Two Sections of Sewer Main to be Relined
Closed-circuit video of two segments of a 60-year-old sewer main showed corrosion, cracking, and flaking. “The sections of this 36-inch-diameter reinforced concrete pipe are in failing condition, and we need to reline them to extend their life another 50 years,” says Associate Engineer Rudy Portugal.
This pipe collects sewage from east Dublin and Parks Reserve Forces Training Area and conveys it to the Regional Wastewater Treatment Facility located in Pleasanton on Johnson Drive.
Between the two sections of this sewer main, there is a 1,400-foot section of pipe in fair condition due to a liner installed in 1993. “We expect this middle section of the sewer main to last another 20 years,” says Portugal.
To begin the process to reline this large pipe, the contractor will first install a bypass pumping system to move wastewater through a temporary pipe, around the portion of sewer pipe being relined. DSRSD operates 24/7/365 so construction projects must maintain all conveyance facilities while upgrading worn out and failing assets such as pipes, pumps, and electrical systems.
Most of the bypass pipe will be above ground. However, when the bypass pipe crosses streets, driveways, and walkways it will be underground in a shallow trench. Sewage is moved through the bypass under pressure. This bypass pipe takes a couple weeks to set up.
Once the bypass system is in place and the corroded, cracking, and flaking pipe is emptied of sewage, the 36-inch pipe is cleaned and ready to be relined. The pipe will be relined using a cured-in-place-pipe (CIPP) method, which uses a felt liner saturated with a resin. Once the felt liner is in the pipe, hot water or hot air is forced through, pushing the liner against the walls of the pipe and hardening it to create a structural repair of the pipe. Installation and curing of the new CIPP liner will take several weeks to complete.
The last two weeks of construction involve inspecting the new liner, removing the bypass, cleaning up the construction area, and paving the trench that held the bypass pipe.
The biggest challenge of this project is that the two sections of pipe that need to be relined (813 feet total) travel through a heavily congested business area: under Interstate 580 and near shopping centers on Johnson Drive at Owens Drive that have businesses with long open hours. “The goal is to minimize impact to vehicles on the roads and pedestrians on the sidewalks,” says Portugal.
Other challenges are that some of the work will have to be done on private property requiring temporary easements, and most of the work will have to be done at night.
The District expects construction of this project to cost $600,000 and begin summer 2021, running through the end of October 2021.
The first pipe section is in an easement that begins just west of Johnson Drive (about 500 feet north of Owens Drive) and continues west almost to Owens Drive. The second pipe section is in an easement just south of I-580 between Owens Court and the Pleasanton BART parking lot.
Updated: July 14, 2021