Collection System Inspection Overview

Transcription

1 MWEA Collections Seminar October 1, 2009 Collection System Inspection Overview Rod Thornhill, PE White Rock Consultants Dallas, Texas

2 What can we do with CCTV Data? Asset Inventory PM Planning GASB-34 Compliance Hydraulic Modeling New Construction Inspection Deterioration Analysis CMOM Compliance Mapping Updates/GIS I/I Reduction

3 Miles of Pipe History of Sewer Pipe Installation Total Approx 520,000 Miles EPA Gap Analysis

4 Components of Long Term Data Usability Standardization of coding, training, and database archiving Data must be accurate, reliable Understanding the importance of monitoring change in condition Recognition that condition of pipe today will be of interest in the future Consider the question, How long do I want my pipeline condition data to last?

5 Some Long Term Applications of TV Data Population of GIS database Maintenance Management database and Scheduling Evaluation of Deterioration factors Estimation of life expectancy of pipe

6 Population of GIS Database TV data used to ground truth GIS data Many data elements used in GIS collected during TV inspection One-time integration with TV data creates repeatable path into GIS Volume of data accumulates very quickly

7 PACP Header Form Data Useful in GIS Length Diameter Material USMH Depth DSMH Depth Pipe material changes Tap Locations Tap Diameters Line Direction changes Line Diameter changes Location/Address Joint Length

8 Population of Maintenance Management Database Many fields applicable in GIS are used in maintenance management TV data determines operational and maintenance condition of pipe (roots, debris, lack of O&M problems) O&M condition data used to schedule appropriate maintenance activities

9 Pipeline Deterioration Analysis A before and after assessment of a pipeline Provides a quantitative understanding of rate of deterioration progression Should also include pipe condition and other factors such as soils, surcharging, groundwater, roots, age, etc. PACP standards provide the ability to share with other utilities nation-wide

10 Draining for Profit and Draining For Health Col. George E. Waring 1867 Every reported case of failure in drainage which we have investigated, has resolved itself into ignorance, blundering, bad management, or bad execution Gisborne Quote on title page of book, referring to William Gisborne, Minister of Public Works, New Zealand

11 Excerpts from Metcalf and Eddy Design of Sewers Volume I, 1914 American sewerage practice is noteworthy among the branches of engineering for the prepondering influence of experience rather than experiment upon the development of many of it s features, apart from those concerned with treatment of sewerage First sentence of Introduction

12 Bulletin 31 Iowa State College 1913 Dr Anson Marston Extensive discussion of unexplained failures in new pipe construction First to establish Theory of Loads on Pipes in Ditches First to develop load strength tests for cement and clay sewer pipes Found wide-spread variability in pipe that otherwise appeared to have identical strength

13 Deterioration and Collapse Mechanisms Water Research Centre (WRc) has studied mechanisms that influence the deterioration of sewers Rate of deterioration of sewer depends upon many factors, including the structural condition Risk or likelihood of collapse related to structural performance grades.

14 3 Stages of Collapse STAGE 1 -an initial defect enables deterioration process to commence STAGE 2 - deterioration process continues in and/or behind the sewer wall STAGE 3 Collapse occurs due to weakened wall. Re-enforces the idea that even today we must be diligent with new construction inspection

15 Steps to Understanding Pipe Condition Change Thorough assessment of current condition of pipe Identification and quantification of factors affecting each individual pipe Understand era and circumstances of original construction Understand maintenance and repair history of pipe Apply knowledge gained to plan the future of each pipe Use retro-assessment of previous inspection to detect and evaluate change

16 Thorough Assessment/Benchmarking of Current Condition of Pipe Adopt and implement a standard code set and procedures for logging pipe conditions Require use of standard condition assessment by all in-house personnel and outside firms. Develop a software and data management strategy that assures the longevity of the condition assessment information Maintain an on-going coding quality control program

17 Estimation of Remaining Life Expectancy of Pipe Little quantitative pipe survival data available so engineers gravitate to using 50 years as a fallback position. Lack of ability to estimate remaining life of pipe a glaring weakness in sewer asset management Preliminary findings to develop life expectancy yields surprising results

18 Deficiencies in Life Expectancy Assessment to Date Majority of sewers in place today were only first televised years after construction Many of the defects in pipes were created during construction Up until now, the US had no ability to quantitatively measure change in pipe condition

19 Major Deterioration Factors Soil in trench surrounding the pipe and native soil outside of trench Position of groundwater table Frequency and magnitude of surcharging within the sewer Loading of the sewer during construction Quality of sewer construction 3 rd party action

20 Major Deterioration Factors (Cont d) Method for connecting service laterals Strength of original pipe material and loss of pipe strength, if any. Alignment of sewer and presence of sags Roots, grease, debris causing surcharging and necessitating more frequent cleaning Method and frequency of cleaning

21 Root Induced Deterioration Roots intrude through existing pipe defects Root growth expands existing pipe defects and creates new defects Root growth can result in blockages and overflows Surcharging caused by root growth will accelerate structural deterioration Deterioration Mechanisms

22 50 Years of Root Growth

23 Change Caused by Aggressive Cleaning Suspected

24 PACP Reinforcement Projecting (SRP)

25 Pipe Failure Likely Created During Construction

26 Life Cycle of Sewer Line $ Replacement Costs C o s t s Structural Grade Renew/Replace R A T I N G New Time

27 Minimizing Effects of Deterioration Mechanisms Maximizes Longevity of Pipe Remove defects that allow roots, GW, surcharging, poor soils to enter Minimize or eliminate roots or groundwater Minimize or eliminate surcharging or surcharging effects. Avoid cleaning techniques that damage pipe

28 Don t Ignore Retrofitting Existing Data Very inexpensive compared to obtaining new data Audio and Video often of excellent quality Can add up quickly to a considerable portion of the system Provides immediate ability to assess rate of deterioration by comparing old data to new

29 Use Knowledge Gained to Plan the Future of Each Pipe Which defects probably are construction-related Does pipe need to be cleaned What impact does roots and root control have Aggravating existing defects Creating new defects Is the Pipe Material deteriorating (i.e. H2S) and at what rate When is the next inspection needed

30 Pipe Deterioration and Repair/Replace Decisions Each pipe will have a Probability of Failure (POF) based on conditions specific to that pipe POF generally correlates to Life Expectancy Process will lead to methods for extending life of pipe Continual improvement will be conducted by adjusting deterioration rates over time and testing estimates of deterioration with PACP coding and a calendar

31 Population of Other Application Databases Hydraulic Modeling programs Accounting databases (GASB-34) SSES Projects Nationwide wastewater pipeline integrity management research

32 Process of Pipeline Condition Management Continual Improvement Criticality Proactive Decision Matrix Condition Assessment Deterioration Mechanisms

33 What are Critical Sewers? Sewer where the costs associated with the failure of the sewer likely to be high. Fall into three broad bands construction costs associated with repair traffic delay costs strategically important (trunk sewers)

34 Sample Critical Sewer Matrix A Most Critical 5-10% of System B Critical 10-15% of System C All Other Sewers Traffic Vehicles/Day Depth of Sewer 10 feet or less Depth of Sewer Greater than 10 ft Good Soil Bad Soil Good Soil Bad Soil <10,000 10,000 to 15,000 15,000 to 20,000 >20,000 Criticality

35 Summary Temporal, time-sensitive approach needed to better understand deterioration mechanisms and rates of deterioration Standards for describing and documenting structural and O&M conditions essential for industry Historical documents have a wealth of information Think long term, big picture