Options: 1) Assign a Higher Priority in the Inspection Order; 2) Perform Partial or Targeted Inspections of Problem Areas; 3) Perform Interventions for Repairs. 10

11 Prioritization of 36-Inch and 42-Inch PCCP Inspections In FY 13 WSSC Began Robotic Inspections and Installation of AFO Monitoring in the 68 miles of 36-inch and 42-inch PCCP Pipelines Under the 5-Year Plan. Prioritization of the Inspections for the 36-inch and 42-inch Mains was First Established by the SAS Scores and Confirmed Under the WSSC Asset Management Program. The Risk Factors Considered Under by the Asset Management Program to Prioritize the Mains for Inspection were Similar to Those Used in the SAS Scores. Using the Current Mileage Goal of 18 miles per Year, it will Take 8 to 10 Years to Complete a Full Inspection Cycle for all 68 Miles and Install AFO Monitoring. At the Completion of the Cycle, our Approach to Prioritization and Inspection of 36-inch and 42-inch Mains with AFO will be the Same as 48-inch and Larger. 11

12 PCCP Repair Prioritization How Did We Get Here? Historically, WSSC Finance Policy Considered the Repair or Replacement of Less Than 100 Feet of Water Main a Maintenance Activity Which had to be Funded by Operating Funds. Operating Funds Have a Far Greater Impact on Water Rates Than Capital Funds, Therefore, Obtaining the Necessary Funding for PCCP Repairs Became a Real Challenge. Decisions on Which PCCP Pipes to Repair or Replace Prior to FY 09 was Based on Limited Available Operating Funds and Only the Worst Condition Pipes Could be Repaired. In Order to Implement the PCCP Program as an Effective Asset Management Strategy, Adequate Funding for the Needed Repairs was Essential. 12

13 PCCP Repair Prioritization How Did We Get Here? Requested the Finance Office for a Change in Policy to Capitalize PCCP Repairs and Replacements Less Than 100 Feet. The Policy was Changed and we Established the Large Diameter Rehabilitation and Replacement Capital Improvement Program Also Known as CIP No. W Under the New CIP Program, the Decision on Which PCCP Pipe Sections to Repair Could Now be Made Based on Pipe Condition Not Funding. If a Pipeline has a High Number of Pipe Sections That Require Repair and is No Longer is a Candidate for the PCCP Program Asset Management Strategy then it is Considered for Replacement Under the CIP. In FY 11, the Brightseat Road 54-inch PCCP Main was Found with 36% of the Pipe Sections with Broken Wires, Repairs Were Not Cost Effective so the Main is Being Replaced. 13

14 Repairs Decisions Following Inspection Internal Inspection Data Analysis FEA* Curve for Each Pipe Class High to Moderate Level Damage Low Damage No Damage Repair or Replace by Planned Emergency Acoustic Monitoring * Finite Element Analysis

15 Prioritizing Pipes for Repair or Replacement The Pipe Sections Found with a High to Moderate Level of Damage as Determined by the Finite Element Analysis Curve are Permanently Repaired or Replaced. High to Moderate Damaged is Defined by the Number of Existing Wire Breaks as Compared to the Finite Element Analysis (FEA) Curve. WSSC Repairs or Replaces ALL Pipe Sections when they are Within 20 Wire Breaks of the Yield Limit on the FEA Curve. We do not Consider Land Use when Making a Decision on Whether or not to Repair a Pipe. Pipe Repair Decisions are Based on the Condition of the Pipe Sections. Our Goal is Repair all Pipe Sections that Require Repair in Order to Prevent PCCP Failures and Maintain the Continuous and Safe Operation of our Transmission Mains. 15

16 Repair Action Level FEA Analysis: Finite Element Analysis is used for each Pipe Design to Determine the Action Level for Repair. WSSC Repairs or Replaces ALL Pipe Sections when they are Within 20 Wire Breaks of the Yield Limit on the FEA Curve. 16

17 Inspection Prioritization Challenges Unplanned Maintenance and AFO Interventions: Due to Limited Redundancy in the Transmission Main Network, Executing the 5-Year Plan in Priority Order is Often Disrupted by Unplanned Maintenance Events Such as Malfunctioning Valves, Leaks, etc. Significant Delays Can Occur. As More Pipelines are Equipped With AFO Monitoring, and the Pipelines Continue to Age, Repairs Associated with AFO Interventions will Cause Delay and Changes to Pipeline Inspection Priority. Planned Work by WSSC and Others: Coordination Between 48-inch and Larger and 36-inch and 42-inch PCCP Mains Presents Further Challenges with Prioritization. Planned Work by WSSC and Outside Agencies and Developers Requires Flexibility and Adjustments in Inspections Schedules Because the Timing of these Projects is Often Uncertain. 17

18 18