The city of Odessa, Texas,

http://dx.doi.org/10.5991/opf.2012.38.0027 John D Antoni is a principal with Alan Plummer Associates (www.apaienv.com), Houston. Roy Staggs, assistant director of utilities, and Ajay Shakyaver, city engineer, are with the city of Odessa (www.odessa-tx.gov), Odessa, Texas. Plan Sets the Stage for Rehabilitation and Sustainable Renewal An aging infrastructure and related problems prompted Odessa, Texas, to implement a $42 million water and sewer improvement program. Its experience offers lessons for other cities. By John D Antoni, Roy Staggs, and Ajay Shakyaver The city of Odessa, Texas, experienced unprecedented growth during the 1950s and 1960s, which spurred construction of additional infrastructure, including mixed piping and material types. Over the years, the city s infrastructure has experienced an increasing number of water main breaks and other distribution system problems. Table 1. Water Pipe Segment and Pipe Asset Summary AA and DA classifications provide a more manageable grouping for project planning. Data Category Number Counted Miles of Pipe 621 Number of Pipe Segments 10,067 Number of Assets AA-Area Assets ( 10 in.) DA-Discrete Assets (> 10 in.) 122 371 Recognizing the need for a substantial reinvestment in the city s buried infrastructure, the Odessa city council approved the Water and Sewer System Improvement Program (WSSIP), a $42 million water and sewer pipe renewal program to be completed during a 6-year period. A comprehensive asset management plan was developed to prioritize pipeline replacement and develop tools to implement a sustainable infrastructure program. Approach The infrastructure assessment used a topdown process that maximized city data and tapped into staff experience. WSSIP project goals were to renew aging infrastructure. reduce water line breaks. improve water quality. renew the most pipe for the budget. meet regulatory compliance requirements. formulate plans for a sustainable future. reduce reactive maintenance. To meet these goals, the asset management planning effort focused on pipeline performance and condition assessment of traditional structures. In developing an overall risk-based renewal program, likelihood- and consequenceof-failure analyses accounted for performance failures. The program was designed to balance renewal funding between water and sewer pipelines and emphasize performance of smaller pipelines. To complement the initial WSSIP investment, the Water Research Foundation s KANEW model was used to develop a long-term sustainable renewal plan. Data Collection and AnalysEs Data from various city sources was collected, compiled, and analyzed, revealing that the city s water and sewer systems consisted of about 1,100 miles of pipe and nearly 20,000 individual line segments. Because classification of water and sewer system piping was critical to assess and implement the planning 22 Opflow May 2012 www.awwa.org/opflow

Buildup on Joint Buildup on Pipe Prototype acoustic and video inspection laid the groundwork for future inspection programs. PHOTOGRAPHs: PURE TECHNOLOGIES process, a classification protocol was developed. Ten years of customer service data helped characterize system performance. Larger water pipelines were designated as discrete assets, with renewal projects organized on a line-segment basis. Smaller lines of similar material and age were grouped by geographical area for replacement. For pipelines, 10 in. in diameter and larger, a contiguous segment of similar size, material, and age was managed and assessed as one asset, called a discrete asset (DA). A total of 371 DAs representing 120 miles of pipe were designated in the water system, and 241 assets representing 112 miles of pipe were designated in the sewer system. Smaller lines less than 10 in. in diameter constituted about 80 percent of total pipeline footage. A pipeline less than 10 in. in diameter within the same geographic area was assessed as one asset and called an area asset (AA). This concept targeted all smaller-diameter pipe for replacement or rehabilitation in a given area. After evaluating various options, the established section/quarter-section grid system was chosen as the basis for area classification. Table 1 summarizes water distribution pipe assets. Although the risk analysis was performed at the linesegment level, individual line-segment risk factors and scores were included in the DA and AA levels. Data assessment and gap analysis provided additional information. In addition, information from property parcel records helped complete pipe-age records, and pipe size and age data helped complete the material records. Data sources were flagged in the database to define relative accuracy and in case the data needed to be reassessed and confirmed. To assess the condition of the overall water distribution system, staff interviews were conducted with the management team and operations and maintenance staff members. The purpose of the interviews was to develop an initial condition assessment of the overall water distribution system. Staff members provided a pipe condition score using the quartersection grid mapping system. The final step in the data-collection and analysis effort was a comprehensive data management plan that defined how data would be stored and used during the planning process. In addition, the plan defined how the expanded database would be used by the city and integrated into its overall information management systems. Performance Assessment The water distribution performance assessment included evaluating waterline breaks, dirty water, leaks, low pressure, and water quality concerns. Data consisted of customer addresses linked to service order complaints, hydraulic model simulations of small-diameter water lines, and other water quality parameters (e.g., chlorine residual, disinfection byproducts, and bromide) from different parts of the city. www.awwa.org/opflow May 2012 Opflow 23

Figure 1. Sample GIS Point-Density Plot Point-density plots indicate areas that require attention and are useful communication tools. Service-order complaints for leaks, low pressure, dirty water, and line breaks were geocoded and mapped as point densities in the city s geographic information system (GIS). When individual geocoded customer complaints were linked to the nearest water line, pipe material, size, and age could be analyzed. Data from the hydraulic model included junction pressures for maximum day demand and hydraulic grade line during peak-hour demand. Water age information was obtained from model runs using an extended-period simulation. Figure 1 illustrates a typical point-density plot for line-break data. Indicating areas that need attention, the point-density plots are useful for communicating problems to elected officials and the public. The potential for other water quality problems was analyzed based on average total chlorine residual by city section from June 2003 to May 2008. Generally, Point Density (Events/Square Mile) for Line Break Complaints January 2000 July 2008 Line Breaks 1 19 20 47 48 95 96 142 143 189 N Full Sections Water Line Streets Arterial Highway Major Road Railroad 0 2 4 Miles the southwest part of the distribution system experienced lower chlorine residuals than the rest of the city. However, hydraulic model evaluations suggested that water age in this area wasn t unusually high, indicating that the low residual chlorine was most likely caused by pipe age, material, and condition. Lower chlorine residuals in the upper pressure zone and the northeast part of the city likely result from higher water age, not pipe age or condition. Elevated water ages, as well as the presence of bromide and nitrites, also contribute to elevated trihalomethanes in the upper pressure zone. After the hydraulic model of the city s water distribution system was updated and expanded to include all pipes, the model validated low-pressure complaints along a ridge between the upper and lower pressure plane. Model results will help city personnel recommend the appropriate line size during pipe renewal. Pipeline Risk Analysis A risk-based approach helped prioritize water distribution system renewal, including quantifying the likelihood and consequences of failure. The likelihood of failure was estimated by considering an asset s performance and structural, hydraulic, and water quality condition. Consequences of failure were estimated by considering the effect of asset failure on city finances, public well being, economy, and environment. By understanding the risks posed by asset failure or inability to meet specified service levels, city staff can mitigate risk by identifying operation and maintenance procedures, capital rehabilitation, and replacement projects. The riskanalysis process is illustrated in Figure 2. A detailed risk matrix was developed with utility staff to assess the probability and consequence of water line failure, as well as corresponding weights customized for the city, as shown in Table 2. Asset data, including pipe attributes, were loaded into the GIS database. A GISbased risk assessment tool was then used to develop component scores, calculate likelihood and consequence of failure, an overall risk score for each of 10,000 individual water-line segments, and relative ranks for each line segment. Composite scores were calculated for DAs and AAs by averaging the scores of individual line segments within the asset. Final asset risk scores were validated with city staff in a post-prioritization workshop that incorporated hands-on experience and intuition. Some pipeline assets were identified for replacement or rehabilitation. Other assets were targeted for physical inspection to confirm condition before finalizing renewal decisions. Some assets were given a lower priority based on staff s knowledge of actual condition or through consequence-of-failure mitigation. Prototype Pipeline Inspection A prototype field inspection program was initiated to test the effectiveness of 24 Opflow May 2012 www.awwa.org/opflow

Implementing WSSIP is expected to significantly increase the city s knowledge of its infrastructure inventory, condition, and life expectancy. current inspection technologies and to learn more about actual pipe condition. Resulting data were extrapolated for pipe of similar size, material, and age. Although some older pipelines were targeted for immediate replacement or rehabilitation, a portion of the system was inspected to determine its actual condition. About 3 miles of water mains were inspected with acoustic, video, and wall-thickness technologies. Largerdiameter pipelines provided ready access for the inspection equipment. One large and several small leaks were identified. This prototype inspection program helped city personnel assess the technology and plan the overall asset-inspection program. The opening images on page 23 illustrate video quality. Important additional lessons were learned during the prototype program: Insertion-type inspection technology should be used only on larger-diameter transmission mains. Substantial planning, engineering, and field testing is required before actual field inspection. City maintenance crew support is required during inspection. Competitive bid documents for inspection services should require and quantify allowances for downtime and disruption of company and city crew inspection activities. Priority Renewal Strategy The prioritized list of DAs and AAs was organized into projects based on priority and location. Eight DAs and nine AAs were programmed for immediate action. Other water lines were slated for field inspection, and a construction allowance for each inspected asset was programmed into future construction. Although individual project elements offer flexibility in assembling bid packages for design and construction, a 5-year implementation plan was developed to guide WSSIP implementation. Figure 2. Overall Risk Prioritization Process The risk assessment included quantifying the likelihood of failure and the consequences of failure. Prepare Asset Database Refine Risk Matrix as Necessary Perform Final Business Risk Assessment The 5-year plan provides for inspection, design, and bid, with construction to be completed in the program s sixth or seventh year. Figure 3 on page 26 summarizes the overall WSSIP capital improvement forecast. The Odessa city council recognized the need for reinvesting in the city s existing pipeline assets to avoid further deterioration and reduced customer service levels. The WSSIP Implementation Plan prioritizes a 5-year investment program that Table 2. Risk Matrix Components and Weights A methodology was developed to weight and score the various risk components. Likelihood-of-Failure Components Weight % Staff opinion of condition 16 Develop Risk Matrix Review Asset Component Scoring Post-Prioritization Processing Consequences-of-Failure Components Public and utility employees health Finalize Asset Database Perform Initial Business Risk Assessment Final Prioritized Results Asset Renewal Program Weight % Break and leak history 16 Loss-of-revenue financial impact 5 Time since second break 11 Repair costs financial impact 10 Age 10 Loss of public confidence/loss of service 10 Material 11 Loss of service to critical facility 20 Joint type 11 Proximity to main roads or railroads 15 Embedment zone backfill material 4 Head loss 3 Lowest operating pressure 5 Fire flow 5 Dirty water complaints 3 Chlorine residual 5 40 www.awwa.org/opflow May 2012 Opflow 25

targets nearly 1 million linear ft of water and sewer mains for replacement, inspection, or rehabilitation. The implementation plan addresses about 17 percent of Odessa s 1,100 miles of buried pipelines. The investment will help improve overall system performance and reduce the frequency of main breaks, blockages, and other failures. The initial investment will also jump-start the city s long-term investment plan. Sustainable Renewal Plan Replacing a pipeline at the right time is often a challenge. If a pipe is replaced too soon, a portion of the asset s value is lost. However, waiting too long increases the risk that a main break will cause disruption and necessitate costly repairs. Utility pipeline life cycles range from 15 years to more than 100 years, depending on material type and the environment. The purpose of having a long-term sustainability plan is to predict future levels of water and sewer main replacement or rehabilitation required to maintain customer service and system performance standards. The KANEW model helped city staff predict long-term rehabilitation or replacement needs beyond WSSIP. Although the long-term sustainability renewal plan wasn t developed at the same level of detail as WSSIP, it provides a long-term infrastructure investment forecast. The KANEW model forecasts pipe replacement based on the city s pipe life expectancies. Pipe life expectancies or survival functions were based on industry standards and refined specifically for the city based on staff input. Life expectancies in years were developed for three conditions: One hundred percent of existing pipe is still in the ground and in service. Fifty percent of original pipes of that material have been or are anticipated to be in service without replacement or substantial structural rehabilitation. Ten percent of original pipes of that Figure 3. Overall WSSIP Capital Program Forecast A 5-year plan was developed as an initial guide for water and wastewater projects. Pipe Renewal Investment, $ million 9 8 7 6 5 4 3 2 1 0 2010 2011 2012 2013 2014 Water DA Water AA Sewer DA Sewer AA Inspection material have been or are anticipated to be in service without replacement or substantial rehabilitation. Based on age and material of the current water and sewer pipeline inventory, the city has a backlog of pipeline replacement and rehabilitation work. The current WSSIP is an excellent first step in addressing pipeline infrastructure renewal needs. The program will target pipelines with the highest failure risk and performance problems. However, WSSIP won t eliminate the replacement and rehabilitation backlog. Continued investment in the city s pipeline infrastructure is required to avoid further system degradation. The funding gap for water and sewer system infrastructure is a national issue. Most cities face difficulties in funding pipeline replacement and rehabilitation at levels identified in the KANEW analysis without state or federal assistance. The KANEW analysis reinforces the city s need to increase and sustain investment in its pipeline infrastructure. Implementing WSSIP is expected to significantly increase the city s knowledge of its infrastructure inventory, condition, and life expectancy. Data gathered through detailed field inspection and pipeline replacement programs can help refine the city s sustainable infrastructure renewal plan. WSSIP plan recommendations included development of a funding strategy to increase city investment in its pipeline infrastructure over time until a ±1 percent/year replacement level is reached. That replacement level corresponds to a total annual investment of $6 million to $10 million for buried pipeline infrastructure in the water and sewer systems. WSSIP Implementation The city of Odessa is in the fourth year of $42 million WSSIP implementation, which began in 2008, well before the overall asset management plan was completed. Although areas were moved up in priority based on staff input, projects have generally followed the overall prioritized implementation plan. For most projects, the city has completed the inspection, surveying, and design with in-house resources. 26 Opflow May 2012 www.awwa.org/opflow