ASBESTOS CEMENT PIPE: ASSET OR LIABILITY?

Transcription

1 ASBESTOS CEMENT PIPE: ASSET OR LIABILITY? DOUG SCHLEPP, P.E. PRINCIPAL RH2 ENGINEERING MATT HUBBARD, SYSTEM PLANNING ENGINEER TACOMA WATER PNWS-AWWA, DISTRIBUTION COMMITTEE SECTION CONFERENCE 2017 KENNEWICK, WA

2 HISTORY OF ASBESTOS CEMENT PIPE IN NORTH AMERICA, ASBESTOS CEMENT PIPE WAS INSTALLED BEGINNING IN THE 1930 S UNTIL THE 1980 S IN AREAS PRONE TO CORROSION. OVER THE LAST 30 YEARS, ASBESTOS CEMENT PIPE HAS BEEN REPLACED WHOLESALE WITH MODERN PIPE MATERIALS. WERE THE MILES OF PIPE REPLACED A LIABILITY OR POSSIBLY AN ASSET? 2

3 MAIN REPLACEMENT PROGRAM PAST PHILOSOPHY: 100 year replacement cycle is desired All Asbestos Cement Pipe is considered to be at the end of its useful life All main breaks are considered to have the same detrimental impact Take advantage of project partnering opportunities 3

4 MAIN REPLACEMENT PROGRAM PRESENT PHILOSOPHY: Use of Advanced Asset Management Principles Understanding and accounting for risk Risk Likelihood of Failure Consequence of Failure Managing assets to the Lowest Lifecycle Cost Considering type of failure Condition assessment utilized Strong emphasis on project coordination Consideration of economic development and timing of main replacement projects Asbestos cement mains are considered to have remaining life 4

5 OPTIMAL REPLACEMENT STRATEGY 5

6 OPTIMAL REPLACEMENT TIMING Economic model developed to prioritize replacement of main segments Calculates Annual Risk Costs and Annualized Replacement Costs The intersection of these Costs indicates the optimal replacement timing Economic model results confirmed through use of condition assessment Replacement Cost Risk Cost 6

7 INFERENTIAL ASSESSMENT INDICATORS 7

8 CONDITION ASSESSMENT INFERENTIAL ASSESSMENT INDICATORS Pipe Class: Type I or II Age: indicator for exposure Soil: ph, Sulphate, contamination Water Quality: Hardness/Alkilinity Loads: Frost, traffic, water pressure Failure Records: Leakage/Breakage 8

9 CONDITION ASSESSMENT TECHNOLOGIES AND TECHNIQUES Acoustical Testing assess wall softening Visual Inspection by Video External/internal hardness fingernail or metal scraper Residual strength crush/pressure test Phenolphthalein testing determine remaining undegraded pipe wall thickness 9

10 CONDITION ASSESSMENT ACOUSTIC TESTING AT TACOMA Tested 58.6 miles over 5 years Average cost of $2.74 per foot Field results averaged -12% of lab results (ranging from -27% to +1%) 10

11 CONDITION ASSESSMENT Wall Thickness Assessment 11

12 CONDITION ASSESSMENT DATA Databases and GIS Economic Model Increased failure probability based on wall thickness 12

13 CONDITION ASSESSMENT BENEFITS Provides quantifiable data for business cases Better informed main replacement decisions Deferral of capital cost, and redirecting funds to high priority projects Realize more value from existing assets by deferring replacement 13

14 CAPITAL PROJECT SELECTION & EXECUTION Project Sources A. Economic Model Condition Assessment B. Planned, Coordinated Projects C. Projects of Opportunity 14

15 CAPITAL PROJECT SELECTION & EXECUTION Project Sources Project Assessment and Execution A. Economic Model Condition Assessment 2. Prioritize Project List B. Planned, Coordinated Projects 1. Develop Business Case Evaluations (BCEs) 3. Approve BCEs/Budget C. Projects of Opportunity 5. Assess Opportunities 4. Execute & Coordinate Projects 15

16 ECONOMIC PROJECT GROUPINGS COSTS DEVIATION Replacement Cost Risk Cost BENEFITS RESTORATION AVOIDED RISK EFFICIENCY NET BENEFIT 16 16

17 MODELING ASSUMPTIONS Replacement Likelihood Consequence ECONOMIC MODEL Main Replacement Costs (per foot) Engineering/Technician Materials and labor Pipe removal (if applicable) Boring (if applicable) Pavement restoration by class Landscape restoration Failure history by material class (Weibull Curves) Condition assessment Corrosive soils Main Break Financial Costs: Repair costs Shutdown costs Excavation costs Railroad Damages Emergency premiums Consequence High pressure premiums Property damage Water quality costs Contaminated soil disposal costs Bridge damages Pavement mitigation fees Pavement restoration costs Main Break Social Costs: Outage costs Traffic costs Poor water quality costs Main Break Environmental Costs: Environmentally sensitive area restoration Fish impacts Steep slope erosion

18 MODELING ASSUMPTIONS PROJECT GROUPINGS (MAD MODULE) Combines Economic Model assumptions for multiple water main assets into a single analysis Replacement Cost Inputs: Risk Cost Year of Restoration Opportunity Restoration Savings Percent Efficiency Savings Moratorium Cost Moratorium Duration Failure Multiplier Duration of Savings Benefit (from multiplier) Project Cost/LF check

19 QUESTIONS? 19

20 20 BACKUP SLIDES

21 ABOUT TACOMA WATER FOUNDED IN 1893 OVER: 117 square miles of service area 100,000 connections 300,000 people 21

22 COMPOSITION OF DISTRIBUTION SYSTEM Material Type Plastic, 4% Steel, 0.2% (1970s-1990s) Galvanized, 0.3% (Inception Early 1980s) Asbestos Cement, 11% ( ) Cast Iron, 7% ( ) Ductile Iron, 47% ( Present) Old Cast Iron, 14% ( ) WWII Cast Iron, 16% ( ) 22

23 AC CONDITION ASSESSMENT TECHNOLOGIES AND TECHNIQUES Acoustical Testing 23

24 CONDITION ASSESSMENT CASE STUDY DUMAS BAY MAIN REPLACEMENT PROJECT 6,000 lf of AC Installed in 1968 Estimated cost: $1,400,000 24

25 CONDITION ASSESSMENT CASE STUDY DUMAS BAY MAIN REPLACEMENT PROJECT AFTER CONDITION ASSESSMENT 1,933 lf of AC Project cost: $623,804 Approximate Condition Assessment Cost: $20,000 25