Cr : http://www.acphd.org/2019-ncov/face-covering.aspx

Effective July 19, 2020 and valid until replaced, amended, or rescinded: Health Officer Order with updated Face Covering guidelines for Alameda County.
Summary of the Face Covering Order
This order generally requires wearing Face Coverings when people are outside their homes, and is intended to provide simple rules that we must all follow in the months to come. Widespread use of Face Coverings is a critical part of reducing the spread of COVID-19.
Per the Order, everyone over the age of 12 should wear a Face Covering when:
at an outdoor dining establishment except when eating or drinking at a dining table;
outside their home and within 30 feet of anyone else other than members of their Social Bubble;
in the workplace except when in a private space or area not regularly used by others;or
preparing food or other items for sale or distribution to people outside their household.
Face Coverings may be removed in the following circumstances but should always be kept on hand:
when eating or drinking alone or with members of one’s Social Bubble; or
when alone or with members of one’s household in an outdoor area such as a park or patio, while maintaining six feet of distance from others.