Mission Bay SFPUC 66-inch Sanitary Sewer Force Main and 30" Drain Line

This project involved working in and around an active San Francisco Utilities Commission (SFPUC) 66-inch sanitary sewer force, so SAFETY was the primary concern from day one. Extensive pre-planning was required to coordinate the requirements of SFPUC, Catellus, and other specialty subcontractors. Each shift had to be planned with great attention to details, since no redundant system or temporary by-pass was available. After each shift, the force main had to be returned to operation since the pump station had very limited holding capacity. This required the majority of the project to be performed at nights and weekends which added other restrictions.

A new 30-inch drain line and corresponding plug valves were installed at an existing manhole structure. These valves were installed by underwater hardhat divers, since a complete shutdown was not available. McGuire and Hester installed an equalization chamber that allowed divers to enter the pipe, remove the damaged valve, and install the replacement valve all while the pipe line was under pressure.

We also assisted underwater hardhat divers entering the active sanitary sewer force main at multiple locations to inspect the existing condition of the pipeline. Much of these improvements were installed to provide the necessary infrastructure and information for a future project that would realign this sanitary sewer force main.