Lake Anza North - Tilden Regional Park

Source Information

The East Bay Regional Park District’s recreational water quality is monitored as a collaborative effort between East Bay Parks, Contra Costa and Alameda County Departments of Environmental Health. Sites are monitored weekly from April - October and many continue to be monitored twice a month from November - March. East Bay's fresh water beaches are tested solely for E.coli. The standards for indicator bacteria are as follows: Single sample maximum E.coli > 235 MPN / 100 ml Geometric Mean (5 samples collected over a 30 day period) E.coli > 126 MPN / 100 ml A fresh water beach is marked Green when bacteria levels for a single day and geometric mean are below the standards mentioned. A fresh water beach is marked Red when bacteria levels for a single day or the geometric mean are above the standards mentioned. In Swim Guide, a red icons will be assigned to beaches posted with a cautionary advisory as well as emergency closures. East Bay monitoring agencies do not close beaches unless there is a sanitary sewer overflow or other emergency. Beach are posted with a yellow icon on East Bay’s website when bacteria levels are above the standards mentioned. A beach is marked Grey when there is no current or reliable monitoring information available. When visiting a beach, EB Parks encourages you to protect your health. Keep water out of your mouth. After you leave the water, shower and towel dry as soon as possible. Do not swim in the lake for 3 days after a rainstorm or swim within 100 feet of a flowing storm drain. Check posted signs for water quality information.