Managing Risk at Pipeline River Crossings in Changing Regulatory Settings

Recent high profile exposure and rupture of pipelines at river crossings in the United States (U.S.) has raised the awareness of riverine hazards and the corresponding risks of operating pipeline river crossings. The decadal tendencies for rivers to change vertically (i.e. scour and deposition) and horizontally (i.e. channel migration) increases the risk to ageing pipeline systems. The corresponding cost of the consequences from potential exposures, damages or even ruptures at river crossings has re-defined the risk regime for planning, permitting, designing, installing, operating, and regulating river crossings. Pipeline systems installed decades ago frequently did not incorporate state of the art hydrotechnical engineering approaches, and did not address long-term channel scour and erosion dynamics, instead setting sagbends and burial depths relative to active (i.e. short term) channel conditions and not planning for long-term geomorphic trends. Planning for river crossing routing assessments now include increasing awareness of how riverine systems function. Hydrotechnical studies incorporate hydrologic, hydraulic, and fluvial geomorphic assessments and investigations, as well as environmental, social, and land inputs to the planning, permitting, design and construction processes. Recent high profile damage, exposure, and in some cases rupture of pipelines in river crossings has brought these issues into the public domain. Pipeline regulatory agencies and congressional oversight in the U.S. has responded to recent pipeline incidents in dynamic riverine conditions with increased permit planning, design and operation requirements. This paper will discuss the ways changing rivers are resulting in increasing challenges for pipeline operators, and discusses how Williams Northwest Pipeline (NWP) has implemented several practical mitigation measures to proactively address river crossing risks.