For the last two weeks, the city of Sacramento has been working on the downtown sewer systems. The short version of why goes something like this: the sewage was draining into the Sacramento river. It's probably defiled forever, but in the meantime it's time to fix shit.
As such, all over the downtown area it sounds a bit like a Freddy Krueger film. This is made more amusing - if amusing is the right word - by the earth-quake style booms that you can periodically feel as they tear up the road.
Ah, well. Don't take this for complaining. It's totally fucked up my sleep cycle, but beyond that it's rather amusing to wake up to nigh-endless metal screeches, booms, and small explosion sounds.