A Multi-Pronged Approach in Condition Assessment and Risk Analysis of Underground Utilities at GLWA’s 1,700 MGD Water Resource Recovery Facility

The Great Lakes Water Authority (GLWA) owns and operates the largest Water Resource Recovery Facilities (WRRF) in the United States and the American continent. To ensure reliable treatment of 1,700 million gallons per day (MGD) of wastewater, GLWA needed to assess the condition and potentially rehabilitate more than 30 mi of underground support utilities that have been constructed in the last 90 years. A multi-prong approach was used to assess the condition of the gravity and pressurized sewer, potable and service waters, natural gas, steam, and compressed air systems. Various available tools and methods were evaluated to collect information on the condition of the underground utilities, and a toolbox of applicable methods was developed. Data collected through soil and pipe material tests, visual inspection and surface measurement, flushing and fire hydrants test, valve exercising, acoustic leak detection, tethered CCTV inspection, manhole inspection, and ultrasonic and electromagnetic pipe wall thickness measurements were used to perform risk analysis of the assets. The result of quantitative risk analysis helped prioritize the rehabilitation practices required to improve the resiliency and reliability of the systems and improve their service life while reducing operation interruption. This paper covers the triage process for setting up a practical toolbox for condition assessment of congested and complex underground utilities within the fenced area of a heavily industrial and active facility, followed by a quantitative approach to risk analysis to prioritize improvements. This paper’s shared experience and techniques can be beneficial to facility directors and managers and help them take a more informed and organized approach to condition assessment and prioritization of their underground assets.