This is incorrect, or misleading at best. The map that you linked contains data about TCE levels in public water systems. It does not imply anything about the contamination of the ground water supply which exists below many homes in workplaces in throughout the Bay Area.

The vast majority of the Bay Area population gets its water either from the Hetch Hetchy (SF, South Bay, Peninsula) or the Mokelumne River watershed (East Bay). Ground water wells are rather uncommon for most areas here.