Regional Connector’s next challenge: a massive storm drain lurking under DTLA

There’s plenty of buzz surrounding the Regional Connector tunnel boring machine and its 1.1-mile trip under downtown Los Angeles, including this in-depth look by the L.A. Times. Right next to the Times building, however, crews are working to upgrade a massive, decades-old storm drain running under 2nd Street between Spring Street and Broadway.

Recent photos from the construction site show the scale of this concrete pipe that’s encased in wood and running through the site of the future Historic Broadway Station. Crews have chipped away at rock and clay and exposed most of the old storm drain that’s nearly 12 feet wide. In order to advance excavation down to the tunnel level, the pipe must be replaced.

This is a good example of how complex transit projects can be. They’re not always just about building transit — rather they can also be about moving and rebuilding other civic infrastructure. 

The new fiberglass reinforced, polymer mortar pipe will measure just over 10 feet in diameter. Compared to concrete, it’s much lighter and easier for workers to handle. Once fully installed, the new pipe will be suspended from the 2nd Street decking so that excavation operations can continue while maintaining flow to the storm drain system.

The materials and supplies for the new pipe are being delivered to the site this week and crews are expected to begin installing the new bit of infrastructure in June.

The Regional Connector is a 1.9-mile rail tunnel in downtown L.A. that will link the Blue, Expo and Gold Lines, creating quicker trips to and through DTLA with fewer transfers. The project is funded in part by Measure R, the half-cent sales tax approved by L.A. County voters in 2008 as well as a grant from the Federal Transit Administration. Project homepage

7 replies

  1. i realize that somebody has calculated the weight of that pipe filled with water and the weight of the roadway above it.. and figured out if the surrounding walls and the I beams can carry the weight .. might want to NOT have any crew down there during rain when the storm drain gets more than 25% full.. until its tested a few times. this is just a thought.. i would worry about the water pushing against the existing structure with no dirt around it to support it..

  2. Reminds me of the oldest subway in continental Europe, the Budapest M-1 line. It was built in 1895-96 and has a low-clearance tunnel and trains of a unique low-platform design because the depth to which the tunnel could be dug was limited by a large sewer line in the downtown area.

  3. A definite but often ignored side benefit of these projects is identifying where utilities are and in this case replacing before failure.

  4. A little more description would be nice. How deep is this older storm drain? Presumably the RC TBM is running much deeper.

    • The storm drain is approx. 25 feet below the ground level. The tunnel in that station will run between 110-120 feet below the ground level.