At first glance, this photo, which was posted on Reddit by Broostenq and inspired a lengthy discussion in the comments section, looks like a picture of the Embarcadero BART station wall being painted. It’s not. The wall is getting cleaned. How did it get so dirty? We put that question to BART Communications Department Manager Alicia Trost. The short answer is train brake dust. 

Each time the train stops, the friction of the brakes creates a tiny amount of dust. With 699 cars coming and going from 4:45 a.m. until after midnight, those specks add up. The dust is so pervasive that BART recently budgeted $300,000 to remove “Legs,” a macrame sculpture installed in the late '70s. The sculpture was orange and white went it went up, and dark grey by the time it came down. 

Like “Legs,” the BART station walls haven’t been properly cleaned in a long time — not since the station opened, actually. They’re formed out of White Terrazzo, a type of flooring made from crushed marble, glass, and clay. To get them back to their original color the walls are being sandblasted by a tool that both blasts and vacuums. It sprays the wall with sand to remove the dust, and then sucks the whole mixture back up. 

BART officials chose to clean Embarcadero station because it has the dirtiest walls. It’s the first station after the Transbay Tube so it collects extra dust and grime as the trains come back from the East Bay. BART sandblasted one platform last year, and is now starting on the other side. If, like us, you see this faded wall and wonder about your lungs, don’t panic. Trost assured us there is nothing toxic in brake train dust. “It is organic material,” she said in an email. “No lead or asbestos.”  

Photo by Broostenq via Reddit

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