Understanding Pneumatically-Induced Hydraulic Surges and Geysers in Sewers

摘要

The need for urban sewers continues to grow due to numerous causes, such as population growth, climate change, and the desire to prevent sewage from discharging to the environment. To meet this need, many owners are installing tunnels as part of the solution. Surges and other transients, which are predominantly a wet weather feature, are more common in large-diameter sewers in deep tunnels than near-surface sewers. While the hydraulic drivers of surges and transients are well-documented and generally well-understood, the role of air in inducing these surges and geysers is less so. Pneumatically-induced hydraulic surges can result in geysers, which are violent eruptions of sewage that occur at the ground surface. These geysers can result in numerous potential health and safety concerns, such as damage to infrastructure, discharges of sewage to the environment, displacement of protective manhole covers, trip/fall hazards, etc. Through the use of real-world examples, this paper examines the causes and effects of pneumatically-induced hydraulic surges and geysers in sewers. The associated presentation includes several videos of real-world geysers, as well as modeling result animations from surges in tunnel systems. These videos and animations provide the practitioner with a solid grasp of the causes and effects of air in tunnel systems under wet weather events.