The cleanest beaches are picked from a list of the 200 most popular U.S. beaches, and NRDC awarded one star each for:
1) Meeting water quality standards in 2009.
2) Meeting water quality standards in 2008.
3) Testing frequency (more than once a week).
4) Promptly issuing a closing or advisory warning when a water sample exceeded state standards.
5) Promptly posting closing or advisory signs (online and at the beach) when necessary.
The following Southern California beaches received four or five stars.