A Tale of Three Projects: Vortex Manholes Design, Operation and Improvement

Vortex manholes have proven effective in resolving some of the worst odor problems in the Water Authority system after multiple alternate solutions failed. The Water Authority’s experience indicates that a primary benefit of vortex manholes is the control of air flow rate to prevent the release of fugitive sewer gas. Testing again demonstrates that H2S levels in the vortex exceed acceptable levels for release. Downstream water quality benefits are addressed but are not conclusively determined. Guided by difficulties with its initial vortices, the Water Authority subsequently developed and implemented design features that provide for improved hydraulics, and associated ventilation, exiting the vortex manhole. The Water Authority has developed and implemented practical design consideration for operation and maintenance (O&M). Modifications were successfully made to correct issues with the initial vortices. The Water Authority operates eight vortex manholes on three interceptors. All are performing well.