Inside the Fence: Assessing and Remediating 60+ Year Old Critical Plant Piping

Public water agencies throughout the United States face many challenges with extending the reliable service life of their aging buried infrastructure. The San Jose/Santa Clara Regional Wastewater Facility (RWF) has the capacity to treat approximately 200mgd, with ongoing projects expanding this number. It is located in the City of San Jose (City) and has approximately 67,000 linear feet (LF) of buried wastewater process pipes, many of which were installed in the '50s and '60s and thus have exceeded their design life. Because of the potential terminal condition for some RWF piping, the City is using this Project to increase operational reliability and mitigate the likelihood of failure of their existing buried linear assets. If selected, the purpose of this presentation would be to share BV and the City of San Jose's approach to a large-scale piping condition assessment and rehabilitation effort. The presentation would include a description of the risk tool that BV developed exclusively for this project, condition assessment methods that were implemented, and rehabilitation methods that were selected. Fortunately for these agencies, many viable pipe rehabilitation methods have been invented to date, and there are often large pools of contractors vying for the job. Unfortunately for these agencies, there is rarely a platform available to share feedback or lessons learned from prior projects, even between neighboring cities. Furthermore, it is rare for an agency to embark on such a large, comprehensive project. Therefore, the largest benefit of this presentation would be the ability to share BV and the City's approach to delivering an on-time/under budget project, which started with developing a piping inspection prioritization tool and ended with rehabilitating pipes to provide an additional 50-year service life. In 2018, the City retained Black & Veatch (BV) for the Yard Piping Improvements Project (Project) to systematically assess all buried process pipes 8 inches to 144 inches at the RWF, which equates to approximately 60,000 LF of piping. Pipes at the RWF are comprised of many materials, but are primarily made of either reinforced concrete, ductile iron, or welded steel. The focus of the multi-year Project is to repair, rehabilitate, or replace (R/R/R) pipes, or portions of pipes, that are highest priority by virtue of their criticality and/or observed physical condition. In 2015, as part of a separate project, BV developed a condition assessment plan that provided a prioritized list of critical pipes for inspection, inspection protocol recommendations, and end of life estimates. The plan used weighted risk factors to determine the LOF (likelihood of failure) and COF (consequence of failure) for each assessed pipe. Depending upon identified pipe risk, inspection protocols and desired levels of inspection detail were determined for each pipeline. The final report produced in 2015 has served as the technical basis for the current Yard Piping Improvements Project, and the recommendations provided in that initial report have largely been followed. To date, approximately 36,000 LF of primary and secondary treatment piping has been inspected. Following each inspection, BV reviews the resultant condition data and makes R/R/R recommendations based on the findings. The Project follows an annual cyclical schedule whereby pipes are inspected during the regional dry-weather season, design work based upon these inspections occurs during the wet weather season, and R/R/R construction proceeds in the next dry-weather season. There is a separate service order for each year's pipe rehabilitation design, and a design-bid-build (DBB) project model is followed for each service order. Approximately 2,200 LF of the 36,000 LF inspected to date was identified to have severe deficiencies requiring R/R/R, and these pipe segments have since been rehabilitated. The scope for the first pipe rehabilitation service order contained primary effluent 96-inch reinforced concrete pipe (RCP) and an elliptical 87x136-inchpipeline. Beginning in the '50s, the RWF has slowly expanded to add more effective treatment processes and to increase the overall plant capacity. As a result of this expansion, there are many buried crossing utilities that preclude the feasibility of applying many traditional rehabilitation methods, resulting in a trenchless method focus. Ultimately, the 96' pipeline was rehabilitated with CIPP, and the 87'x136' was rehabilitated using a combination of concrete crown restoration with geopolymer material with an epoxy top coating. The second pipe rehabilitation service order, which is currently in the design phase, contains more primary effluent RCP including 78-inch, 96-inch, and 84-inch pipeline. CIPP was selected as a rehabilitation method for both the 78-inch and 96-inch pipelines, and concrete crown repair with a with an epoxy top coating selected for the 84-inch pipeline. The overall project is scheduled to be completed in 2026, with phases completed each year. The presentation of the Project, which has never been presented at a WEF Collections Conference to date, will focus on condition and risk assessment, selection of inspection methods and applications, the criteria against which rehabilitation alternatives are compared, planning and successfully executing pipeline rehabilitation.