Ask Mr. Smarty Plants

We found 7 Juniperus species native to California. This USDA Plant Profile shows that Juniperus californica (California juniper) grows in and around San Francisco County. As a matter of fact, the root systems of that genus are going to be pretty similar, so exact identification probably wouldn't help all that much, but we will use that as a sample.

The best advice we can give you is a kind of generic plan for killing persistent invasive roots. As long as there are no leaves growing on sprouts above ground, the roots will eventually starve to death. So, Step One, get rid of sprouts as soon as you see them surface. That is the root fighting to survive by creating new leaves (or needles in this case) to manufacture food for the root. Step Two: buy some disposable sponge paintbrushes and a wide-spectrum herbicide. Make a clean cut on the root and, within 5 minutes, paint the cut surface with full-strength herbicide. You do this so the herbicide can start getting down into the root before the root can heal itself over for protection. Be very careful doing this-don't spill the herbicide and certainly don't spray it, you will kill some things you never meant to. Make absolutely sure that the root you are treating is, indeed, from the juniper. Find as many root endings as you can and treat similarly. There is nothing you can do about the damage already done to driveway and foundation, but as the root dies, it will decompose and add some nice organic material to your soil.

More information and pictures from Calflora