Nitrate contamination comes from agricultural run-off. Nitrogen fertilizers are heavily applied to fields to produce ripe, market-ready crops year round.
Arsenic is mostly naturally-occuring around Monterey County, specifically known to be located along Highway 68. It can also leach as a by-product of mining and other industrial activities.
Coliform bacteria - including total coliform, fecal coliform and E. coli bacteria - can be caused by improperly treated or maintained sewage systems or well equipment.
Corinne Smith is a freelance multimedia journalist based in Monterey and Oakland, CA. In May 2015 she graduated from the Middlebury Institute of International Studies at Monterey, with a master's degree in International Policy and Development with a focus on land and water rights, conflict resolution, and sustainable development. She is currently working on a long-form radio piece on how communities are protecting water quality in the Salinas Valley, how agricultural run-off is regulated, and solutions for the future of sustainable agriculture. Contact at firstname.lastname@example.org