Projects like that start when the money is available and plans are done, not the weather. Besides:

1) While it looks like a big El Nino, it isn't, yet. Some pieces needed aren't there yet, though most are. And the "Blob" is still off the north coast and into the Gulf of Alaska - nobody knows how that will work with an El Nino pattern elsewhere.
2) El Nino without all of the pieces mainly washes out Southern Calif.
3) Normal rainfall in SF is quite low - a bit over 20 inches. It's technically semi-arid. With adequate provision for stormwater control, projects in SF usually don't have major interruptions due to storms.

I hope that we do get a wet El Nino for the whole state, especially one where the mountain temps are cold enough that a good bit of the water falls as snow. That doesn't mean every place in the state will get flooded; SF usually doesn't, except in a few areas that have poor drainage.