River Crossing Inspections—Balancing Risk with the Need to Obtain Advanced Pipeline Condition Assessment Data

Increasing regulatory pressure to prevent inadvertent spills of both chlorinated water and wastewater to the environment has resulted in a drive by municipalities across North America to inspect and quantify the condition of their river crossing inventory. Estimating remaining service life requires the use of both structural assessments and deployment of advanced condition assessment technologies, including sonar, closed circuit television (CCTV), and advanced electromagnetics tools. River crossings pose a unique challenge for condition assessment programs as they are highly critical assets subject to unique operating conditions and are often difficult to access for both inspection and repair. Deploying inline inspection tools can require extensive system modifications and are often located in environmentally, geotechnical, and socially sensitive areas such as river banks and mature neighborhoods. As a result, developing a river crossing inspection program requires extensive planning, assessments of system hydraulics, pipelines access, geotechnical conditions, and contingency planning. Lack of system redundancy often makes removal from service difficult, if not impossible and planning system modifications and inspections requires reviewing system operations as a whole in addition to localized flow control requirements. Inspection of both gravity and pressure pipelines requires review of a myriad of potential operations to permit both system modifications and the inspection work itself. These include: upstream system storage, lift station shutdowns, pressure drops, and flow reversals in looped water systems, etc. As a result, extensive hydraulic modeling and coordination with system operators is required to develop flow control plans permitting necessary system modifications and tool deployment. This paper outlines the authors approach to developing advanced river crossing inspection programs addressing pressure and gravity system hydraulics, system modifications, tool deployment, and procurement of inspection and support contractors.