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Purple Line Extension Tunnel Boring Machines (TBM)

The TBM family is complete!

Welcome the last two tunnel boring machines (TBMs) to the Purple (D Line) Extension family. Iris and Aura, the Section 3 TBMs, have joined Elsie and Soyeon along with Harriet and Ruth, the Section 1 and Section 2 TBMs in LA.

Elsie and Soyeon, the TBMs for Section 1, are currently digging two parallel tunnels to connect three new stations between Koreatown and Beverly Hills. Meanwhile, Harriet and Ruth, the TBMs for Section 2, are currently digging the tunnels that will connect two new stations between Century City and Beverly Hills. Iris and Aura, the last TBMs to launch for Section 3, dig the tunnels to connect two new stations in Westwood finishing the tunnel connection to the Westside.

Follow the Purple Line Extension TBMs journey into the Earth on Twitter @PurpleLineTBMs .

Elsie and Soyeon, the Section 1 tunnel boring machines (TBMs), started their tunneling journey Fall 2018 at Wilshire/La Brea Station in Miracle Mile and will continue towards Wilshire/Western Station in Koreatown. Once they reach the current D Line (Purple) terminus, they will be dissembled for transporting back to Wilshire/La Brea Station and then reassembled for the last leg of their journey through Wilshire/Fairfax Station and finishing at Wilshire/La Cienega Station in Beverly Hills.

Section 1 TBM breakthrough at Wilshire/Western on June 28, 2019

Harriet and Ruth, the Section 2 TBMs started their tunneling journey in Spring 2020 from Century City/Constellation Station and head east towards Wilshire/Rodeo Station in Beverly Hills and link up with the Section 1 tunnels at Wilshire/La Cienega Station.

Section 2 TBMs in Germany

Iris and Aura, the Section 3 TBMs, will start their tunneling journey in early 2021 from the VA Hospital Campus in West LA and head east towards the Westwood/UCLA Station. The TBMs will link with the Section 2 tunnels in Century City.

Section 3 TBM being assembled within the VA staging yard

For more information about the TBMs check out the fact sheets .

Follow the Purple Line Extension TBMs @PurpleLineTBMs .

The Purple (D Line) Extension Section 1 Tunnel Boring Machines (TBMs), Elsie and Soyeon, are currently digging under Wilshire Bl. They will construct two parallel tunnels to create a seamless connection from the current Purple Line terminus at Wilshire/Western Station in Koreatown to three new stations located at Wilshire/La Brea, Wilshire/Fairfax and Wilshire/La Cienega.

Elsie and Soyeon are responsible for building 17,845 linear feet of tunnels to create approximately 3.9 miles of new subway. They have completed Reach 1 and 2 and are on their way to completing Reach 3.

Harriet and Ruth, the Section 2 TBMs, are currently building the connection between the Wilshire/La Cienega and Wilshire/Rodeo Stations in Beverly Hills and the Century City/Constellation Station. They will build approximately 2.6 miles of new subway and will be creating 13,630 linear feet of tunnels.

The last two sets of TBMs for Purple (D Line) Extension Section 3, Iris and Aura, will launch in early 2021. They will be building the tunnels between the VA Hospital Campus in West LA and Westwood/UCLA. Iris and Aura will be adding the last 2.56 miles of new subway and will be creating 13,461 linear feet of tunnels.

Along the way, all TBMs will encounter different soil conditions. The tunnel crown will always be at least 20 feet or more under the subsurface water table.

In terms of geology, tunnels will be bored through two types of geological formations: San Pedro and Fernando.

Tunneling Statistics

Progress is measured in total linear feet traveled.

Section 1 Tunneling


Linear Feet




La Brea Bl to Western Av



La Brea Bl to Fairfax Av



Fairfax Av to La Cienega Bl



La Cienega Bl to tail track west of La Cienega Bl

Section 2 Tunneling


Linear Feet




Reeves Dr to La Cienega Bl



Constellation Bl to Reeves Dr

Section 3 Tunneling


Linear Feet




VA Hospital Campus to Wilshire Bl



Wilshire Bl to Constellation Bl

Please use the materials below to learn more about the Purple Line Extension Tunnel Boring Machines (TBMs).

Fact Sheets

Follow the TBMs @PurpleLineTBMs for weekly updates on their progress and more.