Fortunately (with rare exceptions) nobody uses well water in Santa Clara county (see https://pubs.usgs.gov/circ/circ1182/pdf/05SantaClaraValley.pdf https://pubs

Fortunately (with rare exceptions) nobody uses well water in Santa Clara county (see https://pubs.usgs.gov/circ/circ1182/pdf/05SantaClaraValley.pdf https://pubs.usgs.gov/circ/circ1182/pdf/05SantaClaraValley.p... ) and a lot of these chemicals are relatively low toxicity, the greatest danger seems to be vapors released from the soil. As far as risks via things like gardening, I actually wonder about the levels of arsenic or mercury in the soil, compounds of which were used many decades ago on fruit trees (which were very common here).