How the Purple Line is making history

Yesterday, we celebrated the end of tunneling on the Purple (D Line) Extension Project –– a major step forward in our plans to build a subway that will connect Downtown Los Angeles with some of the most significant areas of the Westside. This important phase of the project was officially completed last October, when two eastward-chugging Tunnel Boring Machines (TBMs) coming from Westwood entered the future Century City / Constellation station. Yesterday, a small event was held at the Wilshire / Fairfax station construction site (Ogden Yard) to celebrate the tremendous efforts of our engineering, planning, and hard-working construction crews.  

Mayor Bass gives rousing remarks at yesterday’s event.

Picking up where the Purple Line currently ends at Wilshire / Western station in Koreatown, the project will add seven new stations in some of LA’s most popular (and crowded) destinations such as the Miracle Mile, Beverly Hills, Century City, and Westwood. When the project is complete, Angelenos will be able to travel between downtown Los Angeles to Westwood in only 25 minutes.  

It’s going to be big. Not only because the new subway will connect millions of people to jobs, schools, museums, medical centers, and various forms of recreation. And not only because it will serve some of LA’s most notoriously congested areas. (Let’s face it, traveling to and from the Westside at rush hour is the bane of our existence, the cause of thousands of lost jobs and failed relationships. For Angelenos, it’s almost a punchline.)   

Even more than those things, completing this project will be a historic achievement. Why? Let me explain.  

Even though we officially broke ground on the Purple (D Line) Line Extension Project in 2014, this date doesn’t speak to the much longer legacy of rail-building ambition along the Wilshire Corridor –– and the complex emotions about it we’ve been kicking around for a very long time. Wilshire Boulevard, in many ways, is perfect for rail-based rapid transit. The almost 16-mile street is home to some of our most iconic businesses, cultural institutions, and architecturally significant buildings. (That’s part of the reason why it’s the busiest thoroughfare in the region!) It’s central –– running through five major business districts. And it’s dense –– so the rail line would get a lot of use (we’ve projected that over 49,000 people will board trains at the new stations every weekday). Yet Wilshire’s relationship with mass transit has been fraught, to say the least:  

  • In 1901, Wilshire Boulevard famously banned streetcars between MacArthur Park and Beverly Hills in a city ordinance. The noisy streetcar lines, homeowners believed, risked bringing undesirable elements into the neighborhood. (This was one of the reasons why Wilshire became the location of one of LA’s first bus routes.)

Cruising down Wilshire Boulevard, c. 1932

  • In 1963, German transportation company Alweg Monorail proposed building a monorail that would travel over the famous boulevard. It didn’t go very far. Although it succeeded in Disneyland, LA stakeholders promptly squelched it.  

Vice-President Richard Nixon and family, seen here with Walt Disney, prepare to ride Disneyland Monorail (also built by Alweg), June 1959.

  • In 1968, Wilshire Boulevard was proposed as one of the routes proposed in SCRTD’s ‘Five Corridor System,’ which was rejected by voters. (Read a great first-person account here.)  

  • Wilshire Boulevard was the original alignment for the Red Line (now the B Line), LA’s first modern subway. The train was originally supposed to travel beneath Wilshire from Alvarado Street to Fairfax Avenue. (At Fairfax, the train would have then turned north and continued through West Hollywood and into the San Fernando Valley.) That is, until the infamous Ross Dress For Less methane explosion of 1985. While the explosion didn’t mean that a subway would have been dangerous, it stoked fears about subterranean methane and it provided politicians ammunition to ban the use of federal money for the subway’s western extension for the next 22 years. The Red Line was rerouted up Vermont Avenue instead.


Tunneling technology has evolved a lot since the 1980s. It’s gotten faster, safer, and more sustainable. That starts with our Tunnel Boring Machines, or TBMs –– the 400-foot-long, 1000-ton megadrills we use to dig beneath the ground. At the front of them are enormous cutter heads (i.e. giant spinning disks complete with blades) that measure over 20 feet in diameter. We use them to cut away soil while they form the tunnels with concrete. TBMs came on the scene during the 1950s –– before then, the work was done by miners! –– and they’ve evolved a lot in recent years. For example, we used open face shields with diggers to build the Red Line during the 1980s and 1990s. These shields dug directly against LA’s relatively soft soil and rock formations.   

Now, we have what we call “earth pressure balance” TBMs –– named because they maintain a constant pressure in the ground surrounding the tunnel with a mixture of air and soil conditioners, keeping workers safe and making collapses virtually impossible. As the TBMs move forward, concrete liners are immediately installed in order to support the newly excavated portions of the tunnel. 

Still, the project hasn’t been easy. Far from it. Spanning nine miles, the Purple Line Extension Project is the longest tunneling project through tar in Southern California. The project was so large (and funding arrived at different times) that we split the task into three sections, each of which connected us to different pieces of our region’s history. Curious? Here’s a recap.  

Section 1:  

3 stations 

3.92 miles 

Projected opening: 2025  

Tunneling for the PLE kicked off in October 2018, when our Section 1 TBMs –– named “Elsie” and “Soyeon” –– started digging eastwards from the Wilshire / La Brea station site toward the existing D Line station at Wilshire / Western, clearing soil and rock 70 feet below the city. They reached Western Avenue in June, 2019.   

This -– we called it Reach 1 –– was the (relatively) easy part. In Fall 2019, the TBMs were removed from the ground, transported back to the La Brea Avenue site, and launched westward (the reason for this change in direction was that launching a TBM at the Wilshire/Western site would have required a large, time-consuming, and costly additional excavation). The second section –– Reach 2 –– was a much tougher dig. The TMBs encountered pockets of methane gas and sticky tar sands (no surprise there, as we were working right next to the La Brea Tar Pits). On a good day, a TBM can tunnel up to 60 feet, in these conditions, they’d often only log half the distance … or less. And even though TBMs run on electricity, they still need to be cleaned, lubricated, and serviced in order to operate as safely as possible. Especially when covered in tar.  

Getting ready to tunnel at the future Wilshire/La Brea station. Yes, cutterheads come in all kinds of colors!

Did we mention that we found a lot of fossils at all three Section 1 station excavations? Wooly mammoths, mastodons, camel, bison, dire wolves, giant sloths, you name it. After cataloguing and cleaning is complete, the fossils will eventually be housed at the Natural History Museum of Los Angeles County. And we never would have found them without the subway project. Geologists describe Los Angeles as a “bowl” or “basin” filled with epochal amounts of organic matter. We found over 2000 fossils when we tunneled the Red Line too.  

We also ran into things we call ‘anomalies’ –– which are pretty much what they sound like –– unidentified objects beneath the ground. In 2020, we found two giant steel beams at the intersection of Wilshire and San Vicente Boulevards. The objects were eventually removed, but we still don’t know when they were made, or where, exactly, they came from. You don’t want a TBM to hit metal (we learned this from a TBM named ‘Big Bertha’ in Seattle), and removing the beams ended up causing some project delays. 

In April 2021, Elsie finally broke through to the Wilshire / La Cienega subway station site in Beverly Hills. Soyeon followed in May. We had broken a record –– the longest tunnel project through tar infested soil in history! 

Section 2 

2 stations 

2.59 miles 

Projected opening: 2027  

Subway tunneling below this stretch of Wilshire between La Cienega Avenue and Century City also officially broke ground in 2018, although the TBMs –– “Harriet” and “Ruth” –– didn’t start digging until April, 2020 – that’s right, during some of the most uncertain moments of the pandemic. They started at the staging yard at the future station at Century City/Constellation and then headed east. Harriet reached the Wilshire/Rodeo station box in early January, 2021. Ruth followed a few weeks later.  

If Section 1 submerged us into the prehistoric era, Section 2 brought us up to the early 20th century. While this area wasn’t nearly as tar-heavy or fossil-rich as Section 1, we did unearth some fragments of the region’s recent past.  

We started at Century City, once a 20th Century Fox backlot before it was purchased by developer Robert Zeckendorff and aluminum giant Alcoa and transformed into a mixed-use, state-of-the-art “city in a city” during the 1960s. We had high hopes going into the dig. Would we find pieces of the studio’s beloved Cafe de Paris? Would we find remnants of the sets where Cleopatra was filmed? Unfortunately, no archeological resources were found. All we turned up were miscellaneous debris –– bricks, rusty pipes, pieces of lumber, and fragments of metal –– placed when the old backlot was leveled in the 1960s to make way for Century City.  

Under Beverly Hills High School we found two abandoned oil wells: reminders of our not-so-distant past as an oil town that played a huge role in the region’s expansion. The four-miles-long Beverly Hills Oil Field was discovered in 1900 … and is still active today. For decades, there was a drilling island on the high school’s campus (that was capped and plugged in 2020). 

In the past, old wells were abandoned by dumping bricks in the hole – bricks that would be 100 years old by this point! Today, the state of California has far more rigorous standards for safely plugging the wells (think thin-walled steel casing that is drilled into the ground, allowing specialists to fill the hole from the bottom with high-pressure grout). Luckily, the City of Beverly Hills was already working to plug other wells on campus, so we were able to use the contractors who were already there. All the necessary work on these two wells was was complete before our TBMs reached them.  

Plugging a well in September, 2020 … when no one was in school.

By January 2022, the TBMs pulled into the excavation for the future station at Wilshire/Rodeo (still a 90+ foot hole in the ground at that point). They were then walked to the eastern side of the future station along plinths in order to continue their work. Harriet reached the future station at Wilshire/La Cienega in November, 2022, followed by Ruth in January, 2023.  

Section 3 

2 stations 

2.56 miles  

Projected opening: 2028 

Section 3, the project’s shortest section, broke ground in 2021, and TBMs named “Aura” and “Iris” were launched into the ground at the future Westwood/VA Hospital station on the west side of the VA campus in October 2020 and started tunneling east.  

Well … almost. There wasn’t a future station yet. In Section 3, we approached the tunneling process a little bit differently. When we started on Sections 1 and 2, our contractors dug out the stations first. Once they completed the piling (that is, inserting steel beams around the future station box’s circumference to form a station “skeleton”), the TBMs were lowered into the shafts, switched on, and started doing their thing.  

For Section 3, however, we used two contractors at once –– a first for Metro. One team of contractors operated the TBMs while another team created the station boxes. In Section 3, therefore, our station “breakthroughs” were vertical. In other words, rather than TBMs tunneling into the future stations from the side, we connected the tunnels to the future station box by digging downwards and meeting the existing tunnels by bursting through precast segments.  

Section 3 wasn’t fossil rich like Section 1, or oil rich like Section 2. We found a lot of … bricks. Why? When the National Home for Disabled Volunteer Soldiers and Sailors opened in 1888, designed for Civil War veterans, a number of structures were built on the 400-acre property. Over decades, many of them were demolished and rebuilt, but remnants of old buildings are still there –– such as brick chimneys, furnaces, and sometimes entire foundations.  

By April 2023, our Section 3 TBMs approached the doorstep of the Century City/Constellation station. We were almost at the finish line.  

Future Westwood/VA Hospital Station


What happens now that tunneling is complete?  Crews will start the concrete work in the tunnels to support the tracks. They’ll also create cross passages on twin tunnels to use in case of emergencies. Then we’ve got to build the stations, including the appendages where electrical equipment and other utilities are housed as well as installing power and ventilation systems.  There is still a lot of work to do.  

But completing the tunneling is a huge milestone –– without a doubt, one of the most difficult aspects of a subway project. And when you take the Wilshire Corridor’s history into account, the feat is pretty darn special. While we encountered unexpected challenges, we successfully tunneled almost 10 miles. We went beneath homes, stores, offices, and even a high school, without receiving one single complaint about noise or vibrations from our TBMs. We always knew this would be an undertaking. We’re proud of what we’ve achieved.  

And yet, the cultural implications of this feat are bigger than any one street or thoroughfare. Los Angeles is a peculiar place. Much of our history is buried beneath the ground. Tar that seeps through the grass in Hancock Park brings to mind the animals of the prehistoric era. Active rigs remind us of our not-so-distant past as a booming oil town (and, for what it’s worth, Los Angeles is still the greatest urban oil field in the country). Here, the subterranean world has an outsized influence on our collective psychology. Legends of underground labyrinths and lizard people percolated through early 20th-century print culture. Reports of seismic activity and earthquake liquefaction keep us wondering when the Big One is coming. Our subway tunnels are places where the past feels very close, and where the future is still being written.  



Categories: Transportation News

8 replies

  1. Long overdue extension. I wished they added a Crenshaw stop though. That is a somewhat long way between La Brea and Western to not have a Crenshaw stop… which will be needed soon once K Line heads further north.

  2. Thanks Ms. Mandelkern for this instructive and well-resourced report. Large mass-transit projects take a long time to plan and execute, sometimes longer than social and economic changes in a region impact how, and why, we need to get around. When the 1968 plan was proposed, part of the justification was to get commuters to work in downtown Los Angeles in a timely fashion when boosters dreamed of Los Angeles having a “real” downtown like major cities back east.

    But since the pandemic, two changes have occurred. A boom in jobs in the entertainment industry (driven by streaming) and tech fields has led to increased housing prices on the west side, and many people who used to commute to downtown now work from home.

    As a result, downtown Los Angeles, recently on the verge of becoming the very “real” downtown boosters in the 1960s dreamed of, is suffering,

    But Los Angeles’s long term commitment to ferry commuters on a rail line west to east might now work even better in reverse. The new D line could bring workers from employment centers on the west side home to downtown, where high-density residential development is welcomed, and points east, where more affordable housing is accessible on other rail lines and Metrolink commuter rail.

    The problems we are solving with the transit plan today are different than those we faced in the 1960s, but the subway can still be the solution.

  3. This was a really thoughtful and well written piece; I appreciate it!

    The tunneling to the west side is a really significant achievement and the fulfillment of more of a century of waiting to connect the two sides of town via off-grade transit. I look forward to metro continuing its work on making transit clean, safe, fast, and frequent so we can get more Angelenos out of their cars, lower VMT, and make LA a more accessible, equitable, and affordable place.

    This will also go a long way towards shaking off the pernicious myth that LA is a “car town” when—in fact—LA was built and grew as a *rail town* where folks moved regionally in the great-great-grandparents of our current LRT and HRT rolling stock! What a stupendous achievement this is.

    Now let’s get those TBM’s to keep going to Santa Monica then turn south along the coast until they hit San Pedro!!

  4. Why did Metro’s CEO fire the agency’s chief safety officer? Is this blog going to acknowledge this news that affects Metro riders who are subject to daily harassment and crime riding Metro trains and buses?

  5. The tunnels were completed last year. Are we now delaying celebrations a year too? It seems like everything has to be a year or two late on every project.

    • Tell that to everyone in LA that insist that this line goes down to LAX even though it’s going to take just as long as the LAX Flyaway is now.

      Yes, I rather send this to Santa Monica and the Sepulveda Line to LAX instead. No need to further complicate the system.