Community Warning System
&
MRC internal siren tests
COMMUNITY WARNING SYSTEM (CWS)
The Community Warning System (CWS) is Contra Costa County’s official all-hazard emergency alert system, designed to notify you when a potentially life or health-threatening hazard requires you to take immediate protective action. CWS delivers alerts via multiple channels, including phone calls, text messages, email, social media, and the sounding of outdoor sirens for industrial facility emergencies.
If you hear sirens, there is an industrial facility emergency, and you should SHELTER IN PLACE immediately.
When you hear sirens, you should:
- SHELTER – Go indoors immediately.
- SHUT – Close all doors and windows.
- LISTEN – Go to local radio or TV news stations for official updates.
Stay inside until officials say it is safe.
CWS sirens are tested on the first Wednesday of every month at 11:00am. For the remaining Wednesdays, a more quiet and low “growl” test is performed at 11:00am.
CWS Levels
Hazardous materials threats are identified by severity using a 4-tier system:
- Level 0 = Offsite impacts not expected and not expected to cause public concern
- Level 1 = Odor or audible impact; flaring lasting longer than 20 minutes; or other non-flaring visual impact
- Level 2 = Has or expected to go offsite; may impact health of sensitive populations
- Level 3 = Has or expected to go off site; may impact health of general public
MRC Internal Siren tests
The refinery runs internal siren tests on Mondays between 11:00 am and 12:00 pm to ensure they are operational. During these tests, our sirens will typically be heard by our near neighbors.