BART reaches major milestone in upgrading its electrical infrastructure

The Bay Area Rapid Transit (BART) has completed the large-scale installation of modern and robust high-voltage cables to reliably run trains, a major milestone in infrastructure improvements.

When it’s all done, BART riders can expect a more resilient electrical power system to handle more frequent trains and support the growing number of Fleet of the Future trains.

The operation involved pulling three large cables through a conduit using a mechanical cable puller, part of an upgrade funded by the Measure RR bond that voters approved in 2016. The existing electrical system is from when BART was built in the 1960s.

The first task in a cable replacement project is to install new six-inch phenolic (a thermosetting resin) conduits. These conduits are attached to the ceiling of the tunnels using high grade structural steel plates and clamps. BART says it is using a new type of conduit that is lightweight, strong and durable. Benefits to these new types of conduit include less time to install, lower maintenance cost and longer service life.

The second task is to insert a steel braided line into the entire length of conduit, ensuring the conduit is clear of obstructions and ready for the cable pull. As soon as the steel braided line is pulled through the entire conduit, one end is attached to the electrical cables and the other end is connected to the mechanical cable puller.

Now the cable pulling operation can begin. The mechanical cable puller slowly pulls the cable into the lubricated conduit. It measures pulling tension every second to ensure no damage to the cable or conduit. It takes about one hour for the cable to travel through the entire length of the conduit.

BART’s infrastructure and system upgrades is considered essential work and can continue under the coronavirus shelter-in-place orders. Workers are equipped with face masks, safety glasses, hard hats and other PPE, and keep the greatest social distance possible on each job.

The additional time made available by BART’s 9:00 p.m. early closure, due to low ridership during the pandemic and in effect until further notice, is being used to ramp up projects like the electrical system upgrade.

Customers may be affected by the need to single-track for this project; the extra time is necessary to bring in staff and materials to be ready to go when trains stop running. This means BART will potentially be able to perform three cable pulls instead of one per shift. That equals up to 9,200 linear feet (or nearly two miles) of cable that can be installed each night. This could shave off many months of work from the five-year-long project, says BART.

DMZ Builders, a local general engineering contractor based in Concord, Calif., is the contractor for the project.