Changing Gears in the Motor City: A Case Study on Great Lakes Water Authority's Shift to Proactive Pipe Management

摘要

The Great Lakes Water Authority (GLWA) provides water to approximately 4 million people in 127 communities—nearly 40% of the state of Michigan. Up to 1.7 billion gallons of water per day is conveyed to customers through over 800 miles of large diameter transmission mains. In October 2017, a 48-inch prestressed concrete cylinder pipe (PCCP) operated by GLWA experienced a catastrophic failure, resulting in a service impact to more than 300,000 customers, including three nearby hospitals. The drop in pressure caused by the break resulted in reduced pressure, boil water advisories, and loss of service. GLWA, Oakland County, and member partner public works departments worked around the clock to isolate the main break, open emergency connections, and restore water to as many customers as possible while the main was being repaired. At the time of this failure, GLWA was developing a transmission system integrity plan, which included a risk-based prioritization and long-term asset management plan for all their large diameter pipeline inventory. Due to the risk of this main failing again, and considering the now understood consequences, GLWA decided to complete a comprehensive condition assessment as a pilot study to be used as the basis of the integrity program. This paper will provide background on the transmission main and include a discussion of the 2017 failure. This paper will also provide details on the planning and execution of the water main assessment, which posed several challenges because the pipeline has no redundancy. In order to minimize the likelihood of service impacts, GLWA opted to use inline, free-swimming technologies to complete the assessment. Considering that GLWA is a wholesale water provider to more than 127 member-partner communities, planning and executing the assessment required widespread collaboration between internal and external stakeholders. Several risk mitigation procedures were completed prior to the assessment, including test shutdowns and valve operability assessment. In an effort to maximize the information obtained during this assessment, multiple techniques of varying resolution were employed, including a drone flyover, transient pressure monitoring, inline leak detection, and electromagnetic assessment. GLWA determined that the criticality of this main also warranted the installation of a continuous structural monitoring system that will allow them to make proactive decisions in managing this high-risk main. As GLWA moves forward with a transmission system integrity program, the lessons learned from this assessment will serve as the basis for development of a world class, water sector leading program!