What is the Community Warning System?

The Contra Costa County Community Warning System (CWS) is recognized as one of the nation’s most modern and effective all-hazard public warning systems. CWS is an all-hazards system designed to alert the community of an emergency through multiple communication tools.

How is the CWS funded?

CWS is funded through fees collected by Contra Costa County Health Services Department from hazardous materials facilities throughout Contra Costa County.

Who activates the system?

For “All Hazards” emergencies throughout Contra Costa County – The CWS system is activated by the CWS staff on behalf of law enforcement agencies, fire departments and other agencies in case of imminent threat to life or health.

The CWS system can automatically be activated by refineries, on behalf of the Contra Costa County Health Services Department in the event of a hazardous materials release.

What types of incidents is the CWS activated for?

CWS can be used for any situation in which there is an imminent threat to life safety or health. Some examples of common types of emergencies the system is activated for are: hazardous materials incidents, law enforcement activities, missing persons, gas leaks, human caused disasters, etc. The CWS may also be used to advise affected members of the public when follow-up action is required.

What types of incidents do NOT generally warrant the use of the CWS?

The CWS will NOT be activated for public communications that:

  • Do not require specific and immediate protective actions to be taken by the public.
  • Could be effectively delivered by other means.
  • Are commercial or political in nature
  • Are not authorized by a responsible public safety official.

Examples of such incidents are: major traffic delays, hazmat incidents that are contained to the facility (no off-site impact, as determined by CCHS), threats to property, general information.

Each incident is unique due to numerous variables and unforeseen developments therefore no decision making process is the same. However, there are several basic principles that must be met to consider activating the CWS system. The system will most likely be activated if: •The hazardous situation requires the public to take immediate action •The hazardous situation poses a serious threat to life or health •There is a high probability that the hazardous situation will occur
CWS utilizes a variety of tools to issue an alert. This includes: Landlines; Cell Phones (phone calls & texts) and E-mail (upon registration); Public Web Site; Social Media (Facebook &Twitter); Sirens; NOAA Weather Radios; the Emergency Alert System (EAS) and the Wireless Emergency Alerting (WEA) system. For more information on each one of these tools please see our Notification Methods section
When you receive and alert from CWS the caller ID may display as “925-655-0195”. When you receive this important call, don’t hang up. Save this number as a new contact on your mobile device and label it "Community Warning System". Once you receive the message, follow the instructions given.
The protective action you will be advised to take is incident dependent. Some common protective actions include: shelter in place, avoid the area, evacuate immediately, etc. Keep in mind that the emergency alert is designed to provide initial information and instructions regarding the incident. Please keep yourself informed by continuing to monitor other public safety warning and information systems (such as TV and radio) whenever possible. If you have any questions regarding an incident occurring in your area, you can also check this web site for any active alerts.
CWS may alert you of an imminent threat to life or health in your area as soon as requested by a public safety agency. Depending on the type of incident or emergency, the message will instruct you to take protective action such as “shelter-in-place”, “avoid the area” or “evacuate”.
No, Amber Alerts are issued by the California Highway Patrol. CWS will occasionally send alerts regarding missing persons when their life or health is at risk.
CWS may only issue an alert on behalf of the Health Services Department if the incident is deemed to have off-site impact (i.e. odor, smoke, etc.). CWS will alert the affected community about the specific hazardous situation, its location and the recommended protective action to take.
Contra Costa County Health Services, Hazardous Materials Program, established an Incident Notification Policy that includes criteria for the various public notifications requirements during hazardous materials incidents.
Some fixed hazardous materials facilities have terminals to activate the CWS on behalf of Contra Costa County Health Services Department to expedite the notification process when a release has occurred.
You can register to receive alerts for up to 3 different addresses in Contra Costa County. If the address you registered for was not impacted by a specific incident you will not receive an alert. If you registered for alerts and you are not receiving any alerts feel free to e-mail us at or call 925-655-0111.
A siren is simply an alerting device that alerts you to a possible hazard in your area. It could be for any number of hazards and is sounded to draw your attention away your daily activities. You may work or live near a hazardous materials facility, a dam or levee, or any number of potential hazards. Even if you are not sure what is going on, fortunately the best first protective action, no matter the hazard is to Shelter, Shut and Listen.
Shelter, Shut and Listen: Shelter yourself, your family, and your pets (if possible) inside, away from the outside air; Shut and lock doors and windows. Turn off vents, air conditioners and fans; and Listen to telephone notifications, radio and TV broadcasts and other sources of official information to learn how long you should stay inside and anything else you should do to protect your health.
Do not call CWS, we will call you! Do not call 911 for information about an incident, unless you are reporting a life threatening emergency. Instead, create an “emergency information kit” and prepare yourself to receive information about an incident. Have your own siren by acquiring a weather radio or register to receive voice and text alerts on your cell phone or e-mail and see a map of current alerts at
Generally, test alerts are rarely sent to the public. Test alerts are posted to the CWS public web site on a regular basis and the message will read: “This is a test of the Community Warning System. In the event of an actual emergency, check this website, TV or radio for more information. Please stay off the phone and do not call 9 1 1 unless you have an emergency to report at your location.”
You don't have to register your landline number. We already have all the landline numbers in our system. A VoIP phone or internet phone connects to your internet router therefore it is not a landline number. If you have a VoIP phone number you will need to register that number in order to receive emergency alerts.
Step 1: Go to Contacts -> Select Contact (Community Warning System) Step 2: Got to Edit -> Ringtone -> Select Emergency Bypass toggle button -> Done
Step 1: Go to Contacts -> Select Contact (Community Warning System) -> Add to Favorites Step 2: Go to Settings -> Notification –> Do Not Disturb -> Allow Exceptions -> Calls From -> Favorite Contacts Only