I can’t urge you strongly enough to talk to someone in the Planning Department. They will tell you what your options are, and there are more issues than just setbacks. Have your lot size and sq footage with you, and bring a set of plans if you have any. If not, make a rough sketch so you can describe what you’d like to do.
If you’re near any of those large power lines, you might even have a PG&E easement to deal with.
One other thing to do right away: Check the Santa Clara County Assessor’s web site and download the map for your neighborhood. That’s a good start-- it will have all the lot line dimensions on it. It’s not the easiest web site to navigate, so let me know if you have trouble doing this. It should also show if there are any easements on your lot.