Los Angeles is finally going underground

Los Angeles is set to open a transformative 4-mile subway extension along the critical Wilshire Boulevard corridor in May, connecting downtown to the Pacific Ocean. The new segment, featuring three stations, will turn what is often an hours-long drive through the museum-dense Miracle Mile district into a swift 25-minute train ride. This achievement represents a major engineering victory, as the ground beneath the area is notoriously unstable, filled with tarry soil and methane deposits—a hazard demonstrated by a 1985 explosion that destroyed a department store.

To conquer this dangerous geology, LA Metro employed specialized earth-pressure-balance tunnel-boring machines. These automated diggers are designed to safely chew through gas-packed ground, removing dirt via conveyor belts and simultaneously installing precast concrete liner segments with sealed gaskets to form a gas- and waterproof tube. This technology allowed for rapid progress of about 50 feet per day. Station construction was managed from street level, with weekend excavations covered by concrete decks to allow uninterrupted car traffic above. While the project ran over budget and schedule, costing nearly $4 billion for this segment alone, it marks a significant step in LA's decades-long effort to rebuild its rail network and reduce car dependency.