DNA Lounge owner Jamie Zawinski noticed something a little strange about the Central Subway construction going down at 4th and Harrison. Our knowledge of best practices for subway-building isn't great, so we'll let him take it away:

So first they dug these narrow, deep holes and dropped girders in.

Then they dug thin trenches between them and poured walls.

Then they excavated out the dirt between those walls! What?

This city is under constant construction, so I've seen a lot of basements and foundations being dug, and I've never seen it done in that order before. They always dig a hole, shore up the sides as they dig, and then pour the walls. This seems like way more effort.

So next, they dropped girders on top of the hole, at street level, presumably to hold up the street that's going back on top -- except they only left like 4' underneath the girders, so what's going under there? Why did they do this at all! I thought the point of digging this hole was to build the head-end for the drilling machine, meaning the receiver for a bunch of conveyor belts trailing behind a chewing disc that is around 20' across.

What the fuck are they doing?

According to the Central Subway's blog, this week's project involves building beams across the below-ground walls, but that only serves to back up Zawinski's point-- we're not sure how those beams facilitate getting a 20-foot-wide drilling machine down there. Any construction aficionados want to clarify things for us?

[jwz.org]