Point. Although I'd assume the majority of subway routes tend to be built under roads (also bad, but less terrible)? Not sure what the geology of San Francisco

Point. Although I'd assume the majority of subway routes tend to be built under roads (also bad, but less terrible)? Not sure what the geology of San Francisco / California tends to be like, but I believe most of the Manhattan skyscrapers are anchored down to the bedrock. Which I'd expect would require cutting and reinforcing vs just "drill on through".