Finally got a chance to check out the cement factory ruins at American Canyon. They are rapidly building houses all around it, so I'm afraid the place won't be available to explore for much longer. (The city claims the ruins will be preserved, with a town center actually built right there, but the place certainly won't be in its current state.)
Went on a weekday and there were too many construction workers nearby, so I only got to fly a drone around. But I'm hoping to go boots on ground this Sunday--it's New Year's so hopefully nobody will be working. If anyone else is interested in joining, message me! Would love some company.